Foul Drainage Strategy Mitford Estate LLP Proposed...

Foul Drainage Strategy

WYG Engineering part of the WYG Group creative minds safe hands

www.wyg.com

Mitford Estate LLP

Proposed Development on Land West of Lancaster

Park, Morpeth, Northumberland


March 2015 Matthew Elliott


WYG Engineering part of the WYG Group creative minds safe hands

www.wyg.com

Report Control

REPORT

CONTROLDocume

Foul Drainage Strategy (FDS)

Project: Proposed Development on Land West of Lancaster Park, Morpeth, Northumbria

Client:

Mitford Estate LLP

Job Number: A090801

File Origin: N:\Projects\A090001-A095000\A090801\reports\FRA\Land west of

Lancaster Park Morpeth FRDA text.doc

Document Checking:

Primary Author Matthew Elliott Initialled:

Contributor Simbi Hatchard Initialled:

Review By Tom Beavis Initialled:

Issue Date Status Checked for Issue

1 03/03/2015 First Issue

2

3

4


WYG Engineering part of the WYG Group creative minds safe hands Proposed Development on Land West of Lancaster Park, Morpeth, Northumberland – Foul Drainage Strategy March 2015

1

Contents

1 INTRODUCTION ............................................................................................................................. 1

1.1 PURPOSE OF THE REPORT .................................................................................................. 1 1.2 PROPOSED DEVELOPMENT .................................................................................................. 1 1.3 REQUIREMENT FOR A FOUL DRAINAGE STRATEGY .............................................................. 1 1.4 STRUCTURE OF FOUL DRAINAGE STRATEGY ........................................................................ 2

2 SITE DESCRIPTION ......................................................................................................................... 3

2.1 EXISTING SITE ................................................................................................................... 3 2.2 DEVELOPMENT PROPOSALS ................................................................................................ 6 2.3 EXISTING FOUL DRAINAGE INFRASTRUCTURE IN LOCALITY ................................................ 7 2.4 STUDIES IN RESPECT OF FOUL DRAINAGE INFRASTRUCTURE .............................................. 8 2.5 CONSENTED DEVELOPMENT IN LOCALITY ........................................................................... 9 2.6 CONSULTATIONS .............................................................................................................. 10

3 FOUL DRAINAGE: PLANNING POLICY AND LEGISLATION ................................................................ 12

3.1 INTRODUCTION ................................................................................................................ 12 3.2 NPPF AND PPG.................................................................................................................. 12 3.3 LOCAL PLANNING POLICIES .............................................................................................. 13 3.4 WATER INDUSTRY REGULATION AND LEGISLATION .......................................................... 13 3.5 ENVIRONMEMTAL PERMITS AND DISCHARGE CONSENTS ................................................... 14 3.6 CONCLUSIONS .................................................................................................................. 16

4 PROPOSED STRATEGY .................................................................................................................. 17

4.1 INTRODUCTION ................................................................................................................ 17 4.2 DISCUSSION OF OPTIONS ................................................................................................. 18

5 CONCLUSIONS ............................................................................................................................. 21

APPENDICES

Appendix A - Indicative Masterplan (with Indicative FDS) Appendix B - Excerpts from NCC WCS

Appendix C - Liaison with NWL

Appendix D - Liaison with the EA Appendix E - RBMP and RBMP 2015 Consultation Excerpts



1

1 INTRODUCTION

1.1 PURPOSE OF THE REPORT

Mitford Estate LLP has commissioned WYG Engineering Ltd to prepare a Foul Drainage Strategy (FDS) in

respect of a proposed development on land west of Lancaster Park, Morpeth.

This report has been prepared to accompany an outline planning application for a 36.6ha development

comprising a Trunk Road Service Area (TRSA), residential units and a country park and other community

facilities. These are shown on the Indicative Masterplan contained within Appendix A.

1.2 PROPOSED DEVELOPMENT

The land which will accommodate the proposed site will be provided with access on completion of the

proposed Morpeth Northern Bypass, which is planned to become operational by 2016. The TRSA is intended

to provide services to users of the A1. More precisely, the development comprises of 280 residential units

plus the TRSA which comprises 400m2 mixed use (commercial at ground floor with 12 apartments above); a

hotel class C1 of around 60 bedrooms; a 550m2 restaurant and pub adjacent to the hotel; a fuel station

with 100m2 A1 retail floor space and a 1450 m2 amenity building. The proposed development also includes a

country park and indicative supporting infrastructure including a waste water treatment plant. The country

park and community facilities aim to accommodate informal recreational activities, public art, ongoing

farming practises, and creating enhanced ecological and landscape features.

The development is to be located on land generally comprised of undeveloped open fields used for

agricultural purposes.

1.3 REQUIREMENT FOR A FOUL DRAINAGE STRATEGY

Typically, it is necessary to limit foul drainage strategy considerations at the outline planning stage to

determining reasonably available points of connection to public foul or combined sewers (mains drainage).

However, the situation in North Morpeth is complex due to the inadequacy of the existing foul sewer system

in this area, the extent of already consented development which is to rely on individual site based treatment

systems, the opportunity afforded by the approved bypass to use this as a route for the construction of new

foul drainage infrastructure and the relationship of all of the above to current planning and water sector

legislation.



2

1.4 STRUCTURE OF FOUL DRAINAGE STRATEGY

This report is structured as follows. Section 2 sets out the context of the development with a description of

the site and the effluent flows that will be generated by the development; existing studies in relation to foul

drainage in Morpeth are then considered along with a review of existing consented development in the area.

The outcome of consultation with statutory consultees is then provided. Section 3 set out the planning and

water sector legislation relevant to the application and Section 4 sets out the proposed strategy for

providing foul drainage bearing in mind the specific circumstances of the site and the need for the most

reasonable approach that is compliant with planning policy and water industry legislation. Overall

conclusions are set out in Section 5.



3

2 SITE DESCRIPTION

2.1 EXISTING SITE

The application site covers an area of approximately 36.6 ha and lies west of the Lancaster Park

development, Morpeth, Northumberland, as shown in Figure 1 and Figure 2 below. An inspection of

Northumbrian Water public sewer record plans together with a subsequent inspection of the site to view

available adjacent infrastructure was undertaken on 8th January 2015.

Figure 1 – Site Location1

Site Location



4

Figure 2 – Site Plan

The application site is currently made up of undeveloped open fields used for agricultural purposes.

The application site is bounded by the A1 to the west, with the village of Mitford beyond. Part of its southern

boundary is bounded by the B6343, and part is bounded by undeveloped greenfield land. Beyond the

southern boundary lies the River Wansbeck. The ordinary watercourse Scotch Gill forms the eastern

boundary, beyond which is the Lancaster Park residential development. To the north lies undeveloped

greenfield land. The proposed Morpeth Northern Bypass will run past the northwest of the site.

Surface water falling onto the site all drains into the North Sea via the River Wansbeck. However, the site

can be divided into three catchments which are distinguished by the route by which any water falling onto

and flowing across the surface of the ground would reach the River Wansbeck. The far north of the site,

Site Location

Site Location



5

which is to form the TRSA, drains under the A1 and into Benridge Burn, which then drains into the River

Wansbeck via Mitford Dean joining the Wansbeck just upstream of Mitford. The remainder of the northern

section of the site drains into a watercourse which runs down the eastern boundary of the site and is named

Scotch Gill. Scotch Gill is in a wooded steep-sided ravine which has eroded into the more or less level land

on either side. Scotch Gill enters the Wansbeck opposite Abbey Mills Farm. There are several small

tributaries extending westwards into the site from Scotch Gill. The remainder of the site slopes down

towards the River Wansbeck.

The land along the western boundary is a bank which falls sharply towards to the A1 from an average level

of 69.10m AOD to a level of 61.80m AOD (along the section of bank surveyed) along the A1. The highest

point of the site is in the northwest of the site with a level of 69.37m AOD and the lowest point of the site is

in the southeast corner of the site at a level of 33.62m AOD. The directions in which the land falls and the

high and low points are shown in Figure 3 below.

According to flood risk mapping provided by the EA, the site is located entirely within Flood Zone 1: i.e. land

assessed as having a less than 1 in 1,000 annual probability of river or sea flooding (<0.1% Annual

Exceedance Probability (AEP)), in any one year.



6

Figure 3 – Direction of Surface Water Flows

2.2 DEVELOPMENT PROPOSALS

2.2.1 Development Proposals: Description

The proposed development is to consist of 280 residential units; 400m2 mixed use (commercial at ground

floor with 12 apartments above); a hotel class C1 of around 60 bedrooms; a 550m2 restaurant and pub

adjacent to the hotel; a fuel station with 100m2 A1 retail floor space and a 1450 m2 amenity building. It will

also include a country park and indicative supporting infrastructure including a waste water treatment plant.

The country park and community facilities aim to accommodate informal recreational activities, public art,

ongoing farming practises, and creating enhanced ecological and landscape features. The development

proposals are shown on the Indicative Masterplan contained within Appendix A.

Key

Site Boundary

Surface Water flow direction

Catchment Boundaries

33.62m AOD

69.37m AOD

Part of the upstream catchment

of Benridge Burn / Mitford Dean

Part of the upstream catchment

of Scotch Gill

Direct run off to

River Wansbeck



7

2.2.2 Development Proposals: Foul Drainage

The flows generated by a new development are calculated by two distinct methods depending on whether

the calculation is to support the design of the sewer network (conveyance) or the design of a wastewater

treatment facility (treatment). Inasmuch as the proposed development has primarily two distinct elements

(the TRSA and the remaining residential areas) the design flows attributable to these two elements are also

distinguished below.

In terms of conveyance, it is proposed that the primary foul only systems are built to adoptable standards

and therefore the key design document is Sewers for Adoption (SfA) (6th or 7th Edition). Using SfA the

approximate conveyance design flows generated are as set out in the table below:

Development Element Foul Flow (conveyance) (l/s)

TRSA (2.6 Ha) 10 (Preliminary Estimate)

280 Resi Units 12.5

In terms of treatment volumes the EA consenting regime (which is discussed in more detail below) requires

that these be calculated using ‘Flows and Loads 4- Sizing Criteria, Treatment Capacity for Sewage Treatment

Systems’ published by British Water (ISBN: 978-1-903481-10-03). Full calculations in respect of the above

will be provided with the discharge consent application.

2.3 EXISTING FOUL DRAINAGE INFRASTRUCTURE IN LOCALITY

2.3.1 Sewers

Northumbrian Water Sewers

Inspection of Northumbrian Water Limited (NWL) sewer records identified that the nearest foul sewer is a

150 mm diameter foul sewer located within the adjacent Lancaster Park development which drains to the

Morpeth Wastewater Treatment Works. There are also public surface water sewers in the Lancaster Park

Development. NWL have stated that the system in Lancaster Park is unable to receive any additional foul or

surface water discharges.



8

2.3.2 Wastewater Treatment

Northumbrian Water Wastewater Treatment Works

There are two NWL wastewater treatment works (WwTW) that could conceivably treat effluent from the

development proposals. The Morpeth WwTW is located to the east of Morpeth and the treated effluent

discharges into the River Wansbeck. NWL have indicated that there is currently capacity to accept flows

from the site for treatment and that build out rates are unlikely to outstrip any enlargement measures

necessary to keep pace with wider development within the catchment.

NWL have a small treatment plant serving the rural community of Mitford. This also discharges treated

effluent into the River Wansbeck. NWL have indicated that this is a small facility and is unable to accept the

flows from the proposed development.

2.4 STUDIES IN RESPECT OF FOUL DRAINAGE INFRASTRUCTURE

In conjunction with preparation of the FRA, the NCC Strategic Flood Risk Assessment (SFRA) has been

consulted. The SFRA identifies that the site is within an area with a high incidence of sewer flooding, and

indicated that Morpeth experience issues with sewer flooding. However as the site is currently undeveloped

and not connected to the sewer network sewer flooding at the site is not an issue requiring further

consideration.

A Water Cycle Study (WCS) is a strategic planning document that considers the potential constraints to new

development arising from existing water infrastructure and specific water cycle consequences that might

arise from premature development. Excerpts of the WCS are provided in Appendix B.

The NCC WCS (published May 2012) currently states the following in relation to Morpeth:

‘Wasterwater- NWL have confirmed that Morpeth WwTW currently has no headroom to serve new

development within Morpeth. Although there is potential to extend Morpeth WwTW (in relation to consents),

there are currently issues with land purchase which may prevent any extension. If the land purchase issues

cannot be resolved, then this will have major implications for future development within Morpeth and the

parts of the Castel Morpeth area that would drain to Morpeth WwTW – essentially preventing short term

development.

Sewer- information provided by NWL has confirmed that areas in south east/west Morpeth are currently at

risk of sewer flooding indicating that there may be limited capacity in the network in these areas of Morpeth.



9

However, more recent consultations with NWL (see below) indicate that the problems at the Morpeth

WwTW have now been resolved although it now emerges that there are sewer capacity issues in North

Morpeth.

Currently NWL and NCC have been considering how foul drainage provision for North Morpeth might be

provided in conjunction with the approved Morpeth Bypass. These proposals are discussed in more detail in

Section 2.6.1.below.

2.5 CONSENTED DEVELOPMENT IN LOCALITY

A relevant consideration to this foul strategy is the number of consented developments in the locality.

The following developments in North Morpeth benefit from a Planning Consent:

• 13/02105/OUT- Outline Planning Application for the proposed development of approximately 255

residential units on land to the south west of Northgate Hospital. The foul drainage strategy for the

development is for on-site treatment by package treatment plant which will discharge to Cotting

Burn

• 14/02318/REM- Reserved matters application for planning permission 11/01439/FUL for access,

appearance, landscaping, layout and scale for residential development at Northgate Hospital. Foul

drainage is to be by discharge to the upgraded existing hospital private WwTW which discharges

into Cotting Burn

• 14/02750/FUL-Hybrid Planning Application; Full planning permission sought for demolition of

existing St George’s Hospital buildings and development of 119 new dwellings; Outline permission

sought for phased redevelopment of site for up to 256 new residential units. Foul drainage can

connect to existing public sewers that drain to Morpeth WwTW.

• 14/02721/OUT: Planning approval for a small residential development on the site of the former NWL

water treatment works alongside the River Wansbeck, immediately to the south of the proposed

application site. Foul drainage to site based package treatment plant discharging into the River

Wansbeck



10

2.6 CONSULTATIONS

2.6.1 NWL

In January 2014, 3E Consulting Engineers lodged a predevelopment inquiry with NWL. The NWL responses

dated 4th February and 30th April 2014 identified network capacity issues in North Morpeth.

Following WYG appointment in January 2015 NWL met with WYG representatives to discuss the proposed

development and consider, what, if any options were available for contributions to a strategic solution to

foul sewerage in North Morpeth. Subsequent to this meeting, WYG issued an email meeting record along

with a number of attachments. All liaison documents between the development team and NWL are provided

in Appendix C.

It can be seen that the outline plan for the provision of a strategic foul drainage solution (see Appendix C)

for North Morpeth consists of the following elements (working upstream from the WwTW):

1. Morpeth WwTW currently has headroom for around 800 residential units; in the event that further

expansion is required, no significant problems are anticipated;

2. It some future date it may be required to provide a new pumping station to allow flows from North

Morpeth to cross under the River Wansbeck and discharge into the WwTW;

3. Some future reinforcement of sewers may be required between the River Wansbeck and the St

George’s Hospital site;

4. New gravity sewers with sufficient capacity to convey flows from further upstream can be provided

in conjunction with re-development of the St George’s Hospital Site;

5. A new pumping station is required, located adjacent to the proposed Northgate roundabout. Twin

rising mains routed along the new bypass cycleway would convey flows from the pumping station to

the new gravity sewers in the St George’s Hospital Site. The pumping station can be sized to

accommodate the proposed Mitford Estates development and the developments at and adjacent to

the Northgate Hospital.

The references to site options 1,2 and 3 on the plan provided in Appendix C have now been largely

superseded by the fuller site FDS set out on the masterplan in Appendix A.



11

2.6.2 EA

Following WYG appointment in January 2015, a pre-development inquiry was lodged with the Environment

Agency. The EA responded in writing on 10th February 2015. A copy of both the pre-development and the

EA response is provided in Appendix D.

The EA note that the pre-development inquiry proposes a FDS involving on-site treatment and discharge

into the River Wansbeck; Noting the dependence of this strategy on the issue of an Environmental Permit or

Discharge Consent for the proposed discharge of treated effluent tin to the Wansbeck, the EA recommend

that the permit application is submitted concurrently with the planning application.



12

3 FOUL DRAINAGE: PLANNING POLICY AND LEGISLATION

3.1 INTRODUCTION

In order to develop an appropriate foul drainage strategy it is necessary to appreciate planning policy and

other legislative impacts that may have a bearing on strategy selection. The relevant policies and legislation

are discussed below.

3.2 NPPF AND PPG

The general approach to foul drainage within the NPPF is to prevent development being permitted which will

result in adverse impacts on the natural environment on account of the proposed foul drainage

arrangements. The key section of the NPPF is Section 11 which has the title ’Conserving and Enhancing the

Natural Environment’ (paragraphs 109 – 125). Specifically paragraph 109 states, ‘The planning system

should contribute to and enhance the natural environment by....preventing both new and existing

development from contributing to or being put at unacceptable risk from, or being adversely affected by

unacceptable levels of soil, air water or noise pollution or land instability..’

In addition paragraph 120 adds ‘To prevent unacceptable risks from pollution and land instability, planning

policies and decisions should ensure that new development is appropriate for its location. The effects

(including cumulative effects) of pollution on health, the natural environment or general amenity, and the

potential sensitivity of the area or proposed development to adverse effects from pollution, should be taken

into account...’.

The PPG has a specific section dealing with ‘Water Supply, Wastewater and Water Quality’ which are

specifically cross referenced to NPPF paragraphs 109 and 120. The PPG indicates that water quality could be

a significant planning concern due to ‘a lack of adequate infrastructure to deal with wastewater’. As noted

above, at the time of submission, wastewater infrastructure is considered by NWL to be inadequate in North

Morpeth, although NWL are considering how the system might be reinforced.

Paragraph 20 (reference ID: 34-020-20140306) of the PPG Chapter includes a section entitled ‘Are there

particular considerations that apply in areas with inadequate wastewater infrastructure?’ This section makes

it clear that the first presumption is to provide a system of foul drainage discharging into a public sewer to

be treated at a public sewage treatment works. However, the PPG recognises that ‘the timescales for works

to be carried out by the sewerage company do not always fit with development needs’ and ‘where a

connection to a public sewage treatment plant is not feasible (in terms of cost and practicality) a package



13

sewage treatment plant can be considered’ that treats the effluent to a standard set by the Environment

Agency’. The PPG requires operation and maintenance plans of such treatment plants to be set out by the

developer.

3.3 LOCAL PLANNING POLICIES

The NCC draft planning policy consultation document places a degree of reliance on the findings of the

Northumberland Water Cycle Study (discussed above) to direct development into areas where adequate

sewerage capacity is available thereby minimising the need for new infrastructure. Any new infrastructure

required to support new development should not have adverse impacts on the environment and should be

delivered in advance of occupation. Where non mains drainage systems (such as package treatment plants)

are required, these should be carefully sited and designed to have no adverse impact on water quality.

The Morpeth Neighbourhood Plan (MNP) Consultation Draft January 2015 deals with the issue of foul

drainage infrastructure in Sections 2.7.1 (in respect of overall ‘Vision’) and 3.10.1 in respect of ‘Drainage

System and Sewage Treatment Capacity’ in Neighbourhood Plan Policies. The MNP encourages the use of

‘grey-water’ systems in reducing flood risks, but recognises that the provision of additional foul drainage

infrastructure capacity rests with NWL and protection of the water environment with the EA.

3.4 WATER INDUSTRY REGULATION AND LEGISLATION

The primary legislation governing the operation of water utilities, such as NWL, is the Water Industry Act

1991 (WIA 1991). S94 of the WIA 1991 places two general obligations on a water utility with respect of

sewerage systems (a) ‘to provide and extend such a system of public sewers (whether inside its area or

elsewhere) and so to cleanse and maintain those sewers as to ensure that that area is and continues to be

effectually drained’ and (b) ‘to make provision for the emptying of those sewers and such further provision

(whether inside its area or elsewhere) as is necessary from time to time for effectually dealing, by means of

sewage disposal works or otherwise, with the contents of those sewers’.

These two obligations relate to the two primary elements of the public sewerage network: (a) the system of

pipes, pumping stations and other accessories which constitute the sewerage network and (b) the waste

water treatment works. Investment in the two arms of the sewerage system is regulated by Ofwat who

place water utilities under tight controls to minimise expenditure in the interest of keeping water rates paid

by consumers affordable. Plans are reviewed by Ofwat for 5 yearly Asset Management Plans (AMPs) the

next AMP (AMP 6) running from April 2015 – April 2020.



14

S98 of the WIA 1991 allows individual developers to requisition both new connections to the existing public

sewer network and increases in capacity to the sewerage network to overcome any downstream capacity

problems. However, S98 does not allow increases in treatment capacity to be ‘requisitioned’. Given this

arrangement, water utilities typically increase treatment works capacity in the light of adopted local plans.

Improvements to wastewater treatment works can take a long time to plan and implement because planning

permissions may be required with supporting EIAs plus review of existing Environmental Permits or

Discharge Consents (see below) which will be typically determined in the light of Water Framework Directive

(WFD) objectives for the receiving waters. However, it is also the case that consented development build

out rates are usually not so rapid as to compromise existing wastewater treatment plant operation and

compliance with existing consents.

Typically small incremental improvements to the sewerage network can be dealt with via the S98 requisition

process. However, the S98 process is not suited to strategic re-configuration or extension of the sewerage

network in the interests of multiple developer plans. S94 of the WIA provides the power for a water utility to

extend or strategically alter the sewerage network where this is required either to support adopted Local

Plans, or more usually in the light of consented development. Clearly S94 strategic sewerage network

extension could be supplemented by individual S98 requisitions where this is financially viable.

It should be noted that water utility investment in the light of an adopted local plan could easily result in

unnecessary expenditure by the water utility if extensive infrastructure investment is made ahead of

consented development implementation. For this reason synchronisation of infrastructure provision with

development implementation can be difficult. In the short term, such a situation may require early

development phases to be supported by package treatment plants, provided that the cumulative effect of a

proliferation of such plants does not compromise WFD objectives for the receiving water bodies.

3.5 ENVIRONMEMTAL PERMITS AND DISCHARGE CONSENTS

3.5.1 Consent Regime

As can be noted from the above, a consenting regime for new discharges of treated effluent to water bodies

is crucial to protection of the environment. The EA are responsible for determining appropriate standards of

water quality that are to be achieved prior to discharge of a treated effluent to a water body. In setting

standards, a key driver is the WFD objectives for any water bodies that might be affected. However, impacts

on protected species is clearly also a relevant consideration.

The EA, noting that it is proposed to discharge treated effluent from the development into the River

Wansbeck have recommended that the application for the Environmental Permit or Discharge Consent be

made in tandem with the planning application. The Environmental Permit or Discharge Consent application



15

for the proposed wastewater treatment plant is currently under preparation and will be submitted in March

2015. The size of the completed development means that the required permit is bespoke permit ‘Part B6-

Water-Discharge Activity’.

3.5.2 WFD Objectives

River Basin Management Plans (RBMPs) are drawn up for the 10 river basin districts in England and Wales

as a requirement of the Water Framework Directive. Morpeth is located in the area covered by the

Northumbria District River Basin Management Plan and is located within the ‘Northumberland Rivers’

catchment area. The specific water body reference is River R79 ‘Wansbeck from Font to North Sea’

(GB103022077060). The upstream extent of this water body is the confluence of the Font and Wansbeck

which occurs just upstream of the site at Mitford. Whilst all surface water within the water body reference

area is a relevant consideration, only the water in the larger watercourses are in effect monitored and

shown on EA mapping. The watercourses specifically considered are the River Wansbeck and Cotting Burn.

The current ecological and status of this watercourse system is ‘poor’ with predicted ecological potential for

2015 indicated as being ‘moderate’. The current chemical quality is ‘fail’ with this situation not expected to

improve by 2015. A more detailed breakdown of the biological and other supporting elements necessary to

achieve the overall status objective of ‘good’ is provided in Annex B of the River Basin Management Plan

which can be found in Appendix E of this report.

Annex G of the RBMP ‘Pressures and Risks’ provides an assessment of a range of factors for each water

body in the RBMP. This is done by using the following classification for each water body: ‘not at risk’;

‘probably not at risk’; ‘probably at risk’ and ‘at risk’. Particular risks arising from wastewater treatment

facilities that are considered in Annex G are ‘Total Oxidized Nitrogen (combined point and diffuse sources)’,

‘Ammonia (combined point and diffuse sources)’ and ‘Biological Oxygen Demand (BOD) (combined point and

diffuse sources). For each of the above pressures River R79 ‘Wansbeck from Font to North Sea’ is indicated

as being ‘Not at Risk’. The greatest risks to this water body are ‘Diffuse Source Pesticide’ and ‘Diffuse Source

Phosphorous Pressures from Agriculture’ for which the water body is shown as having the most challenging

designation of ‘at risk’.

RBMPs are reviewed on a 6 year cycle and a consultation is currently taking place in relation to the RBMPs

nationally. For the Wansbeck Operational Catchment investigations 17 reasons have been identified as to

why the water body is not achieving ‘good’ status. 5 of the reasons are on account of ‘pollution from waste

water’, although specific sites of pollution are not provided. However, the consultation identifies the

following measures for the Wansbeck: ‘Improve modified physical habitats’; ‘Improve the natural flow and

level of water’; ‘Manage pollution from rural areas’ and ‘Manage pollution from mines’. It would appear from



16

the consultation that resolution of the ‘pollution from waste water’ is primarily targeted at rural areas rather

than the more urbanised environment in the immediate vicinity of Morpeth.

3.6 CONCLUSIONS

It would be reasonable to conclude from the above review that an appropriately defined Environmental

Permit for a treated effluent from a wastewater treatment works located within the site and discharging into

the River Wansbeck is unlikely to compromise achievement of the WFD objectives for the water body.

Similarly, it is reasonable to assume that any future connection to the public sewer network and conveyance

of flows to Morpeth WwTW would be accompanied by expansion and improvement of the WwTW in line

with likely development build out rates of consented development within Morpeth and reasonable

compliance to existing Environmental Permits for the works.



17

4 PROPOSED STRATEGY

4.1 INTRODUCTION

The strategy for the proposed development must take account of the following:

1. The current absence of a suitable local connection for any foul drainage from the site;

2. NWL proposals for the provision of a new sewerage network to serve development in North

Morpeth (possibly with some elements being constructed in conjunction with the construction of the

Morpeth bypass);

3. The likely routing of a connection to a new system to be provided in conjunction with (2) above to

be by either requisition or by agreement of the landowners;

4. Arrangements for the treatment of effluent from the site in perpetuity or until such time as a system

to be provided by NWL becomes locally available; the level of treatment to be provided is to be

determined by the EA in conjunction with an Environmental Permit application;

5. Reasonable flexibility of the site sewerage infrastructure, including any impacts on the masterplan

(for pumping stations), such that the system can connect to a site treatment works or connect to a

local public sewer network as provided by NWL in the future;

6. The site foul drainage system is to exclude rainwater and trade effluents, and,

7. Clearly, the strategy needs to be in accordance with the NPPF and PPG and take account of the

emerging local planning policies.

In view of the above the proposed strategy is to provide a site based waste water treatment plant that

discharges into the River Wansbeck, via existing outfalls to the River. The system draining to the treatment

plant will exclude rainwater and trade effluents. An application for the associated required Environmental

Permit is to be submitted in tandem with the planning application. The site system will be designed such

that, if at a future date, a new public sewer system serving North Morpeth is provided by NWL (in

conjunction with the new bypass or otherwise) to pick up other consented developments (also reliant on

local treatment plants) in the vicinity of the proposed Northgate Roundabout, then a connection to this

system from the site will be practicable.

Greywater recycling may reduce water supply requirements in areas of high water stress. However, Morpeth

is not an area of high water stress, so this is not an issue that requires resolution. Furthermore greywater

recycling will not remove the need for either a connection to mains drainage or the provision of a site based



18

wastewater treatment plant. As such, greywater recycling, which introduces considerable complexity into

property plumbing brings little benefit in the circumstances of this site and has therefore been dismissed as

an option for inclusion within the development proposals.

4.2 DISCUSSION OF OPTIONS

4.2.1 Timescales and Phasing

The key phasing arrangements for the proposed development are as follows. Firstly, commencement of the

proposed development is dependent on the North Morpeth bypass reaching an appropriate stage of

completion along the site frontage to allow a start to be made. It is then anticipated that the TRSA will be

completed within 18 months of the proposed development commencement. Thereafter, the residential build

out is expected to take place over a period of 6 years at a rate of approximately 50 units per year.

Implementation of the country park proposals will occur in years 4-5 of the build out.

For the reasons outlined above, the timing of any NWL sewerage extension to serve the north of Morpeth is

unknown. However, should the works be undertaken in conjunction with the bypass, it would be reasonable

to assume that a commercially viable connection would be available at the same time that the proposed

development was able to be commenced. In this scenario, it would not be necessary to implement any

approved waste water treatment plant.

In the event that the NWL extension is not available, a modular package treatment plant with sufficient

capacity to cater for the TRSA (and connecting sewerage infrastructure) will be provided. Thereafter, the

capacity of the plant will be increased as build out proceeds using modular units to continue provide

sufficient headroom to allow compliance with the Environmental Permit. As and when a commercially viable

public sewer connection becomes available, the connection will be made and the plant will then be removed

and the area appropriately reinstated.

A plan showing the key elements of the site foul drainage infrastructure is shown on the masterplan

provided in Appendix A.

4.2.2 Treatment on Site: Discharge Locations

Treated effluent discharge options that have been considered are (i) disposal by soakaway (ii) discharge

northwards to Benridge Burn (iii) discharge to Scott Gill and (iv) discharge to the River Wansbeck.

However, the possible eventual size of the proposed treatment plant places restrictions on potential

discharge locations.



19

As such, the most suitable discharge location is the River Wansbeck, which is able to provide a high level of

dilution in all conditions. WFD considerations confirm that of the options available, this is the most

appropriate.

Mitford Estates currently own the land between the B6343 and the River Wansbeck and also have an

existing piped land drainage system discharging under the B6343 and into the Wansbeck. It is proposed to

re-use this pipework and outfall (renovated as necessary) for discharge of the treated effluent into the River

Wansbeck.

4.2.3 Treatment on Site: Plant Design and Location

Inasmuch as the treatment plant is required to discharge to the River Wansbeck, which runs to the south of

the B6343 and the proposed Lancaster Country Park, a location in the south west corner of the site is

proposed. This location is in Flood Zone 1 just outside the extent of Flood Zones 2 and 3 associated with

the River Wansbeck and is therefore at a low risk of fluvial flooding (less that 0.1% AEP). The FRA does not

identify any other significant flood risks at this location.

The location provides easy vehicular access to the B6343 and power supplies are understood to be available

as these would previously have supplied the adjacent now abandoned NWL water treatment works site.

The treatment plant is located against the visually intrusive A1 River Wansbeck viaduct, but will screened

from the proposed Lancaster Country Park by appropriate planting.

It is proposed to use package treatment plant units. Typically such units are of insufficient individual size to

serve a development of the size proposed. However, as indicated above, the units will be installed with

regard to the phasing of the development with the unit for the TRSA being placed first with space left for

further units to serve the proposed residential areas outwith the TRSA (in the event that later connection to

mains drainage is not possible).

4.2.4 Treatment Plant Operation and Maintenance

Maintenance of the package treatment plant units will be by management company (possibly the suppliers

of the package treatment units). In the event that it becomes clear that the north Morpeth sewerage

infrastructure is not going to be provided by NWL in the foreseeable future, it is proposed to discuss with

NWL options for upgrading the works to permit adoption by NWL. This would then permit adoption of the

upstream drainage infrastructure.



20

4.2.5 Site Infrastructure

In order to facilitate the inherent adaptability necessary to accommodate a future connection to an extended

North Morpeth foul sewage network the following approach is required.

1. All primary foul drainage will be constructed to Sewers for Adoption (SfA) standards, thus allowing

future adoption by NWL;

2. Foul sewers within the TRSA area will drain northwards towards the access road to the new

roundabout to a collection manhole (with an approximate invert level of 64.5m AOD); This invert

level would permit a future gravity connection to a new Pumping Station to be provided by NWL in

the vicinity of the Northgate Roundabout;

3. The foul sewers within the TRSA will be sized so that primary routes will be capable of

accommodating all flows from the relevant catchments of the proposed residential areas;

4. In the event that early extension of North Morpeth public sewers occurs such that a commercially

viable and timely connection to this system is possible then such a connection will be made;

5. In the event that extension of the North Morpeth public sewers is delayed or does not occur a

pumping station will be provided at the location shown on the masterplan. The pumping station

rising main will follow the western boundary of the site until it reaches the point where effluent can

drain by gravity down towards the proposed treatment plant.

6. Throughout the build out, the possibility of commercially acceptable and timely connection to mains

drainage in the north of Morpeth will be reviewed and taken into account in the design of site foul

drainage infrastructure.

7. In the event that a mains drainage connection is made, it will be necessary to pump flows from the

south east corner of the proposed residential area due to levels in this location. A plot of sufficient

size with vehicular access has been left within the masterplan to accommodate this pumping station

should it be required.

A plan showing the key elements of the site foul drainage infrastructure is provided in Appendix A.



21

5 CONCLUSIONS

This report makes the following conclusions:

1. The site is located in an area where there are no reasonably available existing public sewers with

any headroom available such that a new connection can be made to serve any or all of the

proposed development.

2. The nearest public sewers are within the existing Lancaster park development to the east of the

proposed site and these have only sufficient capacity to deal with the existing development. This

system drains through central Morpeth where there are other known sewer capacity issues.

3. Morpeth WwTW has recently been upgraded and has sufficient capacity to accommodate

approximately 800 more residential units. Although significant new development is proposed in

Morpeth, NWL do not perceive treatment works capacity to be a constraint on development as build

out rates are unlikely to exceed the ability of NWL to maintain a reasonable headroom and the

existing treatment works site can support further expansion.

4. The extent of consented development and possibilities of further expansion of North Morpeth

provides a strong driver for the installation of a strategic foul drainage solution elements of which

could be provided in conjunction with the new bypass.

5. Due to the uncertainties surrounding the timing of strategic foul drainage infrastructure provision in

North Morpeth the only FDS that provides sufficient certainty of implementation is to make provision

for foul treatment on site.

6. The level of treatment to be provided is to be determined by the EA in response to an application

for an Environmental Permit that is to be submitted in tandem with the planning application.

7. A review of the RBMP indicates that the discharge of treated effluent subject to compliance with an

appropriate Environmental Permit would not jeopardise the achievement of the WFD objectives for

the Wansbeck in Morpeth or further downstream. (The key pressures on the Wansbeck are primarily

on account of diffuse pollution within the rural catchment).

8. If at some future date, mains drainage becomes available such that a commercially viable

connection can be made, such connection will be made.



22

9. The site foul drainage infrastructure can be provided such that it has the necessary inherent

flexibility to be adapted to either continue to drain to the site wastewater treatment plant or to be

re-directed to a mains drainage connection.

10. The treatment plant will be for domestic sewage only and will not have rainwater or trade effluent

connections.

11. Inasmuch as water scarcity is not a significant driver in this location and few other benefits will

ensue, greywater re-cycling is not proposed.

12. Maintenance of the WwTW will be by private management company (preferably the supplier of the

package treatment units). In the event that extension of the foul drainage network is delayed

indefinitely or a commercially viable connection is not possible, consideration will be given to

upgrading of the plant to permit adoption by NWL, thus permitting adoption of the upstream foul

sewer network.

13. It is concluded that given the specific circumstances of this site, this FDS is in accordance with the

NPPF and the PPG and relevant water Industry legislation.

Foul Drainage Strategy Mitford Estate LLP Proposed...

Documents

Transcript of Foul Drainage Strategy Mitford Estate LLP Proposed...