TE ANAU TREATED WASTEWATER SCHEME BASIS OF DESIGN · Rima Krause Roger Oakley PREPARED BY 27 August...

REPORT

TE ANAU TREATED WASTEWATER SCHEME BASIS OF DESIGN STATUS: UPDATED AFTER FINAL COMMENTS FOR REVIEWER

CENTRE PIVOT IRRIGATION OPTION ADDED

PREPARED FOR SOUTHLAND DISTRICT COUNCIL September 2018

Stantec │ │ September 2018

Status: Final │ Project No.: 80508264 │ Our ref: r_SDI BoDesign v13c for BC

Stantec │ │ September 2018

Status: Final │ Project No.: 80508264 │ Our ref: r_SDI BoDesign v13c for BC

This document has been prepared for the benefit of Southland District Council. No liability is accepted by this company or any employee or sub-consultant of this company with respect to its use by any other person.

This disclaimer shall apply notwithstanding that the report may be made available to Southland District Council and other persons for an application for permission or approval to fulfil a legal requirement.

QUALITY STATEMENT PROJECT MANAGER PROJECT TECHNICAL LEAD

Rima Krause Roger Oakley

PREPARED BY

27 August 2018 Roger Oakley

28 August 2018

CHECKED BY

John McAndrew (except section 8).

Rima Krause (section 8)

28 August 2018

REVIEWED BY

John Cocks

28 August 2018

APPROVED FOR ISSUE BY

Rima Krause

REVISION SCHEDULE

Rev No. Date Description

Signature or Typed Name (documentation on file)

Prepared by Checked by Reviewed

by Approved

by

28 Aug 2018 Final for Business Case R Oakley J McAndrew,

R Krause J Cocks R Krause

25 Sept 2018

Update with final Ecogent and reviewer comment R Oakley J McAndrew,

R Krause J Cocks R Krause

File path: P:\_2012 Onwards\Southland District Council\80508264 Te Anau WWTP\G - Specification & Reports\G12 - Basis of Design\r_SDI BoDesign v13c for BC.docx

DUNEDIN Level 3 John Wickliffe House, 265 Princes Street, Dunedin 9016 PO Box 13-052, Armagh, Christchurch 8141 TEL +64 3 477 0885, FAX +64 3 477 0616

Stantec │ │ August 2018

Status: Final │ Project No.: 80508264 │ Our ref: r_SDI BoDesign v13

Southland District Council Te Anau Treated Wastewater Scheme

CONTENTS 1. Introduction and Purpose ........................................................................................................................... 1

1.1 Update to Include CPI – August 2108 ........................................................................................................ 1

1.2 Project Background ..................................................................................................................................... 1

1.3 Purpose of this Report .................................................................................................................................. 1

1.4 Process Flow Schematic .............................................................................................................................. 1

1.5 Cost Estimates ............................................................................................................................................... 1

2. Outcomes of Reviews of this Report .......................................................................................................... 2

2.1 Ensuring Fair Comparison SDI v CPI ............................................................................................................ 2

2.2 Transfer Pipeline Size .................................................................................................................................... 3

2.3 Updated SDI layout (Option 3) ................................................................................................................... 3

2.4 Biofilm Dosing for main Transfer Pipeline.................................................................................................... 4

2.5 Site Drainage Control .................................................................................................................................. 4

2.6 Additional Hydrus Modelling ....................................................................................................................... 4

2.7 Further Modelling for Irrigation During Extreme Weather ........................................................................ 4

3. Resource Consents ...................................................................................................................................... 5

3.1 Kepler Discharge Consent .......................................................................................................................... 5

3.2 Discharge Consent to Upukerora River ..................................................................................................... 7

3.3 Discharge to Air at Existing Ponds Site ....................................................................................................... 7

4. Design Flows ................................................................................................................................................. 8

4.1 MWH NTC29 – First Stage SDI ....................................................................................................................... 8

4.2 Recent Flows ................................................................................................................................................. 8

5. Design Loads ................................................................................................................................................ 8

6. Project Constraints ....................................................................................................................................... 9

6.1 Business Case ................................................................................................................................................ 9

6.2 Resource Consents ....................................................................................................................................... 9

6.3 Technical ....................................................................................................................................................... 9

7. Specific Process Elements – General and SDI ........................................................................................ 12

7.1 Existing Ponds .............................................................................................................................................. 12

7.2 Additional Storage ..................................................................................................................................... 13

7.3 Pond Outlet Screen .................................................................................................................................... 15

7.4 Membrane Inlet Screen ............................................................................................................................. 16

7.5 Membrane Filtration ................................................................................................................................... 17

7.6 MF Balance Tank ........................................................................................................................................ 19



7.7 Biofilm Control Dosing ................................................................................................................................ 21

7.8 Pump Station ............................................................................................................................................... 22

7.9 Transfer Pipeline .......................................................................................................................................... 23

7.10 Air Valves and Odour Filters ...................................................................................................................... 24

7.11 Pump-out Drain Points ............................................................................................................................... 25

7.12 Control Valve .............................................................................................................................................. 26

7.13 Kepler Balance Tank .................................................................................................................................. 27

7.14 Kepler Balance Tank Odour Filter ............................................................................................................. 29

7.15 SDI Pump Station ........................................................................................................................................ 30

7.16 SDI Irrigation Filtration and Flush Filtration ................................................................................................ 31

7.17 SDI Biofilm Dosing ........................................................................................................................................ 33

7.18 Subsurface Drip Irrigation .......................................................................................................................... 34

7.19 Root Intrusion Control ................................................................................................................................. 40

7.20 Subsurface Drip Irrigation Flushing ............................................................................................................ 41

8. Specific Process Elements – CPI ............................................................................................................... 42

8.1 Trickling Filter Pumpwells and Balance Tank ........................................................................................... 42

8.2 Trickling Filter ............................................................................................................................................... 44

8.3 Soil Odour Filter ........................................................................................................................................... 45

8.4 Hypochlorite Dosing ................................................................................................................................... 46

8.5 Centre Pivot Irrigators ................................................................................................................................ 47

9. Other Process Elements ............................................................................................................................. 50

10. Risk ............................................................................................................................................................... 51

10.1 Key Risks Summary for SDI .......................................................................................................................... 51

10.2 Opportunities Arising From SDI .................................................................................................................. 53

10.3 Opportunities for Both CPI and SDI .......................................................................................................... 54

LIST OF TABLES Table 2-1: Comparison of SDI and CPI features...................................................................................................... 2

Table 4-1: Average Pond Inflows for Mid-Summer and Winter ............................................................................. 8

Table 6-1: Minimum Life of Major Components .................................................................................................... 10

Table 7-1: Summary Process Element – Existing Ponds ......................................................................................... 12

Table 7-2: Summary Process Element – Additional Storage ................................................................................ 13

Table 7-3: Summary Process Element – Pond Outlet Screen ............................................................................... 15

Table 7-4: Summary Process Element – Membrane Inlet Screen ........................................................................ 16

Table 7-5: Summary Process Element – Membrane Filtration .............................................................................. 17

Table 7-6: Summary Process Element – MF Balance Tank ................................................................................... 19

Table 7-7: MF Balance Tank initial sizing (tbc) ...................................................................................................... 20

Table 7-8: Summary Process Element – Biofilm Control Dosing ........................................................................... 21

Table 7-9: Summary Process Element – Pump Station .......................................................................................... 22

Table 7-10: Summary Process Element – Transfer Pipeline ................................................................................... 23



Table 7-11: Summary Process Element – Air valves and Odour Filters................................................................ 24

Table 7-12: Summary Process Element – Pump-out drain points ........................................................................ 25

Table 7-13: Summary Process Element – Control Valve ....................................................................................... 26

Table 7-14: Summary Process Element – Kepler Balance Tank ........................................................................... 27

Table 7-15: Kepler Balance Tank initial sizing (tbc) .............................................................................................. 28

Table 7-16: Summary Process Element – Kepler Balance Tank Odour Filter ...................................................... 29

Table 7-17: Summary Process Element – SDI pump station ................................................................................. 30

Table 7-18: Summary Process Element – SDI Irrigation Filtration and Flush Filtration ......................................... 31

Table 7-19: Summary Process Element – SDI Biofilm Dosing ................................................................................ 33

Table 7-20: Summary Process Element – SDI ......................................................................................................... 34

Table 7-21: Summary Process Element – Root Intrusion Control ......................................................................... 40

Table 7-22: Summary Process Element – SDI Flushing ........................................................................................... 41

Table 8-1: Summary Process Element – TF Pumpwells and Balance Tank ......................................................... 42

Table 8-2: Summary Process Element – Trickling Filter .......................................................................................... 44

Table 8-3: Summary Process Element – Soil Odour Filter ...................................................................................... 45

Table 8-4: Summary Process Element – Hypochlorite Dosing .............................................................................. 46

Table 8-5: Summary Process Element – Centre Pivot Irrigators ........................................................................... 47

LIST OF FIGURES Figure 7-1: Motueka WWTP membrane inlet screen ............................................................................................ 16

APPENDICES Appendix A Draft Process Flow Diagram

Appendix B Chart of Pond Inflows

Appendix C NTC 29 – First Stage SDI Flows

Appendix D NTC 32 Design Nitrogen Loads

Appendix E Consented Irrigation Area

Appendix F SDI Field Layout Options

Appendix G Review Feedback – P Riddell

Appendix H Peer Review Feedback - Ben Stratford

Appendix I Cost Estimates

Appendix J Comparison of SDI and CPI Schemes

August 2018 │ Status: Final │ Project No.: 80508264 │ Our ref: r_SDI BoDesign v13

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1. Introduction and Purpose Southland District Council (SDC) are seeking to implement a wastewater scheme to dispose to land the wastewater discharge from the Te Anau wastewater ponds. This Basis of Design report describes the processes, design requirements, and risks associated with the option for this land disposal to be by subsurface drip irrigation (SDI).

1.1 Update to Include CPI – August 2108 In August 2018, this report was updated, for completeness, to include all the elements of the currently consented Centre Pivot Irrigation (CPI) option. Previously, only CPI elements that were in common with SDI were included. Section 8 has been added to describe process elements unique to CPI.

1.2 Project Background Presently, the discharge from the Te Anau ponds is via a wetland to the adjacent Upukerora River. The consent for this discharge expires on 30 November 2020. Commencing 2005, SDC have been seeking to identify and consent a suitable land disposal site, so that the Upukerora discharge could cease. A 25yr consent was granted in January 2017 for disposal via centre pivot irrigation (CPI) to a block of land north of the Manapouri/Te Anau airport. This is a 125Ha site known as the Kepler Block, of which approx. 115Ha is permitted in the consent to be irrigated. After submissions from stakeholders, SDC agreed to explore the option of changing the irrigation method from CPI to SDI.

1.3 Purpose of this Report The purpose of this report is to identify the requirements for an SDI scheme. This includes first identifying overall project requirements. Following from this the individual process elements and their design requirements are identified. The level of investigation required for this report is to a level that an SDI option can be scoped sufficiently for a fair comparison to be made with CPI, and with sufficient confidence that, if the SDI option is adopted, its scope is generally in accordance with this report. This report also identifies the key risks for each process element, and of the process overall. This report has been subjected to feedback and submissions, and a peer review, and updated as required. Feedback, with responses, from the principal reviewers is appended. Once finalised, it will form the evidence base for the Business Case comparison with the CPI option.

1.4 Process Flow Schematic A schematic of the process elements is appended, which illustrates each process element.

1.5 Cost Estimates This Report does not provide cost estimates. These will be developed once the Basis of Design is confirmed.


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2. Outcomes of Reviews of this Report This report was submitted in draft format on 24 April 2018 for:

Formal peer review by Ben Stratford of Mainline Aqua Technical comment by Peter Riddell of Ecogent Ltd.

Following initial feedback from the above, an updated report was reissued as ‘Updated for Final Comment by Reviewers’. The final version of this report has been updated to take account of this feedback. The key issues arising from the review are discussed below.

2.1 Ensuring Fair Comparison SDI v CPI It is important that as far as possible an ‘apples for apples’ comparison can be made by Business Case assessment when comparing SDI and CPI schemes. Some technical and risk matters are not entirely comparable and have been dealt with in the following way:

Table 2-1: Comparison of SDI and CPI features

Item Method of Comparison

SDI able to irrigate in a wider range of weather conditions. An advantage of SDI is that it is not affected by wind, and is less affected by surface runoff. (Refer risk in s8.2). This reduces the peak demand on the 15,000m3 additional storage at the Te Anau ponds site. There are options for how to best account for this: Reduce the 15,000m3 storage with SDI. Not

considered feasible as this is a consent condition.

Reduce the size of Transfer Pipeline, on the basis that peak flows can be mitigated. Not pursued, see below.

Add scope to the CPI estimate (for comparison purposes at least), to provide a similar level of risk mitigation. This method selected.

Budget allowance added to CPI estimate for: Management of surface runoff on the site. A further 8,000m3 of Additional Storage at the

Te Anau ponds, compared to SDI. (Note, an earlier proposal was to remove the

Southern Shelter belt at Kepler to allow greater use of the western side of the site. This budget now added to the additional storage budget, as this is more suitable mitigation).

Note, the addition of these budget estimates is for the purposes of comparison of options, and is not a formal commitment that this scope will be added to the project. Also note the existing CPI proposal allows for the ability for the CP irrigators to be variably controlled to avoid irrigating specific areas.

Peat bog. The peat bog on the eastern side of the site requires wheel bridges for the CPI irrigator, and concern was raised whether the cost estimate for this was sufficient.

Budget estimate for wheel bridges over peat bog reviewed and updated. An alternative exists to ‘split’ the eastern CP irrigator into two separate irrigators either side of the peat bog, and avoid the peat bog altogether. This is a similar cost to the updated estimate for wheel bridges.

Staging of CPI. The cost estimate for SDI shows staged implementation of capacity (3,600m3/day initially, 4,500m3/day subsequently). Following peer review feedback, staging of the last 20% of CPI has been allowed for in estimates, to ensure like-for-like comparison with SDI

To effect this comparison: The estimate allows for 20% of the pivot

irrigator cost to occur in year 10. A NPV saving.

Irrigators will need to be nozzled to achieve instantaneous flow rates equivalent to 4,500m3/day (ie 52 L/s), for flushing of the Transfer Pipeline.

When irrigating at this higher rate, irrigator travel speed will increase so that the mm/day application rate is not exceeded.


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Item Method of Comparison

Option of SDI with Baseload Membrane Filtration (MF) and bypass This is a new option of a MF plant only sized for 2,400m3/day for stage one. This is on the basis that there will be very few days when flow exceeds this, and the excess flow could be managed through a 120micron bypass strainer. This option has the unconfirmed assumption that the algae in occasional bypass flow does not present a risk to fouling of the soil surrounding the SDI emitters. Stantec’s internal reviewer’s clear opinion is that algae that bypasses the MF plant presents an unacceptable risk of fouling the soil surrounding the subsurface irrigation emitters.

A new option 3A has been introduced for the SDI, being ‘baseload MF + bypass’. S7.5 has been updated to reflect this. The bypass would require duty/standby 120 micron strainers, to ensure reliability during peak events. Note, this option cannot proceed without expert reassurance of the algae blinding risk of the subsurface irrigation field, and subsequent acceptance of the risk by SDC. Algae can pass through a bypass filter. In discussion: Risk is the combination of likelihood and

consequence. In this situation it is the severe consequences of algae blinding that are of concern – potentially requiring the replacement of the irrigation field.

The provision of a bypass options introduces the possibility of bypass occurring more frequently than intended, for operational ease.

2.2 Transfer Pipeline Size Ecogent proposed reducing the size of Transfer Pipeline (Te Anau to Kepler) from 250mm id (for CPI) down to 225mm id for the SDI option, on the basis that peak flows can be reduced for SDI. It is suggested this reduction is possible because the peak flow occurs after an extreme weather event where the imperative is to pump down the buffer storage at the Te Anau ponds. This is on the basis that SDI is likely to be able to irrigate more volume during an extreme rain event, and therefore more of the 15,000m3 additional storage required by the Kepler resource consent would be available to moderate the peak pumping flow. Reducing the peak flow might also reduce the size of the membrane filtration plant, as it is sized on operating the pipeline at design flow, from time to time, for flushing. After consideration and discussion with SDC, a reduced pipe size was not pursued, the principal reasons being:

Consented flows are based on a 35yr horizon, it is realistic to expect population growth continues. The expected pipeline life is 100 years, the larger size provides some future proofing. Future proofing is considered important given the potential Te Anau has shown for growth. A consent for discharges up to 4,500m3/day is to hand. Further discussion with Tony Davoren (Aqualinc) has provided reassurance that under centre-pivot

the soils can accept high drainage rates when above field capacity. While further modelling will be done to refine results, the outcome is that peak flows from CPI are not expected to be significantly higher than for SDI.

2.3 Updated SDI layout (Option 3) Stantec and Ecogent independently identified Option 3, a further refinement to the physical layout of the SDI system of mainlines, driplines and flushlines. Both concepts are similar, this Basis of Design is based on the Stantec layout. Should SDI proceed to detailed design then it is expected that the features of both systems would be assessed to develop an optimised solution. At this stage it is felt the cost and features of either layout are comparable.

Option 3 enables significant reductions in pipe sizes and this has been used as the basis of the cost estimate.

Specific Details for Option 3 Ecogent provided a considerable amount of comment to support their Option 3. This information has generally not been added to the Basis of Design report as it is of more specific detail. It is understood the


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principal reason for this being supplied is to show how key design risks might be managed, and this has been considered when reviewing the key risks.

2.4 Biofilm Dosing for main Transfer Pipeline This has been deleted after receiving feedback.

2.5 Site Drainage Control The cost estimate has added a provision for basic site contouring work to improve the large scale surface drainage patterns on the site. The allowance for CPI is greater than SDI, to acknowledge CPI is more sensitive in extreme events.

2.6 Additional Hydrus Modelling Hydrus modelling by Aqualinc has compared nitrogen removal performance of CPI against SDI (with upstream membrane filtration). The results are appended, and with regard to nitrogen removal, clearly support the proposal of the irrigation area of SDI being reduced in proportion to the percentage of nitrogen removed by the membranes. This is discussed further in s7.18.

2.7 Further Modelling for Irrigation During Extreme Weather Feedback from the reviews highlighted the desirability to further understand how extreme weather events may affect the ability to irrigate. This affects the way the additional storage is used, with consequential effects on peak flows to irrigation, and potentially even the amount of storage. It was considered that CPI was more sensitive in this regard. This work is supplementary to the appended NTC29.

To provide resilience to previous estimates, the modelling will be based on a mass balance approach. A methodology has been agreed with Tony Davoren of Aqualinc. It will only assess the situation when the soil is at or above field capacity, as this is worse-case.

Modelling will assess a safe limit of water that can be applied to the site before the risk of ponding or runoff exceeds that allowed by the Discharge Permit. The limit will be expressed in equivalent mm – combined rainfall and irrigation. Modelling will then also derive drainage rates back to field capacity. From this the amount water that can be applied daily can be finalised. Precautionary guidelines will also be established for rest periods after heavy rain.

Initial assessment (from investigations undertaken for the resource consent) confirm that the soils can achieve relatively high drainage rates, meaning that restrictions on irrigation for significant lengths of time (in terms of storage), are unlikely.


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3. Resource Consents This section discusses the current state of resource consents for the project. This is then used to inform the minimum requirements for performance.

3.1 Kepler Discharge Consent Discharge Permit 302625 was issued, effective 16 January 2017 for a centre pivot irrigation system to discharge wastewater to the Kepler site, the purpose being:

Two key aspects are the reference to spray irrigation, and an allowable irrigation area of 115Ha. Appendix E contains a diagram from the consent that defines the ‘consented irrigation area’ referred to in 2(b), and the Designated ‘North Block’ area. Exact boundaries and areas will be established by survey in May 2018.

Key Dates Key dates for Discharge Permit 302625 are:

Commencement Date: 16 January 2017 Shall lapse if not given effect to within five years of it commencing Expiry date: 22 January 2040.

Consent Requirements – Irrigation Volumes and Depths Condition 5 of the consent presents several constraints relevant to the design of a layout for an irrigation system. The full text of condition 5 is shown below. Key aspects relevant to an SDI design are:

The maximum daily discharge permitted between the 1st of September and the 30th of April is 4,500m3/day

The maximum daily discharge permitted between the 1st of May and the 31st of August is 2,000 m3/day The depth of wastewater application that can be applied between the 1st of September and the 30th

of April cannot exceed 6.5mm/day. This value was originally based on dividing the maximum summer daily discharge of 4,500m3/day by the originally proposed area of 69 Ha. This was the area that could readily be irrigated by two centre pivot irrigators that were as large as could be readily fitted within the site

The depth of wastewater that can be applied between the 1st of May and the 31th of August cannot exceed 2.9mm/day (This value was originally based dividing the maximum winter daily discharge of 2,000m3/day by 69 Ha).


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Full Text of Consent Condition 5

The full text is shown below, as the wording needs to be carefully understood:

Consent Requirements – Nitrogen Removal A land application design is required to remove nitrogen, the key consent requirements are:

The consent permits the application of 290kg N/ha/yr (nitrogen per hectare per year). Condition 5c, as above

However, the loss of nitrogen to groundwater from the Kepler ‘North Block’ shall not exceed 32 kg N/ha/year (condition 7e). This value is taken as an average over the whole area of the Kepler ‘North Block’, which is about 121Ha, being the defined irrigation area plus a buffer zone.

Partial Text of Consent Condition 7(e)

Consent Requirements – Additional Storage A total of 15,000m3 of additional storage is required as below:

Condition 6(c). Prior to commencement of the wastewater discharge on the North Block, a minimum of 10,000 cubic metres of storage shall be provided as a contingency measure for extreme weather events and/or equipment breakdown

Condition 13(a)(viii): [The Environmental Management Plan shall include]… how the 10,000 cubic metres storage facility required by Condition 6(c) shall be managed for extreme weather events and/or equipment breakdown and how the treatment ponds, wetland system and irrigation will be operated to provide an additional 5,000 cubic metres of storage capacity in anticipation of forecast rainfall events. This is to be reviewed annually.

Refer to Appendix E for a map of the consented area.


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3.2 Discharge Consent to Upukerora River Discharge Permit 20157778-01 currently exists to allow the discharge from the existing wastewater ponds and wetland to the Upukerora River. Condition 1 of this consent states that this consent authorises the following discharges:

a) treated wastewater, at an average monthly flow rate of up to 1,400 m3/day from the Te Anau township wastewater treatment plant into the Upukerora River, and

b) a portion of the treated wastewater into land through the base of a “wetland ditch”.

Key Dates Key dates for Discharge Permit 20157778-01 are:

Commencement Date: 9 November 2015 Expiry date: 30 November 2020.

3.3 Discharge to Air at Existing Ponds Site Discharge Permit 20158286-01 currently exists to discharge contaminants to air from wastewater treatment at the existing wastewater ponds and wetland to the Upukerora River. Condition 1 of this consent states:

1. This resource consent authorises the discharge of contaminants, particularly odour and spray, to air from a wastewater treatment system, as described in the application for resource consent dated 13 November 2015 and the further information provided on 3 May 2016. The scope of the activity is described in the application as being, amongst other things: the treatment system consists of a screen, an oxidation pond and maturation ponds with

a combined surface area of 4.8 hectares, wetland and mechanical aeration.

It is noted that this condition is specific to the existing treatment systems on site and does not include new treatment systems.

Key Dates Key dates for Discharge Permit 20158286-01 are:

Commencement Date: 30 June 2016 Expiry date: 30 June 2041.


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4. Design Flows Design Flows are characterised in the MWH June 2013 ‘Te Anau Wastewater Flows Report’, submitted as Appendix F of the Kepler Resource Consent Application. Subsequent to the above report, the following additional information is available:

MWH Notice to Client (NTC) 30, dated 1 December 2016, updating Average Daily Flows data 2010 – 2018 data for rainfall and inflow to the Te Anau ponds. This is summarised in the charts in

Appendix B.

Note that allowance for annual growth, as in Flows Report, shall be allowed for.

4.1 MWH NTC29 – First Stage SDI MWH NTC29 of November 2016 (Appendix C) detailed the proposed minimum design flow for the first stage of an SDI system. It is noted that this NTC allowed for:

Growth in flows (derived from 2013 Flows Report) Recognition of above-average growth of inflows subsequent to the 2013 MWH report Allowance for a 1:10 year flow to be higher than observed flows from 2010-2016.

4.2 Recent Flows Subsequent to the 2013 Flows Report, higher averages for winter and summer flows have been sustained, as tabled below. Reasons for these increases have not been determined.

Table 4-1: Average Pond Inflows for Mid-Summer and Winter

Year Mid-Summer (1 Dec–28 Feb) Average Flow –

m3/day

Winter (1 May – 31 Aug) Average Flow –

m3/day

Peak 3 day inflow*

m3/day

Peak 3 day inflow** plus rain on ponds

m3/day

2011 1,053 (2010/11) 662 1,391 (1-3 Jan) 1,551 (6-8 Jan)

2012 954 (2011/12) 682 1,439 (29-31 Dec) 2,657 (15017 Sept)

2013 1,002 (2012/13) 651 2,083 (26-28 Oct) 2,650 (26-28 Oct)

2014 1,007 (2013/14) 865 1,915 (1-3 Jan) 2,546 (1-3 Jan)

2015 1,015 (2014/15) 915 2,197 (6-8 Oct) 2,415 (5-7 Oct)

2016 1,430 (2015/16) 1,179 2,586 (18-20 May) 3,333 (25-27 Feb)

2017 1,447 (2016/17) 897 2,315 (17-19 Sept) 2,881 (17-19 Sept)

Av for 2010-17 1,165 m3/day 836 m3/day

* The average daily flow over the worst 3 days of the year of pond inflow. Excludes additional flow from rain on the ponds.

** The average daily flow over the worst 3 day period of the year when combining pond inflow and volume of rain landing on the ponds.

5. Design Loads MWH NTC32 of 6 December 2016 (Appendix D) detailed design nitrogen loads for SDI and CPI options. This was for the brief for Hydrus modelling to allow comparison of centre-pivot and SDI irrigation systems. Design influent load (to the ponds) and effluent load (from the ponds) in terms of BOD and bugs are detailed in the Kepler Consent AEE, and the evidence used in the design of the odour Trickling Filter. Refer also to table 2.2, page 10, of the Kepler resource consent application.


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6. Project Constraints The following constraints are adopted for this Basis of Design.

6.1 Business Case SDC prepared a Business Case for the project, dated December 2017. This will be updated with the refined SDI concept and costings that arise out of this Basis of Design document. The Business Case sets out the Needs for the project, the Investment Objectives, the Key Constraints and provides a framework for how options are evaluated.

The Business Case framework will not be amended, unless specifically stated in this report. Relaxation of the Key Constraint (s2.6). ‘Implement before 30 November 2020’, is the only amendment proposed, and is discussed below.

6.2 Resource Consents This section discusses the consent conditions that SDC has determined might or shall not be open to revision.

Non-Contestable Consent Conditions SDC has determined that the following consent conditions be adopted for the purposes of design.

Pasture management will be by cut and carry (condition 7a). 4,500m3/day maximum daily discharge during summer months (condition 5a) 15,000m3 additional storage (conditions 6c and 13a viii). 290kgN/Ha/yr maximum application of nitrogen (condition 5c). 32kgN/Ha/yr maximum loss of nitrogen to groundwater averaged over the whole North Block

(condition 7e). The date of 22 December 2021 to give effect to the Kepler Discharge Consent (5 years after the

appeal was withdrawn, s116 RMA). The consented irrigation area (North Block) remains the same (condition 2b).

Contestable Consent Conditions SDC determined that if the SDI case is sufficiently compelling, it is prepared to revisit the following consent conditions. This is because they are not seen to fundamentally affect the bottom line environmental effects that are protected by the ‘non-contestable’ conditions above and may add flexibility and resilience into the operation of the scheme.

Application depths of 6.5 or 2.9mm/day for summer and winter respectively may be increased (condition 5b).

2,000m3/day maximum daily discharge during winter months may be increased (if environmental effects can be proven to be acceptable).

Extending the date of 30 November 2020 to cease discharge to the Upukerora River, to coincide with the 22 December 2021 date to give effect to the Kepler Discharge Consent.

6.3 Technical Technical constraints apply as detailed in this section.


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Life of System The scheme shall be developed with component lives generally as follows:

Table 6-1: Minimum Life of Major Components

Component Design Life (years) Main pipeline from Te Anau to Manapouri 100

Civil works, including buildings, raising ponds, fences etc 50

Mechanical components, pumps, valves 25

Irrigation system 25

Electrical and control equipment 25

Design Capacity The scheme shall be designed to be able to achieve the consented capacity of 4,500m3/day before the end of the currently consented period (Jan 2042). Developing the scheme is stages to achieve this capacity can be considered where subsequent stages do not require major rework of existing infrastructure, and can be justified financially.

Instantaneous Flow Rate and Duration Two key design parameters are:

The scheme shall be designed for a sustained instantaneous flow rate of 52 L/s indefinitely A pipe flow velocity in the Te Anau to Kepler pipeline of 1.1 m/s shall be able to be maintained for

a minimum of 4 hours. The basis of this is:

The Transfer Pipeline between Te Anau and the Kepler Block needs to be able to achieve the consented flowrate, for the life of the asset. It has an expected 100 year life.

To achieve the maximum consented discharge rate of 4,500m3/day, wastewater would need to be discharged at a constant rate of 52L/s throughout a 24 hour period. The ability for higher flow rates should be investigated in detailed design to allow a contingency for the daily discharge to be achieved in less than 24 hours.

52L/s is the minimum flow rate for the Transfer Pipeline (if 250mm internal diameter), to achieve pipeline scour and sediment transport velocities. (Refer Stantec Report ‘Te Anau Treated Wastewater Transmission Pipeline – Preliminary Hydraulic Design’ December 2017)

A 250mm id pipe is the smallest diameter option, otherwise headloss becomes excessive. This sustained flow is considered sufficient to flush sediment and air along the Transfer Pipeline a

sufficient distance to prevent reversal. Refer to the ‘pipeline’ section Investigation by Stantec has confirmed that flow velocities in the order of 1.1m/s (equivalent to 52

L/s in a 250mm bore pipe) will need to occur in the Transfer Pipeline at times, for up to 4 hours, to ensure air is positively transported between air valves. This is based on an internal Stantec report that found that during flushing, air could be transported along the downslope sections of the pipeline at 10% of the general velocity. Therefore air transport at 0.11 m/s. If air valves are assumed to be 1km apart this infers 10,000 seconds (3 hrs) to positively flush air to the next air valve. This is increased to 4hrs to provide a margin of safety.

Effective flushing of air is required principally: To avoid increasing loss of pumping efficiency as air accumulates over time in minor high

points not directly served by air valves. To ensure that recommissioning the Transfer pipeline after major air ingression (for any reason)

is able to be achieved efficiently, with minimal staff input. Priming a pipeline with inadequate air management can be difficult.


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Further considerations that may increase the instantaneous rate beyond 52L/s are:

Additional flushing flows in the SDI dripper lines are occasionally required. The subsoil irrigation system is required to be capable of achieving minimum flushing velocities in the range of 0.3-0.4 m/s at the far end of each dripper line (email correspondence with John Wicken, Waterforce sales engineer). These velocities are required to remove sediment and algae build up. For example, each flushing zone in layout option one (refer Appendix F) has 66 x 17mm dripper lines, giving a flushing flow of 6 L/s at 0.4m/s.

Increases of the flow rate above 52L/s may improve air transport in the Transfer Pipeline and reduce the requirement for air valves.

SDC may require a safety margin to achieve the 4,500m3/day in less than 24 hours. A larger Transfer Pipeline diameter will likely require a proportionally higher instantaneous flow rate.

Future Capacity Beyond the current consenting horizon, the design shall provide realistic options for an (arbitrary) increase in future flows to 6,000m3/day, with proportionate increases in load. Options such as booster pumping may be considered, the key requirement being options that efficiently reuse existing infrastructure. The basis for this requirement is that the pipeline will have 100 year life, and this provides an arbitrary allowance for growth of flows beyond the current consenting term. This requirement accepts that further wastewater treatment processes may be required to meet future discharge standards. SDC have an ongoing programme to manage inflow and infiltration, and it is noted this will have an effect on future design flows.


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7. Specific Process Elements – General and SDI A preliminary Process Flow Diagram (PFD) (Appendix A), highlights the key process elements for both a Centre Pivot option and an SDI option. This section describes each of the elements for the SDI process in further detail.

7.1 Existing Ponds Table 7-1: Summary Process Element – Existing Ponds

Attribute Description

PFD Element ID 1

Description Existing Ponds

Purpose Pond 1, facultative. Normal oxidation pond functions. Reduction of BoD, settling of solids, digestion of solids:

Ponds 2 and 3, maturation (pathogen reduction is a normal function of a maturation pond).

Required for Centre Pivot or SDI CPI and SDI

Size At normal operational level: Pond 1, 3.3Ha Ponds 2 and 3, 0.75Ha each.

Fit for Purpose evidence MWH NTC27 confirms pond efficiency for present and future flows up to 4,500m3/day.

Matters remaining None for Pond 1 – continuing its existing use Ponds 2 and 3, potential to use for different function or

ultimately abandon, as maturation function is probably not needed if discharging to land.

Key Risks Odour from ponds 2 and 3, if abandoned (and not cleaned out) or put to new use.

Odour (pond 1) from sludge overload from membrane filter backwash.

High leakage to ground. Issues with sludge from membrane (eg not settling).

Mitigation of Risks Proposed: Ensure any changed use for Ponds 2 and 3 consider odour and environmental effects Other: Desludging as necessary to maintain hydraulic volume Lining of ponds.

Further Comment None.


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7.2 Additional Storage Table 7-2: Summary Process Element – Additional Storage


PFD Element ID 2

Description Additional Storage

Purpose Prevents overflow of ponds to Upukerora river when irrigation unavailable in extreme conditions or for operational reasons.

Meets consent conditions 6(c) and 13(a)(viii):

Required for Centre Pivot or SDI CP and SDI, noting SDI less demanding on storage (see below).

Size 17,000m3 for SDI 25,000m3 for CPI

Fit for Purpose evidence Meets resource consent Discharge Permit 302625 Stantec NTC 29, modelling of extreme events for SDI Stantec NTC 27 confirming efficiency of Pond 1 Memo T. Davoren, Aqualinc, 25 July 2018, ‘Kepler Block Irrigation

Limitations’, for CPI.

Matters remaining Determining most efficient method of achieving storage. (Stantec Issues and Options report commissioned).

Consideration of whether ponds 2 and 3 can be repurposed. Check whether NTC27 needs updating to cater for occasional

times of higher Pond 1 levels if used for additional storage. Further confirmation of volumes for SDI and CPI, after further

modelling of extreme events, and field assessment of ponded areas, soft areas when wet and catchments that drain to the affected areas along with analyses of return frequencies

Key Risks Storage insufficient – pond overflow to Upukerora River in an extreme event

Growth of Te Anau further increases infiltration and inflow into sewerage beyond predicted levels in MWH 2013 Flows Report

Mitigation of Risks Proposed: Pumping and irrigation capacity is 50% greater than peak pond

inflow, to allow recovery of storage capacity. Further modelling of requirement for storage during extreme

weather events. Modelling based on mass balance of soil storage capacity and drainage rates.

Other: Further storage Resource consent for ultimate overflow (if Additional Storage all

used up) to Upukerora River or infiltration field at Kepler.

Further Comment It is noted that the consent requirement for additional storage is based on centre pivot irrigation. In comparison, SDI can operate under a wider range of conditions, a crucial one being during extreme rain events until the soil moisture content reaches saturation when daylighting will occur. This is because SDI is less likely to result in surface runoff and ponding as soil moisture content increases, at a time when pond inflows are likely to be high. No matter the irrigation system, when soil moisture content reaches saturation redistribution or runoff and ponding will occur – for CPI directly at the surface and for SDI because there will be daylighting above emitters or as a result of lateral movement to lower areas. For the same amount of storage, SDI offers a higher factor of safety compared to centre pivot. However, as stated in section 5 of this report, a reduced storage volume will not be sought.


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Aqualinc Assessment of Storage Requirements Further assessment has been undertaken by Aqualinc in July 2018 in their memo ‘Te Anau WWT Irrigation – Kepler Block Limitations’. This memo assessed the ability of the soils to accept water from either rainfall or irrigation. The report looked in detail, in particular, at the ability to accept water when above Field Capacity, and the depth which can be relied upon to be utilised as transpiration by the pasture and/or drain through the soil profile. Rain and irrigation flows since 2010 were modelled, with the May 2016 weather event being the most extreme event since 2010 – not because of the peak rainfall but because of the duration of rainfall days and the accumulated rainfall. The Aqualinc Report indicated catering for this event required storage, for CPI, of 20,000m3 and to provide a margin of safety 25,000m3 is proposed. The storage requirements for SDI were also qualitatively assessed, noting that there are different mechanisms between SDI and CPI in the way that the soil reaches a point where no further irrigation is possible. SDI will daylight or CPI will not infiltrate, in either case the cause being days of continuous rain that increase soil moisture content to saturation. While direct comparison isn’t possible, the opinion of the author of the report considered that the application advantages of SDI (irrigate the various blocks over short periods of opportunity) meant that SDI could potentially operate for longer. How much longer depends on rainfall depth (vis. Accumulation of 40mm will raise soil moisture from field capacity to saturation) and duration of rainfall events (a single event over a day or two is less severe than an event that lasts for 20 days as occurred in May 2016).3-At a winter irrigation limit of 2,000m3/day, every day SDI could irrigate is a saving on storage capacity. The daily water balance modelling shows that no matter the soil moisture limit for irrigation, rainfall during such events as May 2016 restricts the opportunity for any irrigation. Given that the proposed SDI field is 20% smaller than the CPI field a pro-rata adjustment suggests that Additional Storage for SDI can be 8,000m3 less, or 17,000m3. Options Report An Options report is being prepared by Stantec (August 2018) to determine the best way to achieve the additional storage. While the project cost estimate is based on raising Pond 1, this is only intended for budgeting purposes and is not to restrict options. The Options Report will consider options such as new constructed storage, lowering normal operational levels, and repurposing ponds 2 and 3. Options will also consider how any future improvements to treatment processes at Te Anau WWTP could be included. For example the addition of a membrane filtration plant. Overflow Provision Assessment by Aqualinc confirmed that it is always possible an extreme event could exhaust the Additional Storage. This would likely be due to a period of high rainfall over many days. If this eventuality is to be specifically catered for, an overflow route to either the Upukerora River or an infiltration field at the Kepler Block are the obvious options. The existing scheme flow capacity of 4,500m3/day would meet overflow requirements. Detailed assessment may enable this flow to be reduced. Specific resource consents would be required. Given that the proposed storage for SDI is less than for CPI, the risk of requiring such an overflow provision is comparable for both options. If it were to proceed, consideration should be given to:

Acceptable frequency of its use If an infiltration field is used, whether a reduction of Additional Storage can be justified.


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7.3 Pond Outlet Screen Table 7-3: Summary Process Element – Pond Outlet Screen


PFD Element ID 3

Description Pond outlet screen, with self-cleaning facility

Purpose CPI: Primarily, debris screening to protect pumps and allow a more efficient pump type. Secondarily, to reduce algae pumped to Kepler.

SDI. Prescreening for gross debris to protect the Membrane Inlet Screen


Size Two screens, Duty/standby tbc, but initially sized at 78l/s, being the max flow + 50% SDI screen mesh size tbc, but 6mm (in both dimensions) as initial

assumption. CPI screen mesh size tbc, but refer to preliminary hydraulic

design.

Fit for Purpose evidence Stantec report: Te Anau Treated Wastewater Transmission Pipeline – Preliminary Hydraulic Design

Matters remaining Selection of a specific screen type, and mesh size Providing suitable access for maintenance Ensuring screen can cope with operational range of pond level.

Key Risks Screen is hard to keep clean, therefore loss of flow capacity

Mitigation of Risks Proposed: Self cleansing mechanism Duty/standby arrangement 50% additional capacity per screen (tbc) Additional storage of 15,000m3, as required by consent.

Other: Dual screens

Further Comment The pond outlet screen may potentially vary between a centre-pivot and SDI scheme. SDI includes a membrane filtration plant, and this will have an additional screen, potentially meaning the Pond Outlet screen can be for coarser debris.

The pump intake screen would be located in the oxidation pond. The primary function of the screen is to limit the size of debris and particles that can enter the system. The screen must be self-cleaning to prevent the build-up of algae and slime. It must also provide a low approach velocity and low head loss.

The outlet screen must be able to cope with algae, which is present on the pond surface and extends down approximately 30 cm. There is also the potential for slime build up on parts that are immersed in water.

The screens must be able to deal with a small amount of pond level change, expected to be in the order of 200mm. This is unless situated in a pond that caters for the additional storage, in which case the range may be in the order of 800mm (to be confirmed).

Section 8.2.1 of the Pipeline - Preliminary Hydraulic Design report discusses pond outlet screen options. There are a variety of proprietary screens available, the report identifies a ‘Kleenscreen’ product as a viable option (for subsequent pumping direct to a centre-pivot irrigation scheme), but a final choice will be made at the detailed design stage.


Page 16

7.4 Membrane Inlet Screen Table 7-4: Summary Process Element – Membrane Inlet Screen


PFD Element ID 4

Description Membrane Inlet Screen

Purpose Protection of membrane from abrasive debris Some reduction of algae solids onto membranes to reduce

backwashing

Required for Centre Pivot or SDI SDI

Size tbc, but initially sized at 104 L/s, being the max flow + 100% Mesh size tbc, but typically 1mm in two dimensions.

Fit for Purpose evidence tbc. However Masons Ltd have recently designed and installed a similar screen (as discussed below), for pond discharge to a similar sized membrane filtration plant at Motueka.

Matters remaining Final sizing, specification and selection of screen type Decide on whether to have duty/standby screens

Key Risks Algae clogging

Mitigation of Risks Proposed: Self cleansing, easy access for maintenance. Sized for spare capacity when under high loading Other: Duty/standby screens, of potentially smaller capacity

Further Comment The Motueka WWTP project (Average Dry Weather Flow capacity of 4,700m3/day and peak of 5,500) also takes wastewater from the outlet of a pond and into a membrane filter. For this project the inlet screen used was a Johnson Versa model 20 0.9mm perforation in two dimensions. These are inclined drum screens.

Figure 7-1: Motueka WWTP membrane inlet screen


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7.5 Membrane Filtration Table 7-5: Summary Process Element – Membrane Filtration


PFD Element ID 5

Description Membrane Filtration (MF) plant

Purpose Primary: removal of algae and suspended solids to control risk of blockage of SDI subsoil driplines, emitters and in the soil surrounding the emitters

Further benefit of reducing nitrogen by approx. 20% for component bound in solids

Additional benefits relating to filtering of bacteria and some viruses (although some regrowth can be expected)


Size Option 1: 4,500m3/day (net output after stoppages for backwash etc)

Option 2: 2,400m3/day base flow capacity, with peak flow bypass through duty/standby 120 micron filters

Membrane pore size tbc (0.04 – 1 micron typical)

Fit for Purpose evidence As used for pond effluent from slightly larger Motueka and Cromwell plants. Commissioned 2017/18 respectively.

Membrane pore size a physical barrier. For bypass strainer – 120micron is as used for SDI field. MWH NTC32 of 6 December 2016 (Appendix D) that indicates

filterable N

Matters remaining Confirmation of: Influent water quality for which the design capacity is to be

achieved (lower water quality requires more membranes) Final proportion of N removed Pore size, to be based on a performance specification. Effect on ponds from returning backwash stream to ponds

Key Risks Algae blockage of membrane Algae will pass through bypass strainer, and SDI dripline emitters.

Risk of algae fouling of soil surrounding the emitters. Effect on ponds from returning backwash stream to ponds,

including backwash not settling. Mechanical or electrical failure (forcing system shutdown, as MF

must not be by-passed).

Mitigation of Risks Proposed: Budget allowance to reduce algae load onto membranes. Expert opinion required on risk of algae fouling in SDI field (when

bypassed through strainers). Duty/standby or redundancy in key equipment items, including

generator plug-in point. Review of performance of Motueka and Cromwell plants Pre-filtration at Membrane Inlet Screen Review effect of backwash on ponds. Other:


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Further Comment The MF plant would be designed for the final design flow with regard to footprint, pipework, electrical capacity etc. A reduced capacity would be achieved by leaving out some membrane racks or modules. Backwash flows in the order of 20% are expected, and this flow would be returned to the head of pond 1, to allow solids to settle. A membrane pore size of 0.04microns has been used at similar plants at Motueka and Cromwell, but has not been specifically determined for this project. This may be vendor specific. To finalise, the selected vendor would conform to a detailed performance specification.

Opportunity for Smaller MF Plant (with bypass) for SDI A suggestion was offered by Peter Riddell, Ecogent Ltd (email of 11 April 2018) that a 2,400m3/day (28 L/s equiv) MF plant might be possible, at least initially. This is on the basis that flows in excess of 2,400m3/day are very infrequent, and that higher 52 L/s flushing flows were of short enough duration to allow this flush water to be built up in balance tanks prior to pumping. This suggestion has been considered, and a new option added and priced to cater for it noting:

It is necessary to retain the capability of 4,500m3/day to allow rapid recovery from when additional storage at the Te Anau ponds is used. Eg a requirement to pump pond inflow plus reduce accumulated storage.

Analysis of the requirements for air transport, and potentially sediment transport in the pipeline show that it is desirable, if not necessary, to be able to regularly operate the pipeline at full flow (4,500m3/day or 52 L/s) for sustained periods of time. This may be in the order of 1 – 4 hours. It will require operational experience to determine these flush durations. Therefore this Basis of Design assumes that the plant must be able to operate at full flow for extended periods of time.

A larger balance tank at the Kepler block could receive and store higher flows (eg an extra 26 L/s for four hours), but this offsets the saving of the smaller plant.

Bypass Filtering:

Based on the above flow requirements, if the MF plant is sized for baseload flows, a bypass flow through a strainer would be required. It would be sized to prevent blockage of the SDI dripline emitters. However, algae commonly found in oxidation ponds can be too small for strainers. They range in size as below (source: K Norquay, Stantec).

Euglena - Length ranges are 34-78 and width 5-24 μm Closterium - Length 25 - 400 μm, width 2.5 - 8 μm Chlorella - It is spherical in shape, about 2 to 10 μm in diameter.

The principal concern is that algae blinding of the soil around an emitter must be avoided. Therefore before this option is committed to, expert confirmation is required that algae blinding (fouling) of the soil is not a realistic risk.

Stantec sought advice from John Cocks, their internal reviewer, regarding this proposed option. After consideration, John’s advice was very clear that this option should be avoided. This opinion was based on three fundamentals:

Underlying Principle: The integrity and performance of the SDI field is a critical process element, with no real bypass option. For such an element, prudent design is to add redundancy, whereas allowing occasional algae bypass reduces redundancy.

Experience: John’s experience with rapid infiltration basins (RIBs) is that algae blinding is a very real factor. In RIBs, sacrificial sand layers (or similar) can be added, such that they can be dug out and replaced as needed. Yet even with this some bypassing can occur and algae clogging can bypass performance. This option would not be possible for an SDI field.

Technical: The USEPA manual identifies algae blinding as a risk.

The conclusion regarding this option is that it should not be pursued unless specific expert evidence can be obtained that addresses the above concerns. Operational evidence from similar projects is also highly desirable.


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7.6 MF Balance Tank Table 7-6: Summary Process Element – MF Balance Tank


PFD Element ID 6

Description Balance Tank

Purpose Primary: Even out flows between MF plant and Transfer Pipeline. MF

plant will be stop/start operation, including during backwash (eg 90 seconds every 15 minutes).

Make allowance for the time required to stop/start or change flows in the Transfer Pipeline

Secondary: Additional storage to further reduce operational complexity for

transfer pipeline Provision of additional volume of water for pipeline flushing if MF

plant capacity less than desired flushing flow.


Size 100m3, based on a minimum calculated requirement of 88m3

Fit for Purpose evidence No specific report done regarding size. However a preliminary calculation of minimum volume is given below

Matters remaining Finalising size, with more detailed analysis of factors affecting volume, balancing smaller size (cheaper) vs operational flexibility (larger, most expensive)

Confirm the assumption that no odour treatment required on balance tank vent

Key Risks Undersized, making control of pumping to Kepler more difficult

Mitigation of Risks Proposed: Design site layout to allow easy installation of an additional tank Allow for factor of safety on minimum theoretical size Other:

Further Comment Reference is made to the Stantec report: Te Anau Treated Wastewater Transmission Pipeline – Preliminary Hydraulic Design. s11.6.1 gives:

570 seconds to ramp pump flow from 0 to 52 L/s (gives 15m3/s at an average flow of 26 L/s) 300s from max flow to zero flow (gives 8m3 at 26 L/s).

The following calculation is to be properly confirmed, but initial sizing, based on an assumed 5m diameter tank is shown below, and assumes the balance tank will need the following volumes:


Page 20

Table 7-7: MF Balance Tank initial sizing (tbc)

Storage Element Volume (m3)

Minimum submergence from inlet invert to floor of tank. Assume 300mm 6

Minimum submergence over outlet pipe invert. Assume 1m 20

Low level alarm volume between minimum submergence and min operating level. Assume based on 1.5 times the 300s time to stop the pipe flow

12

Operating volume. Assume 2 x the 570s time to ramp the pipe flow up to full flow. (570s x 2, x52/2)

30

Volume above operating volume to allow time for high level alarm to work. Assume based on taking 2 minutes to stop flow from membrane plant at 52 L/s

6

Freeboard to overflow invert (200mm) 4

Head over overflow invert to drive 52 L/s (assumed at 500mm) 10

Total minimum storage 88m3

Notes:

The above calculation excludes provision of additional volume of water for pipeline flushing if MF plant capacity less than desired flushing flow.


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7.7 Biofilm Control Dosing This Process Element was initially proposed by has been deleted, May 2018. Biofilm control dosing will still occur in the pipework for the SDI disposal field. The reasons for deleting it are that a proper flush regime is proposed for the Transfer Pipeline, and duty/standby filters prior to the SDI disposal field.

Table 7-8: Summary Process Element – Biofilm Control Dosing


PFD Element ID 7

Description Hypochlorite dosing generating hypochlorous acid.

Purpose Inhibits biofilm growth in Transfer Pipeline. Biofilm sloughing can cause clogging issues for SDI dripper lines and emitters


Size Not yet sized

Fit for Purpose evidence Deleted – May 2018.

Matters remaining Determining dose levels for effective biofilm control, noting hypochlorite (or alternative) will react with TOC and ammonia as well.

Confirming whether other chemicals are more effective

Key Risks Level of dosing hard to confirm, issues with under or over dosing High operating costs arising from high levels of dose required. Effects of residual on soil and biota at the SDI disposal field Adverse environmental effects of chlorine dosing Lack of hard data to base design upon

Mitigation of Risks Proposed: Seek comparable examples (potentially Liverpool-Ashfield

Pipeline near Sydney). Rigorous commissioning regime

Other: Larger ‘rearguard’ filters at Kepler site



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7.8 Pump Station Table 7-9: Summary Process Element – Pump Station


PFD Element ID 8

Description Pump Station at Te Anau ponds site

Purpose Transfer wastewater from Te Anau ponds site to Kepler site

Required for Centre Pivot or SDI CP and SDI

Size 52 L/s (+ 5%?) and 4,500m3/day.

Fit for Purpose evidence Stantec report: Te Anau Treated Wastewater Transmission Pipeline – Preliminary Hydraulic Design, December 2017

Matters remaining Determine whether a higher pump rate than 52 L/s is desirable so that 4,500m3/day can be achieved with some downtime

Refer to Preliminary Hydraulic Design Report

Key Risks Pipe roughness greater than assumed – affects capacity Mechanical or electrical failure of key components

Mitigation of Risks Proposed: Conservative pipe roughness, and ensure pipe pressure class

appropriate Duty/standby or redundancy in key equipment items, including

generator plug-in point. Ensure manual control possible

Other:

Further Comment The Preliminary Hydraulic Design Report outlines the pumpstation requirements in detail, and identifies that there are readily procurable components (eg pumps) to meet the requirements. The Stantec memo on Air Travel Management indicates that flushing flows of at least 1.0m/s (ie full flow) lasting for 1-4 hours will be required to ensure that air pockets are moved positively along the pipeline to the next air valve.


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7.9 Transfer Pipeline Table 7-10: Summary Process Element – Transfer Pipeline


PFD Element ID 9

Description Pipeline between Te Anau Ponds and Kepler Block.

Purpose Transfer wastewater to the Kepler site

Required for Centre Pivot or SDI SDI and CP

Size Approximately 250mm internal bore


Stantec memo, April 2018, Te Anau Pipeline Air Management. Minimum Velocity Required to Transport Air Pockets Along Horizontal and Downslope Sections’

Matters remaining Selection of pipe material (PE or PVC) Exact physical alignment Third party approvals (NZTA, landowner, consenting for stream

crossings)

Key Risks Cost, if topography and corridor owners more demanding Damage, eg by excavators

Mitigation of Risks Proposed: Develop detailed alignment Use resilient materials, Incorporate ability to isolate and drain sections. Additional storage at ponds

Other:

Further Comment The Preliminary Hydraulic Design Report (Stantec December 2018) outlines the transfer pipeline requirements in detail, and identifies that there are solutions and readily available materials meet the requirements. The Stantec memo on Air Travel Management indicates that flushing flows of at least 1.0m/s (ie full flow) lasting for 1-4 hours will be required to ensure that air pockets are moved positively along the pipeline to the next air valve.


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7.10 Air Valves and Odour Filters Table 7-11: Summary Process Element – Air valves and Odour Filters


PFD Element ID 10

Description Air valves and odour filters

Purpose Air valves allow entrained air and gas in pipeline to escape to prevent build-up of an air pocket obstruction. Also allow draining and filling of pipe, and in some locations can protect pipe against negative surge pressures

Odour filters on air valves remove odour as contaminants where treated wastewater has become septic in pipeline


Size Varies but 50mm normally sufficient Located no further than 1km apart

Fit for Purpose evidence Stantec report: Te Anau Treated Wastewater Transmission Pipeline – Preliminary Hydraulic Design, December 2017 Stantec memo, April 2018, detailing requirements to transfer air along a pipeline (to be completed)

Matters remaining Confirming the number and location of airvalves Assessment of sulphate loading. Odour filter design normally undertaken by odour filter supplier,

based a performance specification Finalise requirements for scouring of air from pipe, especially in

downhill sections

Key Risks Undulating pipe requires a high number of airvalves, especially if wastewater flow velocities are low Pipe not kept full, increasing volume of air discharges

Mitigation of Risks Proposed: Keep pipeline to minimum practical diameter to keep flow

velocities higher Include high flow-rate flush periods in operational regime Ensure infrastructure at each end of pipeline can cater for long

duration flushing flows

Other: Provision of infrastructure to pig the pipeline Provision of manual bleed valves on pipeline to assist re-filling

after a maintenance

Further Comment The Preliminary Hydraulic Design Report outlines the transfer pipeline air valve requirements in detail, and identifies that there are solutions and readily available components to meet the requirements. The Stantec memo, April 2018, detailing requirements to transfer air along a pipeline (to be completed), determines the requirements for velocities and durations of flushing flows to move air along a pipeline (especially downhill gradients). It also details air release requirements for refilling a pipeline.


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7.11 Pump-out Drain Points Table 7-12: Summary Process Element – Pump-out drain points


PFD Element ID 11

Description Chambers to drain pipeline into

Purpose Prevent uncontrolled discharges when draining pipeline. Discharges into chambers are pumped to a truck and returned to Te Anau ponds

Minimise discharge from a pipe breakage, as mainline isolation valves included at each drain point

Reduce the time/difficulty of refilling and re-commissioning the pipeline


Size 2m diameter (tbc) manhole chamber Nominal installation every kilometre

Fit for Purpose evidence These isolation points and pump-out chambers were part of the proposed scheme described in the Kepler discharge consent application, although not strictly part of the consent

Matters remaining Confirm sizing so pumping out can be reasonably matched to inflow

Confirm exact locations

Key Risks No major risks

Mitigation of Risks Proposed: Other:

Further Comment Pump out drain points have not always historically been included in wastewater pipelines, but are included in this project to better manage environment effects and provide more operational flexibility.


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7.12 Control Valve Table 7-13: Summary Process Element – Control Valve


PFD Element ID 12

Description Control valve arrangement at Kepler end of Transfer Pipeline

Purpose Keeps the pipeline full. This controls odour effects, and allows much greater control over stopping and starting the flow in the pipe


Size 200mm


Matters remaining Detailed design of valve is important to achieved accurate control over the range of flows.

Key Risks Valve failure, allowing transfer pipeline to drain Valve failure, causing overpressure in pipeline and reduced/no flow

Mitigation of Risks Proposed: Refer section 9 of Hydraulic Design report. Include a pressure relief valve and a guard valve to positively isolate the pipe Other:

Further Comment The principal purpose of this valve is to keep the Transfer Pipeline full. If the pipe partially drains then it time-consuming to refill, leading to lower and unstable flows. Additionally, the air that would be introduced and expelled requires odour treatment. For this reason, the pipeline design will include careful flow and pressure monitoring of the performance of this valve, and a separate automated ‘guard’ valve to manually isolate the pipeline if necessary.

If the pressure release valve is actuated, then consideration is required as to where this flow will go. Potentially to the adjacent balance tank.


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7.13 Kepler Balance Tank Table 7-14: Summary Process Element – Kepler Balance Tank


PFD Element ID 31

Description Kepler Balance Tank

Purpose Even out flows between Transfer Pipeline and SDI system. SDI irrigation will be stop/start operation, whereas pipeline flows stop and start over a period of minutes

Allow storage for higher SDI flows while flushing Provides a hydraulic break from the Transfer Pipeline, which

allows lower pressures and pipe classes Simplifies pumping and control of Transfer Pipeline


Size 100m3, based on a minimum calculated requirement of 69m3 and the economies of having the same size as the Pump Station balance tank

Fit for Purpose evidence No specific report done regarding size. However a preliminary calculation of minimum volume is given below

Routine stopping and starting of system proposed in s15.3 of Stantec report: Te Anau Treated Wastewater Transmission Pipeline – Preliminary Hydraulic Design, December 2017

Matters remaining Finalising size, with more detailed analysis of factors affecting volume, balancing smaller size (cheaper) vs operational flexibility (larger, most expensive)

Consideration of whether a balance tank can be omitted by the SDI pump station being designed as an online booster pumpstation

Key Risks Undersized, making control of pumping to Kepler more difficult

Mitigation of Risks Proposed: Design site layout to allow easy installation of an additional tank Allow for factor of safety on minimum theoretical size

Other:

Further Comment Reference is made to the Stantec report: Te Anau Treated Wastewater Transmission Pipeline – Preliminary Hydraulic Design. s11.6.1 gives:

570 seconds to ramp pump flow from 0 to 52 L/s (gives 15m3/s at average flow of 26 L/s) 300s from max flow to zero flow (gives 8m3 at average flow).

The following calculation is to be properly confirmed, but initial sizing, based on an assumed 5m diameter tank is shown below, and assumes the balance tank will need the following volumes.


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Table 7-15: Kepler Balance Tank initial sizing (tbc)

Storage Element Volume (m3)

Minimum submergence from inlet invert to floor of tank. Assume 300mm 6

Minimum submergence over outlet pipe invert. Assume 1m 20

Low level alarm volume between minimum submergence and min operating level. Assume based on 2 minutes to react to and stop flow to SDI field.

6

Operating volume. Assume 2 x the 570s time to ramp the pipe flow up to full flow.

30

Volume above operating volume to allow time for high level alarm to work. Assume based on taking 2 minutes to stop flow from membrane plant at 52 L/s.

3

Freeboard to overflow (200mm) 4

Head over overflow invert to drive 52 L/s (assumed at 500mm) 10

Total minimum storage 69m3

Opportunity for Excluding Kepler Balance Tank Peter Riddell (Ecogent Ltd) suggested in an email of 11 April 2018 that the balance tank could be excluded from the scope of work, at least initially when average flows are lower. The proposal is that the SDI pumps are inline booster pumps. Booster pumping avoids excessive pressures in the Transfer Pipeline, and a subsequent need to increase the pressure rating of this pipe (expensive). At this stage, it is considered that direct booster pumping should remain in consideration as an opportunity to be explored during detailed design, if SDI is the selected option. The reasons for not selecting it as the default option are as follows.

The Preliminary Hydraulic Design for the Transfer Pipeline showed that Transfer Pipeline flows require careful control to limit pressure and keep the pipe full. A central assumption in that hydraulic design is that there is a free discharge after the control valve.

It is not clear, without further investigation, that online booster pumping could be readily included without adding undue complexity, especially given the booster pumps would be downstream of a pressure control valve, so these pumps don’t see true upstream pressure.

Stopping and starting of the SDI pumps could confuse the management of the control valve that is essential to keep the pipeline full.


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7.14 Kepler Balance Tank Odour Filter Table 7-16: Summary Process Element – Kepler Balance Tank Odour Filter


PFD Element ID 32

Description Fan and odour filter for balance tank air vent

Purpose To control odourous air vented out of balance tank as level changes


Size Tbc. Could be a soil filter or carbon filter, analysis not yet done

Fit for Purpose evidence Tbc

Matters remaining

Key Risks Undersized, causing release of odour.

Mitigation of Risks Proposed: Formal design of filter, assessing air volumes and concentrations of odourous compounds Other:

Further Comment A sealed tank and fan are required to ensure tank vents positively through odour filter, and no other path.


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7.15 SDI Pump Station Table 7-17: Summary Process Element – SDI pump station


PFD Element ID 33

Description SDI pump station

Purpose Pump station to supply SDI field and flushing flows


Size Tbc. Preliminary size is 52 L/s for irrigation flow + 6L/s for flushing flow Potentially, at least 50% turndown of flow depending on how SDI field zoning is configured Assume duty/standby arrangement Operating head tbc, but 35 -50m expected

Fit for Purpose evidence Operating head indication provided in P Riddell (Ecogent Ltd) email of 11 April 2018 to Stantec

Matters remaining Hydraulic design of SDI field to confirm operating flows and pressures

Key Risks Pumpstation considered conventional, key risks lie in properly defining the requirements for the downstream components and their potential changes over time

Mechanical or electrical failure

Mitigation of Risks Proposed: Ensure full range of operational flows and pressures for SDI field

and filters are defined before selecting pumps Duty/standby or redundancy in key equipment items, including

generator plug-in point. Other: None



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7.16 SDI Irrigation Filtration and Flush Filtration Table 7-18: Summary Process Element – SDI Irrigation Filtration and Flush Filtration


PFD Element ID 34

Description Filtration of: Feedwater to the SDI field Flush Water from the SDI field Backwash storage tank

Purpose Protect the SDI irrigation driplines, emitters or surrounding soil being fouled by biofilm sloughed from the transfer pipeline


Size Preliminary SDI Feed Filter sizing based on duty/standby x 4,500m3/day

Screen pore size 120micron max Flush Filter: single filter, sized for 2 x max flow (2 x 3.5 L/s) Backwash storage tank size tbc, but 30m3 assumed for budget

purposes. Size so that emptying frequency is no less than weekly

Fit for Purpose evidence SDI Feed Filter: Sizing of 2 x 4,500m3/day filters indication provided in P Riddell (Ecogent Ltd) email of 11 April 2018 to Stantec. 120 micron

Matters remaining Predicting peak filter load requirements, eg from a pipeline sloughing event

Confirming appropriate screen aperture size

Key Risks Corrosion from septic wastewater Blockage from a pipeline sloughing event Screen pore size too coarse Backwash holding tank undersized, restricting filtering capacity

Mitigation of Risks Proposed: Stainless steel or plastic components Duty/standby arrangement for SDI filters Chemical dosing to control biofilm in pipeline Literature research on nature and likely loading from biofilm

sloughing. Noting mitigating effect of membrane plant. Other: Disposal of flush water to soakage pit, removes need for flush filter and backwash holding tank. Would require a resource consent

Further Comment Backwash holding tank: it is assumed that there is sufficient residual pressure in the backwash discharge to allow an above ground holding tank. For the SDI feed filter both Waterforce and Ecogent have proposed automatic backwashing filters of approx. 120micron. These have similar capital cost. This Basis of Design assumes the backwash holding tank is cleared by sucker truck and discharged at the Te Anau Ponds. Detailed design should look at the value of adding a settling tank for the flush water, to allow only decanted flush water to be returned to the balance tank.


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Opportunity to Eliminate the Flush Filter and Backwash Holding Tank An SDI scheme will require consent amendments. There may be efficiencies and risk reduction if flush water is consented to discharge to land, instead of being recycled because:

Simpler operation Less backwash water to be disposed of Less risk of flush debris being recycled.

This option is likely to be cost neutral, as soakpits will replace filters. If SDI is pursued, then it is recommended to explore this option.


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7.17 SDI Biofilm Dosing Table 7-19: Summary Process Element – SDI Biofilm Dosing


PFD Element ID 35

Description SDI Biofilm dosing via hypochlorous acid or similar.

Purpose Biofilm (slime) control in drip lines and control valves.


Size tbc

Fit for Purpose evidence Ecogent documented trial of hypochlorous acid at Omaha.

Matters remaining Confirm which chemical to dose Confirm dosing regime/frequency

Key Risks Inaccurate dose control leading to poor biofilm control or effect on pasture.

Mitigation of Risks Proposed: Use of driplines that include a smooth bore and antimicrobial

linings to minimise biofilm adherence. Commissioning and operational procedures to determine and

control dosing. Other: None



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7.18 Subsurface Drip Irrigation Table 7-20: Summary Process Element – SDI


PFD Element ID 36, 37

Description SDI disposal field

Purpose Subsurface irrigation of wastewater, and management of odour risk

Required for Centre Pivot or SDI SDI only

Size Stage 1, 3,600m3/day. 6 zones, each 7.5 Hectares. Stage 2, 4,500m3/day. 2 further equivalent sized zones

Fit for Purpose evidence MWH NTC 29 Aqualinc Hydrus modelling 2017 – dripper flow and spacing Aqualinc Hydrus comparison, July 2018 report, comparing CPI

and SDI MWH NTC 32 of 7 December 2016, Average Flows and Loads.

This compares N loads for CPI vs SDI

Matters remaining Final confirmation of the Hydrus modelling required, confirming 2L/dripper/hr on a 1.0m x 0.8m grid is a reasonable optimum to limit nitrogen leaching to 32kg/ha/yr over full area of North Block.

A full nitrogen model for the site, for a consent AEE, as the Overseer model does not include a subsurface module

Sue Bennett (Stantec) to prepare a memo confirming the filterable N quantities predicted by NTC 32

Final confirmation of dripper flow rate and spacing Consenting, especially if daily discharge rate exceeds the

presently consented 6.5mm per day (summer) Case studies, or other proof, of effective environmentally

acceptable herbicides to control root intrusion

Key Risks Nitrogen removal requires more irrigation area than assumed. Consentability under proposed Southland Water and Land Plan Root intrusion – loss of flow rate capacity per irrigation zone Lack of comparable projects in NZ of similar scale. Introduces

risks of ‘we don’t know what we don’t know’, and less available design expertise

Significant delay to project in order to resolve issues Machine damage to soil or infrastructure, eg from cut and carry

operation. Hydrus modelling of nitrogen removal has been problematic. Stoney soil damages or affects the driplines

Mitigation of Risks Proposed: Further Hydrus modelling to confirm nitrogen uptake to give a

scientific basis for consenting Peer review of Hydrus model Research on suitable herbicides Early discussion with Environment Southland on evidence

requirements for a consent amendment Deadline set, to limit allowable time to resolve issues. Keep the centre-pivot option live, until SDI consented


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Attribute Description Install drip lines with emitters with a higher than minimum flow

rate, to cater for some loss of hydraulic performance over time Buffer storage at Kepler to cater for differences between

pipeline flow and different ‘irrigation’ flow Loss of flow rate capacity per zone ultimately requires two zones

to irrigate simultaneously for an ‘overlap’ period. Pumps, pipes and buffer storage to be sized accordingly

Pasture management plan to control damage to soil and infrastructure

Review of soil information with a dripline supplier, and potentially a site visit with them for field tests.

Test pit programme to confirm extent of stoney ground. Other: Potentially, an additional 7.5Ha zone during stage 1 to allow for

loss of hydraulic performance

Initial Daily Flow of 3,600m3/day The maximum flow expected in initial stage of development is 3,600 m3/day (through to 2029 as detailed in MWH NTC 29 dated 4 November 2016). It is assumed that this maximum flow is irrigated continually throughout a 24 hour period at a constant rate. Will still need to have the ability to deliver the maximum flow to flush the Transfer Pipeline. This can be achieved with SDI, but at a higher application rate or to more zones simultaneously if the area has been reduced.

Dripline Layout and Flows High levels of nitrogen removal are essential to comply with consent conditions. Aqualinc Ltd were commissioned by SDC to model an SDI system, using the ‘Hydrus’ modelling software. Their brief was to determine the configuration of a SDI layout that would achieve the required nitrogen uptake. Based on MWH NTC 32 modelling assumed that there was an upstream membrane filtration plant that removed 20% of the nitrogen. A draft memorandum was issued on 12 April 2017 confirming the parameters below:

The optimal dose rate for each emitter is 2L/hour at a depth of 20cm (page 2 Aqualinc memorandum) Each emitter is capable of dosing 8L in a 4 hour pulse each day (page 2 Aqualinc memorandum) Dripper lines should be spaced at 1.0m centres (page 2 Aqualinc memorandum) Emitters should be spaced 0.8m apart (page 2 Aqualinc memorandum) Irrigation zone modelled on flow being pulsed then rested in a ratio 4 hours on, 20 hours rest (page 2

Aqualinc memorandum). Further modelling showed that soil moisture distribution improved by enhancing this dosing to 1 hour on, 5 hours rest.

Emitter Flow Rate A 2L/hr flow rate from emitters on a 0.8m2 grid gives 2.5mm depth of irrigation per hour. The consented daily maximum of 6.5mm (ie 6.5 litres per m2) occurs in 2.6 hours. This provides flexibility to:

Provide lower rate drippers if desired, with expected improvements in moisture/solute distribution, or Pursue a consent with higher permitted daily depths of discharge, or Provide a safety margin to account for loss of hydraulic performance over time. Eg; daily zone

volume achieved in 4hrs vs (say) 2.6hrs, noting that instantaneous irrigation rate per zone would drop below the design 52 L/s.

Minimum SDI Field Area – Stage 1 The existing discharge consent limits the rate of irrigation via centre pivot irrigation to 6.5mm per day for a maximum daily volume of 4,500m3/day. This gives an area of 69.2 Hectares. To calculate the area of an SDI field, the following assumptions are made:


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If a lesser daily volume is irrigated initially, then the disposal field can be reduced accordingly, and it is felt that this is an argument that the consent authority would accept

If the nitrogen concentration in the wastewater is reduced, (in this case by a membrane plant), then the irrigation field size can be reduced proportionally (so that the kg of N/Hectare remains unchanged). This assumes: That modelling (eg Hydrus) can prove to the consenting authorities’ satisfaction that the extra

depth of irrigation does not increase wastewater drainage, especially in the critical shoulder seasons. Hydrus modelling supports this.

That the new requirements of ES’s Proposed Water and Land Plan have not raised the minimum standard.

Therefore using:

An initial max daily flow of 3,600m3/day, the area reduces to 55.4Ha A nitrogen reduction due to a MF plant of 20% (refer MWH NTC 32) reduces the initial SDI field size

to 44.3Ha.

Further reduction of SDI field area.

To further reduce the size of the SDI field, two further arguments could be used:

That SDI produces greater pasture/dry matter, and therefore more nitrogen removal. Therefore a proportionate reduction of the field size could be argued. This assumes again that the further depth of irrigation doesn’t cause more drainage to groundwater. However reducing the wetted area under irrigation may be offset by lower baleage production (hence N removal) off the consented 120Ha. There is presently no evidence to support this argument, and Tony Davoren, Aqualinc noted in an email of 26 July 2018 to R Oakley that “Of all irrigation systems, linear move irrigators give highest yields”.

That further refinement of the modelling of N uptake could show that even with more concentrated disposal, the scheme could stay within the 32kgN/Ha/year limit. Note that this is not suggesting higher hydraulic and N loadings produce proportionately more pasture dry matter. It is only suggesting more sophisticated modelling could reduce the margin of error in predictions to demonstrate a higher N loading could stay within consent limits. Aqualinc, using Hydrus modelling, compared the performance of CPI and SDI with regard to N removal. This is summarised in their July 2018 report ‘Te Anau Wastewater Upgrade: SDI vs CPI comparison’. This showed that, with regard to N, an area of 37Ha under SDI would achieve similar performance to the consented 70Ha under CPI (table 4 of that report). However this requires significantly higher hydraulic loading. As discussed below, increased hydraulic loading, above the 20% already proposed, is not considered acceptable. Operational experience will be required to gain further certainty.

Irrigation field size particularly depends on the performance of two key factors, nitrogen removal, and avoiding the risk of daylighting during wet weather events (hydraulic performance). With regard to daylighting, further reducing the field size will increase the application depth, increasing this risk. The proposed Additional Storage for SDI is less than for CPI, to give comparable risk of daylighting/runoff in severe weather events. Discussion with Aqualinc confirms that further increasing the SDI hydraulic loading will commensurably increase the likelihood of daylighting occurrences. Therefore, for hydraulic reasons, a further reduction in area is not proposed. In discussion of the last bullet point, increasing the N loading per Hectare, above the currently consented rate, may prove difficult to consent, even if more accurate models show that the 32kgN/Ha/year leaching limit can be achieved. This is because in gaining the existing consent it was recognised that there were inherent factors of safety in the predictions, and the consenting authority may feel they ‘own’ this safety margin. Therefore, the minimum area for the first stage of an SDI field is 44.3Ha, on the assumption that the consenting authority accepts the above ‘scaling’ arguments.


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Minimum SDI Field Area – Stage 2 Stage 2 is assumed to provide for the full consented flow of 4,500m3/day. Using the same basis as for stage 1, an SDI field can be 20% smaller than a centre pivot operation running at 6.5mm/day, due to the nitrogen removed by the membrane filter. This reduces 69.2Ha to 55.4Ha.

Layout Options for SDI Fields Appendix F gives three potential layouts of irrigation zones and flush zones that could fit comfortably on the site, with reasonable options to add additional further area in the future. The options illustrate the evolution of thought on an optimum layout. Key differences are:

Options 1 and 2 assume all flow goes to a single zone at a time Option 1 assumes a binary on/off of full 100% design flow goes to a single zone at a time Option 2 allows for partial flows in 25% increments for a zone Option 3 abandons the idea of 6-8 dedicated zones, and simply creates 24 – 32 smaller zones, each

capable of accepting 25% of the flow. Irrigation could be to any combination of these zones, and they are sized to be an appropriate size for flushing.

Key attributes for design are:

Each zone must be the same area, to have the same flowrate There must be a practical layout of the zones on the site Longer dripline runs tend to decrease the amount (and cost) of trunkmain pipework that feeds the zones More zones can be added in the future, to increase irrigation capacity Each zone for Options 1 and 2 are 7.5Ha Dripper lines will be at 1.0m spacing, with emitters on each line at 0.8m spacing, as per the Hydrus

modelling Each zone includes pipework and valves to enable flushing to remove accumulated particles Flush water will be passed through a filter and returned to the inlet balance tank All inlet and flush valves for each zone will be in a chamber (which will be mowed around), and will

have power and control cables Flushing should be able to be undertaken in a zone that takes no more than 25% of the irrigation design

flow (ie 52 L/s) Pumping and hydraulic design will assume a flushing flow velocity of 0.4m/s (minimum) at the outlet end

of the dripper lines.

Discussion of Layout Options Option One is configured so that all flow goes to a single zone. This requires a single inlet valve, and full capacity inlet mains. Dripper lines would be 17mm, and there would be five flush subzones. This option minimises the dripper line diameter, the length of physical pipework, and the number of valves, but comes at the expense of supply mains and valves being larger, and no capacity to operate at partial flows. Flush flows will add a requirement for an additional 6 L/s. Option Two is configured so that each zone, and the whole scheme, can be operated in fields of 25% flow increments. This gives greater control over flow rate, and means supply mains and valves can be smaller. Dripper line runs are longer, requiring an increase in diameter to 20mm, but less connections to supply and flush mains. To achieve full flow of 52 L/s, four fields, each in a different zone, would be employed, as supply mains to a zone would not be sized to feed all four of its fields at the same time. Option 3 is a further refinement that requires the least amount of infrastructure and provides the most flexibility. The project cost estimates for an SDI scheme are based on Option 3.

Winter and Lower Flows Lower daily flows, including when limited during winter, would be achieved by shorter duration doses to each zone, with no dosing happening at all for periods during the day.


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Higher Future Flows An advantage of SDI is that is that hydraulic capacity to dispose of flow rates much higher than the design inflow. This is because dosing in pulses in the ration 1:6 dose:rest. Therefore, higher future flows could be achieved by:

Irrigating to additional zones at a time (effectively reducing the 1:6 dose ratio). This would require the upsizing of the trunk mains, pumps and filters in the field. This may be possible if monitoring shows the environmental effects are less than predicted.

Combined with the above, constructing more zones, depending on consenting requirements. Higher future flows require knowledge that N effects are acceptable, and that the hydraulic loading on the soil does not cause unacceptable effects with saturation (hydraulic capacity). Operational experience will be the best source of information as to what extent hydraulic loading can be increased.

Minimum Zone Area – Layout Options 1 and 2 This is calculated using the maximum instantaneous flow, and the optimal dose rate for each emitter. For this calculation the maximum instantaneous flow was adopted as 52l/s. This value was used to ensure the subsoil irrigation system was capable of disposing the maximum daily flow of 4,500m3/day expected at the end of the consent period in 2048. This is required because subsoil drip irrigation systems cannot be reconfigured once installed. Therefore, in order to future proof the system each irrigation zone is required to be sized to discharge the instantaneous flow expected in final stage of design (4,500m3/day in 2048). As the subsoil drip irrigation is a staged installation process capacity would be increased by the addition of extra irrigation zones rather than altering irrigation zone sizes. The optimal dose rate for each emitter is 2L/hour as mentioned previously, with Hydrus modelling recommending drippers on a 1.0m x 0.8m grid. These parameters are used to produce a minimum irrigation zone area of 7.5 ha/zone at 52 l/s. The calculations performed to obtain this value is shown below. To discuss sensitivity:

Zones smaller than 7.5Ha will not accept 52L/s Therefore, if there are smaller zones, then multiple zones will need to be operated simultaneously, sized

to give a combined flow of 52L/s. The next logical size down would be 3.75Ha, half of the 7.5Ha minimum size

Zones larger than 7.5Ha would require emitters to be either slower rate, or at a larger spacing. Emitters operate at a single flow rate, not variable.


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Maximum Zone Area – Layout Options 1 and 2 The assumptions for maximum required zone sizing are:

The maximum daily depth of irrigation is 6.5mm as per the current resource consent This must be achieved within 4 hours per day, the maximum dose time identified in the Hydrus modelling.

This gives a maximum zone size of 11.5Ha. The equation is: 6.5mm depth = 6.5 litres/m2 in 4 hours = 1.625L/m2/hour, or 0.00045L/m2/s. Therefore, the zone area for 52L/s = 52/0.00045 = 115,200m2.

Minimum of Six Zones – Layout Options 1 and 2 The SDI system is required to have irrigation zones that can be pulsed and rested to allow nitrogen uptake and soil moisture levels to even out. The optimal pulse to rest ratio is 4:20 as previously outlined. Each zone is able to be pulsed for a period of 4 hours as determined in the report by Aqualinc. It follows that six zones will be required as a minimum to achieve the required pulsing ratio.

Minimum Required Number of Zones Layout Options 1 and 2 The minimum number of zones is:

Stage Daily Flow m3/day

Irrigation Area Ha

Zone size Ha

Number of Zones

SDI field size Ha

One 3,600 44.3 7.5 6 45

Two 4,500 55.4 7.5 8 60


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7.19 Root Intrusion Control Table 7-21: Summary Process Element – Root Intrusion Control


PFD Element ID 38

Description Root Intrusion Control via via sustained release herbicide impregnation

Purpose Prevention of root intrusion into subsurface emitters.


Size n/a, it is a substance impregnated into the dripline liners

Fit for Purpose evidence Control of root intrusion is a fundamental requirement of and SDI field.

Refer Aqualinc memo of 9 April 2018 proposing pendimethalin.

Matters remaining Historically, the Trifluralin (Treflan) product was impregnated into drip lines. Due to environmental/toxicity concerns, it is unlikely to be an option. Banned in the EU since 2008

Refer Aqualinc memo of 9 April 2018 providing update on Treflan use and proposing pendimethalin instead.

Key Risks Pendimethalin’s registration for use in NZ still be confirmed. This is a major hurdle, root intrusion must be confidently controlled

Obtaining a resource consent for any herbicide used Effect on ‘in-soil’ bacteria (eg nitrifiers/denitrifiers)

Mitigation of Risks Proposed: Confirm status of pendimethalin approval. Alternatively, undertake environmental impact assessment of

Treflan and gain a consent for it Seek confirmation of herbicide effect on in-soil bacteria. Other: Set aside financial allowance for shorter life of SDI field due to root intrusion.

Further Comment Ben Stratford, peer reviewer, cautions that full confirmation of acceptability of the root intrusion control chemical remains a major risk, and further expertise should be sought.


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7.20 Subsurface Drip Irrigation Flushing Table 7-22: Summary Process Element – SDI Flushing


PFD Element ID 39

Description SDI pipe flushing

Purpose Flushing of sediment and biofilm from SDI irrigation pipework

Required for Centre Pivot or SDI SDI only

Size 3.5 L/s, based on 0.4m/s velocity at end of 17mm dripper line 100mm diameter flush mains indicated, based on general

principle of limiting flow velocity to 1m/s

Fit for Purpose evidence Refer email I McIndoe (Aqualinc, 12 Dec 2017)

Matters remaining Duration of flush tbc, but approx. 15 minutes per flush zone, every fortnight Confirmation of flush velocity, and hence flow. 0.4m/s may be able to be reduced. Full hydraulic design (software packages exist for this)

Key Risks Odour from air valves Clogging of flush-return filter

Mitigation of Risks Proposed: Obtain a consent to discharge flush water to soakpits Accept odour risk from air valves, as short duration and

occasional. Include in consenting. Other:

Further Comment Additional flushing flows in the SDI dripper lines are occasionally required. The subsoil irrigation system is required to be capable of achieving minimum flushing velocities in the range of 0.3-0.4 m/s at the far end of each dripper line (email correspondence with John Wicken, Waterforce sales engineer). These velocities are required to remove sediment and algae build up. Flushing occurs while irrigating a zone. To limit the instantaneous flow to a zone, (and accompanying upsizing of infrastructure), it is proposed to provide the facility to sequentially flush 20% of an irrigation zone at a time. Refer Appendix F for layout options. With this approach, each flushing zone likely to have 66 x 17mm dripper lines, giving a flushing flow of 6 l/s. Ian McIndoe (Aqualinc Ltd), email, 12 December 2017, also confirmed flushing flows should achieve velocities of 0.3 to 0.4m/s, but it is assumed this would need to be confirmed for a specific layout. Other parameters are:

Flush for enough time to replace the volume of water in the driplines, the flushing submain and the feeder submain

In practice, inspect the flush water to see how long it needs to flush to clear, but the above is a starting point

Initially flush every two weeks, check the quality of flush water and extend the time out if it stays relatively clean.


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8. Specific Process Elements – CPI This section describes in further detail those elements that are specific to the Centre Pivot Irrigation. Refer to the preliminary Process Flow Diagram (PFD) (Appendix A), that highlights the key process elements for both a Centre Pivot option and an SDI option.

8.1 Trickling Filter and Irrigation Pumpwells Table 8-1: Summary Process Element – TF Pumpwells and Balance Tank


PFD Element ID 21 and 24

Description Arrival pumpwell for Trickling Filter, in a combined structure with the pumpwell for the centre pivot irrigation pumps. Irrigation pumpwell incorporates 100m3 balance storage (similar to item 31 for SDI).

Purpose Arrival pumpwell allows ww to recirculate around trickling filter, whether or not there is a inflow from the ponds, or an outflow to irrigation. This keeps TF media wet and biofilm healthy.

Irrigation pumpwell is to pump to the irrigators the overflow ww from the arrival pumpwell to the irrigators. This is the pumpwell that would have the balance storage.

All chambers are connected via overflow weirs. 100m3 balance storage is to: Even out flows between Transfer Pipeline and CPI system. CPI

irrigation will be stop/start operation(in a matter of seconds), whereas pipeline flows stop and start over a period of minutes.

Allows Transfer pipeline to briefly run at higher flushing flows without adjusting irrigation rates.

Simplifies pumping and control of Transfer Pipeline.

Required for Centre Pivot or SDI CPI

Size Recirculation and irrigation pumps – capability for full potential flow of Te Anau pumpstation. This will exceed the design flow (52 L/s+5%), depending on Transfer Pipeline pipe roughness and actual pump specification.

Irrigation pumps – as above. Recirc pumpwell volume – not sized yet. Balance tank (aka irrigation pumpwell volume), in the order of

100m3, initial sizing calc as per SDI arrival balance tank (PFD item 31).

Fit for Purpose evidence Refer to 2014 MWH report ‘Te Anau Trickling Filter Odour Control Modelling’ for general description of need for Trickling Filter pumpstation and sizing.

Balance Tank: initial sizing calc as per SDI arrival balance tank (PFD item 31).

A lesser balance volume may be possible, refer to s12 (irrigation Supply Chamber Sizing) in the Stantec report: Te Anau Treated Wastewater Transmission Pipeline – Preliminary Hydraulic Design, December 2017.

Routine stopping and starting of system proposed in s15.3 of Stantec report: Te Anau Treated Wastewater Transmission Pipeline – Preliminary Hydraulic Design, December 2017.

Matters remaining Final sizing and physical configuration.


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Attribute Description Confirm location, presently assumed to be on the northern

boundary, between the two western irrigators.

Key Risks Undersized balance tank, making control of pumping to Kepler more difficult.

Mechanical or electrical failure of key components Corrosion from H2S.

Undersized balance volume, making control of pumping to Kepler more difficult.

Undersized recirculation pumpwell, making pump control unduly complex.

Mitigation of Risks Proposed: Allow for factor of safety on minimum theoretical size.

Duty/standby or redundancy in key equipment items, including generator plug-in point.

Fully develop the operational logic to ensure pumpwell sizing is correct.

Ensure manual control possible.

PVC lining of pumpwell, and/or non-corrosive materials.

Other: Additional balance tank volume.



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8.2 Trickling Filter Table 8-2: Summary Process Element – Trickling Filter


PFD Element ID 22

Description Trickling filter.

Purpose Odour control. Removal of odorous compounds.


Size 300-400m3

Fit for Purpose evidence Refer to 2014 MWH report ‘Te Anau Trickling Filter Odour Control Modelling’.

Matters remaining Final sizing

Key Risks Mechanical failure. Undersized, affecting odour performance and biofilm growth. H2S corrosion. Biofilm dieback during shutdown.

Mitigation of Risks Proposed: Redundancy of key components. Distributor arm directly procured from proven specialist provider,

as it is the key mechanical and process item. Use of corrosion proof materials. Addition of downstream oxidant dosing as redundancy in case

of loss of odour treatment performance. Ensuring pumpwell size sufficient to maintain performance of

trickling filter when not irrigating. Other: Increased spray droplet size at irrigators (up to 3,200micron

VMD), to reduce odour risk. Use of Low Energy Spray Application (LESA) nozzles and

configuration at the irrigators to minimise risk of spray drift and control droplet size.



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8.3 Soil Odour Filter Table 8-3: Summary Process Element – Soil Odour Filter


PFD Element ID 23

Description Soil odour filter

Purpose Treat odour from off-gas air positively ventilated from trickling filter and pump wells.


Size Preliminary sizing: 2,300m3/hr, 30m2.

Assume an above ground soil filter 1.5m deep and 6m x 5m. Fit for Purpose evidence Refer s5 of 2014 MWH report ‘Te Anau Trickling Filter Odour Control

Modelling’.

Matters remaining Sizing of odour bed.

Key Risks Drying out of filter bed. Undersized. Flooding. Mechanical failure.

Mitigation of Risks Proposed: Dedicated system to irrigate filter beds. Conservative sizing, to allow maintenance of zones of the filter

bed. Build above ground. Redundancy of key mechanical components (mainly the

ventilation fan attached to the TF). Other:



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8.4 Hypochlorite Dosing Table 8-4: Summary Process Element – Hypochlorite Dosing


PFD Element ID 25

Description Online oxidant dosing

Purpose ‘Mop up’ any H2S that is not stripped by Trickling Filter.


Size S4 of 2014 MWH report ‘Te Anau Trickling Filter Odour Control Modelling’ suggests no more than a 1,000 litre Intermediate Bulk Container (IBC) will be required.

Above report (s4.1) details potential range of dose rates from 2.5 – 6.1mg/l of 10% NaOCl solution. This equates to 62 – 152 litres per month.

Fit for Purpose evidence S4 of 2014 MWH report ‘Te Anau Trickling Filter Odour Control Modelling’.

Matters remaining Final sizing Method of measuring H2S in the wastewater.

Key Risks Inadequate online control of dose.

Mitigation of Risks Proposed: Investigate use of online H2S measurement in wastewater. Other:



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8.5 Centre Pivot Irrigators Table 8-5: Summary Process Element – Centre Pivot Irrigators


PFD Element ID 26

Description Centre pivot irrigators

Purpose Evenly distributed irrigation of treated wastewater onto land


Size 3 or 4 irrigators capable of 52 L/s flow, plus any additional flow above this design level that the infrastructure is physically capable of. Note that the original consent application was based on two bigger irrigators.

70Ha irrigated area at 4,500m3/day design flow. Potentially, only installing 80% of daily irrigation area until

demand increases. Note 100% of instantaneous rate will be required for Transfer Pipeline flushing.

Fit for Purpose evidence Refer to AEE for discharge consent to Kepler.

Aqualinc report, August 2018 ‘Storage Requirements and Frequency of Storage Volumes for Te Anau WW’, that details limits to irrigation in extreme rain events.

Matters remaining Determine layout of irrigators, especially around the peat bog

Key Risks Extreme weather events preventing irrigation due to wind, or especially, saturated soils.

Fouling of nozzles. Rutting of wheel tracks. Frosted ground limiting irrigation. Proper management of spray drift. Algae fouling of soil surface affecting infiltration rates.

Mitigation of Risks Proposed: Resource consent limit of 6m/s wind speed for irrigating near the

boundary Consideration of splitting the irrigator at the peat bog into two

separate irrigators (as in diagram below) Filters on pumped discharge to irrigators (refer to 2017 Stantec

Report on Preliminary Pipeline Hydraulics) Buffer storage at Te Anau ponds to enable ‘no irrigate’ days if

wind or frost issues arise. Budget allows for constructed wheel tracks in first year of

operation, and ongoing maintenance. Active pasture management Nozzles sized for large droplet size (up to 3,200micron VMD) to

eliminate spray drift and control fouling potential Other: Membrane filtration plant at Te Anau ponds to remove algae

risk Low energy spray irrigation (LESA), with low elevation nozzles to

further control spray drift potential.


Page 48

Further Comment Work in 2018 has further developed the preferred irrigator layout, as shown below. Key advantages are:

Retention of the southern shelter belt.

Avoiding the irrigators travelling over the peat bog (and associated needs for controls to stop irrigation and for wheel bridges over bog).

Flexibility and redundancy of operation from an additional irrigator.

LESA irrigation is shown in the example below:


Page 49


Page 50

9. Other Process Elements Additional to the process elements described in this Basis of Design, there are other elements:

Potable water will be required on both the Kepler and Te Anau ponds site. Eg for safety showers, soil filter irrigation. Quantities are expected to be small

Odour control will be required on the flush water holding tank and SDI flush line air/vacuum valves Power supply will be required at the Kepler site, and upgraded at the Te Anau Ponds Pasture type and management is a central element to the effective treatment of the waste water.

Careful selection of type, and ongoing management are crucial, and a management plan is a requirement of the current Kepler consent

SDI will require power and signal cables to the valves for the inlet and outlet of all the zones. This would be ringmained to limit the consequences of any damage

The hardware and software to control the infrastructure Provisions to monitor the effectiveness of the scheme and determine any degradation of

performance.


Page 51

10. Risk

10.1 Key Risks Summary for SDI This Basis of Design Statement has identified the following key risks relating to an SDI system. The project risk register tracks all risks, and it will be important to update it as necessary with the risks below.

Comparable Projects The Te Anau scheme will be significantly the largest scale SDI project in New Zealand. This is both in terms of area and flows. Knowledge can be drawn from smaller projects that have hydraulic characteristics that can be scaled (eg Tiwai Pt). However, a SDI scheme is designed for a combined performance of hydraulics and wastewater treatment especially nitrogen removal, so each scheme is unique. This introduces risks of ‘we don’t know what we don’t know’. This is a serious form of risk. Associated with the above, is that there is less available design expertise, and this has been evidenced to date by a wide range of opinions on risks, and the difficulty to date to model nitrogen leaching. Mitigation of this risk requires a more conservative design and an increased financial risk allocation.

Fouling of the Disposal Field A major, if not the major risk of an SDI scheme relates to the fouling of the disposal field by biogrowth and particulates. Fouling may particularly arise from root intrusion into the emitters, or fouling of the soil surrounding the emitters. This risk is exacerbated by recent information against the use of the Treflan herbicide. However, a replacement herbicide (pentamethalin) has been developed and appears to be gaining general acceptance. Work is still required to finally confirm a suitable herbicide is available and will achieve regulatory approval.

The fouling risk is particularly prominent because:

A fouled disposal field (or part of), is expensive to fix, as replacement of driplines may be the only option

It may take some years to manifest, making it difficult, if not impossible, for SDC to recover compensation. This means SDC may own the risk.

Mitigation of SDC’s risk (not necessarily the actual risk) could include procurement methods such as Design-Build-Operate, with a longer term ‘Operate’ period, and a financial allocation to the risk budget. This would require a contractor to accept the risk. Ben Stratford, peer reviewer, cautions that full confirmation of acceptability of the root intrusion control chemical remains a major risk, and further expertise should be sought. It is also crucial to confirm that the selected herbicide achieves necessary regulatory signoff.

Environment Southland Water and Land Plan It is expected that an SDI scheme will have to meet a higher standard than the consented CPI scheme. This is regardless of whether it can be authorised under an amendment to the CPI consent, or requires a new consent. The Proposed Southland Water and Land Plan has come into force since the CPI consent for the Kepler was granted. The standards have changed, and now includes aquifers, as well as the point of discharge to surface water. This introduces requirements around nitrogen and microbiological loadings/attenuation with regard to the aquifer. The AEE for the present CPI consent assumed that pathogens would not completely die off before the aquifer, meaning this matter will need to be readdressed. Mitigation includes keeping the CPI option live, and setting deadlines for a decision on SDI.


Page 52

Extension of Discharge Consent to Upukerora SDI will require Upukerora consent renewed for a further term, and Objectives and Policies in the Proposed Plan about discharge to surface water are tighter, for example regarding pathogens, introducing a risk of further treatment required at the pond site for the extended discharge. Advice from a range of legal and planning sources warns that gaining a consent for a further period of discharge to the Upukerora River is a far from certain process. Mitigation includes keeping the CPI option live, and setting deadlines for a decision on SDI.

Confirming Nitrogen Removal Modelling of nitrogen leaching for SDI is not yet conclusive. This introduces two risks:

The required area for SDI is different than presently assumed (higher or lower) Sufficient technical evidence is not yet available to support a consent change to SDI.

There is an immediate need for SDI nitrogen modelling that can be used as a valid comparison with the Overseer model developed for the present CPI consent. The advice received is that Overseer does not have the capability to model SDI. To address this it is proposed:

Initially, extend the existing Hydrus SDI model to do a direct comparison of nitrogen drainage between the wetted area of CPI and SDI schemes for Te Anau. This comparison would take into account that SDI has approx. 20% lower nitrogen concentration due to the MF plant. This would be combined with industry figures for a ‘per hectare’ nitrogen drainage from dryland parts of the North Kepler Block. Irrigated and dryland figure would be combined to give an average for the whole block. This comparison would provide sufficient technical evidence to finalise the wetted area of on SDI scheme

Should SDI become the preferred option from the Business Case assessment, a full nitrogen model for the whole North Block would need to be developed for a resource consent AEE.

Pathogen Removal An advantage of the surface application of centre-pivot is the improved removal of pathogens, in comparison to SDI, because they are exposed to UV (sunlight), and have a longer path to the groundwater. This would need to be addressed, but may be acceptably offset by the membrane filter. Regrowth after the membranes would need to be considered but is not an exact science.

Sludge Load from Membrane Plant The MF plant will return its backwash sludge load to the head of Pond 1. Confirmation will be required that this is an acceptable load on the ponds. Increased frequency of pond desludging can be expected, and this will need to be allowed for as an increased operational cost. Sludge character will need to be understood, sludge from different treatment processes has differing characters and treatment requirements.

Speed of Recovery SDI has the risk arising from an operational failure that takes longer to recover from than the time available. Such failure might be one that affects the membrane plant, or passes an unacceptable solids load to the disposal field. In comparison, a CPI operation is simpler and less susceptible. Mitigation includes a greater level of control and monitoring, along with redundancy of key components.

Ease of Operation An SDI/Membrane Filtration scheme will be significantly more sophisticated to operate than the existing oxidation ponds, and introduces a risk of insufficient experience and training of operators leading to an operational failure, or degradation of performance. A CPI scheme without MF will also be more sophisticated than the existing scheme, but less so, especially when considering the consequences of a failure.


Page 53

It is considered that there is a similar level of complexity SDI v CPI in operating the Kepler irrigation site. To mitigate the risks arising from errors in operation there will be a need for significant initial and ongoing training of operators. With regard to the nature of the operational risks, whilst the level of operational complexities are similar between CPI and SDI, the character of the risks differ importantly. This is with regard to both likelihood and consequence. These will need to be characterised with work, eg review of operational type failures with CPI and with SDI. To illustrate the different nature of operational risks, the consequences with SDI, as discussed above, could include system failure and complex or time consuming repairs. Mismanagement or operational limitations leading to failure of CPI could include eg over irrigation and contaminated runoff, or irrigators being blown over.

Hydrus Modelling of SDI Nitrogen Removal To date, modelling of the removal of nitrogen achieved by SDI is incomplete, and has had some issues. There is a risk that problems may continue, making it very difficult to supply the technical evidence to support an SDI consent application. To mitigate this, it is recommended that a peer review of the model is undertaken at the appropriate time.

Stoney Ground Around the Drippers Stoney ground around the driplines can cause damage to the driplines, as they are thin walled.

Mitigation can include mole-ploughing in sand around the driplines as they are installed, but this can be expensive.

To mitigate this existing soil testpit information should be forwarded to dripline providers for advice on whether this is an issue, and any further field tests required.

10.2 Opportunities Arising From SDI An SDI scheme has a range of risks and opportunities that are different from a CPI scheme. Key opportunities, or areas of lower risk for SDI are:

The form of nitrogen in SDI will typically be different due to the absence of a trickling filter for odour. SDI will have more ammonia, which is more readily held in the soil. This provides an opportunity for N removal performance to be enhanced. As quantification of this benefit is difficult, this matter is listed as an opportunity, rather than a direct benefit that allows reduced SDI irrigation area.

SDI, with MF, has a smaller footprint than CPI with no MF. This leaves more space available at the Kepler site for future expansion.

SDI is not susceptible to wind drift, or perception issues relating to aerosols. SDI more efficiently uses water for irrigation when the soil moisture is low. This increases the chance

of higher dry matter production on an annual basis. SDI can likely avoid the stand down period (say 7 days) between irrigating and cutting the pasture. SDI is less affected by the potential for surface runoff during extreme weather events. Therefore,

SDI can operate in a wider range of conditions, reducing the demand on the additional storage at the Te Anau ponds, and reducing the risk of requiring further additional storage.

The MF plant size could be reduced from peak flow to a baseload flow size if a satisfactory bypass filtering to control algae can be determined. This is on the basis that algae blinding of the soil around an emitter must be avoided. Presently, this risk of emitter fouling is considered unacceptable.

An SDI scheme has more capacity for short term hydraulic disposal of peak flows, as each irrigation zone designed for 1:6 dose:rest ratio. Actual performance will depend on installed pumps and pipe sizings.


Page 54

10.3 Opportunities for Both CPI and SDI While outside the scope of this Basis of Design, longer term opportunities are mentioned:

Experimentation of pasture type and management may well increase the ability to capture nitrogen in the cut and carry crop

Monitoring of actual environmental effects, and nitrogen leaching may provide qualitative evidence of lesser effects than presently predicted, due to assumptions that are necessarily conservative. This will provide an evidence base for future expansion and reconsenting that may demonstrate higher loadings are acceptable. This will reduce physical works for future stages

Repurposing Ponds 2 and 3 to provide Additional Storage Staged construction, to match inflow growth, to defer capex Hypochlorite dosing in the Transfer Pipeline to improve pipeline performance.

Appendices


Appendix A Draft Process Flow Diagram

Pond Outlet Screen

Purpose: Debris and algae removal,

protect pumps.

Size: Duty/standby, 78l/s. Max flow +50%

Key Risks: Partial clogging affecting

capacity

Additional Storage

Purpose: Store ww when can’t irrigate

for weather or operational reasons.

Size: 15,000m3. As per consent

Risks: undersized – pond overflows

Membrane Filter

Purpose: Solids/algae removal to protect drippers.

Also: Reduces nitrogen by 20%, removes bacteria,

some viruses.

Size: 4,500m3/day net output. 0.04 micron

Risks: Algae clogging, malfunction, power outage

MF Balance Tank (SDI)

Purpose: Flow balancing as MF

turns on and off for backwash.

Size: 100m3 (tbc)

Risks: undersized – affects pumping

Membrane Inlet Screen

Purpose: Protect membranes,

algae reduction, debris damage

Size: 104 L/s. Max flow + 100%

Risks: Algae clogging

Biofilm Control Dosing

Deleted May 2018

Transfer Pipeline

Purpose: transfer ww to Kepler

Air valve and odour filter

Purpose: Air release and surge

protection. Odour control

Size: Every 1km, max

Risks: insufficient number.

Undersized for pipe filling.

Pump Station

Purpose: Transfer ww to Kepler

Size: 52 l/s (+ 5%?), 4,500m3/day

Risks: Malfunction, power outage

Tank

MF

Pump

AV

Carbon

Pump-out drain points

Controlled emptying

Approx every 1 km

ADDITIONAL

SCOPE FOR

SUBSURFACE

DRIP IRRIGATION

20% backwash

return

DRAFT TE ANAU WW SCHEME - PROCESS FLOW DIAGRAMLast updated 27 August 2018

To Kepler1

2 3

4

576

9

8

11

27/08/2018Draft after peer review – page 2 of 2

10

Existing

Ponds

KEY:

Wastewater flow

Backwash flow

Air flow

Chemical dose

MF Peak flow bypass option

Purpose: cost saving on smaller MF Plant

3.5 L/s Flush Return – Sediment/biogrowth removalFilters

Purpose: Prevent blockage

Size: Full flow +50% (tbc)

Key Risks: Undersized

Kepler Balance Tank (SDI)

Purpose: Buffer flow differences between

transfer pipeline and irrigation. Simplify

pumping and control. Allow lower

pressure in the transfer pipeline. Stored

volume for dripper flushing flows.

Size: 100m3 = 30 min at 52 l/s max

Risks: undersized

Biofilm Dosing (SDI)

Purpose: Biofilm control

Size: n/a

Risks: Not effective - dripper blockage.

Compromises nitrogen removal.

Soil odour filter

Purpose: Odour control from TF

Size: tbc

Key Risks: Dries out, leaks odour.

Tank

PP

Pump

Centre Pivots x 3

Purpose: ww distribution

Size: 52 l/s, 4,500m3/day

Key Risks: Operation limited

during extreme weatherFan

Flush

Filter

Trickling filter

Purpose: Odour control

Size: 300 - 400m3

Risks: Mechanical or biological

failure

Subsurface Drip Irrigation

Purpose: ww distribution with little

odour risk.

Size: Stage 1: 24 zones, 1.9Ha each,

3,600m3/day. Stage 2: extra 8 zones

Risks: Consenting under new Plan. Root

intrusion. Nitrogen removal inadequate.

Irrigation

Filters

Pumphouse (SDI)

Purpose: Pumping and controls

Size: 52 l/s + 6 l/s flush.

Risks: Malfunction, power outage

Control

valve

From

Ponds

Future

zones

Soil Odour

filter

Odour

filter

Hypochlorite dosing

Purpose: Additional odour control

Size: tbc

Key Risks: Inadequate online control

of dose.

Irrigation Pumpwell

Purpose: Irrigation pumps, and

balance storage for Te A pipeline

Size: 100m3.

Risks: undersized – affects pumping

TF

52 L/s

12

22

25

23

24

26

31

33

32

34

35 36

3739

AV AV AV AV AV AV

27/08/2018Draft after peer review – page 2 of 2

21

Fan

Backwash

tank

Air/vacuum valve

Recirc

Root Intrusion Control

Trifluralin or pendimethalin impregnationFlush

38

Centre

Pivot

Option

Sub-

surface

Option


Appendix B Chart of Pond Inflows

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Jul-10 Jan-11 Jul-11 Jan-12 Jul-12 Jan-13 Jun-13 Dec-13 Jun-14 Dec-14 Jun-15 Dec-15 Jun-16 Dec-16 Jun-17 Dec-17 Jun-18 Dec-18

Ra

infa

ll (mm

)P

on

ds

Infl

ow

(m

3/d

ay

)Te Anau Wastewater Ponds. Daily Inflow and Rainfall 2010 - 2018

(updates the previous 2010 - 13 data)

Ponds inflow from pump hours 4,500m3/day summer discharge limit 2,000m3/day winter discharge limit

Ponds inflow from magflow Rainfall (mm) 20 per. Mov. Avg. (Rainfall (mm))

Flow measurement

changed to a magflow

meter 19 Dec 2015


Appendix C NTC 29 – First Stage SDI Flows

File Reference: P_80508264/ C / C1

Page 1

NOTICE TO CLIENT

DATE 9 November 2016 CLIENT SDC Water and Waste Services

CONTRACT Te Anau Wastewater Scheme ADDRESS PO Box 903

PROJECT NO. 80508264-C-C1 INVERCARGILL

CONSECUTIVE NO. 29 ATTENTION: Ian Evans P:\_2012 Onwards\Southland District Council\80508264 Te Anau WWTP\C - Client Correspondence\C1 - Notices to Clients\NTClient

29 Design Statement SDI flows\NTClient 29 Design Statement - SDI flows.docx

TE ANAU WW SCHEME Update of inflow data Basis of design for determining flows for subsurface treatment and disposal This Notice reviews new inflow data to the Te Anau wastewater ponds. This data is from 6 January 2013 to present, and is subsequent to the information in the resource consent application for WW disposal at the Kepler Block. This notice then sets out the rationale for determining the design flows for a subsurface drip irrigation (SDI) system that would treat and dispose of the flows from the Te Anau wastewater ponds. A key assumption is that a SDI system is able to operate under all conditions, and won’t (for example) need to cease discharging during storm events. This Notice refers to the June 2013 MWH document: ‘Te Anau Wastewater Flows Report’ (the Flows Report), that was included as Appendix F in the 2013 consent application document. 1. PEAK FLOWS

The present Discharge Permit 302625-01 of 22 January 2015 (under appeal) allows for a maximum discharge of 4,500m3/day to the North Kepler Block. This compares to the 3,000m3/day identified in the Flows Report as the peak day dry weather flow at maximum occupancy in 2048 (expected to be in summer). This allows a contingency of 1,500m3/day to due to wet weather peaks, and/or recovery from use of buffer storage. The Discharge Permit requires the maximum discharge rate to reduce to 2,000m3/day for the winter period 1 May to 31 August. 2. UNDERLYING ASSUMPTIONS

The following assumptions underlie the conclusions in this Notice: a) That the subsurface system is intended to be in a form of a subsurface drip irrigation (SDI) system

for the soil and pasture, such that the take-up of nutrients limits their discharge to ground water to within the limits of the Discharge Permit.

b) That irrigation rates are limited to those in the present Discharge Permit 302625-01 (under appeal). Condition 5 limits discharge to: • 4,500m3/day and 6.5mm depth of application during the period of 1 September to 30 April. • 2,000m3/day and 2.9mm at other times.

c) That the WW ponds and their operation are modified as required so that 5,000m3 of buffer storage is available. This gives effect to consent condition 13 (a) (viii), requiring this ‘...in anticipation of forecast rainfall events’.


Page 2

NOTICE TO CLIENT

d) That an additional 10,000m3 of storage is provided at the WW ponds as per consent conditions 6 (c) and 13 (a) (viii), ‘…as a contingency measure for extreme weather events, and/or equipment breakdown’.

e) That all buffer storage is in pond 1 (33,000m2), because it is most cost effective to raise the sides of the largest pond only.

f) It is noted that adding 5,000m3 into pond 1 will raise its level by 151mm. g) That rainfall accumulates on all three ponds, over an area totalling 48,000m2. h) That the 5,000m3 wet weather buffer storage shall be disposed of in 10 days, so that this storage is

available for the next event. This is based on an assumption that the need for any higher rate of storage recovery implies a very unlikely event for which the 10,000m3 storage for ‘extreme weather events’ could be used.

i) A climate change allowance of 1 degree Celsius. This is less than the usual 2 degrees (detailed on the MfE website) to recognise the shorter 25yr period of the consent.

j) That the implementation of an SDI system can be staged to match actual growth in flows. Therefore it is assumed that: • the initial flow capacity will be to year 2029 (half the consent term) • later expansion will cater for flows expected in year 2042 (full consent term).

3. REVIEW OF RECENT DATA

3.1 Introduction

The existing consent application used pond inflow data from 2010 up to January 2013 (the Flows Report). Section 2.3 of the Flows Report clarifies that these inflows were not directly measured, but calculated, based on pump hours and an allowance for a separate gravity flow. Since then, the following additional information is available.

• From 19 Dec 2015 the method of inflow measurement changed, and now ultilises a newly installed magflow meter at the inlet to the ponds. This can be used to calibrate the calculated inflows from 2010 – 15, as both methods of measurement ran concurrently until 30 June 2016.

• The inflow data from 2013 – 16. Note that this has been calculated from pump hours from the pumpstations feeding the ponds, plus an allowance of 20% from gravity sources.

• Rainfall data from 2013 to date. • The 2013 Census. • Consent condition 1 stipulates a 25 year consent term, not the 35 years sought. 35 years was used

for the growth predictions for flow. 3.2 New flowmeter on pond inlet

The graph below compares the flow recorded from the new flowmeter at the inlet to the ponds, with the previous method that calculated flow based on pump hours from contributing pumpstations, and a 20% allowance for gravity flow. This comparison is for the period 19 December 2015 to 30 June 2016. For this period, the average flow based on pump hours was 1,444m3/day, vs 1,418m3/day from the flowmeter. There is generally good correlation shown other than the pump hours give peakier figures, the reasons for this have not been explored. The conclusion is that the change in measurement method does not give a reason to revisit earlier data. However, it appears flows arriving at the pond may be in reality be less ‘peaky’ than inferred from measuring pumping hours.


Page 3

NOTICE TO CLIENT

3.3 Inflow and rainfall data 2013 -16

The graph below (Te Anau Wastewater Ponds. Daily Inflow and Rainfall 2010 – 2016) includes the 2013 – 16 data. It updates the graph in Appendix A of the Flows Report, which had data up to 6 January 2013. A larger version of the graph is appended. Observation regarding this more recent data are discussed in the sections below, on the Summer and Winter components. However, there is a strong correlation between major rainfall events and higher inflows, as is commonly experienced.

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Jul-10 Jan-11 Jul-11 Jan-12 Jul-12 Jan-13 Jun-13 Dec-13 Jun-14 Dec-14 Jun-15 Dec-15 Jun-16 Dec-16 Jun-17

Rainfall (mm

)

Pond

s Inf

low

(m3 /

day)

Te Anau Wastewater Ponds. Daily Inflow and Rainfall 2010 - 2016(updates the previous 2010 - 13 data)



Flow measurement changed to a magflow meter 19

0

500

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19 D

ec24

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29 D

ec3

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8 Ja

n13

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n23

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28 Ja

n2

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7 Fe

b12

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17 F

eb22

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27 F

eb4

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ch9

Mar

ch14

Mar

ch19

Mar

ch24

Mar

ch29

Mar

ch3

April

8 Ap

ril13

Apr

il18

Apr

il23

Apr

il28

Apr

il3

May

8 M

ay13

May

18 M

ay23

May

28 M

ay2

June

7 Ju

ne12

June

17 Ju

ne22

June

27 Ju

ne

Pond

inflo

w (m

3/da

y)

Te Anau Wastewater PondsComparison of inflow measurement

Pump hours vs new magflow19 Dec 2015 - 30 June 2016

Flow based on pump hours + 20% magflow data


Page 4

NOTICE TO CLIENT

3.4 Mid summer inflows

Inflows for the mid summer period (1 December to 28 February) are shown in the graph below (‘Te Anau Wastewater Ponds 2010-16 mid-summer daily inflows (Dec - Feb)’), and summarised in the table below. A larger version of the graph is appended. The data shows summer flows have been consistent up until the 2015/16 summer, when significantly higher flows were recorded, in the order of 40%. In particular the period from New Year to April had sustained high flows. Further study would be required to ascertain whether this increase was due to human factors (such as a signficant increase in tourist numbers), or environmental factors (such as temporarily high water tables influencing infiltration into the reticulation). Later in 2016, as discussed below, the flows returned to more historical levels. However, it will be important to monitor the 2016/17 summer to see if there is any trend. The Flows Report assumes a summer average dry day baseflow of 1,000m3/day for 2006, with various peaking factors on different accommodation types (eg houses vs hotels) to determine a peak dry day flow of 1,800m3/day. A further peaking factor of 1.2 on top of the above peak dry day flow was determined in the Flows Report to determine a peak wet weather day flow of 2,200m3/day for 2006.

Year Average Flow 1 Dec - 28 Feb

(m3/day)

Total Rainfall (mm)

2010 -11 1,053 270 2011 - 12 954 153 2012 - 13 1,002 282 2013 - 14 1,007 276 2014 - 15 1,015 217 2015 - 16 1,430 278

3.5 Winter flows (1 December to 28 February)

Inflows for the winter period (1 May to 31 August) are shown in the graph below (‘Te Anau Wastewater Ponds 2011-16 Winter Daily Inflows (May - August)’), and summarised in the table below. A larger version of the graph is appended. The Flows Report assumes a winter average dry day baseflow of 600m3/day for 2006, with various peaking factors on different accommodation types (eg houses vs hotels) to determine a peak dry day flow of 843m3/day. s2.1 of the Flows Report indirectly proposes a wet weather peaking factor in winter of 2.0 on top of the average dry day flow.

Year Average Flow

1 May - 30 August (m3/day)

Total Rainfall (mm)

2011 662 322 2012 682 238 2013 651 363 2014 865 315 2015 915 461 2016 1,179 501

0

500

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2500

1 Dec 8 Dec 15 Dec 22 Dec 29 Dec 5 Jan 12 Jan 19 Jan 26 Jan 2 Feb 9 Feb 16 Feb 23 Feb

Flow

s (Cu

bic

Met

ers)

Month

Te Anau Wastewater Ponds2010-16 Mid-summer Daily Inflows (Dec - Feb)

(updates the previous 2010/11 - 12/13 data)

Flows 10_11

Flows 11_12

Flows 12-13

Flows 13_14

Flows 14_15

Flows 15-16

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Flow

s (m

3/da

y)

Month

Te Anau Wastewater Ponds2011-16 Winter Daily Inflows (May - August)

(updates the previous 2011 - 12 data) Flows 2011, previous data

Flows 2012, previous data

Flows 2013, new data





Page 5

NOTICE TO CLIENT

In reviewing the data, there is good correlation between larger rainfall events and spikes in the inflow. This leads to the conclusion that the dry weather baseflow has been reasonably consistent over the years. For example the May 2016 spike in inflows coincides with 223mm of rain in that month. 3.6 L22013 census

The population of Te Anau was given in the 2006 census as 1,899. This increased slightly to 1,911 in the 2013 census. This is less than the medium projection of 2,018 given in the Flows Report, but our judgement is that this should not alter the projections of the Flows Report because growth was artificially depressed from 2009 due to the global financial crisis (GFC). Evidence of this could be seen in the downturn of house building in subdivisions recently developed before the GFC. 3.7 25 vs 35 year consent term

The outcome from the Flows Report was that the peak dry day summer inflow into the ponds grerw from 1,800m3/day to 3,000m3/day in the period 2006 to 2048. This equates to an annual growth rate of approx. 1.22%. Assuming linear growth, if a 25yr consent is finalised in 2017, the predicted peak dry day summer inflow in 2042 is 2,790m3/day, 7% less than the 2048 forecast. 3.8 Conclusions regarding 2013 -16 data

In general, the updated data supports the continued use of the inflows predicted in the Flows Report and Kepler consent application. However, we note that the increased inflows recorded in 2016 warrant further investigation to understand their causes better. Recorded flows were generally higher over the 2015/16 summer and autumn. There have been specific rainfall events that partly account for this, but not completely. Rainfall in this time has generally been higher, but outside of larger events, the correlation between rainfall and pond inflow is not necessarily directly proportional, and doesn’t fully explain the higher flows observed over the 2015/16 summer. We are not aware of any changed circumstances (eg connection of a new area of reticulation) sufficient to fully account for the increased inflows. The inflows appear to have settled back to historical bounds. It will be important to observe flows over the 2016/17 summer to see if there is any repeat of these levels, but overall, no need is seen to amend the inflow rate predictions used to date. Flows over the last year do highlight how periods of higher inflow can happen. This reinforces the importance of not trimming down the maximum design outflow capacity from the ponds. 4. RATIONALE FOR 10YR ARI EVENT WITHIN 5,000m3 BUFFER STORAGE

Consent condition 13 (a) (viii) requires an Environmental Management Plan (EMP) “…to provide an additional 5,000 cubic metres of storage capacity in anticipation of forecast rainfall events”. A 10yr period is normally considered the Annual Recurrence Interval (ARI) to base the design of primary (ie piped) stormwater systems, if you like, the ‘business as usual’ design scenario. Therefore, an assumption has been made to use a 10yr ARI to conform to the above consent condition. We reviewed the data for Te Anau from NIWA HIRDS v3 (ref NIWA website). It can be seen that the maximum duration event for which statistical data is available is 72 hours. A judgement was made that 250mm was reasonable extrapolation for a 10 day event, with a 10yr ARI. However, to confirm this, a statistical analysis of the raw data would be required, and this has not been done. It is noted that from 2010-2016 there have been three 10 day periods in the order of 150mm cumulative rainfall.


Page 6

NOTICE TO CLIENT

5. DETERMINING A DESIGN FLOW FOR DISCHARGE TO A SDI SYSTEM

The primary approach to determining a peak design outflow from the ponds was based on the theoretical demand as calculated in the Flows Report. The mass balance in the ponds was modelled to determine a constant outflow sufficient to keep pond levels within the buffer storage, while accounting for population growth, wet weather peaking factors, and rainfall on the ponds. As a check against the primary method, a similar mass balance was undertaken using recorded actual inflows to the ponds, with allowances for growth and the possibility that recorded flows underestimate a reasonable value for a 10 year period. 5.1 Primary method

The peak inflow calculations are based on a 10 day period, being equivalent to the peak Christmas/New Year period. This is assumed to coincide with a 10 day, 10yr ARI rain event.

a) Calculate inflows based on the 2006 Peak Summer Dry Day (1,800m3/day) as derived in the Flows Report.

b) An assumption is made that the Peak Summer Dry Day flow, as above, will continue over the design period.

c) Update the above flows, as appropriate, to account for the further information from 2013 – 16. (As shown above, no change required).

d) Increase these inflows to allow for growth to 2029 and 2042, being half, and all of, the 25 year consent period.

e) The rate of increase of these flows over time shall be assumed to be a straightline, at the rate in the Flows Report. Namely, the 1,800m3/day Summer Peak Dry Day in 2006 increases to 3,000m3/day in 2048.

f) Multiply these inflows by a wet weather peaking factor of 1.2, being the peaking factor for wet weather at the summer peak population time (s2.1 of the Flows Report). The use of this value is commented upon elsewhere in this Notice.

g) Assume the above 10 days of peak inflow coincides with a 10 day duration, 10yr ARI storm event. In the absence of better statistical data, this is assumed to be 25mm a day, for 10 days.

h) This rainfall on the ponds is converted to an equivalent m3/day inflow. i) Determine a constant discharge rate from the ponds such that the pond volumes are kept within the

5,000m3 buffer storage.


Page 7

NOTICE TO CLIENT

5.2 Comments

Review of the data 2010-16 shows that it is reasonable to combine peak wet day flows with rain events that accumulate rain onto the ponds’ surface. Unsurprisingly these events often coincide. Modelled scenarios tend to show that the limiting factor is the volume of buffer storage available, rather than how long it takes to dispose of the buffer storage. Once it stops raining, if the rate of discharge is kept the design maximum, the ponds can be drawn down reasonably quickly, in less than 10 days. 5.3 Verification method – Mass balance check based on extrapolating recorded flows

A 20-day period is assessed, to allow for the buffering effects of pond storage during 10 days of rainfall accumulation and up to 10 days to dispose of buffer storage. A mass balance is based on the rainfall that can be expected from a 10 day duration storm, with a 10 year ARI, with no more than 5,000m3 buffer storage used. As for the primary method, this 10yr ARI storm is assumed to be over Christmas/New Year period.

a) Analyse daily inflow data 2010 – 16, determine the greatest inflow in a 3-day period, and calculate a daily average.

b) Use this ‘3-day’ figure as a reasonable proxy for a maximum present-day sustained pond inflow. c) Scale this 3-day figure up by 15% to allow for a worst case in a 10yr (vs 6yr of data) period. 15% is

selected as it is the increase in rainfall intensity generally shown in HIRDS between a 5 and 10 year ARI. We note that there is, at best, an indirect correlation between HIRDS and inflow, but review of inflow data is reasonably supportive.

d) Further scale this 3-day figure up to allow for growth to 2029, being the first staged design horizon. e) Determine the volume of rainfall on the ponds, extrapolating from HIRDS for a 10yr ARI over 10

days, and convert to a equivalent daily inflow volume. f) Determine the required sustained pond outflow assuming:

• There is a 10yr, 10day ARI event for the first 10 days, and then no rain. Assumed to be 25mm a day for 10 days

• The above ‘3-day’ flow occurs for 10 days • For the following 10 days the above inflow occurs, less the wet weather peaking factor of 1.2 • A limit of 5,000m3 of buffer storage is available in the ponds • Buffer storage is to be restored within 10 days.

5.4 Comments

A 3-day figure of 1,944m3/day was selected for the verification method, noting some of peak flows below. There is sometimes a mismatch of several days between inflow peaks and rainfall. This is not considered significant because rainfall and high inflows were not limited to these days, and it did not affect the results to any great degree.

a) Pond inflow of an average of 1,688m3/day recorded in 10 day period of 17 - 26th Feb 2016, and 1,944m3/day between 253 - 27th Feb 2016. 148mm of rain occurred 18 - 27th Feb.

b) Inflow of an average of 1,626m/day recorded in 3 day period of 31 Dec 2012 to 2 Jan 2013. 74mm of rain occurred 30 Dec 2012 to 3 Jan 2013.

Greater than the above, an inflow of an average of 2,469m3/day was recorded in the 10 day period of 16-25th May 2016. 153mm of rain occurred 8 - 17th May. This inflow is of some concern as it is in the time period in the discharge consent when disposal flows are to be below 2,000m3/day. This flow was not used in the verification method because it was judged that due to the time of year a large component arose from inflow and infiltration (I and I), not directly related to the growth factors, and that the hydraulic disposal capacity required for summer peaks would be sufficient. 12,000m3 of buffer storage would be required for the above event if the disposal rate was limited to 2,000m3/day. The occurrence of the above 2,469m3/day average reinforces that the design maximum outflow from the ponds needs to cater for occasional more severe events.


Page 8

NOTICE TO CLIENT

6. OTHER CONSIDERATIONS

6.1 Additional factors

This Notice determines design peak daily flows from the wastewater ponds. It does not calculate instantaneous flow rates to a disposal field which may increase due to:

• Downtime for backwashing and/or reasonably foreseeable routine servicing of mechanical equipment. It is considered reasonable for unforeseen outages to be catered for by buffer storage at the ponds

• Degradation of disposal field performance (if any) over the assumed 12 year period before it is upsized.

Therefore, the designers of the SDI disposal field will need to consider the above, and any other factors, that might require the area of the disposal field to be increased. 6.2 Sensitivity

The Flows Report indicates that peak wet weather inflow is not too sensitive to population numbers. There is not a proportional relationship, because inflow and infiltration is related to the size of the reticulation network, and the population peaks just fit more people within the same network, ie hotels are fuller. Section 2.1 of the Flows Report says that using a wet weather peak value of 2 x summer baseflow is defendable, and gives a similar figure to 1.2 x summer peak. This is supported by recorded flows, for example, pond inflow for 15/16 September 2012 (‘base’ time) averaged 1,549m3/day when 72mm of rain occurred on these two days. For 1st/2nd January 2013 (peak time) inflow averaged 1,682m3/day with 50.6mm of rain. 7. CONCLUSIONS – DESIGN MAXIMUM FLOWS FROM THE PONDS

The conclusions below are based on a design horizon of 2029 and 2042, versus 2048 assumed in the Flows Report. 7.1 Definition

The ‘Design Peak Daily Flows’ given below are the maximum flows that will be delivered to the disposal site from the ponds. They can be expected to be of a duration of at least 14 days during a 1 in 10 year event. These peak flow rates can be expected to occur for shorter periods on an annual basis. This is because there are still regular occurring shorter duration rainfall events, sometimes of higher intensity, that demand use of buffer storage, and it is assumed that operations staff will be keen to recover this promptly. 7.2 Design peak daily flow from the Te Anau wastewater ponds – to 2029

• The primary method of assessment gave a result of 3,550m3/day. • The verification method of assessment gave a result of 3,650m3/day. • Therefore a figure of 3,600m3/day should be used.

Based on the present discharge permit (under appeal), with a maximum irrigation depth of 6.5mm/day, a disposal area of 55 Hectares is inferred for 3,600m3/day 7.3 Design peak daily flow from the Te Anau wastewater ponds – to 2042

• The primary method of assessment gave a result of 4,050m3/day.

Based on the present discharge permit (under appeal), with a maximum irrigation depth of 6.5mm/day, a disposal area of 62 Hectares is inferred for 4,050m3/day


Page 9

NOTICE TO CLIENT

7.4 Other Conclusions

The observed rainfalls 2010 – 16 are significantly less than the predictions for a 10yr ARI storm. This supports:

• A factor of safety being added to any calculation based on historical data • Basing design on the 5,000m3 buffer storage for ‘forecast rain events’, and therefore leaving free the

additional 10,000m3 ‘extreme event’ storage. Further to the above the amount of buffer storage available is sensitive to the design peak daily outflow rate, and assumptions have been made in this regard. If a lower outflow rate is accepted, more buffer storage will be used more frequently, and the risk increases of an occurrence when all buffer storage is exhausted and pond overflow will occur. Ultimately this balance is a risk owned by SDC. Follow-up is required regarding the higher inflows recorded in the first part of 2016 to better understand their cause. One logical action is to make a comparison with the upcoming 2016/17 summer data. The Design Peak Daily Flows calculated in this Notice cannot be used to calculate design instantaneous flows in the transfer pipeline between the ponds and disposal site. This is because the discharge at the disposal site may not be uniform over a 24 hour period. A key assumption in this Notice is that a SDI system is able to operate under all conditions, and won’t (for example) need to cease discharging during storm events. Roger Oakley Project Manager

emailed 9 November 2016 cc Tony Davoren, Hydro Services Ltd Attached:

• Peak daily flow rate calculation – 2029 horizon, primary method • Peak daily flow rate calculation – 2029 horizon, verification method • Peak daily flow rate calculation – 2042 horizon, primary method • Graph: Te Anau Wastewater Ponds. Daily Inflow and Rainfall 2010 - 2016 • Graph: Te Anau Wastewater Ponds 2010-16 Mid-summer daily inflows (Dec - Feb) • Graph: Te Anau Wastewater Ponds 2011-16 Winter daily inflows (May - August) • Graph: Te Anau Wastewater Ponds, Comparison of inflow measurement’ Pump hours vs new magflow,

19 Dec 2015 - 30 June 2016

DATE: 9/11/2016 (for Client) (for MWH Ltd)

Reviewed by: John Cocks Copies: Blue For Client to sign and return to MWH (if requested) Yellow File MWH New Zealand Ltd

Level 3, John Wickliffe House Telephone: 0-3-477 0885 265 Princes Street Facsimile 0-3-477 0616 Dunedin, New Zealand

0

500

1000

1500

2000

2500

3000

35001

9 D

ec

24

De

c

29

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c

3 J

an

8 J

an

13

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28

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7 J

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12

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17

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ne

22

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ne

27

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ne

Po

nd

infl

ow

(m

3/d

ay

)

Te Anau Wastewater Ponds

Comparison of inflow measurement

Pump hours vs new magflow

19 Dec 2015 - 30 June 2016

Flow based on pump hours + 20% magflow data

0

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20

30

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50

60

70

80

90

1000

500

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1500

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4500

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Jul-10 Jan-11 Jul-11 Jan-12 Jul-12 Jan-13 Jun-13 Dec-13 Jun-14 Dec-14 Jun-15 Dec-15 Jun-16 Dec-16 Jun-17

Ra

infa

ll (mm

)P

on

ds

Infl

ow

(m

3/d

ay

)

Te Anau Wastewater Ponds. Daily Inflow and Rainfall 2010 - 2016(updates the previous 2010 - 13 data)



Flow measurement

changed to a

magflow meter 19

0

500

1000

1500

2000

2500

1 Dec 8 Dec 15 Dec 22 Dec 29 Dec 5 Jan 12 Jan 19 Jan 26 Jan 2 Feb 9 Feb 16 Feb 23 Feb

Flo

ws

(Cu

bic

Me

ters

)

Month


2010-16 Mid-summer Daily Inflows (Dec - Feb) (updates the previous 2010/11 - 12/13 data)

Flows 10_11

Flows 11_12

Flows 12-13

Flows 13_14

Flows 14_15

Flows 15-16

0

500

1000

1500

2000

2500

3000

1 May 8 May 15 May 22 May 29 May 5 Jun 12 Jun 19 Jun 26 Jun 3 July 10 July 17 July 24 July 31 July 7 Aug 14 Aug 21 Aug 28 Aug

Flo

ws

(m3

/da

y)

Month


2011-16 Winter Daily Inflows (May - August)(updates the previous 2011 - 12 data)







TE ANAU WASTE WATER SCHEMEDetermination of Design Peak Daily Flows

Primary Method for calculation Prepared by Roger Oakley MWH

Design Horizon - 2029 Checked by John Cocks MWH

Nov-16

Day

10 yr ARI

Rainfall

event

(mm)

Rain vol

into

ponds

(m3)

Year 2006

PSDD

inflow

(m3)

Change

due to

2013-16

data

Year 2029

PSDD

inflow

(m3)

Wet

weather

peaking

factor

Required

outflow

rate

(m3/day)

Change in

buffer

storage

(m3)

Cum

storage

(m3)

25 1,800 1.00 1.32 1.20 3,550Base figures or

multiplier

0 0 0 1,800 1,800 2,381 2,857 3,550 0 0

1 25 1,200 1,800 1,800 2,381 2,857 3,550 507 507

2 25 1,200 1,800 1,800 2,381 2,857 3,550 507 1,014

3 25 1,200 1,800 1,800 2,381 2,857 3,550 507 1,521

4 25 1,200 1,800 1,800 2,381 2,857 3,550 507 2,028

5 25 1,200 1,800 1,800 2,381 2,857 3,550 507 2,535

6 25 1,200 1,800 1,800 2,381 2,857 3,550 507 3,042

7 25 1,200 1,800 1,800 2,381 2,857 3,550 507 3,549

8 25 1,200 1,800 1,800 2,381 2,857 3,550 507 4,056

9 25 1,200 1,800 1,800 2,381 2,857 3,550 507 4,563

10 25 1,200 1,800 1,800 2,381 2,857 3,550 507 5,070 Buffer storage full

11 0 1,800 1,800 2,381 2,381 3,550 -1,169 3,900

12 0 1,800 1,800 2,381 2,381 3,550 -1,169 2,731

13 0 1,800 1,800 2,381 2,381 3,550 -1,169 1,562

14 0 1,800 1,800 2,381 2,381 3,550 -1,169 393 Buffer restored

15 0 1,800 1,800 2,381 2,381 3,550 -1,169 -776

16 0 1,800 1,800 2,381 2,381 3,550 -1,169 -1,946

17 0 1,800 1,800 2,381 2,381 3,550 -1,169 -3,115

18 0 1,800 1,800 2,381 2,381 3,550 -1,169 -4,284

19 0 1,800 1,800 2,381 2,381 3,550 -1,169 -5,453

20 0 1,800 1,800 2,381 2,381 3,550 -1,169 -6,622

Totals 250 12000

Notes:

PSDD - Peak summer dry day

Note, once rain stops, buffer storage is drawn down promptly

Inflow is reduced by wet weather factor of 1.2 when rain stops

Pond outflow calcs SDI Nov 2016 12:37 p.m. 4/11/2016


Verification Method for calculation Prepared by Roger Oakley MWH


Nov-16

Day

10 day, 10

yr ARI

Rainfall

event

(mm)

Rain vol into

ponds (m3)

Max

recorded

3-day

inflow*

(m3/day)

Factor of

Safety for

10yr

worst

case

Growth

factor for

2029

Required

outflow

rate

(m3/day)

Change in

buffer

storage

(m3)

Cum

storage

(m3)

25 1,944 1.15 1.32 3,650Base figures or

multiplier:

0 0 0 1,944 2,236 2,957 3,650 0 0

1 25 1,200 1,944 2,236 2,957 3,650 507 507

2 25 1,200 1,944 2,236 2,957 3,650 507 1,014

3 25 1,200 1,944 2,236 2,957 3,650 507 1,521

4 25 1,200 1,944 2,236 2,957 3,650 507 2,028

5 25 1,200 1,944 2,236 2,957 3,650 507 2,535

6 25 1,200 1,944 2,236 2,957 3,650 507 3,042

7 25 1,200 1,944 2,236 2,957 3,650 507 3,549

8 25 1,200 1,944 2,236 2,957 3,650 507 4,056

9 25 1,200 1,944 2,236 2,957 3,650 507 4,563

10 25 1,200 1,944 2,236 2,957 3,650 507 5,070 Buffer storage full

11 0 1,620 1,863 2,464 3,650 -1,186 3,884

12 0 1,620 1,863 2,464 3,650 -1,186 2,698

13 0 1,620 1,863 2,464 3,650 -1,186 1,512

14 0 1,620 1,863 2,464 3,650 -1,186 326 Buffer restored

15 0 1,620 1,863 2,464 3,650 -1,186 -860

16 0 1,620 1,863 2,464 3,650 -1,186 -2,046

17 0 1,620 1,863 2,464 3,650 -1,186 -3,231

18 0 1,620 1,863 2,464 3,650 -1,186 -4,417

19 0 1,620 1,863 2,464 3,650 -1,186 -5,603

20 0 1,620 1,863 2,464 3,650 -1,186 -6,789

Totals 250 12,000

Notes:

Inflow of an average of 1626m3/day recorded in 3 day period of 31 Dec 2012 to 2 Jan 2013. 74mm of rain occurred 30 Dec 2012 to 3 Jan 2013.

Inflow of an average of 1688m3/day recorded in 10 day period of 17 -26th Feb 2016, and 1,872m3/day 24-26th . 148mm of rain occurred 18 - 27th Feb.

Inflow of an average of 2,469m3/day recorded in 10 day period of 16-25th May 2016. 153mm of rain occurred 8 - 17th May.





Primary Method for calculation Prepared by Roger Oakley MWH


Nov-16

Day

10 yr ARI

Rainfall

event

(mm)

Rain vol

into

ponds

(m3)

Year 2006

PSDD

inflow

(m3)

Change

due to

2013-16

data

Year 2042

PSDD

inflow

(m3)

Wet

weather

peaking

factor

Required

outflow

rate

(m3/day)

Change in

buffer

storage

(m3)

Cum

storage

(m3)

25 1,800 1.00 1.55 1.20 4,050Base figures or

multiplier:

0 0 0 1,800 1,800 2,788 3,346 4,050 0 0

1 25 1,200 1,800 1,800 2,788 3,346 4,050 496 496

2 25 1,200 1,800 1,800 2,788 3,346 4,050 496 992

3 25 1,200 1,800 1,800 2,788 3,346 4,050 496 1,489

4 25 1,200 1,800 1,800 2,788 3,346 4,050 496 1,985

5 25 1,200 1,800 1,800 2,788 3,346 4,050 496 2,481

6 25 1,200 1,800 1,800 2,788 3,346 4,050 496 2,977

7 25 1,200 1,800 1,800 2,788 3,346 4,050 496 3,473

8 25 1,200 1,800 1,800 2,788 3,346 4,050 496 3,970

9 25 1,200 1,800 1,800 2,788 3,346 4,050 496 4,466

10 25 1,200 1,800 1,800 2,788 3,346 4,050 496 4,962 Buffer storage full

11 0 1,800 1,800 2,788 2,788 4,050 -1,262 3,700

12 0 1,800 1,800 2,788 2,788 4,050 -1,262 2,439

13 0 1,800 1,800 2,788 2,788 4,050 -1,262 1,177

14 0 1,800 1,800 2,788 2,788 4,050 -1,262 -84 Buffer restored

15 0 1,800 1,800 2,788 2,788 4,050 -1,262 -1,346

16 0 1,800 1,800 2,788 2,788 4,050 -1,262 -2,607

17 0 1,800 1,800 2,788 2,788 4,050 -1,262 -3,869

18 0 1,800 1,800 2,788 2,788 4,050 -1,262 -5,130

19 0 1,800 1,800 2,788 2,788 4,050 -1,262 -6,392

20 0 1,800 1,800 2,788 2,788 4,050 -1,262 -7,653

Totals 250 12000

Notes:

PSDD - Peak summer dry day





Appendix D NTC 32 Design Nitrogen Loads


Page 1

NOTICE TO CLIENT

DATE 7 December 2016 CLIENT SDC Water and Waste Services

CONTRACT Te Anau Wastewater Scheme ADDRESS PO Box 903

PROJECT NO. 80508264-C-C1 INVERCARGILL

CONSECUTIVE NO. 32 ATTENTION: Ian Evans P:\_2012 Onwards\Southland District Council\80508264 Te Anau WWTP\C - Client Correspondence\C1 - Notices to Clients\NTClient

32 Average flows and loads.docx

TE ANAU WW SCHEME Average Flows and Loads This Notice provides proposed figures for the purpose of comparing subsurface drip irrigation (SDI) with centre pivot irrigation (CPI) with respect to removing nitrogen so as to comply with the resource consent conditions. Average flows are those presented in Notice to Client No 30, first table. 1. Proposed Figures for CPI

The CPI system will receive effluent from a biological trickle filter (BTF). The BTF will convert almost all the ammoniacal-N in the oxidation pond effluent to nitrate. Table 1: Average flows and Concentrations of Nitrogen in Effluent to CPI system

Parameter Unit Winter

1 May 31 August

Summer

1 September – 30 April

Current

Average daily flow m3/d 826 981

Nitrogen concentrations

NOX-N g/m3 20.2 17.1

Ammonia-N g/m3 0.5 0.2

Particulate organic N (algae) g/m3 5.5 5.5

Non-biodegradable N g/m3 0.8 1.2

Total N g/m3 27.0 24.0

Future (2042)

Average daily flow m3/d 1,189 1,413


NOX-N g/m3 20.2 17.1


Particulate organic N (algae) g/m3 5.5 5.5


Total N g/m3 27.0 24.0


Page 2

NOTICE TO CLIENT

2. Proposed Figures for SDI

The SDI system will receive effluent from a microfiltration (MF) plant. The MF plant will remove particulate organic nitrogen in the oxidation pond effluent. Table 2: Average flows and Concentrations of Nitrogen in Effluent to SDI system

Parameter Unit Winter

1 May 31 August

Summer

1 September – 30 April

Current

Average daily flow m3/d 826 981


NOX-N g/m3 0 0.3



Total N g/m3 21.5 18.5

Future (2042)

Average daily flow m3/d 1,189 1,413


NOX-N g/m3 0 0.3



Total N g/m3 21.5 18.5

John Cocks Acting Project Manager

emailed 7 December 2016 cc Tony Davoren, HydroServices Ian McIndoe, Aqualinc

(for Client) (for MWH Ltd) Reviewed by:

Copies: Blue For Client to sign and return to MWH (if requested) Yellow File

MWH New Zealand Ltd Level 3, John Wickliffe House Telephone: 0-3-477 0885 265 Princes Street Facsimile 0-3-477 0616 Dunedin, New Zealand


Appendix E Consented Irrigation Area

- 12 - AUTH-302625-01

Attachment 1

August 2018 │ Status: Final│ Project No.: 80508264 │ Our ref: r_SDI BoDesign v13

Appendix F SDI Field Layout Options

DESIGNATION BOUNDARY

WINDBREAKWINDBREAK

WIN

DBRE

AK

WIN

DBRE

AK

PEATBOG

MANAPOURI AIRPORT

NOTES1. EACH INLET & FLUSH MAIN PIPE HAS A

POWER AND SIGNAL CABLE IN THESAME TRENCH.

2. DRAWING TO BE READ INCONJUNCTION WITH STANTEC "BASISOF DESIGN" REPORT 2018.

3. AIR RELEASE/VACUUM BREAK VALVESNOT SHOWN.

KEY:INLET PIPEFLUSH RETURN PIPE

A1

FOR REVIEW

NOT FOR CONSTRUCTION

23.04.18

NOT APPROVED

ZONE 1ZONE 3

ZONE 5

ZONE 2ZONE 4

ZONE 6

ZONE 7230m*330m

10.00m CORRIDORBETWEEN ZONES

ZONE 8

230m*330m

230m*330m

230m*330m

230m*330m

230m*330m

230m*330m

230m*330m

STAGE 2 ZONES TOACHIEVE 4,500 m³/DAY

FLUSH FILTER

INLET FILTER

PUMP HOUSE

BALANCE TANK

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Rev.

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Rev.

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SURVEYED

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DRAWN

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DESIGNED

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DESIGN CHECK

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APPROVED

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CAD REVIEW

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CAD REVIEW

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THESE DRAWINGS SHALL ONLY BE USED FOR THE PURPOSE FOR WHICH THEY WERE SUPPLIED. ANY RE-USE IS PROHIBITED AND NO PART OF THIS DOCUMENT MAY BE REPRODUCED OR DISTRIBUTED WITHOUT THE WRITTEN PERMISSION OF MWH LTD.

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TE ANAU WW SCHEME

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SITE PLAN OF IRRIGATION ZONES - CONCEPT LAYOUT

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OPTION 1

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Z1041108

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01

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1 : 2500

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1 : 2500

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1 : 2500

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1 : 2500

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TRUESOUTH

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Peter A Thomson

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07/02/13

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pw:\\asiavpwint04.mwhglobal.com:AP_PROJECTS\Documents\New Zealand Clients\Southland District Council\Z1041108 - Te Anau WW Scheme\01\Civil\Z1041108-01-001-D011

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100m


WINDBREAKWINDBREAK

WIN

DBRE

AK

WIN

DBRE

AK

PEATBOG

MANAPOURI AIRPORT






A1

FOR REVIEW


23.04.18

NOT APPROVED

ZONE 1220m*340m


ZONE 4

ZONE 3ZONE 2a

ZONE 5a

ZONE 3

ZONE 6

ZONE 8

5.00m

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m CO

RRID

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N ZO

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OPTION 2


FLUSH FILTER

INLET FILTER

PUMP HOUSE

BALANCE TANK

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TE ANAU WW SCHEME

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SITE PLAN OF IRRIGATION ZONES - CONCEPT LAYOUT

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OPTION 1

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Z1041108

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01

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001

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1 : 2500

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1 : 2500

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1 : 2500

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1 : 2500

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TRUESOUTH

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Peter A Thomson

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07/02/13

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100m

FLUSHING ZONE 5

FLUSHING ZONE 3

FLUSHING ZONE 2

FLUSHING ZONE 1

TO NEXT ZONE

DN250 PE PIPE

DN250 PE PIPE

DN150 PE PIPE

DN150 PE PIPE

DN125 FLUSH SUBMAINS

FLUSHING ZONE 466-DN17 DRIPPER LINE- 1m CRS. TYP.

240.00m

330.0

0m

CONTROL VALVESIN CHAMBER

PRESSURE INDICATORCONTROL VALVE ANDVACUUM/AIR VALVE INCHAMBER (TYP.)

NOTES1. EACH INLET & FLUSH MAIN PIPE HAS A POWER

AND SIGNAL CABLE IN THE SAME TRENCH.2. DRAWING TO BE READ IN CONJUNCTION WITH

STANTEC "BASIS OF DESIGN" REPORT 2018.

A1

FOR REVIEW


23.04.18

NOT APPROVED

BULKMAIN

FLUSHING MAIN

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TE ANAU WW SCHEME

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TYPICAL IRRIGATION ZONE LAYOUT - CONCEPT LAYOUT

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OPTION 1

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Z1041108

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01

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001

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AS SHOWN

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Peter A Thomson

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07/02/13

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FLUSHING ZONE C

FLUSHING ZONE B

FLUSHING ZONE A

DN150 SUBMAIN

DN100 FLUSH SUBMAINS

FLUSHING ZONE D

55-DN20 DRIPPER LINE- 1m CRS. TYP.

340.00m

220.0

0mACTUATED INLETVALVE IN CHAMBER

PRESSURE INDICATORCONTROL VALVE ANDNON-RETURN VALVE ANDVACUUM/AIR VALVE INCHAMBER (TYP.)

DN100 FLUSH RETURN

Qmax 18l/s

DN250 BULK MAIN

6l/s

NOTES1. EACH INLET & FLUSH MAIN PIPE HAS A POWER

AND SIGNAL CABLE IN THE SAME TRENCH.2. DRAWING TO BE READ IN CONJUNCTION WITH


A1

FOR REVIEW


23.04.18

NOT APPROVED

D012BOPTION 2

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Appendix G Review Feedback – P Riddell

App3_Ecogent response Aug 2018v3_ReviewComments.docx Page 1

TE ANAU WASTEWATER SCHEME – BASIS OF DESIGN FOR SUBSURFACE DRIP IRRIGATION Responses by Stantec to feedback from Peter Riddell of Ecogent Ltd Feedback based on Stantec Draft Basis of Design Reports dated 12 July 2018, and earlier versions dated 1 June 2018 and 23 May 2018. Response last updated 14 August 2018 Stantec responses prepared by Roger Oakley Peer reviewer responses prepared by Ben Stratford, Mainline Aqua, 25 August 2018.

Design Report Ref

Comment by Peter Riddell (Ecogent Ltd)

Stantec Response Peer Reviewer Response

P Riddell email of 11 May 2018 4.45pm Comment on Subsurface Drip Irrigation

s7.18

Comments – 25 July 2018

S 7.18 I have attached a revised and improved layout of the previous concept sent to you (Eco 01.2)-labelled Option 3. It has quite a few cost efficiencies compared to the original layout. It would be subject to detailed design including avoiding wet areas, incorporating drainage and access tracks etc but gives an idea of an effective scheme.

Noted. See Stantec Option 3, which is similar, and what the estimate is based on. Agree detailed design would need to look at basic contouring, and budget allowance added to estimate.

Agree – cost estimates have been updated to reflect more efficient layout options.

S 7.18.13 Note also previous comments on s6.18.13. There are actually no obvious advantages in the original concept (1) of having large fields which take the entire design flow. It is unwieldy and difficult to isolate specific areas for any reason such as maintenance, resting for harvest, isolating of a wet area etc. The proposed layout using smaller fields gives much greater flexibility to meet changing flows for whatever reason than single large fields.

Agree. See Stantec Option 3 Agree – smaller fields will give better flexibility. Balance expected through procurement between less, larger, or more, smaller zones.


Design Report Ref



A spreadsheet is attached which lists some of the main quantities and gives some indication of the potential cost savings.

Noted. Cost estimates have been updated to incorporate indicative costs where appropriate.

I have also attached a copy of communications with one company that specialises in irrigation control to give you an indication of one control options. Option 1 would be appropriate as it doesn’t have soil moisture control feedback. A cost estimate for the valve control hardware is attached also.

Noted. Will be referred to if SDI proceeds. Cost estimates have been updated to incorporate indicative costs where appropriate.

Specific items arising: 1 Hydrus confirms the dripper spacing of 1m x

0.8m is practical. It needs to also model the effect of numerous small doses in applying water which is normal drip industry practice.

Agree. Underway. Hydrus modelling should reasonably reflect the soil parameters at Kepler for both SDI and CPI – this has been a major point of contention and it is not acceptable there should be such a perceived N reduction performance benefit in applying water to the site through either system. The treatment processes prior to site disposal will define the forms of nitrogen remaining in the effluent, and the soil composition and crop selection will determine the level of N reduction through the system.

2 Hydrus leaching modelling. Commented on previously but note an 8 litre prolonged dose from 1 emitter is not representative in looking at leaching.

Noted. Further work underway to refine this.

3 Note also the need to model the lower mobility of ammonium nitrogen when considering leachate.

Initial response from Aqualinc is that this can’t be specifically quantified, but accepted that this is can only reduce nitrate leaching risk. Noted as an opportunity.

4 This also applies to using Overseer as a relative measure of Nitrogen discharge

Our understanding is that Overseer assumes an immediate conversion to nitrate.

There are wider issues with Overseer, but in general the N reduction should reflect the mass balance approach through the treatment process (reducing N in the form of nitrate), fertiliser inputs, and outputs such as crop harvest and grazing (if applicable).


Design Report Ref



5 Note that literature shows value of plant uptake of N from drippers particularly when application rates are lower than plant demand which is the particular case at Kepler for SDI and CPI in summer.

Noted Agree that application efficiency of SDI is higher than CPI and could benefit crop growth through low inflow periods when application rates will not meet evapotranspiration rates. If soils are light, as indicated in the initial soil profile information, the risk of moisture deficit during summer months is high for both systems.

6 Root intrusion. Have provided an update on Trifluralin use. Note some other methods involve injection of herbicide in the irrigation water or copper based techniques which we don’t recommend.

Noted and report updated Interestingly you get the opposite feedback when talking to Netafim who make drip tubing with a copper oxide root intrusion system. Further industry expertise will be required as this is a major risk with SDI.

7 Comparable projects. The Smelter field is a similar size to one of the proposed Kepler fields

Noted in updated report. Although performance requirements re N must be compared too.

I am unfamiliar with the Tiwai smelter treatment process, but the Omaha and Pauanui SDI systems follow different treatment processes, therefore N reduction cannot reasonably be compared with the proposed Te Anau system. It would be even further difficult to then reasonably compare the likely performance by SDI or CPI. Again, the treatment process, soil composition and crop management are the N removal tools, not the application infrastructure.

8 Pauanui operates at peaks of about 7,500m3/d and has capacity for much greater flows.

Noted Pauanui is a sand dune, there are high rate application zones straight into the sands along Vista Paku Drive that can take up to 1100mm application. Note that the treatment process is sequential batch reactor (SBR), filtration and UV – a much higher quality effluent than proposed for Te Anau.


Design Report Ref



9 Omaha deals with over 2,500 houses as well as high weekend and holiday visitor numbers.

Noted. Omaha is also built on sand dunes, with high disposal application rates available for UV sterilised effluent. Disposal fields are also close proximity to the treatment plant with low risk of effluent degradation through the main pipeline.

10 The use of SDI for crop irrigation worldwide is increasing because it is a more efficient use of water and nutrient.

Noted, although for Te Anau, shoulder and winter govern when water efficiency not an issue

Agree that efficient application of water is improved with SDI and the increasing value of water resources means the capital investment required to apply by SDI is more appealing over the long term. Ironically the opposite is generally applicable for disposal sites, particularly when related to domestic wastewater flows where peak inflow coincides with wet weather events when irrigation would typically not be required. Refer earlier comments where during some periods the efficient application through SDI could help improve crop production through dryer periods.

11 No significant issues require resolution that cannot be dealt with using current knowledge. Hydrus for example is used elsewhere and seeking assistance to use this may be more expedient than starting from a low experience base.

Noted. A full Hydrus brief will be required if SDI proceeds

I am not familiar enough with Hydrus to comment about local knowledge in it’s use. However, there are fundamental soil processes that are required to “treat” effluent, including retention time within the soil profile. These processes should be similar between SDI and CPI if the preceding treatment processes are the same.

12 Machine damage [for SDI] is more manageable as smaller areas can be targeted and it is easier to rest areas before harvest,

Noted. Note that variable rate irrigation proposed for CPI.

VRI will provide some flexibility in this regard, but accept that SDI has more flexibility to target areas directly. However once SDI is installed there is no flexibility to adjust application rates within a zone, whereas VRI can be changed relatively easily.


Design Report Ref



Proposed steps: Recommend early discussion with Enviro Southland. Ensure comparative advantages are understood and explained along with areas of reduced risks. There is no need to allow for loss of hydraulic performance as the multitude of small fields give sufficient flexibility to cover eventualities.

Noted for consenting phase.

S. 7.18.4 Minimum irrigation area. We have no difficulty with the logic behind the 44.3ha stage 1 area. The Stage 2 area can be confirmed based on Stage 1 performance and is unlikely to be more than 55.4Ha.

Noted. Agree – if the soil hydrology can cope with the increased application rate over the smaller area.

S. 7.18.6 Minimum zone area. This does not need to accept 52 lps but could be designed for a smaller flow. However the ability remains to irrigate 52lps under Concept 3.

Agree, Stantec option 3 adopts this approach.

Agree

S. 7.18.9 Recommend 32 fields and could irrigate 1, 2,3 or 4 at a time in normal circumstances, or 5 if extreme flows are required.

Stantec option 3, similar. Detailed design would refine.

Agree

S. 7.18.9 Low Flows. The proposal allows for a probable 2 fields at once to irrigate low flows efficiently.

Noted. Agree


Design Report Ref



S. 7.19 Flushing. Drip lines using Wasteflow (or similar)

require< 0.2m/s flush rate. This is because of the non-mobile anti-microbial copolymer inner layer. We conservatively recommend 0.3m/s. Waterforce would probably be referring to standard ag dripline that does not have this feature.

A nominal 5lps is allowed for. Flush duration typically 1-2mins. This

allows for the removal of any settled solids at the closed end of the driplines.

Flush frequency. Expect that monthly will be adequate but more frequently is also practical.

Noted. Stantec option 3 similar and detailed design will need to refine.

Agree

Risks. Odour from field air valves is not an

issue on other schemes. Clogging from flush water is not an issue

elsewhere. The proposed storage tank provides flexibility and the reduced flush velocity and duration results in low flush volumes.

Kepler ww will be septic. Allowing for odour treatment is consistent with CPI comparison.

Treatment processes at other sites are different to that proposed for Te Anau. It is not acceptable to simply base the expected performance on “other schemes”. My understanding of the comparative SDI schemes at Pauanui, Omaha and Tiwai is that the disposal fields are within 2-3 kilometres of the WWTP, not 17 kilometres which will be the case for Kepler. Septicity in the pipelines is a risk.

S.7.19.1 It is not practice to flush dripline, submains and feeder mains. Providing there is ability to flush each field the submains to that field are also flushed by the higher velocity and flushed material is moved toward the closed end for ultimate removal in future flushes. Similarly with the feeder mains. The system does however have the ability to undertake more focussed flushing if required.

Noted. Option 3 layout includes ability to flush inlet manifold (before driplines) to waste.

Agree


Design Report Ref



P Riddell email Fri 11/05/2018 4:17 p.m. S.7.5 The ultimate size should be for the ultimate

SDI flow. As stated previously SDI does not require 52lps (4500m3/d). The main determinant of the peak flow is the need for pipeline flushing. With the smaller pipe this is of the order of 40lps. Another variable is the flush duration. For example, a membrane of 3,000m3/d could fill the storage tank which supplied the irrigation pumps and when full the pumps could operate at a required flow of 3600m3/d to scour the line. The difference of 600m3/d or25m3/hr would allow a 100m3 tank to draw down over about 4 hours. This requires some attention to optimise. In particular the flush requirements including duration and frequency when the water is of membrane quality as compared to unfiltered pond water should be clarified

Updated Design Report confirms SDC requirement for 250mm pipe and 52 L/s. This logic may be useful for shorter duration flushes. The updated Design Report confirms that 3-4hr duration flushes will be occasionally needed for any accumulated air.

Pipe size should be the same for both SDI and CPI. Allowance for balance storage has been increased to cover possible restrictions of CPI application during extended wet weather events. It is expected that detailed design will allow for optimisation, but essentially the scheme must dispose of the flows expected from the growing community. Linear infrastructure should always be sized conservatively where possible. The relative increase for the additional diameter size is nothing compared to a replacement pipeline if future flows exceed expectations. Selection of SDI or CPI will not change the incoming flows to the WWTP and should not impact the decision on pipeline size.

S.7.5 The second influence on membrane size is the irrigation flow as determined in NTC29. This is nominated as 3,600m3/d however we believe that for an intermediate (stage 1) flow this is excessive as it does not utilise a reasonable amount of the available storage for what is actually a reasonably extreme event.

Membrane infrastructure will be sized for ultimate capacity but staging of membrane module installation is possible.

Agree that staging of treatment infrastructure is an option and should be optimised through detailed design and procurement phases.


Design Report Ref



S.7.5 We consider more work is required to refine NTC29 and to also check relative to CPI operation, however in the interim an expandable 3,600m3/d membrane could be allowed for. This would eliminate the need to provide additional storage for pipe flushing. It should be noted as an item requiring more detailed investigation in terms of NTC29 frequency assumptions and the use of available storage.

For fair SDI/CPI comparison, an extra $300k (incl P&G etc) has been added to the CPI Additional Storage estimate.

Refer previous comment about allowance for additional storage for CPI. Whilst the exact configuration of storage versus disposal at Kepler is still to be defined, the additional storage allowance for CPI is a fair reflection of the potential benefits identified by Ecogent relating to irrigating for longer periods during storm events.

S.7.5 We note that membrane filter modules are expandable to accommodate flow increases allowing for more modest future costs than if a new membrane skid unit was installed for stage 2.

Noted. See above. Agree and applies to both SDI and CPI options with membrane filter.

S.7.5 Effect of returning backwash to ponds. Our experience at Omaha where backwash has been returned for probably 20 years is that it has not been an issue in terms of pond performance. It may be useful to consider utilising one of the small ponds to receive the backwash as a location to consolidate solids.

Noted. No additional cost has been added to the MF estimate for sludge affecting the ponds.

Agree


Design Report Ref



S.7.5 Mechanical failure. There should be adequate storage to allow for any short term mechanical issues. However we would note that there is no reason why as a short term expediency the membrane cannot be bypassed. The SDI field is protected by 120 micron self-cleaning filters and it is quite practical to install a standby filter at the membrane as an emergency bypass filter system direct to the membrane discharge tank for pumping to Kepler.

Noted. Although it’s felt the 15,000m3 Additional Storage should be sufficient for the duration of mechanical events.

I recall that Pauanui has an offline storage pond where off-spec effluent bypasses part of the treatment process, is stored until it can be returned to the start of the treatment process. This could apply to both mechanical failure or inflows exceeding treatment capacity. Pauanui also has high rate infiltration areas where high flow discharges can be made to cater for extended wet weather periods or to clear storage. SDC should consider the possibility of a high rate infiltration zone at the Kepler block or possible managed overflow bypass to the river should conditions exceed design expectations. It is standard design practise to have a “safety valve” on a system to protect infrastructure. If the main pumps, pipeline or irrigation system is out of operation for extended periods for any reason then storage at Te Anau could be exceeded. Allowing it to simply overflow without a controlled discharge path puts the entire storage pond structure at risk and would not be acceptable. All waste flows have passed to the lake in the past, I would expect an extremely rare event in emergency conditions would be an acceptable and safe solution.

P Riddell email Fri 11/05/2018 12.39 p.m.


Design Report Ref



S.7.16 We attach a quotation and specification (NZ Municipal WW project-Outlook file) for suitable filters from Triangle, a supplier we have used many times. Also included is the same for control valves at the filter and to the storage tank. Ref the headworks drawing (Eco -02.3) sent previously and also attached here. Note that the filter size could be optimised as we have a high flow set however it’s a good indication for you. It also includes a pressure relief valve discharging from the mainline to the storage tank which is a cost effective additional surge protection device for the mainline.

Noted. Will be referred to for detailed design if SDI selected.

Agree

S.7.16 We suggest that flush water from the filters and the field is collected in a small tank. It is practical to have a dedicated irrigation system including pump, filter and disposal field pumping settled decant water to an adjacent irrigation field. Typical size 300m2. Similar to a household size system. The pump suction could be located at about one third of the way up the tank wall leaving the residual for settled solids that could be tankered away if required. A higher flow dripper, 4lph (noncompensating) could be used as it is more tolerant to high solids load.

Noted. Although the concept doesn’t presently include this, options for flush water disposal would be revisited as part of any reconsenting.

Cost estimate should allow for management of the flush flows.

S.7.16 Risks Blockage from pipeline sloughing unlikely to be an issue because of improved quality of membrane treated water and redundancy in the two irrigation filters.

Noted. No extra physical works proposed to address this risk.

Agree and applies to both SDI and CPI options with membrane filter.

Screen size is the recommended 100- 120micron- not the basket type referenced in 6.16/Risks.

Agreed. Agree


Design Report Ref



Backwash holding tank size. We suggest it is increased for example to 25 m3 or a low profile above ground tank. This allows settlement for irrigating the decant water and storage for solids to be tankered away if required. Tank does not need to be buried but low profile is preferred.

Above ground tank budgeted for. Agree

We note there is adequate experience with large schemes and these issues

Noted. Agree

S.7.16.2 Eliminating Flush Storage Tank

This may be a possibility however the proposed system is reasonably cost effective and has no difficult permitting issues.

Noted. Agree


Price Quoting The information below was supplied to Ecogent by Gary Horton of Triangle Waterquip (Australia). Email of 10 May 11.48am System Criteria:

Water Source: Treated Municipal Waste Water.

System Flow: 190m3/hr, Operating Pressure: approximately

600kpa. Equipment Proposed: Filtration:

Filtaworx Fully Automatic Self Cleaning Screen filter Model – Product Code FW200-EL -100 (120) screens.

FW200: Connections: Flanged Table “E” Body Material of Construction: 304ss

Flow Rate: 300m3/hr Filter Area: 8114cm2 Controls: Electric. List (retail)Price: A$26-650-00 each filter

per filter Note: In sub surface Wasteflow applications we would always use 120 mesh screens. Hydraulic Valves. Hydraulic valves to be plumbed for pressure reducing and pressure sustaining. Valves to be plumbed with 16bar diaphragms, plumbed with 8mm polyethelyene tube, 3 way control tap and pressure gauges fitted. Item 3. Surge protection valve we will quote a quick relief valve; Relieves or vents the pressure quickly to atmosphere from a pipeline when it reaches a pre –set maximum level. This is designed to protect pipelines and systems from over pressuring.

Noted. Forwarded by Ecogent for information, and to support general layout comments.

Agree


Design Report Ref



Valves: 200mm (8”) Flanged Table “E” Cast iron 16bar diaphragm – Pressure gauges included. Valve Code: VH200-PR-PS-3W List (retail) Price: A$5,922-00 each Valve. Valve Code: VH200-PS-3W (pressure sustaining only) List Pricing: A$5,024-00

Surge Protection valve/ Quick Relief valve This valve would only need to be 100mm flanged just Teed into the mainline and directed back to the surge protection tank Valve Code: VH100-QR List Price: A$1,339-00 Availability: Filters Ex stock subject to prior sales. Valves 10-12 weeks (shipment ready to leave)

P Riddell email Fri 11/05/2018 12.39 p.m. Comments on 5.3.2/3/4. Design Capacity

S.5.3.2/3/4 Design Capacity

SDI doesn’t require the same peak flow of 4,500m3/d as it doesn’t need to cease irrigation and then need to catch up. I noted yesterday the advantage of having a smaller pipe (225mm) in terms of Capex, ability to get scour velocity at lower flows etc. This size pipe can however also operate at 4500m3/d if essential, but you would not bother with that pump capacity initially.

Updated Design Report confirms logic for 250id pipe and 4,500m3/day.

Catch-up may not be just due to wet weather, there could be equipment failures that require storage that needs to be cleared in appropriate time. Confirmation of soil properties that are so different for SDI over CPI application is required before I can accept that the same hydraulic load (or greater for SDI) do not have a similar impact on soil saturation. If SDI is installed within the gravels then the inferred treatment identified in the Hydrus model may be misrepresented.


Design Report Ref




I have modelled various historic flows and rain into the ponds and the required storage and provided that information previously. It demonstrates that SDI has a greater safety margin than CPI when it comes to storage requirements in specific events and conversely a smaller discharge requirement. The debatable factor however in the comparisons is the extent to which CPI must be curtailed due to ponding. I have made estimates based on my observations of photos and contours. The information you have used as created in NTC29 makes assumptions for SDI but does not address the relativity for CPI. This should be elaborated on in a Risk comparison matrix. You have also somewhat addressed it in S6.2.1- Further comment.

Noted. Refer s2.1of the updated Design Report that shows how this difference is allowed for. Further modelling of Additional Storage volume is underway.

I disagree that SDI can improve the hydraulic performance of the system to such an extent. Disposal is driven by the incoming flows which can be balanced in storage. If the soils are suitable for irrigation, as identified when selecting the site, then there should be minimal difference between the application methods for a similar hydraulic loading. Higher instantaneous application rates at the end of a pivot may cause short term surface ponding, but indicative infiltration rates do not support this. SDI may offer some opportunity to irrigate for longer once soils reach field capacity. But at some point they will reach saturation and surface ponding will occur. I anticipate the benefit could be 2-3 days which is reasonably covered by additional storage allowance in the CPI estimates.


Design Report Ref




In terms of future proofing for after 2042, the options are additional pipeline or booster pumping. Peak flow requirements with SDI are less because of there being no need to cease pumping and the consequent requirement to catch up at a greater rate and that needs more attention. However the more likely option once the advantages of SDI are appreciated is that land near the ponds would be used for future expansion. We have seen this at Omaha as the scheme has expanded over 30 years. This would provide more cost-effective expansion options with potentially one or more small additional areas unlikely to be available to CPI. In our experience, once SDI performance is observed, the resistance to new Consents is typically minimal compared to overhead irrigation.

Updated Design Report confirms logic for 4,500m3/day. Also refer s2.1of the updated Design Report that shows how this difference is allowed for. Noted, but cannot be relied upon. A consented site is extremely valuable, and AEE investigations for any discharge method are very expensive.

Again, treatment processes at other sites are different to proposed, with a better quality effluent. The additional areas available for application to land are also more appropriate, as mentioned previously Omaha and Pauanui are large sand dunes. There are other options to consider in the future, including a hybrid approach that has both CPI and SDI fields, reduced inflow and infiltration, improved treatment and recycling options etc.

S.5.3.3 It would be useful for you to provide guidance on the reduced demands likely on duration of flushing due to the high quality membrane water. A comparative table of the two water qualities would help people to understand the difference. Some rational for 4 hours would be useful.

Comment added to Design Report that the 4hrs is for air flushing rather than sediment.

Agree that air management is the main consideration for the length of pipeline flushing.

S.5.3.3 SDI Flushing does not need flows of 52lps. As noted in the irrigation design the flush flow is approx. 5lps per field and only one field needs to be flushed at a time.

Option 3 adopts this. Agree – this affects SDI field design, not pipeline flushing flow requirements.


Design Report Ref



S.5.3.3 The minimum flush flow of 0.3 to 0.4m/s advised by Waterforce is actually higher than required for the Wasteflow product used in the other NZ systems. This is not crucial but is worth correcting the record. I will address that in the Irrigation Design notes.

Noted in Basis of Design report. Agree

S.5.3.3 While SDC may like to build more safety margin into the system i.e. more than 4,500m3/hr this raises two issues. First it is important that the SDI

concept is not lumbered with the costs of some of the restrictive issues related to CPI. (Higher flows due to restrictions imposed by excess rain, flooding and wind and the need for it to ‘catch up’)

Second its important to home in on the uncertain details that are leading to such statements. In our experience determining the extent of storage required to compensate for periods when irrigation cannot occur is a very complex issue and often not successful.

Noted. Refer s2.1of the updated Design Report that shows how this difference is allowed for.

Agree with allowances in the cost estimates. Understanding the soil properties in more detail will be critical to assessing the risk of potential irrigation restrictions. However, I understand from the analysis of the various sites, that the soils at Kepler are relatively free draining, with underlying gravels, hence selection as the preferred disposal site. Wind issues could be minimised with longer droppers, different sprinkler types, mobile drippers etc.

S.5.3.4 Future Capacity

As stated above SDI leaves many options open for future capacity. It is unlikely to require additional treatment as below ground irrigation removes many constraints and the membrane filtration provides a high quality wastewater.

Noted. Agree, but membrane filtration and other treatment processes could be added to improve CPI application and remove the perceived constraints.


Design Report Ref



S.5.3.4 Future Capacity

The realistic option for 6,000m3/d would be irrigation of the increased volume close to the treatment ponds. Options would be Council parks and reserves or agricultural land. There is adequate time available to Consent such increases and the experience from SDI is likely to result in a simple future consenting process. We suggest that future consenting of an increase in CPI will not be an easy exercise.

See above. A consented site is extremely valuable, and AEE investigations for any discharge method are very expensive.

Adding future areas of SDI could occur regardless, installing CPI at Kepler does not exclude other forms of disposal at other sites if consents can be obtained.

P Riddell email Thursday 10 May 2018. 4.06pm

Further Comment on Pipeline size, Kepler balance tank and Booster pumping

S.7.13, S.7.14 Reduce pipeline size by 1 diameter to nominal 225mm. The reason is the reduced peak flow requirement for SDI and the ability to maintain your required pipe flushing velocities but at smaller flows. There would also be capital cost savings

Discussed above. 250mm is the minimum size and the estimate now allows for the CPI/SDI difference.

This is not an option with the expected inflows to the WWTP.

S.7.13, S.7.14 Retain the mainline control valve with similar functions as described.

Noted. Agree

S.7.13, S.7.14 There is the opportunity to direct on-line irrigate without Kepler repumping. A booster pump would only be used with the pipeline flush requirement. This leads to a simple system with associated power savings.

DoL irrigation not preferred, as mainline hydraulics have been carefully considered and are already quite complex. DoL irrigation would likely also cause an increase of pressure class for significant sections of the pipeline.

Agree with the complex hydraulics. There may be an opportunity to optimise this for both SDI and CPI (with additional membrane filtration or storage). Comparative costs for the business case seem reasonable.

S.7.13, S.7.14 With the proposed irrigation layout the irrigation flows are approximately 11,22,33 and 44 l/s for 1,2,3 and 4 blocks

Noted. Agree

S.7.13, S.7.14 At low pond inflows and levels irrigation would typically be 1 or 2 blocks at a time. Most probably the default would be 2 fields and a flow of 22lps.

Noted. Agree


Design Report Ref



S.7.13, S.7.14 The main supply pump receiving water from the membrane treated water tank would supply water to the Kepler with a pressure at the main control valve at Kepler of approx. 4 bar, sufficient to pass through the irrigation filters direct to the irrigation field. The Hydraulic grade line would be similar to that shown for the 26lps/ 250mm pipe but with a slightly higher discharge pressure. 2 Valves or irrigation fields is equivalent to about 1900 m3/d. If pond levels were increasing then a third irrigation field could be irrigated at the same time and pumped flow increased to 33lps. This will ensure that with the exception of mainline pipe flushing all irrigation water will be pumped with a single efficient pump system without repumping.

DOL irrigation not preferred, as mainline hydraulics are already quite complex. An increase in pressure in pipeline from Te Anau could likely require an increase in pipe pressure class rating of significant sections and hence price.

Refer earlier comments. Optimisation could be considered during detailed design.

S.7.13, S.7.14 We suggest that for pipe flushing (at 1+m/s) or for irrigating 4 fields at once (44 l/s) a storage tank and irrigation pump set be installed. A branch line from the mainline prior to the main control valve would lead to the storage tank (nominal size 75 m3) and an irrigation pump set capable of approx. 45lps would be supplied from the storage tank. The irrigation pumps would discharge water back into the mainline, downstream of the mainline control valve but upstream of the irrigation filters. A second control valve would be provided on the inlet to the irrigation tank. This would be automatically opened thereby diverting the main pipeline flow when pipeline flushing was required

DoL irrigation not preferred, as mainline hydraulics are already quite complex. Ecogent’s proposal appears to be a similar scope/cost to the Stantec proposal.

Refer earlier comments. Optimisation could be considered during detailed design

S.7.13, S.7.14 The irrigation pumps could be controlled by water level in the storage tank.

Noted Agree


Design Report Ref



S.7.13, S.7.14 In pipe flushing /irrigation pumping mode the mainline valve would be redundant and would be closed as it sensed the low pipe pressure.

See comments above Refer earlier comments. Optimisation could be considered during detailed design

S.7.13, S.7.14 This concept provides the ability to pump all irrigation water via the irrigation tank if required but given the power savings potential it seems prudent to allow irrigation without repumping for the bulk of the irrigation flows.

See comments above Refer earlier comments. Optimisation could be considered during detailed design

S.7.13, S.7.14 We record that conversation (PR/RO) following this email identifies the concern of RO that SDC would want a future proofed pipe size. As noted we believe that more detailed analyses will confirm that the smaller size is adequate for SDI. However, we also note that the irrigation and headworks layout is independent of the pipe size and the concept of normal irrigation be without booster pumping and that only pipe flushing flows would be diverted to the storage tank for repumping. This saves on OPEX costs of pump power. We also note however that the requirement for the large diameter pipe, and the requirement to pass all water through a membrane results in unnecessary membrane and pump CAPEX.

See comments above Refer earlier comments. Optimisation could be considered during detailed design. I understand that all flows would need to pass through the membrane, it would not be acceptable to pump bypass flows direct to the SDI system.

7.14 Specific Comments

Tank purpose. Evens out flows. This is a minor issue under the proposed regime as described however it does provide buffering as the flush flow ramps up.

Noted. Agree


Design Report Ref




There is no need to provide buffering for SDI flush flows as the flow change is minor. Eg with two fields operating at 22lps the flush flow is an additional 5lps for 2 or 3 mins. This variation should not be an issue with the low mainline velocity (approx. 0.6m/s at that stage.)

Noted. Detailed design will refine tank sizes. Balance tank sizes/cost are equivalent between SDi and CPI

Agree


The use of the tank avoids the need for excessive pipe pressures during flushing.

Noted. Agree


Simplifies pumping and pipe control. There is no significant difference in the control philosophies other than a dedicated irrigation program to coincide with the flush. We note the same must occur with CPI but with the added requirement to confirm that ground conditions allow all 3 irrigators to operate for the flush duration.

Noted. Agree


Required for CPI? We note that balancing must also be provided for CPI and is expected to be at least a similar if not greater volume.

CPI balance tank will have odour treatment. CPI estimate increased to allow for similar balance storage.

Agree

7.14 Key Risks None that are evident. The flush program is predetermined. It is less weather dependent than for CPI. If there is a problem with inadequate storage then level sensors in the tank will advise and the pumps at the ponds will back off to a nominal irrigation flow, the branch diversion valve will close the Kepler irrigation pumps will reduce the level and cut out on low level allowing normal direct on-line irrigation to continue.

Noted. Control functionality that should be dealt with at detailed design


Design Report Ref



S.7.13.2 Comment on complexity of stopping and starting SDI pumps and effect on management of the Control Valve. These are typically VSD driven. They do not need to change rapidly as in the mainline pipe flush mode they would operate at one predetermined flow (4 fields being irrigated) and as different fields were irrigated say every 20 mins then the sequence would be that the 4 valves would close slowly in sequence being replaced by 4 new valves opening in sequence such that 4 were open at any one time.

Noted. Control functionality that should be dealt with at detailed design

S.7.14 Odour Risks

Will be minimal due to the high quality of the membrane filtered water however a small filter can be included. Maximum air flow capacity equivalent to the water flow of 45lps as the tank fills. Carbon filter is suggested. Fan unlikely to be essential. Air inlet valve also required to replace irrigated water when system closes.

Noted. Approach consistent with CPI. Fan recommended by odour specialist

Agree

P Riddell email Thursday 10 May 2018. 3.03pm

Some specific comments on the Feedback Items on the draft SDI report as advised by Stantec in the email appended below. Note

some additional comments added since earlier email.


Design Report Ref



S.5.3.3 Flushing Flows

Remember that for SDI the membrane treated water has minimal TSS so sediment flushing requirements are reduced for the SDI option. As mentioned it is not my place to question your pipeline design detail, flush velocities etc however I note that for SDI it is practical to reduce pipeline nominal size to 225mm. This has advantages, particularly for SDI on which I will elaborate in a later section, but also aligns with the proposed mitigation of risks under 6.10 .

Noted and discussed above Air management is the main driver for pipe flushing, not sediment. Membrane filtration also an option for CPI.


Design Report Ref



S.7.7 Biofilm Control Dosing for Transfer Pipeline

This is not essential for SDI. Under the SDI option high quality membrane filtered water and regular high velocity flushes are proposed. The SDI is protected by 120micron irrigation filters. We do recommend having the ability to dose Hypochlorous acid into the irrigation system upstream of the irrigation filters and we would propose a generating system be included at the irrigation headworks shed for that purpose. The purpose of this is to restrict biomass growth on filters and control valve and associated filters and we know from other projects (both Omaha and Maketu) this reduces maintenance on valves and filters (it is not needed for the SDI pipe or emitters as these have antimicrobial linings for that purpose). In the long term we suspect that when the benefits of this are noted it is likely that using the same product to control the growth of Biofilm on the main pipeline will an obvious extension and at that point the product could be trucked to the ponds for adding to the pipeline. An indicative design for the pipeline would suggest that a similar to the dose rate for drinking water, say 0.5ppm but added

Deleted from scope Agree

S.7.17 Agree this is incorrect. For biofilm control management we recommend using hypochlorous acid as noted above. Regarding Trifluralin for root intrusion management I have sent you a note on this to clarify.

Noted. See new s7.19 regarding root intrusion control.

Agree


Design Report Ref



S.7.17 Requirement to update model (NTC29) to stop SDI as a precaution when surface runoff in an extreme event is occurring. In our opinion providing there is care taken when designing the SDI and ensuring that the depressions or water courses do not run through fields there will be no need to ever cease irrigating in extreme weather. I referred previously to the need for a more detailed survey at the design stage identifying these features. The irrigated wastewater will only reach the surface through capillary movement providing our pulsed irrigation recommendations are followed and there will be no measurable mixing of irrigation and surface water. On that basis it is unlikely to be infringing a Consent.

Noted. However a precautionary approach is to assume that SDI would need to pause in extreme events, if only to allay concerns of the local population and regulator.

Refer earlier comments about soil saturation. Regardless of the application type, the accumulation of rainfall and irrigation, less drainage, will exceed the soil storage capacity and surface ponding will occur. It is possible that SDI could extend the irrigable period for 2-3 days but I would not be comfortable with any further benefit in this regard. I visited site on 30th July, after 25mm rainfall in the preceding four days. Whilst the gateways and “bog” area were still very wet, the remainder of the site was easily trafficable with no evident tyre depressions left behind as we drove around. The general contour of the site is flat with undulating depressions forming potential channels for surface flow. At the time it was difficult to visualise these depressions as “water courses”. However, the inconsistent direction of these depressions will likely require some adjustment to the proposed grid layout of SDI if there is to be no low areas through the fields.


Design Report Ref



S.7.17 I also note in NTC29 that the assessment of SDI peak flow for design is based on events which I consider to be a greater magnitude than the assumed 10 year return period. The requirement to then use only 5000 of the available 15,000m3 buffer storage results in a disadvantaged outcome for SDI as it is a small buffer storage volume for an extreme event. Key Issues: An assessed 10 day 250mm rainfall

considered to be a 1 in 10yr event. I am not in a position to comment on the derivation of this figure.

The decision that the prolonged rain event coincides with the peak 10 day Xmas flow- this increases the frequency of the event to more than 10 years

The additional 1.15 factor to increase the flow in case the rainfall isn’t a 10 year event.

The total of these three factors results in a storm which will be greater than a 1 in 10 year event.

Further modelling underway. Section 2 of updated Design Report adds scope to CPI to provide fair comparison. We stand by the methodology in NTC29. However further modelling is been undertaken to confirm how the buffer storage will be used. Initial results, based on soil moisture infiltration capacity, suggest that the buffer storage is adequate.

The requirements for storage to manage inflows to the WWTP should be consistent between the SDI and CPI systems. At this stage I am not satisfied with the information available that SDI offers a dramatically improved ability to irrigate the Kepler block through winter conditions than CPI other than the 2-3 days previously commented on.

The decision is then made that only one third or 5,000 of the 15,000m3 of the storage can be utilized because this is only a 10 year event.

Noted. See above comments


Design Report Ref



If half of the remaining 10,000m3 storage was used then that would reduce the required flow by 500m3/d to 3100m3/d. If all the storage was used the required flow would further reduce to 2,600m3/d. These ad hoc design considerations have a major impact on SDI system costs and require a sounder basis.

Noted. See above comments

For the comparison of how the two forms of irrigation can deal with extreme events it is important that some commonality is used. For example I have previously provided photos showing prolonged flooding of part of the irrigation area. However this occurred following a much smaller rain event, less than 150 in 20 days compared to the 250mm in 10 days that has been applied to the SDI design.

Section 2 of updated Design Report adds scope to CPI to provide fair comparison.

Agree with comparison basis for business case at this stage. But we need to resolve the future peak flows and storage requirements that will form the basis for detailed design. If the photos that Ecogent continue to refer to are equivalent to a 1 in 2 year event as inferred, then it questions whether the site is suitable for irrigation at all. Soil assessment and site visits after extended periods of rainfall indicate better performance than the photos elude to.


Design Report Ref



You commented that you had walked over the site after 40mm of rain and it was quite sound. My response is that 40mm on dry ground would typically not be an issue. It is the prolonged rain in excess of say 150mm on wet ground that appears to create the problems. There needs to be a better measure of rainfall frequency, flooding events and how CPI irrigation might be managed because this is a risk for Council that should be understood. Perhaps a more sound approach in terms of comparing the risks between SDI and CPI would be to agree to two or three extreme rainfall / flow scenarios and model outcomes for both options.

Noted. Further modelling underway, as noted above. The soil testing to date indicates a high capacity to accept flows.

It is unreasonable to increase the hydraulic load through SDI (same flow but on reduced area) and still expect the soils to remain unsaturated. If the SDI is installed in the gravels, which allows free draining capability, then the inferred treatment benefits of applying the effluent are reduced as the flows are essentially injecting to groundwater. At this stage I am not satisfied that we overstate the hydraulic performance of SDI over CPI, other than to reduce the application area on the basis of reduced N due to the membrane filtration and increase storage for the CPI option. I do agree that we need to fully understand the storm event being designed for, and the expected flows to the WWTP from this design event. Once this is firmly fixed then the comparison between SDI and CPI should not be so subjective.

S.7.19 Including Air Filters on SDI Flush Lines. It is not common to do this as it has not been demonstrated to be an issue on other schemes.

Included for consistent comparison with CPI, and stakeholder feedback. A consenting issue.

Minor cost, opportunity for optimisation of filters on air valves for both systems.


Design Report Ref



General. Provide Cost Estimate for CPI at the same 3600m3/d. The problem with this is the need that CPI has to be able to discharge 4,500m3/d for peak events. It reaffirms the need for an analyses of probable restrictions on the area that can be irrigated by CPI in extreme weather. I noted in the Hydraulics report S14.2 Pasture Irrigation that VRI was unlikely to be used for CPI. Is that correct? If so it raises difficulty for management of CPI in wet weather. I also found an earlier estimate I made of the cost of providing tracks over the bog. I measured 600m for all the wheels and a unit cost of $500/m for trestles and bridging. Disclaimer- a non-professional costing!

Noted in updated Design Report. VRI is budgeted for. Estimate updated, and disclaimer accepted. Alternative is splitting this CP into two units and avoiding the bog altogether. A similar cost.

VRI should be considered. I understand there is reasonable cost for tracks across the bog, although avoiding it would be preferable with an alternative layout. Costs for tracks or the premium to add additional centre point and pivot infrastructure are likely to be similar and not impact the business case. CPI could be staged by using a different sprinkler package to start with, replacing later as the irrigated area increases. CPI is also relatively cost effective per hectare to simply add the additional machine sooner rather than later.

P Riddell attachment of Stantec (R Oakley) email of 24 April


Design Report Ref



No response required. Included for info only. This email by Roger Oakley was to Peter Riddell, Ben Stratford and Ian Evans. Hi all. Attached is the Basis of Design Report. Its status is ‘Draft for Peer Review’. The intention is that the feedback received from each of you will be incorporated into an updated final version. Based on that final version, cost estimates will be prepared, and it will then be assessed in accordance with the Business Case. Ian Evans has asked for feedback by Friday 4 May. Ian was in Dunedin today and the report reviewed. Some initial feedback was received, as below, but a decision made not to update the report before sending it out. In this way everyone can be confident they are seeing the same information. Feedback is:

S.5.3.3 Explain the logic for the requirement for flushing flows for 4 hours. (Relates to flushing air between air valves, R Oakley will elaborate).

Refer earlier comments

S.7.7 Biofilm Control Dosing for Transfer Pipeline. Not clear if this is needed, so maybe this is a provisional item. Removing it would require more reliance on the irrigation filters (s6.16) after the SDI pumps.

Not required for the transfer pipeline


Design Report Ref



S.7.17 SDI Herbicide dosing. Should be renamed ‘SDI Biofilm Dosing’ and its only purpose is to control biofilm in the SDI field. The herbicide (root intrusion) function is performed by Treflan (or alternative) impregnation of the dripper lines, and should be commented upon in s6.18.

Agree

S.7.18 Subsurface Drip Irrigation. Need to model scenarios where SDI irrigation stops for some time period as a precaution when surface runoff in an extreme weather event is occurring. R Oakley to update the models in MWH NTC 29 with these scenarios.

Agree

S.7.19 Allow for carbon filters on the airvalves on the SDI flush lines. This gives fair comparison with the level of odour treatment for SDI.

Agree – cost basis needs to be comparable

General General – Cost estimate should allow for an initial stage of 3,600m3/day for CPI (if practical), if this is what is allowed for SDI. Will need to check this still achieves required flush rates.

Agree – cost basis needs to be comparable and staging is potentially an option for both SDI and CPI

P Riddell email 9 May 2018 Hydrus Model and Aqualinc Memo

(Responding to R Oakley response email of 9 May 2018, 5.28pm, to the email below) The point was raised solely because it affects Hydrus leaching calcs which should be aimed at probable operations and the 4 hours non pulsed would not be typical- a bit like stopping the CPI but continuing to irrigate. I agree there is lots of flexibility with the final install.

Flexibility in control functionality at the disposal site should be considered through detailed design.

P Riddell email 9 May 2018. 5.01pm Some further thoughts about the Hydrus

modelling


Design Report Ref



The 8 litres per dripper (mentioned on Page 2 of the Hydrus report) is a very high irrigation figure and not representative of what’s likely to happen. It is equivalent to 10mm over 4 hours on the 0.8 x 1m spacing which is about 3 times the average WW application for the year as listed on Table 2 of the Aqualink report. It’s important that both the frequency and depth of irrigation reflect likely conditions for comparative purposes. I raised the issue of the need for frequent small doses in the previous email. I didn’t add that some practitioners advocate even greater frequency but smaller volume doses to maximise soil treatment. The limitation becomes the hydraulics of the irrigation system.

Responded to in R Oakley email of 9 May 2018, 5.28pm.

Agree

P Riddell email 4 May 2018. 11.54am Additional Modelling

It is important to model something approaching a probable operation which would be 20 to 30 min irrigation duration so 8 daily applications per area for 30mins or 12 for 20 mins. This provides a more realistic picture of soil moisture profiles and reduces the excessive leaching resulting from a single 4 hour dose.

Included in Hydrus brief. However note previous comments that also provide limits on minimum SDI area.

Agree

Additional Modelling

From the Hydrus summary can you please get some answers to the following. (See the attached spreadsheet-Hydrus Summary- that puts CPI and SDI side by side for comparative purposes with the same flows and areas)

Hydrus brief is principally for side by side comparison.

Agree


Design Report Ref




What factors are resulting in the high drainage for SDI that then lead to the conclusion that more area is needed. See the attached spreadsheet. I cannot see how the highlighted figures for SDI drainage are obtained.

New Hydrus work will supersede this. If SDI is installed close to the free draining gravels, with no risk of reaching the soil surface, then I wold expect drainage to be occurring rather than treatment and plant uptake. Pulsed irrigation cycles are expected, but if the soils are saturated due to the incoming hydraulic load from irrigation and rainfall (note this is already 20% higher for the SDI system), then the water must move either to the surface (ponding), or direct to drainage.


My earlier comments on how Hydrus deals with different forms of N.

Noted. Refer to comments below.


And leading from that did Overseer recognise different forms of N in the original modelling

Understand that Overseer assume immediate conversion to nitrate.

I understand Overseer does not differentiate forms of N.

P Riddell email 4 May 2018. 11.54am Re: Hydrus model and Aqualinc memo


Design Report Ref



I appreciate the single page summary doesn't include the entire farm but at least it provides figures higher than when the larger area is included so it’s a good start and an easy final correction. I am pleased you sent it because it made it easier to get the big picture. I looked back through the commissioners’ decision to try to identify what form of N was used in Overseer. Pre the BTF for odour reduction it was substantially ammonium. I noted the model was run as a comparison with Taupo which also was predominantly ammonium. When it was rerun after inclusion of the BTF it is unclear whether the transformation to nitrate was included. I don't have access to the detail and it was complicated by the annual flow being more than halved by considering actual rather than consented flows. It would be good if some clarity could be obtained over this. I agree re Hydrus and relativity of CPI and SDI. Extending that further it would be good to get the answer re the overseer comparison with ammonium vs nitrate. The reason is that there should be clear advantages with ammonium in terms of leaching and if SDI was considered then it would be good to understand how overseer would model that difference in N type.

Advice from Aqualinc is that specific empirical calculation of the effect of different form of N is not possible. This makes it difficult, when consenting SDI, to gain specific recognition, such as via a reduced SDI field area. It is accepted that the ammonia form of N is an advantage and this is listed in s9.3.

Transformation of forms of N through the BTF are not my specialty, however it appears there may be an opportunity to consider the treatment process to ensure the predominant form of N is ammonia through disposal at Kepler. Ideally reducing the incidence of drainage will ensure either form of N remains in the soil profile.

R Oakley email response 2 May 2018, 4.31pm


Thanks for your comments, and I hope that the flu bug is wearing off. It would be good if we could talk over the phone on this, at least to get as much consensus as possible, as it can be difficult to get clarity over emails. However, as general comments in response to your email below: Yes, it seems generally accepted that shorter doses are much preferable than a 4 hr blast. I think the Hydrus report suggests that too. I think this may ultimately be an operational matter, as the scope and cost of the SDI infrastructure will be very similar (or same) regardless of dose duration. The single page summary is misleading, and I hesitated about forwarding it, but decided that everyone should have the same info. It is misleading in that the modelling to date only considers the wetted irrigated area, not the combination over irrigated and dryland areas, with regard to the consented 32kg/Ha/yr over the whole North Kepler Block. I am presently finalising a brief to Aqualinc to give a better direct comparison with CPI over the whole North Block. This topic is going to be a challenge going forward, as the present consent is based on Overseer modelling and ongoing reporting by Overseer. I suspect Hydrus will give different results, but in the first instance it is the comparison CPI/SDI that is important, rather than the absolute values. So to answer your comment, more Hydrus modelling is required to clarify matters.


Design Report Ref



I will check with Aqualinc re form of N. Your comment is noted. If it is to be taken into account in a consenting situation, then we will need to satisfy the consent authority with strong technical evidence to support a reduction of SDI area due to the form of N. I understand that this may be difficult, but is not an area I have expertise in. I think the above answers your comments in general, but happy to talk.

P Riddell email 2 May 2018. 3.33pm Re: Hydrus model and Aqualinc memo

Hydrus Modelling

Thanks for the info. The Hydrus modelling is as we expected as regards emitter spacing outcomes based on our observations and soil moisture measurements at installed sites. Could you ask that a 30 min dose is included if further modelling is done as in practice we have found 20 to 30 mins to be an optimal balance between treatment and system hydraulics. The 4 hour dose as used in the main Hydrus report would be a most uncommon operation and would lead to unnecessary leaching. Pulse dosing is the best way to optimise soil treatment.

Responded to in R Oakley email of 2 May 2018, 4.31pm. Hydrus will model shorter duration

Agree that pulse dosing will benefit application and performance of the SDI

Hydrus Modelling

I am having difficulty understanding the data in the second, single page, pdf results summary. Essentially it implies that the yields for SDI irrigation will be about 20 percent less than the yields for CPI for the same area and flow. I can’t find any substantiation for that in the report and it is contrary to experience and most literature.

Responded to in R Oakley email of 2 May 2018, 4.31pm

I understand the modelling has been updated to cover this.


Design Report Ref



Hydrus Modelling

I would also like to know about the form of nitrogen used in the hydrus model. CPI wastewater is primarily in the nitrate form whereas SDI would be substantially in the ammonium form. It appears that no difference has been assumed in the table. This is important because it means a greater portion of the winter applied N would be bound up for use when soil temperatures rose again thereby reducing winter leaching with SDI.


Form of N is important for the overall treatment performance of the system. However, based on continued insistence that the soils are at risk of ponding through CPI, I am concerned about the hydraulic load on the soils if we continue to reduce the area to which irrigation is applied for SDI. As the hydraulic load increases, if SDI is not to pond at the surface, there must be increased drainage which reduces the effective treatment of the soils, increasing N loss.

Hydrus Modelling

There are also some possible errors in the table particularly as applied to the last 3 columns of solute applied/uptake/drainage. I presume on an annual basis after the first year or two that this should be a closed system. I may be missing something here however it is important. For example I think the 37ha SDI 2016 should be 32 not 42 kg/ha, the 50ha SDI 2016 13 not 30 and the 74ha SDI 22 not 34. These are figures for irrigated areas not the whole farm. I stand to be corrected but it is important when the concluding statements are that 47 ha and 78 ha are needed for SDI.


I understand the modelling has been updated to cover this.

R Oakley (Stantec) response to Riddell email of 30 April


Design Report Ref



Hi Peter, and all. The two documents have been loaded onto the Sharefile site now. Aqualinc modelling of N leaching to date has only looked at the wetted area under irrigation, rather than the average over the whole of the North Block. I am preparing a short brief for Aqualinc to extend their present work to allow for both irrigated and ‘dryland’ areas. I’m not expecting this to affect the density of emitters, but it will provide more robust evidence for a reduced SDI area compared to centre-pivot. Also, can you include Ian Evans in on any group emails. Cheers, Rog.

P Riddell email 30 April 2018. 10.28am Hydrus model and Aqualinc memo.

Hi Roger, are you able to send the aqualinc memo and a summary of the hydrus model outputs. Regarding hydrus it sounds as though there is positive info however I am interested to know what the input nitrogen assumptions were. Regards, Peter

See R Oakley response above (30 April)

P Riddell email 11 April 2018. 6.23pm SDI Irrigation Flows (email to B Stratford

and R Oakley)

I just wanted to document my understanding of the issues relating to SDI area and flows.

1 We are using similar areas for cost comparative purposes at this stage.

Noted Irrigation areas have been reduced due to reduced N through the membrane filter. Cost estimates have been updated to reflect this.

2 Flows based on the SDI Design Note produced by Roger in 2016 which estimated an SDI flow of 4050 for the future and a suggested 3600 for stage 1 up to about 2029.

Noted Staging of both systems is acceptable.


Design Report Ref



3 Resultant areas at 6.6mm/d are 55ha and 62ha.

Noted, but updated by Option 3

4 Layout for comparative purposes is the stage 1- 55ha. Conceivable when stage 2 comes about more info has been collected that will allow the stage 2 area to be reduced- or not epending on other factors such as wastewater inflow trends, weather trends etc.

Noted, but updated by Option 3. Staging allows assessment of performance of the installed system with modifications made as required.

5 The membrane is thought to remove 20% of the nitrogen and this suggests potential to reduce the irrigation area by a similar ratio based on N budget. Work is required to confirm this. PDP looked at it and I think without checking my notes that they agreed with a 20 or was it 30% reduction. Data could readily be obtained from other systems and also tests at TeAnau.

Noted. 20% is the agreed figure. Agree for N reduction. However we need to carefully consider the hydraulic load on the soils through the wetter months as this will likely become the limiting factor for both systems.

6 I do not think from reading the evidence that the 6.5mm/d or 2.9 winter rate are hydraulic limitations, especially with SDI so if N application is the issue the areas could be reduced to 44Ha for Stage 1 and 50 for stage 2. This suggests that stage 1 could maybe have a shorter horizon allowing data to be collected over say 5 years to support a reduced next stage. Note that high rate areas are used at Omaha and Pauanui as a means to irrigate short term high flows.

Correct that 6.5mm/d or 2.9mm winter rate are not hydraulic limitations. Option 3 gives size for first stage.

Omaha and Pauanui are coastal sand dunes where there is a high drainage potential. If this is a possibility for Te Anau through Kepler gravels, then are the risks of surface ponding being overstated? This is a major contentious item and needs further support on the likely performance of the soils on site to both CPI and SDI applications.


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7 Hydrus seems a reasonable first step. I mentioned the fact that N is expected to be substantially nitrate after the BTF. This point was made in the evidence from the MWH BTF expert. Contrast is that Nitrate in SDI will be significantly less. Point being that nitrate leaches quickly in winter whereas ammonia is held, converted and used by the plant resulting in reduced leaching loss. I don’t think hydrus or overseer deals with this well. Quite a bit of literature positive about SDI nutrient uptake benefits. I will find some and send when I get back This is obviously a future matter for discussion with ES but point is Risk should be positive.

Noted, and commented upon above. Discussed in s9.2 of Design Report (Opportunities arising from SDI)/

Refer earlier comments about form of N. We need to be careful not to double count the possible N performance benefits of the SDI system. If these benefits, compared to CPI, are captured in the economic section through reduced area and longer run times through storm events then the same benefit cannot be counted again in another section of the business case.

8 Future monitoring - form and concentration of N in wastewater, in soil moisture, in aquifer below irrigation at the west irrigation boundary and in the crop

Aside from consent requirements, agree that monitoring will gather useful evidence for ongoing consenting.

Agree

9 As an aside I would like to encourage the growing of Lucerne- at least as part of stage 1. Reason is it grows well at the site can allow greater therefore cheaper row space and responds well to SDI. Recommended by local contractor and growers as a good crop in the area

Pasture type will be selected specifically to maximise performance as a ww scheme. Rye and fescue also have been proposed.

Agree that Lucerne could be a good option, particularly with a deeper root system that will assist in maintaining production during dryer periods with reduced inflows to the system.

10 Need to be able to deal with unexpected high flows. Eg prolonged 4,500m3/d due to extreme events. SDI can hydraulically handle that flow. Issue is to negotiate with ES prior to being faced with the decision to spill or irrigate in excess of the consent. SDI allows the irrigation option whereas CPI at the bets could only irrigate part of the area due to ponding

Noted. Discussed in various items above. Refer earlier comments about hydraulic loading. If the soils can handle the higher application rates through SDI then either there is more drainage occurring in the lower soil profile or there will be migration of applied water to the surface, causing ponding. Unsure what is referred to by “spill”, is this an overflow option at the ponds?


Design Report Ref



P Riddell email 11 April 2018. 1.05pm SDI Irrigation Layout

1. Revised Layout As discussed Monday we would recommend a different approach to the SDC layout concept for two reason. Better economy and flexibility of operation.

There is certainly opportunity for optimisation of SDI layouts, but I understand a reasonably efficient design basis has been incorporated in the cost estimates.

SDI Layout Concept

Economy comes from smaller supply mainlines and no large 52lps sized valves.

Other economies come from the potential for longer runs using nominal 20mm dripper line hence fewer submain connections

Flexibility is useful for various reasons. Greater flow flexibility, potentially from about 11lps with one block to 52lps with 5 blocks so can easily handle base flows, average flows and peak flows.

Does not rely on flushing to deal with the peak 52lps flow.

Flushing programs easy to run and can be organised for periods of normal rather than peak flows

Typically all valves normally closed and slow operating so compliment the main line valve.

Option 3 captures these points Agree

A typical layout could be 32 individual blocks and control valves. Each block discharging its flush flow through a non-return valve into a common flush mainline discharging to a storage tank. Flush takes place from whichever block is irrigating but only when the single flush valve opens. Nominal 25m3 tank adequate.

Option 3 captures these points Agree


Design Report Ref



Some specific recommendations for the SDI Pipe: Antimicrobial lining. This minimises slime

growth and only requires a flush velocity of 0.3m/s. NZEPA compliant and non-mobile.

Root intrusion protection by sustained release dripline impregnated trifluralin. This emits a vapour in the immediate proximity of the dripper. NZEPA compliant.

20mm nominal ID. 2.1 lph pressure compensating emitters at about 800mm spacings (to achieve the average 0.8m2/dripper you mentioned Roger from Hydrus . Effective row length up to about 300m. This allows a flush flow without excessive additional inlet pressure.

Aim for dripper flow of at least 2lpd to minimise blockage potential.

Flow to individual blocks. Block size 1.73 ha, 2.1lph drippers at 0.8m c/s flow 45m3/h or 12.6 lps

Flow variations. At low flow could operate at 12.6 lps, 2 at 25lps, 3 at 38lps, 4 at 50.5.

Additional flow to flush an individual block approx. 4.2lps.

Typical concept is to break into 4 groups of 8 blocks allowing flows to be spread out and pipe sizes reduced.

Typical block size up to 300m long and 58 rows at 1m spacing wide.

Updated Design Report and layout Option 3 captures these points, and further improves them.

Agree – SDI layout and equipment optimisation has been captured sufficiently to support the business case.


Design Report Ref



By comparison, the draft layout provided by SDC shows 7 x 7.92ha areas. Each area can take 46lps as an irrigation flow. The entire 7.9ha irrigates as one block but flushes in 5 zones as a flush valve in each zone opens sequentially. Flush flow that needs to be captured is 6lps. When flushing the full flow of 52lps is required into a single 7.9ha block. This layout requires 35 automated flush valves and a single approx. 200mm valve at the inlet to each zone. This is not the most economic layout as it requires large pipes and control valve to each 7.9ha block. It is also restricted from a practical aspect in that any problem areas within the 7.9ha, such as restricted drainage, maintenance, harvesting difficulty due to isolated soft soil etc. necessitate turning off the entire area.

Updated Design Report and layout Option 3 captures these points and further improves them.

Agree

An alternative layout concept is shown on the attached plans. It obviously needs more detailed investigation to optimise it and consider the ground contours and flooding etc.

Updated Design Report and layout Option 3 captures these points

Agree

Drainage Improvements

We would recommend minor drainage improvements to ensure each of the estimated 32 blocks does not incorporate any significant depressions or channels. The land between blocks can be modified to allow surface drainage to move away from fields. Blocks would not be located on the main drainage depressions. A concept is shown on the attached plan.

Estimate updated to allow minor drainage improvements.

Agree

P Riddell email 10 April 2018. 11.38am Restricted Irrigation Areas


Design Report Ref



First, Roger you mentioned that you had created a spreadsheet of the May 2016 storm and concluded that “there should be no difficulties for CPI in that event”- or words to that effect. Could you share that model as I think restrictions on the ability to irrigate in certain areas in storm times is a risk to both forms of irrigation but less so to SDI because of the potential to avoid locating dripline in the ponded areas. I have previously produced storage/irrigation models of various events to demonstrate the greater flexibility of SDI. The key issue I found to be is the estimate of when and how much CPI is feasible due to ponding restrictions. One of those models is in the Ecogent report in the shared file. You will note my assumptions regarding restrictions on irrigation which I think should be explored further.

Base daily data shared, of pond ww inflows and rainfall.

Refer earlier comments about hydraulic loading and the requirement for additional detail to support basis for further reducing the SDI area and increasing the risk of CPI surface ponding.

You mentioned that there were no photos showing flooding for prolonged durations. I have attached photos from 3/8/14, 11/8/14 and 18/8/14 showing perseverance of ponding in the depression south of the peat bog. Also attached is the rainfall record. 141mm over 21 days. These and other photos also highlight the site drainage channels.

Photos received, thank you. Budget estimate increased to allow for some site contouring.

We need to understand the reasons for this ponding, was it a 1:10 wet weather event, is it inherent soil and subsoil issues which would question the suitability of the site for irrigation, or is it localised surface capping due to current farm practises that can be rectified through cultivation, cropping, fert applications etc? My understanding is that generally the soils across the site are suitable for irrigation. My site visit on 30th July 2018 was after a wet July with a total of 161mm rainfall and we could still easily traverse across the Kepler block by vehicle.


Design Report Ref



Also attached is the photo from Enviro Southland showing flooding in an earlier event. I have highlighted the airstrip in red to assist orientation. The peat bog can be seen as can various ponded areas on the irrigation site.

Photo received. Peat bog would be avoided for any irrigation system. I would expect some surface contouring, drainage, cultivation, ripping etc. to further prepare the site for irrigation, much as you would do for any other irrigation development. Costs have been included for this preparatory work and should be supported by the additional soil property data requested in previous comments. Refer earlier comments about the storm event that is being designed for.

I had a quick go at sketching depressions on the contour plan based on observations from the photos. I haven’t time to put any detail into this but a site walkover and pre design survey should allow an accurate definition of the low areas and ephemeral water courses to be better defined.

Noted. Budget estimate increased to allow for some site contouring.

Agree with budgets for site works. The ephemeral water courses do not show any evidence of water migration, they are simply contoured depressions which appear to be easily farmed across. It is possible that the surface soils in these depressions are heavier and have slightly lower infiltration rates than the wider Kepler block.

When we consider the catchment of each area that has standing water there is obviously a large area draining to the ponded areas that cannot be irrigated for extended periods as per the photos as the consent requires no standing water for more than 3 hours. I have never seen any work done to identify this and define the extent of restricted areas and consider it should be recognised as a Risk issue.

CPI will have variable control. Ponding risk will be noted.

Agree The ponded areas from the airplane photo continually referred to by Ecogent will not practicably be avoided by either SDI or CPI infrastructure. Some soil surface improvements will likely be required for either system.


Design Report Ref



In conclusion I believe it is important that we identify the risk of reduced irrigation ability and the interaction with storage and consider how to minimise for both options. From the work I have done the 15,000m3 storage will be essential as demonstrated in May 2016

Agree


Table of Attachments from Ecogent

Rainfall Photos Kepler Site Contours Prelim Site Plan of SDI Irrig Zones Feb 2018 Layout of Block of 4 Fields Drawing Data from Hyrdus E. Control Pilot Adjustment & Setting 11. Pressure Reducing/Pressure Sustaining Valve with Manual Control D. Control Pilots Cast Iron Valves Electric Controller Drawing FW100EX Filter Assembly Drawing FW200 Water Filter Drawing SDI Headworks at Kepler Drawing Mainline Totals Control Schematic Outline Costs Control Schematic Site Plan of Irrigation Zones – Concept Layout Option 3


Ecogent Feedback of 7 June Stantec Response Peer Reviewer comment SDI Costs I agree with your comment about various ways to slice and dice but it is the big picture that is being lost here to the disadvantage of SDI. I have provided relevant costs based on other NZ systems, as well as a more efficient conceptual layout to reduce the component size, dimensions and cost from your original, but I feel to a large extent this information has been ignored.

Costing spreadsheet was forwarded to Ecogent and specific feedback received. Subsequent conference calls. Aside from any minor updates the principal outcomes are a reduction of dripline supply and installation cost, based on refined info, an adjustment of comparative CPI/SDI pumping costs at the irrigation site and reduced per m2 cost for the transfer PS building if MF included.

It is my opinion that the cost estimates have been updated with consideration of Peter’s comments. I agree that in previous versions the basis of unit rates varied between CPI and SDI and this has been corrected where applicable. It is important to note that CPI infrastructure is common throughout NZ and costs are well understood on a per hectare basis so it will be difficult to get an exact comparative basis without going to the market. However the cost estimates do need to have consistency between systems, for example building costs per m2 should be similar, pipeline supply and install rates should be similar etc.

SDI Costs On SDI in-field costs alone the estimates are arguably 50% higher than realistic at about $62,000 per ha. The cost indications we supplied were for other municipal or high risk commercial schemes (such as the Smelter where failure had a high associated cost and liability) and SDI beneath (not beside) the Pauanui airstrip being an obvious example of the need for a high quality installation. You may have noted from the supplied Ocala Airport paper that SDI in addition to meeting FAA requirements was competitive when operating costs were also considered. The point is that using more agricultural standards as is the case with the CPI system results in much lower scheme cost so the comparison is not like with like. The CPI costs are based on current agricultural prices from Waterforce yet the SDI is a very conservative costing and industry-standard concepts appear not to have been applied.

A more refined estimate for dripline supply and installation has seen this cost reduce. Regarding agricultural standards, this can only apply to the centre pivot units themselves, as everything else is specific design. Standard CP units are appropriate as there is redundancy and easy maintenance access.

Agree


Ecogent Feedback of 7 June Stantec Response Peer Reviewer comment SDI Costs In addition to the infield costs there are glaring examples where the comparisons are not realistic. They include, but are not limited to • A shed for the SDI pumps but not the CPI pumps. • SDI pumps and pipework that costs 3 times as much as the CPI pumps but irrigate similar flows and pressures as CPI pumps with cleaner water. • Excessive costs for the filters including duplication. • The same cost as CPI for the main pipeline pump station at the ponds yet the SDI pump station is above ground from a tank after the membrane and should be similar to the cost of the Kepler irrigation pump systems. • Membrane costs that reflect a conservative approach such as the massive allowance for unsubstantiated algae filtration, as well as a 15% risk contingency. • In summary the major cost items described are adding an impost in the order of $3M to the SDI

CPI pumps are submersible in trickling filter recirculation pumpwell. Adjustment made to pump/pipe comparison in estimate Duty/standby considered necessary for SDI filters. Crucial that system is reliable under sustained peak flows. Stainless steel assumed as ww is septic. The estimates include manifolding, valves, plinths etc See above, per m2 rate for PS building reduced for MF plant. Risk allowance reduced to 5% Risk allowance for algae for peak load MF option reduced to $200k, as per base load, as any remedy would be similar. Not sufficient certainty at this time to remove this risk allowance, especially given the reduction of the general risk allowance to 5%.

Refer earlier comments, the cost estimates have been updated to correct the comparative basis of unit rates for the various elements.

I have not seen an updated OPEX but note that the figures in the November 2017 report need some refining and attention to excessive costs allocated to SDI

Opex discussed at conference call on 27 June. Very little difference between options, not considered material to CPI/SDI comparison

Generally agree, but typically the business case would be on some form of NPV?

I am pleased to see that an allowance for bridges over the bog has been included for CPI although as I noted the $500/ m was a non-professional estimate.

Understand comment on your $500/m estimate. We ran with that as it provided a similar cost to splitting the ‘peat bog’ irrigator into two separates ones that avoided the bog altogether.

Agree – avoid the peat bog would be the preferred option.

I think you have underestimated the cost of gravel tracks as I estimate there could be 15km of tracks and allowing even 0.1m3 per m would result in about $30K for gravel and a similar

Opex increased from $2k to $5k pa, as advice is it is more cost efficient to maintain any problem areas rather than provide full tracks everywhere.

Refer earlier comments relating to soil properties.


Ecogent Feedback of 7 June Stantec Response Peer Reviewer comment amount to install, along with ongoing annual maintenance. SDI Benefits The section on SDI benefits needs expansion. In the text the general theme is that SDI and the membrane are far more operator demanding than the CPI option, but we have provided information to suggest that this is not the case. The report continues to suggest that there are no direct comparisons for SDI despite the project list we have given you. If the argument is that none of the SDI projects on the list are considered sufficiently direct comparisons then it would be appropriate to emphasise that there are no direct comparisons for CPI either as we are not aware of any with this quality wastewater on a site such as this with the associated challenges we have highlighted. The report should clearly state that Pathogens are better dealt with by SDI vs CPI. This is because of the combination of the membrane providing additional pathogen removal the greatly reduced potential for direct contact (no spray drift etc.) and the lower pulse doses that are possible with SDI. I think the issue of how to deal with unexpected wet weather remains moot and is an area that should be looked at far more closely including in field monitoring as I see it as a real unquantified risk for Council. The previous fortnight for instance had 8 days of rain totalling 80mm, which followed a prolonged wet period which would have kept the soil close to saturation so ponding and irrigation restrictions would have

Comments noted, but no change proposed to the Risk Assessment section of the SDI Basis of Design, as it is felt to be fair and that these matters are covered. The updated SDI Basis of Design and estimate makes allowance for the difference in wet weather resilience, to the extent that it is felt that a fair comparison will be made when using this information in the Business Case assessment. More rigourous modelling will be done re buffer storage useage in adverse weather events, accepting that this is not an exact science

Agree that frost protection for variable rate CPI needs to be considered. Hydraulic loading of the soils, particularly when saturated, will be an issue for both SDI and CPI. Refer earlier comments relating to spray drift.


Ecogent Feedback of 7 June Stantec Response Peer Reviewer comment been inevitable. To make matters worse the next 3 nights had temperatures of -5, -4 and -3 degrees so icing of the systems could have been problematic. In this context, to my knowledge, there are no other schemes that would need to operate with such extensive control over nozzles to avoid wet areas and the control valves for these will require protection against freezing which I cannot see allowance or precedence for. The difficulty for the operator to access both sites in adverse conditions such as prolonged rain and icy conditions reinforce the value of the SDI. Allowing an additional amount for increasing storage for the CPI option goes part way towards addressing the issues however there is a need for more rigorous modelling which should include understanding the surface flooding and consequential irrigation limitations. SDI Complexity As stated above I don’t agree with the comment that the SDI -membrane concept is overly complex on several counts. Firstly SDI is automated and in reality requires minimal operator attention. For example, Peter Gearing recently visited the NZAS site at Tiwai Point for the first time in approximately 15 years to provide an overview assessment of the system following the recent site fire. He reported a happy customer and a scheme that after 20 years operates automatically with minimal operator input. This is important in the context of the similar cold conditions and is in stark contrast with the implication in the report that the SDI concept is more complex than CPI.

The point that was being made in the Basis of Design report is that compared to the existing ww scheme a CPI or SDI scheme will be significantly more complex and operator training will be required. It is accepted that MF plant is readily managed. A CPI scheme without MF is seen as simpler. Day to day, at the irrigation site, it is fair to say CPI and SDI are of similar complexity to operate, and words to this effect will be included. It is important to note that SDI has the particular risk to be managed of avoiding dripline fouling. This is a tolerable risk, but operator training and

The upgraded treatment and disposal system will require active management regardless of CPI or SDI installation. Automated control is expected but operator understanding and intuition of both systems throughout a season cannot be underestimated. However, I don’t believe there is a reasonable difference in complexity between the systems to affect the business case.


Ecogent Feedback of 7 June Stantec Response Peer Reviewer comment The smelter is also relevant in that the field is installed in pea gravel. The smooth gravel outcrops at Kepler will not require sand trenches. The ripping provided by the proprietary blades of the insertion machine is generally adequate although in some conditions contractors adapt ploughs to suit the conditions. (We also note these machines are available in NZ) Secondly in discussions with the membrane suppliers it is evident that these also are automated to the extent that an hour per day or a day per week is all that is required and there are now good examples that should give you comfort. I think you need to be more upfront about the relative CPI system complexity in any comparison, if only to highlight the SDI advantages for specific climatic and other events. As stated in the consent evidence for the CPI “management will not be for the faint hearted.”

procedures will need to be rigourous. This is not a risk that SDC will compromise on.

Future proofing Rather than investigating the opportunity that SDI offers for future proofing including smaller diameter pipe and on line direct pumping the report simply mirrors the CPI scheme concept in this regard. While this is a quick and easy approach it obfuscates the potential reduced costs for the SDI system. Further to the potential cost savings it is my opinion that when it comes to future reconsenting, the CPI challenges will be problematic and options for expansion will be limited whereas SDI provides many opportunities to expand at Kepler or at other places along the mainline or adjacent to the ponds which are denied to the CPI concept. With this in mind the

The size of the main Transfer Pipeline has been again considered with SDC. The conclusion is that a 250mm pipe is the smallest internal diameter acceptable, for the reasons stated in the Basis of Design report. It is felt that SDI’s potential to mitigate peak flows has been allowed for by adding scope to the CPI estimate for additional resilience measures (see s2.1 of BoD report).

Refer earlier comments. The sizing of the mainline cannot be compromised by the SDI or CPI disposal system. Linear infrastructure, such as the pipeline length to Kepler, are much easier and cost effective to futureproof initially, rather than be short of capacity in the future. As per earlier comments, a staged approach for disposal is anticipated and it could be that a combined system of CPI and SDI is the result long term. SDI is not disadvantaged by the correct sized rising main.


Ecogent Feedback of 7 June Stantec Response Peer Reviewer comment opportunity exists to economise on the proposed SDI option in the knowledge that in future the opportunity will be for expansion at Kepler or at other less problematic sites. SDI is disadvantaged by the decisions to provide oversized infrastructure now for possible future eventualities. It would be better to design SDI for the present permitted period for purposes of comparing the systems. It is practical to then consider the significance of the NPV of future upgrades rather than include those costs now. Future proofing All the major SDI schemes in NZ have the filtration- pump- pipeline-additional filtration – SDI layout and operate successfully. The uncertainty about how to manage perceived problems with mainline biofilm, sediment and air transport have created unrealistic impositions on the costs of SDI and are these are aggravated by the increased pipe size for CPI peak flows and associated scour requirements. In this regard the higher quality water from the membrane reduces the impacts of sedimentation and gas conveyance or release. I believe that if you costed a similar concept to the other NZ systems the overall SDI price would be far closer to the CPI price and give decision makers a better reason to consider the other issues.

Generally covered above. The point is repeated that a conservative approach will be taken to protect against fouling of the subsurface emitters. This is a risk with significant consequences.

Direct comparison with other SDI schemes is not appropriate with the different treatment processes prior to disposal and the much shorter distances between the treatment plant and disposal sites. As far as I understand from Peter’s comments there is no precedent for the proposed Te Anau treatment system combined with land disposal, therefore conservatism across both SDI and CPI designs at this stage is appropriate.

Future proofing For example, a smaller pipe plus allowance for duplication in future has an NPV of about $1.5 M more than the large pipe but reduces associated costs and has greater future opportunity particularly as the pipeline duplication will probably be over ridden by better options.

A minimum internal pipe diameter of 250mm has been reconfirmed, as stated above. Consenting new disposal sites is not to be underestimated. AEE requirements are rigourous and standards are increasing over time.

Refer earlier comments.


Ecogent Feedback of 7 June Stantec Response Peer Reviewer comment Noted that the opportunity for SDI at a new site in the future is available for both SDI and CPI, although accepted local SDI track record is useful.

Overall Risk Assessment CPI risks that are overcome by SDI need to be better addressed • better future options for the quality and value of feed supply. • By only utilising 80% of the area SDI provides more opportunity for expansion. It could deal with a 25% population increase within the area occupied by the proposed CPI or 100% increase within a 110ha area whereas CPI could probably only manage a 50% increase in the same 110ha. • Birdstrike and risk to Council • Aerosols which potentially become more of a risk as public perception grows. • Management complexity in adverse weather

These first two benefits for SDI will be added to s9.2 ‘Opportunities for SDI’. SDC has commissioned expert advice on birdstrike risk and has instructed any consequences to be included in Business Case assessment. CPI aerosols are properly managed and proposed use of low pressure developments further reduces risk. Adverse events for CPI discussed in s2.1 of BoDesign. With this, the higher hydraulic loading of SDI, and with events being infrequent, it is felt the management load is comparable.

Refer earlier comments, particularly around hydraulic loading and risk of surface ponding or excessive drainage. I am unsure about the risk of bird strike due to centre pivots. If it is because of the change in crop conditions alongside the air strip increasing birdlife, then it is the same for SDI and CPI. There is a national wetland reserve at the eastern end of the air strip which must harbour a wide range of birdlife that would far exceed what irrigation could add. Centre pivots are not typically nesting places for bird life. Aerosol risk can be reduced with longer droppers and alternative sprinkler options. Improving the effluent quality through membrane filters also reduces the perceived disadvantages of CPI.

In summary, my belief is that the CAPEX is excessive for SDI and not a valid comparison for the reasons outlined. There are also improvements required in the earlier OPEX figures to allow a more realistic comparison. The second point is that there is not sufficient emphasis on the merits and advantages of SDI in the context of the site challenges and uniqueness. Finally it will be difficult for non-technical people and decision makers to get a reasonable

Generally covered in the detailed responses above, but the net effect of taking the Ecogent feedback into account has significantly reduced the gap between SDI and CPI.

Comparative cost basis has been updated. The design basis report is a technical report and should be circulated as such. It is our role to ensure that the technical detail is appropriate and accurate and that it is then used to advise non-technical people and decision makers through the business case process. I reiterate the point that if every advantage of SDI over CPI is captured in the cost estimates, then these same advantages cannot be used against CPI in other elements of the business case consideration.


Ecogent Feedback of 7 June Stantec Response Peer Reviewer comment understanding from this report of the opportunity SDI offers.

Option 3A – SDI with Baseload Flow Membranes

Stantec sought advice from John Cocks, their reviewer, regarding this proposed option. After consideration, John’s advice was very clear that this option

should be avoided. This opinion was based on three fundamentals:

Underlying Principle: The integrity and performance of the SDI field is a critical process element, with no real bypass option. For such an element, prudent design is to add redundancy, whereas allowing occasional algae bypass reduces redundancy.

Experience: John’s experience with rapid infiltration basins (RIBs) is that algae blinding is a very real factor. In RIBs, sacrificial sand layers (or similar) can be added, such that they can be dug out and replaced as needed. This option would not be possible for an SDI field.

Technical: The USEPA manual identifies algae blinding as a risk.

Peer Review Comment – what is the risk of algae blinding the soil surface through CPI? What are the options to physically manage this, cultivation, crop selection, aeration, ripping?


Ecogent Feedback of 7 June Stantec Response Peer Reviewer comment Hi Roger, Thanks for the [cost estimate] spreadsheet. I have gone through and highlighted in red the key areas we consider need change and attach the modified version.

Main points. I have removed the Option 3 that relied on filtered bypass of peak flows as it raises complexities that we don’t need at this stage of the process. I have concentrated therefore on a critique of the Option 3B being 4.5MLD Membrane filtration with 45Ha SDI now and 10Ha in stage 2. It is listed as Eco Option 3B. Revised figures are in red on the spreadsheet. The main savings which are highlighted in red in the savings col and are mainly above 50K are [see below]:

Noted, and this addresses John Cocks’ concern (see above)

Agree

5 Membrane 5.02B Budget allowance. 300k. As noted

by Ben, better to tag as a Stantec uncertainty. As per my previous note suggest you talk to Masons.

5.04B Building. Excessive size and cost.

Reducing the extra 40m2 saves 80K, potential for more if "skyline garage" approach adopted.

5.14B Balance tank. Quote obtained for

supply of 4x25m3 conc tanks with

Noted. Approach (noted above) has been to reduce this allowance to $200k and reduce the total scope risk allowance for MF to 5% SDC instruction to add in the 40m2, as this provides resilience to changes. Reduced to 5%.

Refer earlier comments about comparative unit rates for similar elements between the options.


Ecogent Feedback of 7 June Stantec Response Peer Reviewer comment flanged outlets at 27k, allowed 50k, saving 80k.

5.16B Risk. Very hard to see why 15% given quote from Masons with recent experience with 2 similar. Reduced to 5% as per all other components. Saving 270k

6 Rising Main Pump Station. 6.05 Pump station building and civil

works not required as pumps are surface mounted and fed from the permeate storage tanks. Allowed 20m2 addition to membrane building. Saving 135k

6.06. Excessive cost for pumps. Allowed for eg Grundfos multistage 3 in parallel plus standby with smart control. Saving 130k

6.07 MEICA. Pumps have integral controls, potential saving 50k

Covered above. 50m2 allowed for at lower building cost for MF. Cost is same for all options, so no change.


8 Kepler electrical supply and monitoring. Should be less for all components as only one pump set for irrigation compared to ditto for CP irrigation, pump set for T/F and 2 fan sets for T/F and odour bed. Minimal saving of 10K allowed for.

Accepted


12 SDI 12.1. Storage. As per membrane storage

conc tanks, savings 80k 12.2 Pump shed not needed. Could be

submersible as per CPI. Save 100k

See comment below re timbertank Pump shed kept to shelter mech equip and operations staff.



Ecogent Feedback of 7 June Stantec Response Peer Reviewer comment 12.2.Pump set. Same cost as CPI.

Allowed extra 30k for more efficient multistage set. Save 125k

12.3 Filters. Only need 1 plus spares. As

per quote allow 50k save 100k 12.5.2 Zone inlet valves, Cost is

excessive. Use standard irrigation valves add air valves One upstand/2 adjacent fields. SCADA inc in S.12.5.4 Save $48k

12.5.2 Inlet manifold flush points. Not standard practice. Save 90K

12.5.2 Inlet manifold flush line. Not required and not standard practice. Save 70k

12.5.3. SDI 20mm pipe supply. Price

excessive. Suggest also using thicker wall 1.25mm. Landed price inc margin 1.25/m save 157k

12.53 SDI install. 50c/m more realistic.

Save 225k 12.5.3 Risk for stony ground. Unlikely

and also excessive. Use 10%, Save 67k

Cost halved to $100k and includes manifolding valves etc. CPI est raised $25k for same reason. As commented above, duty/standby filters preferred for reliability in peak flow. No change proposed Flush points to be kept. Required for consistent approach to consenting and odour treatment. Agree, updated pricing from Waterforce confirms. Bottom up estimate (as discussed) gave 55c, this is used. No change, risk allowance considered fair. Ultimately, if SDI proceeds, a grid of test holes should be dug to provide a factual report to fully define the risk, as limited holes dug on the North Block to date. No change. Same rate as CPI No change. Considered comparable to high level of CPI odour control. No change. Flush main rate considered acceptable.

Note comment related to unlikely risk around stony ground, yet anticipated install of SDI is within or near gravel layer to reduce risk of surface ponding from SDI. Need to be consistent, if SDI is to be more resilient through the winter it may need to be in the more permeable gravel layer, therefore drainage risk is higher as is the risk of installation in stony ground.


Ecogent Feedback of 7 June Stantec Response Peer Reviewer comment 12.5.4. SDI Field elect. Excessive price.

See quote from Parklands and also similar item allocated to CPI was 15k as CPI control inc in package price. Use Parklands plus allowance of 20k for contingencies. Don’t recommend 230v. Save at least 35k.

12.6 Air vac valves. Install in inlet valve chamber, Valve cost $250. Allow smaller odour filter and only one per 12 chambers serving 2 fields. Save minimum of 96k.

12.6 Flush submain. PN6 adequate, rate excessive for 80mm. Save 52k

12.7 Stage 2. Unit price for stage 1 was

37k/ha which is closer to industry norm. Reduces Stage 2 cost to 19k/ha . Save 147k.

12.7 Further smoothing. Unnecessary additional cost. Previous allowance for earthworks is approx. 2k/ha which is more than adequate. Save 30k.

The above items which are highlighted in red in the savings col of the spreadsheet, along with minor savings items listed ( with explanations) result in an SDI section 12 savings of 1.8M. and an Estimated construction savings of 3.5M.

Pro-rata price will flow through. No change, as considered reasonable.

14, External to contract 14.1 Additional Consenting. I consider 300k is excessive. If SDI was compared to CPI on

Disagree. Consenting has been very difficult and will be notified.

Agree that consent changes will be challenging and costly.


Ecogent Feedback of 7 June Stantec Response Peer Reviewer comment the key issues then all parties should see the environmental advantages of SDI. CAPEX and its effect on costs to the ratepayer could however create potential opposition. We have reduced the figure from 300 to 200k, a saving of 100k. Also note that some suggested changes in CPI could require additional consenting costs. 14.2 Design contingency. The concept is proven. What is needed is to talk to companies that have designed SDI systems to confirm industry standards of equipment and layout for purposes of costing. Most design criteria is understood and utilised in the draft concept to date. Saving minimum 100k. Total estimated Capex savings 4.25M

See above $300k difference is reasonable. No change. Has been difficult to date to understand and resolve risk areas, and it is considered that there are still a range of matters to fully resolve.

Refer previous cost estimate comments. Unit rate adjustments have been captured in the cost estimates where appropriate for this stage of design and I do not believe further reduction in SDI elements is appropriate. If environmental advantages have been captured through the cost estimates then the options should be considered equivalent, we cannot double count. For example if surface ponding is a higher risk for CPI and we add the costs for extra storage for this option, then the perceived environmental advantage for SDI is negated.

Option 3C We also looked at the option of using a smaller pipeline. The reason for this is that the peak flow is dictated by the need to pump down the ponds before and after peak events to allow for the downtime from CPI during heavy rain and possible ponding, neither of which are an issue for SDI. A smaller pipe diameter results in a more simple system.

A smaller pipeline is not pursued, as discussed above and in Basis of Design report. Storage at the ponds is also discussed above.

Again, there is possibly an optimisation process through detailed design and the cost offset between storage and transfer to the disposal site.


Ecogent Feedback of 7 June Stantec Response Peer Reviewer comment The main saving is in the cost of the pipe supply and install. We obtained a quote from a supplier for both the current proposed nominal 300mm pipe and a size smaller nominal 250mm pipe to allow us to compare prices and ensure margins were consistent. The savings for the pipeline portion are 840k with a total bottom line Capex savings of 1.25M compared to ECO option 3B or 5.5M compared to Option 3B. There have been many reasons given for why a smaller pipeline is unacceptable however these should be looked at in the context of the better understanding which would be gained by modelling wastewater inflows and rainfall frequency with the benefit of the water meter and taking into account the probable restrictions at Kepler during major events. This remains an outstanding issue in my opinion. We believe that better modelling is essential, using for example the flows of May 2016 and extrapolating the base flow to the 25 year horizon. We also note the low cost potential to increase storage at the ponds which would be beneficial to the smaller diameter pipe option. Comment on OPEX. We haven’t had the revised OPEX figures but note the potential savings attributable to SDI.

Opex costs for CPI and SDI very similar and considered to be a reasonable comparison



Ecogent Feedback of 7 June Stantec Response Peer Reviewer comment Comment on Ben’s report. There are some useful issues highlighted and we will send separate comment.

Noted.

P Riddell email 29 June 2018. 10.59am 100m3 Balance Tank

Hi Roger, For your ref I have attached a quote for a lined timber tank with sealed roof, the same volume as we specified for Omaha to receive filtered water pre irrigation. Served its purpose for past 18 years and a much lower cost than fibre glass lined. (Quote of $56,800+GST enclosed, cf $130k allowance in estimate for glass coated steel tank).

A lined timbertank could be considered but noted that the required standard for a tank has not been established yet. As the equivalent CPI tank is PVC lined, and $100k has been added to the CPI estimate for extra balance storage it is felt the CPI/SDI comparison is fair and therefore the lower cost of a timbertank is not assumed in the estimate.

Agree


Hydrus Modelling – Comment by Stantec Preliminary results have been received from the Hydrus modelling (as of 6 July). This properly takes into account the mitigating effect of the dryland areas comprising the remainder of the total 121 Ha site over which N leaching is allowed to averaged. This averaging is on the basis of using the current CPI consent condition of 32 kgN/Ha/year based on Overseer modelling. These results indicate that with regard to controlling N leaching, the assumption of an initial area of 44Ha for SDI is acceptable. The direct comparison data with CPI is still awaited. The principal objective is to determine, under Hydrus, a comparable SDI area for N leaching, versus the currently consented 69Ha CPI area. It seems likely that compared to Overseer Hydrus modelling will indicate lower N leaching for both CPI and SDI. This was expected as Hydrus is a more accurate form of modelling, using daily data. For the logic stated in 7.18.4 of the SDI Basis of Design, smaller areas and higher hydraulic loadings may be difficult to consent. Increased hydraulic loading for either method of irrigation also increases the risk of saturation in extreme events and daylighting/ponding. A consequence may be increased cost in buffer storage. This highlights that hydraulic loading and N removal must be treated as separate considerations. Given the above, the minimum SDI area of 44.3Ha as stated in the Design Report remains. Stantec response to Email, P Riddell 6 July 2018, 9.58am. Titled ‘Scoring Criteria’. The following email was received on 6 July. The detailed responses generally cover the points made, so will not be repeated, but in general:

A fair amount of Peter Riddell’s feedback re cost has been taken into account in the final update, and the estimates updated. In particular the cost of the procuring and installing the dripline.

The opex budget has been increased for wheel track maintenance, as advice is that this is best managed on an ongoing basis when and where it occurs

The Business Case explores cost sensitivity of the options. In other words the effect arising from the real cost being higher or lower than estimate.

Modelling of irrigation and buffer storage in extreme weather events is ongoing, and it is accepted that this is important. A cost provision has been made to balance risk differences between CPI and SDI.

With regard to the comments on scoring criteria, it is understood that these are technically outside of Peter Riddell’s brief, but are included below in any case. It would be inappropriate for Stantec to specifically comment, as the assessment of scoring criteria is done individually by the Business Case assessment team members.

Email, P Riddell 6 July 2018, 9.58am. ‘Scoring Criteria’. Hi Roger, Further to your comment last week re the scoring criteria it is clear that it would be useful to acquaint the scoring team with the issues recently discussed so I have made relevant comments below. Capital cost


I have assisted with providing a conceptual SDI layout and operation methodology and costing, but to a large extent you have not agreed with many of the figures, despite the fact that our SDI figures are experienced based. Ploughing in the SDI is a classic example where there is a 100% disagreement on a unit rate which has a greater than 300k impact on the CAPEX bottom line. There have been savings with the more efficient layout we suggested however these have been overridden by conservatism and a lack of practical project based understanding). In summary my SDI as well as total project estimates are about 20% lower. This is using the same mainline pipe size as for CPI and the larger 4500m3/d membrane. I have also identified areas where I consider CPI has been under costed including gravel tracks particularly as there is no information on the extent of weak, when saturated, soils, and the cost of the irrigation pump system compared to SDI. I suggested that one approach was to evaluate the SDI using a high and low cost estimate and determine if a review of the Scoring Criteria showed the difference was significant then a closer look at SDI cost was warranted. If I look at the scoring methodology you were using the change in CPI and SDI costs could reduce the CAPEX CPI score from 0.98 to 0.7, and increase the SDI from 0 to 0.45 We haven’t addressed discrepancies in OPEX. I haven’t time to update this, however there are some notable areas of excess including the overestimate of SDI chemicals and power and the underestimate of the CPI irrigation power. Again this has a big effect on scoring. There have been some areas of agreement which provides more certainty to the evaluation process in the Key Values.

Hydrus confirmed that 1m row spacing was acceptable and that the 20% area reduction based on the expected membrane nitrogen removal is reasonable.

The hydrus model using pulse irrigation from SDI cannot identify any greater leaching of N than is likely from CPI.

Hydrus is unable to take into account the reduced N leaching in winter likely from SDI because of the predominant ammonia form which can only be a long term advantage to N leaching from SDI.

Overseer is not able to take into account reduced leaching from ammonia as it is not set up to do so therefore SDI leaching is likely to be less than Overseer predictions.

In summary there is no evidence that SDI will leach more than CPI, and it is in fact likely that monitoring of SDI will show that leaching is less.

It is probable that SDI will use water more beneficially during the summer droughts which will result in a better yield per irrigated Ha, and, by extension more N uptake and less loss to groundwater.

The accompanying email from the CEO with my brief included the statement; Roger Oakley (Stantec), Ben and Peter to convene via phone conference with a view to agree relevant design inputs / parameters associated with the SDI Concept Design. In particular, elements that have to date been the source of contention (i.e. storm water inflows, pond storage, Kepler capacity, nitrogen losses etc..).


I have tried several times to initiate discussions about storm inflows, pond storage and Kepler capacity including my spreadsheet of inflow, rain, storage and irrigation and photos and comments regarding Kepler ponding and limitations on irrigating the full area during extreme events. I understand you have set up a spreadsheet mirroring the one I have provided, particularly for the May 2016 storm, however there has been no attempt to model the irrigation constraints at Kepler and what impact that might have on the required amount of storage or on the risk of overspill. This remains as a big unknown and potential risk for CPI and should be clearly identified and addressed in the Evaluation. Dealing specifically with the scoring criteria the following are items that I feel have not had the SDI potential understood or included to date or need adjustment.

Environmental E1. Ability to obtain long term consents. This could be considered in terms of the 25 year consent as granted and the potential to gain future consents after 25 years given the argument for investing in future infrastructure capability now. It is highly probable that CPI will have more challenges for long term consents than SDI. In terms of the 25 year consent CPI rates highly because it has the consents, however the quoted uncertainties in predictions regarding the ease of consenting SDI are substantially being resolved as the issues are debated and modelled through this “commenting” process. Environmental E2. Adaptability to meet increased environmental standards. CPI has more potential limitations at the irrigation site, for example aerosols/spray drift is likely to become more contentious as public health awareness increases. Proximity to airport and bird strike, possible runoff management issues. There is uncertainty about the effects of spraying near an airport in cold conditions and risk of creating induced ice on the runway. CPI will have less ability to expand particularly to deal with storm flows. SDI has minimal environmental and health & safety risk. The belief that the reduction in area because of the lower nitrogen concentration is possibly a disadvantage is not substantiated. It is more likely to be an advantage because it allows a greater area for expansion. It also allows better summer crop yield with better irrigation rates albeit still smaller than ideal for crop yield. CPI has many conflicting managerial / operational requirements with potential environmental risk, i.e. needs to be empty for frost / full for heavy winds/ off during storms / extended operation post storm for pond draw whereas SDI is “hands off”. SDI with its numerous discrete zones – allows for far greater flexibility of control and application (compared to the CPI all or nothing approach). In summary very difficult to see how CPI could score more than SDI for E2.

Environmental E3. Adaptability to meet increased flows and loads. SDI has more flexibility with transfer pipe size with its all weather irrigation ability. It currently needs less than the consented 4500m3/d to manage pond storage because of that. SDI uses only 80% of the land area for the same flow and therefore has more expansion potential at Kepler than CPI on the available land. SDI can be placed on the best land and avoid wet and pond prone areas CPI has a big unknown about its peak irrigation limitations as the site and water quality are not similar to other such projects In summary it is difficult to see how CPI could score more than SDI for E3


Iwi Acceptability IA1 Extent to which it meets aspirations of Iwi. Iwi accepted spray as an improvement on direct discharge. As is the case on all large SDI in NZ, Iwi prefer SDI to sprinkler as a method of land application, if given the option, and that has driven change. eg Pauanui. There is a risk to the project future that when it comes to reconsenting Iwi will realise that there are better ways No justification for current score showing CPI is greater than SDI. Should be reversed for IA 1. Social Acceptability SA 1. Score likely to be widened in favour of SDI both now and in future when consent is renewed. We have discussed most of these issues but as they are spread out in the correspondence we have provided I hope this collection will assist with the evaluation


Design Report

Ref Comment by Peter Riddell (Ecogent Ltd) Stantec Response Peer Reviewer Response

P Riddell email of 12 July 2018 1.30pm General Comment


Cost estimate

Your draft Design Report has just arrived. I will review later but will send these comments now as some relate to current conditions at Kepler that are important in the context of what it can actually irrigate in wet conditions. Thanks for the response. As requested I have restricted feedback to key items and a couple of topics raised in discussion with Ben last week. We have achieved a better understanding of SDI systems and general confirmation from the Hydrus work that the suggested spacings and irrigation rates are viable. We have not achieved much agreement on the relative costs. The reason is for three main reasons: A lack of experience and hence confidence in municipal large scale SDI

from some of your advisors, a tendency to price individual items on a like for like basis with CPI

rather than standing back and looking at a conceptual SDI system from pond to farm and

unsubstantiated conservancy on issues such as algae influences on the membrane.

This is aggravated by the desire to maintain like for like with consent requirements on items such as odour control whereas evidence at other schemes without the benefit of the membrane filtration, and with houses adjacent to the systems shows odour is not an issue. This type of contingency should be removed and kept as a bottom line item subject to discussion in any consenting process for SDI. The CAPEX difference for Item 3 [Stantec note: refers to Option 3B for SDI vs Option 1 for CPI] compared to the consented option is about $4.5M. Ecogent considers that difference could be reduced to about $2M as well as a small but undefined amount for OPEX.

Like-for-like comparisons on matters such as odour is deliberate, in order that a consistent approach is taken, with the same level of conservatism between options. Overall, while the estimate for any individual item can easily be debated, our opinion is that the risk between estimates is comparable and fair. It is noted that the relative capex costs between CPI and SDI have reduced from $7.3M to $4.5M in the period December 2017 to July 2018. This is largely due to refining a site-specific SDI layout, and better understanding the differences between SDI and CPI.

I believe the cost estimates have been updated to reflect the key discrepancies between the review parties. Unfortunately the reality is that SDI is not commonly installed across 40-50 ha of land in New Zealand, whereas CPI is, therefore the infrastructure cost basis will be slightly different. The various treatment aspects of the two systems has also been similarly updated to reflect the differences between them. In some instances the advantage is reflected in a cost “penalty” for an item, such as buffer storage for CPI. These items have been included to ensure the comparison between equivalent systems.


Ponding and soil strength

The extent of ponding and poor soil strength and consequent restrictions on irrigation at Kepler as well as the frequency of events that will restrict CPI has advanced no further. This is outside the brief except in that it affects relativity of costing and raises issues that should be investigated further. This past week for instance 80mm of rain fell yet most of the block is apparently not accessible by vehicle according to the farm manager, even though the proceeding 3 weeks had negligible rain. This is in contrast to the two large operating CP systems in NZ. Part of the recommended investigation for SDI is boreholes to determine the extent of stony ground and this needs to be extended to understand areas that are regularly ponded and which are too soft to carry the irrigator wheels without major works and drainage improvements. Photos have been provided and “noted” but attention has not been placed on the significance of the issue. In a phone discussion with me last week, Ben noted the increased water flow due to the smaller SDI area and expressed concern that this may be a constraint. My summary of that issue is that the worst case is a winter storm. The maximum irrigation rate based on the 2000m3/d consented flow would be 2.9mm/d for CPI and 3.6mm/d for SDI. The saturated permeability is 9mm/hr in the upper layers or about 200mm/d. There is clearly no drainage constraint within the soil profiles with that good drainage characteristic. The biggest issue will be at the surface where suspended solids, particularly algae will accumulate and restrict surface infiltration. This will be aggravated in winter conditions and on sloping land increasing the frequency and magnitude of the exiting runoff and further increasing the extent of the ponded areas. SDI by contrast has a cleaner water with no algae and being about 200mm below ground is not subject to the surface restrictions and will not create wastewater contaminated runoff. On the outer extent of the CPI spans where many of the soft areas are the instantaneous application rate of 20mm/hr will add to the runoff potential from CPI. Photos of flooding from 2002, 2014 and 2016 show the extent of the ponding. Adding the extent of the adjacent sloping land as evident from the contour plan on the Sharefile suggests that the area that would need to be avoided for irrigation is likely be in the order of 5 to potentially 20% of the

The differences between SDI and CPI have been balanced by a lesser irrigation area and buffer storage for SDI. SDC staff drove over the paddocks in a car the day after the May 2016 storm, suggesting that issues with soft spots are more isolated. The capex and opex budgets were increased to allow for a more conservative approach to irrigator wheel tracks, but will be double-checked. Advice from Aqualinc is that with less area and buffer storage, SDI irrigation limits in extreme events are similar to CPI. Agree that detailed design and operational experience will refine the best irrigation areas.

I drove over the site on 30th July 2018 after an unseasonably wet month and similarly was able to drive around the site with no issue. There are certainly areas through the gateways and around the bog that will need remediation or be avoided by irrigation infrastructure. I disagree with Peter’s comments that the risks of surface ponding and wheel track maintenance have been ignored. There has been adjusted costs applied in buffer storage and gravels for track repairs against the CPI option. Whilst the photos provide a snapshot of the surface during or immediately after a storm event, the soil investigations provide evidence that the permeability for both SDI and CPI will be acceptable. Peter continues to state that the soil permeability favours SDI, but a surface issue (not captured in the soil investigations that I can see) will limit the performance of CPI on the same soils. The reduction of algae through the membrane filter is an option for CPI and perhaps will reduce the added risk of surface sealing as discussed by Peter. The overall characteristics of the soils which make SDI attractive, are also applicable to CPI.


Design Report


CPI area depending on the storm severity. This should be looked at in far more detail before the layout of CPI or SDI is determined.

Saturated permeability of 9mm/hr for SDI is the same for CPI. Noted that increased surface ponding at the extent of CPI spans could be expected if soils were saturated. But if they can continue to drain at the permeability rate confirmed on site, then the ponding would be short term. During the site visit there was no evidence that ponding that does collect in the ephemeral water courses (depressions) migrates laterally across the surface but rather soaks down into the soils over time. The bog appears to be an area of groundwater coming to the surface, with no clear drainage path that collects water from across the site to this particular location.


Design Report


Ponding and runoff

Ben also commented on the possibly reduced ability of the soil to capture N from the higher SDI irrigation rate. My comment is that the 3.6mm/d will be applied in about 8 doses of 10min duration and 0.45mm depth each with 2 to 3 hours between the short pulses for the wastewater to assimilate nitrogen. It is generally agreed that nitrates in the CPI water will leach to drainage however ammonium nitrogen as in the SDI water will be more likely to be taken up on available soil sites and released for summer crop uptake thereby reducing losses. I would also note that under these small pulse irrigation circumstances there is no opportunity for the applied water to rise to the surface, in a well designed scheme, which is another concern expressed. The comparison with CPI and the outer spans of the pivot irrigators is a single dose at a rate of 20mm/hr in an 8 or 9 min deluge which clearly has more potential to cause runoff.

Noted and discussed earlier, with regard to ammonia v nitrate. Agreed that SDI has the advantage of being a more ‘gentle’ form of irrigation, and has advantages from being subsurface. While either system in normally OK, this is the reason why, in extreme events, less buffer storage is required, SDI can continue irrigating for longer, but there are limits.

My comment simply relates to the time when the soils are fully saturated and whether the ability to capture ammonium N under anaerobic conditions still applies. If not, then it will be lost through drainage. Short pulse irrigation of SDI under normal conditions is advantageous, however I am not convinced of the espoused benefits when the soils are fully saturated. Under some conditions irrigation is simply not going to be possible, CPI or SDI, and this will be managed through the buffer storage (additional for CPI).

I have not dwelt on the minor issues that we still do not agree on, and these are generally obvious in the text where they are simply “noted”. Many will be resolved in final design.

Understood

P Riddell email of 12 July 2018 4.16pm Comment on Irrigation during extreme weather events s2.7



Design Report


S2.7. Further modelling for irrigation during

This additional proposed work as detailed in S2.7, copied below, is a waste of resources if it is just a desk study of the drainage/irrigation rates which on its own doesn't add much to what was in the consent docs We believe that in most elevated flat areas drainage rates will be satisfactory and can take more than proposed. The problem comes from the ponding areas, the soft wet areas, and the slopes that lead to the ponded areas or potential offsite runoff. This is then aggravated by the wastewater quality, particularly suspended solids including algae, which restricts surface infiltration and thereby increases runoff. What is needed is an actual site investigation and analyses of the available survey data, supplemented by more survey where needed

The further modelling is underway, based on Aqualinc’s judgement of sustainable infiltration rates during extreme events. This addresses the risk of redistribution and ponding and takes more into account than saturated infiltration rates and hydraulic conductivity. Detailed design will investigate worthwhile surface drainage works.

There is minimal risk of offsite run-off, the site is generally flat with slight undulations that will collect surface water. There is no evidence of lateral migration of water through these undulations. Membrane filtration prior to CPI irrigation will reduce the risk of suspended solids and algae capping the soil surface. I understand soil analysis has already been completed and there was evidence of additional potholing on site when I was there in July.


Design Report


S2.7. Further modelling for irrigation during extreme weather

I highlighted the current soft site conditions after the past week’s not extreme rain in my email this morning as something that should be looked at while the poor conditions exist Key points that I consider should be assessed in a study include: What is the extent of flooding in various historic rain events and return

frequency What is the catchment draining to each ponded area ( on average the

winter irrigation is the same magnitude as winter rain so there will always be increased runoff and ponding)

What is the extent of soft soils and what needs to be done to support the irrigator wheels

How sensitive are different areas and slopes to reduced soil infiltration caused by TSS including algae. (typically ponded areas will stay ponded longer and slopes will discharge more water to the ponds)

This should allow a better concept to be developed showing how VRI might manage the affected restricted areas and what level of operator attention will be required. It would provide the missing information from your pond storage model which I have been going on about since this started.

Recommendations for a study are noted. Operational experience will particularly show how to maximise irrigation using VRI. Overall, Aqualinc’s advice has always been that the site is suitable for the summer and winter conditions, so no further work is planned on defining details of irrigation until a decision is made on irrigation method. Aqualinc are defining recurrence intervals of extreme events. Irrigator wheel track maintenance will commence once operation commences and the tracks/soft spots are defined. This will occur particularly in the first year.


Comparison with other CPI schemes

How does the site differ from Rolleston and Taupo in terms of soil strength for running irrigators on and the extent of ponding. This is not essential but is a reality check for everyone. These sites have cleaner water, stronger soils when wet, no runoff and more CPI units with much more flexible irrigation control.

Tony Davoren advises Taupo and Te Anau are similar with regard to A horizon soil. Te Anau and Rolleston similar in subsoil.

Noted

P Riddell email of 12 July 2018 4.20pm Comment on Additional Storage


7.2 Additional Storage

Hi Roger, further to the last email, suggest you add to the further modelling words to the effect of —— and field assessment of ponded areas, soft areas when wet and catchments that drain to the affected areas along with analyses of return frequencies.

Report updated as suggested Noted


Design Report


P Riddell email of 12 July 2018 4.48pm Comment on Fair Comparison CPI v SDI


2.1 Fair Comparison SDI v CPI

From a practical point of view I just don't see how reducing the CPI by 20% is practical. Do you propose removing the small irrigator? It has ramifications in terms of management of the 26 and 52 lps flows, reduced control with 2 different size units, downtime/ repairs, reduced ability to avoid wet areas, potential issues re consent and different nozzle sizes/ spray drift, increased app rate on the outer units to above 20mm/hr which exceeds sat infiltration rates if only operating 2 of future 3 to achieve the 4500m3/d instantaneous rate. I also doubt that you will achieve a 20% capex reduction for a 20 % area reduction, particularly if it involves consent issues. I would like to see the concept. As always I stand to be corrected

A very clear instruction from SDC is to ensure an ‘apples for apples’ comparison between systems. SDI is based on 80% installed capacity now, and the remaining 20% in 10 years. Therefore for comparison purposes, this feature is introduced. Agreed that it would infer different nozzles and irrigator travel speed. It is correct that instantaneous application rate of the outer spans would increase unless the number and spread of nozzles was amended.

The CPI layout I have seen has four pivots, with one of the smaller ones looking like about 20% of the area. Changing management approach through slightly different sprinkler package should allow for flushing flows to be managed. Larger nozzles will likely reduce risk of aerosol due to larger droplet size. Buffer ponds remove risk of downtime with repairs, unless at time of peak flows which is an issue I have raised previously about the “safety valve” option through pond overflow or high rate irrigation/infiltration.

P Riddell email of 13 July 2018 9.23am Email to Ian Evans SDC



Design Report


Just following up on an email to Roger copied to you and Ben yesterday re the present condition at Kepler to make sure you got this particular message amongst the other issues. My advice in the notes yesterday was that the soft ground be investigated preferably now while it is present as regardless of the system you install that information needs to be gathered when it is available.

Noted.

As mentioned in earlier comments I was on site on 30th July after four days of rain totalling 25mm, during a particularly wet month as indicated in the Metservice historical rainfall data. Whilst not comprehensive, we drove around most of the site and the only soft spots were through gateways and at the bog. Remainder of the site seemed to be holding up particularly well.


Design Report


There is a belief, as noted in the design report, that the site can be driven over after heavy rain. Probably correct in summer but it does not appear to be the case in winter. The attached rain record shows the recent rain. The farm manager apparently advised Ruth Shaw that she needs to get permission from Council to visit the site and anyway it is not accessible by vehicle because of the ground conditions. I just happened on this info when I was copied into an email saying Ruth would be away for a while later this month and who would be taking over. We know that at least some of the farm could not be driven on even by a wide wheeled 4WD during a wet time in 2016. The additional comment in a further email I sent Roger, cc Ben and you yesterday was following on from the new addition to the report that Tony Davoren would be doing a more detailed drainage study. My recommendation was that the real need was to identify those areas that could not be irrigated in wet times, ie ponds, immediate catchment to ponds , soft areas etc. The drainage study is not needed for the well drained flat areas but to date no one has addressed the extent of the area that will not be able to be irrigated in wet weather or attempted to put any frequency of occurrence to it. It is an essential component of the pond water balance and storage work. There is more detail in my emails. I have rung Roger this morning to follow up but he is on leave hence this email to you.

Direct experience of Ian Evans (SDC) in May 2016 immediately after the extreme event was that the paddocks were accessible. While not comprehensive, it indicates that issues with soft areas are not general. Tony Davoren is determining general guidelines for when irrigation is to be curtailed. This allows buffer storage for extreme events to be modelled. This may be different from the drainage study that is envisaged. Davoren’s work will be conservative in that it will not fully account for specific areas that can still be irrigated in difficult times.

It is accepted that the soils on the Kepler block are generally appropriate for irrigation. The ponded areas during extended rainfall periods as shown on photos are slightly depressed areas of the same soil and it is likely that surface improvements through earthworks, cultivation and crop management improve permeability characteristics over the long term.

P Riddell email of 12 July 2018 4.25pm Email to Ian Evans SDC



Design Report


S7.2.1 Additional Storage

If I was the consultant I would be looking also at the concept of constructing the external pond as suggested in the forthcoming Options report (referred to in the attachment S 7.2.1) but would configure it to act as a nitrogen reduction system, only aiming initially for cost effective partial removal, say 50%., and use the existing ponds for storage of peaks. This would give far more flexibility at Kepler as N levels, hence land requirements, would be halved. Selecting the best land that doesn't flood would make irrigation easier and at higher rates. This could all be staged and changes consented as proven. It would also help manage the pond odour issue which isn't going away and manages algae more effectively. I have previously suggested a system such as the IDEAL from EDI in the US.

Refer to response, below, to email of 22 July 2018


ECOGENT EMAILS OF 22 JULY AND 3 AUGUST 2018

Attached below are two emails from Peter Riddell, Ecogent. While these are outside of their brief, to comment on the SDI design, they are included for completeness, and to provide confidence that all correspondence is included. General comment is:

Email, P Riddell 22 July 2018, 9.48pm. Titled ‘Review of Pond Storage based

on Stantec Notice to Client NTC29’

Hi Roger,

I have reviewed the NTC29 in more detail and note that while it suffices for a summer storm there is a big shortfall in the availability of storage in winter to deal with the event described. This needs to be seriously addressed given the experience from the May and July 2016 storms.

It is not possible for 15,000m3 of storage to adequately deal with the forecast 10 year rainfall event in winter under the consented 2000m3/d irrigation limit. NTC29 determined that the future inflow would be 3000m3/d which exceeds the maximum irrigation flow by 1,000m3/d. Over the 10 day storm this means that 10,000m3 must be stored.

In addition there is the 12,000m3 that falls on the ponds from 250mm of rain which must also be stored so regardless of the irrigation method, i.e SDI or CPI there is a storage requirement of 22,000m3. Clearly the 15,000m3 proposed is insufficient.

If the CPI option is pursued we know that irrigation will not be possible on some days due to heavy rain and will also be restricted on the other days due to ponded areas. I estimate that will total 3 days with no irrigation and the other 7 days with irrigation on only 80% of the area so this would require an additional 3days at 2000m3/d plus 7 days at 400m3/d, a total of 8,800m3 bringing the total storage required to over 30,000m3. At least with SDI the total would only be 22,000m3 as it wouldn’t have the

same irrigation constraints in wet weather.

As well as this shortage of storage you need to consider the fact that your NTC29 calculation was based on 250mm over 10 days. However we know that in May 2016 a flow 10% greater than the NTC29 flow was measured over 10 days from a rainfall of about half of the 250mm estimate used in NTC29. This suggests that actual storage requirements in the winter, when a storm with rainfall of the magnitude predicted in NTC29 occurs, will be much greater than the 30,000m3 example I have detailed.

This is clearly an unacceptable situation. Comments such that in future the infiltration into the pipe network from the increased population will be better managed have no precedence and are a high risk assumption for SDC. This is particularly so when the frequency of extreme events appears to be increasing.

To manage this problem the storage needs to be increased. My recommendation is to consider building a new external pond rather than raising the existing pond walls even further. The concept of constructing an additional pond has recently been raised and this analysis suggest it is the only practical approach. However the difference I recommend is that the new pond be constructed as a treatment pond and the existing large pond be decommissioned and retained as a storage pond, typically only used in significant events.

My suggestion is that this external pond is built adjacent to the large pond, is configured with two cells of approximately 10,000m3 total volume and has aeration equipment installed. This would then become the main treatment train that allows the treatment of the wastewater flow to take place with the treated water flowing directly from the new pond to the membrane and pump station to Kepler.


Nominal design would be to accept a peak flow of 3000m3/d. Creating this new external treatment pond would allow the existing inefficient pond to be converted into an extreme event storage pond. It would be emptied and desludged and converted to a peak flow storage pond with an available storage in the vicinity of 50,000m3 which would deal with the future projected winter flow storage requirements. This is the same concept as operates successfully at Omaha where there is a 40,000m3 detention dam/storage pond located after the two aerated treatment ponds. The two small ponds at Te Anau would be retained for sludge storage.

This concept provides Council with four opportunities.

First and most importantly would be the ability to have a large volume (at least 50,000m3) of available storage that could eliminate the uncertainty and risk of overspill or runoff as described above.

Second is the potential for significant cost reduction because the high peak flows derived from NTC29, which have dictated the SDI component design, would be reduced. Savings include simplicity in controlling the pond levels, smaller membranes, removal of the algae control uncertainty, smaller pipeline, smaller pumps, tanks and irrigation area.

Third would be the ability to reduce total nitrogen in the wastewater. A minimum 50% removal is easily achievable in the new external treatment pond and this would provide flexibility for future expansion by reducing the nitrogen load to Kepler and would also help the case for increasing irrigation rates on the good (i.e.non-ponding and high permeability) areas at Kepler to manage the problem of restricted irrigation areas during storms. We have previously tabled concepts to achieve a higher level of nitrogen reduction in a compact aerated pond system and the advantages become even clearer when the importance of providing adequate storage is considered.

The fourth advantage would be management of the current recurring odours at the ponds which are not addressed by the proposed upgrades. Our experience is that odours are not an issue in aerated ponds such as described above.

I trust you can see the value in these comments and can incorporate the recommendations in the design report.

Stantec Comment:

The point being made is understood. For that reason further work is being undertaken to model the performance of the entire scheme in various weather events. Duration of event is obviously a key parameter. Aqualinc are looking in detail at appropriate ‘rules’ for when either SDI or CPI may be

able to irrigate, either partially or fully. This is based on the measured parameters of the soils. Initial results confirm that the proposed 8,000m3 extra storage requirement of CPI vs SDI is reasonable, if not on the generous side. In that respect the comparison in the Basis of Design is considered fair.

An Options report for the physical form of the extra storage is being prepared by Stantec, and various options have different capacity limits, so these will need to be compared to the results of the Aqualinc findings.

The suggestions for achieving the storage have been passed onto the person undertaking the options report, for consideration alongside the existing thinking.

The suggestions relating to options that provide N removal are out of scope. However they are noted, and Stantec presented a summary of them to SDC management on 31 July 2018 for their awareness.

Peer Reviewer Comment:


Whilst outside the scope of my brief to review the comparison between SDI and CPI, the design capacity of the future treatment and irrigation system must be defined.

Standard practise for a Council is to set the design basis for their assets, such as being able to manage a particular storm event. In respect of a wastewater system, peak flows are defined by the integrity of the wastewater network and the response of the network to the design storm event. Typically, a peaking factor of between 2.5 and 4 times the average daily flows can be expected in New Zealand wastewater networks. One of the main ways for a Council to reduce flows to the treatment plant are through network improvements such as separating stormwater and wastewater flows (Watercare, Central Interceptor), reducing risk of infiltration through pressure sewer designs, relining older pipelines, checking for illegal connections such as residential down pipes etc. I understand SDC have a policy for continuing improvement in the performance of their wastewater assets.

It is my opinion that the better the treated product that leaves the treatment plant, the better performance we will see at the Kepler disposal site. Improvements for SDI in Peter’s email also apply

to the CPI option.

I also understand there is some anomalies in the flow recording data, with some being based on pump run times. There needs to be a consistent approach to the assumption of flows from various rainfall events so reasonable and appropriate design decisions can be made.


Email, P Riddell 3 August 2018, 1.09pm. Titled ‘Te Anau reports. SDI Basis of

Design, with selected appendices and Hydrus’

Hi Roger,

Thanks for sending this through.

I note the list of my comments does not include the last 2 sets between the 6th and 23rd of July. They were important in my opinion as they focussed on the increasing awareness of storage issues and a potential solution as well as the recommendation to investigate the significance of the soft areas given the prolonged wet period. Will these be added or should I reattach to my Synopsis?

Could you or Ian advise as I wish to send my Synopsis today.

The Aqualinc report is interesting.

1. It confirms general N loads are OK which is important and that for a 55Ha SDI system the N leaching at 25kg/ha is less than the consent limit and less than CPI at 28kg/Ha on 70 Ha.

2. It notes the different forms of N and the fact that the ammonium form doesn’t leach but tends to build up for later conversion and use, but is unable to model this and assumes instead everything is in the nitrate form. See quote [italics] below. This results in an overestimate for SDI as the winter build up is converted for spring/summer use as soils warmup. In other words the 25Kg for SDI is an overestimate, and should be addressed in future and acknowledged in this report.

In general terms, when soil temperature drops below about 10 degrees, the

nitrification rate will fall rapidly. At 0 degrees some nitrification still occurs, but it is

very slow. N in ammonium form does not generally leach from the soil and tends to

build up in the soil over winter when soils are cold and wet. As soil temperatures

warm up in spring, ammonium is converted to nitrate where it is either leached or

assimilated by plants. We have assumed that ammonium will be converted to nitrate

at some point, so while the timing of N leaching potential or plant uptake may change,

the total N loading over time in the system is retained.

3. The statements re the high irrigation rates at the small area options (e.g. 25Ha) are misleading. They are high in terms of the consent but not in terms of the soil drainage capacity (9mm/hr). It is accepted by all that if SDI was used on the suggested 55ha you would need to vary the consent maximum allowable winter irrigation rate from 2.9 to 3.6mm/d. This should not be an issue as initial investigation work outlined in the Consent app. was done at 4.5mm/d in winter and was only limited by N drainage not irrigation rate.

4. There is no basis provided for the implication that ”there is the possibility for SDI to bubble to the surface” under the irrigation rates expected from the 55Ha option. Did they ever model the 8 doses per day I recommended? Despite it probably being too late in the reporting process to address this I would like to see the 8 dose model if it was actually done.

5. The concluding statements by Aqualinc are misleading, particularly for the lay person. The Hydrus modelling showed that pulsing the applications (for example 4 short

pulses per day situation compared to 1 longer pulse per day) will reduce drainage

and therefore N leaching. However, it results in higher soil moisture above the

drippers compared to once per day applications, because of the lower drainage

And - The higher soil moisture conditions between the ground surface and the SDI

drippers results in a greater potential for soil moisture conditions to reach field

capacity, and under prolonged or heavy rainfall, reach soil saturation.

I think what they are saying is immediately above the drippers soil moisture will be greater. That is correct. What is not correct is the implication that wastewater from SDI flows to the surface. That’s providing the soil profiles provided in the evidence are correct.


The subtle difference between the two systems is that overall runoff and ponding volumes are probably similar. With CPI it is a combination of pond wastewater and rain runoff. With SDI it is just rain runoff.

To give additional comfort, the SDI water quality after the membrane has most pathogens removed and after further passage through the soil is even cleaner, as noted in the Consent evidence. It is very easy to create a mass balance for each irrigation type to demonstrate this

I trust these comments are useful and will be acted on.

Stantec Comment:

The difficulty is noted that it is not possible to quantify the extent to which winter ‘storage’ of ammonia will be beneficially used, rather than eventually leached as nitrate. This opportunity for N removal to be enhanced is noted in s9.2 of the Basis of Design report, and has been repeatedly discussed by those assessing SDI for the Business Case, giving confidence this matter is not being overlooked.

It is accepted that a greater application depth for SDI, based on 55Ha, is acceptable, and the SDI option is not penalised in this regard. However it is considered that the area of the irrigation field for SDI cannot be reduced below 55Ha if there is to be a fair comparison with CPI, which is compensated by greater buffer storage and a greater land application area.

The Business Case also assesses the option of CPI with membranes.

Peer Reviewer Comment:

I agree with the comments relating to ammonia N and that it has been considered appropriately in the design report and in the business case.

What is continuing to be a point of difference between reviewers is the ability for the soil to accept an increased hydraulic loading through SDI due to the high permeability of the soils, but the same soils being an extreme risk to CPI of ponding and therefore not being able to irrigate. The statement that “overall runoff and ponding volumes are probably similar” contradicts the earlier statement (item 3) that irrigation rate would not be a limiting factor for SDI. I understood the consent restricts irrigation during periods of surface ponding, which would then apply equally to both CPI and SDI if overall runoff and ponding volumes are similar. As mentioned in earlier comments, the risk of lateral movement of water across the site appears to be very low, therefore is the incidence of ponding for short periods a high environmental risk for either system?

If the membrane filtration, along with reduced nitrogen through an aerated pond system were applied to CPI, then the same benefits to SDC would be realised.

PO Box 12-499, Penrose, Auckland Phone: (09) 579-1080

www.ecogent.co.nz

17 August 2018

SUMMARY REPORT – ECOGENT REVIEW

1. Introduction

This document is a summary of key points raised by Peter Riddell from Ecogent Ltd and includes

commentary where issues have not been resolved.

The layout and section numbers in this synopsis follow that of the Design Basis Peer Review dated

25/7/2018. Other comments from the Peer Reviewer which appear in Appendix 2 of this report are also

noted where we disagree with them.

Statement of Limitation.

This summary has been prepared by Peter Riddell in the role of SDC appointed Commenter on the “Basis of

Design Report for SDI (June 2018)” prepared by Stantec which outlines a potential subsurface irrigation

(SDI) design. Where issues raised are relevant to centre pivot irrigation (CPI) these are also commented on.

While every effort has been made to explain the layout, design considerations and equipment typically

used in SDI systems the Commenter has no influence on the subsequent interpretation or acceptance of

those recommendations.

The list of comments is tabled in Appendix 2 of the Design Basis - Peer Review. The order of those was

comments on the Design Review from Peter Riddell followed by comment by Roger Oakley from Stantec

and then input from the Peer Reviewer.

Two phone conferences were held to discuss issues. Some of my comments have been accepted, some

partly accepted, and some rejected or not acted on. Where disagreement remains, the main topics are

discussed in this summary report.

I am qualified to provide this commentary based on my 47-year experience in irrigation, water resources

and wastewater. Relevant experience includes the large NZ SDI systems, irrigation throughout NZ and Asia-

Pacific, soil moisture measurement and irrigation management including for SDI, wastewater network leak

investigations, wastewater pond upgrades to high rate treatment systems with flows up to 25,000m3/d,

including storage, filtration and disinfection. After 5 years as the Water Resources Engineer at the

Marlborough catchment board I have been a consulting engineer for the rest of the time including

Our Ref#:Eco1097

Managing Director of Woodward-Clyde prior to it becoming URS. I have been assisted in this review by

Ecogent personnel Peter Gearing, who was the key designer for the SDI systems mentioned, and Marcus

Bird who was also involved in much of the above.

2. Treatment and Disposal Options

2.1 Centre Pivot Irrigation.

The Peer Reviewer comments that CPI is a common form of irrigation in rural NZ and its capabilities and

costs are well understood. This ignores some key differences and challenges of the Kepler CPI proposal.

There are only 2 other similar CPI systems in NZ which irrigate municipal waste on this scale, Taupo and

Rolleston. They operate in better conditions including all-weather irrigation and higher peak irrigation rates

without risk of ponding or runoff and do not rely on buffer storage.

They do not have restrictions on irrigation during heavy rain. Their Consents allow irrigation at about 2.5

times their Average Daily Flow (ADF). The Keppler Consent only allows 1.5 times the ADF.

Their wet weather inflows are less than twice their ADF whereas Kepler has inflows currently up to 3 times

ADF, or 3.6 times ADF when rain on the ponds is included. This is likely to get worse as the population

increases over the duration of the consent.

Taupo and Rolleston both have the capability to irrigate at a greater rate than their inflows whereas the

Kepler irrigation capability is close to half the winter storm inflow. Kepler relies on storage to manage the

difference but, as the May 2016 storm demonstrated, the proposed storage would be insufficient to

prevent overspill, and this May 2016 storm was only a mild rain event, according to Stantec rainfall

calculations. This problem of more inflow than consented irrigation is unique to Kepler and will get worse

as the population increases, and larger storms are experienced, over the next 25 years of the consent.

The other systems have a better water quality. Kepler will have a high algae load due to the 60-day

detention time in the ponds which allows algae to grow. This is not the case at the other plants and this has

implications for reducing soil infiltration ability. Kepler CPI will have a high nitrate level due to the trickling

filter. This will result in winter leaching of all applied nitrogen. This is not the case at the other schemes.

Nor is it for SDI which will have a low nitrate level as it does not have the trickling filter.

Soil conditions are also different. The other schemes are on well drained soils that do not pond and do not

have extensive soft areas that will constrain CPI wheels and require significant support. Despite the better

ground conditions, they still require gravel tracks. I expect this to be a maintenance issue at Kepler which is

not well understood.

The other schemes are more flexible and easier to operate. They have more than twice the number of CPI

units, with each irrigating only half the area that the Kepler units will irrigate. This gives considerably more

flexibility for the inevitable down time, repairs, harvesting and management of varying irrigation flows.

They do not require close operator attention to manage wet weather events, as they automatically turn on

additional CPI units to deal with increased flows without the need to avoid ponding areas, or to manage

buffer storage. The revised Kepler layout with one CPI unit irrigating about half the total area is not good

practice as, if it is out of action for any reason, the integrity of the entire scheme is at risk. Review of both

the other schemes, particularly at Taupo reveals there were a considerable number of issues including

nozzle blockage, gearbox problems, wheel rim problems, the need to construct a dedicated wheel track

gravel laying unit, GPS location drift, and wind effects on the units that needed to be overcome before they

settled down. Taupo has the luxury of having 8 units and a wastewater flow in its first 3 years operation of

only one third of its design flow, (2mm/d compared to 6.5mm/d) with a maximum allowed irrigation rate of

15mm/d which is 2.3 times the design flow and 7.5 times the average flow. This provided a massive safety

factor to allow CPI units to be taken out of service and repaired. By comparison Kepler flows as shown in

May 2016 are already exceeding the expected future consented values and there is no redundancy to take

CPI units out of action for repair. This is a significant issue for Kepler in winter where, unlike the other

schemes, it has a reduced allowable winter irrigation rate compared to the summer rate.

Other key areas that I have identified as being unresolved risks for CPI include;

• The portion of the Kepler farm where irrigation is prohibited in the Consent due to ponding. No

apparent effort has been made to define the extent of this area, despite available photos that show

prolonged flooding.

• The sloping areas leading to these pond areas that will also not be able to be irrigated due to the

runoff into the ponds. The reduced allowable flow due to these two issues will place more demands on

additional storage.

• Wheel track gravel costs and ongoing maintenance particularly the wheel tracks in localised areas of

soil that becomes soft when wet for prolonged periods. There has been no measure of the extent of

this or how it would be managed as there is no precedent in the other CPI schemes for the soft areas

identified at Kepler.

• The management of flushing which is required when the CPI units have been out of action for 2 or 3

days and how this water will be disposed of in saturated conditions.

• Aerosols which are a potential long-term issue of concern as awareness of possible health risks

increases

• Bird strike risks with proximity to the airport

• Management of the CPI system during freezing conditions, particularly as happened recently if it

follows several days of restricted irrigation

2.2 Subsurface drip Irrigation as a disposal option.

I agree that key features that make SDI suitable include variable irrigation rates making management

easier, no surface discharge, no aerosol risk, efficient water use (beneficial in summer) and discharge

directly to the root zone. Other advantages in my opinion include:

• Bird strike risk is minimised.

• There is no odour from a well-managed system.

• An easier system for the operator in times of extreme events as it can be left to operate

without concern about excess rainfall causing contaminated runoff, or frost restricting

operations.

• The very good water quality after membrane treatment which removes most pathogens, and

the discharge below ground where soil provides additional treatment.

I disagree with the context of the following comments by the Peer Reviewer.

1. “That the capabilities of SDI are well understood but the cost structures for large areas of rural

land are not well developed.”

The unit cost is based on actual installation costs from Pauanui where the Peer Reviewer had

an active role as noted in his C.V. The installation is in a Council park, under the airport and in

an urban road medium strip. It required a very high installation standard, more so than typically

expected in a rural environment. Other SDI schemes are also in a rural or semi-rural

environment including the Aluminium Smelter SDI system and at Maketu while Omaha is partly

in rural paddocks, in native bush and eucalypt plantations and a golf course. In our opinion the

cost structures are well understood. Kepler SDI costs should also benefit from economies of

scale.

2. “That nitrogen uptake requirements make this different to the other SDI systems”

The difference is that the Kepler crop will be harvested as a means of N removal. Others,

including Pauanui and Maketu reduce N in the treatment process, the Aluminium smelter

balances the N load with vegetation uptake while Omaha reduces golf course fertiliser

application rates because of the wastewater nutrient and uses the soil between the irrigation

area and the receiving environment to remove N as noted in the recent reconsenting process.

I note also that the recent Aqualinc modelling has confirmed the expected N discharge from

the 55Ha SDI area is likely to be less than that from the 70Ha CPI scheme.

3. “That the proposed SDI water quality will not be as good as at Omaha and Pauanui”

Their treatment processes were cited as the reason. On the contrary, it is probable that the SDI

wastewater, after the membrane filter, will be as good as or better than these schemes in the

important areas for SDI of TSS, pathogen reduction and to a lesser extent BOD.

Risks for SDI identified in the Design Report and subsequently resolved include:

1. Below ground infrastructure. The drip pipe has a life expectancy that exceeds the Consent life.

It also constitutes less than one third of the irrigation system components.

2. Cropping activities, are managed by using no-tillage agriculture. Land contour and drainage

paths would be improved before installing driplines.

3. Drippers are manufactured with approved root inhibitors and slime control. Algae and

particulate managed by filtration(membranes) and system flushing. This has been well

canvassed in the design and permitting of all the municipal SDI schemes and confirmed by the

longevity of the track records.

4. Irrigation would not be in a single pulse but in typically 8 pulses per day which maximises

pathogen removal in the soil and optimises water movement.

3. Points of Contention.

These are listed in items 4 to 6 below.

4. System Capacity

The magnitude of the Design Storm rainfall and inflow remains in contention. This is critical because the

system obviously must be able to operate within the conditions of the Consent in that storm and still have

spare storage for extreme events. (The detail is spelt out in NTC29). Stantec, in determining the criteria for

the design of the SDI estimated the 1 in 10-year design rainfall to be 250mm over 10 days.

In the winter storm of May 2016, the 10-day rainfall was only 130mm, which is much less than a 10-year

event, probably only a 2-year event, however it resulted in a 10-day inflow to the pond which was greater

than the Stantec modelled flow.

Whatever the cause of the high inflow it is irrefutable that the May 2016 storm, from only 130mm of rain,

resulted in a measured inflow that would have caused the CPI system to operate in breach of the consent

at Kepler or require spillage to the river.

The SDI system as proposed would be able to comply with the Consent for that storm.

Neither CPI or SDI would have been able to handle the May storm flows if rainfall had increased to the 10-

year Stantec design. This is an important issue to consider as it casts significant doubt on the validity of the

storage assumptions or the flows that can be expected. I note that one reason for this is that the long-term

flow record was based on pump hours which is not a reliable method due to performance variations.

4.1 Buffer Storage.

I consider that the proposed 15,000m3 of storage is insufficient to deal with a 2-year, let alone 10-year,

design event as evidenced by rain and flows in May 2016.

I have recommended additional storage is created outside the ponds in a new approx. 10,000m3 pond

which has the aeration included in it so that it is used as a treatment system rather than a storage system.

Water from this new pond would then pumped directly to Kepler, in the case of SDI via a membrane

system. The existing large pond would be emptied, de-sludged, modified and retained to provide about

50,000m3 of available storage. It would be maintained empty, only receiving spillage in extreme events and

this spillage would be transferred back to the treatment pond as weather permitted. This would also

address the regular odour problem at the ponds which is not addressed in the present proposal. It would

be like Omaha where the storage is adjacent to the treatment, not part of it.

I estimate this approach would be cost neutral at the ponds because of the savings it allows in other items

and would reduce other costs because of the reduction in the magnitude of the peak flows that need to be

pumped.

4.2 Mainline sizing.

I continue to disagree with the philosophy of the mainline size as it applies to the SDI irrigation option.

The first point of contention is that Stantec nominated the SDI design flow based on the premise that in the

10-year frequency storm SDI must operate using only 5,000m3 of the available 15,000m3 of storage. The

other 10,000m3 was to be retained for a more extreme event. This design requirement wasn’t applied to

CPI. It is evident that CPI could not function with only 5,000m3 but would need more than the 15,000m3 of

storage to avoid breaching the consent in what was probably only a 2-year rainfall event. The result of

imposing this requirement on SDI, but not CPI, added 1,000m3/d for 10 days, to the SDI flow requirement,

increasing sizing and costs for the membrane and pipeline.

The mainline size is determined by the consented flow for CPI of 4500m3/d and includes allowance for

managing storage imposed by CPI restrictions in storms. This restriction is not incurred by SDI. For this

reason, I consider a pipeline one size smaller than proposed would be enough for SDI. It then has

associated advantages such as reducing the required flush flows.

The increase in storage I recommend would further support the smaller pipe size for SDI and potentially

CPI. The outcome would be significant costs savings in the pipeline and membranes.

4.3 Irrigation Disposal.

The impact of saturated soils on irrigation ability is not the same for the two different irrigation types and

this is a point of contention that should be easily resolved. During heavy rain overhead irrigation will mix

with rainfall and any areas that are subject to ponding (as shown in various photos) as well as slopes that

drain to those ponded areas will have wastewater mixed with and contaminating the rainfall that runs off.

That is why in heavy rain overhead irrigation (CPI) must stop. The suggested cessation figure in the Consent

evidence was 30mm/d. The Consent also requires that irrigation does not continue over ponded areas. I

have estimated areas that pond, and areas that drain or runoff to the ponds, as being between 5% and 20%

of the total irrigated area. A 20% reduction in area to be irrigated also results in a similar 20% reduction in

the allowable flow for CPI. SDI would be located away from ponding areas. There has been no dialogue

refuting these pond area estimates and it remains a complication for CPI which should be addressed, not

just left to the design stage.

The Peer Reviewer makes several references to his concern at the proposed SDI application rate being

greater than the CPI rate and considers if there are concerns (as expressed by me) about limitations to CPI,

the same must apply to SDI. My response to that is that the consented CPI rate and the suggested

increased rate for SDI are both less than 2% of the measured 9mm/hr soil permeability. There is significant

potential to increase these rates for brief periods during storms as a possible solution to the storage

shortfall.

The irrigation rates are based on the Consented nitrogen loads and with SDI having only 80% of the applied

N then the SDI rate could increase (from 2.9mm/d to 3.6mm/d) to maintain the same N load. This approach

has been confirmed in the latest Aqualinc report which concludes that SDI on 55Ha will result in less N load

from the entire farm than will CPI on the full 69Ha.

CPI has a limitation as discussed on some areas during heavy rain. This is increased at the outer radius of

the CPI circle where brief but high rates of 20mm/hr aggravate the ponding and runoff potential in rain.

This limitation doesn’t apply to SDI as it is below ground and pulse irrigated with 8 small doses per day.

These small applications will not rise to the surface but will drain in winter and be used by the pasture in

summer. SDI will also be located away from areas prone to ponding.

Wastewater discharged from the SDI dripper will normally move in all directions by capillary action. In

saturated soils movement is by gravity and is both lateral and vertical. The only way it can reach the soil

surface is if a dripper is surrounded by low permeability materials and the only outlet is up to the surface.

This is clearly not the case here as shown by the soil investigations and with the proposed numerous small

doses.

5. Soil Properties.

5.1 Nitrogen reduction

I agree with the comment that nitrate is more mobile and note that the conversion of ammonium nitrogen

to nitrate by the trickling filter is what Stantec said will happen in the consent evidence. SDI with its

primarily ammonium nitrogen clearly has an advantage in winter in retaining nitrogen in the soil even

under saturated conditions. This hasn’t been used as a factor in comparing the nitrogen budgets but is

positive for reducing SDI leaching in winter. This advantage is recognised by the Aqualinc review but not

used in their calculations.

The Peer Reviewer comment about SDI having a 2 to 3-day benefit of outlasting CPI as soils reach

saturation ignores the Consent criteria of not irrigating ponded areas and ceasing during heavy rain. It was

stated in evidence and commented on by the Commissioners that it is common to irrigate such systems

when soil moisture is above field capacity and that hasn’t been restricted in the Consent. What has been

restricted is irrigating ponded areas. My interpretation based on this and the low irrigation rates discussed

in 4.3 above is that SDI can continue in all weather and that the “2 to 3-day advantage” comment has no

technical significance with these soils and irrigation rates.

5.2 Water holding Capacity

This has been discussed above. There is no intention to install the SDI system in the underlying gravels. It

should be installed within the top soil layers as described in the soils investigations.

5.3 Saturation and Drainage

Regardless of irrigation type, soils will typically be at or above field capacity in winter and all irrigation

applied will drain, or partly runoff. This is outlined in the evidence and accepted in the conditions of the

Consent.

As raised above in S 4.2 (Buffer Storage) I consider there will be insufficient storage and recommend the

concept of constructing a new pond for treatment and converting the existing pond for storage which

provides a solution for either irrigation system.

The Peer Reviewer suggests alternative solutions of either a bypass to the river or high rate infiltration at

Kepler. In our opinion the first would be unacceptable to most, if not all, stakeholders. The second option

of creating a separate high rate disposal area would have significant technical and consenting problems.

We note a cost estimate for this has been included in the revised CAPEX. We don’t think that cost should be

applied to SDI.

A variation of the second option, being Increased irrigation via the installed SDI, would have no additional

cost because all infrastructure would be in place. It is also likely to be a simpler exercise to vary the Consent

for. It is quite practical given the significant difference between soil permeability and the likely low

irrigation rates. It would be more difficult for CPI as it is typically needed when CPI is constrained by the

weather. This approach to manage peak flows is utilised at other SDI schemes by increasing the irrigation

rates, although the increase at Kepler would be minor by comparison.

6 Financial

I do not consider the Cost estimates are a reasonable reflection of the relative costs between the 2

irrigation options despite our discussions. There are several reasons for this.

First the SDI concept has more associated infrastructure than has been the norm for the other municipal

SDI systems in NZ. This is partly because of the apparent lack of experience with these SDI schemes by the

design team, and to a lesser extent by the peer reviewer, and partly because it has been influenced by the

CPI concept to maintain comparative cost assumptions. The sources for the SDI equipment costs appear to

be predominantly from the company which has supplied the CPI system cost. It installs CPI systems in a

competitive environment whereas the same expertise and experience with municipal SDI was not apparent

to confirm our suggested SDI layout and costs.

The SDI scheme is also over designed in terms of the instantaneous hydraulic load, which dictates the size

of major components. This is because of the design constraints applied by Stantec, particularly relating to

storage, to make it conform with the CPI concept rather than take advantage of the unique irrigation

advantages it offers.

The variation in our review of the Stantec cost estimates for SDI is between $3M and $4M, or about 20% of

the project Capex. I have detailed them in a separate spreadsheet that has not been reproduced in the final

report. Some changes were made based on my comments, but other items have been added such that the

residual difference remains.

My discussion on the cost differences is summarised in Appendix 2, Items listed under “Ecogent feedback of

7th June.”

Costs have been added to the SDI concept by Stantec since that discussion and include removal of the

southern shelter belt, only for SDI, and an allowance for a rapid infiltration field (for all systems). The total

increase to Capex of these two additions is about $1.5M and in my opinion both are unnecessary. SDI can

avoid that shelter belt and the SDI flow can be easily increased without additional infrastructure to deal

with any increased flow issue whereas the concept of rapid infiltration for CPI at Kepler is likely to become

a significant consenting challenge. As noted by Stantec (J. Cocks) the algae load would also make this high

risk without a membrane. I note also an allowance for possible installation risks have been increased to

40% of the install cost for SDI.

The CPI comparative cost has been reduced by delaying construction of 20% of the system for 10 years to

reflect the same staging flexibility that SDI has. However, this is not operationally practical as with only 2 or

3 units the only way to achieve a reduction would be by making the units smaller. The cost of this would

only be a small portion of the total, certainly not the 20% allowed for.

I also note that our suggested solution to the storage problem will result in the ability to lower costs

particularly for SDI as it removes many of the expensive components and constraints.

6. Summary

In summary I conclude that there are no fatal flaws for SDI. Modelling by Aqualinc has confirmed its

potential to provide a lower N discharge than required by the Consent. When the relative immobility of the

ammonium nitrogen in the SDI water is considered the nitrogen losses to groundwater will be even less

than indicated.

Minor changes to the Consent would be needed for SDI in terms of the irrigation rate but the parties agree

that this should be attainable as the increase is minor in the context of the measured soil permeability.

I cannot reach agreement with the review team over costs and some technical issues. To do this requires a

more pragmatic approach with greater attention to industry norms for SDI. Review of membrane

performance and testing the treated waste water at the two South Island membrane plants will help

eliminate perceived risks such as the uncertainty of algae on performance and the potential for odour that

are increasing costs. I have suggested this be done.

The system has the potential to have the same layout as all other municipal SDI systems without the

emphasis on repumping at Kepler with associated cost savings.

It is also my opinion that if the suggestion of an external treatment pond is adopted to overcome the

storage limitations, and the existing pond is used for storage, there is the opportunity for a more cost-

effective SDI scheme to be produced that will be resilient to future storms without breaching the Consent.

Increasing SDI rates to include increased irrigation in storms is also a potential solution however it would

best be done in conjunction with improving the storage.

All aspects of the ranking matrix show a clear benefit for SDI to people who understand the relative

impacts. I have highlighted the differences in Appendix 2 (Scoring Criteria, note dated 6th July). The

outstanding criteria influencing the scoring is the cost as discussed and ultimately this may only be realised

with a fresh approach and testing the market.

Peter Riddell

17/8/18

Ecogent final comment and response 20 Sept 2018 page 1

FINAL ECOGENT FEEDBACK AND RESPONSE 20/21 SEPTEMBER 2018 Final documentation of all peer review responses were forwarded to Ecogent on 14 September, completing the cycle of progressive review and response that had occurred until that point. The document below gives Ecogent’s final feedback received on 20 September 2018, with the Peer Reviewer’s response on 21 September. A few points of correction in the Peer Review document.

1. Pauanui costs were updated from 2008. Note that drip line supply costs actually reduced. Cost differences mainly relate to our different opinions on the hardware and layout finer details. Large irrigation area simply means greater economy of scale is obtained. You will have seen the considerably greater number of irrigation blocks and complexity at the other schemes, particularly Omaha to appreciate that their unit costs should be greater than we are suggesting here. – Peer Reviewer Response: Noted that costs were updated to reflect current economic conditions, and simply acknowledged that confidence of CPI costs would be more robust with the wider use of centre pivots in the rural irrigation sector. I am surprised that Ecogent could not reference any current rural installations that are being completed, I know there are a few larger area installations (irrigation only, not effluent) being done in Canterbury, but by their competition.

2. Ongoing misunderstanding of the point I have tried to make re the relative ability of SDI and CPI to irrigate in wet conditions. Rain mixes with surface applied wastewater from CPI so if there is runoff while irrigating it will be a mix of water and wastewater. With SDI it is just rainwater‐ providing the system is installed and operated correctly, ie small doses not one daily dose. In both cases, CPI and SDI, once water is beneath the surface the permeability is sufficient to drain the water, not cause it to rise to the surface unless there are localised drainage impediments. Peer Reviewer Response: We will need to agree to disagree on this point. Tony Daveron agrees with my statement in the report and I have spoken to other suppliers/installers of SDI systems and in saturated soils the irrigation water will come to the surface.

3. Site Soils and possible effect on CPI operation if soft. First, the drive over of 31 July quoted as justification is not a good example. I emailed on about 12 July that it would be worth checking conditions given the prior 85mm of rain and the anecdotal comment that the site was at that time too soft to drive on. By the time of the inspection of July 31st the average for the prior 20 days was down to <4mm/d so naturally the site would have substantially drained. The additional comments that CPI and gravel track maintenance are common in rural areas overlooks the fact that to my knowledge there are no similar situations. Most farm CPI operations would be for less than 9 months and don’t irrigate effluent unless there is storage capacity in the soil. Effluent irrigation alone would typically only require 10% of the annual application likely at Kepler because of N limits and then only in suitable times, not all weather, so track maintenance would not be such an issue. Peer Reviewer Response: Peter’s evidence was anecdotal, he did not visit site. Whilst the average over the preceding days may have been <4mm, the total for the month was 161mm, double the monthly average, and there was reasonably heavy rainfall the day before I attended site.

Ecogent final comment and response 20 Sept 2018 page 2

4. Ben commented on what might influence bird strike. I am not an expert but understand that one factor is the increased presence of worms, insects etc that surface during flooded and ponding conditions. Irrigating subsurface reduces the vertical and lateral extent of soil saturation and ponding and reduces that risk. Managing grass height, seed head development are other issues mentioned.

Peer Reviewer Response: Noted

5. Ben commented. It is also possible that the proposed trickling filter required to reduce risk of odour for the CPI system could transform ammonium nitrogen to nitrate which is much more mobile in the soil profile and could be lost through drainage when soils exceed field capacity The potential for nitrogen loss through drainage is fundamental to the existing consent conditions linked to Overseer and must be carefully considered through detailed design of the system. My comment is that the MWH expert in evidence said this would happen, not could happen. – Peer Reviewer Response: Similar to the comments below, the review I completed did not include going into sufficient detail to confirm exact performance of treatment elements such as the trickling filter, therefore my language was kept circumspect.

6. There are numerous comments about the brief expanding to include a comparison of CPI and SDI and the overall design capacity implying this is out of scope. My explanation is that because of the need to try to ensure that SDI was appropriately designed and costed and that the advantages of SDI were understood, the only way to do that was to critically consider all the design assumptions to ensure consistency between the two systems and ability to contend with extreme events. That included NTC29 and its restrictions on SDI design flow, the impact of storage, particularly the winter 2016 storm and its effect on both systems and the ability of SDI to better weather storms. These are fundamental to a reliable system regardless of type and I think the project has benefited from bringing the analyses to the fore. I also note that my brief included raising such issues if they became evident. I have previously copied you that section. – Peer Reviewer Response: as alluded to in my report there are several aspects raised through the review process that have triggered additional work or require further design input, this is a good outcome. Where they specifically impact the comparison between SDI and CPI it is my opinion that sufficient detail, costs and consideration has been included for the business case review.


Appendix H Peer Review Feedback - Ben Stratford

9/7/2018

Southland District Council Te Anau Treated Wastewater Scheme

Design Basis Peer Review – August 2018

Ben Stratford MAINLINE AQUA LTD

https://d.docs.live.net/0baa468a28691ba1/Documents/Mainline/SouthlandDistrictCouncil/TeAnau_WWTP/5-

Deliverables/PeerReview_TeAnauWWTP_BenStratford_Final_Sept2018.docx

Contents

1 Executive Summary ....................................................................................................... 2

2 Introduction .................................................................................................................. 4

2.1 Statement of Limitation ......................................................................................... 4

2.2 Project Background ................................................................................................ 4

2.3 Basis of Design Report ........................................................................................... 4

2.4 Ecogent Commentary ............................................................................................ 4

3 Treatment and Disposal Options .................................................................................... 5

3.1 Centre Pivot Irrigation ............................................................................................ 5

3.2 Subsurface Drip Irrigation (SDI) .............................................................................. 5

4 Points of Contention ...................................................................................................... 6

5 System Capacity ............................................................................................................ 6

5.1 Buffer/Balance Storage .......................................................................................... 7

5.2 Mainline Sizing ....................................................................................................... 7

5.3 Irrigation Disposal .................................................................................................. 7

5.4 Aqualinc Report ..................................................................................................... 8

6 Soil Properties ............................................................................................................... 8

6.1 Nitrogen Reduction ................................................................................................ 8

6.2 Water Holding Capacity ......................................................................................... 9

6.3 Saturation and Drainage ...................................................................................... 10

7 Financial ...................................................................................................................... 10

7.1 Basis of Unit Rates ............................................................................................... 10

7.2 Cost Estimate ....................................................................................................... 11

7.3 Contingency Values .............................................................................................. 11

8 Conclusion ................................................................................................................... 11

9 Appendices .................................................................................................................. 12

9.1 Appendix 1 – Curriculum Vitae – Ben Stratford .................................................... 12

9.2 Appendix 2 – Design Basis Report Comments, June 2018 ..................................... 13

9.3 Appendix 3 – Ecogent Comments and Peer Review Responses, July 2018............. 14

August 2018 2

1 Executive Summary The peer review for the Te Anau Treated Wastewater Scheme was intended to be a collaborative process to agree the design basis for an SDI system that was comparable to the consented CPI system for disposal at the Kepler Block.

In my opinion it became an exercise in comparing the relative merits of SDI versus CPI irrigation systems and much of the intended commentary and associated evidence has been relatively subjective. It has also expanded beyond the intended brief to include the overall design capacity and process elements of the proposed treatment system upgrade.

I believe there is general consensus between the parties on the specific process elements that are required for each system to operate within the consent conditions. However there is still disagreement on the scale of some of these elements, such as pipeline diameter, which are discussed in detail through this report.

Overall the Kepler Block appears to be appropriate for the irrigation of treated effluent from the Te Anau WWTP based on the soils investigation data. The soils have a high permeability through the upper horizon and overlay gravels with an even higher permeability. Ecogent maintain that this permeability is the key to the success of SDI and that there is sufficient capability in this system to add irrigation application depth to the site through reduction in the application area and to manage the increased flows through the treatment plant during rainfall events, reducing storage requirements. However, they contest that this permeability cannot be applied the same for the surface application of effluent through CPI, where surface ponding may be much more prevalent according to historical photos. I disagree with their position and it is my opinion that the soil permeability comparison should be able to be managed between the systems through improving land contour and drainage paths before installation, additional storage, membrane filtration for CPI and good management practise of cultivation and cropping activities. Regarding the cost comparison, SDI has been favoured through the reduced area of the disposal fields and CPI has incurred additional costs of storage, membrane filtration and maximised coverage across the site.

The cost estimates have been a major source of contention, particularly from Ecogent in relation to the perceived higher unit rates for the construction of the SDI system. I stand by my comment in regard to the confidence of supply and install costs of the CPI systems in broadacre applications. SDI systems on a scale of the Kepler block are limited and the direct reference to Pauanui installation costs are from 2008/9. Benefits of economies of scale will only be realised through the procurement process and cannot be relied on in the current review process. It is appropriate that there is a reasonable conservatism when preparing cost estimates against the current level of design detail and this approach has been applied to all unit rates, including for the CPI system. I am satisfied that a reasonable comparison of costs has been presented in the design basis report.

A further point of difference raised by Ecogent is the scale of the SDI infrastructure used for preparing the cost estimates. They have raised a concern about the design storm event and the impact on capacity of the treatment plant, storage ponds and the irrigation disposal system which is discussed further in this report. However, for purposes of the comparison between SDI and CPI systems the nominated flows to the Kepler Block must be catered for in the design elements. I agree there are opportunities for staging of certain elements that may favour SDI over CPI and that there are elements that vary in scale between the systems to ensure year-round operation is achievable. Again, I believe these variances between the systems have been adequately captured within the text of the design basis report and the cost estimates, sufficient for reasonable consideration through the business case process.

Ecogent continue to be concerned about the risk of bird strike at the airport due to centre pivot irrigators. The mechanism of how this risk will be increased by CPI rather than SDI has



not been made clear and is therefore difficult to quantify any remedial measures that might be required. The shelter belt between the airport and disposal field that remains and the adjacent mire/wetland area are established bird habitats. I am unclear on how the CPI system will add to the bird strike risk in this environment.

Spray drift from overhead sprinklers is a major community concern. However, there are options to minimise this with CPI, including through low pressure, large droplet sprinklers, or LEPA (low energy precision application) droppers which are essentially bubblers or drippers that deliver water closer to the ground surface rather than through spray. Improved treatment at the plant, through more intensive aeration and a membrane filter, will further reduce the perceived risk from spray drift. Note that the improved treatment of effluent at the plant will only improve the performance of either irrigation system at the Kepler block.

Wheel tracks are likely to present an ongoing maintenance issue as they do on most rural CPI systems across New Zealand. There are management practises, specialist equipment and cultivation options that should provide confidence that this risk can be managed at Kepler. Avoiding the bog and improving drainage channels would further reduce the risks.

The risk of frost impacting the above ground CPI infrastructure, particularly pilot tubing and solenoid valves is valid and will need careful consideration through the detailed design phase. Heat trace wiring is a possible protection measure and there are other options available.

Ecogent have raised several design aspects that could enhance either the CPI or SDI system, including improved treatment through additional aeration, off line storage, increased buffer storage, membrane filtration for CPI, optimised mainline size and possible in-line booster pumping at Kepler. I have not reviewed the technical merits of these suggestions, but they could be considered further as design stages progress.

There should be consideration when undertaking the business case review to ensure that where differences between SDI and CPI have been captured and adjusted through changes to process elements and the cost estimates, for example in a reduced application area for SDI and additional storage for CPI, that these are not repeatedly or cumulatively considered in the social, environmental or cultural sections of the business case. Residual differences between the systems that have not been sufficiently resolved in the design elements and cost estimate would then have a differing score across the business case criteria.

It is my opinion that the design basis report and cost estimates have been sufficiently challenged over the last several months to offer SDC a reasonable comparison between CPI and SDI systems for consideration in the business case review.

August 2018 4

2 Introduction

2.1 Statement of Limitation

This Peer Review Report has been prepared by Ben Stratford of Mainline Aqua Ltd, as an independent consultant. The terms of reference for the review are limited to the Stantec Basis of Design Report, comparison of alternative land disposal options at the Kepler Block, specifically subsurface drip irrigation (SDI) versus the consented centre pivot irrigation (CPI), and responses to Ecogent commentary.

The key objective of the peer review is to ensure a fair and reasonable comparison between the CPI and SDI land disposal options at the Kepler Block through development of the Design Basis Report. The Design Basis Report will then be considered further through the Business Case process.

I am qualified to undertake the review based on my 20 plus years involvement in civil, municipal and irrigation development projects. I have over 14 years’ experience as a consultant engineer to municipal, commercial, industrial and rural clients, culminating as a Principal with URS NZ Ltd in 2014 after which I set up my own consultancy business.

My curriculum vitae is included in Appendix 1 for reference.

2.2 Project Background

Presently, the discharge from the Te Anau ponds is via a wetland to the adjacent Upukerora River. The consent for this discharge expires on 30 November 2020.

Commencing 2005, SDC have been seeking to identify and consent a suitable land disposal site, so that the Upukerora discharge could cease. A 25yr consent was granted in January 2017 for disposal via CPI to a block of land north of the Manapouri/Te Anau airport. This is a 125 Ha site known as the Kepler Block, of which approximately 115 Ha is permitted in the consent to be irrigated.

After submissions from stakeholders, Southland District Council (SDC) agreed to ensure there was sufficient design information to enable a robust like for like comparison between the relative merits of CPI and SDI.

2.3 Basis of Design Report

The peer review role for this project was identified in February 2018 and I was engaged by SDC in March 2018 to collaborate with Stantec and Ecogent representatives to prepare a balanced Basis of Design Report for the SDI disposal option.

As part of the collaborative approach to this review I prepared a schedule of comments against the draft Design Basis Report which were submitted to SDC in June 2018. I am satisfied that these comments have been addressed in the final version of the report, either incorporated in the technical requirements or addressed in the supporting commentary. A copy of these draft report comments is included in Appendix 2 for reference.

2.4 Ecogent Commentary

Ecogent have submitted a number of comments relating to the CPI and SDI disposal options, and also wider commentary on a number of key design aspects such as the incoming flows, future storm events, mainline hydraulics etc. Whilst some of these comments are not directly related to the comparison between SDI and CPI, I have provided my own comments where applicable.

Individual responses to the collection of Ecogent comments made over the duration of the review process are tabled in Appendix 3 for reference.



3 Treatment and Disposal Options

3.1 Centre Pivot Irrigation

Centre pivot irrigation (CPI) is the currently consented disposal option to the Kepler Block. CPI is a common form of irrigation across rural New Zealand, the capabilities are well understood, as are the cost structures to import and install the infrastructure.

Key features of CPI that make it suitable for land disposal include:

• Reasonably cost-effective capital investment per hectare to irrigate large areas.

• Variable application rates through speed of rotation, sprinkler selection and VRI options that can target or avoid specific locations across the irrigated area.

• Sprinkler options to assist in reducing possible aerosols and reduce atmospheric losses (beneficial through summer months where incoming flows are not likely to maintain optimum soil moisture conditions for crop growth)

• Above ground infrastructure that is easy to service and upgrade.

• Minimal below ground infrastructure allowing physical cropping activities to be completed, such as ripping, aeration and cultivation.

The main risks of CPI identified by Ecogent and subsequently addressed through changes in the design report, include:

• Surface application of treated effluent that could reduce the number of days irrigation can safely occur during extended rainfall events – additional storage has been included for CPI over and above that for SDI. Note that total quantum of storage required for either option is still to be resolved.

• Quantification of ponded areas identified in photos that will be a risk to surface application – land contour and drainage paths would be improved before installing infrastructure. VRI has been included in the cost estimate and prescription maps would be applied to avoid drainage paths and higher risk areas.

• Individual pivot tower wheel tracks that will require ongoing maintenance – allowance for gravelling of wheel tracks has been included in the cost estimate. Ecogent continue to disagree that this risk is understood, however the repair of wheel tracks across heavily irrigated pasture is a common practise across New Zealand farms. Without subsurface infrastructure the wheel tracks could also be repaired during the drier months through cultivation activity.

• Aesthetics of large infrastructure in the region – with the remaining shelter belts, CPI infrastructure will largely be obscured from the air strip and the road.

• Spray drift, depending on sprinkler selection – additional costs have been included for longer droppers, LEPA or equivalent low pressure, low level applicators. I agree that perception will be more difficult to allay than reality.

• Exposure to frost conditions – this risk is well understood and not considered a significant cost. Specifics should be finalised in detailed design and related costs would be managed within the current budget forecast.

3.2 Subsurface Drip Irrigation (SDI)

Subsurface Drip Irrigation (SDI) has been nominated as a viable alternative disposal option to the Kepler Block. SDI is a less common form of irrigation across rural New Zealand, more commonly found in vineyards and orchards. The capabilities relative to water efficiency and placement of water in the root zone are reasonably well understood, but the cost structures to import and install the infrastructure across large areas of rural land are not well developed.

Key features of SDI that make it suitable for land disposal include:

August 2018 6

• Variable application rates through adjusting run times to each irrigation zone. Often control programmes are set up to “pulse” the daily application depth through several cycles, hours apart.

• There is no surface discharge through SDI, removing the risk of aerosols and reducing atmospheric losses.

• SDI is at the higher end of irrigation options for efficient water use (beneficial through summer months where incoming flows are not likely to maintain optimum soil moisture conditions for crop growth).

• Discharge of treated effluent within the root zone which could extend the number of days irrigation can safely occur during extended rainfall events.

• Reduced exposure to frost conditions – whilst most SDI infrastructure is sub surface and generally protected from frosts, the control valve pilot tubing and small diameter air relief and other valves will still require protection. This risk is well understood and should be finalised in detailed design. Specific costs would be managed within the current budget forecast.

The main risks of SDI that are further considered in this report, include:

• Below ground infrastructure that is not easy to service and upgrade.

• Physical cropping activities such as ripping, aeration and cultivation need to be considered carefully or not undertaken above SDI infrastructure. No-tillage cropping activities and precision agriculture will minimise risk of physical damage.

• Small diameter drippers that could become blocked through root intrusion, algae or other particulate, reducing the application ability. Root inhibitors are included in the drip line pipes, with filters and flushing protecting against algae and slime build up.

4 Points of Contention Through the process of reviewing and updating the Basis of Design report there were a number of comments made that were perceived by Ecogent to be ignored by the design team and review process.

Individual review comments for the Basis of Design report and Ecogent commentary are included in the Appendices.

The following sections have been prepared to further discuss the key areas where there is still a perceived difference in opinion relating to the benefits and constraints between the CPI and SDI disposal systems.

5 System Capacity The main design aspect that Ecogent insist is not being considered appropriately for CPI is the maximum storm event that should be contained, treated and disposed of through the Kepler Block irrigation system. It is my opinion that this aspect is critical to both CPI and SDI irrigation systems and should be confirmed as soon as practicable.

There has been repeated reference to a particular storm event in May 2016 and photos of subsequent surface ponding that occurred on the Kepler Block. The return period for this storm event has not been confirmed, but anecdotally it seems that it would be within the expected design capacity of the treatment and disposal system. Ecogent raised concerns that the May 2016 storm was possibly a 1 in 2 year event and that their modelling indicated the design infrastructure could not contain it, particularly at the winter flow rate to disposal of 2,000 m3/day. This potential constraint would apply to both CPI and SDI systems.



This raises two questions, was the May 2016 storm actually a 1 in 2 year event, and what is the storm event appropriate for the design basis? In comparison with several years of recorded flow data this storm event seems to exceed the flows that the design storm would reasonably produce at the treatment plant.

There were three key infrastructure items that were subsequently questioned by Ecogent through the review of the Basis of Design report, balance storage, mainline sizing and impacts to both the CPI and SDI disposal systems.

5.1 Buffer/Balance Storage

Hydraulic modelling of the May 2016 event indicated that the proposed 15,000 m3 of storage may not be sufficient to manage the treatment plant inflows if irrigation is limited to the 2,000 m3/day through the winter months.

Subsequent modelling by Aqualinc indicated that irrigating to field capacity at the Kepler Block (through CPI or SDI), rather than constraining to the daily limit, would have required a balance storage in the order of 25,000 m3.

Whilst this discussion is valid in terms of setting the limits of the detailed design and capacity of the treatment plant system, the main differentiation for the land disposal options is perhaps 2-3 days of additional irrigation for SDI in taking the soils from field capacity to saturation. It is likely that CPI would cease sooner due to ponding resulting from the cumulative depth of rainfall and irrigation on the soil surface.

Note that allowance for additional storage volume was included in the cost estimate for CPI to reflect the potential differentiation between the disposal systems.

Further discussion relating to the soil capacity is discussed later in this report.

5.2 Mainline Sizing

Pipeline sizing is simply a function of flow required to be delivered to the Kepler Block. This is currently defined at 4,500 m3/day and pipe diameter is therefore a function of the economical balance between flow velocity required to transport air and sediment along the pipeline, length of pipeline (friction losses) and reasonable power input at the pump station.

Booster pumping part way along the mainline and in-line pumping at Kepler would be considered through optimisation during detailed design.

If the storm event, and flow rate, are adjusted through detail design there will be opportunities to consider additional storage versus reduction in pipe diameter at that time.

For comparative purposes between CPI and SDI there is no reasonable explanation to change the pipe diameter for either option.

5.3 Irrigation Disposal

The May 2016 storm event and associated photos indicate evidence of soil saturation at the Kepler Block. It appears to have been a sustained rainfall event over multiple days where the normal moisture losses from a soil, through evapotranspiration and drainage, were unable to clear sufficient storage capacity in the soil profile for the following day’s rainfall.

The application of an irrigation depth between 2.9 and 6.5mm over and above the rainfall depth would further exceed the soils capacity to store moisture and would exacerbate the surface ponding.

There is a definitive limit to the depth of irrigation that can be applied to the Kepler Block through either SDI or CPI systems and this needs to be considered in conjunction with the balance storage requirements at the treatment plant.

August 2018 8

The implication of saturated soils would be the same for both CPI and SDI disposal systems and is a function of the soil properties discussed in the following section. I understand the consent limits irrigation over ponded areas, and it would be reasonable to think that this would also limit irrigation beneath ponded areas.

The spatial variability of the surface ponding indicated in the photos referenced by Ecogent would be difficult to specifically avoid through SDI field layout or CPI VRI prescription maps. Land contouring and improving drainage channel alignment would be required before installation of either system.

5.4 Aqualinc Report

Aqualinc have recently completed a report entitled Te Anau WWT Irrigation – Storage Requirements and Frequency to determine the temporal distribution of storage requirements using a long-term climate record and likely waste water flow. From these results the frequency of different storage requirements were estimated.

This report expanded on the previous modelling undertaken by Stantec and included several increases to the anticipated future wastewater flows, including:

• Population increase – a 1.34 factor was adopted across population increases to 2042.

• Peaking factor – higher peaking factors were adopted to reflect an increase in inflow and infiltration to the wastewater network.

• Adjustment factors were applied to recent flow data, calibrated to the May 2016 storm event.

This report confirmed that additional storage would be required at the treatment plant for both CPI and SDI disposal options. The ultimate storage capacity to fully capture and manage every predicted storm event by 2042 is considerable and a staged approach to implementing the additional infrastructure is recommended. This will defer capital expenditure, but more importantly allow collation of wastewater flow and disposal system performance data to compare with model predictions and adjust planning and implementation accordingly.

SDC and the design team have discussed the Aqualinc report and confirmed a staged implementation with the following storage options for the Design Basis Report:

1. Stage 1 as either: a. SDI – a maximum of 22,000m3 b. CPI – a maximum of 30,000m3

2. Stage 2 to be determined in the future subject to monitoring of actual WWTP and irrigation performance, and actual effects of growth and climate change.

I consider that the analysis completed by Aqualinc is sufficiently conservative in predictions to provide confidence for SDC to proceed with the recommended storage options for consideration in the business case for SDI or CPI disposal.

6 Soil Properties

6.1 Nitrogen Reduction

Nitrogen levels in wastewater are reduced through several mechanisms in the proposed treatment system, including biological processes within the pond system and soil profile, physical removal through membrane filtration and through plant uptake.

The treatment process for SDI includes a membrane filter to reduce particulate matter in the effluent so it can pass through the dripper system. The membrane filter is expected to



reduce the nitrogen levels in the effluent by about 20% and the area required for the base case SDI system to remove the remaining nitrogen has therefore been reduced by 20%.

Note that decreasing the application area by 20% due to the improved nitrogen reduction for the SDI system causes a relative increase in the irrigation application depth. This has the potential to negate the perceived 2-3 day benefit of SDI outlasting CPI as soils reach saturation.

It is also possible that the proposed trickling filter required to reduce risk of odour for the CPI system could transform ammonium nitrogen to nitrate which is much more mobile in the soil profile and could be lost through drainage when soils exceed field capacity.

The potential for nitrogen loss through drainage is fundamental to the existing consent conditions linked to Overseer and must be carefully considered through detailed design of the system.

6.2 Water Holding Capacity

Water holding capacity is the ability of a soil to hold water within the soil profile, essentially a storage volume. It is typically represented as a depth of storage per metre depth of soil with units of mm/m.

There are several reference terms to be considered when discussing water holding capacity:

• Field capacity – moisture content in the soil profile after excess water has drained away.

• Saturation – moisture content when all soil pores are full, additional water ponds at the surface or exits the profile through drainage.

• Wilting/stress point – moisture content where the plant cannot uptake sufficient water to maintain growth function and turgidity, plants start wilting.

Good irrigation management practises seek to maintain a soil moisture content between field capacity and wilting point for optimum soil and plant health.

The ability of a soil to hold water within the profile is not affected by the application type, either CPI or SDI. It is generally a mass balance consideration with inputs (rainfall and irrigation) and outputs (evapotranspiration and drainage) moving the storage volume (moisture content) between wilting point and saturation.

Where SDI may have some benefit over CPI is in the transition from field capacity to saturation. As field capacity is exceeded, the ability of a soil to absorb water from the surface lessens and ponding will become evident 2-3 days sooner than is likely with the SDI system. If the rainfall continues then SDI will eventually saturate the soils and cause excess drainage and surface ponding.

Regardless of the application type, as the soils transition from field capacity to saturation, drainage to the underlying gravels will increase.

Ecogent also state that the SDI system is less likely to pond at the surface due to the permeability of the soil profile as shown by the soil investigations. It is my opinion that the high permeability rates should therefore be applicable to the CPI application rates as well.

There could be a deterioration at the soil surface from CPI due to algae build-up and poor site management (more of a risk if grazing livestock), but this risk is minimised if membrane filtration is added to the CPI option. There are also physical activities that can be implemented to further improve surface permeability, should it decline over time.

As previously mentioned, the spatial variability of the surface ponding as indicated in the aerial photos could overly complicate the field layout for SDI in order to avoid these areas. If surface ponding does occur then it could render an entire field out of action for irrigation,

August 2018 10

pending confirmation that irrigation on surface ponded areas cannot occur from above or below that area.

Land contour and drainage paths would be improved before installing either the CPI or SDI system to reduce the risk of surface ponding. Both systems would avoid the permanently wet or bogged area.

The proposed VRI option for the CPI system will allow adjustments to be made to the prescription maps, allowing the system to avoid ponded areas if/when they develop.

6.3 Saturation and Drainage

Managing these two parameters through balance storage and control of the land disposal system are key to the success of the proposed treatment system.

When a soil becomes saturated, whether by rainfall or irrigation, further application of effluent to the soil will likely be lost through surface ponding and potential run-off and drainage direct to the underlying gravels.

Both CPI and SDI systems provide control flexibility in regard to varying the rate of water applied during an irrigation event. SDI has the added ability to “pulse” multiple applications of small amounts of effluent throughout a day. CPI is constrained to typically a single application per day based on length and rotation speed of the pivot. Note that CPI is simply a single, short duration application per day, and based on the site infiltration rates should not cause prolonged ponding or run-off unless the soils are at saturation.

As can be seen by the May 2016 storm event, and the relatively small application depth of effluent from either CPI and SDI, the limiting factor at the disposal field will likely be extended periods of rainfall.

It is therefore critical that SDC and the designer’s clearly define the storm event that is required to be contained and treated, which will then determine the hydraulic capacity of the infrastructure. Previously we had worked from a top down approach, where a predetermined flow rate must be disposed of across a fixed area. The preferred approach would be to design an irrigation system from the soil and crop up, focusing on optimal crop production and the hydraulic capacity within the soil profile, with the final design aspect being the flow rate that can be managed at the Kepler Block. This would be a bottom up approach to the design and the appropriate way to confirm the balance storage required at the treatment plant to manage the future wastewater flows from the community.

The Aqualinc report discussed in Section 5 defines the hydraulic capacity of the Kepler Block under a wider range of wet weather events, using both historical and future prediction data, and provides improved confidence in the design of the upstream storage, treatment and delivery systems to the disposal site.

7 Financial As part of the development of the Basis of Design report for SDI, a cost estimate was prepared to form the basis of comparison in the Business Case process. As can be seen in the appended review comments, there were many aspects of the cost estimates that were considered.

7.1 Basis of Unit Rates

The main aspect of the cost estimate that was adjusted was the relative unit rates to ensure consistency between the disposal options. This approach is necessary to ensure a like for like comparison can be confidently made when assessing economic criteria between the disposal



options. Relative costs for pump stations, building types, pipe installation and other rates were adjusted to ensure consistency between the CPI and SDI schedules.

It is my opinion that the relative unit rates in the cost estimates are now reasonable and appropriate for the Business Case assessment between the options.

7.2 Cost Estimate

The cost estimate has also been updated to reflect the necessary process elements that were agreed through the review for both the CPI and SDI systems. This included specific treatment elements such as membrane filtration, bio trickling filters, hypochlorite dosing, SDI field layout etc. that contribute to the overall scale of the cost estimate.

Where there were specific benefits identified for either disposal system, allowances were made in the schedule to reflect these. Key examples are the additional balance storage for CPI and the reduced area (20%) of the disposal field for SDI.

It is my opinion that the overall cost schedules for both CPI and SDI are now reasonable and appropriate for the Business Case assessment between the options.

7.3 Contingency Values

The cost estimate included contingency values for specific risks within elements of the schedule, and then applied further contingency to that overall element. What this does is exacerbate the overall element cost based on a risk that may or may not eventuate.

It was suggested that risks for specific elements in the cost schedule should be removed from the comparison and form part of a costed risk register that takes into account the scale of the risk and likely occurrence. The costed risk register would then form the basis of the overall contingency value that is applied to the respective cost schedules.

I understand this has been considered and applied where appropriate through the cost estimates.

8 Conclusion Through a collaborative approach to the review process, the design basis report and cost estimates have been sufficiently challenged over the last several months to offer SDC a reasonable comparison between CPI and SDI systems for consideration in the business case review.

The relative unit rates in the cost estimates are reasonable and appropriate for the Business Case assessment between the options.

It is therefore my opinion that the overall cost schedules for both CPI and SDI are also reasonable and appropriate for the Business Case assessment between the options.

August 2018 12

9 Appendices

9.1 Appendix 1 – Curriculum Vitae – Ben Stratford

BenStratford_CV_Feb2018.docx Sunday, 11 February 2018

Ben Stratford

[email protected]

029 355 1381

Water Design & Management Specialist

Ben has a unique combination of work experience, with nearly 20 years in designing and

maintaining water, wastewater and irrigation systems. His work has gone from hands on

farming work and running his own business to working in the troubleshooting and

maintenance side of pump station and pipeline systems, working as a consultant design

engineer on larger projects throughout Canada, Australia and New Zealand. He brings a very

practical, high level approach to system design, focusing on outcomes for the entirety of the

project rather than on the minute detail.

His main roles include project and design management, route optimisation, hydraulic and

civil design, with a particular focus on constructability and operational efficiencies. By

understanding the construction and operational requirements of a system and being able to

share this knowledge with the project team is why he can ensure the best long-term

outcomes for the project.

AREAS OF EXPERTISE

• Project Management

• Irrigation Hydraulics and System Design

• Water and Wastewater Hydraulics and System Design

• Team Leadership

• Budget Management

• Strategic Planning/Analysis

• Process Improvements

• Change Management

• Relationship Building

• Consenting Processes

RELEVANT EXPERIENCE

Mainline Aqua Ltd – Director, September 2014 – Present

North Otago Irrigation Company – Technical Manager, September 2014 – Present

(independent contractor through Mainline Aqua Ltd)

URS NZ Ltd, Principal – Water Group, 2005 – September 2014

Kellogg Brown & Root Pty Ltd (KBR), Brisbane, 2003 – 2005

Consultant, Lake Taupo, New Zealand, 2000 – 2003


PROJECTS

Irrigation Scheme Expansion – North Otago Irrigation Company (NOIC), $50m

• Ben was technical lead for the development of the concept design, engineering

design basis and cost estimate for the share prospectus issued to farmers in October

2014.

• Development of the Principals Requirements for the physical works construction

contract.

• Project technical lead for NOIC, representing shareholder irrigation demands and

guiding the coordination between design and construction effort.

Key Achievement: Ben’s experience on-farm and on large infrastructure projects was an

invaluable link between the shareholders and design/construction team during the

alignment and overbuild optimisation of the Stage 2 expansion project, adding a further

10,000 Ha of irrigable area.

Irrigation Optimisation – North Otago Irrigation Company (NOIC)

• Ben was technical lead for the optimisation of the Stage 1 infrastructure, installed as

part of the North Otago irrigation scheme off the Waitaki River.

• Identify hydraulic constraints and control issues that initiated development of new

formed suction intakes for each of the 2.5 MW main pumps.

• Develop a roster schedule for shareholders during peak demand and initiate air

management improvements across the gravity pipelines.

Key Achievement: As an independent, Ben applied an objective review process to many

operational and control issues that occurred in the original Stage 1 construction,

identifying several major upgrades that have been implemented as part of the Expansion

project.

Pauanui WWTP Disposal System – Thames Coromandel District Council

• Ben was Design Manager for the URS team providing the irrigation scheme design

for the Pauanui WWTP treated effluent disposal system.

• Coordination of the pump station, pipeline and subsurface drip irrigation (SDI) design

and control through road verges and sports fields.

Key Achievement: Ben’s unique skill set that includes irrigation design experience along

with large pump station and pipeline design helped take the concept disposal system

through to detailed design and construction.

Maketu Wastewater Disposal System Review – Western BOP Council

• Ben completed a peer review of the land disposal system for the Maketu

Wastewater Treatment Plant (WWTP).

• The review was intended to advise Western Bay of Plenty (WBOP) of the suitability

and operability of the installed infrastructure as part of the land disposal system.


• The report deliverable made recommendations on outstanding or incomplete items

from the construction contract, offering solutions for remedial works to be

completed.

Key Achievement: Ben’s technical knowledge of irrigation systems allowed him to

complete the peer review of the subsurface drip infrastructure, and he also provided

advice on enhancements to extend the operation and performance of the system.

Howick Diversion – Watercare Services Ltd, $25m

• Ben was Design Manager for the 600mm diameter trunk gravity sewers, 500 L/s

wastewater pump station and 500mm diameter pressure main as part of the

improvements to the Howick and Bucklands Beach wastewater network.

• The infrastructure is required to divert flows from the over-capacity existing Howick

trunk network towards East Tamaki.

Key Achievement: The additional capacity relieved in the network would allow

development restrictions currently in place across the catchment to be released.

Christchurch City Earthquake – Water Supply Reinstatement

• Ben was requested to work with the Christchurch City Council water supply team in

response to the February 2011 earthquake in Christchurch.

• Strategic assessment, design and reinstatement of the trunk water supply network,

including pump stations, pipelines and reservoirs.

Key Achievement: Ben’s coordination role between City Care (network contractors

responsible for repairs), Christchurch City Council and network operators was critical to

the success of returning water supply to the many of the trunk reservoirs located in the

Port Hills.

North Harbour No. 2 Watermain, Watercare Services Ltd, $260m

• Ben was Project Manager for the investigation of route options for a second North

Harbour watermain to run between the Titirangi No. 3 reservoir at the Huia

treatment plant and the Albany reservoirs.

• The 900-1200mm diameter watermain will stretch approximately 35 km across west

Auckland through various communities and natural landscapes.

Key Achievement: Ben was responsible for a comprehensive constraints analysis and

risk assessment process to deliver a preferred route option and capital budget

requirements to progress the project to consenting, detailed design and construction

phases.

FEED Design – Moranbah CSG Water Management System, Arrow Energy

• Ben coordinated the Auckland based civil, structural, mechanical, electrical and

hydraulic design team for the Front End Engineering and Design (FEED) of the

balance of plant required for the proposed RO treatment system for water

management from the Moranbah CSG project.


• The water management system comprises a series of storage pond facilities

collecting from the well heads and compressor stations, with a peak volume of

approximately 2.0 ML/day.

• Treatment and disposal options included forage crop irrigation, dust suppression,

reuse in local mines, and possible discharge to the Isaac River.

Key Achievement: Ben was responsible for the hydraulic and civil design teams between

the Auckland, Christchurch and Melbourne offices, with the project site in northern

Queensland. His ability to travel as required and communicate effectively across a range

of mediums ensured the FEED design documentation was pulled together for the client

on time and within budget.

Papamoa Pipeline, Tauranga City Council, $40M

• Ben was Project Manager for the development, consenting and design of a 12 km,

500 mm diameter trunk sewer pipeline through the Papamoa community to service

future development in the south east catchments of Tauranga.

Key Achievement: Ben’s network rationalisation and development of staged upgrade

options allowed the client to spread capital expenditure over the next 20 years while

maximising use of existing assets.

Southern Pipeline, Tauranga City Council. $100M

• Ben completed a range of tasks for the Southern Pipeline project including network

planning, route assessment, cost benefit analysis (technical lead) and design tasks.

• The Southern Pipeline is a 14km, 800 mm diameter interceptor sewer pipeline across

Tauranga, required to divert current and future wastewater flows from the Chapel

Street WWTP to the Te Maunga WWTP

Key Achievement: By optimising existing infrastructure and designing for future

requirements, Ben enabled further developments in the south western catchments of

the city to be released.

Tahuna Wastewater Treatment Plant Upgrade, Dunedin City Council, $6M

• Ben was hydraulic design lead for the design of a 700 kW pump station for the new

ocean outfall constructed as part of the Tahuna WWTP upgrade in Dunedin.

• The pump station design was based on a reduced hydraulic grade line through the

pump station and ocean outfall, lowering the physical profile of the civil structures

required in the secondary treatment process (able to be constructed at or near

ground level).

Key Achievement: Ben’s understanding of the proposed secondary treatment process

upgrade works (to be built approximately 6m above ground) identified an efficient

hydraulic design for the pump station that has saved Dunedin City Council many

$millions in expensive infrastructure.


QUALIFICATIONS, TRAINING & AWARDS

Bachelor of Agricultural Science (Irrigation and Water Technology, Waste Water

Management and Soil Water Conservation), Massey University, New Zealand, 1991-1994

Mechanical Engineering—Stage 3 (Mechanical design and Thermo dynamics), Manawatu

URS Project Management Certified – 2011

Rogen Client Relationship Training – 2011

Ross Sharp Marketing Award (URS) – 2013

Client Account Manager (Watercare) – 2012 through to leaving URS in 2014

Water Group Manager (URS) – January 2010 to December 2013

Project Innovation Award (URS) – 2007



9.2 Appendix 2 – Design Basis Report Comments, June 2018

Te Anau Treated Wastewater Scheme, Basis of Design, Subsurface Drip Irrigation Peer Review Comments – June 2018

The following document captures my review comments to the updated Basis of Design report, June

2018, including the cost estimates.

1 Basis of Design Report

1.1 Item 1.4 Cost Estimates The report does include cost estimates

1.2 Item 2.1 Ensuring Fair Comparison The peat bog appears to be a point of contention for the comparison. I understand that SDI would be

installed around the bog, not through it. Could CPI also be configured so the wheel tracks do not pass

through the bog? This would add a premium to CPI (possibly and additional part circle pivot) but will

allow a fairer comparison with SDI.

Note that VRI sprinklers would allow this area to remain unirrigated.

Can the peat bog be drained to minimise the risk?

Higher hydraulic loading through SDI and a staged construction process pose a saturation risk to the

soils at the disposal site. Whilst focus has been placed on the reduced N through the membrane filters

and subsequent reduction in area, this simply applies a greater depth of irrigation. Regardless of surface

or subsurface application, if the soil is at field capacity, then any excess water will drain or pond.

1.3 Item 2.2 Transfer Pipeline Size Lifespan should be consistent between text and table 6-1, 80 or 100 years?

In my opinion the transfer pipe size will be the same for both options, the hydraulic load from the future

incoming flows will be what it is. Assuming the disposal field can take the hydraulic load through either

CPI or SDI, then the peak flow rate is the same and therefore the design of the pipeline should be

consistent.

If there is some issue at the disposal field, waterlogging, ponding, breakdown etc. then the only way to

manage this would be through additional storage at the pond site. SDI may reduce this risk, refer to later

comments.

1.4 Item 6.2.1 Non-Contestable Consent Conditions If the 4,500 m3/day is non-contestable then the pipe size is fixed within the design parameters such as

velocity, sedimentation and air transport requirements.

1.5 Table 6-1 Minimum Life of Major Components Main pipeline refers to 100 years, but in the document text it states 80 years in sections 2.2, 6.3.3 and

6.3.4

1.6 Item 6.3.4 Future Capacity I would expect that SDC have a philosophy to continue improvements in reducing infiltration and inflows

to the collection network and would expect that peak flows identified have a level of conservatism.

1.7 Item 7.1 Existing Ponds Risk mitigation measures could include removal and treatment of biosolids, and lining the ponds to

reduce leakage.

1.8 Item 7.2 Additional Storage Additional storage at the front end of the system is likely to be relatively low cost to install in the future

if it is required. This will allow further buffering of the system if peak flows exceed expected growth or if

there are issues at the disposal fields (either through hydraulic load or operational constraints).

It is important to note that SDI and CPI have the same hydraulic load on the soils. If the area for SDI is

reduced due to N reduction through the membrane filter then the hydraulic load on the soils is

effectively higher.

Generally the primary benefit of SDI under normal irrigation is to use less water to grow more crop. In a

wastewater disposal application this is not an option as the flows entering the system are fixed.

Heavy soils still have the risk of becoming waterlogged with the same or higher hydraulic load through

SDI.

1.9 Item 7.3 Pond Outlet Screen The main pond outlet screen only references a 200mm level difference. If this is required to suit the

15,000m3 storage, then this would equate to a 7.5 Ha pond. I understand Pond 1 is somewhat smaller

than this?

1.10 Item 7.5 Membrane Filtration If the MF plant is installed as a smaller unit with a bypass, would the bypass (untreated flow) be

considered for daily flush of the main pipeline?

To flush with treated flow only (assuming bypass would only occur when incoming flow exceeded the

MF capacity, not for flushing) it will require a 346 m3 balance storage. This is based on the flow

difference of 52 -28 L/s for a 4 hour flush.

1.11 Item 7.6 MF Balance Tank This balance tank is required to meet the variance between MF flows, backwashing cycles, and the

transfer pipeline pump station.

Total volume will need to cover both the MF flow balance and meet flushing volumes if a staged

approach is adopted.

1.12 Item 7.12 Control Valve Unsure of the details of this valve, but assume it is a hydraulic control valve with pressure sustaining

capability? There could be an additional actuated valve that mechanically closes on a drop in pressure if

this control valve fails.

The Kepler Balance Tank/Pond could also be sized to accept the pipe volume that physically could drain

under gravity conditions if the control valve failed.

1.13 Item 7.13 Kepler Balance Tank The requirement for the control valve and balance tank needs to fully understood. There is an option for

CPI to include the MF treatment which would remove the need for the trickling filter. Therefore could

the transfer pipeline connect direct to either the SDI or CPI system without the hydraulic break?

1.14 Item 7.18 SDI The potential for the peak flow is real and if the area for SDI is reduced based on reduced N through the

MF, then the consented 6.5mm per day application will be exceeded.

Are the soils at the Kepler block stoney? I understood they were heavier clay soils with minimal risk of

stones or gravels being present.

1.15 Item 7.18.1 Initial Daily Flow of 3,600m3/day Will still need to have the ability to deliver the maximum flow to flush the pipe. This can be achieved

with SDI, but at a higher application rate if the area has been reduced. It could be achieved through CPI

if pivots are sized and nozzled appropriately, particularly if an additional unit is installed to help avoid

the peat bog. This provides flexibility to run one or more pivots at a time, depending on incoming flows.

1.16 Item 7.18.4 Minimum SDI Field Area I accept the reduced area for SDI based on the improved N loading through the MF, provided the soil

water holding capacity can manage the additional hydraulic load.

The further reduction in area based on the staged capacity applies to both SDI and CPI.

1.17 Item 7.18.9 Higher Future Flows Higher flows can be applied through more SDI areas open at the same time. Similarly there could be

multiple CPI operating together, or the nozzle package could be changed (a relatively cost effective

upgrade).

Again, higher flows mean higher hydraulic load on the soil regardless of application system so risks

between systems are comparable.

2 Cost Estimates The following comments relating to the cost estimate are not based on market enquiries, rather on

general comparisons between the options and my experience in developing similar cost estimate

schedules for clients.

2.1 Item 1 – Prelim and General This seems to be double counting where many P&G items are covered in various sections including

individual item contingencies, 12.7 (the second one), 12.8, 12.9,13 and 14.

It may be more reasonable to have a separate risk section which captures these specific items and can

then form the basis for the overall project contingency for the various options. This would also be valued

through the evolving risk register for the project.

2.2 Item 2 – Additional Storage I believe this is an environmental risk for both CPI and SDI systems and would cover issues from

unforeseen infiltration or inflows, operational issues, disposal site issues etc.

There is certain value in deferring additional capital spend on storage, but it really applies to both

options in my opinion.

Scope Risk Contingency items as a percentage should be applied to the subtotal of each option, not a

single subtotal. It does not currently reflect the contingency value against the costs – this seems to be

applicable to all Scope Risk Contingency items.

2.3 Item 5a and 5b – Membrane Filtration Item 5a should have a larger balance tank to allow a specific duration of flushing flows, refer to

comment 1.10.

I am not an expert in MF filtration but would expect that algae risk at about 10% is excessive,

particularly with a further 15% contingency on top of this item.

I would prefer to see the risk elements grouped together as per my earlier comment.

Items 5.17A and 5.17B seem to indicate there will be no screening of MF bypass flows required for the

CPI option? I would expect some screening would be required, particularly if you refer to my comment

2.4 regarding the requirement for odour control if an MF system is also installed.

Building costs seem excessive – this is applicable to all building cost items, ranging in similarity to a mid

to high end residential construction cost.

2.4 Item 9 – Odour Control If odour control is not required for SDI with MF treatment then it shouldn’t be applied to Option 2A and

2B.

Balance tank sizing should be consistent between all options as it is required as the hydraulic break in

the system and to facilitate appropriate control. There may be an argument to have a larger balance

tank for SDI due to the flushing flow requirements where return flows are received at the tank.

Keeping the balance tank size consistent between all options is reasonable at this stage of cost

estimation. Alternatively, the item could be kept as a small balance tank, with increased volume moved

to the risk register on the basis of SDI/CPI control limitations and possible mitigation of the possible

flows from a control valve failure.

2.5 Item 10 – Kepler Site Preparation Costs to manage or work within the peat bog seem excessive. It appears that the best option might be

to avoid it altogether which may require additional pivot infrastructure. This would help minimise what

is a reasonable risk in ongoing wheel track maintenance.

2.6 Item 11 – Centre Pivot Irrigation Cost estimates for centre pivot supply and installation are well understood with hundreds installed

throughout NZ annually.

I note there is no allowance for testing, QA, as-built and commissioning items which are just as

important for CPI as they are for SDI.

2.7 Item 12 – Subsurface Drip Irrigation Balance tank, odour control and pump station items should be reasonably consistent between SDI and

CPI.

The duty/standby requirements should be consistent across the options and between the options. SDC

will have expectations for this and it should be applied to both SDI and CPI equipment/systems where

appropriate.

The soils must be reasonably well understood to have obtained consent for the site and to complete

Hydrus modelling. Is there really a risk of encountering stoney ground during construction that could

affect the dripline installation? This risk item should probably sit outside the main cost schedule as

previously commented.

I am not familiar enough with SDI cost schedules to understand individual item costs, but in principal the

approach to developing the cost estimate should be similar (where possible) to CPI.

Item 12.7 includes items such as safety shower facilities that will be required for both systems. Where

applicable these items should be in Item 10.

Second Item 12.7 and 12.8 need to be applied to the CPI option.

August 2018 14

9.3 Appendix 3 – Ecogent Comments and Peer Review Responses, July 2018

Stantec Note:THESE COMMENTS AND RESPONSES ARE GIVEN AS THE FIRST DOCUMENT IN APPENDIX G OF THE BASIS OF DESIGN REPORT AND ARE NOT REPEATED HERE.

Further Note: The final version of the Peer Reviewer comments were received on 28 August 2018, and these are the ones appended.

Appendix I Cost Estimates

TEANAU SEWERAGE ‐ KEPLER PROPOSAL

Updated Estimate 24 August 2018

Previous Estimate ‐ Refer Business Case Report of Dec 2017 Last Updated 27 July 2018

Updated by Roger Oakley, Alistair McGaughran and Jon Kemp, numerical check by C McCrostie

Reviewed by Roger Oakley and various contributors Opex estimate is updated May 2018

OPTION ONE CONSENTED

OPTION

OPTION 2A CONSENTED

OPTION + BASE FLOW MF + CPI

OPTION 2B CONSENTED

OPTION + PEAK FLOW MF + CPI

OPTION 3A 2,200m3/DAY MF

+ SDI

OPTION 3B 4,500m3/DAY MF

+ SDI

Item Description Unit Quantity Rate Amount Amount Amount Amount Amount 1 PRELIMINARY & GENERAL

1.01 General conventional allowance of 10% (of items 2 - 12) % 10% 1,247,996.01 1,418,381 1,470,881 1,504,472.10 1,539,472.10 1.01 Allowance for head contractor margins % 2% 249,599.20 283,676 294,176 300,894 307,894

Subtotal 1 1,497,595 1,702,057 1,765,057 1,805,367 1,847,367

2 POND RAISING TO PROVIDE ADDITIONAL 15,000m3 STORAGE2.1 Centre Pivot, 30,000m3. Refer estimate from separate spreadsheet. LS 1 980,000.00$ 980,000 980,000 980,000 n/a n/a2.2 Subsurface, 22,000m3. Refer estimate from separate spreadsheet. LS 1 710,000.00$ n/a n/a n/a 710,000 710,000 2.3 Scope Risk Contingency % 5% 980,000.00$ 49,000 49,000 49,000 49,000 49,000

Subtotal 2 1,029,000 1,029,000 1,029,000 759,000 759,000

3 POND PIPEWORK TO ALLOW STORAGE IN POND 13.1 Outlet arrangement from Pond 1 LS 1 20,000.00$ 20,000 20,000 20,000 20,000 20,000 3.2 Actuated valve and flowmeter, via SCADA, to control flow from Pond 1 LS 1 20,000.00$ 20,000 20,000 20,000 20,000 20,000 3.3 Pipework from Pond 1 to 3. (Assume flow goes 1-3-2 and pump from 2). m 150 400.00$ 60,000 60,000 60,000 60,000 60,000 3.4 Level sensors to control all pond levels, and cable through to switchboard LS 1 10,000.00$ 10,000 10,000 10,000 10,000 10,000 3.5 Scope Risk Contingency % 5% 110,000.00$ 5,500 5,500 5,500 5,500 5,500

Subtotal 3 115,500 115,500 115,500 115,500 115,500

4 GENERAL WWTP SITE PROVISIONS

4.1Connection of individual WWTP site elements and data to SCADA/telemetry, incl programming, and supply of telemetry LS 1 40,000.00$ 40,000 40,000 40,000 40,000 40,000

4.2 Power Supply Upgrade to site LS 1 18,000.00$ 18,000 18,000 18,000 18,000 18,000 4.3 Landscaping LS 1 14,000.00$ 14,000 14,000 14,000 14,000 14,000 4.4 Scope Risk Contingency % 5% 72,000.00$ 3,600 3,600 3,600 3,600 3,600

Subtotal 4 75,600 75,600 75,600 75,600 75,600

5A MEMBRANE FILTRATION AT PONDS - BASE FLOW2.2MLD, 1 Rack x 44 modules, expandable to 3,600m3/day, 72 modulesRefer Rising Main PS est for pond intake structure and pipe to inlet screen.

5.01A 500 micron Inlet screen (to protect membrane) and pipe to MF building LS 1 150,000.00$ N/A 150,000 N/A 150,000 N/A5.02A Civil works for inlet screen inlet channel or similar LS 1 50,000.00$ N/A 50,000 N/A 50,000 N/A5.03A Additional algae removal re membrane fouling. BUDGET ALLOWANCE LS 1 200,000.00$ N/A 200,000 N/A 200,000 N/A5.04A Basic building for MF unit, +40m2 spare (excl pipeline PS, see below) m2 125 2,000.00$ N/A 250,000 N/A 250,000 N/A5.05A Chemical CIP and warm water LS 1 37,000.00$ N/A 37,000 N/A 37,000 N/A5.06A Compressed air system LS 1 75,000.00$ N/A 75,000 N/A 75,000 N/A5.07A Instrumentation LS 1 25,000.00$ N/A 25,000 N/A 25,000 N/A5.08A Electrical and controls and standard HMI LS 1 220,000.00$ N/A 220,000 N/A 220,000 N/A5.09A Membrane package incl pumps, valves etc LS 1 340,000.00$ N/A 340,000 N/A 340,000 N/A5.10A Upgrade basic MF package with full SCADA LS 1 20,000.00$ N/A 20,000 N/A 20,000 N/A5.11A Installation and Commissioning LS 1 40,000.00$ N/A 40,000 N/A 40,000 N/A5.12A Civil works to service the site. Eg roads, stormwater, building platform LS 1 50,000.00$ N/A 50,000 N/A 50,000 N/A5.13A Head contractor margin at 12% on MF and Mech/Elec/Commissioning (was $130k) now in P&G N/A N/A N/A N/A N/A5.14A Balance tank, 100m3 working volume, with steel roof LS 1 130,000.00$ N/A 130,000 N/A 130,000 N/A5.15A Pipes after MF plant to PS and rising main, incl civils LS 1 30,000.00$ N/A 30,000 N/A 30,000 N/A5.16A Peak flow bypass to balance tank. Pumps, pipes, valves, control LS 1 70,000.00$ N/A 70,000 N/A 70,000 N/A5.17A 120 micron duty/standby bypass filter/backwash assembly for SDI option. LS 1 100,000.00$ N/A N/A N/A 100,000 N/A5.18A NPV allowance, year 10 membrane upgrade to SDI for flow growth (or $150k now) LS 1 75,000.00$ N/A N/A N/A 75,000 N/A5.19A Backwash pipe to north end of Pond 1. Assume 100mm PE, incl fittings m 250 150.00$ N/A 37,500 N/A 37,500 N/A5.20A Scope Risk Contingency % 5% -$ N/A 84,350 N/A 84,350 N/A

Subtotal 5 - 1,808,850 - 1,983,850 -

5B MEMBRANE FILTRATION AT PONDS - PEAK FLOW 4.5MLD 2 racks of x44 modules, expandable to 72 modules/rack

Refer Rising Main PS est for pond intake structure and pipe to inlet screen.5.01B 500 micron Inlet screen (to protect membrane) and pipe to MF building LS 1 180,000.00$ N/A N/A 180,000 N/A 180,000 5.02B Civil works for inlet screen inlet channel or similar LS 1 60,000.00$ N/A N/A 60,000 N/A 60,000 5.03B Additional algae removal re membrane fouling. BUDGET ALLOWANCE LS 1 200,000.00$ N/A N/A 200,000 N/A 200,000 5.04B Basic building for MF unit ( +40m2 spare excl pipeline PS, see below) m2 190 2,000.00$ N/A N/A 380,000 N/A 380,000 5.05B Chemical CIP and warm water LS 1 52,000.00$ N/A N/A 52,000 N/A 52,000 5.06B Compressed air system LS 1 75,000.00$ N/A N/A 75,000 N/A 75,000 5.07B Instrumentation LS 1 40,000.00$ N/A N/A 40,000 N/A 40,000 5.08B Electrical and controls and standard HMI LS 1 300,000.00$ N/A N/A 300,000 N/A 300,000 5.09B Membrane package incl pumps, valves etc LS 1 600,000.00$ N/A N/A 600,000 N/A 600,000 5.10B Upgrade basic MF package with full SCADA LS 1 20,000.00$ N/A N/A 20,000 N/A 20,000 5.11B Installation and Commissioning LS 1 60,000.00$ N/A N/A 60,000 N/A 60,000 5.12B Civil works to service the site. Eg roads, stormwater, building platform LS 1 60,000.00$ N/A N/A 60,000 N/A 60,000 5.13B Head contractor margin at 12% on MF and Mech/Elec/Commissioning (was $130k) now in P&G N/A N/A N/A N/A N/A5.14B Balance tank, 100m3 working volume, with steel roof LS 1 130,000.00$ N/A N/A 130,000 N/A 130,000 5.15B Pipes after MF plant to PS and rising main, incl civils LS 1 30,000.00$ N/A N/A 30,000 N/A 30,000 5.16B Backwash pipe to north end of Pond 1. Assume 100mm PE, incl fittings etc m 250 150.00$ N/A N/A 37,500 N/A 37,500 5.17B Scope Risk Contingency % 5% -$ N/A N/A 109,350 N/A 109,350

Subtotal 5 - - 2,333,850 2,333,850

6 RISING MAIN PUMP STATION6.01 Pond intake structure LS 1 30,000.00$ 30,000 30,000 30,000 30,000 30,000 6.02 Upgraded screening for option 1 to protect pump LS 1 30,000.00$ 30,000 N/A N/A N/A N/A6.04 Inlet pipe to pumpstation LS 1 15,000.00$ 15,000 15,000 15,000 15,000 15,000

6.05A PS building, slab 2m below ground level, basement walls extending above flood level m2 50 3,500.00$ 175,000 N/A N/A N/A N/A6.05B PS building if membranes used, assume as extra area in membrane building m2 50 2,000.00$ N/A 100,000 100,000 100,000 100,000 6.06 PS mech, elec fitout, and dry mount pumps LS 1 240,000.00$ 240,000 240,000 240,000 240,000 240,000 6.07 MEICA within pumpstation. LS 1 80,000.00$ 80,000 80,000 80,000 80,000 80,000 6.08 Surge Control Vessels and controls LS 1 80,000.00$ 80,000 80,000 80,000 80,000 80,000 6.09 General Site Works LS 1 30,000.00$ 30,000 30,000 30,000 30,000 30,000 6.12 Back up generator LS 1 56,000.00$ excluded excluded excluded excluded excluded6.13 Scope Risk Contingency % 5% 680,000.00$ 34,000 34,000 34,000 34,000 34,000

Subtotal 6 714,000 609,000 609,000 609,000 609,000

1:14 p.m.24/08/2018 P:\_2012 Onwards\Southland District Council\80508264 Te Anau WWTP\F ‐ Design\F3 ‐ Calculations and $ ests\cost Estimates\Estimates Sept 17 onwards\App 5 Cost Est_Te Anau Opex and Capex July 2018 v19App 5 Cost Est_Te Anau Opex and Capex July 2018 v19 1 of 5


OPTION

OPTION 2A CONSENTED


OPTION 2B CONSENTED



+ SDI


+ SDI

Item Description Unit Quantity Rate Amount Amount Amount Amount Amount 7 CONSTRUCTION OF RISING MAIN - BASED ON 250ID PN100 PE PIPE

7.1 Transfer Pipe 7.1.1 Pipe supply only, delivered to site

7.1.1.1 PE315 PN16 PE100 m 4000 146.00$ 584,000 584,000 584,000 584,000 584,000 7.1.1.2 PE280 PN12.5 PE100 m 3000 93.00$ 279,000 279,000 279,000 279,000 279,000 7.1.1.3 PE280 PN10 PE100 m 11500 79.00$ 908,500 908,500 908,500 908,500 908,500 7.1.2 Pipe trench excavation, shoring, jointing/lay, bedding, backfilling and reinstatement

7.1.2.1 Road Carriageway Crossing 1- SH94 Te Anau Milford Hwy m 30 781.00$ 23,430 23,430 23,430 23,430 23,430

7.1.2.2 Road Carriageway Crossing 2 - Sandy Brown Rd near SH94 m 35 781.00$ 27,335 27,335 27,335 27,335 27,335 7.1.2.3 Road Carriageway Crossing 3 - Captain Roberts Rd and Sandy Brown Rd m 35 781.00$ 27,335 27,335 27,335 27,335 27,335 7.1.2.4 Road Carriageway Crossing 4 - Caswell Rd and Sandy Brown Rd m 35 781.00$ 27,335 27,335 27,335 27,335 27,335 7.1.2.5 Road Carriageway Crossing 5 - Burnby Dr and Sandy Brown Rd m 35 781.00$ 27,335 27,335 27,335 27,335 27,335 7.1.2.6 Road Carriageway Crossing 6 - SH94 Te Anau Mossburn Hwy m 35 781.00$ 27,335 27,335 27,335 27,335 27,335 7.1.2.7 Road Carriageway Crossing 7 - Mt York Rd and SH95 Manapouri Te Anau Hwy m 35 781.00$ 27,335 27,335 27,335 27,335 27,335 7.1.2.8 In road verge/berm - Depth 1m to 1.3m m 855 201.30$ 172,112 172,112 172,112 172,112 172,112 7.1.2.9 In road verge/berm - Depth 1.3m to 1.5m m 6090 206.80$ 1,259,412 1,259,412 1,259,412 1,259,412 1,259,412 7.1.2.10 In road verge/berm - Depth 1.5m to 1.8m m 2310 222.20$ 513,282 513,282 513,282 513,282 513,282 7.1.2.11 In road verge/berm - Depth 1.8m to 2 .1m m 295 242.00$ 71,390 71,390 71,390 71,390 71,390 7.1.2.12 In road verge/berm - Depth 2.1m to 2 .5m m 10 302.50$ 3,025 3,025 3,025 3,025 3,025 7.1.2.13 In paddock - Depth 1m to 1.3m m 3605 93.00$ 335,265 335,265 335,265 335,265 335,265 7.1.2.14 In paddock - Depth 1.3m to 1.5m m 2320 98.00$ 227,360 227,360 227,360 227,360 227,360 7.1.2.15 In paddock - Depth 1.5m to 1.8m m 2070 105.00$ 217,350 217,350 217,350 217,350 217,350 7.1.2.16 In paddock - Depth 1.8m to 2 .1m m 550 130.00$ 71,500 71,500 71,500 71,500 71,500 7.1.2.17 In paddock - Depth 2.1m to 2 .5m m 70 140.00$ 9,800 9,800 9,800 9,800 9,800 7.1.2.18 In paddock - Depth over 2 .5m m 85 150.00$ 12,750 12,750 12,750 12,750 12,750 7.1.2.19 Extra over for excavation in hard ground or boulders - PROVISIONAL m 1850 60.00$ 111,000 111,000 111,000 111,000 111,000 7.1.2.20 Extra over for overcutting on carriageway seal and reinstatement - PROVISIONAL m 200 80.00$ 16,000 16,000 16,000 16,000 16,000

7.1.3 Pipe Ancillaries 7.1.3.1 DN 300 horizontal 11.25 bend No 15 2,020.00$ 30,300 30,300 30,300 30,300 30,300 7.1.3.2 DN 300 horizontal 22.5 bend No 15 2,028.00$ 30,420 30,420 30,420 30,420 30,420 7.1.3.3 DN 300 horizontal 45 bend No 15 2,073.00$ 31,095 31,095 31,095 31,095 31,095 7.1.3.4 Sluice Valves (in line) No 20 3,700.00$ 74,000 74,000 74,000 74,000 74,000 7.1.3.5 Spindle extension for sluice valve - Provisional No 20 650.00$ 13,000 13,000 13,000 13,000 13,000 7.1.4 Stream crossings and Culvert crossings

7.1.4.1 Stormwater Culvert Crossing. Allowance to deviate under a culvert. No 14 1,300.00$ 18,200 18,200 18,200 18,200 18,200 7.1.4.2 Stream Crossing 5 - Ramparts Creek Bridge Crossings No 1 30,000.00$ 30,000 30,000 30,000 30,000 30,000 7.1.4.3 Stream Crossing 8 No 1 60,000.00$ 60,000 60,000 60,000 60,000 60,000 7.1.4.4 Stream Crossing 9 No 1 60,000.00$ 60,000 60,000 60,000 60,000 60,000 7.1.4.5 Allowance for supporting side of trench at two crossings No 2 5,000.00$ 10,000 10,000 10,000 10,000 10,000 7.1.4.6 Allowance for reparing damaged culvert - PROVISIONAL No 7 2,000.00$ 14,000 14,000 14,000 14,000 14,000 7.1.5 Additonal Items

7.1.5.1 Reinstatement of paddocks LS 1 4,000.00$ 4,000 4,000 4,000 4,000 4,000 7.1.5.2 Fence and gate reinstatement - Landcorp land LS 1 5,000.00$ 5,000 5,000 5,000 5,000 5,000 7.1.5.3 Supporting and relaying existing 63OD watermain along Upukerora Road m 700 50.00$ 35,000 35,000 35,000 35,000 35,000 7.1.5.4 Supply, lay firbre optic conduit along pipeline. Including offtakes to air valve boxes m 18500 8.00$ 148,000 148,000 148,000 148,000 148,000 7.1.5.5 Installation and commissioning fibre optic cable in sections No 11 200.00$ 2,200 2,200 2,200 2,200 2,200 7.1.6 Testing and Compliance

7.1.6.1 Compaction testing or trench floor and backfill material LS 1 11,600.00$ 11,600 11,600 11,600 11,600 11,600 7.1.6.2 Hydrostatic pressure testing of DN300 reticulation main in sections LS 19 4,500.00$ 85,500 85,500 85,500 85,500 85,500 7.1.6.3 Commissioning of pipeline LS 1 6,500.00$ 6,500 6,500 6,500 6,500 6,500

7.2 Air Valve and Odour Treatment7.2.1 Air valve and chamber ea 32 5,500.00$ 176,000 176,000 176,000 176,000 176,000 7.2.2 Carbon filters added to airvalves ea 32 8,000.00$ 256,000 256,000 256,000 256,000 256,000 7.2.3 Branches to air valve chambers at line valves ea 32 6,500.00$ 208,000 208,000 208,000 208,000 208,000 7.2.4 Vehicle Access to Air valve and Odour treatment No 16 6,000.00$ 96,000 96,000 96,000 96,000 96,000

7.3 Pump Out Drain Points7.3.1 Pump Out chamber including upstand pipe and fittings ea 18 6,500.00$ 117,000 117,000 117,000 117,000 117,000 7.3.2 Branches to pump-out chambers at line valves, including PE "special" offtake fitting ea 10 6,500.00$ 65,000 65,000 65,000 65,000 65,000 7.3.3 Vehicle Access to Pump Out drain points No 5 6,000.00$ 30,000 30,000 30,000 30,000 30,000

7.4 Control Valve (Kepler Site)7.4.1 Allowance for flow control at Kepler to keep rising main full during on/off LS 1 30,000.00$ 30,000 30,000 30,000 30,000 30,000

7.5 Pipework Contingency to allow for Work not yet identified7.5.1 Scope Risk Contingency % 5% 6,626,000.50$ 331,300 331,300 331,300 331,300 331,300

Subtotal 7 6,957,301 6,957,301 6,957,301 6,957,301 6,957,301

8 KEPLER ELECTRICAL SUPPLY AND MONITORING8.1 Power supply to site LS 1 70,000.00$ 70,000 70,000 70,000 70,000 70,000 8.2 Switchboard building m2 25 2,000.00$ 50,000 50,000 50,000 50,000 50,000 8.3 Switchboard. LS 1 50,000.00$ 50,000 50,000 50,000 40,000 40,000 8.4 PLC and SCADA programming - entire Kepler Site LS 1 40,000.00$ 40,000 40,000 40,000 40,000 40,000 8.5 EMP monitoring soil (6), 1 climate station, runoff detection(2) LS 1 32,000.00$ 32,000 32,000 32,000 32,000 32,000 8.6 Scope Risk Contingency % 5% 242,000.00$ 12,100 12,100 12,100 12,100 12,100

Subtotal 8 254,100 254,100 254,100 244,100 244,100

9 ODOUR CONTROL - Trickling filter, biofilter and chem dosing.9.1 Trickling Filter (13m dia, 4m media depth 6m wall height)

9.1.1 Earthworks, foundations and reinstatement m3 100 50.00$ 5,000.00$ 5,000 5,000 NA NA9.1.2 Pipework under the tank and valves/bends/flanges etc LS 1 20,000.00$ 20,000.00$ 20,000 20,000 NA NA9.1.3 Site concrete under floor m2 140 35.00$ 4,900.00$ 4,900 4,900 NA NA9.1.4 Tank floor - concrete 175mm thick, shaped m3 23 2,000.00$ 46,000.00$ 46,000 46,000 NA NA9.1.5 Tank floor - concrete ring beam 125mm extra, and discharge channel m3 6 2,000.00$ 12,000.00$ 12,000 12,000 NA NA9.1.6 Tank floor - sealants m 60 60.00$ 3,600.00$ 3,600 3,600 NA NA9.1.7 Central column - steel with flanges and conc lined LS 1 15,000.00$ 15,000.00$ 15,000 15,000 NA NA9.1.8 Central column - concrete surround and foundation m3 6 2,000.00$ 12,000.00$ 12,000 12,000 NA NA9.1.9 Distributor arm assembly m 12.5 12,000.00$ 150,000.00$ 150,000 150,000 NA NA

9.1.10 Distributor arm delivery to site from UK LS 1 50,000.00$ 50,000.00$ 50,000 50,000 NA NA9.1.11 Air pipework within tank m 30 300.00$ 9,000.00$ 9,000 9,000 NA NA9.1.12 Plenum floor m2 130 80.00$ 10,400.00$ 10,400 10,400 NA NA9.1.13 Plastic media from DCC, 240m3 LS 1 16,000.00$ 16,000.00$ 16,000 16,000 NA NA9.1.14 Plastic media, 260m3 m3 260 325.00$ 84,500.00$ 84,500 84,500 NA NA9.1.15 Media repackaging, loading and unloading hr 180 30.00$ 5,400.00$ 5,400 5,400 NA NA9.1.16 Media cartage only - free from DCC. 60m3 per trip trip 7 2,800.00$ 19,600.00$ 19,600 19,600 NA NA9.1.17 Media loading into TF (500m3, 23t) m3 500 20.00$ 10,000.00$ 10,000 10,000 NA NA9.1.18 Tank structure and roof - glass coated steel, 13m diameter by 6m high. LS 1 250,000.00$ 250,000.00$ 250,000 250,000 NA NA9.1.19 Tank modifications from standard (eg flush vents, air outlets, lights) LS 1 10,000.00$ 10,000.00$ 10,000 10,000 NA NA9.1.20 Internal walkway m 13 2,000.00$ 26,000.00$ 26,000 26,000 NA NA9.1.21 Hopper LS 1 10,000.00$ 10,000.00$ 10,000 10,000 NA NA9.1.22 Fans on plinths feeding air to plenum at base Nr 2 15,000.00$ 30,000.00$ 30,000 30,000 NA NA9.1.23 Electrical and Control incl SCADA connection from main switchboard LS 1 15,000.00$ 15,000.00$ 15,000 15,000 NA NA



OPTION

OPTION 2A CONSENTED


OPTION 2B CONSENTED



+ SDI


+ SDI

Item Description Unit Quantity Rate Amount Amount Amount Amount Amount 9.2 AIR SYSTEMS AND SOIL FILTER (2,300m3/hr, 30m2)

Assume an above ground soil filter 1.5m deep and 6m x 5m9.2.2 Foundations, strip topsoil etc LS 1 2,000.00$ 2,000.00$ 2,000 2,000 NA NA9.2.3 Site concrete under filter m2 30 35.00$ 1,050.00$ 1,050 1,050 NA NA9.2.4 Assume timber walls m2 40 200.00$ 8,000.00$ 8,000 8,000 NA NA9.2.5 Wall/floor lining and gravity drain to pump chamber LS 1 5,000.00$ 5,000.00$ 5,000 5,000 NA NA9.2.6 Above ground pipework from TF, say 400mm diameter m 30 500.00$ 15,000.00$ 15,000 15,000 NA NA9.2.7 Plenum chamber media and separation barrier to media m3 26 150.00$ 3,900.00$ 3,900 3,900 NA NA9.2.8 Plenum distribution pipework LS 1 10,000.00$ 10,000.00$ 10,000 10,000 NA NA9.2.9 Supply and install filter media m3 26 60.00$ 1,560.00$ 1,560 1,560 NA NA

9.2.10 Media irrigation system LS 1 3,000.00$ 3,000.00$ 3,000 3,000 NA NA9.2.11 Fans Nr 2 10,000.00$ 20,000.00$ 20,000 20,000 NA NA9.2.12 Electrical and Control incl SCADA connection from main switchboard LS 1 15,000.00$ 15,000.00$ 15,000 15,000 NA NA9.2.13 Smoke testing and commissioning LS 1 2,000.00$ 2,000.00$ 2,000 2,000 NA NA

9.3 RECIRCULATION PUMPSTATIONAssume 3 chamber. Internal 3.3m deep x 3m x8.1m. 4.5MLD design flow.

9.3.1 Excavation m3 540 12.00$ 6,480.00$ 6,480 6,480 NA NA9.3.2 Site concrete m2 44 35.00$ 1,540.00$ 1,540 1,540 NA NA9.3.3 Backfill and compaction with excavated material m3 440 20.00$ 8,800.00$ 8,800 8,800 NA NA9.3.4 Concrete structure (250mm walls - lined so not water retaining concrete design) m3 24 2,700.00$ 64,800.00$ 64,800 64,800 NA NA9.3.5 Internal weir, penstock and flap valve LS 1 12,000.00$ 12,000.00$ 12,000 12,000 NA NA9.3.6 PVC lining floors and walls m2 79 370.00$ 29,230.00$ 29,230 29,230 NA NA9.3.7 Top slab 200mm thick - precast m3 6 2,000.00$ 12,000.00$ 12,000 12,000 NA NA9.3.8 Aluminium lids - non trafficable LS 1 6,000.00$ 6,000.00$ 6,000 6,000 NA NA9.3.9 Internal pipework and (above ground) valve 'chamber' LS 1 60,000.00$ 60,000.00$ 60,000 60,000 NA NA

9.3.10 Pipework to and from TF, say 30m steel at 300dia with bends etc m 30 600.00$ 18,000.00$ 18,000 18,000 NA NA9.3.11 Pipework branch to and from Te Anau to CP irrigators, incl valves, to PS's LS 1 12,000.00$ 12,000.00$ 12,000 12,000 NA NA9.3.12 Recirc pumps, constant recirc rate = 52 l/s. Duty/standby Nr 2 12,000.00$ 24,000.00$ 24,000 24,000 NA NA9.3.13 Irrigation pumps, installed, 26 -52 L/s Nr 3 23,000.00$ 69,000.00$ 69,000 69,000 NA NA9.3.14 Electrical and Control incl SCADA connection from main switchboard LS 1 15,000.00$ 15,000.00$ 15,000 15,000 NA NA

9.3.15Increase storage in pumpwell from 30 to 100m3 to provide direct comparison with SDIbalance tank. Refer SDI Basis of Design report. LS 1 100,000.00$ 100,000.00$ 100,000 100,000 NA NA

9.4 Oxidant Dosing (for final odour removal)9.4.1 Lump sum allowance (Refer to Sydney Water standard design) LS 1 200,000.00$ 200,000.00$ 200,000 200,000 NA NA

9.5 Misc Trickling Filter works9.5.1 Tracks/hardstanding around Trickling Filter and pumpstations LS 1 4,000.00$ 4,000.00$ 4,000 4,000 NA NA9.5.2 Fencing - low m 100 20.00$ 2,000.00$ 2,000 2,000 NA NA9.5.3 Landscaping LS 1 2,000.00$ 2,000.00$ 2,000 2,000 NA NA9.5.4 Upgrade of power supply to site from what is needed for CPs LS 1 5,000.00$ 5,000.00$ 5,000 5,000 NA NA9.5.5 Spray drift sensors (detect horiz drift, sheltered from the rain). ea 4 7,000.00$ 28,000.00$ 28,000 28,000 NA NA9.5.6 Safety shower, with gravity warm water supply LS 1 6,000.00$ 6,000.00$ 6,000 6,000 NA NA

9.6 Trickling Filter and Irrigation Infrastructure Commissioning9.6.1 Contractor attendance Hr 150 90.00$ 13,500.00$ 13,500 13,500 NA NA9.6.2 Extra capital items LS 1 20,000.00$ 20,000.00$ 20,000 20,000 NA NA9.6.3 O&M manuals, as-builts LS 1 8,000.00$ 8,000.00$ 8,000 8,000 NA NA9.6.4 Disbursements LS 1 4,000.00$ 4,000.00$ 4,000 4,000 NA NA

9.7 Scope Risk Contingency % 5% 1,632,260.00$ 81,613 81,613 81,613 NA NA

Subtotal 9 1,713,873 1,713,873 1,713,873 - -

10 KEPLER SITE PREPARATIONPaddock and Pasture Development

10.01 Paddock Development, change grass/crop Ha 120 500.00$ 60,000 60,000 60,000 60,000 60,000 10.02 CPI. Allowance for basic contouring. Separate storm runoff from irrigated areas. LS 1 125,000.00$ 125,000 125,000 125,000 NA NA10.03 SDI. Allowance for basic contouring. Separate storm runoff from irrigated areas. LS 1 75,000.00$ N/A N/A N/A 75,000 75,000

Shelter Belts10.04 Remove northern shelter belt, incl stumps m 1500 86.00$ 129,000 129,000 129,000 129,000 129,000 10.05 Remove Southern Shelter belt, incl stumps. SDI only m 1300 62.00$ N/A N/A N/A 80,600 80,600 10.06 Remove end of southwestern shelter belt (by runway) LS 1 34,000.00$ 34,000 34,000 34,000 34,000 34,000 10.07 Transport of saleable firewood off site - northern shelter belt LS 1 23,000.00$ 23,000 23,000 23,000 23,000 23,000 10.08 Transport of saleable firewood off site - southern shelter belt LS 1 20,000.00$ N/A N/A N/A 20,000 20,000 10.09 Burn and bury non-saleable wood, tree stumps, smooth ground - north shelter belt LS 1 19,000.00$ 19,000 19,000 19,000 19,000 19,000 10.10 Burn and bury non-saleable wood, tree stumps, smooth ground - south shelter belt LS 1 14,500.00$ N/A N/A N/A 14,500 14,500 10.11 Trim /clear existing western shetter belt for new boundary fence m 400 6.00$ 2,400 2,400 2,400 2,400 2,400 10.12 Clear existing slash and trees to enable new accessway LS 1 7,000.00$ 7,000 7,000 7,000 7,000 7,000 10.13 Plant new northern shelter belt & maintain 1yr (consent and Landcorp rqd) m 1500 0.60$ 900 900 900 900 900 10.14 Plant new western shelterbelt m 400 0.60$ 240 240 240 240 240 10.15 Plant one extra row on eastern shelterbelt m 650 0.60$ 390 390 390 390 390

Fences10.16 Remove internal fences LS 1 20,000.00$ 20,000 20,000 20,000 20,000 20,000 10.17 Fencing for one side of northern, eastern and western shelter belts m 2600 15.00$ 39,000 39,000 39,000 39,000 39,000 10.18 Fencing for one side of SH95 access track m 400 15.00$ 6,000 6,000 6,000 6,000 6,000 10.19 Reinstate Landcorp fences/gates at new boundary fences. LS 1 10,000.00$ 10,000 10,000 10,000 10,000 10,000 10.20 Fencing of Landcorp's new southern landway. (SDC not yet agreed to this) m 900 15.00$ 13,500 13,500 13,500 13,500 13,500

Miscellaneous10.21 Peat Bog development, planting, earthworks Nr 1 10,000.00$ 10,000 10,000 10,000 N/A N/A10.22 Isolate water supply LS 1 1,000.00$ 1,000 1,000 1,000 1,000 1,000 10.23 Form access track from SH95 LS 1 6,000.00$ 6,000 6,000 6,000 6,000 6,000 10.24 Laneways across access track LS 1 2,000.00$ 2,000 2,000 2,000 2,000 2,000 10.25 Diagram C entrance off SH95 (if required) LS 1 9,000.00$ 9,000 9,000 9,000 9,000 9,000 10.26 More bores etc for ongoing monitoring Nr 6 5,000.00$ 30,000 30,000 30,000 30,000 30,000 10.27 Site signage as required by consent conditions LS 1 8,000.00$ 8,000 8,000 8,000 8,000 8,000 10.28 Scope Risk Contingency % 10% 555,430.00$ 55,543 55,543 55,543 55,543 55,543

Subtotal 10 610,973 610,973 610,973 666,073 666,073

11 CENTRE PIVOT IRRIGATION11.1 Supply and install CPs, incl frieght to site (WaterForce Sept 2017) m 766 390.00$ 298,740 298,740 298,740 N/A N/A11.2 Allowance for effluent vs water - screening and corrosion Nr 3 20,000.00$ 60,000 60,000 60,000 N/A N/A11.3 Water supply and storage for flushing the CPs, and pumpset in shed Nr 1 25,000.00$ 25,000 25,000 25,000 N/A N/A11.4 Upgrade CPs to vary flow rate by isolating nozzles Nr 3 50,000.00$ 150,000 150,000 150,000 N/A N/A11.5 Upgrade CPs for boon backs for outer spans Nr 3 11,000.00$ 33,000 33,000 33,000 N/A N/A11.6 Power supply to irrigators - based on share trench with pipeline (km) m 1680 50.00$ 84,000 84,000 84,000 N/A N/A11.7 Tracks for Pivot drive wheels - allowance m 17000 2.00$ 34,000 34,000 34,000 N/A N/A11.8 Peat Bog wheel bridges, or additional CP to avoid bog (revised May 2018) m 200 500.00$ 100,000 100,000 100,000 N/A N/A11.9 300mm Pipeline from boundary to CP 1/2 m 900 170.00$ 153,000 153,000 153,000 N/A N/A11.10 200mm Pipeline from CP2 to CP 3/4 m 780 160.00$ 124,800 124,800 124,800 N/A N/A11.11 Fibre optic cable to irrigators m 1680 8.00$ 13,440 13,440 13,440 N/A N/A

11.12Deduction (for fair SDI comparison). Assume 20% CPI delayed to year 10. (6% discountrate, 10 yr = 0.5584 on 20% of CPI cost) LS 215,196 0.5584-$ 120,165- 120,165- 120,165- N/A N/A

11.13 Scope Risk Contingency % 5% 1,075,980.00$ 53,799 53,799 53,799 N/A N/A

Subtotal 11 1,009,614 1,009,614 1,009,614 - -



OPTION

OPTION 2A CONSENTED


OPTION 2B CONSENTED



+ SDI


+ SDI

Item Description Unit Quantity Rate Amount Amount Amount Amount Amount 12 SUBSURFACE DRIP IRRIGATION

12.1 Kepler Balance Tank5m dia tank. 2hr peak capacity = 100m3. Glass coated steel sides and roof LS 1 130,000.00$ N/A N/A N/A 130,000 130,000 Pump outlet pipework inside tank, including plinths. LS 1 5,000.00$ N/A N/A N/A 5,000 5,000

12.2 Kepler Balance Tank Odour ControlOdour control on tank. Assume soil filter, ductwork and fan. Or carbon filter LS 1 40,000.00$ N/A N/A N/A 40,000 40,000

12.2 PumpingPump shed. Basic lighting, ventilation. m2 50 2,000.00$ N/A N/A N/A 100,000 100,000 Pipework (250id) and valves from balance tank, through pumpset, filters assembly, flowmeter, then underground. Stainless. LS 1 30,000.00$ N/A N/A N/A 30,000 30,000 Pumpset for SDI system. Duty/standby 58L/s. All manifolding, valves, elec. LS 2 50,000.00$ N/A N/A N/A 100,000 100,000 Flowmeter, above ground. LS 1 10,000.00$ N/A N/A N/A 10,000 10,000 Misc controls and instrumentation (excl SCADA - priced elsewhere) LS 1 2,000.00$ N/A N/A N/A 2,000 2,000

12.3 Irrigation FiltersBulk Main filters. 100micron 58 L/s. Incl stainless pipes, valves, plinth. ea 2 75,000.00$ N/A N/A N/A 150,000 150,000 Flushing Main filter. 100 micron. 3.5 L/s backwash rate LS 1 15,000.00$ N/A N/A N/A 15,000 15,000 PE Holding tank 30m3 to accept backwash from filters. Above ground. LS 1 20,000.00$ N/A N/A N/A 20,000 20,000 Settling tank for flush water before pumping/decanting to balance tank. LS 1 20,000.00$ N/A N/A N/A 20,000 20,000 Pumpset 1 L/s, elec/controls for decanted settling tank water to balance tank LS 1 5,000.00$ N/A N/A N/A 5,000 5,000

12.4 Biofilm Chemical DosingDosing equipment and shed. Keep separate from electrics. As per CPI ox dosing LS 1 200,000.00$ N/A N/A N/A 200,000 200,000

12.5 Subsurface Drip Irrigation - Stage One12.5.1 Mainline Trunk Pipework Stage One

Site Boundary to arrival balance tank. PN10 250id PE assumed. 700 cover m 350 160.00$ N/A N/A N/A 56,000 56,000 Central main down spine of zones. PN10 250id (315OD) PE 900 cover m 700 170.00$ N/A N/A N/A 119,000 119,000

12.5.2 Zone Sub-mains Stage OnePE tee connection from mainline to adjacent pair of flush zones ea 12 1,200.00$ N/A N/A N/A 14,400 14,400 Zone inlet valves, 100mm plus butterfly, install, incl automation, SCADA ea 24 3,500.00$ N/A N/A N/A 84,000 84,000 Zone inlet manifold 80mm PVC, reduce to 50mm at ends. 55m long ea 24 1,500.00$ N/A N/A N/A 36,000 36,000 Install above manifolds (excl lateral risers) ea 24 1,500.00$ N/A N/A N/A 36,000 36,000 Inlet manifold flush points at each end of manifold 50mm valve in 600 dia chamber, with hat ea 26 3,500.00$ N/A N/A N/A 91,000 91,000 Inlet manifold flush return line flush tank, 3.5L/s. 90mm MDPE. Plus valves m 700 100.00$ N/A N/A N/A 70,000 70,000 Chambers for all zone inlet and inlet and outlet valve assemblies. Above ground, Rain hat galv lid Nr 24 3,500.00$ N/A N/A N/A 84,000 84,000

12.5.3 Dripper Lines - (Stage one 45Ha)12.5.3.1 Supply 20 mm driplines (200m long runs, 1.0m dripper spacing). 1.25mm WT. m 270,000 1.25$ N/A N/A N/A 337,500 337,500 12.5.3.2 Supply 16 mm driplines (130m long runs, 1.0m dripper spacing). 1.15mm WT. m 180,000 1.06$ N/A N/A N/A 190,800 190,800 12.5.3.3 Installation of driplines (Moled in using tractor). See separate estimate m 450,000 0.55$ N/A N/A N/A 247,500 247,500 12.5.3.4 Import moleplough machine from elsewhere (eg Australia) LS 1 30,000.00$ N/A N/A N/A 30,000 30,000 12.5.3.5 Transport dripline to site. 0.4m3/roll, 150 rolls/ truck. INCLUDED IN SUPPLY loads 9 -$ N/A N/A N/A - - 12.5.3.6 Supply materials for dripline connection to manifolds each 1,320 20.00$ N/A N/A N/A 26,400 26,400 12.5.3.7 Install dripline connection to manifolds each 1,320 5.00$ N/A N/A N/A 6,600 6,600

riskBudget risk allowance for stoney ground remediation around driplines. Weighted price at 20% of full cost. LS 20% 450,000.00$ N/A N/A N/A 90,000 90,000

12.5.4 SDI Field Electrical Power supply in conduit to all inlet chambers. 230V. Incl connections m 700 50.00$ N/A N/A N/A 35,000 35,000 Conduit connecting all inlet chambers to Pumps. Controls and sensors m 700 15.00$ N/A N/A N/A 10,500 10,500 Scada units. Each serves 6 inlet valves ea 4 5,000.00$ N/A N/A N/A 20,000 20,000 Heat trace on inlet valves - frost protection ea 24 200.00$ N/A N/A N/A 4,800 4,800 9 core cables connecting local chambers to SCADA units m 700 12.00$ N/A N/A N/A 8,400 8,400 Fibre optic comms cable down spine m 700 8.00$ N/A N/A N/A 5,600 5,600 Allowance for connections of various cables LS 1 12,000.00$ N/A N/A N/A 12,000 12,000

12.6 Flush Submains - Stage OneZone outlet manifold 50mm PE. (potential to reduce at ends). 55m long ea 24 2,000.00$ N/A N/A N/A 48,000 48,000 Supply materials for dripline connection to manifolds ea 1,320 20.00$ N/A N/A N/A 26,400 26,400 Install dripline connection to manifolds ea 1,320 5.00$ N/A N/A N/A 6,600 6,600 Air/vacuum valves in chamber at high point of manifold with odour filter ea 24 8,000.00$ N/A N/A N/A 192,000 192,000 Zone outlet valves package (50mm butterfly isolating, flush valve, pressure gauge). Inclautomation, SCADA. In chamber with hat ea 24 3,500.00$ N/A N/A N/A 84,000 84,000 Flush submains. PN9 80mm PE assumed. m 2100 100.00$ N/A N/A N/A 210,000 210,000 Fresh water feed to outlet manifolds (submain) to control valves. m 2100 10.00$ N/A N/A N/A 21,000 21,000 Freshwater pumpset and tank LS 1 15,000.00$ N/A N/A N/A 15,000 15,000 Flowmeter kit,connected to SCADA, to monitor flushing effectiveness ea 1 6,000.00$ N/A N/A N/A 6,000 6,000

12.7 Stage Two SDI 10 Hectares.Based on per Ha rate for Stage One (items 12.5, 12.6) 49,433.33$ Additional 10 Ha in year 10 at 6% NPV discount rate (0.5584) Ha 10 27,603.57$ N/A N/A N/A 276,036 276,036

12.8 MiscellaneousFurther smoothing of paddock (can't do it later once driplines in). LS 1 30,000.00$ N/A N/A N/A 30,000 30,000 Water supply from farm system LS 1 4,000.00$ N/A N/A N/A 4,000 4,000 Safety shower, with gravity warm water supply LS 1 6,000.00$ N/A N/A N/A 6,000 6,000 Tracks/hardstanding around SDI facilities LS 1 4,000.00$ N/A N/A N/A 4,000 4,000 Fencing - low m 100 20.00$ N/A N/A N/A 2,000 2,000 Landscaping LS 1 2,000.00$ N/A N/A N/A 2,000 2,000

12.9 Testing and QA - PipelinesBalance tank, pumpset, filter area pressure/leak tests LS 1 3,000.00$ N/A N/A N/A 3,000 3,000 Inlet main per test 2 1,600.00$ N/A N/A N/A 3,200 3,200 Dripper flow tests - random test, once per zone per test 24 800.00$ N/A N/A N/A 19,200 19,200 Outlet flush mains per test 3 1,600.00$ N/A N/A N/A 4,800 4,800 Destruction testing of samples LS 1 10,000.00$ N/A N/A N/A 10,000 10,000

12.10 COMMISSIONINGContractor attendance Hr 150 90.00$ N/A N/A N/A 13,500 13,500 Extra capital items LS 1 20,000.00$ N/A N/A N/A 20,000 20,000 O and M manuals and as-builts LS 1 8,000.00$ N/A N/A N/A 8,000 8,000 Disbursements LS 1 4,000.00$ N/A N/A N/A 4,000 4,000

12.11 Scope Risk Contingency % 5% 3,461,235.73$ N/A N/A N/A 173,062 173,062

Subtotal 12 - - - 3,634,298 3,634,298



OPTION

OPTION 2A CONSENTED


OPTION 2B CONSENTED



+ SDI


+ SDI

Item Description Unit Quantity Rate Amount Amount Amount Amount Amount SUBTOTAL 1- 12 13,977,555 15,885,867 16,473,867 16,850,088 17,242,088

13 ALLOWANCES 14.1 Construction Contingency (post Contract award) % 10% 1,397,756 1,588,587 1,647,387 1,685,009 1,724,209 14.2 Market Risk - competiveness/volatility % TBC TBC TBC TBC TBC TBC14.3 Unknown items - identified per category, see above N/A N/A N/A N/A N/A N/A N/A N/A14.4 Remote location - relocate workforce % TBC TBC TBC TBC TBC TBC

Subtotal 13 1,397,756 1,588,587 1,647,387 1,685,009 1,724,209

TOTAL ESTIMATED CONSTRUCTION CONTRACT VALUE TOTAL 1-13 15,375,311 17,474,454 18,121,254 18,535,096 18,966,296

14 EXTERNAL TO CONSTRUCTION CONTRACT14.1 Additional consenting LS 1.00 25,000 50,000 50,000 300,000 300,000 14.2 Engineering % 10% 1,537,531 1,747,445 1,812,125 1,853,510 1,896,630 14.3 Design Contingency. Further design to develop/prove concept LS 1.00 - 100,000 100,000 300,000 300,000 14.4 SDC Project Management % 2% 307,506 349,489 362,425 370,702 379,326 14.5 Environmental Management Plan including OMP/Mitigation measures LS 1.00 150,000.00$ 150,000 150,000 150,000 150,000 150,000 14.6 Other Costs (SDC to advise) LS 1 200,000.00$ 200,000 200,000 200,000 200,000 200,000

SUBTOTAL 14 2,220,037 2,596,934 2,674,550 3,174,212 3,225,956

TOTAL ESTIMATED CAPEX REQUIREMENT TOTAL 17,595,348 20,071,388 20,795,804 21,709,308 22,192,252


TEANAU SEWERAGE ‐ KEPLER PROPOSAL

Operational Cost Estimate (Based on daily average flow of 1,500m3 in 35yrs time). 24/08/2018 13:22

Depreciation is Excluded

Approx 2014 daily average flow is 900m3/day, approx 60% of 35yr flow in Flows report.

Last Updated 18‐Jun‐18

Prepared by Roger Oakley, Reviewed by P Jacobson. Numerical check by L Boyd 2 Nov 2018

Minor updates 18 June 2018 to match SDI Basis of Design Report updates.

OPTION ONE BASE CASE

OPTION 2A CONSENTED


OPTION 2B CONSENTED



+ SDI


+ SDI

Item Description Unit Quantity Rate Amount Amount Amount Amount Amount 1 PRELIMINARY & GENERAL

1.1 Base operator input - TeAnau region. Includes personal overheads Hrs pa 800 80.00$ 64,000$ 64,000$ 64,000$ 64,000$ 64,000$ 1.2 Operator support, vehicle, laptop, tools etc LS 1 20,000.00$ 20,000$ 20,000$ 20,000$ 20,000$ 20,000$

Subtotal 1 84,000$ 84,000$ 84,000$ 84,000$ 84,000$

2,3 TE ANAU PONDS (capital items 2 & 3)2.1 Inlet screens, as a percentage of capital value % 1% 100,000.00$ 1,000$ 1,000$ 1,000$ 1,000$ 1,000$ 2.2 Aerators, as a percentage of capital value % 1% 300,000.00$ 3,000$ 3,000$ 3,000$ 3,000$ 3,000$ 2.3 Civil Structures, as a % of capital value % 0.5% 100,000.00$ 500$ 500$ 500$ 500$ 500$ 2.4 Ground maintenance Hrs pa 100 60$ 6,000$ 6,000$ 6,000$ 6,000$ 6,000$ 2.5 Acces road maintenance LS 1 1,000$ 1,000$ 1,000$ 1,000$ 1,000$ 1,000$ 2.6 Disposal of screen debris LS 1 2,000$ 2,000$ 2,000$ 2,000$ 2,000$ 2,000$ 2.7 Annual desludging allowance - treat as separate capital project tonne 0 400$ NA N/A N/A NA NA

Subtotal 2,3 13,500$ 13,500$ 13,500$ 13,500$ 13,500$

4 TELEMETRY AND SCADA FOR WWTP SITE4.1 SCADA and PLC tech support Hrs pa 40 150$ 6,000$ 6,000$ 6,000$ 6,000$ 6,000$ 4.2 Control and instrumentation physical maintenance, as a % of capex LS 200,000$ 5% 10,000$ 10,000$ 10,000$ 10,000$ 10,000$

Subtotal 4 16,000$ 16,000$ 16,000$ 16,000$ 16,000$

5 MEMBRANE FILTRATION AT PONDS (base on 4.5MLD plant)5.1 Chemical usage LS 1 12,000$ NA 12,000$ 12,000$ 12,000$ 12,000$ 5.2 Membrane replacement (5yr guarantee, 7yr budget duration) year 0.14 179,200$ NA 12,800$ 25,600$ 12,800$ 25,600$ 5.3 Civil at 0.5% of capital % 0.5% 800,000$ NA 2,680$ 4,000$ 2,680$ 4,000$ 5.4 M&E at 1% of capital % 1% 2,000,000$ NA 13,400$ 20,000$ 13,400$ 20,000$ 5.5 Additional Operator input 14 hrs per week hrs 700 80$ NA 56,000$ 56,000$ 56,000$ 56,000$

Subtotal 5 -$ 96,880$ 117,600$ 96,880$ 117,600$

6 RISING MAIN PUMPSTATION TO KEPLER6.1 Pumpstation civil, as a percentage of capital value m 0.5% 175,000$ 875.00$ 875$ 875$ 875$ 875$ 6.1 Pumpstation M+E, as a percentage of capital value m 1% 500,000$ 5,000.00$ 5,000$ 5,000$ 5,000$ 5,000$

Subtotal 6 5,875.00$ 5,875$ 5,875$ 5,875$ 5,875$

7 RISING MAINOdour control maintenance on pipeline, and carbon filters LS 1 6,000$ 3,000$ 3,000$ 3,000$ 3,000$

Civil maintenance at 0.5% of capital % 0.5% 6,957,301$ 34,787$ 34,787$ 34,787$ 34,787$ 34,787$ Subtotal 7 40,787$ 37,787$ 37,787$ 37,787$ 37,787$

8 KEPLER ELECTRICAL SUPPLY AND MONITORINGM&E at 1% of capital % 1% 254,100 2,541.00$ 2,541$ 2,541$ 2,541$ 2,541.00$

Subtotal 8 2,541.00$ 2,541$ 2,541$ 2,541.00$ 2,541.00$ 9 ODOUR CONTROL - Trickling filter, biofilter and chem dosing.

Soil filter rehabilitation LS 1 2,000$ 2,000.00$ 2,000$ 2,000$ N/A N/ACivil, as a percentage of capital value LS 0.5% 1,100,000$ 5,500.00$ 5,500$ 5,500$ N/A N/A M+E, as a percentage of capital value LS 1% 600,000$ 6,000.00$ 6,000$ 6,000$ N/A N/A

Oxidant chemicals, 10% sodium hypochlorite. IBCs 2 3,000.00$ 6,000.00$ N/A N/A N/A N/AAdditional Operator input hrs 260 80.00$ 20,800.00$ 20,800$ 20,800$ N/A N/A

Subtotal 9 40,300.00$ 34,300$ 34,300$ -$ -$ 10 KEPLER SITE MAINTENANCE

Fencing and gates LS 1 2,000$ 2,000$ 2,000$ 2,000$ 2,000$ 2,000$ Tracks, incl irrigator wheel tracks LS 1 5,000$ 5,000$ 5,000$ 5,000$ N/A N/ATree pruning LS 1 3,000$ 3,000$ 3,000$ 3,000$ 3,000$ 3,000$ Peat bog and 'bridges' over for irrigator LS 1 1,000$ 1,000$ 1,000$ 1,000$ N/A N/AGround maintenance in odour/SDI treatment compound LS 1 1,000$ 1,000$ 1,000$ 1,000$ 1,000$ 1,000$ Paddock Development, replant grass Ha/yr 10 500$ 5,000$ 5,000$ 5,000$ 5,000$ 5,000$

Subtotal 10 17,000$ 17,000$ 17,000$ 11,000$ 11,000$

11 CENTRE PIVOT IRRIGATION11.1 Annual overhaul by specialist, plus any callouts. LS 1 4,000$ 4,000$ 4,000$ 4,000$ N/A N/A11.2 CP Spray nozzle and filter maintenance LS 1 3,000$ 3,000$ 3,000$ 3,000$ N/A N/A11.3 CP Tyres, general parts replacement LS 1 3,000$ 3,000$ 3,000$ 3,000$ N/A N/A11.4 M+E, as a percentage of capital value LS 1% 566,740 5,667$ 5,667$ 5,667$ N/A N/A

Subtotal 11 15,667$ 15,667$ 15,667$ -$ -$

12 SDI IRRIGATION12.1 SDI backflushing chemicals LS 1 18,000$ N/A N/A N/A 18,000$ 18,000$ 12.2 Civil, as a percentage of capital value. Assume 80% of item 12 LS 0.5% 2,907,438$ N/A N/A N/A 14,537$ 14,537$ 12.3 M+E, as a percentage of capital value. Assume 20% of item 12 LS 1% 726,860$ N/A N/A N/A 7,269$ 7,269$ 12.3 Additional Operator input hrs 260 80.00$ N/A N/A N/A 20,800$ 20,800$

Subtotal 12 -$ -$ -$ 60,605.79$ 60,605.79$

13 CONSENT MONITORING13.1 6 Monitoring bores sampling LS 24 150$ 3,600$ 3,600$ 3,600$ 3,600$ 3,600$ 13.2 Monitoring, overseer, reporting, updating EMP to meet consent requirements LS 1 25,000$ 25,000$ 25,000$ 25,000$ 25,000$ 25,000$ 13.3 Maintaining and calibrating spray drift and soil moisture sensors LS 1 3,000$ 3,000$ 3,000$ 3,000$ 3,000$ 3,000$

Subtotal 13 31,600.00$ 31,600$ 31,600$ 31,600.00$ 31,600.00$

14 PASTURE OPERATION (see estimate below)14.1 Operating costs LS 1 237,775$ 237,775$ 237,775$ 237,775$ 237,775$ 14.2 Income from baleage LS 1 247,240.00-$ 247,240-$ 247,240-$ 247,240-$ 247,240-$ 247,240-$

Subtotal 14 -$9,465 -$9,465 -$9,465 -$9,465 -$9,465

Power POWER- all items - see est on separate spreadsheetP.1 Te Anau Pumpstation KWh 158,601 0.14$ 22,204$ 22,204$ 22,204$ 22,204$ 22,204$ P.2 TF pumpstation KWh 34,762 0.14$ 4,867$ 4,867$ 4,867$ N/A N/AP.3 Centrepivot pumpstation KWh 32,589 0.14$ 4,563$ 4,563$ 4,563$ N/A N/AP.4 Pond inlet screen KWh 6,570 0.14$ 920$ 920$ 920$ 920$ 920$ P.5 Aerators (6) KWh 262,800 0.14$ 36,792$ 36,792$ 36,792$ 36,792$ 36,792$ P.6 Membrane inlet screen KWh 6,570 0.14$ N/A 920$ 920$ 920$ 920$ P.7 Membrane Filtration plant KWh 158,601 0.14$ N/A 21,094$ 22,204$ 22,204$ 22,204$ P.8 Irrigator wheel drive KWh 35,040 0.14$ 4,906$ 4,906$ 4,906$ N/A N/AP.9 SDI system pumps KWh 76,042 0.14$ N/A N/A N/A 10,646$ 10,646$

P.10 Elec capacity charges at Ponds (250kVA transformer assumed) LS 1 16,000.00$ 16,000$ 16,000$ 16,000$ 16,000$ 16,000$ P.11 Elec capacity charges at Kepler (100kVA transformer assumed) LS 1 8,000.00$ 8,000$ 8,000$ 8,000$ 8,000$ 8,000$

Subtotal power 98,251$ 120,264$ 121,375$ 117,686$ 117,686$

TE ANAU TOTAL ANNUAL OPEX COSTS TOTAL 356,056$ 465,949$ 487,780$ 468,009$ 488,729$ check 356,056$ 465,949$ 487,780$ 468,009$ 488,729$

TE ANAU OPEX NET PRESENT VALUE AT 6%, 25 YEARS factor 12.783 4,551,459$ 5,956,231$ 6,235,287$ 5,982,560$ 6,247,424$

Manapouri capex 1,450,000.00$ 1,450,000.00$ 1,450,000.00$ 1,450,000.00$ 1,450,000.00$ Manapouri opex 29,000.00$ 29,000.00$ 29,000.00$ 29,000.00$ 29,000.00$

MANAPOURI OPEX NET PRESENT VALUE AT 6%, 25 YEARS factor 12.783 370,707$ 370,707$ 370,707$ 370,707$ 370,707$

Te Anau capex from 'Main Estimate' spreadsheet 17,595,348.11$ 20,071,388.50$ 20,795,804.50$ 21,709,307.89$ 22,192,251.89$ Total NPV Te Anau and Manapouri 23,967,514.31$ 27,848,326.61$ 28,851,798.16$ 29,512,574.63$ 30,260,382.39$

Excluded:

Depreciation

SDC head office staff time

Other references:

Opex estimate for options in MWH 2006 report 'Initial Consideration of Future Treatment and Disposal Options

Pumping and headloss estimates in MWH Dec 2008 draft report 'Te Anau Sewerage ‐ WWTW to Kepler Block Rising Main'

Notes:

Fixed line charges are potentially very high, highlighting the need for load management in peak times

Estimate for Pasture Maintenance and Dry Matter Production last updated 28 Sept 2017

Note: Scope of estimate limited to the 125Ha North Kepler block.

Least cost (optimistic)

Mid range low range (conservative)

Item Description Unit Quantity Rate Amount Amount Amount 1 Farm Operating Costs

1.1 Pasture management by Landcorp LS 1 3,000.00$ 3,000.00$ 1.2 Fertiliser (probably need 2 spreads pa orf Urea, for N shortage) per Ha/yr 125 95.00$ 11,875.00$ 1.3 Cut of baleage, incl transportation of cut asap - irrigated land, 11.25t/Ha per Ha/yr 40 1,970.00$ 78,800.00$ 1.4 Cut of baleage, incl transportation of cut asap - unirrigated land, 9.5t/Ha per Ha/yr 85 1,660.00$ 141,100.00$ 1.5 Lab testing of baleage. pa 1 3,000.00$ 3,000.00$

Subtotal 237,775.00$ 237,775.00$ 237,775.00$ 2 INCOME per annum - optimistic

2.1Irrigated land - with recovery of 10.4 tonne dry matter/Ha/yr. Use 40Ha for the'irrigated' 75Ha, as irrigated area sized to cope with peak flows. tonne DM 416 280.00-$ 116,480.00-$

2.2 Unirrigated land - based on recovery of 9t/Ha/yr on 75Ha tonne DM 675 280.00-$ 189,000.00-$

3 INCOME per annum - mid range

3.1Irrigated land - with recovery of 10.4 tonne dry matter/Ha/yr. Use 40Ha for the'irrigated' 75Ha, as irrigated area sized to cope with peak flows. tonne DM 416 140.00-$ 58,240.00-$


4 INCOME per annum - conservative

4.1Irrigated land - with recovery of 10.4 tonne dry matter/Ha/yr. Use 40Ha for the'irrigated' 75Ha, as irrigated area sized to cope with peak flows. tonne DM 416 -$ -$


Subtotal 305,480.00-$ 247,240.00-$ 189,000.00-$

Total 67,705.00-$ 9,465.00-$ 48,775.00$

Notes on Pasture costs:

1 Also refer to section E, from p57 of Hydroservices April 2013 Report 'Report on Kepler Farm Site Assessment….' that was submitted as part of the consent application.

2 Travis Leslie, Landcorp site manager, doesn't envisage anything. So small allowance only

3 Travis Leslie, Landcorp site manager: local cost is $45 ‐50/Ha/spread for urea, assuming a higher rateof $80kg/Ha

4 T Leslie, local costs to cut and remove baleage from site are $42/round bale with a 600kg wet weight and 40%DM. ie $42 for 240kgDry Matter

5 Davoren, technical memo 2/11/2017 suggests a revised harvestable range of 8.0‐12.75t/Ha/yr for irrigated land. ‐ Use mid range estimate of 10.4 t/Ha/y

6 Davoren, technical memo 2/11/2017 suggests a revised harvestable range of 6‐12t/Ha/yr for unirrigated land ‐ Used mid range estimate of 9t/Ha/y

7 Davoren, technical memorandum 2/11/2017: Dean Carson suggest value of $280 / t DM based on 2016‐2017 season

Selected risk level forbaleage income

Appendix J Comparison of SDI and CPI Schemes

Te Anau Wastewater SchemeComparison with other Subsurface and Centre Pivot Schemes Updated: 21‐Aug‐18

Scheme Area (Ha)ADF Design

flow (m3/day)

Peak design flow (m3/day)

No. of irrigation blocks

Area per block (Ha)

Av Dry Weather Flow (mm/day)

Peak Flow (mm/day)

Peak/ADFTotal Nitrogen

leached* (kg/Ha/yr)

UV pre‐treatment

Year built Buffer

storage (m3)Storage days

at ADF

Pre‐treatment process

(see notes)Soils + comments

SDI SchemesTiwai Smelter 5 300 6 0.83 0 6 No 1998 100 0.5 RBC Organic over pea gravelMaketu (Stg 1&2) 4.2 635 840 8 0.53 15 20 1.3 15mg/l applied n 1 SBR‐DP LoamOmaha

golf course 6.3 556 1500 52 0.12 8.8 24 2.7 Yes 2001 HRAP, SF Turf over sand over marine deposits. sand dunes 0.6 60 600 3 0.20 10.0 100 10.0 y 2004 Sand dunes. Winter use onlyJones Rd 9.8 534 2200 24 0.41 5.5 22 4.1 y 1988 Peat over high water table

Total consented 16.7 822 4300 44 15mg/l applied y 38,000 46Dam used for extreme flow storage and summer irrigation supply.

Pauanui

Air strip 5 320 16 0.31 6.4 y 2009 DP 1 SBR‐DP Low rate as close to drinking water boresPark 1.24 988 4 0.31 80 y Sand golf club 1.50 300 3 0.50 20 y Sand Medium Strip 0.1 1500 8 0.01 1500 y Sand Total consented 7.84 3108 31

Kepler SDI52* (hydrus)

21mg/l appliedsummer 55 3000 4500 30 1.83 5.5 8.2 1.5 n 15,000 5 ASP+ MFwinter 55 1300 2000 30 1.83 2.4 3.6 1.5 n 15,000 12

CPI schemes.

Taupo View Rd stg 1 119 5,000 approx 8 pivots 2.0 to date 1545 (overseer) <20

measuredn S2‐ 2008 Diurnal 2 T/F clarifier alluvial and airfall volcanic

Rolleston* (stage 2)

81 5,500 actual 13,500 6 pivots 712.8 consent (64mm/5d)

7mg/l applied (consent)

y S2‐ 2013 No <0.1 AS‐BNR Lismore stoney silt

Kepler CPI44* (hydrus)

27mg/l appliedsummer 69 3000 4500 4 pivots 4.3 6.5 1.5 n 23,000 ASPwinter 69 1300 2000 4 pivots 1.9 2.9 1.5 n 23,000 ASP

General notes.Estimated figures shadedNitrogen leached based on wetted irrigation area.Hydrus N leaching figures for Kepler are annual average under the wetted area, based on expected flows in 2042, using Aqualinc Hydrus report of July 2018Rolleston data from Alec Mitchell paper to WaterNZ 2015All CPI schemes and Kepler SDI are cut and carry.Kepler CPI and SDI options comply with 32kgN/Ha/yr average over whole farm via OverseerAll other SDI schemes rely on soil processes to reduce N. Treatment systems legend:RBC‐ Rotating bio contactor, HRAP‐high rate aerated pond,ASP ‐aerated storage pond,SBR ‐sequential bio reactor,MF ‐membrane filtration, SF‐ Sand filter, T/F ‐trickling filter. BNR ‐biological nitrogen removal, OLS‐Off line storage. DP‐ decant pond

P:\_2012 Onwards\Southland District Council\80508264 Te Anau WWTP\F ‐ Design\F1 ‐ Concept and sampling\K ‐ SDI\F Other SDI schemes\Irrigation scheme comparison v2 21/08/2018

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TE ANAU TREATED WASTEWATER SCHEME BASIS OF DESIGN · Rima Krause Roger Oakley PREPARED BY 27 August...

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Transcript of TE ANAU TREATED WASTEWATER SCHEME BASIS OF DESIGN · Rima Krause Roger Oakley PREPARED BY 27 August...