SURFACE/ STORMWATER MANAGEMENT STRATEGY:

Daleston, Phileo Australia

May 2015

Document history

Revision: Revision no. 02 Author/s Stuart Cleven Amanda Shipp Checked Jonathon McLean Approved Jonathon McLean

Distribution: Revision no. 02 Issue date 13 May 2015 Issued to Courtney Sung (PTA) Description: SWMS

Contact: Name Alluvium Consulting Pty Ltd ABN 45 653 522 596 Contact person Stuart Cleven Ph. 0408 501 761 Email Stuart.Cleven@alluvium.com.au Address 21 – 23 Stewart Street,

Richmond Victoria 3121

Ref: R:\Projects\2014\080_Daleston_SWMS\1_Deliverables\SWMS\P114080_R01V02a_Daleston_SWMS.docx

SWMS Daleston i

Contents

1 Introduction 4

Reference material 4

2 Site overview 5

2.1 Catchments 9

2.2 Site photos 10

3 Site analysis 12

3.1 Hydrologic and hydraulic analysis 12 Waterways 14

3.2 Stormwater quality analysis 14

3.3 Criteria for SWMS 14

4 Proposed local drainage system 15

4.1 Minor drainage system 15

4.2 Major drainage system 15

5 Proposed waterway corridor 19

5.1 Waterway corridor 19

5.2 Constructed waterway 22 Existing conditions 22 Waterway design 22 Flood levels 23 Waterway outfall 23

5.3 Waterway crossings 25

6 Proposed stormwater quality treatment system 28

6.1 Performance against BPEM 28

6.2 Treatment asset descriptions 31 Wetlands 31 Sediment Basins 31

6.3 Treatment asset parameters 32

7 Stormwater harvesting 34

Assumptions 34 Opportunities 34 Water balance analysis 35 Options assessment 36

8 Development Services Scheme Assets Required 37

8.1 Required assets 37

8.2 Timing of assets 37

9 Conclusion 38

Attachment A Wetland Concept design 39

Attachment B Sediment basin concept design 44

Attachment C Rational Calculations 48

SWMS Daleston ii

Attachment D Treatment asset calculations 50

Attachment E Constructed waterway design 54

Attachment F RORB sub-catchments 56

Figures Figure 1. Site location 5 Figure 2. Catchment context 6 Figure 3. Black Forest Road Development Services Scheme Werribee 7 Figure 4. Melbourne Water Proposed Greens Road Strategy 7723 7 Figure 5. Preliminary Black Forest Road North Precinct Structure Plan 8 Figure 6. Flora and fauna assessment 9 Figure 7. Overall Catchment Plan 10 Figure 8. Site inspection photos 11 Figure 9. MW RORB model for southern catchment 12 Figure 10. Minor sub-catchments with pipe network 17 Figure 11. Overland flow paths 18 Figure 12. Waterway corridor (Melbourne Water’s Waterway Corridor Guidelines) 19 Figure 13. Constructed Waterway corridor requirements (Melbourne Water’s Waterway Corridor Guidelines) 20 Figure 14. Waterway corridor 21 Figure 15. Long-section for constructed waterway 22 Figure 16. Typical cross-section of constructed waterway 23 Figure 17. Constructed waterway design, with flood levels 24 Figure 18. Waterway crossings in study area 25 Figure 19. Typical culvert arrangement 26 Figure 20. Long-section of constructed waterway with crossings 27 Figure 21. Location of stormwater treatment assets 29 Figure 22. MUSIC schematic for treatment assets 30 Figure 23. Stormwater harvesting and reuse schematic 34 Figure 24. Stormwater harvesting opportunities 35 Figure 25. Daleston stormwater harvesting water balance 35 Figure 26. Plan view for Asset 3 and asset 7 40 Figure 27. Cross-section AA 41 Figure 28. Cross-section BB 42 Figure 29. Cross-section CC 43 Figure 30. Plan view for Assets1b, 4a, and 4b 45 Figure 31. Plan view for Asset 1a, 2, 5, and 6 46 Figure 32. Typical section view for Assets 1a, 1b, 2, 4a, 4b, 5, 6 47 Figure 33. RORB sub-catchments 57

Tables Table 1. Davis Rd East subcatchments 9 Table 2. AR&R Design Rainfall parameters (Werribee) 12 Table 3. Adopted RORB parameters 13 Table 4. Developed flows analysis (100 year ARI) 13 Table 5. Daleston design flows (rational method) 13 Table 6. Channel design flows (RORB) 14 Table 7. Davis Rd East minor flows (rational method) 15 Table 8. Davis Rd East major flows (rational method) 16 Table 9. Crossing parameters 25 Table 10. Fraction Impervious (based on Melbourne Water’s MUSIC Guidelines) 28

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Table 11. Overall treatment train results 28 Table 12. MUSIC results for each treatment asset 31 Table 13. Wetland footprint areas 32 Table 14. Treatment asset parameters 33 Table 15. Location of stormwater harvesting opportunities (refer to Figure 24) 34 Table 16. Irrigation demand 36 Table 17. Stormwater reuse reliability 36 Table 18. Development Services Scheme assets 37 Table 19. Daleston rational calculations 49 Table 20. Daleston sediment pond calculations 51 Table 21. Velocity calculation – Wetlands 52 Table 22. Velocity calculation – sediment ponds 53 Table 23. Constructed waterway hydraulic parameters 55

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1 Introduction

Alluvium Consulting Australia Pty Ltd (Alluvium) has been engaged by Phileo Australia Ltd (Phileo) to prepare a Surface/Storm Water Management Strategy (SWMS), in support of its permit application for the Daleston site.

The objectives of this SWMS are to propose management strategies for:

Stormwater quantity

Stormwater quality

Existing and constructed waterways

Through meeting these objectives, this SWMS acts as a critical component of the development servicing strategy and ensures stormwater is managed in accordance with Melbourne Water’s requirements. Information with respect to scheme assets are provided at a concept design level.

The subject site is contained within the Precinct Structure Plan (PSP) 42.1 – Blackforest Road North, which is currently under development. This SWMS is to form part of the 96a planning permit application to be submitted inline with the PSP.

This project builds on work previously undertaken by Alluvium in 2011 and 2012 to inform a drainage strategy inline with Melbourne Water (MW) Development Service Scheme (DSS) provisions for the subject area. In principle agreements made with Metropolitan Planning Authority (MPA) and Melbourne Water (MW) as part of the initial drainage strategy has been revised and incorporated into the SWMS.

Reference material

Melbourne Water’s Greens Road Strategy 7723

Melbourne Water’s Proposed Black Forest Road Development Services Scheme Werribee

Black Forest Road North Precinct Structure Plan (42.1) advice (MPA)

Site visit and inspection (Alluvium, 2011)

Alluvium (2011a). Phase 1 existing conditions summary report and mapping – Phileo Property – PSP 42 North. Report P111042_R01 by Alluvium for Phileo Australia, Melbourne.

Alluvium (2011b). Phase 2 Initial drainage strategy concept drawings – Phileo Property – PSP 42 North. By Alluvium for Phileo Australia, Melbourne.

Alluvium (2012). Phase 3 Revised drainage strategy drawings – Phileo Property – PSP 42 North. By Alluvium for Phileo Australia, Melbourne.

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2 Site overview

The Daleston site covers an area of approximately 328 hectares and is generally bound by Greens Road to the north, the planned Outer Metropolitan Ring Road to the west, Blackforest Road to the south and adjacent parcels to the east (refer to Figure 1). The topography of the site is characterised by gentle slopes with grades typically in the order of 0.5 to 1.5 %. The study area generally falls in an easterly direction. A site contour plan is provided in Appendix E.

The Daleston site is located within PSP 42.1, which is currently under development. Alluvium’s report for the Daleston site has been undertaken in accordance with planning advice by the Metropolitan Planning Authority (MPA) and Melbourne Water in relation to the preparation of the PSP and Development Services Scheme (DSS).

Figure 1. Site location

The existing waterway through the development area represents both constraints and opportunities. The unnamed tributary of Lollypop Creek has been heavily degraded through agricultural practices including vegetation clearance, re-grading and cropping post European settlement. As result of these practices there appears to be no significant riparian vegetation or habitat for flora and fauna along the tributary and as such no significant environmental values (Alluvium 2011a).

While the degraded the tributary appears to be fairly stable, with no signs of erosion or scour, there is potential for the system to become unstable with increased pressures associated with urban development. This includes vegetation removal, stormwater pollution, increased flow volumes and frequencies, alteration of stream form, reduction in the overall floodplain width and decline in stream health (Alluvium 2011a).

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The required water quality treatment assets provide an opportunity for increasing amenity in the area. An external, undeveloped catchment flows into this development area, which needs to be managed.

The catchment context of the study area is shown in Figure 2. The study area is part of the Lollipop creek sub-catchment within the Little River catchment of the Werribee Basin. Lollipop Creek is linked to the neighbouring Werribee River through the Werribee River ’breakaway’. This has important implications for the retardation of flows within the Lollipop Creek catchment.

Figure 2. Catchment context

The landholding is spread over two drainage catchments. The southern part of the study area flows south-east and is part of the Black Forest Road DSS (Figure 3). The relevant property reference numbers for this DSS are 1, 2, 3, 4 and 25. The DSS includes flows from the study area entering a constructed waterway (at east end of Property reference No. 4) and then being treated by a wetland within a retarding basin north of Blackforest Road. The retarding basin has been sized to ensure peak flows do not exceed the capacity of the downstream constructed waterway originally design as part of the Lollypop Creek DSS.

The remainder of the study area is part of the Greens Road Strategy 7723 (Figure 4). While there is no DSS a suitable strategy was agreed to by Melbourne Water and Wyndham City Council. It outlines the need for a constructed waterway through the study area. The water quality treatment strategy uses sediment basins along the waterway and two wetlands at the downstream end of the waterway to ensure all runoff is treated to best practise requirements. As per the Lollypop Creek DSS and past agreements with MPA and MW no retarding of site runoff is required to ensure flood peaks do not coincide with Lollypop Creek main stem and the Werribee River breakaway flows.

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Figure 3. Black Forest Road Development Services Scheme Werribee

Figure 4. Melbourne Water Proposed Greens Road Strategy 7723

A draft PSP has been developed with MPA. The current features of the PSP are presented in Figure 5. Some important features include the future Outer Metropolitan Ring transport corridor (Public Acquisition overlay), active open space and education zones along the waterway and a regional wetland. The Outer Metropolitan Ring Road on the western boundary and nearby Regional Rail Link to the east have implications for the channel design.

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Figure 5. Preliminary Black Forest Road North Precinct Structure Plan

A flora and fauna assessment completed in 2011 (Biosis 2011) found no flora species of national significance. However, two ecological vegetation classes (EVCs) were found in the study area in a previous assessment in 2008/2009, Plains Grassland and Herbland EVCs. One state significant flora species was recorded during the current assessment, Melbourne Yellow-gum Eucalyptus leucoxylon subsp. connata (Figure 6).

No fauna species of national or state significance were recorded during the current assessment. However, suitable habitat for three species with national significance was identified, including Growling Grass Frog Litoria raniformis Plains-wanderer Pedionomus torquatus and Golden Sun Moth Synemon plana: The presence of suitable habitat resulted in targeted survey for Growling Grass Frog Litoria raniformis and Plains-wanderer Pedionomus torquatus. No threatened species were recorded during these targeted surveys.

A cultural heritage assessment for the study area was completed in 2012 (AHMS 2012). The assessment found no Aboriginal places were identified within the activity area during the survey and complex assessment. The assessment recommended no further investigation or specific salvage or conservation recommendations are proposed for VAHR 7822-3484-41.

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Figure 6. Flora and fauna assessment

2.1 Catchments There are three major catchments on the site (Figure 7), flowing generally to the east. The size and direction of these catchments are provided in Table 1. These are the base catchments, which will be altered slightly when the major and minor flows are considered in detail.

Table 1. Davis Rd East subcatchments

Internal/ External Major Catchment Catchment Area (ha) Flow Direction

Internal Waterway- north 1 53 South-East

2 18.7 South-East

3 16.4 South-East

Waterway - south 4 39.2 North-east

5 16.8 North-east

6 15.4 North-east

7 27.5 North-east

Southern Catchment 8 103 South-East

External Upstream catchment, outside urban growth boundary, entering waterway from west

396 East

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Figure 7. Overall Catchment Plan

2.2 Site photos The following photos demonstrate some features of the Daleston site. These photos were taken by Alluvium in January 2011 during an initial investigation of the waterway. The unnamed tributary has been heavily degraded through agricultural practices including vegetation clearance and re-grading to allow wheat cropping within the property (Figure 8). The channel geometry appears to be shallow and at a flat grade, which indicates that significant flood events will be largely unconfined with floodplain widths varying across the property, reliant on the topography. Prior to European settlement this tributary would have been characterised by a series of pools and riffles and a stand of healthy riparian vegetation.

Two large farm dams, one located immediately upstream of the property boundary (Photo d, Figure 8) and the other located within the Phileo property at downstream boundary (Photo e, Figure 8) are both located on the unnamed tributary, and would be removed as part of the proposed works.

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Figure 8. Site inspection photos

(a) (b)

(c) (d)

(e) (f)

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3 Site analysis

3.1 Hydrologic and hydraulic analysis The hydrologic analysis of the northern catchment was based on the RORB model developed by Melbourne Water as part of the Lollypop Creek DSS. Whereas the hydrologic analysis of the southern catchment was based on a separate RORB model developed by Melbourne Water in response to changes to the urban growth boundary (Figure 9). A map of the RORB sub-catchments for the Lollypop Ck RORB model is provided in Attachment F.

Figure 9. MW RORB model for southern catchment

These RORB models were reviewed refined based on changes to the urban growth boundary to consider the flows through the study site. The following design rainfall parameters (Table 2) and RORB parameters (Table 3) were adopted for the hydrologic RORB modelling. Additional sub-catchment flows have been estimated using the rational method.

Table 2. AR&R Design Rainfall parameters (Werribee)

Parameter Value

1hr 2yr 17.97

12hr 2yr 3.50

72hr 2yr 0.90

1hr 50yr 38.25

12hr 50yr 7.07

72hr 50yr 1.95

Skew 0.38

F2 4.29

F50 14.90

Zone 1

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Table 3. Adopted RORB parameters

Parameter Value (Lollypop Ck RORB model) Value (Tributary 7713)

M, 0.7 0.8

Kc 23 2.25

IL 15 15

CL 2.05

RoC (100 year ARI) 0.6

As per the Lollypop Creek DSS and past agreements with MPA and MW no retarding of site runoff is required to ensure flood peaks do not coincide with Lollypop Creek main stem and the Werribee River breakaway flows. To demonstrate compliance with this principle the results for the fully developed conditions within the PSP42.1 and its impacts on downstream flows within Lollypop Creek are shown in Table 4.

Table 4. Developed flows analysis (100 year ARI)

Parameter Existing Conditions Developed catchment

Peak flows entering study area 21.6 m3/s (2 h) 21.8 m

3/s (2 h)

Peak flow at Lollipop Creek 148.8 m3/s (9 h) 14.7 m

3/s (9 h)

Difference 0.86 m3/s (0.6 %) increase

Alternatively retardation of the 100 year ARI event is required for peak flows draining to the south to ensure constructed waterways designed prior to the expansion of the urban growth boundary are not under sized. As this retarding basin is located outside of the subject property no changes have been recommended to the adopted MW stage storage relationship or the 100 year ARI contributing catchments.

The design flows that have been used for fully developed conditions to assess pipe and road capacity requirements have been undertaker using the rational method and are provided in Table 5 and Attachment C. For the analysis of minor (piped) flow and major, overland flows some catchments are divided further.

Table 5. Daleston design flows (rational method)

Major Catchment Catchment Area (ha) Minor flow

(5 year RAI)

Major flow

(100 year flow)

Waterway- north 1 53 3.81 m3/s 8.1 m

3/s

2 18.7 1.67 m3/s 3.6 m

3/s

3 16.4 1.55 m3/s 3.3 m

3/s

Waterway - south 4 39.2 3.20 m3/s 6.8 m

3/s

5 16.8 1.57 m3/s 3.4 m

3/s

6 15.4 1.46 m3/s 3.2 m

3/s

7 27.5 2.10 m3/s 4.5 m

3/s

Southern Catchment 8 100.8 8.09 m3/s 17.3 m

3/s

Flows for sizing of the waterway have been undertaken using RORB flows and are shown in Table 6.

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Table 6. Channel design flows (RORB)

Chainage Q100 Q10 Q2 Q3month

2800 21.8 m3/s 11.6 m

3/s 5.1 m

3/s 1.37 m

3/s

2590 21.2 m3/s 10.2 m

3/s 4.2 m

3/s 1.12 m

3/s

1950 21.1 m3/s 10.3 m

3/s 4.1 m

3/s 1.1 m

3/s

870 21.5 m3/s 9.6 m

3/s 4.0 m

3/s 1.07 m

3/s

520 22.6 m3/s 10.1 m

3/s 4.4 m

3/s 1.18 m

3/s

Waterways The constructed waterway was designed in line with the Melbourne Water Constructed Waterway Guidelines. The Melbourne Water Waterway Corridor Guidelines, along with consultation with Melbourne Water, has been used to establish appropriate conditions surrounding the waterway. 12d and HEC-RAS have been used to design the waterway and model the major flows through the waterways to determine flood levels. Combined LiDAR and feature survey undertaken by Phileo has formed the digital terrain model.

3.2 Stormwater quality analysis A MUSIC (Model for Urban Stormwater Improvement Conceptualisation) modelling approach has been used to establish the proposed treatment train strategy. The model estimates the amount of pollutants the catchment produces, the performance of treatment measures and the pollutant load generated once the catchment is treated.

3.3 Criteria for SWMS The criteria for the proposed strategy, based on the analysis of existing conditions are as follows:

Meet best practice pollutant removal targets

Convey major flows through the site via the constructed waterway and overland flows along road reserves

Convey minor flows through local catchments in a piped network

Hydraulic size of creek road crossings

The following additional criteria, at the request of MPA is:

Assessment of stormwater harvesting potential

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4 Proposed local drainage system

The proposed internal drainage system should be designed and constructed in accordance with the minor / major drainage system philosophy. For drainage assets within a catchment area of 60 hectares, Council design standards are expected to apply. For drainage assets greater than 60 hectares, Melbourne Water design standards are expected apply.

4.1 Minor drainage system The minor drainage system would consist essentially of an underground piped network and should be designed to accommodate a 1 in 5 year average recurrence interval event (ARI).

Table 7. Davis Rd East minor flows (rational method)

Major Catchment

Catchment Contributing catchment

Minor flows ( 5 year)

Maximum pipe size required*

Pipe capacity

Waterway- north

1a 18.2 1.55 m3/s 900 mm 1.5 m

3/s

1b 34.8 2.62 m3/s 1200 mm 3.1 m

3/s

2 18.7 1.67 m3/s 1050 mm 2.3 m

3/s

3 16.4 1.55 m3/s 825 mm 1.6 m

3/s

Waterway - south

4a 20.6 1.98 m3/s 1050 mm 2.7 m

3/s

4b 18.6 1.62 m3/s 1050 mm 1.9 m

3/s

5 16.8 1.57 m3/s 900 mm 1.7 m

3/s

6 15.4 1.46 m3/s 900 mm 1.7 m

3/s

7 27.5 2.10 m3/s 1200 mm 2.7 m

3/s

Southern Catchment

8a 4.3 0.46 m3/s 600 mm 0.6 m

3/s

8b 30.3 2.79 m3/s 1050 mm 3.1 m

3/s

8c 66.2 5.18 m3/s 1500 mm** 7.8 m

3/s

*Equivalent pipe size if only one pipe was used ** Pipe upsized to provide additional combined road and pipe capacity and align with DSS

Through catchment 1-7, 8a and 8b that drain towards the Blackforest Road wetland/retarding basin there are no locations at which the pipe network will become the responsibility of Melbourne Water. As catchment 8c is 56 ha on the western side of Westbrook Drive and 66 ha in total when taking into account the western side, the drainage pipeline will become the property of Melbourne Water for the section east of Westbrook Drive.

4.2 Major drainage system The major drainage system will convey the 100 year ARI flows through the study area. This consists of the waterway corridor and road reserves throughout the development. The flows from the undeveloped, upstream, external catchment will be contained within the waterway corridor – see Figure 17 below for flood levels. The flows required to be conveyed in road reserves will be the 100 year flow minus the 5 year flow (or pipe capacity) which will be contained within the minor piped drainage system. These gap flows are shown in Table 8. The overland flow path and flow location points are provided on Figure 9.

It is assumed for the two catchments (catchments 2 and 6) draining into the waterway near Westbrook drive, that flows could be conveyed in the minor roads that run parallel to Westbrook Drive, therefore a 12 m road width is assumed adjacent to Westbrook Drive.

Based on the road width and slope, and the maximum allowable nature strip cross-fall of 10%, the capacity that can be contained within the main road reserves is shown in Table 8. This capacity has been determined using HEC-RAS based on the Melbourne Water floodway safety criteria for residential streets used as floodways:

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Manning’s ‘n’ = 0.020

Average velocity time average depth should be less than 0.35

Average depth should be less than 0.30 m

At each flow location, the road reserve will adequately contain the gap flows and therefore pass the 100 year flows through the development safely.

Table 8. Davis Rd East major flows (rational method)

Overland flows Road Capacity

Flow location

Contributing overland

catchment

Minor flows Pipe capacity

(m3/s)

Major flows (m3/s)

Q (gap)

(m3/s)

Road Width

(m)

Slope Road Capacity (m3/s)

A 1a 1.53 3.31 1.78 26 1.7 % 8

B 1b 3.10 5.56 2.46 14 2.0 % 3

C 2 2.34 3.59 1.25 12 2.0 % 3

D 3 1.56 3.35 1.79 12 1.3 % 3

E 4 2.69 6.83 4.15 16 0.3 % 4.75

F 5 1.89 3.39 1.50 13 1.3 % 3

G 6 1.68 3.15 1.47 12 0.5 % 3

H 7a 1.73 2.77 1.04 16 1.3% 2

I 7b 2.68 2.70 0.02 16 0.5% 4.75

J 8a 0.56 1.00 0.44 16 0.7% 4.75

K 8b 3.10 6.01 2.91 30 1.1% 8

L 8c 7.85 11.03 3.18 16 2.3% 3.5

At flow points K and L, for catchment 8b and 8c, the 50 year ARI flow will need to be conveyed under Westbrook Drive to meet VicRroads freeboard requirements. At this point underground pipes and side entry pits will need to be upgraded to convey the 50 year ARI flow. Downstream the pipe capacity can be reduced back to the 5 year ARI with a bubble up pits on the east side of the road.

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Figure 10. Minor sub-catchments with pipe network

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Figure 11. Overland flow paths

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5 Proposed waterway corridor

An unnamed tributary of Lollipop Creek (Asset ID 7723) runs through the Daleston site. Alluvium was engaged by Phileo in 2011-2012 to firstly analyse the existing conditions, and subsequently design a constructed waterway. The existing waterway has been heavily degraded through agricultural practices including vegetation clearance and re-grading. There appears to be no significant riparian vegetation or ecological habitat along the tributary and therefore it was recommended that a constructed waterway replace the existing system.

The main considerations for a constructed waterway running adjacent to a development site are the waterway corridor, design of the constructed waterway, flood levels, and waterway crossings. Stormwater treatment before entering the waterway is discussed in section 6. This process demonstrates that the waterway corridor will be sufficient in conveying flows along the constructed waterway and providing for river health and amenity opportunities in a future urbanised landscape.

5.1 Waterway corridor Waterways, whether natural or constructed, need to have an appropriate waterway corridor or reserve provided adjacent to development in order to accommodate objectives for flood protection, river health, biodiversity and amenity.

A waterway corridor is defined as the waterway channel and its associated riparian zones. The riparian zones consist of two parts (Figure 12):

the vegetated buffer

the core riparian zone

Figure 12. Waterway corridor (Melbourne Water’s Waterway Corridor Guidelines)

Based on the constructed waterway design (see section 5.2), the hydraulic width is 30 m and therefore core riparian zone (CRZ) is 30 m. Based on this design, a 50 m wide waterway corridor was agreed between Phileo, MPA and Melbourne Water as part of the 2011-2012 previous work. This was based on the draft corridor guidelines at the time, which includes a vegetated buffer of 10 m on each side of the CRZ. Shared trail and maintenance track will be included in this zone (see Figure 16).

The final revision of the corridor guidelines includes some minor adjusts to the corridor widths based on the location of active edges Figure 13. The corridor width proposed for the Lollypop Creek tributary is based on the original 2012 agreement with the consideration of maintenance access shown in Figure 16.

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Figure 13. Constructed Waterway corridor requirements (Melbourne Water’s Waterway Corridor Guidelines)

According to Melbourne Water’s Waterway Corridor Guidelines “assigning a waterway corridor preserves areas of the riparian zone that protect or enhance native vegetation, river health and biodiversity, and provide space for recreational infrastructure and activities (e.g. shared paths and (in some cases) stormwater treatment systems”.

A fundamental principle is to provide continuity along the core riparian zone, therefore the strong preference is to locate shared paths and other infrastructure outside of the core riparian zone. However page 13 of the Waterway Corridor Guidelines states that “in some instances, stormwater treatment systems such as constructed wetlands and bio-retention systems may be located within the core riparian zone but should form a relatively small proportion of the area of the core riparian zone so as not to degrade its ecological function”.

The location of the stormwater treatment assets is shown in Figure 21 (section 6). The strategy and concept designs demonstrate that the stormwater treatment systems will not encroach on the CRZ and will form a relatively small proportion of the vegetated buffer, therefore the above principle has been satisfied.

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Figure 14. Waterway corridor

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5.2 Constructed waterway The existing waterway through the site is of very low environmental value. It has a Strahler stream order of 1 and is a tributary of Lollipop Creek.

Existing conditions Based on the existing conditions report (both inspection and hydraulic modelling), the degraded tributary appears to be fairly stable, with no signs of erosion or scour. The channel geometry appears to be shallow and at a flat grade, which indicates that significant flood events will be largely unconfined with floodplain widths varying across the property, reliant on the topography. Two large farm dams, one located immediately upstream of the property boundary and the other located within the Phileo property at the downstream boundary are both located on the unnamed tributary.

It is advised that a constructed waterway be developed to suitably carry developed flows through the waterway corridor, create habitat, and improve channel stability and visual amenity.

Waterway design The alignment of the constructed waterway generally follows the path of the existing waterway. The proposed location of the constructed waterway is provided in Figure 14.

The waterway design ties in to the existing surface at both upstream and downstream extents. This results in a drop of 16.1 m over 2.89 km, creating an average grade of 1 V:180 H. Given there is no bedrock present, the grade suggests that a compound channel should be used and grade control structures may be required dependent on detail design (Melbourne Water Constructed Waterway Manual). The deign grade varies between 1:600 to 1:150 for the downstream 2.6 km, while there is a grade of around 1 in 70 for the upstream section (315 m). This upstream grade may be varied dependent on the Outer Metropolitan Ring Road configuration. The design grade and existing surface are shown in Figure 15.

Figure 15. Long-section for constructed waterway

The low flow channel will convey between a 3month and 1 year ARI event, while the high flow channel has the capacity of the 100 year ARI event. The flows used in the channel design were provided in Table 6, section 3.1. In order to convey these flows and remain within the waterway corridor, a typical cross-section depicted in Figure 16 will be used. Analysis in HEC-RAS ensured the shear stress within the low and high flow channels does not exceed 45 N/ms – the shear resistance of short native grass (Draft Constructed Waterway Manual Part B2) (results summary in Attachment E). This is a conservative value, and with vegetation establishment, the channel could be designed to tolerate greater shear stresses. This waterway will have a hydraulic width of 30 m.

Several roads cross the waterway within the study site. These are discussed in section 5.3.

35

40

45

50

55

60

02004006008001000120014001600180020002200240026002800

Hei

ght

(m, A

HD

)

Chainage (m)

Wetland 1b - Example Cross-section

Design surface

Existing surface

Extended detention depth: 38.3 m

Normal water level: 37.8 m

Access Track(4 m)

1:8

1:8

1:6

Constructed waterway

Sediment pond (depth: 1.5 m)

Wetland(average depth:0.4 m)

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Figure 16. Typical cross-section of constructed waterway

Flood levels The flood levels through the waterway corridor for the 100 year ARI event are depicted in Figure 17 and Figure 20. The major flows are completely contained within the waterway corridor. Areas where fill are required are also marked on the map.

Waterway outfall As described above, the waterway has been designed to tie in with the existing surface level at the downstream end. Therefore any flows will be able to drain via the existing waterway, and large events may sheet flow across the downstream land. There is no engineering constraint on these conditions. Downstream outfall acceptance with the land owner will be presented with the permit application.

35

36

37

38

39

40

41

42

43

44

45

-30 -25 -20 -15 -10 -5 0 5 10 15 20 25 30

Hei

ght (

m, A

HD

)

Chainage (m)

Wetland 1b - Example Cross-section

Design surface

Core Riparian Zone

Existing surface

Extended detention depth: 38.3 m

Normal water level: 37.8 m

Access Track(4 m)

1:8

1:8

1:6

Constructed waterway

Q 10

Sediment pond (depth: 1.5 m)

Wetland(average depth:0.4 m)

Vegetated buffer Vegetated bufferDevelopmentLine

DevelopmentLine

1:5

1:61:6

Access Track Access TrackFill Fill

Q 100

Q 1 year

1:61:6

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Figure 17. Constructed waterway design, with flood levels

SWMS: Daleston 25

5.3 Waterway crossings There are several waterway crossings over the constructed waterway for the study area. As shown on Figure 18, there are six main crossings within the study area. In addition to these crossings, the Outer Metropolitan Ring Road will cross the waterway at the upstream (west) end of the study area, and Greens Road that crosses at the downstream (east) extent of the study area.

Figure 18. Waterway crossings in study area

The crossings vary in length from 16 to 44 m (see Table 9). A standard culvert arrangement has been used for all crossings (Figure 19) that will retain lot and road freeboard requirements. This involves three culverts, all with a span of 3.6 m. The centre culvert will sit within the low flow channel and will have a height of1.5 m, while the outer culverts will sit on the waterway bench, raised around 0.7 m above the low-flow channel, and will therefore be 0.9 m high.

Table 9. Crossing parameters

Crossing ID Chainage (upstream extent) Length (width of road), m

A 2792 26

B 2101 16

C 1846 26

D 1524 16

E 1089 44

F 536 22

SWMS: Daleston 26

Figure 19. Typical culvert arrangement

60 80 100 120 14046.0

46.5

47.0

47.5

48.0

48.5

49.0

des channel 20140829 wCulverts Plan: Plan 02 1/09/2014

Station (m)

Ele

vation

(m

)

Legend

WS 100yr ARI

Ground

Ineff

Bank Sta

SWMS: Daleston 27

Figure 20. Long-section of constructed waterway with crossings

0 500 1000 1500 2000 2500 300036

38

40

42

44

46

48

50

52

54

56

des channel 20140829 wCulverts Plan: Plan 02 1/09/2014

Main Channel Distance (m)

Ele

vation

(m

)

Legend

WS 100yr ARI

Ground

trib 0

SWMS: Daleston 28

6 Proposed stormwater quality treatment system

Based on discussions with MPA working towards the PSP, this strategy includes multiple distributed stormwater treatment assets within the study area and use of an external wetland. For the catchments draining into the waterway (catchments 1-7), treatment will be located along the waterway corridor to treat minor flows through sediment basin treatment as a minimum before they enter the waterway. Catchment 8 will flow to the south east and be treated by a wetland in an adjoining property. This will involve two wetland and seven sediment basin systems within the Phileo land holding (Figure 21). One of the wetlands (asset 7) at the downstream end of the waterway will treat additional flows from the waterway to account for limitations of sediment basin treatment upstream. This is inline with the proposed MW drainage strategy that has been agreed with council.

6.1 Performance against BPEM We understand that a key principle for development is that all stormwater is to be treated to best practice before being discharged to the waterway. The following Best Practice Targets have been adopted:

70% removal of the total Gross Pollutant load

80% removal of total Suspended Solids (TSS)

45% removal of total Nitrogen (TN)

45% removal of total Phosphorus (TP)

The catchments and stormwater treatment train have been modelled using MUSIC. The land use types and corresponding faction imperviousness adopted are presented in Table 10. In accordance with Melbourne Water’s MUSIC Guidelines, Melbourne Airport rainfall station was used with a reference year of 1996. The design treatment system schematic is provided in Figure 22. The results are presented in two forms: the treatment provided by each asset (Table 12), and the overall removal through treatment and load reduction ( Table 11), demonstrating the overall achievement of the strategy to meet best practise.

Table 10. Fraction Impervious (based on Melbourne Water’s MUSIC Guidelines)

Land use type Faction impervious adopted

Residential – average lot size 500 m2 0.7

Schools, Indoor Active Space 0.7

Medium – High density residential 0.8

Activity Centre 0.9

Table 11. Overall treatment train results

Parameter Total

sources Residual

Load Removal achieved

External sources

Internal sources

Removal achieved from study area

Flow (ML/yr) 924 898 26 344 580 4.5 %

Total Suspended Solids (kg/yr) 169,000 57,900 111,100 53,500 115,500 96.2 %

Total Phosphorus (kg/yr) 354 165 189 115 239 79.1 %

Total Nitrogen (kg/yr) 2,610 1,840 770 956 1,654 46.6 %

Gross Pollutants (kg/yr) 33,000 2,930 30,070 7,770 25,230 119.2 %

SWMS: Daleston 29

Figure 21. Location of stormwater treatment assets

SWMS: Daleston 30

Figure 22. MUSIC schematic for treatment assets

SWMS: Daleston 31

Table 12. MUSIC results for each treatment asset

System arrangement System performance (removal)

Asset WSUD Treatment Measure Total Suspended Solids

Total Phosphorous

Total Nitrogen

Gross Pollutant

1a Sediment basin 70.4 % 50.2 % 21.3 % 100 %

1b Sediment basin 66.8 % 49.7 % 23.6 % 100 %

2 Sediment basin 66.3 % 49.1 % 22.6 % 100 %

3 Wetland / Sediment basin 85.3 % 72.4 % 45.2% 100 %

4a Sediment basin 69.1 % 49.7 % 24.1 % 100 %

4b Sediment basin 66.0 % 48.7 % 22.5 % 100 %

5 Sediment basin 68.7 % 51.0 % 24.1 % 100 %

6 Sediment basin 66.5 % 49.2 % 22.7 % 100 %

7 Sediment basin 59.9% 42.6% 18.0% 100%

7 Wetland 37.1% 32.6% 19.6% 100%

Overall 96.2% 79.1% 46.6% 100%

6.2 Treatment asset descriptions This section described the role and components of each asset. Further details of parameters are discussed in section 6.3. Based on the size of the contributing catchments, asset 7 will become a Melbourne Water asset while all remaining treatment assets in the study area will be the property of council. Note that the external wetland treating catchment 8 will be the property of Melbourne Water also. This aligns with the proposed MW drainage strategy that has been agreed with council.

For each asset the normal water level is determined by the subdivision drainage of its local catchment and invert of the waterway that the asset will then drain into. The normal water level must ensure free drainage of the subdivision system into the asset and adequate drainage out of the asset into the waterway. Given the flat terrain, there is a delicate balance here between the drainage either side of the asset.

Wetlands Two wetlands will be located either side of the waterway, at the downstream end of the study area. These wetlands are asset 3 and 7. They will be features of the area as they form the main entry to the development. Concept designs of the wetlands are provided in Appendix A.

Asset 3 will treat the runoff from catchment 3, immediately before it enters the waterway. In order to allow free drainage of the catchment, the normal water level must be set at 37.8 m. This sits the wetland down into the waterway corridor, however an embankment between the asset and the wetland will provide protection from 10 year ARI flows.

Asset 7 will consist of a sediment basin which collects flows from the local catchment, and a wetland which treats both the local catchment and a diversion from the waterway. This allows this asset to compensate for some under treatment further upstream (i.e. from the sediment basins). The wetland will have a normal water level of 37.8 m, and therefore will be at a similar level to the waterway. The wetland will be protected from the waterway by a 10 year embankment. A diversion from the waterway will ensure a maximum peak flow through the wetland of 1.0 m

3/s, which optimises the wetland performance. This is less than the three month

flow of the waterway (1.2 m3/s).

Sediment Basins Assets 1a, 1b, 2, 4a, 4b, 5 and 6 will consist of sediment basins. The assets are located adjacent to the waterway corridor. Full treatment is not provided here prior to entering the waterway as and agreemtn with MW has indicated bioretention systems are not acceptable assets for council. Further treatment is provided

SWMS: Daleston 32

downstream at asset 7. The treatment includes a TSS removal of around 65% before discharging to the waterway.

At some locations, there is limited drop between the normal water level and the invert of the waterway. The sediment pond will be able to drain freely into the waterway. In the case where the waterway is full, water may backflow up the pipe, however the sediment pond will likely be full and the head difference will prevent any flow into the sediment basin. This backflow would be relatively slow and no damage would occur.

Table 13. Wetland footprint areas

Asset Catchment Area

Normal Water Level

Wetland treatment Area

Sediment Basin

Total Treatment area

Total footprint

1a 18 ha 47.0 m - 400 m2 400 m

2 2,000 m

2

1b 35.1 ha 45.2 m - 1,000 m2 1,000 m

2 3,200 m

2

2 18.7 ha 43.1 m - 400 m2 400 m

2 1,950 m

2

3 15.8 ha 37.8 m 2,000 m2 300 m

2 2,300 m

2 8,000 m

2

4a 20.6 ha 48.2 m - 600 m2 600 m

2 2,500 m

2

4b 18.6 ha 46.9 m* - 500 m2 500 m

2 2,200 m

2

5 16.8 ha 45.6 m* - 500 m2 500 m

2 1,750 m

2

6 15.4 ha 41.6 m - 400 m2 400 m

2 2,150 m

2

7 28.3 ha 37.8 m 16,000 m2 500 m

2 16,500 m

2 31,000 m

2

*Note – Fill required in this location for pipe cover.

6.3 Treatment asset parameters The batter slopes have been designed at 1 in 8 around the assets to allow for provision of shared path and maintenance tracks where necessary. It is assumed that at 0.35 m below the normal water level, the batter slope can increase to 1:3 therefore allowing a minimum with of 12.5 m, whilst still accommodating for deep open water zones in the wetland and sediment basins.

All treatment assets are located adjacent to the waterway. The normal water level of the assets has been located entirely outside the waterway corridor, while the batters will link with the constructed waterway earthworks within the vegetated buffer, but outside of the core riparian zone.

Provision has been made for maintenance requirements. As described above, the asset designs allow for a maintenance track, these would typically be 4 m wide at a grade of 1:20. Provision for sediment dewatering has also been made. These areas assume a depth of 500 mm and allow for the 5 year cleanout sediment volume to be accommodated. These calculations are based on the typical sediment loading rate of 1.6 m

3/ha/yr for a developed catchment. The possible locations of these dewatering areas are provided in

Attachment A and B. Calculations for sediment basin capture efficiency and storage volume are provided in Attachment D.

The assets are located offline and will collect water from the contributing catchment then discharge to the waterway. The five year ARI flow from the stormwater pipe will feed into the sediment basins. From there, the sediment basins will provide the wetland with approximately a three-month discharge, with any additional flow overflowing to the Creek (see Appendix A). This allows the sediment basin to protect the wetland from large flows, while treating as much inflow as possible. The freeboard provided above the extended detention is 0.3 m, which will allow the sediment basin to pass any 5 year flows over without entering the wetland. The major 100 year flows are routed around the wetlands, to avoid disturbance (see Figure 11). Treatment asset parameters used in MUSIC are provided in Table 14.

SWMS: Daleston 33

Velocity calculations for the wetland and sediment ponds are provided in Attachment D.

Table 14. Treatment asset parameters

Wetland Sediment Basin

Average depth, m 0.4 1.5

Extended detention, m 0.5 0.5

Freeboard (m) 0.3

Extended detention time (hours) 72 12

SWMS: Daleston 34

7 Stormwater harvesting

This section responds to a request from the MPA to consider the stormwater harvesting opportunities within the Daleston study site.

This options assessment is consistent with themes expressed by the MPA to identify whole of water cycle management (WOWC) opportunities. WOWC opportunities aim to improve the liveability and environmental outcomes from development. Examples of WOWC opportunities include the co-location of surface water management infrastructure to improve amenity and the utility of encumbered spaces as well as opportunities to use treated stormwater for the irrigation of nearby active open spaces.

Assumptions For the purposes of conceptualising a stormwater harvesting system the following process assumptions were adopted (refer to Figure 23):

catchment stormwater enters a sediment basin removing larger pollutants prior to entering a wetland for further physical and biological treatment,

from the wetland, treated stormwater enters a storage basin, underground storage or storage tank, where further settling and sedimentation occurs, and

stormwater is then pumped from the storage, through a coarse filter and UV disinfection unit to a header tank or distribution outlet for irrigation.

Figure 23. Stormwater harvesting and reuse schematic

Opportunities A desktop review of the study area identified three potential locations where stormwater harvesting schemes for the irrigation of nearby active open spaces could be located. A summary of this review is provided in Table 15 and is shown in Figure 24.

Table 15. Location of stormwater harvesting opportunities (refer to Figure 24)

Option Stormwater harvesting location

Potential reuse options Distance between harvesting location and active open space (approx.)

1

Stormwater treatment wetland (Asset 7)

School - east 220 m

2 Sporting reserve - east 520 m

3 Sporting reserve - west 2,100 m

4 Schools - west 1,400 – 1,700 m

SWMS: Daleston 35

Figure 24. Stormwater harvesting opportunities

Water balance analysis The stormwater treatment wetland (asset 7) receives water from all the upstream catchments (aside from catchment 3), which is approximately 766 ML per year. Some of this incoming flow either bypasses the wetland or overflows via the wetland weir overflow, while there is also some evapotranspiration from the wetland area. 335 ML/ year is treated by the wetland and exits via the outlet pipe (Figure 25). This water has been assumed to be available for stormwater reuse.

Figure 25. Daleston stormwater harvesting water balance

Wetland (Asset 7)766 ML /yr

Treated water available for

reuse

Bypass and overflow into

waterway

Study area and upstream catchment

21

ML

/yr

Evapotranspiration

SWMS: Daleston 36

Given the available water and the opportunities outlined above, the possibility of stormwater harvesting and reuse have been analysed below using the Clearwater methodology to determine the likely irrigation demands associated with open space and MUSIC modelling software to determine the system’s water balance on a 6-minute time step. The irrigation demand requirements are provided in Table 16. It is assumed that 20% of school areas would be active open space.

Table 16. Irrigation demand

Option Area (ha) Land type Demand Annual demand

1 7.4 ha Active 4.5 ML /ha /year 33.2 ML /year

2 0.7 ha Active 4.5 ML /ha /year 3.2 ML / year

3 8.3 ha Active 4.5 ML /ha /year 37.4 ML /year

4 2.6 ha Active 4.5 ML /ha /year 11.7 ML /year

Various storage volumes were modelled to estimate the reliability of the system when considering the irrigation demand (i.e. how much of the annual demand can be provided by stormwater). The results are presented in Table 17. The storages were modelled assuming storage ponds had a depth of 1.5 m and allowing for evapotranspiration, as a conservative approach.

The use of stormwater for irrigation purposes is subject to the seasonality of the water supply and demand, for example in summer generally more water is required for irrigation due to greater evapotranspiration, and less stormwater would be generated throughout the catchment. Using the tank sizes outlined below would allow for adequate storage to buffer these seasonality issues and achieve 90% reliability over the year.

Table 17. Stormwater reuse reliability

Option Annual Demand Storage volume Reliability

1 33.2 ML 2,000 m3 90 %

1, 2 36.5 ML 2,500 m3 92 %

1, 2, 3 73.8 ML 5, 500 m3 92 %

1,2, 3, 4 85.5 ML 6, 500 m3 90 %

Options assessment The analysis outlined above demonstrates that there is an abundance of treated stormwater that could be harvested and reused. The analysis has focused on a low-cost stormwater harvesting system reusing water for irrigation purposes.

Option 1 and 2 are located close to this water source and are therefore likely to be a feasible option for stormwater harvesting. Option 3 is significantly further away from the water source and there would be significant costs associated with pumping and extensive pipe networks.

SWMS: Daleston 37

8 Development Services Scheme Assets Required

8.1 Required assets The above strategies have outlined the assets required to deal with the quality and quantity issues associated with stormwater in Phileo’s Daleston site. A summary of the development Services Scheme assets required is shown in Table 18.

Table 18. Development Services Scheme assets

Asset type Description Size Responsibility

Pipe network Minor flows pipe network for internal catchments (1c to 8b)

Varies, up to 1200 mm City of Wyndham

Pipe network at south-east end of catchment (8c west of Westbrook drive)

Approx. 1500 mm City of Wyndham

Pipe network at south-east end of catchment (8c east of Westbrook drive)

Approx. 1500 mm Melbourne Water

Waterway Constructed waterway (tributary of Lollipop Creek)

- Melbourne Water

Road crossings

Seven crossings (16-44 m in length)

- 3 culverts per crossing

Central culvert: 3.6 x 1.2 m

Two culverts adjacent to central culvert: 3.6 x 0.9m

Melbourne Water responsible for the hydraulic function.

Council /VicRoads responsible for the road.

Stormwater Treatment

1a - Sediment basin 400 m2 City of Wyndham

1b - Sediment basin 1,000 m2 City of Wyndham

2 - Sediment basin 400 m2 City of Wyndham

3 - Wetland / Sediment basin 2,300 m2 City of Wyndham

4a - Sediment basin 600 m2 City of Wyndham

4b - Sediment basin 500 m2 City of Wyndham

5 - Sediment basin 500 m2 City of Wyndham

6 - Sediment basin 400 m2 City of Wyndham

7 - Wetland / Sediment basin 16,500 m2 Melbourne Water

8.2 Timing of assets Staging of works will occur in the northern catchment first in east to west direction. Works in stage 1 will trigger works on water quality assets 3 and asset 7. At first asset 7 could be established to operate with the inflow from the sediment basin only, and then be developed to take flows from the waterway once further development commences upstream.

The constructed waterway will also need to be staged with development with temporary rock beaching works to a suitable design standard undertaken at the top of excavated section to ensure flows are safely transitioned into the waterway.

The sediment basins will be built progressively along the waterway as development moves upstream. Catchment 8 will be the last to be developed as it relies on external assets. Dependent on the timing of development on the property to the southeast temporary works may be used as required to ensure compliance with water quality and outfall standards.

Discharge at both of the eastern and south-eastern outlets of the property will require written agreements with landholders impacted prior to works.

SWMS: Daleston 38

9 Conclusion

This SWMS has proposed management strategies for stormwater quantity, stormwater quality, and a constructed waterway. Through meeting these objectives, this SWMS acts as a critical component of the development servicing strategy and ensures storm water is managed in accordance with Melbourne Water’s requirements.

Based on the hydrologic analysis for the catchment, no flood storage assets are required in the northern catchment, with the southern catchment draining to the MW DSS retarding basin. The minor flows will be managed by a local piped system, while the major flows will be managed by road reserves and the constructed waterway. The constructed waterway will have a 30 m core riparian zone and an overall waterway width of 50m that provides provision for maintenance access.

Two wetlands systems and seven additional sediment basins are required along the waterway corridor (within the Daleston property) to treat flows before they enter the waterway. These have been sized to treat the 187 ha catchment which flows into the waterway to best practice requirements. Catchment 8 will flow to the south-east and will be treated by a wetland external to the study area as per the MW DSS.

This strategy is inline with the draft PSP 42.1, previous work undertaken and proposed MW drainage strategy that has been agreed with council.

SWMS: Daleston 39

Attachment A Wetland Concept design

SWMS: Daleston 40

Asset 3 and asset 7 plan view

Figure 26. Plan view for Asset 3 and asset 7

SWMS: Daleston 41

Asset 3 section view

Figure 27. Cross-section AA

35

36

37

38

39

40

41

42

43

44

45

0 10 20 30 40 50 60 70 80

Hei

ght

(m, A

HD

)

Chainage (m)

Wetland 3 - Example Cross-section

Design surface

Core Riparian Zone

Existing surface

Extended detention depth: 38.3 m

Normal water level: 37.8 mAccess Track(1:20, 4 m)

1:8

1:6

1:6

Constructed wtaerway

Q 10Access Track(1:20, 4 m)

1:8

SWMS: Daleston 42

Asset 7 section view

Figure 28. Cross-section BB

35

36

37

38

39

40

41

42

43

44

45

0 50 100 150 200 250

Hei

ght

(m, A

HD

)

Chainage (m)

Wetland 1b - Example Cross-section

Design surface

Core Riparain Zone

Existing surface

Extended detention depth: 38.3 m

Normal water level: 37.8 m

Access Track(4 m)

1:81:8

1:6

Constructed waterway

Q 10

Sediment pond (depth: 1.5 m)

Wetland(average depth: 0.4 m)

SWMS: Daleston 43

Figure 29. Cross-section CC

35

36

37

38

39

40

41

42

43

44

45

0 50 100 150 200 250

Hei

ght

(m, A

HD

)

Chainage (m)

Wetland 1b - Example Cross-section

Design surface

Road Reserve

Existing surface

Extended detention depth: 38.3 m

Normal water level: 37.8 m

Access Track(1:20, 4 m)

1:6

1:8

1:6

SWMS: Daleston 44

Attachment B Sediment basin concept design

SWMS: Daleston 45

Sediment basins plan view

Figure 30. Plan view for Assets1b, 4a, and 4b

SWMS: Daleston 46

Figure 31. Plan view for Asset 1a, 2, 5, and 6

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Sediment basins typical section view

Figure 32. Typical section view for Assets 1a, 1b, 2, 4a, 4b, 5, 6

45

46

47

48

49

50

51

52

53

54

55

0 10 20 30 40 50 60 70 80 90 100 110

Hei

ght

(m, A

HD

)

Chainage (m)

Typical Sed basin Cross-section

Design surface

Existing surface

Extended detention depth

Normal water level

Access Track(4 m)

1:8batter varies between1:6 - 1:8

Core Riparian Zone

Constructed waterway

1:3

1:8

1.5 m

0.5 m

Road Reserve

SWMS: Daleston 48

Attachment C Rational Calculations

SWMS: Daleston 49

Rational calculations

For the flows provided in Table 5, Table 7, and Table 8 the rational method has been adopted. The calculations made are presented here.

Table 19. Daleston rational calculations

Treatment asset (minor) catchments Overland flow catchments

Sub catchment: 1a 1b 2 3 4a 4b 5 6 7 8a 8b 8c 1 4 7a 7b

Parameter Catchment area, ha 18.2 34.8 18.7 16.4 20.6 18.6 16.8 15.4 27.5 4.3 30.3 66.2 53 39.2 13.8 13.7

Fraction impervious 0.6 0.63 0.62 0.62 0.60 0.65 0.67 0.65 0.6 0.6 0.6 0.6 0.62 0.62 0.6 0.6

Length, m 976 1267 816 763 620 730 700 660 1060 300 930 1620 1500 1084 670 600

Drop, m 7 8 6 9 6 3.5 6 6 5 2.5 12 20 11 7.5 5 3

Slope m/m 0.007 0.006 0.007 0.012 0.010 0.005 0.009 0.009 0.005 0.008 0.013 0.012 0.007 0.007 0.007 0.005

Average pipe diameter, mm

600 600 600 600 600 600 600 600 600 600 600 600 600 600 600 600

Velocity, m/s 1.8 1.7 1.9 2.4 2.1 1.5 2.0 2.1 1.5 2.0 2.5 2.4 1.9 1.8 1.9 1.5

Time of concentration, min

14.8 18.2 13.3 11.4 10.8 14.1 11.8 11.3 17.8 8.5 12.3 17.2 19.4 16.0 12.0 12.5

Intensity, mm/hr

I 1 year 29.2 26.0 30.6 32.4 32.9 29.9 32.0 32.5 26.4 36.6 31.6 27.0 24.9 28.1 31.9 31.4

I 5 year 54.1 48.0 56.9 60.4 61.4 55.5 59.6 60.5 48.7 68.5 58.8 49.9 45.8 52.0 59.4 58.4

I 100 year 115.9 101.9 122.3 130.2 132.5 119.1 128.5 130.6 103.5 148.9 126.5 106.2 96.9 111.2 127.9 125.6

Discharge, m

3/s

Q 1 year 0.83 1.42 0.90 0.83 1.06 0.87 0.84 0.78 1.14 0.25 1.50 2.80 2.07 1.73 0.69 0.67

Q 5 year 1.55 2.62 1.67 1.55 1.98 1.62 1.57 1.46 2.10 0.46 2.79 5.18 3.81 3.20 1.28 1.25

Q 100 year 3.31 5.56 3.59 3.38 4.29 3.47 3.39 3.15 4.57 1.00 6.01 11.03 8.06 6.83 2.77 2.70

SWMS: Daleston 50

Attachment D Treatment asset calculations

SWMS: Daleston 51

Sediment Pond analysis

Sediment ponds for all assets have been sized to ensure a capture efficiency greater than 95% for the 3 month flow and provide adequate sediment storage. The procedure outlined in WSUD Engineering Procedures 2005 has been followed.

Table 20. Daleston sediment pond calculations

Parameter Asset 1a Asset 1b Asset 2 Asset 3 Asset 4a Asset 4b Asset 5 Asset 6 Asset 7

Conditions Contributing catchment (ha) 18.0 35.1 18.7 16.4 20.6 18.6 16.8 15.4 27.5

Area of Basin (m2) 400 1000 400 300 600 500 500 400 500

Capture Efficiency

Settling Velocity of Target Sediment (mm/s)

[Particle size 125 μm]

11 11 11 11 11 11 11 11 11

Hydraulic Efficiency (λ) 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4

Permanent Pool Depth, dp (m) 1.5 1.5 1 1.5 1.5 1 1.5 1.5 1

Extended detention depth, de 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5

Number of CSTR's, n [From hydraulic efficiency] 1.67 1.67 1.67 1.67 1.67 1.67 1.67 1.67 1.67

Depth below permanent pool that is sufficient to retain sediment, d* (m)

1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5

Design Discharge (m3/s)

[Q 3 month]

0.306 0.528 0.334 0.310 0.397 0.324 0.314 0.292 0.420

Capture Efficiency 99% 98% 97% 97% 98% 98% 98% 98% 97%

Check ( > 95%) OK OK OK OK OK OK OK OK OK

Sediment storage

Sediment Loading Rate, Lo (m3/ha/yr) 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.6

Desired clean-out frequency, Fr 5 years 5 years 5 years 5 years 5 years 5 years 5 years 5 years 5 years

Storage volume required, St 141 277 146 127 162 146 132 120 214

Available sediment storage volume 300 750 300 225 450 375 375 300 375

Check (Available storage > required storage) Ok Ok Ok Ok Ok Ok Ok Ok Ok

Sediment dewatering

Depth for dewatering area (m) 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5

Area required for dewatering (m2) 281 554 291 253 324 292 264 241 428

SWMS: Daleston 52

Velocity Calculations

The velocity through each treatment asset is considered here. For these assets the 100 year overland flow from the catchments is diverted around the wetland. A flow depth of 0.5 m, which is the extended detention depth, has been assumed for all flows, which is a conservative approach (as a calculated smaller flow area will result in higher calculated velocities).

A manual calculation has been used to check the flow velocities through the assets for the concept design. This calculates the flow area from the flow depth (between the extended detention depth and normal water level) and the average width in that area. The average width is determined from the narrowest part of the macrophyte zone or sediment basin. Table 21 shows the calculations for the wetland systems (asset 3 and 7), while Table 22 provides the results for the remaining sediment basins.

Table 21. Velocity calculation – Wetlands

Asset 3 Asset 7

Parameter Q 3 month Q 1 year Q 5 year Q 3 month Q 1 year Q 5 year

Flow conditions Design Flow (m3/s) 0.30 0.80 1.5 0.42 1.20 2.10

Flow depth (m) 0.5 0.5 0.5 0.6 0.5 0.7

Sediment pond Width at NWL (m) 13 13 13 13 13 13

Width at EDD (m) 20 20 20 21 21 21

Average width (m) 16.5 16.5 16.5 17.0 17.0 17.0

Flow Area (m2) 8.3 8.3 8.3 10.2 8.5 11.9

Flow Velocity (m/s) 0.04 0.10 0.18 0.04 0.13 0.18

Check < 0.5 OK < 0.5 OK < 0.5 OK < 0.5 OK < 0.5 OK < 0.5 OK

Macrophyte zone

Width at NWL (m) 21 24 24 25 25 25

Width at EDD (m) 29 32 32 33 33 33

Average width (m) 28 28 28 29 29 29

Flow Area (m2) 14 14 14 17 15 20

Flow Velocity (m/s) 0.02 0.07 0.12 0.024 0.08 0.10

Check < 0.05 OK < 0.5 OK < 0.5 OK < 0.05 OK < 0.5 OK < 0.5 OK

SWMS: Daleston 53

Table 22. Velocity calculation – sediment ponds

Parameter Asset 1a Asset 1b Asset 2 Asset 4a Asset 4b Asset 5 Asset 6

Flow conditions

Design Flow -3 month (m3/s) 1.53 2.64 1.67 1.98 1.62 1.57 1.46

Design Flow -1 year (m3/s) 0.83 1.43 0.90 1.06 0.87 0.84 0.78

Design Flow -5 year (m3/s) 0.31 0.53 0.33 0.40 0.32 0.31 0.29

Flow depth (m) 0.5 0.5 0.5 0.5 0.5 0.5 0.5

Sediment pond

Width at NWL (m) 12.5 12.5 12.5 12.5 12.5 12.5 12.5

Width at EDD (m) 20.5 20.5 20.5 20.5 20.5 20.5 20.5

Average width (m) 16.5 16.5 16.5 16.5 16.5 16.5 16.5

Flow Area (m2) 8.3 8.3 8.3 8.3 8.3 8.3 8.3

Flow Velocity – 3 month (m/s) 0.04 0.06 0.04 0.05 0.04 0.04 0.04

Flow Velocity – 1 year (m/s) 0.10 0.17 0.11 0.13 0.11 0.10 0.09

Flow Velocity – 5 year (m/s) 0.19 0.32 0.20 0.24 0.20 0.19 0.18

Check All < 0.5 OK All < 0.5 OK All < 0.5 OK All < 0.5 OK All < 0.5 OK All < 0.5 OK All < 0.5 OK

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Attachment E Constructed waterway design

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Hydraulic parameters

The constructed waterway design has been analysed using HEC-RAS. The results of this hydraulic analysis are provided here.

Table 23. Constructed waterway hydraulic parameters

Parameter Q 2 year Q 10 year Q 100 year

Average velocity, m/s 0.76 0.92 1.10

Average depth, m 0.94 1.23 1.61

Average shear stress, N/ms 15.86 22.91 31.00

Average stream power, N/m2 14.51 23.65 38.47

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Attachment F RORB sub-catchments

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Figure 33. RORB sub-catchments