Milton Keynes Water Cycle Study Outline Strategy · 2013. 10. 3. · Milton Keynes Council Water...

Milton Keynes Water Cycle Study Outline Strategy

Final

December 2008

In partnership with:

Milton Keynes Council

Water Cycle Study – Outline Strategy

Scott Wilson Mansfield i-Centre Hamilton Way Mansfield Nottinghamshire NG18 5BR Tel. 01623 600660 Fax. 01623 600661 www.scottwilson.com

This document has been prepared in accordance with the scope of Scott Wilson's appointment with its client and is subject to the terms of that appointment. It is addressed to and for the sole and confidential use and reliance of Scott Wilson's client. Scott Wilson accepts no liability for any use of this document other than by its client and only for the purposes for which it was prepared and provided. No person other than the client may copy (in whole or in part) use or rely on the contents of this document, without the prior written permission of the Company Secretary of Scott Wilson Ltd. Any advice, opinions, or recommendations within this document should be read and relied upon only in the context of the document as a whole. The contents of this document do not provide legal or tax advice or opinion. © Scott Wilson Ltd 2008

Revision Schedule

Milton Keynes Water Cycle Study – Outline Strategy

December 2008

Rev Date Details Prepared by Reviewed by Approved by

01 23rd May 2008 Interim Draft Gemma Costin

Assistant Consultant

Carl Pelling

Senior Consultant

David Dales

Director

Andrew Woodliffe

Senior Consultant

02 22nd

July 2008 Final Draft Gemma Costin


Dr Jon Hillman

Senior Consultant

David Dales

Director

Andrew Woodliffe

Senior Consultant

03 26th September

2008

Final Draft v2 Gemma Costin


Andrew Woodliffe

Senior Consultant

David Dales

Director

04 19th December

2008

Final Gemma Costin


Andrew Woodliffe

Senior Consultant

David Dales

Director



Final December 2008 i

Table of Contents

Table of Contents.......................................................................................... i

Executive Summary .................................................................................... iv

Acronyms...................................................................................................viii

1 Introduction ....................................................................................... 1

1.1 Growth in Milton Keynes................................................................................................. 1

1.2 Development and the Water Cycle ................................................................................. 2

1.3 Milton Keynes WCS and the Planning Process............................................................... 3

2 Milton Keynes Water Cycle Strategy ................................................. 6

2.1 Approach to the Water Cycle Strategy............................................................................ 6

2.2 WCS Stakeholders ......................................................................................................... 8

3 Milton Keynes Growth Context ........................................................ 13

3.1 New Housing Areas ...................................................................................................... 13

3.2 New Employment Areas ............................................................................................... 18

4 WCS Methodology .......................................................................... 19

4.1 Step 1a / Step 1b: Baseline Conditions and Capacity ................................................... 19

4.2 Step 2: Water Services Infrastructure Development Options ........................................ 21

4.3 Data Limitations............................................................................................................ 22

5 Flood Risk Baseline......................................................................... 23

5.1 Flood Risk Identification Methodology........................................................................... 23

5.2 Available data and Assumptions................................................................................... 24

5.3 Baseline Description ..................................................................................................... 24

5.4 Fluvial ........................................................................................................................... 26

5.5 Sewers ......................................................................................................................... 30

5.6 Surface Water............................................................................................................... 32

5.7 Groundwater................................................................................................................. 35

5.8 Artificial Sources........................................................................................................... 36

5.9 Flood Risk Constraints Summary.................................................................................. 37

5.10 Data Limitations............................................................................................................ 39

6 Wastewater Baseline and Capacity ................................................. 41

6.1 Available Data and Assumptions .................................................................................. 42

6.2 Wastewater Treatment Baseline and Capacity ............................................................. 43



Final December 2008 ii

6.3 Wastewater Network Baseline and Capacity................................................................. 45

6.4 Wastewater Environment Baseline ............................................................................... 50

6.5 Water Quality Baseline and Capacity............................................................................ 51

6.6 Wastewater Summary .................................................................................................. 59

7 Water Resources and Supply Baseline ........................................... 61

7.1 Introduction................................................................................................................... 61

7.2 Available Data and Assumptions .................................................................................. 61

7.3 Regional Water Resources: Existing Situation .............................................................. 61

7.4 Milton Keynes - Water Resource Baseline Assessment................................................ 62

7.5 Water Supply – Existing Capacity ................................................................................. 65

7.6 Water Supply Network – Baseline................................................................................. 73

7.7 Bedford and Milton Keynes Waterway .......................................................................... 75

7.8 Water Resources and Water Supply Summary............................................................. 76

8 Water Cycle Option Development ................................................... 78

8.1 Introduction................................................................................................................... 78

8.2 Wastewater Option Development ................................................................................. 78

8.3 Water Resources Option Development......................................................................... 79

9 Generation of Flood Risk - SUDS Options....................................... 86

9.1 Introduction................................................................................................................... 86

9.2 Flood Risk from Development – Strategic Options........................................................ 86

9.3 SUDS Utilisation ........................................................................................................... 89

9.4 Flood Risk Management Summary............................................................................... 96

10 Ecological Assessment.................................................................... 97

10.1 Objectives and Approach.............................................................................................. 97

10.2 Sites within Milton Keynes Unitary Authority ............................................................... 101

10.3 Sites of Special Scientific Interest ............................................................................... 101

10.4 Local Nature Reserves ............................................................................................... 101

10.5 Downstream Sites - Special Areas of Conservation .................................................... 102

10.6 Downstream Sites - Special Protection Areas............................................................. 105

10.7 Ramsar Sites .............................................................................................................. 106

10.8 Sites of Special Scientific Interest ............................................................................... 108

10.9 Overall Screening Opinion .......................................................................................... 109

11 Water Quality / Water Framework Directive................................... 112

11.1 Water Framework Directive Standards ....................................................................... 113

11.2 WFD and Milton Keynes ............................................................................................. 118



Final December 2008 iii

11.3 WFD and Water Company Planning ........................................................................... 124

12 Development Area Assessment .................................................... 126

12.1 Central Area ............................................................................................................... 127

12.2 Eastern Area............................................................................................................... 129

12.3 Western Area.............................................................................................................. 131

12.4 Northern Area............................................................................................................. 133

12.5 South Western Area ................................................................................................... 135

12.6 Land East of the M1.................................................................................................... 137

12.7 Rural Areas................................................................................................................. 139

13 Water Efficiency ............................................................................ 142

13.1 New Development – Water Efficiency......................................................................... 142

13.2 Code for Sustainable Homes ...................................................................................... 142

13.3 Current Development – Reducing Existing Baseline ................................................... 144

14 Policy, Developer Guidance and Funding...................................... 145

14.1 Introduction................................................................................................................. 145

14.2 Developer Checklist.................................................................................................... 146

14.3 Funding and Cost Apportionment Mechanisms........................................................... 146

15 Conclusions and Recommendations ............................................. 150

15.1 Overview .................................................................................................................... 150

15.2 Flood Risk and Drainage ............................................................................................ 150

15.3 Water Environment ..................................................................................................... 151

15.4 Wastewater Treatment and Transmission................................................................... 153

15.5 Water Resources and Water Supply........................................................................... 154

15.6 Milton Keynes Tariff System ....................................................................................... 155

15.7 Scope for Detailed WCS (REMOVE) ...............................Error! Bookmark not defined.

16 References.................................................................................... 156

Appendix A – Data Requests ................................................................... 158

Appendix B – Wastewater Network Capacity Calculations ....................... 159

Appendix C – DWF Calculations .............................................................. 160

Appendix D – Hydrological Analysis......................................................... 161

Appendix E – SUDS Options Details........................................................ 162

Appendix F – Developer Checklist ........................................................... 165



Final December 2008 iv

Executive Summary

Study Purpose This Outline Stage 1 Water Cycle Study has assessed the impact of proposed growth targets for Milton

Keynes (as set out in the RSS) on the water cycle infrastructure and water environment of the Milton

Keynes study area. This has been undertaken for an approximate total of 57,950 new homes up to 2031.

It has been developed to inform and provide an evidence base to the initial stages of the production of

Milton Keynes Council’s Local Development Framework (LDF). It is also required to provide justification

for the planning of new infrastructure in Anglian Water Service’s strategic business planning; and to

provide the Environment Agency (EA) and Natural England (NE) with a strategic study that identifies and

suggests mitigation for potential water environment impacts (including flood risk) such that sustainable

development is proposed in Milton Keynes and that objections to proposed developments in Milton Keynes

are minimised.

The Outline Milton Keynes WCS has identified the existing capacity of the current water environment and

water cycle infrastructure and has used this assessment to determine where additional investment is

required to supply new infrastructure or to protect the water environment.

Wastewater Discharge Capacity and Water Environment Increased effluent discharges to the River Ouzel and River Great Ouse will impact on flood risk and water

quality. Before approving increases in consented discharges to these rivers, the EA will require further

catchment modelling to identify any necessary mitigation works particularly with reference to the lakes in

Milton Keynes. This should either be included in the detailed stage of the water cycle study, the level 2

SFRA or as an independent study for example a surface water management plan.

For water quality, the EA position has been that any increase in flows from WwTWs that occur as a result

of growth must comply with their policy on ‘No Deterioration’. This requires that increases in failure of a

mandatory standard caused by growth should be offset by reducing the consent limits of the associated

discharge(s). The policy allows the EA to impose consent limits up to the limit of technological capabilities

(Best Available Technology Not Entailing Excessive Cost - BATNEEC). It also allows the EA to make

special justification for imposing consent limits more stringent than BATNEEC.

Increase in Dry Weather Flow (DWF) equates to 8% of consented discharge from Cotton Valley is forecast

to be required during the planning period (to 2031). This will require an Appropriate Assessment of impact

on designated sites downstream. The detailed water cycle study will need to collect sufficient data to allow



Final December 2008 v

the EA/Natural England to complete an AA. This should build on the assessments completed for

Phosphorous

Wastewater Treatment and Wastewater Network Capacity There is sufficient capacity to accommodate short and medium term growth in all of the non rural

expansion areas in terms of wastewater treatment.

To accommodate the significant growth to the east (between Wavendon and Cotton Valley), upgrades to

the Broughton Brook trunk sewer are required. The ongoing work to increase the capacity of the inlet

works at Cotton Valley WwTW is expected to greatly increase the effective capacity of this trunk sewer and

other parts of the network. To serve the Western expansion, a combination of new pumping stations and

sewers is required to connect to the existing network. Capacity issues at Newport Pagnell and the

disruption and cost of upgrading the existing sewer to Cotton Valley mean that the proposed site east of

M1 motorway would need to be served by a new connection to this works. The south-west development

area can be served with little infrastructure upgrade required to transfer to the point of connection to

existing system. In central Milton Keynes, some infrastructure upgrades are expected to be required

particularly in the Oakgrove area.

Some strategic scale investment will be required for medium and long term development in terms of

wastewater network infrastructure in order to service the new development particularly within the western

expansion area, eastern expansion and for land to the east of the M1.

In the long-term, (2020-2031) flow consent at Cotton Valley and extension of the treatment works will be

required.

Water Resources and Supply Capacity This study has shown that in the short-medium term there are sufficient water resources and supply

capacity for the development proposed for Milton Keynes. However, in the longer term (2019/20 and

beyond) it may be necessary for a major regional water resource development such as the Trent Transfer

scheme to ensure there is sufficient supply to service the development in Milton Keynes.

Currently Milton Keynes receives most of its water from Wing and Grafham WTWs, which are in turn fed

from Rutland Water and Grafham Water respectively. Work is currently being undertaken at Wing WTW

which will ease the situation in the short term. In order to maintain sufficient gap between supply and

demand, it will be necessary to supplement available resources by the development of local schemes,

such as Foxcote WTW (a surface water intake and reservoir), within the existing abstraction licence limits.

In addition, phased developments at Clapham WTW will release Deployable Output from Grafham to



Final December 2008 vi

supply the growth in Milton Keynes, although this may also require an increase in the abstraction licence at

Clapham (on the River Bedford Great Ouse).

The extent of the development proposed for Milton Keynes will also require stringent water efficiency

measures to put in place on all new homes, these measures should be in-line with the current best practice

in this area e.g. Code for Sustainable Homes (April 2008).

At this high level, there are a number of uncertainties which have the potential to adversely impact supply.

These include the impacts of climate change, the Review of Consents and legislation associated with the

Water Framework Directive (WFD).

It is essential that water supply network modelling and modelling of the capacity of the water treatment

works supplying Milton Keynes is undertaken as part of the detailed WCS.

Flood Risk and Drainage There are several Main River

1, IDB managed and Ordinary Watercourses that run through the study area.

All of these watercourses have Flood Zones and hence flood risk associated with them. The main

watercourses in the study area are the River Great Ouse to the north of the study area, the River Ouzel to

the east of the study area, Chicheley Brook and Broughton Brook to the east of the study area, Water

Eaton Brook to the south of the study area and Loughton Brook to the west of the study area.

Instances of fluvial, surface water and sewer flooding have been recorded in the study area, and future

development has the potential to increase the frequency and consequence of such flooding through the

increases in and runoff from impermeable areas. These increases can be mitigated through the use of

integrated SUDS, careful development design, development control and masterplanning. Milton Keynes

has a network of green infrastructure which will be maintained and enhanced through development design.

Groundwater flooding has not been recorded in the study area but there are however areas of more

permeable geology to the south east of the area, near Woburn Sands where there is a potential risk of

such flooding.

The Grand Union Canal also runs through the study area and carries with it an inherent flood risk.

Broad Expansion Area Assessments An assessment has been undertaken of the seven potential expansion areas to demonstrate how

development could impact upon the water environment, wastewater treatment and network capacity, water

supply, and flood risk.

1All watercourses shown as such on the statutory main river maps held by the Environment Agency and the Department of Environment, Food and Rural Affairs, and can include any structure or appliance for controlling or regulating the flow of water into, in or out of the channel. The Environment Agency has permissive powers to carry out works of maintenance and improvement on these rivers



Final December 2008 vii

These broad scale assessments have shown that in the short and medium term (to 2021), with the

exception of certain sewer network issues, there are no major constraints to development within Milton

Keynes. At this stage, there are however a number of unknowns and some key assumptions, particularly

with regards to wastewater and network capacity have been made. It is vital that these uncertainties are

considered thoroughly as part of the next detailed stage WCS. It has also not been possible to rule out

adverse impacts upon the designated sites that are situated within and downstream of the study area, and

it may be that these become significant constraints following a detailed assessment.



Final December 2008 viii

Acronyms

Abbreviation Description

AMP Asset Management Plan

AWS Anglian Water Services

BAT Best Available Technology

BATNEEC Best Available Technology Not Entailing Excessive Cost

BOD Biochemical Oxygen Demand

CAMS Catchment Abstraction Management Strategy

CFMP Catchment Flood Management Plan

CSH Code for Sustainable Homes

CSO Combined Sewer Overflow

CLG Communities and Local Government

DEFRA Department for Environment, Food and Rural Affairs

DO Dissolved Oxygen/Deployable Output

DPD Development Plan Document

DWF Dry Weather Flow

EA Environment Agency

EP English Partnerships

FtFT Flow to Full Treatment

GI Green Infrastructure

GQA General Quality Assessment

HPPE High Performance Poly Ethylene (pipe)

IDB Internal Drainage Board

l/c.d Litres per capita per day (water consumption measurement)

LDF Local Development Framework

LiDAR Light Detection and Ranging

LPA Local Planning Authority



Final December 2008 ix


MBR Membrane Bioreactor

MKC Milton Keynes Council

MKP Milton Keynes Partnership

MKWCS Milton Keynes Water Cycle Strategy

N Nitrogen

NGP New Growth Point

NE Natural England

NVZ Nitrate Vulnerable Zone

OFWAT The Office of Water Services

P Phosphorous

PE Population Equivalent

PPS Planning Policy Statement

RSS Regional Spatial Strategy

SA Sustainability Appraisal

SAC Special Area for Conservation

SEA Strategic Environmental Assessment

SEP South East Plan

SfG Strategy for Growth

SFRA Strategic Flood Risk Assessment

SIMCAT EA mathematical River Water Quality Model

SPA Special Protection Area

SPZ Source Protection Zone

SRP Soluble Reactive Phosphorus

SSSI Site of Special Scientific Interest

SWMP Surface Water Management Plan

SUDS Sustainable Drainage Systems

TSFR Treated Sewage Flow Recorder (flow meter)



Final December 2008 x


TSS Total Suspended Solids (in waste water)

UWWTD Urban Wastewater Treatment Directive

WCS Water Cycle Strategy/Water Cycle Study

WFD Water Framework Directive

WRMP Water Resources Management Plan

WRPZ Water Resources Planning Zone

WRZ Water Resources Zone

WSI Water Services Infrastructure

WwTW Waste Water Treatment Works



Final December 2008 1

1 Introduction

1.1 Growth in Milton Keynes

Milton Keynes is located in southeast England, bordering the administrative districts of Aylesbury Vale

(South East Region) Bedford Borough, Mid Bedfordshire, South Bedfordshire (East of England Region)

Wellingborough and South Northamptonshire (East Midlands Region). Milton Keynes is one of the fastest

growing urban centres both in the sub-region and the country and it is a significant employment centre for

the sub-region. It is also a significant retail, service and administrative centre for the sub region. The

Milton Keynes city limits are located to the south of the confluence of two rivers, the River Great Ouse and

the River Ouzel and are surrounded by several environmentally and ecologically important designated

sites including four Sites of Special Scientific Interest (SSSI) and several county wildlife sites.

The housing growth targets for Milton Keynes up to 2026 are set out in the draft South East Plan (SEP)2

and have been augmented in this WCS with figures from the Milton Keynes Council (MKC) Local

Development Framework (LDF) and Strategy for Growth to 2031. A substantial amount of the proposed

growth to 2026 is allocated in seven broad expansion areas (north, rural areas, central area, east, west,

south-west and land east of the M1), two of which (south east and south west) extend into the

administrative areas of the neighbouring authorities of Mid Bedfordshire and Aylesbury Vale.

Water Cycle Studies (WCS) are required to ensure that proposed growth does not adversely impact on the

existing water cycle environment and that new Water Services Infrastructure (WSI) can be planned for and

provided alongside new development in a sustainable and cost effective manner. Due to the scale of

development proposed for Milton Keynes, it is considered that a WCS is required to ensure that the

proposed growth targets can be met without adversely impacting on the water environment and that

required infrastructure can be planned for and brought online alongside new development, in a timely and

phased manner.

2 All references to the draft South East Plan include the Panel Report from the Public Examination, which sets out a revised set of housing and employment targets, spatial distribution and phasing. The Panel Report figures are the ones used in this WCS and will need to be reconsidered once the South East Plan is finally adopted.




1.2 Development and the Water Cycle

1.2.1 What is the ‘Water Cycle’?

In its simplest form, the Water Cycle can be defined as ‘the process by which water is continually recycling

between the earth’s surface and the atmosphere’. Without considering anthropogenic influences, it is

simply the process by which rain falls, and either flows over the earth’s surface or is stored (as

groundwater, ice or lakes) and is then returned to the atmosphere (via evaporation from the sea, the soil,

surface water or animal and plant life) ready for the whole process to repeat again.

In the context of this study, the ‘water cycle’ has a broader definition than the simple water or ‘hydrological

cycle’. The human influence on the water cycle introduces many new factors into the cycle through the

need to abstract water from the natural environment, use it for numerous purposes and then return to the

natural system. The development and introduction of technology such as pipes, pumps, drains, and

chemical treatment processes has meant that human development has been able to manipulate the

natural water cycle to suit its needs and to facilitate growth and development. ‘Water Cycle’ in this context

is therefore defined as both the natural and engineered water related environment (such as rivers, wetland

ecosystems, aquifers etc), and the WSI (hard engineering focused elements such as: water treatment

works, supply pipelines and pumping stations) which are used by human activity to manipulate the system.

1.2.2 The Problem

In directly manipulating elements of the water cycle, man affects many changes to the natural water cycle

which can often be negative. To facilitate growth and development, there is a requirement for clean water

supply which is taken from natural sources (often depleting groundwater stores or surface systems); the

treatment of waste water which has to be returned to the system (affecting the quality of receiving waters);

and the alteration and management of natural surface water flow paths which has implications for flood

risk. These impacts can indirectly affect ecology, which can be dependent on the natural features of a

water cycle.

1.2.3 Implications for Development: The Solution

In many parts of the UK, some elements of the natural water cycle are considered to be at, or close to their

limit in terms of how much more they can be manipulated. This is especially relevant for the south and

east of England where rainfall and hence available water for supply is the lowest in the UK. Further

development will lead to an increase in demand for water supply and a commensurate increase in the

requirement for waste water treatment; in addition, flood risk may increase if development is not identified




and planned for in a strategic manner. The sustainability of the natural elements of the water cycle is

therefore at risk.

A WCS is an ideal solution to address this problem. It will ensure that the sustainability of new

development is considered with respect to the water cycle, and that new WSI introduced to facilitate growth

is identified and planned for in a strategic manner. In so doing, the WCS can ensure that provision of

water WSI is sufficient such that it maintains a sustainable level of manipulation of the natural water cycle,

drawing upon the Strategic Flood Risk Assessment (SFRA) to facilitate flood risk mitigation, and to

highlight areas where a Surface Water Management Plan (SWMP) may be required. A twin-track

approach and behavioural change will be required to achieve the high levels of water efficiency required to

ensure this sustainable manipulation of the water cycle is adhered to.

1.3 Milton Keynes WCS and the Planning Process

The Department for Communities and Local Government (CLG) are responsible for managing Local

Government and as such, the associated planning guidance. A Local Development Framework (LDF) is

the spatial planning strategy introduced in England and Wales by the Planning and Compulsory Purchase

Act 2004 and given in detail in Planning Policy Statement (PPS) 12. The LDF and its associated Local

Development Documents (LDDs) will replace the previous Local Plan documents produced by Local

Planning Authorities (LPA) and will set out how the growth within each LPAs administrative area will be

achieved. It should be noted that the WCS is an iterative process, as it evolves it will require continual

monitoring and review and be periodically updated.

As part of the LDF process, LPAs are required to produce evidence based studies which support the

selection processes used in deciding on final growth targets and areas to be promoted for growth. The

WCS is one such example of an evidence-based study which specifically addresses the impact of

proposed growth on the ‘water cycle’ and as such, will form an important component of the emerging MKC

LDF. Specifically the WCS will sit alongside the Sustainability Appraisal (SA), Strategic Environmental

Assessment (SEA) and Appropriate Assessment (AA), where necessary, forming a key evidential

document in the LDF portfolio. The WCS builds upon other key flood risk work carried out, including the

Milton Keynes Drainage Strategy (Halcrow 2004) which has been adopted as Supplementary Planning

Guidance (SPG). The WCS will also inform the emerging MKC Core Strategy Development Plan

Document (DPD), the key strategic policy document in the emerging LDF.

WCS’s are a relatively new approach to assessing the impact of new development with respect to the

water cycle; however, the Milton Keynes WCS must be sufficiently robust such that it can form part of the

evidence base for the emerging LDF.




1.3.1 WCS Links with other LDF Studies

There are several other studies which have been, or are in the process of being produced on behalf of

MKC to act as evidence bases to the developing LDF. Those most relevant to the WCS are listed below

and it is intended that the developing WCS will both inform and be informed by these studies:

• A Strategy for Growth to 2031 (SfG),

• Green Infrastructure Plan (GI),

• Strategic Flood Risk Assessment (SFRA),

Strategy for Growth to 2031

The overall aim of the SfG was to identify options for, and make a recommendation on, the optimal

directions for strategic growth, determine the implications of that growth in relation to infrastructure both

physical and social, and identify mechanisms and ways to deliver, manage and monitor that change. The

study is another key piece of the evidence base and has been used specifically to define the potential

development area options for the Core Strategy, to be assessed in this WCS.

Green Infrastructure Plan

The purpose of linking with the GI Plan has been to consider the potential for the water cycle elements of

the proposed development areas to be linked to Milton Keynes’ green corridors and infrastructure. This is

to ensure an appropriately resourced and managed network of accessible, sustainable and linked open

spaces for current and future generations, taking into consideration the large-scale growth proposed for

Milton Keynes. The key aim of the GI Plan is to make recommendations such that the future urban

extensions are to be developed sustainability, with green space and environmental assets to be protected

and enhanced and planned for from the outset.

Strategic Flood Risk Assessment

The Level 1 SFRA undertakes a strategic (district wide) assessment of the sources of flood risk in the MKC

administrative area and considers implications of flood risk arising from new development.

The Level 1 SFRA allows MKC to undertake Sequential Testing on any proposed or likely future potential

development areas, as required in Planning Policy Statement 25 (PPS25: Development and Flood Risk).

Sequential Testing is a method by which development areas are considered and selected on the basis of

taking forward the areas with lowest flood risk, unless there are overriding sustainability reasons for

considering higher risk options.

Where overriding factors prevail, a Level 2 SFRA assessment is required. A Level 2 assessment would

provide MKC with the evidence base required to undertake Exception Testing.




Preliminary outputs from the Level 1 SFRA have been used in the WCS to determine the level of flood risk

to potential development sites in Milton Keynes, but also the potential flood risk that might arise as a result

of development in Milton Keynes.

1.3.2 Aim of the Milton Keynes WCS

In conjunction with the other strategic studies which inform the LDF, a WCS for Milton Keynes is therefore

required to:

• Ensure a co-ordinated approach to identify water supply and waste water infrastructure to support

development,

• Avoid negative impact on water-dependent European sites of nature conservation and non

European designated sites,

• Assess the requirement for flood risk mitigation and identification of where Surface Water

Management Plans (SWMP) may be required,

• Identifying environmental and ecological constraints and maximising ecological opportunities and

enhancements,

• Provide an evidence base for LDDs to site development so that MKC can:

• Ensure delivery of new development in Milton Keynes in the most sustainable way with

respect to the water cycle environment,

• Maximise potential of existing WSI,

• Minimise need for new WSI.

The purpose of this report is to summarise the outputs of the Stage 1 Outline WCS undertaken for Milton

Keynes in light of the required housing and employment growth targets, as set out in the draft Regional

Spatial Strategy (RSS9).




2 Milton Keynes Water Cycle Strategy

2.1 Approach to the Water Cycle Strategy

The Milton Keynes WCS intends to test the suitability of the proposed development area options and

development scenarios for Milton Keynes taking into account existing and new WSI, whilst considering the

impacts of proposed growth to the receiving water cycle environment.

2.1.1 Stages of a Water Cycle Strategy

In general, there are three main stages in undertaking and producing a WCS (Figure 2-1).

Figure 2-1:Stages of a Water Cycle Strategy

Source: http://www.environment-agency.gov.uk/commondata/acrobat/water_cycle__1760254.pdf

The first stage of the Milton Keynes WCS was commissioned by the EA and the ‘Scoping Study’

undertaken by Halcrow.




This information has been used to inform this report, which forms the ‘Outline Study’. The Outline Study

will work alongside MKCs developing Core Strategy, and assist in providing a robust evidence base for

MKCs emerging LDF. For Milton Keynes, the Outline Study must assess and identify:

• Any absolute water cycle environmental capacity constraints to development,

• Any WSI constraints to development,

• Whether any new WSI is required and hence must be planned for to facilitate new development and

which strategic level options are available for delivering new infrastructure required,

• The most suitable (and sustainable) development areas and/or development scenarios with respect

to the water cycle.

The Outline Study will also provide the necessary evidence base for the water company as part of the AMP

process.

The final stage of the WCS is the ‘Detailed Study’ which will work alongside the latter stages of the LDF

process, taking into account other planning considerations as part of this process. The overall aim is to

lead to a water cycle strategy for Milton Keynes which:

• Identifies what WSI is required for Milton Keynes and where it is needed,

• Identifies who is responsible for providing and maintaining the infrastructure and when it has to be

provided by,

• Provides details regarding funding requirements, e.g. developer contributions and other potential

sources,

• Provides guidance for MKC and potential developers on site specific infrastructure requirements

(e.g. strategic and integrated SUDS).

Following completion of the Outline Study, the Detailed Study for Milton Keynes will be undertaken once

the development scenarios have been agreed with respect to all other planning considerations which must

be taken into account.

For the purposes of this report, the acronym WCS has been used to refer to both the Water Cycle Study, the outline stage of which this report forms, and the all encompassing three stage Water Cycle Strategy.




2.1.2 Development Definition

In the context of this Outline Study and due to the proposed volume of development within Milton Keynes,

‘broad’ areas have been determined in conjunction with MKC and the Milton Keynes Partnership (MKP). It

is these ‘broad’ areas which are identified for constraints and risk with respect to the water cycle

environment and WSI, as well as the requirement for new infrastructure required to facilitate development.

However, it is recognised that development can be brought forward in a number of ways according to

associated site constraints and risks. It is also recognised that these constraints and risks also apply to

other planning aspects of future development being considered by MKP and MKC (i.e. transport links,

hospitals and health care and schools). As such, when considering the water cycle and water environment

in isolation through this study, there is a requirement to consider a range of options for meeting housing

and employment targets.

This outline WCS achieves this by identifying incremental potential development scenarios within smaller

study areas and assessing the subsequent sustainability for each of the incremental potential development

scenarios with respect to the water cycle. In so doing, this outline WCS allows MKP and MKC to consider

the relative importance of water cycle issues alongside other planning considerations when making final

decisions on allocations and development promoted in the Core Strategy.

2.1.3 Development in Milton Keynes

The broad development areas identified for Milton Keynes (in the SfG, the draft RSS 9 and the Core

Strategy Preferred Options), are within and adjacent to the existing urban extent of Milton Keynes.

However, growth is also shown to push out into the fringes of Mid Bedfordshire and Aylesbury Vale

(although these growth directions have yet to be agreed, as the growth targets set out in the draft RSS9

have yet to be finalised).

In addition to the proposed development within the ‘broad’ development areas, the additional WSI required

for growth has the potential to impact on a wider area associated with the protected areas of high

ecological value and biodiversity

2.2 WCS Stakeholders

The outline WCS is being undertaken on behalf of MKC, MKP and the Environment Agency (EA). The

study has been overseen by a Project Steering Group chaired by MKC, and made up of representatives

from other organisations, all of which have a vested interest in future development in Milton Keynes and/or

its impact on WSI and environment. The following parties made up the Project Steering Group:




• Milton Keynes Council (MKC),

• Milton Keynes Partnership (MKP),

• Environment Agency (EA),

• MK Parks Trust,

• Aylesbury Vale District Council (AVDC),

• Anglian Water Services Ltd (AWS),

• English Partnerships (EP),

• Buckingham and River Ouzel Internal Drainage Board (IDB),

• Scott Wilson (SW).

2.2.1 Integration with the Planning System

It is important at this stage to consider the planning timelines, both for MKC in terms of the LDF but also

AWS in terms of the funding mechanisms for new water supply and water treatment infrastructure.

2.2.2 Local Authority Planning

The production of the LDF involves an extensive process of consultation with the wider public and for

Development Plan Documents like the Core Strategy, public examination for CLG. This overall planning

process supports a two stage strategy for the water cycle study so that important considerations are not

overlooked in-between the production of an outline study (which informs the Core Strategy) and the

detailed study (which will be used in site or topic specific Local Development Documents). The detailed

WCS will also make recommendations on phasing for development based on the water cycle issues.

2.2.3 Water Company Planning

There are two elements of Water Company planning that are pertinent to the Milton Keynes WCS and

specifically, with regard to integration with Spatial Planning timelines for LPAs and Regional Government.

Financial and Asset Planning

Water Companies currently plan for Asset Management and the financial procurement required for this

through the Asset Management Plan (AMP) process which runs in 5 year cycles. The Office of Water

Services (OFWAT) is the economic regulator of the water and sewerage industry in England and Wales,

and regulates this overall process.




In order to undertake maintenance of its existing assets and to enable the building of new assets (asset

investment), Water Companies seek funding by charging customers according to the level of investment

they need to make. The process of determining how much asset investment required is undertaken in

conjunction with: the EA as the regulator determining investment required to improve the environment; the

Drinking Water Inspectorate (DWI) who determine where investment is required to improve quality of

drinking water; and OFWAT, who along with the EA require Water Companies to plan sufficiently to ensure

security of supply (of potable water) to customers during dry and normal years. The outcome is a

Business Plan which is produced by each Water Company setting out the required asset investment over

the next 5 year period, the justification for it and the price increases required to fund it.

Overall, the determination of how much Water Companies can charge its customers is undertaken by

OFWAT. OFWAT will consider the views of the Water Company, the other regulators (EA and DWI) and

consumer groups such as the Consumer Council for Water when determining the price limits it will allow a

Water Company to set in order to enable future asset investment. This process is known as the Price

Review (PR) and is undertaken in 5 year cycles. When OFWAT make a determination on a Water

Company’s business plan, the price limits are set for the proceeding five year period allowing the water

company to raise the funds required to undertake the necessary investment which will also be undertaken

in that 5 year planning period (the AMP period).

At the time of undertaking the Milton Keynes WCS, Water Companies are preparing for Price Review 2009

(PR09), whereby they are currently drafting their Strategic Business Plans which seek funding for asset

investment for the 5 year period covering 2010 – 2015 (known as AMP5).

It therefore follows that any new asset (or infrastructure) investment required to meet the requirements of

the WCS, needs to feed into the drafting of the Strategic Business Plan for PR09. OFWAT will determine

the final price limits from this process in November 2009. It can also be seen that, if significant WSI

requirements are not included in this current price review (PR09), the funding cannot be sought for it until

the next Price Review towards the end of AMP5 (PR14) which would result in funding not being available

until AMP6 running from 2015 -2020.

The WCS is therefore essential for several reasons:

• It allows the discrepancies in the planning timeframes of AWS and MKC to be reconciled through

strategic planning,

• It provides sufficient evidence base for MKCs statutory LDF process and robust evidence,

• It provides evidence for AWS Strategic Business Plans for investment required in AMP5 (2010-

2015) and beyond.




Water Resource Planning

Water Companies are now required to produce Water Resource Management Plans (WRMP) on a

statutory basis covering 25 year planning horizons. Previously, these plans have not been subject to

public consultation.

WRMPs set out how a water company plans to provide and invest in existing and new water resource

schemes (e.g. reservoirs, desalination) to meet increases in demand for potable supply, as a result of new

development, population growth and climate change over the next 25 year period. When complete, the

new statutory WRMPs will be updated in 5 yearly cycles to coincide with the Price Review and AMP

process.

At the time of undertaking the Stage 1 Milton Keynes WCS, the WRMP09 is undergoing public

consultation. Until such time as consultation is complete and the WRMP09 is approved and published in

2009, it is not possible to state with any certainty as to what options will be taken forward. However, data

from the previous WRMP (04) has been made available and AWS has provided updates on the latest

results from draft WRMP09.

It can therefore be seen that the WCS is crucial to bridging the gap between the LDF timeframe and the

AWS planning timeframe in terms of strategic planning for new water resources to meet development.

2.2.4 Funding Mechanisms

Once the WCS has determined the requirement for new infrastructure it will be necessary for the following

key stakeholders to agree to the WCS findings:

• MKC, MKP and EP - as the planning authority, delivery vehicle and landowners responsible for the

growth in Milton Keynes,

• EA – planning, water resources, ecology and flood risk consultee as well as regulator for water

quality,

• IDB – planning and flood risk consultee,

• AWS – as provider of wastewater and water supply infrastructure,

• NE – as statutory authority for protection of national and international sites of ecological interest and

conservation.

Having due regard to the planning timeframes there will need to be stakeholder agreement on what

infrastructure will be required (as recommended by the WCS) as well as when it will be required and how it

will be funded and maintained.




2.2.5 Water Framework Directive Planning

The WFD was passed into UK law in 2003. The overall requirement of the directive is that all river basins

must achieve “good ecological status” (or good ecological potential in the case of artificial or heavily

modified watercourses) by 2015 unless there are grounds for derogation. The WFD will, for the first time,

combine water quantity and water quality issues together. An integrated approach to the management of

all freshwater bodies, groundwaters, estuaries and coastal waters at the river basin level will be adopted.

It will effectively supersede all water related legislation which drives the existing licensing and consenting

framework in the UK.

UKTAG3, the advisory body responsible for the implementation of the WFD in the UK, has proposed water

quality, ecology, water abstraction and river flow standards to be adopted in order to ensure that

waterbodies in the UK (including groundwater) meet the required status. These are currently in draft form

and will not be formalised until the final River Basin Management Plans (RBMP) are finalised in December

2009 (prior to EU sign off). For this reason, it has not been possible to undertake a full assessment of the

impact of trying to meet the new WFD standards, which in many cases, are likely to be stricter and more

onerous to meet than those set by existing statutory targets and legislation. Despite this, the WCS is

required to consider the longer term issues with respect to the water cycle and water environment and as

such, an assessment of the impact of the interim WFD standards has been undertaken for this outline

study.

3 The United Kingdom Technical Advisory Group (UKTAG) is a working group of experts drawn from environment and conservation agencies. It was formed to provide technical advice to the UK’s government administrations and its own member agencies. The UKTAG also includes representatives from the Republic of Ireland.




3 Milton Keynes Growth Context

This Chapter describes the growth in Milton Keynes in more detail, specifically within the context of

assessing or ‘testing’ the options for growth in terms of impacts on and the requirements of the water cycle.

As explained, draft RSS 9 has set out the growth development targets for Milton Keynes and surrounding

areas to 2026. The SfG and Core Strategy production have included a broad scale assessment of the

various options for potential development areas in Milton Keynes and have identified those development

areas that have the potential to meet growth targets when considering all planning criteria.

It is important to note at this stage that the overall WCS is required to address, in detail, the additional

growth targets up to 2026 as set out in the draft SE Plan, but to also consider the WSI and impacts on the

water environment within the context of extrapolated growth up to 2031. This outline study has therefore

considered the development areas and infrastructure required for both the short and longer term

development aspirations for Milton Keynes.

3.1 New Housing Areas

The SfG (to 2026) for Milton Keynes pulls together information from previous studies and planning

documents including the Milton Keynes Local Plan.

However, for the purpose of this outline WCS and to better represent the proposed development (and

information obtained as part of this study), the following ‘broad’ study areas have been determined in

conjunction with MKC and MKP (Figure 3-1):

• Central Area,

• Eastern Area,

• Western Area,

• Northern Area,

• South Western Area,

• Land East of M1,

• Rural Areas (including Hanslope, Olney, Newport Pagnell and Castlethorpe).




These areas facilitate the incorporation of expansion areas, strategic reserve sites and rural housing sites

identified in the Local Plan; the longer term ‘Strategic Development Areas’ south east and south west,

urban intensification; and they allow for the consideration of phasing of development on an incremental

basis.

Central Area

This study area covers approximately 2,640 hectares and has outline planning permissions for

approximately 6,500 homes. Development proposals show major growth in the Central Area including infill

development and in total it is proposed that there will be maximum of approximately 14,350 new homes in

the Central Area up to 2026, plus a provision for 86 hectares of commercial land.

Eastern Area

This study area covers approximately 1,900 hectares including the Local Plan Eastern Expansion Area

(land between Broughton/Atterbury, the A421, the M1, and the Coachway at Junction 14 (M1)) and

Strategic Reserve Sites at Glebe Farm, Eagle Farm North and South, and Church Farm. Glebe Farm and

Eagle Farm South are south of the A421. Church Farm is south of Wavendon and east of the existing city

boundary. A Development Framework for the land north of the A421 (i.e. the Local Plan Eastern

Expansion Area) proposes approximately 4,000 homes, employment land, local centre, secondary school,

two primary schools and leisure and recreation open space (plus Eagle Farm North as an area of Strategic

Reserve). Following discussions and input from both MKC and MKP, it has been determined that there will

be a maximum total of approximately 13,000 new homes in the whole Eastern Area up to 2026 (including

5,600 within the administrative area of Mid Bedfordshire District Council as advocated in the RSS), plus a

provision for 53 hectares of commercial land.

Western Area

This study area covers approximately 1,800 hectares of land to the south of Stony Stratford, south west of

Two Mile Ash and north-west of Crownhill and Grange Farm (i.e. the Local Plan Western Expansion Area),

and includes part of the South West Expansion Area as identified in the SfG. The Development

Framework for the Local Plan Western Expansion Area includes approximately 6,000 homes, along with a

public transport route linking the area to the city centre, a local High Street, one secondary school, four

primary schools, 17 hectares of new employment land, open space, playing fields, allotments, community

and health facilities and a new burial ground and remembrance garden.




The area known as Stantonbury Park lies north of Wolverton Road and Stantonbury. The site is allocated

for about 500 homes and approximately 60 hectares of open space, which will contribute to a new country

park. The whole site covers an area of approximately 71 hectares.

Following discussions and input from both MKC and MKP, it is proposed that there will be a maximum total

of approximately 10,000 new homes in the Western Area up to 2026, plus a provision for 29 hectares of

commercial land.

Northern Area

This includes the smallest of the Local Plan expansion areas – the Northern Expansion Area. The

Northern Expansion Area lies immediately west of Newport Pagnell, between Wolverton Road, Little

Linford Lane and Linford Lakes - it includes the old Rocla Pipes site. The Northern Expansion Area

proposes 455 homes and also includes 3.4 hectares of employment land (next to the M1) and land where

a mixture of different uses are proposed.


of approximately 3,000 new homes in the whole of the Northern Area up to 2026, plus a provision for

3 hectares of commercial land.

Land East of M1

Discussions with MKC have revealed that following revisions of the South East Plan, an additional 5,600

dwellings are to be provided in the area to the east of the M1, including the existing settlements of Moulsoe

and North Crawley.

South Western Area

This study area covers approximately 2,191 hectares including the areas of Bletchley, Newton Longville

and also the South West Expansion Area as identified in the SfG, GVA Grimley Report and SFRA.


of approximately 9,000 new homes in the South Western Area up to 2026 (with 5,390 in Aylesbury Vale),

plus a provision for 3 hectares of commercial land.

Rural Areas

There are a small number of developments proposed to the rural settlements within the boundary of MKC.

Whilst only relatively minor development is proposed in the Local Plan and the Core Strategy Preferred

Options in and around Olney, Hanslope and Castlethorpe, consideration should still be given to the




potential cumulative effect upon the water cycle within Milton Keynes. Newport Pagnell is also considered

by MKC as a rural settlement.

Following discussions and input from both MKC and MKP, in total it is proposed that there will be a

maximum total of approximately 3,000 new homes in the Rural Areas up to 2026, plus a provision for

0.1 hectares of commercial land.

Summary

A summary of the proposed residential development numbers considered in this outline WCS are show in

Table 3-1.

Table 3-1: Potential Residential Development Numbers

Study Area Dwellings Population*

Central 14,350 32,862

Eastern 13,000 (inc 5,600 in Mid Beds) 29,770

South Western 9,000 (inc 5,390 in Aylesbury Vale) 20,610

Western 10,000 22,900

Northern 3,000 6,870

Land East of M1 5,600 12,824

Rural Settlements** 3,000 6,870

* Based on an occupancy rate of 2.29 (as agreed with MKC and MKP)

** Including Olney, Hanslope and Newport Pagnell

3.1.1 Infill Development

It is envisaged that approximately 14,350 new dwellings will be provided in the existing urban area of

Milton Keynes. It is proposed that the infill housing within the existing urban area will be supplied through

a combination of brownfield redevelopment (20% target), previously undeveloped land and redevelopment

of windfall sites.

By its nature infill development occurs on a partially ad hoc basis, as and when land becomes available,

therefore no definitive locations or growth targets for infill can be confirmed at this stage.

3.1.2 Marston Vale Eco-Town

The proposed Marston Vale Eco-Town is located to the east of the Milton Keynes study area and could

have a minor impact upon the water cycle regime of Milton Keynes, if it reaches the final shortlist. The

Eco-Town will need a new wastewater network, water supply and also generate surface water run off.




Existing masterplans for the Eco-Town suggest that due to the topography of the surrounding area, natural

drainage paths will be towards Bedford rather than Milton Keynes. An estimated 10% of the west of the

development may gravitate to Cotton Valley which would require infrastructure upgrades. Reference

should be made to the Outline WCS for Bedford and Mid Beds being undertaken by Bedford Renaissance.

The final decision on the future of the Eco-town is expected in early 2009.

Any new development on Greenfield sites increases surface water run-off. Although it is envisaged that by

the nature of the Eco-Town development, water recycling and water re-use would be encouraged. Also

the EA and IDB (in line with PPS25) would require that any additional surface water run off should be

attenuated to Greenfield rates, therefore there should be no net increase in surface water run off post

development (should the Eco-Town go ahead).

The CLG Eco-Town Prospectus states that Eco-Towns should be examples of best practice in the fields of

water and wastewater management. They should be working towards water neutrality and will utilise water

efficiency methods. This should therefore mean the Eco-Town places a minimal demand upon existing

water resources. If the Eco-Town is approved, then it will require its own WCS.

3.1.3 Development Scenarios – Housing

In undertaking the Milton Keynes WCS, it would be possible to assess potential broad development areas

individually; however, it is important to consider that there are numerous ways in which the development

can be brought forward in each area both in terms of numbers of housing, but also phasing of housing

development. This gives rise to potential development ‘scenarios’.

It is not possible to consider all the permutations for how housing could be brought forward in each of the

development areas and test each development scenario for implications to the water cycle within the

limitations of this study. In the main, this is due to time constraints, but also because not all of the

theoretical permutations for development would be possible due to other planning or sustainability reasons.

The WCS has therefore considered broad development scenarios to determine options for the phasing of

development. As such, the total growth for each development area has been split down into a number of

incremental steps (Table 3-2). This has allowed determination of constraints to development, both as a

baseline (existing) and then through a number of discrete growth steps.

For the purpose of the wastewater network analysis, the growth phases have been broken down further,

dependant upon the number of catchments draining each area. This has further helped with the

determination of the location of development within each area, thus highlighting where infrastructure

upgrades would be required and also determining sites which may be brought forward sooner (pre

infrastructure upgrades).




Table 3-2 Milton Keynes Development Scenarios

Growth Horizons* (Homes) Area

1 2 3 4

Central 0-3,600 3,600-7,200 7,200-10,800 10,800-14,400

Eastern 0-3,250 3,250-6,500 6,500-9,750 9,750-13,000

South Western 0-2,250 2,250-4,500 4,500-6,750 6,750-9,000

Western 0-2,500 2,500-5,000 5,000-7,500 7,500-10,000

Northern 0-750 750-1,500 1,500-2,250 2,250-3000

Land East of M1 0-1400 14,00-2,800 2,800-4200 4,200-5,600

Olney 0-375 375-750 750-1,125 1,125-1,500

Hanslope 0-375 375-750 750-1,125 1,125-1,500

* Arbitrary growth horizons have been determined based on a quarter split of total development

3.2 New Employment Areas

In addition to the proposed residential growth, there is a substantial amount of non-residential growth

proposed for Milton Keynes. In order to facilitate comparison with AWS data, non-residential development

in this report includes designated employment areas, commercial and community facilities.

The largest proposed employment area by far is in the Local Plan’s Eastern Expansion Area. There are

also other significant areas in the Local Plan’s Western Expansion Area, Shenley Wood and Tattenhoe

Park and the city centre.

Table 3-3 shows the amount of floorspace proposed in each of the development areas based upon the

employment land delivery programme supplied by EP.

Table 3-3: Non-residential Development by Area

Area Non-residential area (ha)

Central 86

Eastern 53

South Western 3

Western 29

Northern 3

Land East of M1 N/A

Rural Settlements 0.1

Until further breakdown (and details) can be determined for the proposed non-residential development,

broad assumptions have been required to determine the wider impacts on the water cycle.




4 WCS Methodology

Broadly, this outline WCS has been undertaken in three steps (1a, 1b and 2):

4.1 Step 1a / Step 1b: Baseline Conditions and Capacity

Before consideration is given to any new infrastructure required to service new development for each of

the development scenarios, it is important to consider the existing baseline with respect to the water cycle

environment and infrastructure. There are two key reasons for this:

• To allow identification of any potential flood risk constraints and water environment constraints which

would immediately restrict development of an area,

• To allow the identification of any spare capacity in the existing WSI; this would minimise the

requirement for new infrastructure.

The baseline and constraints assessment has been undertaken in two distinct stages:

• Step 1a: flood risk constraints are assessed for each development area in isolation,

• Step 1b: water cycle baseline (and constraints) are identified for each of the water cycle disciplines

(i.e. water resources, wastewater, etc.), with an assessment of the water environment baseline.

4.1.1 Constraints Matrix – Traffic Light Coding

Within each constraint category, a series of questions were formulated to identify for each of the study

areas, the relevant important constraints associated, given the present situation and infrastructure

provision. For the purpose of the constraints matrices these were amalgamated and put into generic

categories outlined in Table 4-1. Stage 2 of the WCS will further identify how and whether these

constraints can be overcome.




Table 4-1 Generalised Constraints Traffic Light Matrix

Flood Risk Water Resources Wastewater Environment

There is little or no perceived risk of flooding to the area.

There is existing raw water source nearby with spare license capacity. There is water available based on CAMS Methodology Classification. The Groundwater Vulnerability Classification - Low LP. The site is in Zone 3 groundwater source protection zone. The river quality classification is Good - A/B/C.

Where housing option can be accommodated within existing available headroom at WwTW and in sewers.

No environmental constraints were identified or when housing levels were considered sufficiently small that they were unlikely to materially increase impacts on European sites.

There is a perceived medium risk of flooding to the policy area. Floodplain is likely to intersect development areas.

There is an existing raw water source nearby but with no spare capacity. There is no water available based on CAMS Methodology Classification. The Groundwater Vulnerability Classification - Intermediate LP. The river quality classification is The site is in Zone 2 groundwater source protection zone.

Where WwTW has capacity to accommodate the proposed growth, but the sewers are unlikely to have capacity and therefore may need upgrading.

Medium risk of significant adverse effects as housing levels increase. Coding determined by lower level as a result of greater proximity to sensitive features or a greater degree of dependence upon WwTWs that are currently contributing to excessive phosphate loading*.

There is a perceived high risk of flooding to the policy area.

There is no existing raw water source nearby. There is an over abstracted/over License based on CAMS Methodology Classification. The Groundwater Vulnerability Classification - High LP. The site is in Zone 1 groundwater source protection zone.

Where major/significant upgrade of WwTW and/or sewers are required to accommodate the proposed growth.

High risk of significant adverse effects as housing levels increase. Coding determined by higher level as a result of greater proximity to sensitive features or a greater degree of dependence upon WwTWs that are currently contributing to excessive phosphate loading.

* It is not possible at this stage to accurately determine the level of housing that would lead to significant adverse effects on European sites. This would require further investigation at Stage 2 into (for example) likely degrees of increase in phosphate loading associated with levels of additional housing.

4.1.2 Constraints Matrix

The resultant outcome was the formulation of a constraints matrix for each of the study areas. This has

been completed for each of the housing options within each of the areas, and forms the background

behind the identification of preferred growth / phasing.

The matrix has been designed so that the amount of subjective interpretation of the questions is

minimised, and hence the traffic lights allocated are based on factual and quantitative data.




The number of dwellings which have been identified in the matrices have been based on an interpretation

of the data provided by MKC and MKP.

4.1.3 Use of the Matrix

The matrix is intended to provide a visual comparison of the appropriateness of development within each

of the study areas, with respect to the housing scenarios. For each of the scenarios, a traffic light is

applied, and the total number of “green” traffic lights can be directly compared to the total number of “red”

traffic lights. Areas with a majority of “green” boxes would be preferred, or could be taken forward with

minimal infrastructure work. Conversely areas with a majority of “red” boxes would require significant

upgrades in order to facilitate development. It is however important to note that the matrix is a ‘broad

brush’ summary, and that a detailed assessment should be undertaken as part of the detailed (stage 2)

study.

4.1.4 Summary Matrix

A summary matrix has been provided for each of the study areas (Section 12). These show the limiting

number of dwellings for each of the disciplines within each of the areas. The final limiting number will be

the lowest value of these and represents the development figure for each of these areas without significant

implications.

4.1.5 Constraints of the Matrix

Although the identification of the study areas can be undertaken through a visual comparison of the traffic

light systems, it should be recognised that a “red” light in one of the constraints may in effect over-ride all

other traffic lights (i.e. major ecological constraints may preclude/limit planned development, regardless of

prevailing factors).

4.2 Step 2: Water Services Infrastructure Development Options

This step considers the WSI options which could be taken forward in order to facilitate the growth as set

out in the development scenarios. Where Step 1 has identified a need for further infrastructure

development, strategic scale options are considered which could fill the gap to meet the development

targets and set out how these impact on each development scenario option to allow a comparative

assessment of the options for taking development forward with respect to the water cycle.




4.3 Data Limitations

Undertaking of the outline WCS has required a large amount of data collection and analysis, much of

which has been reliant on the willingness of third parties to supply in order to allow the study to be

progressed. In some cases, the availability of data with respect to WSI and future planning has not been

available within the time required to undertake the assessment. In such cases, various assumptions have

been used to enable the study to continue. Under each relevant topic, this report identifies what data has

been used in each assessment and identifies where assumptions have been adopted and the reasoning

behind these assumptions. Recommendations are also made for further, more detailed investigation in the

detailed study.




5 Flood Risk Baseline

A review of flood risk in the WCS is essential to ensure that:

• The risk of flooding to the broad growth areas is quantified and the development is steered away

from high risk areas (Flood Zone 2 and Flood Zone 3),

• Any flood mitigation measures are planned in a strategic manner,

• There is no deterioration to existing communities’ standard of protection.

5.1 Flood Risk Identification Methodology

The aim of identifying the potential sources of flood risk to the study areas is to assess the risks of all forms

of flooding to and from development, in order to identify any potential development constraints with respect

to flood risk. PPS25 emphasises the need for a risk-based approach to be adopted by LPAs through the

application of the Source-Pathway-Receptor model.

The Source-Pathway-Receptor model firstly identifies the causes or ‘sources’ of flooding to and from a

development. The identification is based on a review of local conditions and consideration of the effects of

climate change. The nature and likely extent of flooding arising from any one source is considered, e.g.

whether such flooding is likely to be localised or widespread. The presence of a flood source does not

always infer a risk. The exposure pathway or ‘flooding mechanism’ determines the risk to the receptor and

the effective consequence of exposure. For example, sewer flooding does not necessarily increase the

risk of flooding unless the sewer is local to the site and ground levels encourage surcharged water to

accumulate. The varying effect of flooding on the ‘receptors’ depends largely on the sensitivity of the

target. Receptors include any people or buildings within the range of the flood source, which are

connected to the source by a pathway.

In order for there to be a flood risk, all the elements of the model must be present. Furthermore effective

mitigation can be provided by removing one element of the model, for example by removing the pathway or

receptor. In the case of Milton Keynes, the general consensus is the receptor (i.e. new development) be

removed from the exposure pathway to a flood source




5.2 Available data and Assumptions

The assessment of flood risk constraints was made using of the draft Level 1 SFRA produced for MKC.

The draft Level 1 SFRA was drafted in March 2008 and covers an assessment of strategic flood risk in the

administrative area of Milton Keynes from all potential sources of flooding, including fluvial, groundwater

and overland flow. The draft Level 1 SFRA has been produced to allow MKC to undertake the PPS25

Sequential Test of potential development sites identified within their emerging LDF.

Information on potential SUDS utilisation has made use of Source Protection Zone (SPZ) information

produced and published by the EA and Groundwater Vulnerability Maps produced by the National Rivers

Authority (NRA).

Other Information Sources used include:

• Records of sewer flooding incidents (DG5) as reported to OFWAT and provided by AWS,

• Groundwater Vulnerability data from the EA.

5.3 Baseline Description

This assessment covers the risk of flooding and hence flood risk constraints posed to the potential

development sites. Flood risk generated as a result of the development (from surface water flooding) is

considered in Section 9 as this is considered on a development scenario basis and not as an absolute

constraint.

5.3.1 Fluvial Systems

The Milton Keynes WCS area covers the catchments of the River Great Ouse and River Ouzel. Tributaries

of these rivers include the River Tove, The Twins, Clipstone Brook, Loughton Brook, Tongwell Brook,

Water Eaton Brook and Broughton Brook. Rivers, floodplain and flood defences are mainly heavily

modified due to historic development, industry and agriculture. Table 5-1 provides an overview of the

major catchment characteristics.

The Milton Keynes SFRA4 and River Great Ouse CFMP

5 provide a more comprehensive assessment of

river catchment characteristics.

4 Milton Keynes Level 1 Strategic Flood Risk Assessment - Draft, Halcrow (March 2008) 5 River Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, Environment Agency (January 2007)




Table 5-1 Major Catchment Characteristics

Watercourse Major Tributaries Catchment Characteristics

River Great Ouse River Tove, The Twins,

Loughton Brook

Largely agricultural, main urban areas

are Milton Keynes and Newport

Pagnell

River Ouzel Clipstone Brook, Broughton

Brook

Largely rural catchment, main urban

area is Milton Keynes

5.3.2 Catchment Geology

Geology maps for the area show that the north of Milton Keynes District is underlain by a major aquifer

(predominantly limestone) of varying vulnerability. The bulk of the city limits is underlain by impermeable

Oxford bed clays with pockets of minor aquifer and river terrace deposits along the watercourse fringes.

The extreme south east corner of the district in the Woburn Sands area is underlain by a major aquifer

(Lower Greensand) of high vulnerability.

5.3.3 Flood Defences

There are some significant raised flood defences in Newport Pagnell, Middleton and Fenny Stratford. The

raised embankment at Kickles Bank has a design standard of 1 in 50 years, as have the raised

embankments Tongwell Brook along Willen Road, and on the Ouzel along Willen Road, Caldecotte Street

and Priory Street. As stated in the SFRA, the defences at Kickles bank are nominally 1 in 100 years as the

water levels of a 1 in 100 year event are approximately 60cm lower than the crest of the embankment.

The raised embankment at the EP site at Middleton has a SoP of 1 in 200 years.

Rivers, floodplain and flood defences are mainly heavily modified due to historic development, industry and

agriculture.

There is also a network of balancing lakes throughout the study area which through their attenuation,

ability to regulate flow and storage capacity provide an effective flood defence. The main lakes are

Caldecotte and Willen which regulate flow into the Ouzel. There are also significant balancing lakes on

Loughton and Tongwell Brook. Broughton Brook and Loughton Brook have both been reengineered to for

development to include lakes, two stage channels and contained floodplains.

5.3.4 Overland Flow

Overland flow is water that fails to infiltrate the surface and travels over the ground surface. Overland flow

can occur from significantly large areas of hardstanding, or from large areas of impermeable soil and or

geology which quickly become saturated during rainfall events. In general, these conditions need to be




combined with steep topography which can lead to rapid runoff from saturated (or impermeable) areas and

channel high flowing water to developed areas.

Stoke Goldington has a history of flooding by overland flow. Discussions with the IDB have also revealed

that the Caldecotte-Walnut Tree area suffers flooding.

5.4 Fluvial

Fluvial flood sources include sections of rivers not affected by the sea. The River Great Ouse flows to the

north and west of the study area, the River Ouzel flows to the south and east of the study area, Broughton

Brook flows to the east of the study area, Water Eaton Brook to the south of Milton Keynes, Tongwell

Brook to the north east of Milton Keynes, Chinchley Brook to the north east of the study area and Loughton

Brook to the west of the study area. The Flood Zones may be seen in the recently completed SFRA.

PPS25 defines three ‘flood risk zones’ with respect to fluvial flooding. The flood zones are classified in

terms of flood risk from rivers based on probability of a flood event occurring. The fluvial flood zones are

defined as:

• Zone 1 – Low Probability: land assessed as having a less than 1 in 1000 chance of river flooding

occurring in any given year (or a less than 0.1% annual probability),

• Zone 2 – Medium Probability: land assessed as having between 1 in 1000 and 1 in 100 chance of

river flooding occurring in any given year (or between 0.1% and 1% annual probability),

• Zone 3a – High Probability: land assessed as having a 1 in 100 or greater chance of river flooding

occurring in any given year (or greater than 1% annual probability),

• Zone 3b – Functional Floodplain: land where water has to flow or be stored in times of flood.

Generally, this is defined as land having a 1 in 20 or greater chance of flooding occurring in any

given year (or greater than 5% annual probability),

Figure 5-1 outlines the extent of the flood zones (from the draft Level 1 SFRA) in relation to the broad

growth areas for Milton Keynes.

For the purposes of the Level 1 SFRA, an agreement was reached with the EA over the use of proxy data.

The proxy’s considered were:

• Functional Floodplain (Flood Zone 3b) for Water Eaton Brook Flood Zone 3b was determined using

the 1 in 25 year modelled outline,




• Functional Floodplain (Flood Zone 3b) for the River Ouzel between Water Eaton and Caldecotte was

determined using the 1 in 50 year modelled outline,

• Functional Floodplain (Flood Zone 3b) for the remaining areas was determined using Flood Zone 3a

as a surrogate.

This may be amended in the Level 2 SFRA if necessary.

5.4.1 Climate Change

PPS25 requires developments in floodplains to consider the potential impacts of climate change on flood

risk for the lifetime of the proposed development.

EA guidance generally suggests that commercial developments should be considered to have a 60 year

design life, and residential developments should be considered to have a design life of 100 years. In

accordance with Annex B of PPS25, allowances for climate change should be made on fluvial flood

sources for a 60 year and 100 year design horizon. This requires an assessment of the impact of an

increase of 20% on peak river flows (or a 30% increase in rainfall intensity) for the design event being

considered. In this case, the peak river flows predicted during flood event with a return period (or

frequency) of 1 in 100 years needs to be increased by 20% (or rainfall intensity increased by 30%).

Where a modelled 1 in 1000 year outline exists (e.g. Water Eaton Brook), this has been used as a proxy

outline for Flood Zone 3a plus climate change. Elsewhere, the existing Flood Zone 2 has been used as a

proxy for Flood Zone 3a plus climate change.

Flood Zone 3a has been used as a proxy for Flood Zone 3b plus climate change.

5.4.2 Historical Flooding and Historical Flood Events

The draft Level 1 Milton Keynes SFRA has identified a number of historical events within the study area.

The following locations have been highlighted within the SFRA, through consultation with stakeholders,

through AWS data and the Stoke Goldington Flooding Investigation Report6 as having particular flooding

issues:

• Newport Pagnell,

• Stoke Goldington,

• Stony Stratford,

• Bletchley,

6 Stoke Goldington Flooding Investigation, WSP (October 2007)




• Woburn Sands,

• Bow Brickhill,

• Central Milton Keynes,

• Walnut Tree,

• Lower Weald

• Great Linford.

The following incidents have been recorded; however no severity rating, return period for the flood event or

details of antecedent conditions are available for these flood events:

• Newport Pagnell - 1947, 1992 and 1998,

• Stony Stratford - 1947,1998, 2003 and 2007,

• Bletchley - 1968, 1998 and 2006,

• Olney - 1947 and 1998,

• Fenny Stratford - 1947,

• New Bradwell - 1948, 1968 and 1998,

• Shenley Brook End - 1980,

• Walton Park - 2004 and 2007,

• Cosgrove - 1998,

• Ravenstone - 1980,

• Stoke Goldington - 1880, 1968, 1973, 1980, 1984, 2002 and 2007,

• Tathall End - 1973 and 2007,

• Woburn Sands - 2004.

5.4.3 Fluvial Flooding – Strategic Development Area Analysis

Central Area

The flood mapping from the draft Level 1 SFRA indicates that there are areas of flood risk (Flood Zones

3a, 3b and 2) along the eastern side of the town associated with the River Ouzel around Oakgrove, Walton

and Monkston Park. There is also an area of flood risk to the north west of the town near Bradwell. The




linear parks running alongside the River Ouzel should be retained and enhanced where possible. These

linear parks can act as a form of flood risk mitigation measure. Flood risk should not be a major constraint

to the proposed development within the Central Area as new development is unlikely to be permitted within

areas of Flood Zones as the river corridors are maintained as green infrastructure and due to surface water

attenuation prior to discharge.

Eastern Area

The flood mapping from the draft Level 1 SFRA indicates that there are areas of Flood Zone 2 and 3 in the

eastern study area. There are also two areas of Flood Zone 2, 3a and 3b within the council’s core

development area associated with Broughton Brook and the River Ouzel. Flood risk is not likely to be a

major constraint to development within the Eastern Area as the bulk of development is to be located away

from areas of Flood Zone 2, Flood Zone 3a and Flood Zone 3b. Also, the development framework for the

Eastern Expansion Area states that the linear park alongside Broughton Brook will be protected, offering a

form of flood risk management.

Western Area

There are areas of Flood Zone 2, 3a and 3b along the eastern edge around Shenley, Furzton and

Loughton, and the North Western Area around Stony Stratford and Calverton. These flood zones are

associated with Loughton Brook and the River Great Ouse. The core development area is however

outside of Flood Zones 2, 3a and 3b. Flood risk is therefore not considered to be a major constraint to the

proposed development within the Western Area due the very small area of the Expansion Area located

within Flood Zone 2 or 3, which is located to the extreme south and west of the area.

Northern Area

The draft Level 1 SFRA Flood Zone maps show that there are large areas of Flood Zone 2, 3a and 3b

within this study area. These Flood Zones are associated with the River Great Ouse and River Ouzel.

The core development areas are however situated outside of the Flood Zones. Given this, flood risk

should not be a major constraint to the proposed development within the Northern Area.

South-Western Area

The draft Level 1 SFRA flood mapping indicates that the southern half of the study area has areas of Flood

Zone 2, 3a and 3b adjacent to Water Eaton Brook, particularly in Water Eaton. It is however a narrow

Flood Zone immediately adjacent to the watercourse. Flood risk is not a major constraint to the proposed

development within the South Western Area as new development is unlikely to be permitted within Flood

Zones, any permitted development would need to incorporate flood resilience measures.




Land East of M1

There are areas of Flood Zone 2, Flood Zone 3a and Flood Zone 3b associated with Chicheley Brook and

the River Ouzel within the broad growth area. The main areas of fluvial flood risk are to the south of

Chicheley, Brook End, Crawley Grange and Newport Stables. Flood risk should not be a major constraint

to development within this expansion area as new development is unlikely to be permitted within flood risk

areas and any development that is, would need to incorporate effective flood resilience measures..

Rural Areas

The draft Level 1 SFRA flood mapping indicates that Olney has large areas of Flood Zone 2, 3a and 3b

associated with the River Great Ouse adjacent to the southern and eastern edges of the settlement. The

draft Level 1 SFRA Flood Zone maps show that there are large areas of Flood Zone 2, 3a and 3b around

Newport Pagnell. The settlement of Hanslope does not have any areas of Flood Zone 2 or 3 nearby and

so flood risk is not a constraint to proposed development in the Rural Areas.

It is important to note that through careful mitigation measures such as the EA have confirming that they

would not approve of development within the floodplain or as a justification to construct flood risk

management infrastructure, fluvial flooding need not be a major constraint to development in any of the

areas proposed for development in Milton Keynes. Maintenance and expansion or enhancement of the

linear green corridors adjacent to the watercourses in Milton Keynes, maintenance of Greenfield runoff

rates and application of other mitigation measures such as SUDS will also facilitate the removal of flood

risk as a major constraint, provided that greenfield runoff rates are maintained. More detailed assessment

of flood risk in each of the expansion areas can be found in Section 12.

5.5 Sewers

Normally, flooding from sewers occurs as a result of exceedance of the capacity of the sewer system from

heavy rainfall or if the system becomes blocked and will continue to remain flooded until the water drains

away. Modern sewer systems are typically designed to accommodate rainstorms with a 30 year return

period, whilst older sewer systems were often constructed without consideration of a design standard and

may in some areas (served by Victorian sewers) have an effective design standard of less than 30 years.

However, as the majority of the sewer network serving Milton Keynes is a separated system, then sewer

flooding issues can be split into two main groups:

• Foul sewer flooding – usually as a result of undersized pipes, blockages or constrictions. Where

there is an existing issue with the capacity of the network, any new connections without upgrades

will only make the situation worse.




• Surface water sewer flooding – usually as a result of incapacity in the system during intense

rainfall events which overwhelm the network (i.e. events with a return period greater than

1 in 30 years). The impacts of climate change are also leading to more surface water sewer flooding

in the UK, with milder, wetter winters and increased rainfall intensity in summer months likely to

become the norm.

In order to fulfil statutory commitments set by OFWAT, water companies must maintain verifiable records

of sewer flooding. The register of sewer flooding where caused by hydraulic incapacity is referred to as the

DG5 register.

DG5 register internal flooding is defined as flooding which enters a building or passes below a suspended

floor; whilst external flooding is defined as flooding which is not classed as internal. Properties at risk are

defined as properties that have suffered or are likely to suffer internal flooding from public foul, combined

or surface water sewers due to overloading of the sewerage system more frequently than the relevant

period. All flooding incidents should be registered by the water company irrespective of the severity of the

storm. For reporting purposes, buildings are restricted to those normally occupied and used for residential,

public, commercial, business or industrial purposes7.

The draft Level 1 SFRA for Milton Keynes noted that incidences of internal and external sewer flooding

have occurred in:

• Wolverton (4 records in DG5 Register),

• Bletchley (5 records in DG5 Register).

5.5.1 Sewer Flooding – Strategic Study Areas Analysis

A description of sewer flooding instances within each strategic study area has been undertaken below. It

is important to note that the data supplied was limited in detail and hence the exact nature and extent of all

events is in many circumstances is unknown.

Central Area

AWS data has identified instances of flooding in Bradwell Common, Heelands, Eaglestone, Bean Hill and

Springfield. The exact nature and extent of these events is not however known.

Eastern Area

AWS data has identified instances of flooding in Willen, Wavenden and Woburn Sands. The exact nature

and extent of these events is not however known. AWS have also confirmed that there are known issues

relating to the incapacity of the sewers in this area. 7 Environment Agency, Upper Mersey CFMP, May 2008




Western Area

AWS data has identified instances of flooding in Stony Stratford, Loughton and Shenley. The exact nature

and extent of these events is not however known.

Northern Area

The SFRA (through DG5 data) and additional AWS data has identified instances of sewer flooding in

Wolverton and other instances of flooding in Stantonbury and Great Linford. The exact nature and extent

of these events is not however known.

South Western Area


Bletchley and other instances of flooding in Fenny Stratford, Water Eaton and Newton Longville. The

exact nature and extent of these events is not however known.

Land East of M1

AWS data has identified instances of sewer flooding in Moulsoe. The exact nature and extent of these

events is not however known.

Rural Areas


Newport Pagnell. There is a risk of flooding from the lagoons at Newport Pagnell; however there are no

known artificial sources of flooding in Olney and Hanslope. There are no further recorded instances of

sewer flooding in the rural settlements of Olney or Hanslope.

Summary

Due to the nature of data supplied, it has not been possible to shown the instances of sewer flooding in

great detail. The SFRA should be referred to for greater detail.

5.6 Surface Water

Surface water flooding, also known as pluvial or overland flooding can occur as a result of a number of

factors. During periods of prolonged rainfall events and intense downpours, overland flow from adjacent

higher ground may ‘pond’ in low-lying areas of land without draining into watercourses, surface water

drainage systems or the ground. In general, surface water drainage systems are only required to be

designed to contain a 1 in 30 year rainfall event (as a maximum), during higher intensity events, surface

water drainage systems become overwhelmed often resulting in surface water flooding.




One of the main issues with surface water flooding is that in areas with no history, relatively small changes

to hard surfacing and surface gradients can cause flooding (garden loss and reuse of brownfield sites for

example). As a result, continuing development could mean that pluvial and surface water flooding can

become more frequent and although not on the same scale as fluvial flooding, it can still cause significant

disruption.

Historically the surface water generated as a result of development within Milton Keynes has been

attenuated via one of a number of attenuation lakes, prior to discharge into the watercourse network. The

lakes were designed to:

“avoid increasing flood risk through development……….…..the lakes have, subject

to certain conditions being met, a capacity sufficient for the long-term development

of Milton Keynes within the drainage area. The design standard was the 1947

flood that was, and remains, the most severe on record”8.

It should however be noted that whilst the surface water system for Milton Keynes was designed to the

1947 standard, this does not preclude the incorporation of new and specific surface water management

into new developments as the impacts of climate change and increase in population densities are

increasing the pressure upon surface water management within Milton Keynes. These measures are

necessary in the expansion areas and for sites outside the Designated Area (DA). The exact return period

of the 1947 event is also unknown and caution should be applied when considering this as a design

standard.

5.6.1 Surface Water Flooding – Strategic Study Areas Analysis

Central Area

There are several recorded instances of surface water flooding within the Central Area. The SFRA has

recorded instances in Conniburrow, Fishermead, Oldbrook, Beanhill and Netherfield.

Eastern Area

There are recorded instances of surface water flooding in Woburn Sands, Wavendon and Bow Brickhill.

The proposed core development area within the Eastern Area will primarily be constructed on Greenfield

land. Greenfield land is land that has never been built on or where the remains of any structure or activity

have blended into the landscape over time. The amount of impermeable land is therefore likely to increase

and it would be necessary to ensure SUDS techniques are employed and maintained to reduce runoff rate

to that of greenfield rate in any development. Greenfield run-off rate is the surface water drainage regime

from a site prior to development, or the existing conditions for brownfield redevelopment sites.

8 Drainage Strategy for Milton Keynes, Halcrow 2004




Western Area

There is a recorded instance of surface water flooding in Stony Stratford. The proposed core development

area within the Western Area will primarily be constructed on Greenfield land. The amount of impermeable

land will therefore increase and it would be prudent to ensure SUDS techniques are employed and

maintained to reduce runoff rate to that of greenfield rates to minimise any potential increase in surface

water runoff.

Northern Area

There are several recorded instances of surface water flooding in New Bradwell, Greenleys, Bradville,

Wolverton, and Great Linford. The proposed core development area within the Northern Area will primarily

be constructed on Greenfield land. The amount of impermeable land is therefore likely to increase and it

would be prudent to ensure SUDS techniques are employed and maintained to reduce runoff rates to that

of greenfield rate any potential increase in surface water runoff.

South Western Area

There are several recorded instances of surface water flooding in Bletchley. Any development on

Greenfield land will increase the amount of impermeable land and would therefore it would be important to

ensure SUDS techniques are employed and maintained to reduce runoff rate to that of greenfield rates to

minimise any potential increase in surface water runoff.

Land East of M1

According to the SFRA there are instances of surface water flooding in Moulsoe and North Crawley. Any

development on greenfield land will increase the amount of impermeable land and would therefore it would

be important to ensure SUDS techniques are employed and maintained to reduce runoff . These should

be limited to greenfield rates to minimise any potential increase in surface water runoff.

Rural Areas

There are several recorded instances of surface water flooding within the rural settlements. The SFRA

notes surface water flooding in Hanslope, Stoke Goldington, Castlethorpe, Newport Pagnell, Olney and

Weston Underwood. Any development on greenfield land will increase the proportion of impermeable

surfaces and it would therefore be important to ensure SUDS techniques are employed and maintained to

reduce runoff rate to that of greenfield rates to minimise any potential increase in surface water runoff.




5.7 Groundwater

Groundwater flooding occurs when groundwater levels rise above prevailing ground levels. The majority of

Milton Keynes city is situated above impermeable boulder clays meaning that groundwater flooding is

unlikely. The area to the north of Central Milton Keynes (around Hanslope and Olney), the area to the

north of Wolverton and the area around Woburn Sands are underlain by permeable geology (limestone

and Lower Greensand). The SFRA states that the IDB have expressed concerns that increased

development and use of infiltration SUDS in the area could lead to localised groundwater flooding.

5.7.1 Groundwater Flooding – Strategic Study Areas Analysis

Central Area

It is considered that the risk of groundwater flooding in Central Area are low due to the nature of the

underlying geology (relatively impermeable and clayey). There are narrow pockets of river terrace

deposits immediately adjacent to the watercourses which have a higher permeability but overall the risk of

groundwater flooding is considered to be low.

Eastern Area

The area around the settlement of Woburn Sands is underlain by permeable sands and gravels. There is

therefore a potential risk of groundwater flooding in the area, although there are no recorded instances.

Western Area

It is considered that the risk of groundwater flooding in the Western Area are low due to the underlying

geology being relatively impermeable (clayey). There are narrow pockets of river terrace deposits

immediately adjacent to Loughton Brook which have a higher permeability, however the risk of


Northern Area

It is considered that groundwater flood risk in the development areas in the Northern Area are low due to

the underlying geology being relatively impermeable (clayey). There are narrow pockets of river terrace

deposits immediately adjacent to the River Great Ouse and River Ouzel which have a higher permeability.

A small area of major aquifer also underlies the area to the north of Wolverton, however the risk of


South Western Area

It is considered that the risk of groundwater flooding in the South Western Area is low due to the underlying

geology being relatively impermeable (clayey). Towards the far east of the area, sands and gravels




become more prevalent and subsequently more permeable. Overall, groundwater flood risk is still

considered to be low.

Land East of M1

It is considered that groundwater flood risk in this expansion area is low due to the underlying geology

being relatively impermeable (Kellaway formation and Oxford Clay). The east of this area is overlain with

drift deposits of a till-diamicton mix.

Rural Areas

Hanslope, Newport Pagnell and Olney are underlain by large areas major aquifer (Oolitic Limestone) with a

high vulnerability meaning that there is a potential risk of groundwater flooding. However, there are no

recorded incidences of groundwater flooding.

5.8 Artificial Sources

Artificial flood sources include raised channels such as canals, or storage features such as ponds and

reservoirs. The SFRA identified that there was a breach of the Grand Union Canal in the Woughton Park

area of Milton Keynes in 1971 following third party work.

Breach or overtopping of reservoirs also poses a risk to development. There are thirteen reservoirs

located within the study area, where these have a perceived risk; more detailed analysis should be

undertaken as part of the Level 2 SFRA.

Central Area

The SFRA has identified that the Grand Union Canal runs through the Central Area and carries with it an

associated flood risk. The SFRA also points out that there was a reported breach of the canal in the

Woughton Park area following third party works.

There are also a number of reservoirs and ponds to the north east of the Central Area. Any major risk to

development should be identified and addressed either as part of the Level 2 SFRA or as part of a site

specific flood risk assessment (FRA).

Eastern Area

Willen Lake is situated in the north west of this area and carries a flood risk in the form of overtopping, or

potentially breach. Any major risk to development should be identified and addressed either as part of the

SFRA or as part of a site specific FRA.




Western Area

There are several reservoirs, ponds and lakes in the east and south east of this area which carry an

associated flood risk through overtopping, or potentially breach. Any major risk to development should be

identified and addressed either as part of the SFRA or as part of a site specific FRA.

Northern Area

There are numerous lakes and reservoirs in the north and west of the area. These waterbodies carry with

them an associated flood risk in the form of overtopping, or potentially breach. Any major risk to

development should be identified and addressed either as part of the SFRA or as part of a site specific

FRA.

South Western Area

There are several balancing ponds and lakes in the Bletchley and Newton Longville area which have an

associated flood risk. Any major risk to development should be identified and addressed either as part of

the SFRA or as part of a site specific FRA.

Land East of M1

There are no identified artificial sources of flooding within this expansion area.

Rural Areas

There is a risk of flooding from the lagoons at Newport Pagnell; however there are no known artificial

sources of flooding in Olney and Hanslope.

5.9 Flood Risk Constraints Summary

The assessment of flood risk undertaken for each study area at the present time, as a summary of the

constraint ranking is shown in Table 5-2, with a summary of the identified constraints shown in Table 5-3.

Table 5-2 Description of Colouring Assigned to Flood Risk Constraint Table

No / negligible issue – small scale management and mitigation may be required

Significant constraint – Feasible, but significant management and mitigation required

Major constraint




Table 5-3 Flood Risk Constraint Assessment

Area Fluvial Drainage / Surface

Water Groundwater Artificial Flooding

Central

Areas of Flood Zones 2

and 3 in the west of the

area associated with the

River Ouzel. Fluvial

flooding has occurred*

There are recorded

instances of surface water

flooding

Underlying geology is

predominantly impermeable

GUC runs along the

eastern edge of Central

Milton Keynes. There

are several lakes in the

area**

Eastern

Areas of FZ 2 and 3

affecting the northern part

of this area associated

with River Ouzel and

Broughton Brook*

There are recorded


flooding in the Woburn

area

Risk of groundwater flooding

around Woburn Sands site

associated with sandy

permeable geology

GUC runs along the

western edge of the

eastern expansion area.

There are several lakes

in the area**

Western

Areas of FZ 2 and 3 in the

east of the area

associated with Loughton

Brook*

There are recorded


flooding in Stony Stratford




in the area

Northern

Areas of FZ 2 and 3

associated with the River

Ouse*

Instances of sewer

flooding recorded in DG 5

register in Wolverton,

Low risk of groundwater

flooding associated with an

area of more permeable

geology to the north of

Wolverton


in the area

South

Western

Areas of FZ 2 and 3

affecting Water Eaton and

Caldecotte*

Instances of sewer

flooding recorded in DG 5

register in Bletchley




in the area

Land East

of M1

Areas of Flood Zone 2 and

3 associated with

Chicheley Brook

Surface water flooding in

Moulsoe and North

Crawley



No artificial sources

nearby

Rural

areas

Areas of FZ 2 and 3 in

Newport Pagnell, Olney

and Newton Blossomville*

Surface Water Flooding in

Newport Pagnell

Areas around Newport

Pagnell, Olney and Hanslope

are underlain by Oolitic

Limestone, which poses a

groundwater flooding risk

No artificial sources

nearby

* Even though parts of the broad development areas may fall within Flood Zone 3, the EA have confirmed that they would not approve

of development within the floodplain or as a justification to build defences. Therefore given this approach it is considered that fluvial

flood risk should not be considered as a major constraint to development.

** Through assessing any risk of flooding from artificial sources as part of the SFRA or site specific FRAs, any risk of flooding could

either be managed or mitigated.




It can be summarised that there are no overriding flood risk constraints to any of the study areas that would

require large-scale flood risk management or mitigation. There is little to differentiate between the areas,

but the following points can be made:

• The Rural Areas have less potential issues than the other areas,

• Fluvial flooding is not considered to be a significant constraint to development within Milton Keynes.

Even though parts of the study areas may fall within Flood Zone 3, the EA have confirmed that they

would not accept development within the floodplain or permit the construction of new flood risk

management infrastructure to facilitate development. The Green Infrastructure Study and the

Development Frameworks both emphasise the importance of the green corridors and recommends

that they should be maintained and enhanced,

• Surface water and drainage flooding has occurred on several occasions in the past throughout

Milton Keynes. Taking into account increases in development, development densities and climate

change predictions, it is likely that this type of flooding will increase in the future. Similarly older

surface water sewers (or combined networks) may be overwhelmed with the increased volume of

rainfall and sewer flooding may be experienced more frequently without network upgrades,

• Consideration should be given to the development of a surface water model for Milton Keynes as

part of the detailed (stage 2) WCS. It may also be prudent to undertake a Surface Water

Management Plan (SWMP) and network analysis, either as part of the detailed (stage 2) WCS, or in

parallel.

• Milton Keynes is based on strategic and integrated surface water and flood risk management

systems and SUDS

• It is also important that the MK WCS should link in to adjoining WCS’s to ensure a more regional

assessment of the water cycle is considered.

5.10 Data Limitations

In addition to any data limitations reported upon in the draft Level 1 SFRA, the only limitations determined

as part of the outline WCS are documented below:

• Functional Floodplain has mostly been mapped using proxies, with Flood Zone 3a typically being

used as a proxy for Flood Zone 3b. In the case of Milton Keynes, this has not been considered to be

too inhibitive as the EA are unlikely to support any proposed development in Flood Zone 3a,




• There are some areas which will require further modelling for impacts of climate change, although

where there is any major impact upon development sites it is likely that modelling would be

undertaken as part of the Level 2 SFRA,

• It has been considered that although the Level 1 SFRA is only at draft stage, given the initial

comments from the stakeholders, it is unlikely that there will be any significant changes. Any

significant changes to the Level 1 SFRA, will be considered and documented in the Final Outline

WCS (where appropriate).




6 Wastewater Baseline and Capacity

The wastewater baseline and capacity assessment addresses two key areas for wastewater. Firstly, the

baseline with respect to treatment of wastewater and how much ‘spare’ capacity is available in existing

wastewater treatment facilities; and secondly, the baseline with respect to sewer network and whether

there is scope to use the existing network system before upgrades are required. By the network system,

this assessment refers to the network of gravity sewers, pumping stations and associated rising mains

which are used to transmit wastewater from domestic and non-domestic developments to treatment

facilities.

It is important to establish an indication of flow consent capacity of wastewater treatment facilities to enable

any issues relating to flood risk and Water Framework Directive associated with an increase in the consent

to be assessed. Capital investment costs also need to be assessed as part of the evidence base for the

LDF process.

In order to give an indication of the relative sewerage infrastructure costs (which would be developer

funded through requisition) it is important to consider, where possible, the level of off-site upgrades

required.

A key priority of the WCS approach is the use of existing facilities, and where required, development of

strategic upgrades solutions. This is to reduce cost, reduce impact to existing communities and to allow

early phasing of some new development which will not have to rely on longer lead in times associated with

securing funding for new infrastructure through the statutory water company planning process. It is

important to note that there may be some WwTWs where there are major constraints to extension of the

works which may be associated with planning (e.g. odour impact), flood risk, land availability.

A critical aspect in assessing the spare capacity of the wastewater treatment facilities is the assessment of

the environmental capacity of the receiving watercourses. Discharge of additional treated wastewater from

new development could have a detrimental impact on:

• Water quality of receiving waters,

• Hydrological/hydraulic regime of receiving water’s and associated habitats,

• Flood risk downstream of the discharge associated with extending the WwTW,

• Flood risk associated with extending WwTW.

This assessment of environmental capacity with respect to wastewater discharge is included in this

section.




6.1 Available Data and Assumptions

6.1.1 Data

Various types of information have been supplied by AWS for the wastewater baseline assessment:

• WwTW population equivalent (PE), location and discharge consent details,

• Location of sewer flooding incidents (for cause see SFRA),

• Coverage of sewer network models,

• Sewer network records in GIS format. These show the layout of the sewer network and include

information such as sewer pipe sizes, sewer type, gradient etc,

• Information on existing capacity relating to all WwTWs.

6.1.2 Assumptions

The following assumptions have been considered whilst assessing the wastewater baseline and capacity:

• The per capita consumption (G - water used per head per day) is taken as 0.137 m3h

-1.d. This figure

is based on the year 2006-2007 AWS regional average for metered houses (assume all new

dwellings will be metered),

• The domestic populations (P) served by relevant WwTWs within Milton Keynes are those as

provided by AWS,

• Total population equivalent (PE) served includes trade effluent, holiday population and tanker

wastes and are those as provided by AWS,

• The average occupancy rate is 2.29 people per household (figure used by MKC),

• The infiltration (I) rate (defined as the amount of water that enters the drainage system from other

sources such as saturated ground, illegal connections and unaccounted drains) has been assumed

to be 25% (it has since been noted that AWS work on a figure of 45 l/c.d) of the Milton Keynes’

population multiplied by the per capita consumption9 (PG) for current and that for future calculation

of I, the additional Infiltration is calculated as 25% of future PG,

• From data provided by AWS, it would appear that the sewer network is predominantly a separated

system in Milton Keynes, i.e. foul water network is separate from surface water drainage network.

There is a predominantly combined system at Bletchley and Wolverton and therefore the risk of

9 Based on Office of Water Services (OFWAT) standards




surcharge from combined sewer overflows (CSO). AWS have indicated that the outlying towns and

villages have combined systems.

• No change in holiday or trade PE,

• It cannot be stated with any certainty as to how the increase employment (approximately 174 ha) is

to be defined and hence what affect it will have on increased trade flow. It has been assumed that

the mainly office type work and light industry and warehousing focus will result in a conservative

increase in trade flow of 30% above the current trade effluent total,

• In keeping with the requirements of PPS25 and EA policy, new development on existing Greenfield

sites will be required to provide sustainable drainage measures whereby runoff rates do not exceed

the Greenfield runoff rates. As such only increases in wastewater need to be considered in terms of

the impact on hydraulic capacity of the receiving water.

6.2 Wastewater Treatment Baseline and Capacity

6.2.1 Existing Waste Water Treatment Works

There are three main WwTW (Cotton Valley, Olney and Hanslope) that are most likely to be affected by the

proposed future development of Milton Keynes (due to the nature of the existing wastewater system),

these are summarised along with other WwTWs within the study area in Table 6-1. The locations of the

WwTWs are shown in Figure 6-1.

The largest, and most significant WwTW in terms of potential to accept additional influent, is Cotton Valley

WwTW. This currently serves 261,244 population equivalent (PE), and has a dwelling capacity estimated

from headroom on the consented flow of 55,560. This figure relates to the estimated flow headroom

available before a revised consent is required. It should be noted that AWS have worked on an occupancy

of 2.1 people per dwelling, compared to the figure of 2.29 used by MKC.




Table 6-1 : Waste Water Treatment Works within Milton Keynes

WwTW Domestic

PE

Total PE

(includes

trade PE)

Consented

DWF (m3

d-1

)

Estimated

actual DWF

(m3d

-1)

Approx

Dwelling

Capacity

OS NGR

Cotton Valley 218,961 261,244 78,000 53498 55,560 SP88474055

Olney 6,650 6,663 1,250 1728 0 SP88805280

Hanslope 2,155 2,216 840 507 755 SP79404740

Lavendon 1,223 1,223 295 223 163 SP91205250

Castlethorpe 998 1,031 151 138 29 SP79564375

Sherington 954 954 206 232 0 SP88094625

Ravenstone –

Stoke

Goldington

728 745 160 150 23 SP84764880

North Crawley 689 689 123 104 44 SP91444496

Newton

Blossomville 324 324 75 70 11 SP93125119

Weston

Underwood 162 162 - - - SP86745034

Filgrave 118 118 - - - SP86894832

Astwood 96 96 50 45 11 SP94864740

Wavendon –

Lower End 61 61 - - - SP92853773

Hardmead

(New) 42 42 - - - SP93824742

Great Linford 35 35 - - - SP85394282

Gayhurst 20 20 - - - SP85004670

Newport Pagnell

– London Road 29 29 - - - SP88714296

Whaddon 718 735 162 151 25 SP81223430

Drayton Parslow 555 555 106 98 18 SP84802870

Ducksworth 7 7 - - - SP96514784

NB WwTW with PE < 250 do not required a consented flow

6.2.2 Wastewater Treatment Capacity Assessment

Planned capital investment by AWS during AMP4 (2005 to 2010) is expected to ensure compliance with

effluent consent at Cotton Valley until at least 2021. The scope of works is to increase the hydraulic

capacity of the inlet works and re-commission secondary treatment activated sludge streams. The




anticipated overall effect of these works is to increase the overall design process capacity to approximately

340,000 PE (an increase of roughly 79,000 PE).

The phasing of growth (residential and commercial) is important. Broadly speaking, the AMP4 investment

at Cotton Valley is anticipated to satisfy about two thirds of the planned growth of Milton Keynes, which

should accommodate development to at least 2021.

The forgoing analysis does not include capacity and potential expansion of the smaller WwTWs in and

around Milton Keynes. These currently range from 7 PE to 6,000 PE and have a combined consented flow

capacity of 1,080 houses (approximately 2,200 PE). A sewage network analysis would be required to

investigate the feasibility for these respective works to accept additional influent.

It should also be noted that Olney and Hanslope WwTWs all have land available within their current

boundary for expansion.

Whilst these assumptions are acceptable for the Stage 1 WCS to determine the outline feasibility of using

the volumetric headroom at the WwTWs, any Stage 2 WCS will need to consider the ‘process’ capacity at

the WwTW as this could limit the extent to which the volumetric capacity can be utilised in the time before

funding is required to upgrade the WwTW. Any new upgrades or infrastructure requires funding to be

sought by AWS and as such, there is an associated lead in time for the upgrade works which would limit

the amount of development that could take place before the upgrades are in place.

Assumption sensitivity

The conclusions for the housing that can be accommodated by the existing capacity of the WwTW are

sensitive to assumptions applied to the calculations, and in particular to the assumption applied to the per

capita consumption. With the publication of the Code for Sustainable homes there is a considerable drive

to move towards more water efficient developments where water consumption is reduced by a number of

measures. A reduction in water usage would significantly reduce the wastewater generated from new

properties which could result in more properties being able to be connected prior to existing flow headroom

capacity being reached.

6.3 Wastewater Network Baseline and Capacity

6.3.1 Wastewater Network Baseline

AWS is responsible for the operation and maintenance of the existing foul drainage network and sewage

treatment facilities, within the Milton Keynes study area. The Milton Keynes study area is predominantly

served by a separate sewerage system which largely drains to Cotton Valley WwTW located to east of




Milton Keynes. It should be noted that, whilst Milton Keynes itself is nominally separate, the older outlying

towns and villages have combined (foul and surface water) systems. Figure 6-2 outlines the current layout

of pipe drainage within the Milton Keynes.

The initial starting point for the outline WCS was to determine the existing levels of wastewater conveyed

through the system in order to determine where there may be capacity issues both now and also in respect

to the proposed development within Milton Keynes.

The initial capacity assessments may help with guiding development proposals away from areas where

there are capacity issues, which would mean major capital investment and/or disruption for upgrades

necessary to serve new sites. Given that the majority of the sewer network serving Milton Keynes is a

separated system, the effects of increased flows due to climate change have not been considered to be a

major issue.

Drainage paths and catchments were determined for all of the development areas, in some cases the

development areas were further sub-divided based on their catchment characteristics.

High level preliminary assessments of the capacities of these drainage paths were then undertaken

(Appendix B). This was undertaken to provide an indication of whether it is feasible to drain any of the

proposed growth locations via the existing network.

With regards to addressing constraints within the wastewater network, the following has been considered:

• Minor Constraint – Less than 10% of network showing capacity issues,

• Significant Constraint – Between 10% and 30% of network showing capacity issues,

• Major Constraint – Greater than 30% of network showing capacity issues.

An assessment of each area is shown below. Further details are included in Section 12.

Central Area – Western

The initial assessment has shown that, in general the network draining the west of the Central Area, has

capacity to service the proposed growth up to the upper growth targets, per area, as tested in Section 12).

The assessments have highlighted that 18% of the network currently has capacity issues; however the

majority of the system would likely be able to accommodate in excess of 4,500 homes.

Central Area – North East

That initial assessment has shown that there are major capacity issues in the network draining the north

eastern part of Milton Keynes. The initial assessments show that 56% of the network is currently suffering

from capacity issues. Without improvements works, further development in this area would only




exacerbate the problem. The remainder of the network appears to have sufficient capacity to

accommodate in excess of 4,500 homes within the north eastern part of the Central Area.

Central Area – South East

The initial assessment has shown that the network draining the south eastern part of the Central Area

generally has capacity to service the proposed growth up to the maximum growth targets. The

assessments have highlighted that 23% of the network currently has capacity issues; however the majority

of the system (circa 76%) would likely be able to accommodate in excess of 4,500 homes.

Eastern Area – South

The initial assessment has shown that approximately 39% of the network draining the southern part of the

Eastern Area suffers from capacity issues. Works will be required to address these capacity issues prior to

the proposed development in the area taking place. The remainder of the system is likely to have capacity

to accommodate growth up to 6,500 homes.

Within the administrative area of Milton Keynes, extensions have already been carried out under

requisition to serve the Wavendon and Eagle Farm sites. However extensions to the Broughton Brook

sewer will be required for development within Mid-Bedfordshire.

East Area – North

The initial assessment has shown that the entire system draining the northern part of the eastern study

area has sufficient capacity to accommodate growth up to the higher growth target of 6,500 homes.

Indeed, from the testing it would appear that there is capacity within the network serving the area for up to

20,500 new homes. Upgrading to inlet works due for completion by March 2009 will greatly improve the

capacity situation in the sewer system, particularly in the Broughton Brook area.

Western Area – North

The initial assessment has shown that approximately 40% of the network draining the northern part of the

western study area suffers from capacity issues. Works will be required to address these capacity issues

prior to the proposed development in the area taking place. Of the remainder of the system, 53% of the

system is likely to have capacity to accommodate growth up to 3,500 homes.

AWS are currently appraising the upgrade requirements to serve the Western Expansion Area, it is

expected that the area will require new pumping stations and sewers to transfer the point of connection to

existing network.




Western Area – Central

The initial assessment has shown that approximately 22% of the network draining the northern part of the

Western Area suffers from capacity issues. Works will be required to address these capacity issues prior

to the proposed development in the area taking place. Of the remainder of the system, 65% of the system

is likely to have capacity to accommodate growth up to 3,500 homes.

Western Area – South

The initial assessment has shown that the network draining the southern part of the Western Area

generally has capacity to service the proposed growth up to the maximum growth targets. The

assessments have highlighted that 5% of the network currently has capacity issues; however the majority

of the system is likely to accommodate in excess of 3,500 homes.

Northern Area – East

The initial assessment has shown that the network draining the eastern part of the Northern Area generally

has capacity to service the proposed growth up to the maximum growth targets. The assessments have

highlighted that 25% of the network currently has capacity issues; however 75% of the system would likely

be able to accommodate in excess of 1,300 homes.

Although more detailed modelling undertaken by AWS has confirmed that there are no issues in this area.

This should be confirmed as part of the detailed study.

Northern Area – West

The initial assessment has shown that the entire system draining the western part of the Northern Area has

sufficient capacity to accommodate growth up to 1,300 homes. The pipe with the lowest capacity in the

system would likely be able to accommodate the entire growth for the northern development area.

South Western Area

The initial assessment has shown that the entire system draining the South Western Area is likely to have

sufficient capacity to accommodate growth up to 9,000 homes. The pipe with the lowest capacity in the

system would accommodate growth up to 7,000 homes.

Land East of M1

The initial assessment has shown approximately 67% of the network currently has capacity issues, with

only 2% of the network able to accommodate up to 1,500 homes. Major infrastructure upgrades would be

required to support the proposed growth.




Upgrade option would mean have to transfer via the Newport Pagnell system which has capacity issues

and also CSO discharges. Almost definitely would be looking at new direct connection to Cotton Valley

Rural Areas – Olney

The wastewater network serving Olney is a pumped system. At this stage it has been assumed that

through increasing the pumping rates or pump durations, initial growth in Olney could be handled by the

existing system. This would need to be considered in more detail during the detailed stage of the WCS.

In the longer term upgrades to the system may be required.

AWS have confirmed they do not have any model coverage for Olney.

Rural Areas – Hanslope

Initial calculations have shown that there is insufficient capacity in 75% of the network currently serving

Hanslope, although this may be exacerbated by missing data (30% of pipes have insufficient data to

assess and have therefore been flagged as having incapacity at this stage). Only 15% of the network is

shown to have network to facilitate the maximum growth figures for Hanslope.

Therefore further investigation of the wastewater network is required in Hanslope to provide the coverage

for the proposed growth.

6.3.2 Wastewater Constraints Summary

The determination of constraints considered for the wastewater network are shown in Table 6-2, with the

assessment of the wastewater network summarised in Table 6-3.

Table 6-2: Description of Colouring Assigned to Wastewater Network Constraint Table

Minor constraint (less than 10% of network at capacity)

Significant constraint between 10% and 30% of network at capacity)

Major constraint (more than 30% of network at capacity)




Table 6-3: Wastewater Network Constraint Assessment

Growth Horizon Study Area

Existing 1 2 3 4

West - 0-1,200 1,200-2,400 2,400-3,600 3,600-4,800

South East - 0-1,200 1,200-2,400 2,400-3,600 3,600-4,800 Central

North East - 0-1,200 1,200-2,400 2,400-3,600 3,600-4,800

North - 0-1,625 1,625-3,250 3,250-4,875 4,875-6,500 Eastern

South - 0-1,625 1,625-3,250 3,250-4,875 4,875-6,500

North - 0-875 875-1,750 1,750-2,625 2,625-3,500

Central - 0-875 875-1,750 1,750-2,625 2,625-3,500 Western

South - 0-875 875-1,750 1,750-2,625 2,625-3,500

East - 0-375 375-750 750-1125 1125-1,500 Northern

West - 0-375 375-750 750-1125 1125-1,500

South Western - 0-2,250 2,250-4,500 4,500-6,750 6,750-9,000

Land East of M1 - 0-1,500 1,500-3,000 3,000-4,500 4,500-6,000

Olney - 0-375 375-750 750-1,125 1,125-1,500 Rural

Hanslope - 0-375 375-750 750-1,125 1,125-1,500

6.3.3 Wastewater Network Modelling

The high level assessments have only considered the impacts of development in each of the study areas

and sub-areas on an independent basis. Further capacity issues may be highlighted when considering the

cumulative effect of drainage systems which join further down the system.

Without more detailed investigation, there is considerable uncertainty to the level of the effects of this

potential problem and it is recommended that wastewater modelling is considered (where feasible and

model coverage is available) to verify this as part of the detailed WCS.

6.4 Wastewater Environment Baseline

6.4.1 Water Environment Data

The Water Quality assessment has made use of water quality data collected and supplied by the

Environment Agency, along with information on the legislation which drives the water quality standards

required to protect ecological habitat integrity for the river systems.

The hydraulic capacity has been undertaken at a high level and has compared existing discharges from

Cotton Valley and likely increases in discharges with peak flows in the River Ouzel and River Great Ouse.




Increased effluent discharges to the River Ouzel and River Great Ouse will impact on flood risk and water

quality. Before approving increases in consented discharges to these rivers, the EA will require further

catchment modelling to identify any necessary mitigation works particularly with reference to the lakes in

Milton Keynes. This should either be included in the detailed stage of the water cycle study, the Level 2

SFRA or as an independent study for example a surface water management plan.

In terms of the wider water related environment, the outline WCS has undertaken the initial screening

stages of an Appropriate Assessment10

to identify whether the water cycle and water infrastructure

changes assessed in the WCS are likely to have a detrimental impact on the habitats of European

designated sites of nature conservation. This screening study undertook a review of all designated sites

(European, national and regional/local) that are hydrologically linked to watercourses or aquifers potentially

affected by development in Milton Keynes.

At this stage in the WCS assessment, a review of water-related environment baseline with respect to

wastewater discharges is essential to ensure that:

• The water related environment has the capacity to absorb further discharges to the receiving

watercourse,

• There are no absolute constraints in terms of the water environment baseline (i.e. unacceptable

increase in flood risk),

• There is no unacceptable deterioration in the quality of the water related environment.

The assessment of the water environment baseline has considered the capacity issues associated with the

ability of receiving watercourses to accept further discharges of treated wastewater from the new

development. This assessment has been undertaken for the impacts locally on the river systems, but also

on hydrologically linked sites designated for ecological and conservation reasons.

An assessment of the capacity of water resources for further abstraction has been undertaken separately

and described in Section 7.

6.5 Water Quality Baseline and Capacity

6.5.1 Water Quality Legislation, Guidelines and Monitoring

There are several Statutory and Guideline documents that are designed to protect water quality and

aquatic ecology, ranging from legislation with which to assess pollution from pesticides and other

10 The need for Appropriate Assessment is set out within Article 6 of the EC Habitats Directive 1992, and interpreted into British law by Regulation 48 of the Conservation (Natural Habitats &c) Regulations 1994




substances, to limits for bacteriological quality of water for bathing and shellfisheries. The most ubiquitous

water quality information for surface waters is the EA River Ecosystem (RE) scheme, which is supported

by monitoring programmes for basic chemical and biological parameters under the General Quality

Assessment Scheme (GQA). An explanation of the RE/GQA scheme is given here, before describing

some changes in water monitoring that are being introduced as part of the Water Framework Directive

(WFD) implementation in Section 11. To enable ease of comparison, the current water quality of the

Rivers Great Ouse and Ouzel is described fully in Section 11.2.1. This is to enable the impact of likely

future standards to be assessed easily against existing standards. This introduction is intended to aid the

interpretation of water quality data in the Milton Keynes area, and to indicate possible future water quality

impacts.

RQO’s are targets used to help protect and improve the quality of the water in watercourses. Each stretch

of river is given a target from the EA River Ecosystem Classification scheme. These range from very good

quality (suitable for all fish species) to poor quality (likely to limit fish species). If a river achieves this target

it means that the river will be of adequate quality to support a certain type of ecosystem. The EA would

also be confident that the river would meet the requirements for wildlife, conservation, recreation and

abstraction for other purposes.

In terms of chemistry, a suite of eight determinands is used for river quality objectives, but a more limited

list of three key determinands is selected for the purpose of compliance trends: biochemical oxygen

demand, dissolved oxygen and ammonia. However, the EA recognise that ‘spot’ samples only provide an

estimate of the underlying quality of the water being sampled. Therefore, the confidence limits within

which the ‘real’ quality is assumed to lie are calculated. The level of confidence chosen for assessment of

compliance with river quality objectives is 95%. The chemical determinands are described using the GQA

scheme, described below.

6.5.2 Chemical GQA Scheme, Guidelines and Standards

The EA grades the chemical quality of rivers using the GQA scheme, which is designed to provide an

accurate and consistent assessment of the state of water quality in rivers over time. Sites are sampled a

minimum of 12 times a year for determinands shown in Table 6-4. The EA uses the data collected over

three years because this produces 36 samples per site, giving the required precision in making judgments

about particular rivers from point sources of pollution, balanced against the cost of monitoring and

resources needed for water quality sampling.




Table 6-4: Environment Agency chemical GQA grades in watercourses

mg N L-1

90 percentileGQA

grade

Dissolved Oxygen

(% saturation)

10 percentile

BOD

mg Lmgl-1

90 percentile

Ammonia

mgNl-1

90 percentile

A 80 2.5 0.25

B 70 4 0.6

C 60 6 1.3

D 50 8 2.5

E 20 15 9.0

F <20 >15 >9.0

The overall scheme also includes a biological assessment, in which macroinvertebrates in the river are

compared with the likely assemblage if the river was not impacted, and assigned a grade (Table 6-5).

Flow and morphology are taken into account. Two biological samples are collected, one in spring (March

to May) and one in autumn (September to November). Complete national surveys were carried out in

1990, 1995 and 2002. From 2002 the EA began to sample one third of sites each year, so that every site

is sampled once in three years. The reported results use the most recent data at each sampling site.

Table 6-5: Biological Monitoring Grades

Classification Description

A – very good Biology similar to that expected for an unpolluted river

B – good Biology is a little short of an unpolluted river

C – fairly good Biology worse than expected for unpolluted river

D – fair A range of pollution tolerant species present

E – poor Biology restricted to pollution tolerant species

F – bad Biology limited to a small number of species very tolerant of pollution

The routine EA samples are not flow-based, and have historically been collected primarily to support

monitoring of point-source emissions to water, such as WwTWs. Thus, storm events, which drive most

diffuse pollutant transport mechanisms, are not specifically sampled, and the concentrations reported will

be a gross underestimate of the peak, albeit usually transient, concentrations. Approximately 90% of

diffuse water pollution will occur during high flow following intense or prolonged rainfall and these periods

can impact water quality to the detriment of river health, or raw-water abstracted for potable treatment.

However, these events are rarely captured by routine monitoring programmes.

Flow-based monitoring to fully assess water quality in watercourses during storm events at sufficient

temporal and spatial resolution is resource intensive and is currently not practiced on a routine basis.

However, advances in monitoring equipment are changing the nature of water quality monitoring.




Investigative monitoring for selected water quality determinands can be conducted using auto samplers,

semi-continuous water quality probes or a combination of both.

6.5.3 Nutrients

The two most important nutrients in terms of eutrophication, nitrogen (N) and phosphorus (P) are assessed

using a separate GQA to other chemical parameters. Table 6-6 shows the GQA Grades for these nutrients

used by the EA.

Table 6-6: Environment Agency nutrient GQA grades

Classification for

phosphate

Grade limit

(mgP/I) average Description

1 0.02 Very low

2 0.06 Low

3 0.1 Moderate

4 0.2 High

5 1.0 Very high

6 >1.0 Excessively high

Classification for nitrate Grade limit

(mg NO3/I) average Description

1 5 Very low

2 10 Low

3 20 Moderately low

4 30 Moderate

5 40 High

6 >40 Very high

Of all forms of P, it is desirable to determine the concentrations of Soluble Reactive Phosphorus (SRP) as

this form of P is most immediately available to aquatic macrophytes and algae. Phosphorus is usually the

limiting nutrient in inland freshwaters and gives an indication of the likelihood of eutrophication within a

water environment. There are guidelines on concentrations that should occur to protect the overall health

of the waterbody, as shown in Table 6-7. Some sources of P to waterbodies are regulated by legislation,

such as discharges from WwTWs (Urban Wastewater Treatment Directive, (91/271/EEC).

The Urban Waste Water Treatment Directive (UWWTD) was agreed in 1991. The UWWTD has

requirements for sewerage collection and sets standards for sewage treatment. The general principle of

the Directive is to provide treatment of sewage from the largest discharges first, and to protect sensitive

waters. Areas are designated under the Directive according to three criteria: (a) waters that are, or have

the potential to become, eutrophic if no protective action is taken. (b) drinking water sources that contain or




could contain more than 50mg/l of nitrate if no protective action is taken. (c) waters in need of protective

action to meet the requirements of other Directives. Waste water discharges over 10,000 PE that

discharge to Sensitive Areas need treatment that relates to the designation criterion or criteria as outlined

in Table 6-7.

Currently in the Milton Keynes study area, although the Rivers Ouse and Ouzel are designated Sensitive

under the UWWTD, only Cotton Valley WwTW has a PE sufficient to qualify under the legislation.

However, to consider the water environment effectively, a catchment approach should be considered.

There are several WwTWs upstream of Milton Keynes e.g. Dunstable, Leighton Linslade and Buckingham,

and these should also be considered in any more detailed analysis of water quality. All of these works are

over 10,000 PE and therefore have target concentrations of total phosphorus of 2.0 mg/l, as shown in

Table 6-7.

Table 6-7: Provisions for Sensitive Areas under the UWWTD

Total nitrogen Concentration (mg/l) Reduction (%)

10,000 to 100,000 PE 15

>100,000 PE 10 70-80

Total phosphorus Concentration (mg/l) Reduction (%)

10,000 to 100,000 PE 2

>100,000 PE 1 80

By contrast to phosphorus, concentrations of nitrogen in inland waterbodies, in the form of nitrate

(expressed as either NO3 or NO3-N), are directly affected by legislation. The EC Nitrates Directive

91/676/EEC aims to reduce nitrate pollution from agriculture and there is legislation to regulate the amount

of NO3 emissions to water from point sources, such as WwTW’s. The objective is to reduce the problem

of eutrophication in surface waters and to limit the concentration of nitrate in drinking water from both

ground and surface water. The Directive does not itself set mandatory standards but relies on other

legislation. The Surface Water Directive, 75/440/EEC, specifies a mandatory limit of 11.3 mg/l NO3-N (50

mg/l NO3), while the Drinking Water Directive, 80/778/EEC, sets the same mandatory value for human

consumption via water.

6.4.2 Relationship between River Ecosystem RQO and GQA grades

Compliance with the RQO is assessed on a 3 year rolling basis from the GQA routine monitoring

undertaken by the Environment Agency. Although methods of calculation and standards are not identical,

GQA Grade A is approximately equivalent to RE1 etc, as shown in Table 6-8.




Table 6-8: Relationship between GQA and RQO/RE Grades

GQA RQO (RE) Ecological Status

A RE1 Excellent

B RE2 Good

C RE3 Moderate

D RE4 Poor

E RE5 Unsuitable

6.5.4 Sediment

Sediment is especially important in the water environment, yet it can be complicated to assess. The

Freshwater Fish Directive (78/659/EEC) gives a guideline value of 25 mg/l for suspended sediment in

rivers for salmonid fisheries. The concentrations of suspended sediment in streamflow are directly related

to velocity and available substrate for suspension. Sediment may be re-suspended from the stream-bed,

or derived directly from soil erosion during rainfall. Suspended sediment can cause several direct

problems, such as reduce light penetration affecting photosynthesis or siltation of spawning gravels, as

well as carrying adsorbed substances such as P, metals or sediment bound pesticides, such as the

insecticide cypermethrin.

The type of standard set in the Freshwater Fish Directive, as an annual mean concentration, is almost

meaningless for sediment management in the context of the achievement of ecological objectives because

of the aforementioned spatial and temporal variability of sediment, and the need to identify issues of

excess (and deficit of) sediment. It is also not the most appropriate for tackling sediment pollution

problems such as those caused by occasional events; for example diffuse pollution from land during storm

events. Therefore, Casper and Jensen (2007), consider there is a dual need; for standards that tackle

sediment as a diffuse pollution issue and define conditions for good sediment habitat supportive of

ecological objectives, and a regime that can also manage specific risks. Accordingly, Natural England

recommends that different river types need different sediment levels for effective ecological functioning.

6.5.5 Receiving Watercourse - Baseline and Capacity

The River Ouzel is heavily engineered and it is likely that any increase in discharges from Cotton Valley as

a consequence of the proposed development within Milton Keynes would not have a detrimental effect in

terms of capacity.

However the River Ouzel discharges to the River Great Ouse at Newport Pagnell and the EA have

expressed concerns about the increased risk of flooding at Newport Pagnell as a result in an increase in

discharge from Cotton Valley.




The EA have confirmed that they would not wish to see any net increase in discharges, which would

increase flood risk at Newport Pagnell. Increased effluent discharges to the River Ouzel and River Great

Ouse would impact on flood risk and water quality. Before approving increases in consented discharges to

these rivers, the EA will require further catchment modelling to identify any necessary mitigation works

particularly with reference to the lakes in Milton Keynes. This should either be included in the detailed

stage of the water cycle study, the Level 2 SFRA or as an independent study for example a surface water

management plan.

For water quality, the EA position has been that any increase in flows from WwTWs that occur as a result

of growth must comply with their policy on No Deterioration. This requires that increases in failure of a

mandatory standard caused by growth should be offset by reducing the consent limits of the associated

discharge(s). The policy allows the EA to impose consent limits up to the limit of “best available

technology not entailing excessive cost” (BATNEEC). It also allows the EA to make special justification for

imposing consent limits more stringent than BATNEEC.

An initial estimation of peak flood flows for both the River Ouzel (at the Cotton Valley discharge location)

and River Great Ouse (immediately downstream of confluence with the River Ouzel) have been

undertaken using the Flood Estimation Handbook (FEH) Statistical Method and Revitalised Flood

Hydrograph (ReFH) Method, these are shown in Table 6-9. These independently derived flows should be

compared against any available existing data (i.e. EA models).

Table 6-9: River Ouzel - Peak Flow Estimates

Peak flows Event Return Period

FEH Statistical ReFH

95% Exceedance (Q95)* 0.47 m3s

-1

Mean Flow* 2.03 m3s

-1

10% Exceedance (Q10)* 4.47 m3s

-1

2 year 26.2 m3s

-1 35.0 m

3s

-1

10 year 44.6 m3s

-1 51.5 m

3s

-1

50 year 61.4 m3s

-1 69.4 m

3s

-1

100 year 69.1 m3s

-1 79.7 m

3s

-1

100 year plus climate change 82.9 m3s

-1 95.6 m

3s

-1

1000 year 98.2 m3s

-1 135.2 m

3s

-1

* Information from gauging station data on www.nwl.ac.uk for River (Bedford) Ouse at Newport

Pagnell (33037)




Table 6-10: River Great Ouse - Peak Flow Estimates Peak flows

Event Return Period FEH Statistical ReFH

95% Exceedance (Q95)** 0.39 m3s

-1

Mean Flow** 4.41 m3s

-1

10% Exceedance (Q10)** 11.11 m3s

-1

2 year 91.6 m3s

-1 128.9 m

3s

-1

10 year 148.3 m3s

-1 185.1 m

3s

-1

50 year 205.4 m3s

-1 243.5 m

3s

-1

100 year 233.2 m3s

-1 276.5 m

3s

-1

100 year plus climate change 279.9 m3s

-1 331.8 m

3s

-1

1000 year 346.3 m3s

-1 449.4 m

3s

-1

** Information from gauging station data on www.nwl.ac.uk for River Ouzel at Willen (33015)

The current estimated DWF from Cotton Valley WwTW as provided by AWS is 78,000 m3d

-1, which

equates to a flow rate of 0.90 m3s

-1. An initial estimate of the increase in DWF, post development in Milton

Keynes (considering the highest growth estimates) has shown an increase of 0.36 m3s

-1.

The increase in DWF equates to 8% of the mean flow within the River Great Ouse and 18% of the mean

flow in the River Ouzel. During flood events, the increase in DWF equates to 0.15% of the estimated

1 in 100 year flow in the River Great Ouse and 0.52% of the 1 in 100 year flow in the River Ouzel (based

on FEH statistical flow estimates). The detailed WCS should consider the effects of these increased flows

in more detail. This may include re-running of existing hydraulic models.

6.5.6 Habitats Regulation Assessment

The initial stages (screening stages) of a Habitats Regulation Assessment as required under the Habitats

Directive have been undertaken for the outline WCS (Section 10). Until the development areas and

development scenarios are agreed in detail following review of all planning considerations, it is not possible

to complete a full “Appropriate Assessment” (AA) on the WCS to determine the full impact on designated

European Sites (such as SACs, SPAs or RAMSAR sites). This will be a requirement of the detailed WCS,

but a screening study for the AA is suitable for the outline WCS in order to identify if they are any

ecological constraints to the outline study.




6.6 Wastewater Summary

In summary, the following general points can be made about the wastewater baseline and spare capacity:

• Additional wastewater flow from the Central Area and immediate environs will be transferred and

treated at Cotton Valley WwTW,

• Additional wastewater flow from Olney and Hanslope may be transferred and treated at Olney

WwTW and Hanslope WwTW respectively, however there are issues relating to the network and

treatment capacities for both systems,

• There is sufficient volumetric headroom treatment capacity at Cotton Valley to treat an estimated

55,560 homes,

• There is no consented flow headroom at Olney WwTW.

6.6.1 Key Network Constraints

• Upgrading to inlet works due for completion by March 2009 will improve the capacity situation in the

sewer system, particularly to the east (Broughton Brook trunk sewer),

• There is sufficient volumetric treatment headroom at Hanslope WwTW to enable connection of an

estimated 755 homes,

• High level assessments have shown that there are a number of both existing and potential

wastewater network issues, that will need examining in more detail during the detailed WCS,

• The network conclusions need to be verified with network modelling of the development scenarios.

A summary of the wastewater network capacity is shown in Table 6-11.




Table 6-11: Wastewater Network – Constraints Summary

Study Area Sub Area Constraint

North East Major

South East Significant Central

West Significant

South Major Eastern

North Minor

North Major

Central Significant Western

South Minor

East Significant Northern

West Minor

South Western Minor

Land East of M1 Major

Olney Major Rural

Hanslope Major




7 Water Resources and Supply Baseline

7.1 Introduction

This assessment covers the existing baseline with respect to available water resources and where the raw

water to supply the new development will be sourced. It also considers the requirement for transmission

infrastructure for treated water in order to service and supply the new development areas.

7.2 Available Data and Assumptions

Water supply to Milton Keynes is the sole responsibility of AWS who are in the process of producing their

statutory Water Resource Management Plan (WRMP) 2009 which sets out how AWS plan to provide the

required water resources for the region over the next 25 years (from 2010 to 2035). Some outline interim

information was made available from the emerging plan in terms of forecasted supply and demand

balances to 2021 and beyond. The draft WRMP09 was due for consultation at the time of writing this draft

report and hence was not available for the Outline Study; however, the following information was made

available:

• AWS have made available their 2004 WRMP which has been used in this assessment,

• Some outline information was made available in terms of supply and demand balance from the draft

2009 WRMP,

• AWS provided network layouts including pipe sizes of the water supply network,

• EA Upper Ouse and Bedford Ouse Catchment Abstraction Management Strategy (CAMS).

The final WRMP09 is to be published in 2009 and further details of this will be included in Stage 2 of WCS,

if this information is available.

Consultation with AWS confirmed that they hold no DG2 records for Milton Keynes.

7.3 Regional Water Resources: Existing Situation

The EA identifies the Anglian Region as being the driest region of England and Wales. On average the

region receives just less than 600 mm of rainfall per annum




Evaporation from vegetation reduces this amount by approximately 450 mm a year, to give only 150 mm

per annum of ‘effective rainfall’11

to replenish aquifers and to maintain river flows. The recharge of aquifers

is an important mechanism for providing feeds to groundwater-fed ecosystems and wetland habitats. This

is aligned with the government policy to maximise SUDS where possible and practical.

In drought years, the rainfall across the Anglian Region can be as low as 450 mm, which reduces the

amount of ‘effective rainfall’ to zero. The climate gradient from West to East and from North to South is

accentuated across the region.

Regionally, the water supply is resourced from two main sources:

• Surface water abstraction (rivers and reservoirs) – 60%,

• Groundwater abstraction – 40%.

7.4 Milton Keynes - Water Resource Baseline Assessment

The EA manages water resources at the local level through the use of Catchment Abstraction

Management Strategy (CAMS) and Milton Keynes lies within the boundary of the River Great Ouse

catchment. The particular CAMS document referred to in the main is the Upper Ouse and Bedford Ouse

CAMS, published in March 2005.

Within the CAMS, the EA’s assessment of the availability of water resources is based on a classification

system that gives a resource availability status and indicates:

• The relative balance between the environmental requirements for water and how much is licensed

for abstraction,

• Whether water is available for further abstraction,

• Areas where abstraction needs to be reduced.

The categories of resource availability status are shown in Table 7-1. The classification is based on an

assessment of a river system’s ecological sensitivity to abstraction-related flow reduction. This

classification can then be used to assess the potential for additional water resource abstractions.

11 Effective rainfall is defined as the proportion of rainfall that makes up flow river flow or aquifer recharge i.e. that which is not lost to evaporation, uptake by plants or soil storage




Table 7-1 CAMS resource availability status categories

Water Available (WA) Water is likely to be available at all flows including low flows. Restrictions may apply.

No Water Available (NWA) No water is available for further licensing at low flows. Water may be available at higher flows with appropriate restrictions.

Over Licensed (O-L)

Current actual abstraction is such that no water is available at low flows. If existing licences were used to their full allocation they could cause unacceptable environmental damage at low flows. Water may be available at high flows, with appropriate restrictions.

Over Abstracted (O-A) Existing abstraction is causing unacceptable damage to the environment at low flows. Water may still be available at high flows, with appropriate restrictions.

The classification for each of the surface waters and groundwater catchments around Milton Keynes is

summarised in Table 7-2.

Table 7-2 : CAMS resource availability classification

Water Resources Management Unit Surface Water Groundwater

8 - River Ouzel NWA NWA

10 - Upper Great Ouse NWA NWA

9 - Broughton Brook O-A O-A

4 - Bedford Great Ouse NWA NWA

The River Ouzel and Broughton Brook are fed from the Lower Chalk and Lower Greensand Formations,

and then flow in a southeast-northwest direction to join the River Upper Great Ouse near Newport Pagnell.

The River Upper Great Ouse rises further to the west in the Great Oolite Formation and flows in a

southwest-northeast direction along the line of the Great Oolite outcrop. A sharp bend in the Great Ouse

occurs north of Bedford and results in the river turning south for a short stretch until it reaches Bedford,

after which the river continues to flow eastwards across the Oxford Clay. During this short stretch north of

Bedford, the river flows across both the Cornbrash and Kellaways Beds Formation which are exposed in

this section.

A majority of the rivers (including the River Ouzel and River Great Ouse) are defined as having no water

available (NWA) at least at times of low flows. This condition applies to both the surface and groundwater

resource assessments of these catchments. The position of these rivers and groundwaters is that at times

of low flows, no new licences are likely to be issued by the EA unless an equivalent resource is given up

elsewhere. The situation with regards the issuing of abstraction licences at times of higher flows will be

subject to review on a case by case basis.

The situation for the Broughton Brook catchment is that a number of large groundwater abstraction

licences from the Lower Greensand Formation mean that this catchment is classed as being over

abstracted (O-A). No further details have been provided on these abstraction licences and percentage




use. Given this classification, no new abstraction licences are likely to be issued until the resource position

has eased.

7.4.1 Abstraction sources

Milton Keynes (current population approximately 200,000) is situated within AWS Ruthamford Water

Resource Zone 11 (WRZ 11). The name for this zone comes from the three major strategic reservoirs

which supply it, namely Rutland Water (Rut-), Grafham Water (-ham-) and Pitsford Water (-ford). Milton

Keynes gets its supply from Rutland Water and Grafham Water. These are pumped storage reservoirs with

long retention periods and receive most of their throughput from water abstracted from the Rivers Nene

(Rutland) and Great Ouse (Grafham). These reservoirs are both situated some distance from Milton

Keynes. Despite this distance, these sources provide a majority of the supply to Milton Keynes. Extra

water from these sources will be required to meet the future needs of an expanded Milton Keynes.

Closer to Milton Keynes are a number of groundwater sources around Woburn which abstract water from

the Lower Greensand Formation (Woburn Sands). Boreholes are located at Birchmoor-Aspley Guise

(Birchmoor WTW) and at Sandhouse (which is also the name given to the works). Details of average

licence and its Deployable Output12

(DO) indicate that this licence is already maximised [information from

AWS 2004 WRMP,] Table 7-3. The 2004 WRMP refers to some of these sources suffering from rising

nitrate concentrations, which will require action in the future.

A small surface water source (Foxcote intake and reservoir) lies close to Milton Keynes (approximately 12

km to the west) and was last used in 1994. This type of licence, often known as a ‘sleeper licence’, could

potentially be brought back into use given appropriate investment.

In addition, there are other surface water resources in Bedford, which is supplied by Clapham WTW

(approximately 20 km away from Milton Keynes). This WTW abstracts from both surface water (River

Great Ouse) and from groundwater. The average licensed abstraction rates from these two sources are

27 and 6 Ml/d respectively (Table 7-3). This compares to a combined (DO) figure from the 2004 WRMP of

only 15 Ml/d. The 2004 WRMP refers to this source suffering from significant outages (losses) at times of

higher flows. By using surface water and groundwater sources conjunctively, it may be possible to

overcome some of these problems given appropriate investment.

The strategic reservoirs of the Ruthamford WRZ-11 also provide long-standing bulk transfers to Three

Valleys Water Company from Grafham Water and to Severn Trent Water from Rutland Water via Wing

WTW. There is also a small indirect supply to Thames Water’s supply area in the Aylesbury Vale, the

connection taking place via Shenley Water Booster (WB) and Mursley Water Reservoir (WR) to the south

of Milton Keynes.

12 DO is, water which is available for supply during dry years




Table 7-3 : Extracts from AWS 2004 WRMP

WTWs Source Type Average Licence (Ml/d) 2004 WRMP DO (Ml/d)

Clapham WTW Surface Water Intake1 + wells 27 + 6 15

Foxcote WTW Surface Water Intake/ reservoir2 9 + 9 0

Birchmoor WTW

Boreholes3

7 6

Sandhouse WTW

4

Boreholes 5 4

1 River Bedford Great Ouse, d/s of Milton Keynes (Cotton Valley). Significant Outage (e.g. loss in DO) at high flows

2 Foxcote WTW closed in 1994 (AMP2)

3 Birchmoor WTW – groundwater fed WTW known to suffer from high nitrate concentrations

4 Sandhouse WTW – groundwater fed WTW which will feed the proposed Newton Leys development (pers.

comm. AWS)

7.5 Water Supply – Existing Capacity

7.5.1 Growth Forecasts – Increase in demand

The growth forecasts for Milton Keynes refer to the need for approximately 57,950 new homes by 2026. In

terms of population, this represents an increase of approximately 132,700 or 66% increase (assuming an

occupancy of 2.29) on the existing 200,000 residential population of the city.

Various estimates can be made of the likely increase in residential demand expected from the

developments around Milton Keynes based on the overall growth targets and the development scenarios

as set out in earlier sections. The highest forecast for the demand from the maximum target of 57,950 new

homes is 19.46 Ml/d to be supplied on average by AWS. At the other end of the range of estimates, the

lowest demand is 15.99 Ml/d. Tables 7-4 and 7-5 also give an indication of the most likely demand

scenario, assuming that new homes use on average 128 l/h/d and occupancy rates of 2.3, giving a total

average usage of water for 57,950 new homes of 16.99 Ml/d. If an allowance is made for leakage, WTW

operational usage and outage (loss of yield), then up to 30% could be added to these figures. In addition

to the increased residential demand, the growth of the city will also generate an increase in growth in non-

residential development. In the case of Milton Keynes, the non-residential development is likely to be

mainly commercial i.e. shops and service based industry (Halcrow 2007). These industries are likely to

serve the needs of local communities and as such it has been assumed that there will be some form of

relationship between the growth in residential and non-residential demand.

In order to estimate the non-residential demand, the approach taken here has been based on information

provided from the OFWAT Security of supply, leakage and water efficiency reports (in both 2005-06 and

2006-07). Data from these reports shows that non-household demand ranged consistently from 51 to 53%

of total metered demand and to be <1% of total unmetered demand in both years (based on AWS data).




In the case of these non-residential demands), the AWS forecast (new) for residential have been used as

the basis for estimating the non-residential demand. As the <1% figure of total unmetered demand is so

small, then this has been ignored for these calculations.

This total estimated demand figure for non-residential demand (9.14 Ml/d) has been apportioned to

individual areas based on their proportional area as part of the total non-residential development area.

These values have been combined together with residential demand to give a total demand figure (both

residential and non-residential).

The estimates range from 25.1 to 28.6 Ml/d, with the most likely demand figure being around 26 Ml/d.

Note this figure does not include the 30% allowance for headroom referred to above.

One issue which has not been considered in great detail is the potential Marston Vale Eco-Town. If the

Eco-town were to go ahead within a similar time-frame to the developments in Milton Keynes, then this

could add an extra 6 Ml/d of demand on to the demand figures given in Table 7-4 and Table 7-5.




Table: 7-4 Residential Water Demand

Study Area Nos. homes AWS forecast

(Ml/d)*1

Eco–homes rating 120 l/h.d

(Ml/d)*2

Eco–homes rating 135 l/h.d (Ml/d)

*2

Eco–homes rating 127.5 l/h.d

(Ml/d)*2

Range of Estimates

Min (Ml/d)

Range of Estimates

Max (Ml/d)

Central 14350 4.82 3.96 4.46 4.21 3.96 4.82

Eastern (inc. 5,600 Mid-Beds)

13000 4.37 3.59 4.04 3.81 3.59 4.37

South Western (inc. 5,390 in Aylesbury Vale)

9000 3.02 2.48 2.79 2.64 2.48 3.02

Western 10000 3.36 2.76 3.11 2.93 2.76 3.36

Northern 3000 1.01 0.83 0.93 0.88 0.83 1.01 Outliers (Olney, Hanslope

& Newport Pagnell) 3000 1.01 0.83 0.93 0.88 0.83 1.01

Land East of M1 5600 1.88 1.55 1.74 1.64 1.55 1.88 Total 57950 19.46 15.99 17.99 16.99 15.99 19.46

*1

Assuming 146 l/h.d supplied and assuming occupancy rate 2.3 (estimate used for Thetford WCS) *2

Eco-homes rating of 120-135 l/h/d (Ref. Consultation of water efficiency in new buildings, CLG – January 2007) and an assuming occupancy rate of 2.3 (AWS Strategic Doc. – Dec 2007)




Table 7-5: Total Water Demand in Milton Keynes

Study Area Nos. homes Estimate of Water to be supplied

*4

Development area (Non-residential)

Ha

Weighting based on development area (Non-residential)

Total Supply (Residential & Non-

residential) (Ml/d)

Range of Estimates Min

(Ml/d)

Range of Estimates

Max (Ml/d)

Central 14350 - 86 4.52 8.72 8.48 9.33

Eastern (inc. 5,600 Mid-Beds)

13000 - 53

2.78 6.60 6.37 7.15

South Western (inc. 5,390 in Aylesbury Vale)

9000 - 3

0.16 2.80 2.64 3.18

Western 10000 - 29 1.52 4.46 4.28 4.88

Northern 3000 - 3 0.16 1.04 0.99 1.16 Outliers (Olney, Hanslope

& Newport Pagnell) 3000

- 0.1 0.01 0.89 0.83 1.01

Land East of M1*5

5600 1.64 1.55 1.88 Total 57950 9.14 174.1 9.14 26.13 25.14 28.60

*4

Non-residential demand assuming MK similar to the rest of AW Region i.e. average 52% over the last 2 years of total metered supply. Note demand estimated on AWS forecast 5

No non-residential development assumed to take place on land east of M1




7.5.2 Existing Capacity

Milton Keynes lies within AWS’s Ruthamford Water Resource Zone (WRZ –11). The definition of a WRZ is

the largest supply area in which water resources can be readily moved about and shared. Exports and

imports may also take place from these zones.

The Ruthamford WRZ is one of the largest WRZs in the Anglian region, extending from Peterborough in

the north to Buckingham and Leighton Buzzard in the south. It also serves the growth town of Corby.

For each of these WRZs, AWS is required to carry out an assessment of how much water is available and

how much water may be required in the future. This balance is called the supply and demand balance

(S/D balance) and it is calculated for the current baseline and projected forward 25 years (to 2035) such

that AWS can determine where future deficits in the balance might occur (or are already occurring); this

planning is undertaken for a worst case very dry year to ensure that sufficient resources are available for

worst case conditions. The projected future demand includes for estimates of increases in population for

the Milton Keynes and Newport Pagnell Water Resource Planning Zone (WRPZ) and includes an

allowance for ‘headroom’ on top of the future predicted demand. The headroom allows for issues such as

outage of water supply facilities and an allowance for uncertainty associated with climate change.

The 2004 WRMP provides useful background information on the Ruthamford WRZ. A brief summary of

the zone’s water balance is given below:

• Total DO from the Ruthamford WRZ-11 is between 582 (average) and 732 (peak) Ml/d,

• AWS Distribution Input (DI)13

figure range from between 361 (average) and 510 (peak) Ml/d,

• The difference is made up of mainly exports from this zone, including long-standing bulk transfer

agreements with both Three Valleys Water Company (91 Ml/d on average from Grafham WTW to

the south) and Severn Trent Water (18 Ml/d on average from Rutland/Wing WTW to the west),

• The remainder is made up of leakage (approx. 81 Ml/d in this zone or 22% of average DI) and a

small amount of both WTW operational usage and outage (loss of yield) etc,

• AWS leakage is close to Economic Level of Leakage14

(ELL) for this zone of 77 Ml/d. It was planned

to keep close to the ELL throughout the AMP4 period (2005-2010). Further discussion on AWS

Water Efficiency Strategy is included in section 7.5.5.

Overall, the position up to 2010 was that a slight deficit in the supply/demand balance for this zone was

expected.

13 Distribution input – The amount of water put into supply, including water not actually delivered i.e. leakage and water taken illegally. 14 Economic Level of Leakage - The level of leakage for which the cost of achieving and then maintaining that level is exactly offset by savings in capital and operating costs.




A detailed water balance for Milton Keynes (including Newport Pagnell) has been provided by AWS, as an

interim output ahead of the 2009 draft WRMP which is due to be published in May 2008. The information

provided at present includes details of the amount of water available for supply and the demand for potable

water in the Milton Keynes and Newport Pagnell Water Resource Planning Zone (AWS’s WRPZ No. 93

and 92 respectively). The WRMP process then identifies potential water resources that could be

developed to bridge the gap in supply and demand (covered in Section 8 – future water supply strategy).

The latest interim S/D balance provided by AWS indicates that:

• The current predicted average demand in Milton Keynes and Newport Pagnell is around 55 Mld-1

and just over 60 Mld-1

with an allowance for headroom,

• The average demand is projected to increase by around 5 Mld-1

by 2035; the allowance for

headroom results in an increase in demand of around 14 Mld-1

by 2035 (N.B. the differences

between this figure and estimates made in Tables 7-4 and 7-5 may be due to different assumptions

made on the number of new homes to be built. Potential inconsistencies to be looked during the

detailed study.

The Milton Keynes and Newport Pagnell WRPZ currently only has sufficient DO to meet demand, not

taking into account headroom, through until 2019/20. If headroom is taken into account, then there is

already a shortfall in the existing resource position and therefore further development of new resources will

be required immediately. In order to address this position AWS will be undertaking upgrading work at

Wing WTW to increase the DO within the AMP4 period (2005-2010). Beyond 2010, then the

supplementing of available resources by developments of local resources within existing abstraction

licence limits may be necessary.

The interim outputs from 2009 draft WRMP demonstrates the importance for AWS of completing their

investment plans for AMP4 period. The upgrading of Wing WTW was seen by AWS as the medium term

solution (covering the period up to around 2021) in their 2004 WRMP. The scheme will enable AWS to

maximise their abstraction licence at Rutland Water. More specifically the scheme will see;

• An increase in the design capacity of Wing WTW from 270 to 360 Ml/d (currently the average and

peak DO figures are 204 and 255 Ml/d respectively),

• The provision of 40 km of large diameter trunk main from Rutland Water to Wing WTW and from

there to Kettering (approximately half-way to Milton Keynes) via Corby,

• The provision of associated pumping stations for this trunk main.

This work is due for completion by March 2010.




It is expected that the 2009 draft WRMP will contain updates on these schemes and other planned work for

the Ruthamford WRZ-11 underway during AMP4.

7.5.3 Environmental Baseline - Water Supply Assessment

Wing WTW is operated in conjunction with Rutland Water. This reservoir was originally constructed in

1975, and shortly after it was designated as both a SSSI and Special Protection Area (SPA), the latter

being in recognition of its standing as an internationally important wetland habitat for migrating birds.

The Statutory Designations at Rutland Water mean that any potential impacts have to be assessed and

mitigated where necessary. The approval by the Secretary of State for the planning permission associated

with Wing WTW, place a requirement on AWS to undertake mitigation measures to overcome the impacts

on wildlife in the event of the reservoir being drawn down for longer periods than at present. The

measures proposed have included the construction of dams across parts of reservoir to form lagoons and

wetlands, mainly along the western edge of the reservoir. The new wetlands will be completed by

November 2010 (the construction taking slightly longer than at Wing WTW in order to minimise the adverse

effect on the SPA. Work is being conducted mainly in late-winter, spring and early summer for the next

three years).

Long term management and maintenance of these newly created wetlands is still to be agreed, although

AWS have confirmed that they are near to completing their consultation and hope to reach agreement with

the various parties shortly.

The extra length of time during which Rutland Water is drawn down, may have consequences on the

amount of spill which takes place from this reservoir and flows into the Rivers Gwash and Welland.

Although it is worth mentioning that the extra demand placed on Rutland Water from growth in Milton

Keynes will be small compared to the total growth expected across the wider East of England.

A number of other protected sites are mentioned in the CAMS document. A summary of the protected

sites within certain catchments are presented in Table 7-6.

Table 7-6: Summary of Protected sites

Water Resources Management Unit

WTWs Distance and direction

from CMK Protected areas/ SSSI

(WRMU)

4 – Bedford Great Ouse Clapham 20km - North East See paragraph below

10 – Upper Great Ouse Foxcote 12km - West Foxcote Res & Wood, Tingewick Meadows

9 – Broughton Brook Birchmoor 5km - East Wavendon Heath Ponds

Note: County Wildlife Sites have not been included in this table




2004 WRMP (public version) makes reference to a number of historical concerns by stakeholders about

the Bedford Great Ouse (from which abstractions take place at Clapham WTW) and Nene (abstractions for

Peterborough area) but which have now been allayed through studies undertaken in the AMP3 period

(2000-05).

7.5.4 Potential Risks to Supply

When considering potential risks to AWS supplies, the following points may be important:

• Climate Change – AWS will be considering the effects of climate change in its 2009 draft WRMP. In

general the effects on DO from groundwater sources is thought to be negligible. Surface waters are

likely to be more affected. For example, surface water intakes such as Clapham WTW (Bedford

Great Ouse) could see a loss of yield of up to 2 Ml/d15

on average. This compares with 2004 WRMP

DO figure of 15 Ml/d and which could mean a loss of yield of around 10% by 2021. In the case of

the other surface water sources within the Ruthamford system, these are mainly multi-season

reservoirs with pumped storage schemes, which rely on abstraction from rivers over the winter

months and therefore these are likely to be less affected by climate change,

• Review of Consents – relates to investigations of abstractions and their impacts on designated sites.

The EA is the Competent Authority and review is due for completion by 2010. It is currently

understood that none of AWS’s sources in the Milton Keynes are part of this review,

• Water Framework Directive – requires all river basins to achieve “good ecological and good

chemical status” by 2015. As per the Review of Consents, the EA is the Competent Authority and

further details on the Programme of Measures (POM) i.e. actions required to reach Good Ecological

Status is expected by the end of 2008. The POM is likely to include details of the further

investigations to be undertaken by water companies to ascertain whether any impacts are taking

place. These will need to carried out by 2015, with any changes to abstraction licences taking place

after this date,

• Water Supply Resilience – all new (and existing) water supplies should be resilient, whereby if the

standard means of water provision is disrupted (i.e. the wash out of a pipe across a river crossing)

then there is a secondary means to continue to supply potable water. Generally speaking the Milton

Keynes water supply system is well connected, allowing the re-distribution of potable water. This is

something that must be carried through to any new development.

15 The loss of yield figure of <2 Ml/d was provided by AWS for the Norwich WCS Stage 2




7.5.5 Water Efficiency Strategy

A water efficiency strategy has been published by AWS within the AMP4 period (2005-2010). This

strategy summarises the steps being taken to control the growth in demand. The two main strands of the

policy are through leakage control (the latter being achieved through both pressure reduction and checks

on pipes) and water metering.

The latest information on leakage from the OFWAT Security of supply report for 2006/07 is that AWS

leakage was 202 Ml/d or 17.5% of the DI figure (1156 Ml/d in 2006/07). This figure is below the target set

by OFWAT for this year of 215 Ml/d.

AWS has already taken steps to encourage the greater uptake of meters through an initiative in the early

1990’s. Currently around 60% of AWS’s customers have a meter installed. AWS have confirmed that all

new connections shall be metered.

In terms of the typical amounts of water used, see Table 7-7.

Table 7-7: Amount of Water Used by Type

Customer type 2005-06 report

(l/h/d) 2006-07 report

(l/h/d)

Metered 128.0 136.9 Un-metered 160.0 155.8

Overall 144.0 146.0 Note: 2005/06 and 2006/07 refer to OFWAT Security of Supply report (previously Security of supply, leakage and water efficiency report).

An interesting feature of the 2006/07 figures is the slight increase in the water used by AWS metered

customers. A full explanation for this increase is to be sought from AWS but it is worth mentioning that this

increase was from the very low base apparently observed in 2005/06 (certainly compared with the water

industry average for metered customers in 2005/06 of 134 l/h/d). It is therefore possible that AWS

underestimated water use in the 2005/06 survey.

7.6 Water Supply Network – Baseline

Assuming that water resource issues can be overcome (especially demand shortfalls, but ideally headroom

as well) with upgrading of Wing WTW, it is important to consider how potable water will be supplied to the

proposed development areas according to the development scenarios being considered.




Figure 7-2: High level Milton Keynes Water Supply Schematic Source: Anglian Water Services




The existing AWS water supply network within Milton Keynes is shown in Figure 7-1. Figure 7-2 shows the

strategic regional water resources distribution network. Figure 7-2 also shows in more detail the water

supply system consisting of major trunk mains to transfer water from the various raw water sources to

demand centres within Milton Keynes. The main features of water supply network are:

• Imports from Wing WTW (Rutland Water) into the northwest corner of city via the Old Stratford

Water Booster (WB),

• Imports from Grafham WTW (from its namesake reservoir) into the east of the city via Woburn

Sands WB,

• A feed from Sandhouse WTW (groundwater fed) which will feed into the proposed Newton Leys

development.

There is also an export of treated water into the Thames Water supply area (Aylesbury Vale) via Shenley

WB and Mursley Water Reservoir (WR) in the west and southwest of the city.

East of M1 levels of off-site works will be more than for other growth areas since existing mains in that area

do not have the capacity to serve such a major development.

As well as considering modelling of the water supply network, the Stage 2 WCS will also need to assess

the capacity of the Water Treatment Works (WTW) feeding Milton Keynes.

7.7 Bedford and Milton Keynes Waterway

The Grand Union Canal (GUC) runs from Birmingham to River Thames at Brentford. It was built by James

Barnes, a canal engineer between 1792 and 1805. The total distance of the canal is 220 km (137 miles).

It includes several significant engineering achievements, the ascent of the Chilterns (highest point at Tring

approx. 100 mAOD) and the aqueduct across the Upper Great Ouse using an ‘Iron Trunk’ set above the

river. British Waterways are the statutory navigation authority for the GUC. A number of charitable trusts

have been established along the canal to promote the wider recreational use of the waterway.

British Waterways, in collaboration with the Bedford and Milton Keynes Waterway Trusts, has plans to

provide a new canal link between the GUC in Milton Keynes and the River Great Ouse in Bedford called

the Bedford and Milton Keynes Waterway. The route of this new canal link was talked about as far back as

early 2003, the total distance being 32 km (20 miles). Outline design is complete for the first 7km of the

route, through Milton Keynes to just north of Junction 13 of M1.

The water resources aspects of this scheme were looked at by Halcrow (2004) for the section as far as M1

(J13). Their conclusion was that at least for this first stage (7km) that sufficient water resources are

available from the existing abstraction points to meet the need of this canal extension. This assumes that




no restrictions are placed on abstractions from the Upper Great Ouse between Stoke Bruerne in the north

and Ivinghoe in the south (EA 200516

). The EA and BW have an agreement that allows BW to maintain

water levels with abstractions from the River Tove and Ouse near Stoke Bruerne. It must be noted

however that the EA would not allow any additional licensed abstraction in summer from the River Tove

and Ouse. Further investigation was planned for Stage 2 of this canal link beyond the M1 to Bedford. ‘In

2007 detailed planning consent was granted for the section of the canal from the Eastern Expansion Area

along the Broughton Brook and the remaining section to the GUC received outline planning consent. At

the request of the EA and the IDB conditions were attached to both the detailed and outline consents to

require further studies regarding water resources and flood risk before the development takes place. It is

unclear whether this scheme will be of any practical benefit for the transfer of water resources. Stage 2 of

MKWCS will need to consider this matter in more detail.

7.8 Water Resources and Water Supply Summary

• Milton Keynes is presently supplied by Wing and Grafham WTWs, which are in turn fed from Rutland

Water and Grafham Water respectively,

• The forecast growth in demand for 57,950 new homes (by 2026) is estimated at 17 Ml/d for

residential demand and a further 9 Ml/d for non-residential development. The latter demand is likely

to be from commercial and service based industry. The combined total is approximately 26 Ml/d on

average but could be as high as 29 Ml/d on average.

• In addition, the above estimates do not take into account of the Marston Vale Eco-Town, which

could drawn up on an extra 6 Ml/d,

• AWS latest supply/demand balance indicates that the Milton Keynes and Newport Pagnell area

currently only have sufficient DO to meet demand, not allowing for headroom, until 2019/20.

Allowing for headroom, this shows there is already a resource shortfall. This position will be eased

in the short term (by 2010) through developments at Wing WTW (supplied by Rutland Water),

• Beyond 2010, it may be necessary to supplement available resources by the development of local

schemes, such as at Foxcote WTW, within the existing abstraction licence limits,

• In the longer term, a major regional resource development may be required, such as the River Trent

Transfer Scheme. Further discussion of the resource scheme options are included in section 8.3.2.

16 EA 2005 – The Upper Ouse and Bedford Ouse CAMS




• The mitigation measures being put in place at the Rutland Water SPA, such as the creation of

wetland habitats, should enable full take-up of this licence quantity without any negative effects on

the site,

• A number of other uncertainties – Climate Change, Review of Consents and Water Framework

Directive remain and which may affect the water resources situation in the future and the status of

available growth within Milton Keynes,

• Detailed configuration can be tested and hence costed using network models in the detailed WCS,

although this will be dependent on the availability of information as to the location of development,

demand and phasing.




8 Water Cycle Option Development

8.1 Introduction

Chapters 5 to 7 assessed the existing constraints and existing baseline for the current WSI in Milton

Keynes. This was undertaken in the context of analysing how much development could be brought

forward with existing infrastructure or minimum investment in new infrastructure. This section

discusses outline or strategic options for providing new infrastructure which has been identified as

required to supply projected housing targets. This assessment needs to be undertaken before the

development scenarios can be tested against the various water cycle assessment criteria.

8.2 Wastewater Option Development

8.2.1 Future Capacity and Upgrade Requirements

Wastewater Network

The initial high level assessment of the wastewater network has highlighted a number of areas with

spare capacity to support growth in the short term (e.g. 5-10 years), with either no upgrades or

minimal upgrades required (some areas are expected to be able to take all planned growth).

However, the assessment has also highlighted areas where there is both an existing problem with

capacity, or where there is likely to be issues with capacity (without significant infrastructure

upgrades) post development. As an initial option, consideration should be given to the phasing of

development, whereby development is ‘fast tracked’ in areas, where no (or minimal upgrades) are

required.

Further more detailed work (including network modelling) should be undertaken as part of the

detailed (stage 2) WCS, to confirm the capacity issues highlighted in this outline study.

Treatment

AWS would be required to seek funding through the Price Review Process in order to provide any

additional treatment required. AWS are currently examining the potential to increase treatment

capacity at Cotton Valley WwTW.

AWS do not consider that the DWF consent will need to be revised until AMP6. Increased effluent

discharges to the River Ouzel and River Great Ouse will impact on flood risk and water quality.

Before approving increases in consented discharges to these rivers, the EA will require further

catchment modelling to identify any necessary mitigation works particularly with reference to the




lakes in Milton Keynes. This should either be included in the detailed stage of the water cycle study,

the Level 2 SFRA or as an independent study for example a surface water management plan.

It is strongly recommended that as part of the detailed (stage 2) WCS, further information regarding

the scheme to increase treatment capacity at Coton Valley should be obtained from AWS. This

would then lead to a detailed review of process capacity and impacts on receiving watercourses and

downstream sites. Such a review should also pay attention to upstream discharges on the River

Great Ouse and River Ouzel, paying particular attention to regulatory standards and phosphorus

since water quality impacts can be cumulative. Discharges should ideally be considered from

headwaters to outfall using appropriate data and modelling software such as SIMCAT.

8.3 Water Resources Option Development

8.3.1 Introduction

At the present time, AWS are in the process of drawing together their new WRMP for AMP5 and

beyond. An early indication of their likely strategy to be contained within their 2009 WRMP was

presented in AWS’s Strategic Plan document for the next 25 years and which was published in

December 2007. This document identified Milton Keynes as a demand hotspot, along with a number

across its region (from Regional Spatial Strategy). A combination of water re-use (abstraction of

water discharged upstream) and major WTW development at Clapham (near Bedford) were referred

to. Along with these developments, there would be continued support to this area from the three

major strategic reservoirs (and possibly supported by a Trent Transfer scheme in the longer term). In

the draft WRMP09, latest document published by AWS in May 2008, it appears that there has been a

shift towards a twin-track approach of demand management (leakage control and an enhanced

metering programme) and use of more local solutions, where available, have been given greater

emphasis over increased transfers. It is thought that the reason for this may be the requirement by

OFWAT for carbon accounting to be taken into accounting all future WRMPs.

It is made clear in the 2009 draft WRMP that these plans have a number of uncertainties most

notably:

• The Review of Consent is assumed to result in a loss of yield of only 5 Ml/d (although figures

well in excess of this have been mentioned by the EA previously),

• A major Groundwater scheme in the Great Ouse catchment requires a licence to be granted by

the EA. The latest information from AWS is that this scheme is not now likely to go ahead and

that instead a combination of demand management measures and possibly a new major

resource development may be required.




• It is also assumed that no extra demand will come from neighbouring water companies (over

and above the long-standing bulk transfers agreements),

• The Water Framework Directive has not been taken account of in the WRMP (see

section 7.5.4).

8.3.2 Water Supply Strategy

Firstly, AWS is expected to maintain its levels of leakage at the close ELL (see section 7.5.2). Apart

from metering, which is mentioned below, all other water efficiency measures will produce only small

amounts of savings.

Short Term

In the short term, AWS will meet the growth in demand by a combination of enhanced metering (this

will generate up to 10 Ml/d across the wider Ruthamford Zone WRZ-11 or pro-rata for the Milton

Keynes/Newport Pagnell area, a saving of 1.3 Ml/d) and improvements to WTWs. The upgrading of

Clapham WTW, planned for AMP5, would in turn release DO from Grafham to support growth in

Milton Keynes. A further 10 Ml/d of DO is expected to come from these developments over the

AMP5 period (2010-2015). The additional resource being made available from Wing is also key to

meeting growth in Milton Keynes in both the short and medium term.

Medium Term

After 2015 (AMP6 and beyond), AWS propose to refurbish Foxcote WTW (source of supply - surface

water intake and reservoir) local to Milton Keynes and which will provide approximately 7 Ml/d in the

medium term. This source is already licensed to AWS, therefore the fact that the Upper Great Ouse

is defined by the CAMS as having no water available should not impact on this scheme.

Long Term

In the longer term, AWS propose to make use of the extra discharges from Cotton Valley WwTW

near Milton Keynes and to increase its abstractions downstream at Clapham WTW. This will be a

phased development undertaken over the medium to longer term and which will hopefully yield a

further 10 Ml/d from this site for the Bedford area, which will in turn release DO from Grafham. This

extra yield at Clapham may require a variation to the licence (currently 27 Ml/d from surface water

and 6 Ml/d from groundwater). Although the CAMS document states that the Bedford Great Ouse

has no water available, it is the case that the slight increase in the licence quantity may be

acceptable to the EA if it is part of a scheme to re-use water from further up the catchment.

In addition, a major regional resource development may be required in the long term, such as the

River Trent Transfer Scheme. As part of this scheme, there may be a need to re-zone supplies from

adjacent planning zones.




The likely infrastructure requirements needed to supply this water is determined below with an

indicative outline cost. The methodology used is similar to that used successfully on other WCS and

which is outlined in the figure below. At this stage in the WCS process, it is noted that the costs are

indicative only and should only be used as a way of determining the potential monetary impacts of

providing the required water resource infrastructure for the predicted housing targets.




Figure 8-1: Indicative costing process for broad scale water resource options

Source: Scott Wilson




In the case of Milton Keynes:

• AWS is expected to maintain its level of leakage at the ELL,

• The savings from the enhanced metering programme are expected to provide 1.3 Ml/d on

average within this area (pro-rata from 10 Ml/d savings across the entire Ruthamford WRZ-11),

• The upgrading of Clapham WTW, which will in turn release DO from Grafham, to provide up to

10 Ml/d of yield,

• The refurbishment of Foxcote WTW to provide up to 7 Ml/d of yield,

• Further phased development at Clapham WTW involving abstraction of extra water discharged

from Cotton Valley WwTW in Milton Keynes, this will again release DO from Grafham, to

provide up to 10 Ml/d (subject to a licence variation).

• A transfer-in from Wing WTW, supplied from Rutland Water, would provide the remainder.

From these demand management measures and a range of water resource developments, it should

be possible to provide sufficient resources to meet the forecast growth in demand of 26 Ml/d on

average and potentially up to 29 Ml/d. These additional resources may not be sufficient to fully cover

the 30% allowance for headroom which is recommended. Further support from the other major

strategic reservoirs in the Ruthamford, along with any new resources development such as the Trent

Transfer scheme may also be required to meet demand in Milton Keynes. This is particularly likely to

be the case if the proposed development for an eco-town at Marston Vale is given the go ahead.

Referring to Figure 8-1 and by placing appropriate costs against the Resource Development,

Production (Treatment) and Distribution, it is possible (using the calculations shown in the table at the

bottom of this figure) to derive rough costs for water resources and water supply for this level of

development. For example; it is estimated that in the short term approximately 10 Ml/d and in the

long term 21 Ml/d (would come from existing licences (Grafham and Rutland) requiring only extra

production capacity and more distant distribution costs (Model E). Whilst around a further 7 Ml/d

would come from an existing surface water source at Foxcote (Model B). This also assumes that

approximately 1 Ml/d from water savings (through an enhanced metering programme).

8.3.3 Anglian Water – Future Asset Management Planning

The following information has been provided by AWS, with regards to offsite requirements required to

safeguard the water longer term water supply for Milton Keynes.

Significant offsite reinforcements are required to support the proposed growth in Milton Keynes and

these include increased:

• WTW capacity,

• Storage,




• Water mains reinforcements,

• Pumps upgrades.

A number of schemes have been identified by AWS to support the outstanding Local Plan growth

(2001 - 2011 to deliver 24,100 new homes) the majority of this growth is located within the four key

expansion areas:

• Western Expansion Area,

• Northern Expansion Area,

• Eastern Expansion Area,

• Central Milton Keynes.

To support growth in the short to medium term would require the following AMP4 (2005-2010)

schemes, which are currently at detailed design or under construction. Schemes to be delivered as

part of AMP4 include:

i. Wing WTW increased capacity,

ii. Wing Strategic Mains,

iii. Old Stratford pump upgrades.

Additional schemes to support growth in AMP5 (2010-2015) have also been identified however it is

anticipated that this would not be sufficient to support the demand of the additional dwelling target to

2031. Future AMP5 (and beyond) schemes, which are to be driven by growth include:

iv. Reinforcement between Ampthill and Woburn Water Reservoirs,

v. Reinforcement between Old Stratford Pumping Station and Kiln Farm.

Assumed at this stage like for like reinforcement:

vi. Upgrade of Woburn Pumping Station,

vii. Increased storage, existing storage points identified in the strategy plans as requiring

additional storage (Deanshanger, Woburn and Brickhill Copse Water Reservoirs,

viii. Resilience - Salcey to Deanshanger rail crossing - duplication of the existing main

under the railway.

There are two major points of supply into Milton Keynes that transfer water into the

east and west of the Milton Keynes grid main network. Water is transferred from the

east via Woburn Sands water booster and Brickhill Copse Water Reservoir

(predominately Grafham WTW) and from the west via Old Stratford Water Booster

(predominately Wing WTW). The schemes identified above are to increase the

strategic transfer capacity and storage however once additional information is




available for the future large scale development areas the need for local offsite mains

reinforcement can be reviewed.

Local offsite mains reinforcements have currently been identified to support the following growth

areas:

• Western Expansion Area,

• Eastern Expansion Area,

• Newton Leys (supplied from Sandhouse WTW),

• Kingsmead and Tattenhoe.

The water cycle study indicates that up to 2011, allocations will be in accordance with the Local Plan.

Over the period 2011-2026 there will be a focus of up to 8,500 houses in the urban area to support

urban renaissance, which will be principally focused on Central Milton Keynes, Bletchley and

Wolverton. As the existing mains in these areas will not have been designed for growth on such a

large scale significant offsite mains reinforcements may be required.




9 Generation of Flood Risk - SUDS Options

9.1 Introduction

Chapter 5 undertook an assessment of potential flood risks and hence constraints posed to potential

development areas. This section considers flood risk generated as a result of development which is

an important consideration with respect to the assessment of development scenarios and current

national planning policy with regards to flood risk management.

In areas where development runoff is likely to be discharged to a river system, it is important that new

development does not increase the risk of flood risk downstream (or indeed upstream) by increasing

runoff rates to greater than that of the runoff generated by existing land use. In addition, it is

important that new development does not increase the risk of overland flow to adjoining development

areas by increasing the amount of impermeable area.

Milton Keynes has been developed around the concept of strategic and integrated surface water and

flood risk management, with large flood storage reservoirs and engineered watercourse. The

Drainage SPG states growth must provide strategic and integrated drainage systems. Therefore

Strategic and Integrated drainage and SUDS is essential to continue the success of Milton Keynes.

9.1.1 National Flood Risk Policy - PPS25

PPS25 requires that all new development should ensure that runoff rates and runoff volumes from

new development are not increased above that of the existing land use. Much of the ‘infill

development within the Central Area will be on previously developed (brownfield) land; hence the

requirement to reduce runoff rates as a result of rainfall will be less onerous for these developments,

compared to those on Greenfield sites. For infill development on currently undeveloped land and

development of the new areas, there will be a requirement to ensure that runoff rates and volumes

are no greater than the Greenfield rates for the design event with return period of 1 in 100 years (with

an allowance for climate change) and smaller rainfall events up to this level.

9.2 Flood Risk from Development – Strategic Options

9.2.1 Central Area

Unlike other urban and suburban areas, due to its nature Milton Keynes only has a brownfield

regeneration target of 20%. Therefore the majority of new development within the Central Area (circa

80%) will be on Greenfield land and will significantly increase surface water runoff.




Consideration should be given to on-site and strategic attenuation of surface water runoff generated

from the Central Area, thus reducing the pressures on the existing surface water network.

9.2.2 Eastern Area

New development within the study area will primarily be constructed on Greenfield land. The amount

of impermeable land is therefore likely to increase and it would be necessary to ensure SUDS

techniques are employed in any development. The Development Framework for the Eastern

Expansion Area sets out guidelines for surface water drainage from new development. Flood risk

management and drainage infrastructure will be fully funded by the development. It considers SUDS,

including wet and dry ponds, areas of open space, will retain and potentially enhance the linear park

that runs through the site along Broughton Brook. The brief identifies five drainage catchment areas

and the surface water from each will be intercepted by offline balancing ponds and wetlands and will

attenuate peak discharge to between 1 and 5 l/s/ha for a storm of return period of 1 in 100 years,

consideration will also need to be given to the effects of climate change.

The Broughton Gate and Nova Development Briefs (sites within the Eastern Expansion Area) also

provide more site specific outlines for the individual sites for surface water drainage, but it is also

important to consider strategic based SUDS in conjunction with site specific SUDS. Part of the Nova

Development Brief explains that attenuated discharges will pass through piped systems and onto a

wetland storage area adjacent to Broughton Brook. Discharges will be attenuated via site source

control and flow attenuation measures. There will be a permanent wet meadow/swale feature and

ancillary water balancing ponds on the southern edge of the floodplain. The development will extend

the ‘Broughton Brook Linear Park’. Other potential SUDS techniques include underground tank

storage, roof drainage storage and block-work paving (where appropriate). The drainage strategy for

the Development Framework has included a 20% allowance for climate change.

9.2.3 Western Area

New development within the western study area will primarily be constructed on Greenfield land. The

amount of impermeable land will therefore increase and it would be prudent to ensure SUDS

techniques are employed in any development to minimise any potential increase in surface water

runoff. The Development Framework for the Western Expansion Area gives an indication of potential

surface water management techniques for the proposed development. Primarily this will be through

a series of balancing ponds and open spaces. A balancing pond will be potentially located near the

V4 at Watling Street. The aim of the surface water management plans will be to reduce peak

discharge to 3l/s/ha for a 1 in 100 year storm event, consideration will also need to be given to the

effects of climate change.




Runoff will discharge to Loughton Brook and mitigation measures will be located along Loughton

Brook. There will also be on-site ponds at the Kiln Farm site, following guidance from the IDB that

storage would be more appropriate at this location than increased conveyance to Loughton Brook.

The development brief highlights that infiltration based SUDS are not likely to be appropriate in this

area due to ground conditions and that balancing ponds should be able to deal with the entire volume

of surface water runoff.

9.2.4 Northern Area

New development within the northern study area will primarily be constructed on Greenfield land.

The amount of impermeable land is therefore likely to increase and it would be prudent to ensure

SUDS techniques are employed in any development to minimise any potential increase in surface

water runoff. It may be possible to attenuate surface water flows through utilising the numerous

lagoons to the north of the development area. The Northern Expansion Area Development

Framework has considered surface water management through the incorporation of SUDS into the

development. Where ground conditions permit, this could include porous paving and soakaways.

9.2.5 South Western Area

Any development on Greenfield land will increase the amount of impermeable land and it would

therefore be important to ensure SUDS techniques are employed in any development to minimise

any potential increase in surface water runoff.

It is likely that the onus for surface water management of the site will fall to individual developers,

through the implementation of integrated strategic management of surface water, drawing upon the

resources of multiple developers as they look to promote an area for development. This approach is

recommended by the EA and IDB, as it promotes sustainability and also avoids the construction of

disparate systems.

9.2.6 Land East of the M1

Development on greenfield land (the majority of the study area) will increase the proportion of

impermeable surfaces and it is therefore important to ensure that integrated SUDS techniques are

employed in any development to minimise any potential increase in surface water runoff.

It is likely that the onus for surface water management of the site will fall to individual developers,

through the implementation of integrated strategic management of surface water, drawing upon the

resources of multiple developers as they look to promote an area for development. This approach is

recommended by the EA and IDB, as it promotes sustainability and also avoids the construction of

disparate systems.




In all development areas, development, flood risk infrastructure and mitigation measures must be

sustainable in terms of future maintainability and whole life costs must be taken into consideration.

9.2.7 Rural Areas

Development on Greenfield land will increase the proportion of impermeable surfaces and it would

therefore be important to ensure SUDS techniques are employed in any development to minimise

any potential increase in surface water runoff.

In all development areas, developments and, flood risk infrastructure and mitigation measures must

be sustainable in terms of future maintainability and whole life costs must be taken into consideration.

9.3 SUDS Utilisation

In order to reduce runoff rates from developed sites to that of existing (and where possible to achieve

‘betterment’), PPS25 and its companion guidance recommend that Sustainable Drainage Systems

(or techniques) known collectively as SUDS are used.

Surface water drainage from any new development within Milton Keynes should be designed in

accordance with recommendations as set out PPS25 and the SUDS Manual (CIRIA C697) as a

minimum and also in consultation with the EA and IDB (where appropriate). Consideration should

also be given to including porous paving (where permissible) and water recycling techniques such as

rainwater harvesting and greywater recycling.

In general, there are advantages to be gained to developing drainage strategies for site wide

developments such that strategic scale options such as utilising the existing attenuation lakes can be

developed at lower overall cost (albeit with potential new linkages), but also to:

• Maximise green infrastructure linkage,

• Maximise ecological enhancement,

• Maximise water quality benefits from retention and filter type SUDS,

• Contribute towards the point system for Code for Sustainable Homes grading.

Considering the options now, is a key consideration for this strategic WCS. The following sections

outline some of the key outline or strategic considerations for SUDS for the development areas, and it

is recommended that the Stage 2 study develops site wide strategic drainage plans for the

development scenarios and areas taken forward into the next planning stage. Property based SUDS

should be provided in addition to strategic SUDS, and not instead of.




9.3.1 Surface Water Attenuation

Once more is known about the precise numbers of housing and likely layouts of the sites, it is

recommended that the detailed requirement for different types of SUDS is undertaken (possibly in the

Stage 2 WCS and certainly at site specific FRA stage). At this stage it can be assumed that a

percentage of the development areas can be set aside as green space and notwithstanding other

SUDS techniques. Therefore the remaining runoff generated from rainfall events will have to be

attenuated or stored in surface water systems such as large scale strategic balancing lakes, or

smaller site-specific ponds.

Once draft masterplans for each of the developments are available, then further work will be required

to determine the increase in run off due to development, allowing the required attenuation volumes to

be calculated. Guidance in the Preliminary Rainfall Runoff Management for Developments or the

Interim Code of Practice for SUDS should be referred to.

Once post development run off rates and volumes have been determined (following masterplanning),

surface water attenuation will need to be provided, utilising SUDS. Infiltration based SUDS are

limited within Milton Keynes due to the nature of the underlying geology and presence of SPZs (to the

South East), primary consideration should be given to the use strategically located large-scale

attenuation facilities, developed to attenuate water from a number of developments (rather than a

number of individual disparate ponds, per development). In some instance, there may be a need to

consider the use of smaller scale site-specific features such as rainwater harvesting, filter strips,

swales and smaller balancing ponds.

9.3.2 SUDS options

A description of the type of SUDS that could be considered for the Milton Keynes study areas are

dependent on the type of housing and density that is envisaged is included in Appendix E – SUDS

Options Details.

The SUDS Hierarchy

The EA and DEFRA currently suggest that the SUDS hierarchy is adopted when considering SUDS

techniques to be adopted for new development. This lists the order in which different SUDS

techniques should be considered for a site in terms of their considered sustainability. SUDS

techniques at the top of the hierarchy are preferable for their potential ecological and water quality

benefits.




Most

Sustainable SUDS technique Flood Reduction

Pollution

Reduction

Landscape and

Wildlife Benefit

Living roofs � � �

Basins and ponds

- Constructed wetlands

-Balancing ponds

-Detention basins

-Retention ponds

� � �

Filter strips and swales � � �

Infiltration devices

-soakaways

-infiltration trenches and

basins

� � �

Permeable surfaces and

filter drains

-gravelled areas

-solid paving blocks

-porous paviors

� �

Least

Sustainable

Tanked systems

-oversized pipes/tanks

-storms cells

�

Figure 9-1: SUDS Hierarchy

Source: SUDS - A Practical Guide, Environment Agency Thames Region

9.3.3 Infiltration SUDS

Infiltration is a key factor in reducing runoff rates and volumes, as it reduces the reliance on surface

or engineered storage systems such as balancing ponds or storage tanks. Figure 9-1 places some

surface storage features near to the top of the hierarchy list on the basis of habitat creation and water

quality benefits. The benefits of such systems is considered in Section 9.3.4; however, encouraging

natural infiltration by creation of open grassland landscaping (where contamination is not an issue)

should be encouraged first for large developments to maximise natural runoff rate reduction and to

encourage natural recharge of groundwater systems.




Maximisation of green infrastructure and open space is recommended for large new development

areas where the soil and geology is sufficiently permeable to make it a feasible option. Infiltration can

also be encouraged via managed SUDS techniques such as soakaways, swales or infiltration

trenches.

Infiltration based SUDS would be subject to site-specific ground investigation works by the developer.

Limitations

Given that much of the study area is underlain by impermeable geology either Boulder Clay or Oxford

Clay (which lies below the Boulder Clay), infiltration is not a key consideration for new development in

Milton Keynes. Indeed the majority of surface water generated from Milton Keynes is attenuated by a

series of purpose built attenuation lakes.

Further to the south lies the Woburn Sands, which is generally more permeable than the clayey strata

- the draft Level 1 SFRA states that the IDB have expressed concerns that increased development

and use of infiltration based SUDS in the area could lead to localised groundwater flooding.

The issue of groundwater flooding could also occur along the northern boundary of Milton Keynes

and where the River Great Ouse flows through part of northern development area. The river through

this section is running across the Great Oolite sequence, a Major Aquifer and which will probably

contribute to flow to river for at least part of the year. A line running west-southwest to east-northeast

and dissecting the Northern development area represents the boundary between the Great Oolite

sequence and clayey strata to the south of this line.

Groundwater Quality - Vulnerability

Groundwater resources are vulnerable to contamination from both direct sources (e.g. into

groundwater) or indirect sources (e.g. infiltration of discharges onto land which in turn may feed down

to the groundwater). Groundwater vulnerability within the study area has been determined by the EA,

based on a review of aquifer characteristics, local geology and the leaching potential of soils. The

vulnerability of the groundwater is important when advising on the suitability of SUDS.

According to the EA’s large scale groundwater vulnerability map (1:100,000), the main part of Milton

Keynes is defined as Non-Aquifer (this area being coincident with Oxford Clay outcrop). The Great

Oolite outcrop to the north is defined as a Major Aquifer with Intermediate vulnerability. As already

mentioned, the Great Oolite outcrop area encroaches onto the edge of the broadly defined Northern

study area. The Lower Greensand to the south is also a Major Aquifer and in the High vulnerability

classification. However this area does not to encroach onto either the South Western or Eastern

study areas.

Source Protection Zones

The Environment Agency defines groundwater SPZs around all major groundwater abstraction

points. SPZs are defined to protect areas of groundwater that are used for potable water supply,




including both public and private supplies (including mineral and bottled water), or where the water is

used in the production of commercial food and drinks.

SPZs are defined based on the time it takes for pollutants to reach an abstraction point from any

point at the water table. It does not include the time taken for water to infiltrate from the surface down

to the water table. This transmission time enables the EA to define 3 zones around a groundwater

abstraction point.

Zone 1 (Inner Protection Zone) – This is defined as ‘any pollution that can travel to the borehole

within 50 days from any point within the zone is classified as being inside zone 1’,

Zone 2 (Outer Protection Zone) – This is defined as the area that ‘covers pollution that takes up to

400 days to travel to the borehole, or 25% of the total catchment area – whichever area is the

biggest’,

Zone 3 (Total Catchment) - The total catchment is the total area needed to support removal of water

from the borehole, and to support any discharge from the borehole,

Depending on the nature of the proposed development and the location of the development site with

regards to the SPZs, restrictions may be placed on the types of SUDS appropriate to certain areas.

Infiltration into SPZ1 is generally only permitted for clean roof runoff. Runoff from roads and car

parks is not acceptable in SPZ1 and is only acceptable in SPZ2 if there are sufficient controls in

sources of contamination (e.g. oil separators) and that there is sufficient depth between the

unsaturated soil into which the water is drained and the saturated water table in the geology below.

The SPZ designations for Milton Keynes and surrounds are shown in Figure 9-2.




SPZ Zones

Zone 1 – Inner Protection Zone

Zone 2 – Outer Protection Zone

Zone 3 – Total Catchment

Figure 9-2: Milton Keynes Source Protection Zones

Source: EA Website

Figure 9-2 shows that there are two Zone 1 SPZs (coloured red) to the southeast of Milton Keynes.

These zones are all within the outcrop of Woburn Sands (Lower Greensand (LGS)) of the Cretaceous

Period). The shape of groundwater catchment zone for the more southerly of these sources implies a

northwest-southeast groundwater flow direction. Although in the case of the more northerly source

(around Aspley Guise), the groundwater flow direction is more northerly. The close proximity of this

source to the edge of LGS outcrop apparently causes the Zone 3 – total catchment area for this

source to extend out in both westerly and easterly direction, which would indicate that the hydraulic

gradients in this area are quite gentle. There are no further SPZs shown on the EA website relating

to Milton Keynes and the surrounding areas.

Central Area

There are no groundwater source protection zones adjacent to the Central Area.

Eastern Area

See comments below on South Western Area.

Western Area

There are no groundwater source protection zones adjacent to the Western Area.




Northern Area

There are no groundwater source protection zones adjacent to the Northern Area.

South Western Area

The SPZs to the southeast of Milton Keynes all occur on the outcrop of Woburn Sands (Lower

Greensand – LGS). The catchment areas of these sources do not extend beyond the outcrop of LGS

and therefore they will not extend into the nearest development sites to these sources e.g. South

Western and Eastern Areas.

Although it is not clear on what the precise direction of groundwater flow is beneath Milton Keynes

within the clayey strata, any movement which does take place within these layers is likely to do so at

a very slow rate. This fact combined with the relative distance of the South-Western and Eastern

study areas from these SPZs will mean that activities within these areas are unlikely to represent a

threat to these sources.

It should be noted that below the clayey strata beneath Milton Keynes lie the Kellaway Beds in which

the regional groundwater flow has been assessed to be in a direction from southwest to northeast.

This means that any pollution present at depth beneath Milton Keynes is most likely to be not in the

direction of the sources situated southeast of Milton Keynes, and instead towards the northeast along

the line of the River Great Ouse.

Land East of M1

There are no SPZs adjacent to the land east of the M1.

Rural Areas

There are no SPZs adjacent to the Rural Areas.

9.3.4 Link to Green Infrastructure

Green Infrastructure is a network of protected sites, nature reserves and green spaces that occur at

all scales from the urban centre to the rural countryside. The aim of the Milton Keynes Green

Infrastructure Plan is to identify environmentally sensitive areas and provide a long term plan for

enhancing their ecosystems, recreational and cultural significance. One of the specific objectives is to

undertake a sensitivity analysis for the development sites to identify green infrastructure links from

and to the rural and urban areas.

The report notes the importance of the river or ‘green’ corridors as natural ecological systems. The

opportunities in the area have been identified as enhancing the links to and along the Rivers Great

Ouse, and Ouzel and smaller watercourses such as Broughton Brook; and the incorporation of small

scale SUDS and the possibility of strategic SUDS adjacent to the rivers, as has also been highlighted

in the Expansion Area development frameworks. The creation of linkage with green infrastructure




vision is perhaps greatest for the larger Eastern and Western Areas as there is potential for strategic

scale SUDS such as balancing lakes to link with the corridor of the River Great Ouse and the River

Ouzel. This is particularly pertinent given that infiltration is likely to be significantly constrained in

many of the development sites due to unsuitable underlying geology.

9.4 Flood Risk Management Summary

In summary, the following key flood risk management points can be made regarding the site.

• Many areas, but more specifically the Central and the South Western and Western Areas, are

likely to be significantly limited in terms of opportunities for utilisation of infiltration SUDS due to

unsuitable underlying geology,

• Potential contamination of the SPZs within the Eastern and South Western Areas is a risk with

development activities associated with these areas,

• The Eastern Area and Western Area provide the best opportunities for linking with green

infrastructure opportunities in the town via linking surface water attenuation features such as

swales and balancing ponds to existing green corridors and the proposed Bedford –Milton

Keynes waterway link,

• Significant preliminary works (in the form of Development Frameworks) have already been

undertaken. These partially determine the scope and potential for surface water management

in the main development areas. . Some of these development areas may contain more than

one sub-catchment and it would then be appropriate to agree different rates of discharge to the

individual watercourses on site. At this stage it may be more relevant to refer to the guidance in

the Preliminary Rainfall Runoff Management for Developments or the Interim Code of Practice

for SUDS These Development Frameworks should be developed further and implemented in

conjunction with the key stakeholders including the EA during the Stage 2 WCS. They should

also be used as models, for the areas where no Development Framework currently exists.




10 Ecological Assessment

10.1 Objectives and Approach

The initial Stages (screening stages) of a Habitats Regulations Assessment have been undertaken

for the first stage of the Outline Stage 1 WCS. Until the development areas and development

scenarios are agreed in detail following review of all planning considerations, it is not possible to

complete a full assessment on the WCS. This will be a requirement of the Stage 2 Detailed strategy,

but a screening study for the Appropriate Assessment is suitable for a Stage 1 WCS in order to

identify if they are any ecological constraints to the outline study.

As well as the European Sites potentially affected, the screening study has considered other

nationally, regionally and local designated sites such that a comprehensive assessment of ecological

impacts of the WCS is considered.

10.1.1 Scope of Assessment

The nearest European site17

to any of the Milton Keynes growth areas is the Chiltern Beechwoods

Special Area of Conservation (SAC) (Ashridge Commons & Woods SSSI) situated approximately

25km to the southeast. This site is not particularly hydrologically sensitive and is considerably outside

any possible zone of influence from water abstraction or discharge associated with Milton Keynes.

The nearest statutory sites18

to any of the growth areas are shown in Table 10-1.

17 European sites: Widely used term for those internationally important wildlife sites designated in order to comply with the obligations of the EC Birds Directive (1979) and EC Habitats Directive (1992) 18 Statutory site: Wildlife sites designated under national legislation, specifically the National Parks & Access to the Countryside Act 1949 and Wildlife & Countryside Act 1981 (as amended). These are Sites of Special Scientific Interest (SSSI), National Nature Reserves (NNR) and Local Nature Reserves (LNR)




Table 10-1: Statutory Sites Adjacent to Milton Keynes

Site Location in

terms of study areas

19

Character Hydrological sensitivity

Howe Park Wood SSSI

Within the southern corner of the Western Area

Dry woodlands

There are ponds within this site but it is uncertain at this stage as to whether they

are hydrologically connected to watercourses or aquifers

Oxley Mead SSSI

Within the southern corner of the Western Area

Flood meadows Highly hydrologically sensitive, linked to

the Shenley Brook

Marston Thrift SSSI

To the south east of the Land East

of M1

A series of ancient woodlands and small ponds coupled with

drier habitats such as grassland

There are ponds within this site but it is uncertain at this stage as to whether they

are hydrologically connected to watercourses or aquifers

Blue Lagoon

LNR

Within the South Western Area

A series of wetlands and small ponds coupled with drier

habitats such as grassland and woodland

Hydrologically sensitive, linked to the Water Eaton Brook, a tributary of the River

Ouzel that in turn flows into the Great Ouse

Kings Wood National Nature Reserve lies just outside the south eastern boundary of Milton Keynes

Unitary Authority, but this is more than 3km from the eastern boundary of the nearest study area

(South Western Area).

The potential water sources for development were outlined in Section 7. It is reasonable to conclude

that any increased volumes of treated sewage effluent generated by the growth areas will be

discharged to these same watercourses, principally via the Cotton Valley WwTW.

The greatest ecological water quality issue associated with the new growth areas is the increase in

the loading of phosphorus that might be expected to result from an increased volume of treated

effluent being discharged to surface watercourses. For the recent years (2003 to 2006) the Rivers

Great Ouse and Ouzel generally achieved the RQO Grade 3 (‘Moderate Ecological Status’) in all

cases. The most prominent feature of the summary data was the consistently high nutrient grades for

Nitrogen (N) and Phosphorous (P). In the River Great Ouse, the Grades between 2003 and 2006

were always ‘very high’ for phosphate, and ‘high’ for nitrate. The sources of phosphorus to water are

many and varied, but can be conveniently ascribed to agricultural (grass and arable) and non-

agricultural (large WwTW, trade discharges, smaller WwTW and domestic systems). Much

investment has been undertaken to improve discharges from major point sources such as larger

WwTWs (>10,000 population equivalent [PE]) and there is increasing attention given to diffuse

sources.

The possible impacts that require consideration in this report are therefore:

• Reduction in flow rates and volumes, to such a degree that damage is caused to designated

sites,

19 Although there may be other impacts on these sites associated with placing growth in these areas, only hydrological impacts are considered in this report given that it is focussed on the Water Cycle Strategy




• Increased phosphorus load (and potentially concentration) in downstream sites, coupled with

an increase in total oxidized nitrogen, potential lowering of dissolved oxygen and an increase

in biological oxygen demand (although EA comments are that increased phosphorus load

impacts will be negligible due to already high existing levels),

• Potential increase in water velocity and levels in downstream sites, notable at low/normal

flows, as a result of the additional wastewater volumes entering the river,

• Drawdown of water within Water Eaton Brook due to possible abstraction from the River Ouzel,

leading to adverse effects on the Blue Lagoon LNR.

10.1.2 Methodology

The need for Appropriate Assessment is set out within Article 6 of the EC Habitats Directive 1992,

and interpreted into British law by Regulation 48 of the Conservation (Natural Habitats & c)

Regulations 1994 (Box 1). The ultimate aim of appropriate assessment is to “maintain or restore, at

favourable conservation status, natural habitats and species of wild fauna and flora of Community

interest” (Habitats Directive, Article 2(2)). This aim relates to habitats and species, not the European

sites themselves, although the sites have a significant role in delivering favourable conservation

status.

Box 10-1: The legislative basis for “Appropriate Assessment”

In the past, the term “Appropriate Assessment” has been used to describe both the overall process

and a particular stage of that process (see below). Within recent months, the term Habitat

Regulations Assessment has come into use in order to refer to the process that leads to an

Habitats Directive 1992 Article 6 (3) states that: “Any plan or project not directly connected with or necessary to the management of the site but likely to have a significant effect thereon, either individually or in combination with other plans or projects, shall be subject to appropriate assessment of its implications for the site in view of the site's conservation objectives.” Conservation (Natural Habitats &c. Regulations) 1994 Regulation 48 states that: “A competent authority, before deciding to … give any consent for a plan or project which is likely to have a significant effect on a European site … shall make an appropriate assessment of the implications for the site in view of that sites conservation objectives”. “… The authority shall agree to the plan or project only after having ascertained that it will not adversely affect the integrity of the European site”.




“Appropriate Assessment”, thus avoiding confusion. Throughout this report, Habitat Regulations

Assessment is used to refer to the overall procedure required by Regulation 48 of the Conservation

(Natural Habitats &c.) Regulations 1994 (as amended 2007).

In practice, Habitats Regulations Assessment of projects can be broken down into three discrete

stages, each of which effectively culminates in a test. The stages are sequential, and it is only

necessary to progress to the following stage if a test is failed. The stages are:

Stage 1 – Likely Significant Effect Test

This is essentially a risk assessment, typically utilising existing data, records and specialist

knowledge. The purpose of the test is to decide whether ‘full’ Appropriate Assessment is required.

The essential question is:

”Is the project, either alone or in combination with other relevant projects and

plans, likely to result in a significant adverse effect upon European sites?”

If it can be demonstrated that significant effects are unlikely, no further assessment is required.

Stage 2 – Appropriate Assessment

If it cannot be satisfactorily demonstrated that significant effects are unlikely, a full “Appropriate

Assessment” will be required. In many ways this is analogous to an Ecological Impact Assessment,

but is focussed entirely upon the designated interest features of the European sites in question.

Bespoke survey work and original modelling and data collation are usually required. The essential

question here is:

“Will the project, either alone or in combination with other relevant projects

and plans, actually result in a significant adverse effect upon European sites,

without mitigation?”

If it is concluded that significant adverse effects will occur, measures will be required to either avoid

the impact in the first place, or to mitigate the ecological effect to such an extent that it is no longer

significant. Note that, unlike standard Ecological Impact Assessment, compensation for significant

adverse effects (i.e. creation of alternative habitat) is not permitted at the Appropriate Assessment

stage.

Stage 3 – Imperative Reasons of Overriding Public Interest (IROPI) Test

If a project will have a significant adverse effect upon a European site, and this effect cannot be

either avoided or mitigated, the project cannot proceed unless it passes the IROPI test. In order to

pass the test it must be objectively concluded that no alternative solutions exist. The project must be

referred to Secretary of State on the grounds that there are Imperative Reasons of Overriding Public

Interest as to why the plan should nonetheless proceed. The case will ultimately be decided by the

European Commission.




This report deals with the first stage of Habitat Regulations Assessment – the Likely Significant Effect

Test.

10.2 Sites within Milton Keynes Unitary Authority

There are no European sites within or local to Milton Keynes Unitary Authority.

10.3 Sites of Special Scientific Interest

10.3.1 Howe Park Wood SSSI (SP832343)

This site is ancient woodland with ponds. Although the woodland is not particularly hydrologically

sensitive, the ponds clearly are sensitive and it is uncertain at this stage as to whether they are

hydraulically linked with any aquifers or watercourses from which abstraction would be likely to take

place. This should be investigated at the next stage.

10.3.2 Oxley Mead SSSI (SP818348)

This flood meadow site is highly hydrologically sensitive and is hydraulically linked to the Shenley

Brook. It is not known at this screening stage as to whether the brook is hydraulically linked with any

aquifers or watercourses from which abstraction would be likely to take place. This should be

investigated at the next stage.

10.3.3 Marston Thrift SSSI (SP973417)

This SSSI is predominantly an ancient ash/maple woodland which also supports damp grassland

communities, including pendulous sedge (Carex pendula) and rushes (Juncus spp). There are also

woodland streams and ponds. Although the woodland is not particularly hydrologically sensitive, the

ponds clearly are sensitive and it is uncertain at this stage as to whether they are hydraulically linked

with any aquifers or watercourses from which abstraction would be likely to take place. This should

be investigated at the next stage.

10.4 Local Nature Reserves

10.4.1 Blue Lagoon LNR

The Blue Lagoon Local Nature Reserve lies on the site of a former brickworks. Two pits were

excavated here. The northern Water Eaton pit was flooded in the 1940's when the Water Eaton

Brook broke its banks. The brickworks were demolished in 1970 and the southern Flettons pit was

used for landfill in the early 1980's. This area has now been landscaped into an attractive string of

ponds and hills planted with woodland. Around the Blue Lagoon natural colonisation of the spoil

heaps has formed grassland and scrub woodland. The grassland is especially rich in plants and




animals including some typical of chalk downland but very rare in North Buckinghamshire. The re-

landscaped Flettons pit with its small ponds has greatly increased the amount of shallow water

habitat. Between the ponds and plantations areas were left unseeded for wild plants to colonise.

10.4.2 Screening Opinion

All of the sites identified above are likely to be hydrologically sensitive to varying degrees, and it will

be necessary as part of the next stage to determine whether there is any hydraulic connection

between the Shenley Brook or the ponds within Howe Park Wood SSSI and any watercourses or

aquifers that will be used for abstraction for the public water supply. Until that time, it is not possible

to screen out adverse effects of the water cycle strategy on these two sites.

The Blue Lagoon Local Nature Reserve is hydrologically connected to the River Ouzel through the

Water Eaton Brook and it will therefore be necessary to determine as part of the next stage whether

any possible abstraction from this River might lead to drawdown of water levels within Water Eaton

Brook, leading to adverse effects on the Blue Lagoon LNR.

It is therefore not possible at this stage to screen out adverse effects on any of these three local sites.

10.5 Downstream Sites20 - Special Areas of Conservation

10.5.1 Portholme SAC

This area lies within Huntingdonshire and holds grassland communities of the alluvial flood meadow

type. It is the largest surviving traditionally-managed meadow in the UK, with an area of 104 ha of

alluvial flood meadow (7% of the total UK resource) and the site is designated as an SAC for this

resource. Watercourses on the periphery of the site have populations of some uncommon

invertebrates, including one dragonfly, which is of a nationally restricted distribution. The meadow is

surrounded by channels of the River Ouse, and the Alconbury Brook is close by. In winter and early

spring Portholme is inundated by floodwaters. This provides natural fertilising of the soil and it is this

seasonal flooding coupled with the traditional management that maintains the diversity of the natural

plant communities.

10.5.2 Ouse Washes SAC

The Ouse Washes are located in eastern England on one of the major tributary rivers of The Wash. It

is an extensive area of seasonally flooding wet grassland ('washland') lying between the Old and

New Bedford Rivers (which are hydraulically connected to the River Great Ouse) and acts as a

floodwater storage system during winter months. The cycle of winter storage of floodwaters from the

river and traditional summer grazing by cattle, as well as hay production, have given rise to a mosaic

of rough grassland and wet pasture, with a diverse and rich ditch fauna and flora. The Ouse Washes

20 Only sites understood to be hydrologically linked to the River Great Ouse and situated downstream of Milton Keynes are included




were designated as an SAC for their population of spined loach. This fish is thought to be largely

confined to oxygen rich waters where the substratum consists of fine, organic rich sediment.

10.5.3 The Wash and North Norfolk Coast SAC

The Wash is located on the east coast of England and is the largest estuarine system in the UK. It is

fed by the rivers Witham, Welland, Nene and Great Ouse that drain much of the east Midlands of

England. The Wash comprises very extensive saltmarshes, major intertidal banks of sand and mud,

shallow waters and deep channels.

The eastern end of the site includes low chalk cliffs at Hunstanton. In addition, on the eastern side,

the gravel pits at Snettisham are an important high-tide roost for waders. The intertidal flats have a

rich invertebrate fauna and colonising beds of Glasswort Salicornia spp. which are important food

sources for the large numbers of waterbirds dependent on the site. The sheltered nature of The

Wash creates suitable breeding conditions for shellfish, principally Mussel Mytilus edulis, Cockle

Cardium edule and shrimps. These are important food sources for some waterbirds such as

Oystercatchers Haematopus ostralegus. The Wash is designated as a Special Area of Conservation

for supporting the following features of European importance:

• Subtidal sandbanks,

• Intertidal mudflats and sandflats,

• Shallow inlets and bays,

• Reefs,

• Mediterranean saltmarsh scrub,

• Lagoons,

• Common seal,

• Otter.

10.5.4 Screening Opinion

There are two significant rivers (the Ivel and the Kym) that drain into the River Great Ouse between

Milton Keynes and Portholme SAC. Given that any abstraction from the River Great Ouse at Milton

Keynes is likely to be matched by an increased scale of effluent discharge into the same river and

that additional water volume is added to the Great Ouse by the watercourses identified above, it is

considered unlikely that significant flow reductions in the Great Ouse at Portholme SAC would be

likely as a result of any of the new growth at Milton Keynes, even in combination with other

developments that will abstract water from the Ouse upstream of Huntingdonshire.

Reduced flows are more likely to have an adverse effect on The Wash; siltation resulting from low

flows is already recognised as a problem. Given that additional abstraction from the Great Ouse at




Milton Keynes is likely to be matched by an increased scale of effluent discharge into the same River

and that additional water volume is added to the Great Ouse by the watercourses identified above, it

is considered unlikely that increased abstraction at Milton Keynes will lead to significant reduction of

freshwater entering The Wash SAC.

Increased flows can lead to prolonged flooding of the Ouse Washes SAC and the spined loach (for

which the SAC was designated due to their rarity in Europe, though they are quite common here) is

associated with slow flowing watercourses, such that a significant increase in flow rates may render

the Ouse unsuitable for the species. However, advice from the EA is that Spined Loach is a hardy

species and that they should not be affected by any increased flow. However, given that the

discharge of treated sewage effluent to the Great Ouse from Milton Keynes is likely to be matched by

an increase in abstraction from the same watercourse significant increases in flow are unlikely to

occur as a result of any of the expansion areas at Milton Keynes.

The Environment Agency’s Review of Consents has concluded that, although the concentrations of

phosphorus in the rivers adjacent to The Ouse Washes are considered to be too high, action at other

WwTWs within the Great Ouse catchment will allow the target quality to be met. Funding for the

necessary improvements has been made available in AMP4, and all schemes are to be completed by

the end of 2009. However, there is nonetheless potential for future development to exceed these

standards and require further review of other sources of phosphorus.

There is potential for dilution of any phosphates contained in treated sewage effluent discharged to

the Great Ouse from Milton Keynes due to the four identified tributaries of the Great Ouse upstream

of Portholme SAC, The Ouse Washes SAC or The Wash SAC. However, it is reasonable to conclude

that some of these watercourses may themselves carry large loads of phosphate due to increased

development within the South East and East of England, and diffuse sources. Therefore, on a

cumulative basis, a possible impact on these European sites cannot be discounted (even though

Milton Keynes individual contribution may well be small). It is understood that the main Milton Keynes

WwTW (Cotton Valley WwTW) is already at the limits of Best Available Technology with regard to

phosphate stripping and it may therefore be necessary to review all sources of phosphorus within the

River Ouse catchment in order to maintain the target river concentration at the Ouse

Washes/Portholme Meadow sites.

At this stage it is therefore not possible to screen out adverse cumulative water quality effects on

these three Special Areas of Conservation. This issue will therefore require further exploration at the

next stage.




10.6 Downstream Sites - Special Protection Areas

10.6.1 Ouse Washes SPA

The washlands support both breeding and wintering waterbirds. In summer, there are important

breeding numbers of several wader species, as well as spotted crake Porzana porzana. In winter, the

site holds very large numbers of swans, ducks and waders. During severe winter weather elsewhere,

the Ouse Washes can attract waterbirds from other areas due to its relatively mild climate (compared

with continental Europe) and abundant food resources. In winter, some wildfowl, especially swans,

feed on agricultural land surrounding the SPA. The site was designated as an SPA for regularly

supporting 64,392 waterfowl, including populations of European importance of the following migratory

species:

• Ruff,

• Spotted Crake,

• Bewick's Swan,

• Hen Harrier,

• Whooper Swan,

• Black-tailed Godwit,

• Gadwall,

• Shoveler,

• Pintail,

• Pochard,

• Wigeon.

10.6.2 The Wash SPA

The Wash is of outstanding importance for a large number of geese, ducks and waders, both in

spring and autumn migration periods, as well as through the winter. The SPA is especially notable for

supporting a very large proportion (over half) of the total population of Canada/Greenland breeding

knot Calidris canutus islandica. In summer, the Wash is an important breeding area for terns and as a

feeding area for marsh harrier Circus aeruginosus that breed just outside the SPA. The Wash was

designated as a Special Protection Area for supporting a bird assemblage of international importance

by regularly supporting 400,273 waterfowl and for supporting populations of European importance of

the following migratory species:

• Common Tern,




• Little Tern,

• Marsh Harrier,

• Avocet,

• Bar-tailed Godwit,

• Golden Plover,

• Whooper Swan,

• Ringed Plover,

• Sanderling,

• Black-tailed Godwit,

• Curlew,

• Dark-bellied Brent Goose,

• Dunlin,

• Grey Plover,

• Knot,

• Oystercatcher,

• Pink-footed Goose,

• Pintail,

• Redshank,

• Shelduck,

• Turnstone.

10.7 Ramsar Sites

10.7.1 The Wash Ramsar Site

The Wash is designated as a Ramsar site for the following reasons:

• The Wash is a large shallow bay comprising very extensive saltmarshes, major intertidal banks

of sand and mud, shallow water and deep channels,

• The site qualifies because of the inter-relationship between its various components including

saltmarshes, intertidal sand and mud flats and the estuarine waters. The saltmarshes and the

plankton in the estuarine water provide a primary source of organic material, which, together




with other organic matter, forms the basis for the high productivity of the estuary.

Internationally important wintering waterfowl assemblage,

• The site supports a wintering waterbird assemblage of international importance.

Species occurring at numbers of international importance are:

• Oystercatcher,

• Grey plover,

• Red knot,

• Sanderling,

• Curlew,

• Common redshank,

• Ruddy turnstone,

• Pink-footed goose,

• Dark-bellied brent goose,

• Common shelduck,

• Northern pintail,

• Dunlin,

• Bar-tailed godwit,

• Ringed plover,

• Black-tailed godwit,

• Golden plover,

• Northern lapwing.

10.7.2 Ouse Washes Ramsar Site

The Ouse Washes is designated as a Ramsar site for the following reasons:

• The site is one of the most extensive areas of seasonally-flooding washland of its type in

Britain,

• The site supports several nationally scarce plants, including small water pepper Polygonum

minus, whorled water-milfoil Myriophyllum verticillatum, greater water parsnip Sium latifolium,

river waterdropwort Oenanthe fluviatilis, fringed water-lily Nymphoides peltata, long-stalked

pondweed Potamogeton praelongus, hair-like pondweed Potamogeton trichoides, grass-wrack




pondweed Potamogeton compressus, tasteless water-pepper Polygonum mite and marsh dock

Rumex palustris,

• Invertebrate records indicate that the site holds relict fenland fauna, including the British Red

Data Book species large darter dragonfly Libellula fulva and the rifle beetle Oulimnius major,

• The site also supports a diverse assemblage of nationally rare breeding waterfowl associated

with seasonally-flooding wet grassland,

• The site supports a wintering waterbird assemblage of international importance.

Species occurring at levels of international importance are:

• Tundra swan,

• Whooper swan,

• Eurasian wigeon,

• Gadwall,

• Eurasian teal,

• Northern pintail,

• Northern shoveler,

• Mute swan,

• Common pochard,

• Black-tailed godwit.

10.8 Sites of Special Scientific Interest

10.8.1 Felmersham Gravel Pits SSSI and Stevington Marsh SSSI

These sites lie approximately 5km east of Milton Keynes and are hydrologically linked to the River

Great Ouse. Therefore excessive abstraction from the Great Ouse during periods of low flow could

potentially lead to drawdown of water within both sites. In addition, increased discharge of treated

sewage effluent could lead to increased phosphate levels and deterioration in water quality.

10.8.2 The Wash SSSI

The whole area is of exceptional biological interest. The intertidal mudflats and saltmarshes represent

one of Britain's most important winter feeding areas for waders and wildfowl outside of the breeding

season. Large numbers of migrant birds, of international significance, are dependant on the rich

supply of invertebrate food. The saltmarsh and shingle communities are of considerable botanical




interest and the mature saltmarsh is a valuable bird breeding zone. In addition the Wash is also very

important as a breeding ground for Common Seals.

10.8.3 Ouse Washes SSSI

The site is one of the country’s few remaining areas of extensive washland habitat. It is of particular

note for the large numbers of wildfowl and waders that it supports, for the large area of unimproved

neutral grassland communities that it holds and for the richness of the aquatic fauna and flora within

the associated watercourse. The grassland communities of the area are characterised by such

grasses as reed and floating sweet-grass Glyceria maxima and G.fluitans, reed canary-grass

Phalaris arundinacea, marsh foxtail Alopecurus geniculatus together with a variety of sedges and

rushes. Typical herbs include amphibious bistort Polygonum amphibium, water-pepper Polygonium

hydropiper and tubular water-dropwort Oenanthe fistulosa. The associated dykes and rivers hold a

great variety of aquatic plants, the pondweeds Potamogeton spp. are particularly well represented.

Other aquatic species include the fringed water-lily Nymphoides peltata, greater water-parsnip Sium

latifolium and the four species of duckweeds Lemna spp.

The limnological interest of the Ouse Washes is further diversified by the Old Bedford River and River

Delph, both good examples of base-rich, sluggish, lowland rivers. The flora includes the fan-leaved

water-crow foot Ranunculus circinatus, yellow water-lily Nuphar lutea, arrowhead Sagittaria

sagittifolia, long-stalked pondweed Potamogeton praelongus, perfoliate pondweed Potamogeton

perfoliatus, and river water-dropwort Oenanthe fluviatilis. The associated aquatic and semi-aquatic

fauna is similarly diverse.

10.9 Overall Screening Opinion

At this stage it is therefore not possible to screen out adverse cumulative water quality effects on a

number of designated sites. This issue will therefore require further exploration at the next stage:

• Portholme SAC (water quality),

• Ouse Washes SAC/SPA/Ramsar site/SSSI (water quality),

• The Wash SAC/SPA/Ramsar site/SSSI (water quality),

• Felmersham Gravel Pits SSSI (water abstraction and water quality),

• Stevington Marsh SSSI (water abstraction and water quality),

• Howe Park Wood SSSI (water abstraction),

• Oxley Mead SSSI (water abstraction),

• Blue Lagoon LNR (water abstraction).




Reduced flows are likely to have an adverse effect on The Wash; siltation resulting from low flows is

already recognised as a problem. Given that additional abstraction from the Great Ouse at Milton

Keynes is likely to be matched by an increased scale of effluent discharge into the same River and

that additional water volume is added to the Great Ouse by the watercourses identified above, it is

considered unlikely that increased abstraction at Milton Keynes will lead to significant reduction of

freshwater entering The Wash SPA.

Increased flows can lead to prolonged flooding of the Ouse Washes SPA and the spined loach (for

which the SAC was designated) is associated with slow flowing watercourses, such that a significant

increase in flow rates may render the Ouse unsuitable for the species. However, given that the

discharge of treated sewage effluent to the Great Ouse from Milton Keynes is likely to be matched by

an increase in abstraction from the same watercourse significant increases in flow are unlikely to

occur as a result of any of the expansion areas at Milton Keynes.

High flows may also increase diffuse runoff, and cause bed/bank sediment (together with sediment

bound substances such as total phosphorus) to become entrained in the water column. Thus,

mobilisation and transport of water soluble and sediment bound substances can be expected during

storm events.

The Environment Agency’s Review of Consents has concluded that, although phosphorous levels in

the rivers adjacent to The Ouse Washes are considered to be too high at the moment, action at other

WwTWs within the Great Ouse catchment should allow the target quality to be met. Funding for the

necessary improvements has been made available in AMP4, and all schemes are to be completed by

the end of 2009. However, there is nonetheless potential for future development to exceed these

standards and potentially make review of other phosphorus sources more desirable.

There is potential for dilution of phosphates contained in treated sewage effluent discharged to the

Great Ouse from Milton Keynes due to the four identified tributaries of the Great Ouse upstream of

The Ouse Washes SPA or The Wash SPA. However, it is reasonable to conclude that some of these

watercourses may themselves carry large loads, or suffer undesirable concentrations of phosphate

due to either increased development within the region, and/or due to diffuse sources. Therefore, on a

cumulative basis, a possible impact on these European sites cannot be discounted (even though

Milton Keynes’ individual contribution may well be small. It is understood that the main Milton Keynes

WwTW (Cotton Valley WwTW) is already at the limits of Best Available Technology with regard to

phosphate stripping and it may therefore be necessary to further review the contribution of all sources

of phosphorus within the River Ouse catchment in order to maintain the target river concentration at

the Ouse Washes and The Wash sites.

Since Milton Keynes town is the nearest major urban area upstream of both Felmersham Gravel Pits

SSSI and Stevington Marsh SSSI (approximately 30km and 42km upstream, respectively, taking river

meanders into account) and since no major watercourses drain to the Great Ouse between Milton




Keynes and either SSSIs (such that opportunities for dilution are limited) it is reasonable to assume

that the new growth areas may contribute to increased phosphorus concentrations of these sites

which could potentially lead to adverse effects on the wetland species for which the sites were

designated, and increased duration of flooding during periods of high flow. This would need to be

investigated further at the next stage.

However, it may well be that after more detailed consideration at the next stage, impacts on many of

these sites can be ruled out.




11 Water Quality / Water Framework Directive

The Water Framework Directive (WFD) was passed into UK law in 2003. The competent authority

responsible for its implementation is the Environment Agency in England and Wales.

The overall requirement of the directive is that all water bodies in the UK must achieve “good

ecological and good chemical status” by 2015 unless there are grounds for derogation.

The WFD will for the first time combine water quantity and water quality issues together. The link

between good physicochemical and ecological status is recognised in the WFD classification system

whereby you cannot have one without the other. Whilst the physicochemical standards are important

in developing measures to achieve ecological outcomes, it is the sum of the target biological

elements that is at the heart of the WFD. The biological elements of ecological status will be

expressed as Ecological Quality Ratios (EQR) which expresses observed data compared with type

specific reference data.

The WFD combines previous water legislation and in certain areas strengthens existing legislation.

An integrated approach to the management of all freshwater bodies, groundwaters, estuaries and

coastal waters at the river basin level will be adopted. Involvement of stakeholders is seen as key to

the success in achieving the tight timescales set by the directive.

All Water bodies in the UK will be designated a status based on their ecological, and chemical

quality. The status will range from poor through to very good and standards are being developed

with which to measure this status covering a range of criteria including water quality, biological

quality, and morphology. As stated, the aim is for all water bodies to reach ‘good status’ (or good

ecological potential in the case of artificial or heavily modified watercourses) or higher by 2015. In

order to do so, the Environment Agency in conjunction with the WFD UK Technical Advisory Group

(UKTAG) is developing a series of River Basin Management Plans (RBMPs) for the major River

Basins of the UK. The RBMPs will be published in draft in 2008 and as final in 2009 and will contain

a Programme of Measures which will set out the changes that need to be implemented in order to

bring the water bodies which are currently failing the required standards up to good status.

Milton Keynes and its rivers are included in the Anglian River Basin District which covers 27,890 km2

ranging from Lincolnshire in the north to Essex in the south and Northamptonshire.

The standards are currently in draft form and will not be finalised until the RBMPs are published in

late 2009. However, because the WFD requirements will largely superseded the current statutory

and guideline environmental standards from 2010, it is important that the WCS considers the

requirements for meeting them such that the impact of growth on future compliance with legislative

requirements is understood and can be managed at an early stage in the planning. The WCS should

also be a driver for improvements in water quality standards.




Prior to the finalisation of the Anglian RBMP, the EA have undertaken a draft assessment of the

characterisation of risk for water bodies in the Anglian River Basin. The summary of the

characterisation is shown in Table 11-1.

Table 11-1: Summary of WFD Risk Characterisation, Anglian RBD

Risk factor Watercourse Risk Characterisation

Point source acidification River Ouse and River Ouzel Not at Risk

Diffuse and Point source ammonia River Ouse and River Ouzel At Risk

Diffuse and Point source BOD River Ouse and River Ouzel Not at Risk

Diffuse and Point source Oxidised Nitrogen21

River Ouse and River Ouzel At Risk

Diffuse and Point source Phosphate River Ouse and River Ouzel At Risk

Diffuse – mines and minewaters River Ouse and River Ouzel Not at Risk

Whilst the draft risk characterisation is considered to be a broad-brush assessment at this stage in

the RBMP process, it does given an indication of the pressures on the two key river systems in and

around Milton Keynes. In particular, it lends support to the fact that diffuse and point source nutrient

enrichment are a key concern. However, it should be noted that catchment specific investigations

and modelling would help to confirm the actual status of the watercourses around Milton Keynes, and

determine proportions of loads from each source (point or diffuse, urban or agricultural).

11.1 Water Framework Directive Standards

In terms of water quality standards, the current River RQO and GQA programme has been very

successful, particularly in assessing the impact of point source discharges on watercourses. In

conjunction with the Urban Wastewater Treatment Directive (UWTD), investment to the larger

WwTWs has improved discharges considerably. There are still problems however. In particular,

rural sources, especially agricultural diffuse pollution (mainly nutrients, sediment, pesticides), smaller

WwTWs, industry, urban areas and roads can cause water quality problems.

In relation to development considered in this WCS, the key concerns are water availability, quantity

and quality of runoff from urban areas and roads, and discharges from domestic houses. These can

all have a large impact on the water environment, and are interrelated. For example, river flow can

affect concentrations of substances such as nitrate. However, existing schemes do not adequately

assess the impact of such sources. In particular, they do not quantify the effect on the aquatic

environment.

The Water Framework Directive (WFD) classifies water in a different way, using new and revised

environmental standards to assess whether environmental conditions are good enough to support

appropriate aquatic life for the system in question. The Directive requires that all inland and coastal

21 Total Oxidised Nitrogen is the considered as combined Nitrate and Nitrite.




water bodies reach at least "good ecological status” by 2015 – subject to certain exemptions, which

allow alternative objectives to be set in cases where it is infeasible or disproportionately expensive to

achieve good status.

The WFD came into force on 22nd December 2000 (although not enacted into the UK legislative

system until 2003), and in accordance with the agreed implementation timetable, monitoring under

the Directive commenced on 22nd December 2006. The Directive requires that a draft River Basin

Management Plan (RBMP) to maintain or improve the aquatic environment is established by the end

of 2008, and updated every six years; the plans will be finalised at the end of 2009 following review

by the EC.

It is generally expected that the new classification will reduce the number of waterbodies achieving

‘good ecological status’, since rivers will be graded by the worst parameter of the revised monitoring

scheme. The new classification system includes rivers, lakes, estuaries, coastal waters and

groundwaters. The WFD requires surface water bodies to be classified into one of five ecological

status classes, and one of two chemical status classes. In addition, there are two stages to

groundwater classification.

From 2007 to 2009, England and Wales will continue to report results based on the GQA monitoring

system, with separate indicators for biology and chemistry. In England, however, a reduced network

will be used, so that resources can be re-directed to implementing the WFD monitoring programme.

During this time, the existing GQA and WFD approaches will report in parallel. This will enable

differences between the two approaches to be distinguished.

The status of each surface water body is judged using separate ‘Ecological classification’ and

‘Chemical classification’ systems. The overall status of the water body will be determined by

whichever of these is the poorer. To achieve ‘good status’ overall, a water body must achieve both

good ecological and good chemical status.

11.1.1 Ecological classification

The Ecological classification system has five classes, from high to bad, and uses biological,

physicochemical, hydro morphological and chemical assessments of status.

• Biological assessment uses numeric measures of communities of plants and animals (e.g. fish

and rooted plants).

• Physicochemical assessment documents parameters such as temperature and nutrient

concentrations.

• Hydromorphological assessment to document water flow and physical habitat.

As of December 2007, UKTAG had derived standards for some of the more important chemical

parameters in freshwaters, as shown in Table 3. The standards will differ based on the ‘typology’ of




each water body; rivers, lakes, transitional and coastal waters, groundwater. A summary of initial

classification for rivers is presented below, based on UKTAG (2007). In this case, just two

parameters (dissolved oxygen and phosphorus) are presented as examples, but it is important that

studies on water quality bear the full list of new standards in mind. Although the existing GQA

scheme is likely to run until 2009, the new standards are being introduced concurrently, and any

differences in water quality as a result of the new standards should be fully explored.

The general typology for rivers is based on alkalinity and altitude, as shown in Table 11-2. However,

for dissolved oxygen and ammonia, the typology was simplified into just two types, as shown in Table

11-3: . These typologies should be used to define the dissolved oxygen standard for a particular

watercourse typology, as shown in Table 11-4: . The standards in Table 11-4: were developed on

the basis of oxygen conditions associated with macroinvertebrates, as these are the most sensitive

biota to DO.

Table 11-2: Basic typology for rivers (WFD)

Alkalinity (mg/l CaCO3) Site Altitude

<10 10 to 50 50 to 100 100 to 200 >200

<80 m Type 3 Type 5 Type 7

>80 m Type 1 Type 1

Type 4 Type 6

Table 11-3: Final typology for oxygen and ammonia for rivers (WFD)

Type Alkalinity Type

Upland and low alkalinity Types: (1+2, 4 and 6

Lowland and high alkalinity22

Types: 3, 5 and 7

Table 11-4: Standards for oxygen in rivers (WFD)

Dissolved oxygen (% saturation)10-percentile

Type High Good Moderate Poor

Upland and low alkalinity 80 75 64 60

Lowland and high alkalinity 70 60 54 45

The impacts of elevated concentrations of nutrients in freshwater systems, especially phosphorus,

are widely studied. The most common impact is enhanced growth of plants and algae, which can

affect watercourses in several ways. River channels can become blocked, exacerbating low flow

conditions; diurnal fluctuations of oxygen content in the water can occur due to respiration of

22 Where a lowland, high alkalinity water body is a salmonid river, then the standards for the upland, low alkalinity type will apply.




macrophytes during the hours of darkness, potentially affecting fish; growths of blue-green algae can

be stimulated which can cause adverse affects in animals.

For revised nutrient standards in rivers, UKTAG (2007) identified that ecological sensitivity could be

related to alkalinity and altitude. The resulting river typology can be seen in Table 11-5: .

Table 11-5: River typology (WFD)

Annual mean alkalinity (mg/l calcium carbonate) Altitude

< 50 > 50

< 80 m Type 1n Type 3n

> 80 m Type 2n Type 4n

When developing the standards for nutrients in rivers, Guthrie et al (2006) reported that diatoms

showed greater sensitivity to nutrients than macrophytes, and these were subsequently used to

develop the standards shown in Table 11-6. Also included in Table 11-6, are guideline values

produced by the Environment Agency which are commonly referred to, as well as values

recommended by the Habitats Directive.

UKTAG (2007) recognise that the relationship between nutrients and water quality is not

straightforward. Thus, it is recommended that an indication of ‘actual or potential’ biological impact is

needed in addition to a finding of high concentrations of SRP.

Nitrate is already covered by legislation which proscribes a Statutory Limit of 50 mg NO3/l (11.3 mg

NO3-N/l) as described previously. However, these limits are largely based on protection of

freshwater for the purposes of drinking water. UKTAG (2007) consider that although nitrate may

have a role in eutrophication in some types of freshwaters, there is insufficient understanding for new

standards or conditions. For this reason, no new standards for nitrate in water have been

recommended.




Table 11-6: Phosphorus standards in rivers under WFD standards, existing GQA guidelines and

habitats directive, for comparison

SRP (µg/l) (annual mean) under WFD

Type High Good Moderate Poor

1n 30 50 150 500

2n 20 40 150 500

3n & 4n 50 120 250 1,000



SRP (µg/l) (annual mean) under existing guidelines

1 2 3 4 5

SRP (µg/l) 20 60 100 200 1,000

Status Very low Low Moderate High Very high



SRP (µg/l) (annual mean) under Habitats Directive

Headwaters Most rivers Large rivers

Natural (1) 0-20 20-30 20-30

Guideline (2) 20-60 40-100 60-100

Threshold (3) 40-100 60-200 100-200

Due to the uncertainty surrounding the effect of applying these revised standards, UKTAG have

estimated the change in classification due to the new standards, compared to the old GQA standards

for England, Wales and Scotland. When the 95 percent confidence interval is applied to the data

presented in Table 11-9, approximately 12% of rivers in England currently fail the existing RQO for

either BOD, DO or ammonia. Under the revised standards, this increases to approximately 20%.

It should be emphasised again that that the existing guidance for phosphorus is currently not usually

used to base decisions on water quality. More detailed investigations are usually undertaken to

demonstrate cause and effect with regards to impact on aquatic ecology.

Table 11-9: Estimated changes to rivers considered ‘less than good quality’ under existing

and proposed standards in England

Percent of river length reported as ‘less than good’

BOD Dissolved Oxygen Ammonia Phosphorus

Existing Proposed Existing Proposed Existing Proposed Existing Proposed

25.6 18.7 30.8 24.6 14.6 17.3 65 63.3




11.1.2 WFD and protected areas

The WFD state that ecological status for water bodies under the WFD must be interpreted separately

from those standards and objectives set under the legislation for protected areas. Thus, Special

Areas of Conservation (SAC) and Special Protected Areas (SPA) must achieve ‘Favourable

Conservation Status’. Ideally, this would equate to ‘High Ecological Status’ under the WFD, but in

reality the standards and objectives under these designations may differ. Consideration will need to

be given on a site-by-site basis. This has particular implications in relation to the Ouse Washes,

which are in an unfavourable condition and particularly sensitive to eutrophication as a result of

excessive phosphorus.

11.1.3 Chemical classification for priority substances and other pollutants

The Chemical classification system for surface waters, used for the most polluting substances, has

only two classes, ‘good’ or ‘failing to achieve good’. We will assess status by checking whether the

water meets Environmental Quality Standards (EQSs) for substances listed in Annex IX (Dangerous

Substances Directive and associated daughter directives) and Annex X (WFD Priority List

Substances). These standards are being set on a Europe-wide basis and are considered a priority

because of their high potential for pollution.

11.2 WFD and Milton Keynes

11.2.1 Water Quality in Milton Keynes and Surrounding Areas

There are several existing EA RQO/GQA (now known as River Ecology (RE)) water quality

monitoring locations in and around Milton Keynes. Water quality from nine locations on the main

watercourses (River Great Ouse and River Ouzel) were summarised and shown in Table 11-10 and

Table 11-11.




Table 11-10: Water quality summary for the River Ouse around Milton Keynes

River Ecosystem General Quality Assessment

Compliance Chemistry Biology Nitrate Phosphate

River Ouse

Environment Agency Sampling Reach

Target 2003-2005

2004-2006

2003-2005

2004-2006 2002 2005

2003-2005

2004-2006

2003-2005

2004-2006

Reach 1 THORNBOROUGH

MILL...DEANSHANGER BROOK

3 Y Y B B A A 5 5 5 5

Reach 2 DEANSHANGER BROOK

..... CONFL. TOVE 3 Y Y B B A A 5 5 5 5

Reach 3 CONFL. TOVE ..... MOTEL

3 Y Y B A A A 5 5 5 5

Reach 4 TICKFORD

ABBEY...SHERRINGTON BRIDGE

3 Y Y B A A A 5 5 5 5

Reach 5 SHERINGTON....

TYRINGHAM HALL 3 Y Y B B A B 5 5 5 5




Table 11-11: Water quality summary for the River Ouzel around Milton Keynes

River Quality Objective General Quality Assessment

Compliance Chemistry Biology Nitrate Phosphate

River Ouzel

Environment Agency Sampling Reach

Target 2003-2005

2004-2006

2003-2005

2004-2006 2002 2005

2003-2005

2004-2006

2003-2005

2004-2006

Reach 6 LINSLADE WwTW ..... STAPLEFORD MILL

3 Marginal Marginal D (DO) D B B 6 6 5 5

Reach 7 STAPLEFORD MILL .....

EATON LEYS FARM 3 Y Y B B A B 6 6 5 5

Reach 8 M1 ..... OUZEL

3 Y Y C (DO) C C B 5 5 4 4

Reach 9 CONFL. BROUGHTON BRK .... BIRCHMOOR

FARM

3 Y Y B B B B 5 5 5 5




Key for Tables 11.10 and 11.11 (for full description see Section 6.5.2)

GQA Grades

mg N L-1

90 percentile

Dissolved Oxygen

(% saturation)

10 percentile

BOD

mg L-1

90 percentile

Ammonia

A 80 2.5 0.25

B 70 4 0.6

C 60 6 1.3

D 50 8 2.5

E 20 15 9.0

F <20 >15 >9.0

Biological Grades

Classification Description

A - very good Biology similar to that expected for an unpolluted river

B - good Biology is a little short of an unpolluted river

C - fairly good Biology worse than expected for unpolluted river

D - fair A range of pollution tolerant species present

E - poor Biology restricted to pollution tolerant species

F - bad Biology limited to a small number of species very tolerant of pollution

Nutrient Grades

Classification for

phosphate

Grade limit

(mg P/I) average Description

1 0.02 Very low

2 0.06 Low

3 0.1 Moderate

4 0.2 High

5 1.0 Very high

6 >1.0 Excessively high

Classification for nitrate Grade limit

(mg NO3/I) average Description

1 5 Very low

2 10 Low

3 20 Moderately low

4 30 Moderate

5 40 High

6 >40 Very high

For the recent years (2003 to 2006) the Rivers Great Ouse and Ouzel generally achieved the RQO

Grade 3 (‘Moderate Ecological Status’) in all cases. The exception was the River Ouzel, between




Linslade WwTW and Stapleford Mill, where compliance was ‘marginal’ and the cause was low levels

of DO.

Although the River Ouzel achieved RE 3 downstream of the M1, the chemical water quality was fairly

good (grade C) for chemistry and biology.

It should be noted that Table 11-10 does not show a significant failure in RQO compliance that

occurred between Tickford Abbey and Sherington Bridge (downstream Cotton Valley WwTW) during

2001 and 2003. The cause of this failure was alkaline water.

The most prominent feature of the summary data in Table 11-10 and Table 11-11 are the consistently

high nutrient grades for N and P. In the River Great Ouse, the Grades between 2003 and 2006 were

always ‘very high’ for phosphate, and ‘high’ for nitrate. In the River Ouzel, the reaches downstream

of Linslade WwTW were ‘very high’ for nitrate, but the concentrations of phosphate were slightly

smaller (but still ‘high’) than upstream in the reach downstream of the M1 Motorway.

Both the River Great Ouse and the River Ouzel are designated Eutrophic Sensitive Areas under the

Urban Wastewater Treatment Directive (91/271/EEC. Where wastewater (treated WwTW Final

Effluent) is discharged into these areas, it must undergo a tertiary treatment which reduces its impact

on the environment.

Sensitive areas are:

• Natural freshwaters, other freshwater bodies, estuaries and coastal waters which have a large

concentration of nutrients. The critical factor is phosphorus which can cause an excessive

growth of algae and other plants which can affect species living in the water, and the quality of

the water overall. These lakes are called eutrophic. This also covers areas which could

become eutrophic if we take no action. These are designated Sensitive Areas (Eutrophic),

• Surface freshwaters used for drinking water that could contain more nitrates than allowed by

The Surface Water Abstraction Directive (75/440/EEC). These are designated Sensitive Areas

(Nitrate),

• Areas where the water needs treatment additional to secondary treatment to fulfil the

requirements of other EC directives. These are designated Sensitive Areas (Bathing Waters)

and Sensitive Areas (Shellfish waters).

The EA considers that the WwTW at Cotton Valley in Milton Keynes has the capacity to deal with the

increased waste water treatment required to support housing growth (Milton Keynes Council, 2007).

However, in liaison with Natural England, MKC has identified two sites that could potentially be

affected due to the pathway provided by the River Great Ouse, which flows to the Ouse Washes

SPA/SAC. The clear water and abundant macrophytes, is particularly important in the Counter Drain,

and a healthy population of spined loach is known to occur. The SPA designation is due to the site’s

importance as an internationally important habitat for wetland birds.




MKC (2007) consider that the distance of Milton Keynes from the Ouse Washes (approximately 60

km) means that any decrease in water quality associated with increased effluent levels would be

diluted before it reaches the Natura 2000 sites, meaning the impact will be negligible. This is further

supported by the presence of a Development Control Policy in the plan requiring developments to

cause no hydrological disturbance. However, the Ouse Washes are in an unfavourable condition,

largely due to water quality (excessive nutrients) and excessive flooding (especially summer

flooding), thus attention should be given to the role of Milton Keynes water policy as part of a regional

strategy to improve water quality upstream of the Ouse Washes. This must also be considered in

relation to revised ecological and chemical standards under the WFD, and the status of Protected

Areas.

The Ouse Washes is one of two U.K RAMSAR sites to be classified under the Montreux Accord, an

alert mechanism to warn the UK Government of potential threats to the area. The potential threats

identified are an increase in spring flooding which reduces the wet grassland available to waders for

nesting and leads to population decline, and a perceived deterioration in the quality of water from

sources that feed the Washes. Increased concentration of some substances; mainly phosphates, but

also nitrate, alter habitat conditions with resultant effects on the vegetation and animal communities.

11.2.2 Existing and future standards (dissolved oxygen and phosphorus)

Since the future management of UK rivers is dependant on revised and new standards introduced

under the Water Framework Directive, it is appropriate to test some key parameters in order to

assess possible compliance issues with ‘Good Ecological Status’. Failure to meet this standard will

likely be addressed by measures under draft River Basin Management Plans, to be consulted later in

2008. As previously discussed, these are new standards and have not yet been applied by the EA.

The cursory assessment described below is designed as an indication of the impact of two important

chemical parameters, namely dissolved oxygen (DO) and phosphorus, in the form of Soluble

Reactive Phosphate (SRP).

With regards to new water quality standards under the Water Framework Directive, the reaches of

the River Great Ouse and the River Ouzel around Milton Keynes are <80 mAOD, (although a

significant proportion of the river is >80 mAOD upstream of Milton Keynes) of and alkalinity is >500

mg/l CaCO3 Thus the river typology is ‘lowland and high alkalinity’

To achieve ‘Good Status’ for DO, the 10-percentile DO content must exceed 60%. Under this

analysis, only the River Ouzel between Linslade WwTW and Stapleford Mill would fail to reach ‘Good

Status’ for DO (as it did recently under existing chemical GQA Grades).

For phosphorus, the Rivers Great Ouse and Ouzel around Milton Keynes must again be assessed for

typology. Both rivers are <80 mAOD, and >50 mg/l CaCO3, and thus comply with Type 3n under the

WFD.




To meet ‘Good Ecological Status’ for phosphate, the standard is 120 µg SRP/l (annual mean). This

would place the Rivers Great Ouse and Ouzel in the ‘Poor’ category under the WFD. The sources of

phosphorus to water are many and varied, but can be conveniently ascribed to agricultural (grass and

arable) and non-agricultural (large WwTW, trade discharges, smaller WwTW and domestic systems).

Much investment has been undertaken to improve discharges from major point sources such as

larger WwTWs (>10,000 PE), and there is increasing attention given to diffuse sources.

Diffuse source pressures arise from a wide variety of activities. They can arise from land use

activities, both rural and urban, that are dispersed across a catchment and may have an individually

minor, but collectively significant environmental impact. Examples of diffuse pollution include the

transport of nutrients and sediment from farmland or the run-off of water contaminated with pollutants

from vehicle emissions from hard surfaces in towns to groundwater and surface waters. Diffuse

pollution is often associated with heavy rainfall when pollutants are flushed into watercourses.

Thus the more detailed WCS should undertake a more complete review of water quality pressures.

Ideally, this would include areas upstream and downstream of Milton Keynes. Depending on the

results of this work, a modelling exercise should be conducted alongside this desk-study, with the

objective of estimating the relative loads of phosphorus to watercourses from diffuse and point

sources. This exercise would help to determine the relative loads from WwTWs, compared to other

sources, and thereby help guide investment decisions.

It should also be noted that under the WFD, more stringent standards might be required for protected

areas, in this case the Ouse Washes. Although the distance upstream has been considered to be a

mitigating factor for large concentrations of nutrients from up, and downstream of Milton Keynes, any

measures to reduce concentrations at the Ouse Washes are likely to require all upstream sources to

be reduced to the most practicable loadings/concentrations not exceeding excessive cost. It is

recommended that discussions continue with Natural England and EA in order to more fully

understand how new standards will be applied, especially in relation to the Ouse Washes, and

measures under RBMPs that might impact activities in and around Milton Keynes and its environs.

11.3 WFD and Water Company Planning

An important consideration in the WFD planning process is the timing with respect to the statutory

water company planning and funding process. At present, there is a discrepancy between the two

planning timelines. The WFD RBMPs are not due to be finalised until 2009 and hence the

Programme of Measures which sets out what changes will need to be implemented in order to

achieve ‘good’ status in all water bodies, will not be known until this point. Whilst it is not just water

companies which will be affected by the programme of measures, it is considered that water

companies such as AWS will have a key role to play in implementing the measures and helping to

achieve ‘good’ status in time for the 2015 deadline as required by the WFD.




However, the current PR09 and AMP5 timelines are such that the water companies will be submitting

their business plans, which set out the investment requirements for AMP5 (2010-2015), before the

RBMPs plans are finalised. It is therefore uncertain how much of the investment required to meet

with programme of measures can be planned for and funded in the next AMP period and that much

of the investment required to meet good status will not be forthcoming until AMP6 (2015-2020).

Despite this, studies such as the WCS have a role to play in identifying likely impacts of the WFD and

where future investment is most likely to be required in order to move key waterbodies towards good

status based on the interim risk characterisations. Use of the draft standards and draft risk

characterisations is essential such that early decisions can be taken on where investment is most

likely to be required in order to meet with the future programme of measures and attainment of ‘good’

status. In this respect, the Milton Keynes WCS can highlight and provide justification for further

investment for inclusion in AWS’s submission for PR09 such that measures can begin to be

implemented in AMP5 prior to the 2015 WFD target.




12 Development Area Assessment

Following the assessment of each of the water cycle and water environment topic areas in preceding

sections, the constraints and options for water cycle elements relating to the development are

covered in the assessment tables which give a visual comparison of each scenario based on a colour

coding system. In addition, a textual description of the colour assigned to each scenario is given in

the table relevant to each scenario.

The colour coding system used is explained in Table 12-1.

Table 12-1 : Assessment Table Colour Coding

Spare capacity, minimum investment required

Strategic scale mitigation or WSI will be required

Major investment required / major limitation




12.1 Central Area

12.1.1 Overview of Potential Growth

Rapid growth is planned within the Central Area, with the majority of this growth likely to occur on

an ad-hoc basis, as and when land becomes available. Although there are currently numerous

developments going forward which are at different phases within the planning process.

Discussions with MKC and MKP have revealed that a maximum of 14,350 homes are proposed for

this area.

12.1.2 Flood Risk and Drainage

There are no major fluvial flood risks within this area, although the River Ouzel runs along the

eastern boundary of the area, and Loughton Brook along the western boundary. Localise flash

flooding has been recorded in the SFRA and should be considered a potential issue, and

appropriate mitigation measures should be incorporated into any development. A site-specific

assessment of the risks should be undertaken and development located where possible in Flood

Zone 1. The SFRA should provide appropriate data for SUDS assessment.

12.1.3 Water Resources and Water Supply

AWS latest supply/demand balance indicates that this area currently has sufficient deployable

output to meet demand, not allowing for headroom, until 2019/20. Allowing for headroom, this

shows there is already a resource shortfall. This position will be eased in the short term (by 2010)

through to developments at Wing WTW (supplied by Rutland Water). Beyond 2010, it may be

necessary to supplement available resources by the development of local schemes with the

existing abstraction licence limits.

In the longer term, a major regional resource development may be required, such as the River

Trent Transfer Scheme. As part of this scheme, there will be the re-zoning of supplies from


The area is presently serviced by a number of potable water mains and as such servicing should

not be an issue. However AWS have identified that as the existing mains in these areas will not

have been designed for growth on such a large scale significant offsite mains reinforcements may

be required. AWS will need to be consulted depending on the total number of properties that can

be developed in this area. Consultation with AWS will verify capacities of existing potable water

infrastructure.

12.1.4 Wastewater Drainage and Treatment

Cotton Valley WwTW currently receives flows from this area currently has a DWF headroom

capable of accommodating approximately 55,560 new properties (based on AWS occupancy of

2.1) hence there are no short or medium term constraints in terms of wastewater treatment.

The ongoing works to Cotton Valley WwTW will improve network capacity in many areas

particularly in the centre and east of the city. Development in the Oakgrove area will require

pumping station and sewer upgrades. Calculations have shown that there are localised issues with

insufficient capacity within the Central Area, particularly in the north-east of the city.

12.1.5 Environment

There are a number of conservation areas and wildlife sites within the Central Area, Oxley Mead

SSSI and Howe Park SSSI (and their associated consultation buffers) are located approximately

2km from the limits of the this area. Further screening will be required to determine extent of

impact of development during the undertaking of the detailed WCS.

12.1.6 Water Quality

Cotton Valley WwTW currently contributes to high phosphate levels in the River Ouzel and River

Great Ouse, which in turn affect downstream areas in the Ouse Washes. Therefore any

development in this policy area could increase phosphate loads in the watercourses without

technological modifications to the WwTW. This should be addressed as part of the detailed (stage

2) WCS.

12.1.7 Summary

Table 12-2 : Key Development Constraints in Central Area

Wastewater

Possible Dwelling

Scenario Flood Risk Water Resources

We

ste

rn*

No

rth

Ea

st*

So

uth

Ea

st*

Environment and

Water Quality

Existing Baseline

0-3,500

3,500-7,000

7,000-10,500

10,500-14,000**

* Total growth figures have been split across the three sub-areas

** Notionally growth up to 14,350




Replace with Figure 12-1




12.2 Eastern Area


Development in the Eastern Area incorporates the Eastern Expansion Area and up to three

reserve sites as identified in the Local Plan.

Proposed growth within to the east of Milton Keynes would lead to an increase in dwellings of up

to 13,000, plus 53 hectares of non-residential development. Of the 13,000 proposed new

dwellings, 5,600 would fall within the administrative area of Mid Bedfordshire District Council.


There are no significant flood risk issues in the Eastern Area. The River Ouzel runs to the west of

the study area and Broughton Brook runs though the study area and there are areas of Flood

Zone 2 and Flood Zones 3a and 3b identified in the SFRA. Risk of groundwater flooding around

Woburn Sands site associated with sandy permeable geology. A site-specific assessment of the

risks should be undertaken and development located where possible in Flood Zone 1. The SFRA

should provide appropriate data for SUDS.


AWS latest supply/demand balance indicates that Eastern Area currently has sufficient deployable

output to meet demand, not allowing for headroom, until 2019/20. Allowing for headroom, this

shows there is already a resource shortfall. This position will be eased in the short term (by 2010)

through to developments at Wing WTW (supplied by Rutland Water). Beyond 2010, it may be

necessary to supplement available resources by the development of local schemes with the

existing abstraction licence limits.





not be an issue, however AWS have identified that significant reinforcements to the current water

supply system will be required to accommodate the planned growth. AWS have a number of

strategic upgrade planned as part of the AMP4 and AMP 5 programmes including an upgrade of

Woburn Pumping Station which require the upgrade of the Woburn Pumps, which pump directly

into supply as well as the Woburn to Brickhill Copse Pumps which transfer water to Brickhill Copse

WTW. Further consultation with AWS will verify capacities of existing and future potable water

infrastructure.


AWS have highlighted that there are significant issues relating to the capacity of the wastewater

network serving the area to the South East of Milton Keynes. The inlet works upgrade at Cotton

Valley WwTW will greatly improve the situation. A broad-scale assessment of the wastewater

network has highlighted significant issues in the area around Wavendon, with the system

appearing to be already at capacity. Pressure on the system would be intensified through the

development proposed in the Eastern Expansion Area. AWS has significant upgrades proposed

to serve development in this area with a new trunk main along Broughton Brook which will be

extended to the south.



2.1) hence there are no short or medium term constraints in terms of wastewater treatment.

12.2.5 Environment

There are a number of conservation areas and wildlife sites within the Eastern Area, however

there are no designated environmental protection areas within the proposed growth area, although

King’s and Baker’s Wood SSSI is approximately 5km south of the limits of the growth area.





technological modifications to the WwTW. This should be addressed as part of the detailed WCS.

12.2.7 Summary

Table 12-3: Key Development Constraints in Eastern Area

Wastewater

Possible Dwelling


So

uth

*

No

rth

* Environment

Existing Baseline

0-3,250

3,250-6,500

6,500-9,750

9,750-13,000

* Total growth figures have been split across the two sub-areas




12.3 Western Area


Discussions with MKC and MKP have revealed that up to 10,000 new dwellings are proposed

within the Western Area. There are also employment areas and community facilities proposed for

this area.


There are no significant fluvial flood risks within this area, although Loughton Brook runs along the

eastern edge of the area. The SFRA identifies areas of Flood Zone 2, and Flood Zones 3a and 3b

associated with Loughton Brook. A site-specific assessment of the risks should be undertaken

and development located where possible in Flood Zone 1. The SFRA should provide appropriate

data for SUDS.


AWS latest supply/demand balance indicates that Western Area currently has sufficient

deployable output to meet demand, not allowing for headroom, until 2019/20. Allowing for

headroom, this shows there is already a resource shortfall. This position will be eased in the short

term (by 2010) through to developments at Wing WTW (supplied by Rutland Water). Beyond

2010, it may be necessary to supplement available resources by the development of local

schemes with the existing abstraction licence limits.





not be an issue, as AWS have identified local offsite mains reinforcements to support the planned

growth. However AWS will need to be consulted depending on the total number of properties that

can be developed in this area. Consultation with AWS will verify capacities of existing potable

water infrastructure.


A study of the wastewater network in the study area has revealed there are some issues with the

capacity of the existing wastewater drainage network, particularly in the north of the area. AWS is

currently reviewing options for serving the Western Expansion Area (Redland development). New

pumping stations and sewers will be required to transfer flows to the point of connection into

existing main to Cotton Valley WwTW.



2.1) hence there are no short term constraints in terms of wastewater treatment.

12.3.5 Environment

There are a number of conservation areas and wildlife sites within the Western Area, Oxley Mead

SSSI and Howe Park SSSI (and their associated consultation buffers) fall within the limits of the

growth area.






12.3.7 Summary

Table 12-4 : Key Development Constraints in Western Area

Wastewater

Possible Dwelling


No

rth

*

Ce

ntr

al*

So

uth

* Environment

Existing Baseline

0-2,500

2,500-5,000

5,000-7,500

7,500-10,000

* Total growth figures have been split across the three sub-areas




12.4 Northern Area


Following discussions and input from both MKC and MKP, it is proposed that there will be a total of

up to 3,000 new homes in the Northern Area.


There are no significant fluvial flood risks within this area, although the River Great Ouse flows

within the area, and the confluence of the River Great Ouse and River Ouzel is situated in the

northeast of the area and has experienced flooding in the past. The SFRA identifies areas of

Flood Zone 2 and Flood Zones 3a and 3b along the River Ouse. There have been several

instances of sewer flooding in Wolverton. There is a low risk of groundwater flooding associated

with an area of more permeable geology to the north of Wolverton. A site-specific assessment of

the risks should be undertaken and development located where possible in Flood Zone 1. The

SFRA should provide appropriate data for SUDS.


AWS latest supply/demand balance indicates that the Northern Area currently has sufficient










not be an issue, however AWS have identified that significant reinforcements to the current water

supply system will be required to accommodate the planned growth. AWS have a number of

strategic upgrades planned as part of the AMP4 and AMP 5 programmes including Old Stratford

pump upgrades, reinforcement between Old Stratford Pumping Station and Kiln Farm, increasing

storage at Deanshanger water reservoir , and improving resilience of supplies through improving

the Salcey to Deanshanger main crossing under the railway. . Further consultation with AWS will

verify capacities of existing and future potable water infrastructure.


There are no major issues in the Northern Area. However, a study of the wastewater network has

revealed that there are small localised issue in the east of the area where wastewater capacity

may be insufficient to cope with the future proposed growth. The Northern Expansion Area

development framework also states that AWS have said, a pumping station will be needed as

there is insufficient fall from the site23

.

(NB From AWS stage 2 report there are no issues with serving Wolverton or Northern

Expansion Area)




12.4.5 Environment

There are a number of conservation areas and wildlife sites within the Northern Area, however

there are no designated environmental protection areas within the proposed growth area.






12.4.7 Summary

Table 12-5: Key Development Constraints in Northern Area

Wastewater

Possible Dwelling


Ea

st*

We

st*

Environment

Existing Baseline

0-650

650-1,300

1,300-1,950

1,950-3,000


23 Northern Expansion Area, Development Framework Plan – May 2004




12.5 South Western Area


Following discussions and input from both MKC and MKP, it is proposed that there will be up to

9,000 new homes in the South Western Area up to 2026 (with 5,390 in Aylesbury Vale).


There are no major fluvial flood risks within this area, although Water Eaton Brook flows through

the area and the SFRA identifies the associated areas of Flood Zone 2 and Flood Zone 3a and 3b,

including parts of Bletchley. There have been instances of sewer flooding recorded in Bletchley

which is situated within the South Western Area. A site-specific assessment of the risks should be

undertaken and development located where possible in Flood Zone 1. The SFRA should provide

appropriate data for SUDS.


AWS latest supply/demand balance indicates that the South Western Area currently has sufficient










not be a major constraint as AWS have identified local offsite mains reinforcements to support the

planned growth. However AWS will need to be consulted depending on the total number of

properties that can be developed in this area. Consultation with AWS will verify capacities of

existing potable water infrastructure.


Study of the wastewater network has revealed there are no major wastewater upgrades required

to serve the proposed growth in the South Western Area. Subject to confirmation on capacity,

AWS expect the development area to transfer to Cotton Valley via the Loughton Valley trunk

gravity sewer. The recently constructed pumping station and rising main to serve Newton Leys

would not be of sufficient capacity to serve development of the scale proposed.




12.5.5 Environment

There are a number of conservation areas and wildlife sites within the South Western Area, Oxley

Mead SSSI and Howe Park SSSI (and their associated consultation buffers) are located

approximately 1km and 2.5km respectively from the limits of the growth area, with King’s and

Baker’s Wood (and Heath’s) SSSI approximately 3.5km from the limits of the growth area.






12.5.7 Summary

Table 12-6 : Key Development Constraints in South Western Area

Possible Dwelling

Scenario Flood Risk Water Resources Wastewater Environment

Existing Baseline

0-2,250

2,250-4,500

4,500-6,750

6,750-9,000





12.6 Land East of the M1


Following discussions and input from both MKC and MKP, it is proposed that there will be up to

5,600 new homes in the expansion area east of the M1.


There are areas of fluvial flood risks within this area associated with Chicheley Brook and the

River Ouzel. However, this should not be a major constraint as the EA are unlikely to permit

development within flood risk areas.. A site-specific assessment of the risks should be undertaken

and development located where possible in Flood Zone 1. Consideration should be given to the

implementation of integrated SUDS measures to attenuate surface water runoff.


AWS latest supply/demand balance indicates that Milton Keynes currently has sufficient

deployable output to meet demand (not allowing for headroom), until 2019/20. Allowing for





.However, AWS have identified that for the Land East of M1, levels of off-site works will be more

than for other growth areas since existing mains in that area do not have the capacity to serve

such major development

AWS will need to be consulted depending on the total number of properties that can be developed

in this area. Consultation with AWS will verify capacities of existing potable water infrastructure.


Study of the wastewater network has revealed there are significant wastewater constraints to the

proposed growth in the area east of the M1. The preferred solution is likely to be a direct

connection to Cotton Valley WwTW. This would require crossing the M1 motorway. Connection to

the existing Newport Pagnell system would require significant upgrades. There are existing

flooding issues at Newport Pagnell which would be exacerbated from increased CSO spill

frequency.



2.1) hence; there are no short or medium term constraints in terms of wastewater treatment.

12.6.5 Environment

There are local wildlife sites within this expansion area including Wepener Wood and Moulsoe Old

Wood. It is not known at this stage whether these sites are hydrologically sensitive to potential

changes brought about by the proposed development. Similarly it is not known then exact nature

of impact the development will have or neighbouring and downstream designated sites.






12.6.7 Summary

Table 12-7: Key Development Constraints in Land East of M1

Possible Dwelling

Scenario Flood Risk Water Resources Wastewater Environment

Existing Baseline

0-1,500

1,500-3,000

3,000-4,500

4,500-6,000




12.7 Rural Areas


Minor growth of up to 3,000 dwellings is planned within the northern parts of the administrative

area of Milton Keynes.


There is an area of fluvial flood risks within Newport Pagnell, although there are flood risk

management schemes in operation to mitigate this risk. There are no other major flood risk areas

within the rural areas. The areas around Newport Pagnell, Olney and Hanslope are underlain by

Oolitic Limestone, which poses a groundwater flooding. A site-specific assessment of the risks

should be undertaken and development located where possible in Flood Zone 1. The SFRA

should provide appropriate data for SUDS.


AWS latest supply/demand balance indicates that the Rural Areas currently has sufficient










not be a major constraint. However AWS will need to be consulted depending on the total number

of properties that can be developed in this area. Consultation with AWS will verify capacities of

existing potable water infrastructure.


The wastewater network serving Olney is a pumped system. At this stage it has been assumed

that through increasing the pumping rates or pump durations, initial growth in Olney could be

handled by the existing system. It is however assumed that through increasing the pumping

phases that the capacity of the wastewater network would not be affected, this would however

need to be confirmed during the detailed (stage 2) WCS. Data provided by AWS shows that Olney

WwTW (which serves Olney and Emberton) (based on AWS occupancy of 2.1) has no flow

headroom capacity. Consultation should be undertaken with the EA as part of the detailed (stage

2) WCS to determine whether the consented limits could be increased.

Calculations have shown that there is insufficient capacity in 75% of the network currently serving

Hanslope, although this may be exacerbated by missing data. Only 15% of the network is shown

to have the capacity to facilitate the maximum growth figure for Hanslope (circa 1,500). Data

provided by AWS shows that Hanslope WwTW has an approximate consented flow capacity of

about 755 new dwellings. In the short term the WwTW would be able to cope with the proposed

development within Hanslope, however in the longer term (and dependant upon the number of

new properties within Hanslope) there may be issues relating to flow capacity at the WwTW. As

with Olney WwTW, consultation should be undertaken with both the EA and AWS to determine the

scope for increasing consented limits and capacities at Hanslope in order to facilitate the proposed

development.

12.7.5 Environment

There are a number of conservation areas and wildlife sites within, or near to Olney and Hanslope.

Salcey Forest SSSI, Mill Crook SSSI and Roade Cutting SSSI are within 5.5km of the limits of

Olney, with Yardley Chase (and associated extension buffer) within 3km of Hanslope. Hanslope is

also within 6km of the Salcey Forest SSSI.


At this stage it has not been determined in any great detail where the treated effluent from Olney

WwTW and Hanslope WwTW are discharged. However, there are issues relating to discharge to

both ground (via soakaways) or a watercourse. Discharges to ground should examine and

determine the exclusion of List 1 and List 2 substances, discharges to a watercourse is likely to

increase phosphate loadings. Discharge details should be confirmed as part of the detailed (stage

2) WCS, as well as addressing the prevailing issues.

Although individually small, discharges from rural WwTWs can cause significant local impacts.

The treatment processes are often rudimentary, and often these discharge to small watercourses

are not well monitored. Small watercourses can be more sensitive to water pollution and changes

in water quality than large rivers, and hence the impact from these small works should be

assessed at the earliest opportunity.




12.7.7 Summary

Table 12-8: Key Development Constraints in Rural Areas

Wastewater

Possible Dwelling


Oln

ey

Ha

ns

lop

e Environment

Existing Baseline

0-750

750-1,500

1,500-2,250

2,250-3,000





Replace with Figure 12-7 and Figure 12-8




13 Water Efficiency

The growth of homes in the Anglian region will place increasing strain on available resources. AWS

have already noted this and through existing schemes has already achieved efficiencies through

increased metering and reduction of water supply leakage24

. Meter penetration has reached 57% of

AWS’s customers25

and they have managed to reduce its levels of leakage to 19% of the water put

into supply (based on 2005/06)26

.

13.1 New Development – Water Efficiency

New developments can be built with water efficiency in mind. The CLG have recently consulted on a

water efficiency figure for all new builds of between 80 l/h/d and 120 l/h/d.

Approaches to water efficiency differ between the two groups of customers supplied by AWS. The

two groups are metered and un-metered customers.

• Metered customers will already be ‘water conscious’ and a typical AWS metered customer

uses around 136.9 l/h/d. It can be assumed that these customers will have taken easy steps to

improve their water efficiency for example, by mending dripping taps, installing water butts and

replacing old washing machines with new more water efficient models,

• Un-metered customers in the Anglian region typically use 155.8 l/h/d. Un-metered households

may not be able to afford to switch to a meter (under existing water tariffs) and their options for

reducing water usage may be less than for metered customers. Help in the form of a water

efficiency audit may be useful step for customers to understand where they might be using

most water. The next step may be to provide certain groups of un-metered customers, such

those receiving social security payments with small grants to enable households to convert to

more water efficient technologies such as showers and low flush toilets.

13.2 Code for Sustainable Homes

The Code for Sustainable homes sets out the maximum water usage permitted for each code level.

This provides a flexible outline for improving the overall sustainability of a house. Table 13-1 outlines

the water efficiency that needs to be achieved to reach each of the sustainable levels.

24 Anglian Water’s Water Efficiency plan 25 Anglian Water’s Drought Plan. AWS, 2006 26 OFWAT Security of Supply, Leakage and water efficiency 2006/07 report. 4 Water Resources in the South East Forum




Figure 13-1: Code for Sustainable Homes – Water consumption targets for the different code levels

and examples of how these targets can be attained in new build

Code for sustainable

homes levels.

Maximum amount of

water (litres per

person per day)

Examples of how to achieve water efficiency level.

1 120

2 120

Install efficient equipment within the home – 18l max

volume dishwasher and 60l max volume washing

machine. Install 4/6l dual flush toilets. Install 6-9l/min

showers. Educate users about how to be efficient

water users. Installation of water meters.

3 105

4 105

As above. Install flow regulators into bathrooms and

kitchens. To reduce flow rate of taps to 3 l/min and

showers to a maximum flow rate of 6 l/min. Specify

‘low volume’ baths with the levels of overflow pipes at

lower than normal levels to prevent over-filling.

5 80

6 80

As above, in addition: Grey water recycling for toilet

flushing. Provide water audits for people to show them

where they can reduce water usage.

The examples of water efficiency measures include in are an outline of the possible ways to improve

water efficiency. There are many more possibilities that are site specific. Many of these are shown

in the OFWAT water efficiency initiatives for water and sewerage companies and it is recommended

that these are assessed and considered for inclusion in new development as part of the Stage 2

strategy as the preferred options for development come forward. Other steps which should be

considered in new builds include: rainwater harvesting from roofs and paved areas (through the use

of permeable surfaces); grey water recycling (with some mains support) which can provide enough

water to run all toilets, a washing machine and outside taps.

New developments offer the opportunity to work towards a much higher level of water efficiency, the

eco-towns water cycle worksheet shows examples of where community schemes have been used as

a way to improve efficiency for example, through the collection and supply of rainwater for use in

toilets; these kind of initiatives could be considered for Milton Keynes on a strategic scale to further

reduce water demand. The Milton Keynes Framework Agreement for developments in the Eastern

and Western Expansion Areas, the Strategic Reserve Areas, Kingsmead South and Tattenhoe Park

require 90% of residential development to meet the Eco-Homes ‘Very Good’ standard, and 10% to

meet ‘Excellent’. All employment development in these areas should meet the BREEAM ‘Very Good’

standard at least. There is an opportunity to drive these standards up even higher (to Code for

Sustainable Homes standards) when it comes to developing standards for new developments in the

future.




13.3 Current Development – Reducing Existing Baseline

As well as efficiency in new build, consideration should also be given to the options to reduce existing

water consumption baseline from existing connections, over and above the measures being

implemented by AWS. It is recommended that a detailed water efficiency plan is developed for

existing customers in the Stage 2 WCS as an overall plan to reduce the baseline water demand in

Milton Keynes. This outline study has initially identified several ways in which current demand can be

reduced in Milton Keynes.

Existing homes can achieve significant savings through the retrofitting of efficient devices for

example; the installation of 6 litre flush toilets can give a saving of 8%27

and potentially even more

savings with 4.5 litre flush toilets. It should be noted that all new homes being built today are fitted

with 6 litre flush toilets as a matter of course today.

There are possibilities within existing development to improve efficiency and reduce the baseline

water consumption. Measures that can be employed are:

• Education about water efficiency, in particular about water efficient fixtures and fittings and

appliances,

• Advertisement of products and services that can help people to be more water efficient;

promote local plumbers who preferable install water efficient fixtures and fittings (for example,

provide grants to cover any additional cost for a 4.5 litre toilet rather than a 6 litre toilet),

• Promotion of the Waterwise Marque, which is given to products that show excellent water

efficiency. More information can be found at www.waterwise.org.uk,

• Provision of support for the purchase and installation of water efficient fixtures fittings and

appliances such as low flush toilets, efficient dishwashers and washing machines, aerating

taps (aerators can be retrofitted on to existing taps), water butts,

• Provide information on lagging pipes to prevent bursts in the winter,

• Provide water audits to show consumers where they use the most water and how they can

reduce their water usage,

• Encourage local businesses to promote water efficiency,

• Installing aerators on taps and showers to reduce the amount of water wastage,

• Fit flow restrictors on showers, which reduces flow to a maximum of 8 litres per minute.




14 Policy, Developer Guidance and Funding

14.1 Introduction

An important outcome of a completed WCS is to ensure a link between the planning process and the

infrastructure required to meet growth requirements. The Stage 2 WCS will define in more detail the

infrastructure requirements for the proposed development areas, but a further key outcome will be

the timing of implementation of that infrastructure and how it is funded.

The Stage 2 Milton Keynes WCS will ultimately produce a programme or timeline for development

with detail of the infrastructure required in order to facilitate this development. The timeline will also

demonstrate when funding would need to be sought by AWS as well as the implementation of

mechanisms for ensuring sufficient developer contribution towards strategic infrastructure required to

meet the requirements of the overall WCS.

It is intended that the completed Milton Keynes WCS will produce an overall strategy that each of the

key stakeholders can sign up to. This will aid in the process of delivering development in Milton

Keynes and local environs by helping to ensure that objections to proposed development on the

grounds of water issues such as flood risk and abstraction are avoided. By producing a completed

WCS that is agreed by MKC, AWS, MKPT, IDB and the EA it will aid developers in understanding the

requirements they need to meet in order to comply with the strategy produced from the WCS. It will

also set the framework for how funding will be sought for the different water infrastructure

requirements.

In order to achieve this, the Milton Keynes WCS is required to produce the following:

• Guidance on planning policy with respect to development and the water cycle that MKC can

use to input into the LDF, and guidance on incorporating the WCS findings into the

Development and Flood Risk SPD,

• Guidance for developers in terms of what developers need to achieve in order to comply with

the overall WCS. This will be in the form of a developer checklist and it is envisaged that this

will eventually be a document, which if its criterion are all met for a proposed development, will

help to ensure no objection from the EA or LPA on the grounds of water cycle issues. This

type of checklist document has been successfully developed for other WCS such as the

inaugural WCS completed for Corby. Consideration should also be given to the checklist

drawn up in the SFRA,

• Agreement on funding mechanisms, particularly for strategic, development wide infrastructure

required i.e. strategic scale and integrated surface water attenuation schemes, maintenance

and responsibility,




• Planning timelines for provision of water infrastructure against growth to aid AWS in planning

for water infrastructure within relevant business plans,

• To provide justification for AWS in seeking funding through the PR and AMP process for the

required infrastructure,

• Highlight the need for a strategic approach to surface water management e.g. development of

Surface Water Management plans across whole areas rather than individual developments.

14.2 Developer Checklist

The overall intention is that all Developers would be asked to use the water cycle developer checklist

as part of the planning application process and to submit a completed version with their planning

applications. The EA is a statutory consultee with regards to flood risk and the water environment

and as such, will need to sign up to the checklist as will MKC. The IDB is the Statutory Operating

Authority within its District and is a planning consultee under PPS25. The checklist provided in this

Stage 1 WCS (See Appendix F) has been developed from examples used in previous WCS as well

as the EA’s national standard checklist available on their website. It is included in the Outline Study

as a starting point to further develop in the detailed study, once it is known which development

scenarios are to be taken forward.

14.3 Funding and Cost Apportionment Mechanisms

In terms of the overall funding mechanism, it is important to consider that the Government has laid

down strict rules on how water companies are funded, especially with regard to domestic

development, and the industry’s economic regulator – OFWAT, heavily regulates this overall process.

Essentially, AWS has the responsibility for providing wastewater treatment and water supply costs

and this is funded through charges to customers within its operating area through the Price Review

Process and Asset Management Plan (AMP) process. Therefore, developer contributions relate

largely to strategic scale flood management infrastructure (including surface water attenuation).

This Stage 1 WCS report introduces the various policy, funding and developer requirement elements

to the Milton Keynes WCS, but it is envisaged that these will be developed further in the detailed

Stage 2 WCS.

The Stage 1 WCS has highlighted that there is a need for expenditure on new infrastructure in the

following areas:

• Water supply and water resources,

• Wastewater treatment and sewerage,




• Large scale surface water management schemes,

• Smaller, site specific surface water management.

Although the options for providing the additional infrastructure will be developed in further detail in the

Stage 2 WCS, it is important to consider funding at a strategic level now to inform the development of

the Stage 2 WCS.

Both water supply and water resources are the responsibility of AWS within Milton Keynes and as a

result, the proportion of which can be charged to developers is set down by agreements with

OFWAT. In general, WCS have not considered the apportionment of developer contributions

towards strategic water supply and wastewater facilities.

In summary, developers can be included into the financial contribution in two ways:

Stage 1 & 2 - Stakeholder Participation

In developing other WCS’s, property developers have been incorporated into the stakeholder group

to provide an input into the direction of the study. It is important to ensure that all developers involved

are represented so as to avoid giving any unfair advantage to any one group of developers. In so

doing, the developers who are involved would be best placed to undertake the recommendations

from Stage 2 of the WCS and ensure that these are incorporated into the design of the

developments.

Stage 3 – Infrastructure Funding

Developers may also contribute to the capital works of infrastructure required within the WCS.

Although in general this would not apply to wastewater or water supply infrastructure as this is

regulated by the Water Companies through OFWAT. It would however include contributions for

funding large scale flood risk mitigation measures, with particular emphasis on large scale surface

water attenuation storage scheme for development in and around Milton Keynes.

14.3.1 Minimisation of Cost

Despite this, developers can at least contribute to minimising the capital cost of water infrastructure.

It can be seen from the assessment of whether existing infrastructure is adequate that a key variable

is water consumption per capita. To a large extent developers can be encouraged to reduce this

through initiatives such as grey water recycling, having developments with less impermeable

surfaces, specifying higher quality materials for pipework etc.

By way of example:

• If the percentage return to sewer can be reduced from 90% to 75%, the number of additional

properties that can be accommodated per 1 m3d

-1 headroom at an existing WwTW is 0.8.




• If reducing the infiltration of groundwater into drains supports the reduction in percentage

return to drain by using higher quality drain pipes, the number of additional properties that can

be supported per 1 m3d

-1 headroom at the same WwTW can be further increased.

14.3.2 Water Resource Provision – Employment

From December 2005, non-household customers who are likely to be supplied with at least 50 mega

litres of water per year at their premises are now able to benefit from a new Water Supply Licensing

mechanism. If eligible, they may be able to choose their water supplier from a range of new

companies entering the market. The Water Supply Licensing mechanism enables new companies to

supply water once OFWAT has granted them a licence. These companies can compete in two ways:

• By developing their own water source and using the supply systems of appointed water

companies (such as AWS) to supply water to customers' premises. This would be carried out

under the combined water supply licence,

• By buying water 'wholesale' from appointed water companies (such as AWS) and selling it on

to customers. This would be done under a retail water supply licence.

These are potential options for the sources of employment to be provided in Milton Keynes.

14.3.3 Cost Apportionment Mechanism

The Stage 1 WCS has considered that surface water attenuation will be required in order for new

development to comply with PPS25, developers could contribute towards the cost for provision of this

on a strategic level. In addition, there are potential options for developer contribution towards

strategic sewerage infrastructure provision. Dependent on the options taken forward in the detailed

study, a potential charge could be made to developers through the Section 106 mechanism with MKC

setting up a fund to receive Developers' contributions and to use them to fund works.

Research for the Corby WCS has identified that there is a legal requirement for such contributions to

be made on the basis of commensurate impact of each development, for instance according to its

location in the catchment. This mechanism has already been applied in Corby, whereby

contributions have been agreed via Section 106 agreements for two key developments; this is an

important precedent.

14.3.4 Milton Keynes Tariff System

In Milton Keynes there is a tariff system for new developments in the Eastern and Western Expansion

Areas, the Strategic Reserve Sites, Kingsmead and Tattenhoe Park. Tariff payments contribute to the

costs of both strategic and local infrastructure. The Tariff system was developed as an approach to

manage Section 106 contributions in these areas. Forward funding can be provided by English




Partnerships, with repayments being made through subsequent Tariff payments (which are linked to

housing completions).

The basis of the system is that each developer pays £18,500 per residential development and

£260,000 per hectare of employment land. Milton Keynes Partnership and English Partnerships act

as the LPA and banker for the system. The funds are a means of ensuring forward funding is

available for key infrastructure including roads, parks, and community facilities such as health centres

and schools. Tariff contributions will not cover 100% of the cost of all infrastructure related to growth

and other funding sources are still required to make up any shortfall on the provision of local and

strategic facilities.

However key benefits of the system are:

• Certainty of a level funding,

• Certainty of developer costs,

• Facilitates MKPs Business Planning,

• Addresses Strategic as well as local infrastructure requirements

• Forward Funding,

• Quality Control.

Outside of the ‘Tariff’ areas MKC continue to negotiate s106 agreements on a site by site basis, using

as a starting point the suite of supplementary documents the council has adopted, which set out the

basis for developer contributions expected for a range of infrastructure. This current suite of

documents includes guidance for developers on Development and Flood Risk. This is based on

PPG25, which has now been superseded.

The provision of strategic flood risk infrastructure related to the longer-term growth of Milton Keynes

could be incorporated into a future Tariff arrangement on development sites, which would manage

any s106 developer contributions. This would need to address all sites across the City, and not just

those forming an extension of the city. Any such arrangement would need to be explored with the

three Local Planning Authorities as a joint arrangement, as Mid Bedfordshire and Aylesbury Vale do

not currently operate a Tariff system, and will have to consider the strategic requirements of other

developments in their respective administrative areas.




15 Conclusions and Recommendations

15.1 Overview

The Stage 1 Milton Keynes Outline WCS has identified the existing capacity of the current water

environment and WSI and has used this assessment to determine where additional investment is

required to supply new infrastructure or protect the water environment. The conclusions of each

assessment are presented here.

15.2 Flood Risk and Drainage

Whilst there is a history of flooding within Milton Keynes and adjacent areas, the EA have confirmed

that they would not wish to see new development within the floodplain, and also would not wish to

see the construction of new flood risk management infrastructure to purely facilitate new development

in areas prone to flooding.

As with any new development there will be an increase in surface water run off, especially where

development takes place on Greenfield sites. As MKC has a target of 20% brownfield

redevelopment, the majority of development within Milton Keynes will indeed be on Greenfield sites.

Any surface water generated as a result of development will be required to be attenuated to

Greenfield run off rates, before being allowed to discharge into either watercourses or the AWS

surface water system.

Whilst some of the larger expansion areas already have plans in place for the construction of

attenuation facilities (i.e. large strategic balancing ponds), other developments would also by required

to provide or utilise attenuation facilities. The IDB has expressed concerns associated with the

impacts of present design standards and development densities of current growth when compared to

the existing surface water and flood risk management assets, which were engineered to different

(lower) design/growth standards that were current in the past when the assets were implemented. As

whilst there may be calculated capacity in the facilities, taking into account the impacts of climate

change and potential changes in flow estimation (since the design of the facilities), the capacity may

be less than perceived. The IDB and EA believe that through ‘joined up’ thinking, developers could

provide a series of facilities in conjunction with developers of adjacent sites in order to avoid a

number of smaller disparate facilities. This would also be the more sustainable option for providing

large scale strategic attenuation. The EA also expressed concern that the promotion of smaller

localised SUDS techniques are not totally over looked whilst aiming to provide the large scale

strategic attenuation, and that the property based SUDS could provide betterment over and above

the base standard provided by the strategic SUDS.




The introduction of small channels and swales to convey surface water to the large scale strategic

attenuation facilities would also be a means to extend and/or provide new green corridors into the

development areas. Sufficient access for maintenance and maintenance regimes would need to be

agreed in advance to determine the size and who would manage the up keep of any new attenuation

features (i.e. channels and swales).

Increased development within Milton Keynes will lead to an increase in water demand, which will in

turn lead to an increase in the generation of wastewater and ultimately lead to an increase in effluent

discharges. Whilst AWS have headroom at Cotton Valley WwTW in terms of the consented volumes

of discharge to the River Ouzel, the EA have confirmed that they would not wish to see any increase

in discharges to the River Ouzel. It is understood that heavy engineering has been undertaken on

the River Ouzel and whilst it is believed that the River Ouzel has capacity to accept additional flows,

there are major concerns over increasing flood risk at Newport Pagnell, at the confluence of the River

Ouzel and River Great Ouse. Following discussions of the possibility of offsetting increases in

effluent discharges with an equal decrease in surface water discharge (from Willen Lake), the

following statement has been agreed between the EA and AWS and will provide guidance on this

issue.

Increased effluent discharges to the River Ouzel and River Great Ouse will impact on flood risk and

water quality. Before approving increases in consented discharges to these rivers, the EA will require

further catchment modelling to identify any necessary mitigation works particularly with reference to

the lakes in Milton Keynes. This should either be included in the detailed stage of the water cycle

study, the Level 2 SFRA or as an independent study for example a surface water management plan.

As there is no surface water (open channel and sewer) network model, it may be prudent to develop

a model either as part of Stage 2 of the WCS, or as part of any future Surface Water Management

Plan (SWMP), which MKC may be required to undertake.

15.3 Water Environment

The discussion in Section 6.5.1 described Water standards, discharge requirements, and other

sources of substances such as phosphorus, while Section 11 described existing water quality in the

Milton Keynes area, before outlining some possible effects of applying some new standards under

the Water Framework Directive. Possible impacts of nearby and downstream designated sites were

also highlighted.

This initial assessment has not been able to assess the ‘water quality’ capacity of the watercourses in

and around Milton Keynes since process capacity at key WwTWs are currently being reviewed by

AWS.




The Statutory standards for ammonia and DO should be fully considered as part of this review.

However, the consistently high nutrient grades for N and P in the Rivers Great Ouse and Ouzel. Both

are designated Eutrophic Sensitive Areas under the Urban Wastewater Treatment Directive

(91/271/EEC). Where wastewater (treated WwTW Final Effluent) is released into these areas, it must

undergo a secondary treatment which causes less impact on the environment.

However, there are also several smaller WwTWs in the Milton Keynes area, up and downstream.

Discharges from small WwTWs can impact smaller watercourses (or groundwater in the case of

soakaways). The possible impact of these discharges (and any possible increases in discharge) on

receiving surface, and/or groundwater should not be overlooked.

Diffuse source pressures also represent a significant threat to water quality. Diffuse sources arise

from a wide variety of activities. They can arise from land use activities, both rural and urban, that are

dispersed across a catchment and may have an individually minor, but collectively significant

environmental impact. Examples of diffuse pollution include the transport of nutrients and sediment

from farmland or the run-off of water contaminated with pollutants from vehicle emissions from hard

surfaces in towns to groundwater and surface waters. Diffuse pollution is often associated with heavy

rainfall when pollutants are flushed into watercourses.

Thus the more detailed WCS should undertake a more complete review of water quality pressures.

Ideally, this would include areas upstream and downstream of Milton Keynes. Depending on the

results of this work, a modelling exercise should be conducted alongside this desk-study, with the

objective of estimating the relative loads of phosphorus to watercourses from diffuse and point

sources. This exercise would help to determine the relative loads from WwTWs, compared to other

sources, and thereby help guide investment decisions.

It should also be noted that under the WFD, more stringent standards might be required for protected

areas, in this case the Ouse Washes. Although the distance upstream has been considered to be a

mitigating factor for large concentrations of nutrients from up, and downstream of Milton Keynes, any

measures to reduce concentrations at the Ouse Washes are likely to require all upstream sources to

be reduced to the most practicable loadings/concentrations not exceeding excessive cost. It is

recommended that discussions continue with Natural England and EA in order to more fully

understand how new standards will be applied, especially in relation to the Ouse Washes, and

measures under RBMPs that might impact activities in and around Milton Keynes and its environs.

The screening exercise undertaken as part of Section 10 showed that any adverse effects of the

Milton Keynes growth areas on a number of sites could not be screened out. These would therefore

need more consideration during the detailed (stage 2) WCS:

• Portholme SAC (water quality),

• Ouse Washes SAC/SPA/Ramsar site/SSSI (water quality),




• The Wash SAC/SPA/Ramsar site/SSSI (water quality),

• Felmersham Gravel Pits SSSI (water abstraction and water quality),

• Stevington Marsh SSSI (water abstraction and water quality),

• Howe Park Wood SSSI (water abstraction),

• Oxley Mead SSSI (water abstraction),

• Blue Lagoon LNR (water abstraction).

However, it may well be that after more detailed consideration at the next stage, impacts on many of

these sites can be ruled out.

15.4 Wastewater Treatment and Transmission

The high levels assessments have identified that there are a number of capacity issues within the

wastewater network serving Milton Keynes. Through increasing levels of development, any existing

issues relating to capacity would be exacerbated. This could however be managed either through

providing upgrades to the existing network at known problem areas (i.e. increasing the size of

pipework) or in certain development areas concentrating development around parts of the network

where there are less capacity issues.

This is particularly true in the Central Area and the Northern, Western and Eastern development

Areas. From the broadscale wastewater network capacity calculations, parts of the systems

undertaken as part of this study, these areas have been shown to potentially have capacity issues,

whilst parts of the system serving of areas within the same development areas have capacity issues

of a lesser. This should be confirmed by network modelling as part of the scope of works for the

detailed WCS.




Table 15-1: Wastewater Network – Constraints Summary

Area Sub Area Constraint

North East Major

South East Significant Central

West Significant

South Major Eastern

North Minor

North Major

Central Significant Western

South Minor

East Significant Northern

West Minor

South Western Minor

Land East of M1 Major

Olney Major Rural

Hanslope Major

In the short term, phasing of development could be concentrated on areas with the least initial

constraints (i.e. northern part of Eastern Area, southern part of Western Area, western part of

Northern Area and South Western Area). Infrastructure upgrades would then allow development in

other areas, where greater constraints have been highlighted. Confirmation of site-specific

constraints should be determined through network model during the Detailed WCS. Consideration

must also be given to the cumulative effect of development in shared networks (i.e. the impact of

development in the west of the Central Area, Western Area and Northern Area, upon the lower part of

the system).

Discussions will also be required to determine whether there is scope to increase discharges at

Olney WwTW and Hanslope WwTW, both of which are either at or close to their consented limits.

Cotton Valley WwTW will also need consent increase within LDF period (unless major reduction in

water consumption).

15.5 Water Resources and Water Supply

Milton Keynes is presently supplied by Wing and Grafham WTWs, which are in turn fed from Rutland

Water and Grafham Water respectively.

The forecast growth in demand for 57,950 new homes (by 2026) is estimated at 17 Ml/d for

residential demand and a further 9 Ml/d for non-residential development. The latter demand is likely

to be from commercial and service based industry. The combined total is approximately 26 Ml/d on

average but could be as high as 29 Ml/d on average. These figures exclude a 30% allowance for




headroom which is considered sensible to plan for. In addition, the above estimates do not take into

account of the Marston Vale Eco-Town, which could draw upon an extra 6 Ml/d.

AWS latest supply/demand balance indicates that the Milton Keynes and Newport Pagnell area

currently only have sufficient DO to meet demand, not allowing for headroom, until 2019/20. Allowing

for headroom, this shows there is already a resource shortfall. This position will be eased in the short

term (by 2010) through developments at Wing WTW (supplied by Rutland Water). Beyond 2010, it

may be necessary to supplement available resources by the development of local schemes, such as

at Foxcote WTW, within the existing abstraction licence limits. In addition, phased developments at

Clapham WTW will release DO from Grafham Water to supply Milton Keynes, although this may

require an increase in the abstraction licence at Clapham (on the River Bedford Great Ouse).

In the longer term, a major regional resource development may be required, such as the River Trent

Transfer Scheme. As part of this scheme, there will be the re-zoning of supplies from adjacent

planning zones. The mitigation measures being put in place at the Rutland Water SPA, such as the

creation of wetland habitats, should enable full take-up of this licence quantity without any negative

effects on the site.

There are however a number of other uncertainties (i.e. climate change, the review of consents and

Water Framework Directive), which remain and may affect the water resources situation in the future

and the status of available growth within the Milton Keynes area. The WCS is an iterative process

and will be updated periodically

15.6 Milton Keynes Tariff System

In order to assist with the provision of required water services infrastructure to help maintain the

proposed growth within Milton Keynes, we would recommend that the existing tariff system is

continued and developed. However this should be further investigated across the three Local

Planning authorities, as the Tariff currently only operates in the MKC administrative area.




16 References

Anglian Water – Drought Plan, 2006

Anglian Water – Water Efficiency Plan, 2004

Anglian Water – 2005 Water Resources Management Plan, 2004

Anglian Water – 2009 [Draft] Water Resources Management Plan, 2008

Anglian Water – 2009 Water Resources Management Plan, 2008

Anglian Water website – www.anglianwater.co.uk

Communities and Local Government – Code for Sustainable Homes - Step-change in sustainable home building practice, 2006

Communities and Local Government – Code for Sustainable Homes – Technical Guide, 2007

Communities and Local Government – [Draft] South East Plan, 2006

Communities and Local Government – Planning Policy Statement 25: Development and Flood Risk, 2006

Communities and Local government, Department for Environment, Food and Rural Affairs – Water Efficiency in New Buildings, 2007 http://www.communities.gov.uk/documents/planningandbuilding/pdf/WaterEfficiencyNewBuildings

Communities and Local Government, Environment Agency, Town and Country Planning Association – Sustainable Water Management: Eco-towns Water Cycle worksheet, 2008

CIRIA – Dry Weather Flow in Sewers, 1998

David Locke Associates – Brooklands Development Brief, 2006

David Locke Associates – Broughton Gate Development Brief, 2005

Department for Environment, Food and Rural Affairs – Securing water for the future, press release, 2008 http://www.tcpa.org.uk/press_files/pressreleases_2008/20080325_ET_WS_Water.pdf

Department for Environment Food and Rural Affairs website – http://www.defra.gov.uk/default.htm

Environment Agency – Guideline phosphorus standards for SAC rivers. Water Quality Task Group for the Habitats Directive. WQTAG048b, 2002

Environment Agency – River Great Ouse Catchment Flood Management Plan – Consultation Draft Plan, 2007

Environment Agency – SUDS, A Practical Guide, 2006

Environment Agency – The Upper Ouse and Bedford Ouse CAMS, 2005

Environment Agency – Towards Water Neutrality in the Thames Gateway, Summary Report, 2007

Environment Agency website – http://www.environment-agency.gov.uk/

Environment Agency, Department for Environment, Food and Rural Affairs – Preliminary rainfall runoff management for developments, R&D Technical Report W5-074/A/TR/1 Revision D, 2007

Environment Agency, Natural England and Partners – Planning Sustainable Communities: A Green Infrastructure Guide for Milton Keynes and the South Midlands, 2005

Gazeley UK – Nova Devlopment Brief, 2005

Government Offices for the South East – Milton Keynes and South Midlands Sub-Regional Strategy, East Midland East of England, 2005




Guthrie, Duncan and Owen – The development of soluble reactive phosphorus regulatory values in UK rivers. Paper prepared for UKTAG Rivers Task Team, 2006

Halcrow – Drainage Strategy for Milton Keynes, 2004

Halcrow – Eastern Expansion Area Development Framework, 2005

Halcrow – Milton Keynes Level 1 Strategic Flood Risk Assessment, 2008

Halcrow – Water Cycle Strategy Draft Guidance, Version 1 Revision 2, 2008

Institute of Hydrology – Flood Estimation Handbook (FEH) – Vols 1 -5, 1999

Joint Nature Conservation Committee website – http://www.jncc.gov.uk/page-0

Milton Keynes Council – Northern Expansion Area Development Framework SPG, 2004

Milton Keynes Council, Milton Keynes Partnership – Western Expansion Area Development Framework, 2005

Milton Keynes Partnership – The New Plan for Milton Keynes: A Strategy for Growth to 2031, 2006

Multi-Agency Geographic Information for the Countryside website – http://www.magic.gov.uk/#

The Office of Water Services – Security of Supply, Leakage and Water Efficiency (2006/07), 2008

The Office of Water Services – Water Efficiency Initiatives – Good Practice Register Water Sewerage Companies, 2006 http://www.ofwat.gov.uk/aptrix/ofwat/publish.nsf/AttachmentsByTitle/goodpracticeregister_2007.pdf/$FILE/goodpracticeregister_2007.pdf

United Kingdom Technical Advisory Group – UK Environmental Standards and Conditions (Phase I) Update report. UK Technical Advisory Group on the Water Framework Directive, 2007

Woods Hardwick – Broughton Park Development Brief, 2006

WRc plc – Sewers for Adoption, 2006

WSP – Land South of A421 Flood Risk Assessment, 2007

WSP – Stoke Goldington Flooding Investigation, 2007




Appendix A – Data Requests




Appendix B – Wastewater Network Capacity

Calculations




Appendix C – DWF Calculations




Appendix D – Hydrological Analysis




Appendix E – SUDS Options Details

Milton Keynes has been developed around the concept of strategic and integrate surface water and flood

risk management, with large flood storage reservoirs and engineered watercourse. The Drainage SPG

states growth must provide strategic and integrated drainage systems. Therefore Strategic and Integrated

drainage and SUDS is essential to continue the success of Milton Keynes.

Soakaways

Soakaways are traditionally built as square or circular pits, either filled with rubble or pre-cast perforated

concrete pipes surrounded by suitable granular backfill (although their design and depth may vary

depending on area draining into them). Their use is generally subject to full infiltration testing.

There are a number of factors that should be considered prior to their inclusion in drainage design, such

as:

• Relevant guidelines (such as BRE Digest 365) require that any soakaways should be constructed at

least 5m from any building foundations. Dependent on the layout of sites in relation to their

topography, this building restriction could limit the use of soakaways on some terraces or blocks of

dwellings,

• In areas of steep topography of the site, soakaways should be aligned perpendicular to the slope

direction, i.e. they should be ‘contoured’,

• In areas of steep gradient, allowing water to freely infiltrate into surrounding ground may cause

ground slumping, soil creep or similar effects.

Swales

Swales are shallow ditches designed to conduit and retain water, as well as facilitate infiltration where

possible. Where ground conditions are suitable, infiltration will occur either naturally or via a filter drain

located beneath the swale base. This can be filled with granular material and, if necessary, a perforated or

half perforated pipe. Swales typically are grass covered but can also contain larger vegetation types (often

scrub or reeds). This vegetation can aid water attenuation through encouraged evapotranspiration, uptake

or infiltration. It can also reduce water velocities and filter particulate matter, such as hydrocarbons and

particulate matter. Given these properties, they are typically located adjacent to roads or parking areas.

Their efficiency of infiltrating water into underlying ground is dependant on full infiltration testing.




Swales are likely to be suitable for receiving surface water runoff generated from roads and communal

parking areas. They could also be used to collate water from roofs in areas where soakaways are not

available.

Permeable Surfacing

Permeable surfacing involves the use of permeable material in the place of impermeable surfacing. This is

typically used for roads or parking areas. Where ground conditions are suitable, permeable paving allows

infiltration into the surrounding ground, using a permeable sub base. Where conditions are not suitable,

permeable paving can act as medium into a sub-surface attenuation tank beneath the paving from which it

is discharged through to the sewer system at an agreed restricted rate, using a hydrobrake or similar.

There are a number of mediums that can be used in the attenuation facility including:

• Tanked systems whereby reinforced tanks situated beneath the permeable surfacing are located.

Their design should considered significant loadings from vehicular traffic,

• Granular fill typically has a void ratio of 0.3 (30%) and is readily available as graded gravel fill,

• Crate systems have a higher void ratio (up to 90% in some cases) but are often costly and may

require complex maintenance.

Depending on potential adoption issues, permeable paving has the potential to be used for all access

roads and parking areas. The choice of system is dependant on the permeability of the underlying ground

and therefore upon full infiltration testing of the underlying ground.

Detention Basins or Retention Ponds

Detention basins are depressions (often vegetated for landscape purposes) that are normally dry but allow

storage of storm water to attenuate surface flows. Should ground conditions be suitable, infiltration will

occur naturally. Retention ponds are similar to detention basins but retain a permanent level of water. If

situated in permeable soil conditions, the base of the pond may require lining. Discharge from retention or

detention ponds into the receiving watercourse can be through a pipe or overflow system.

These features may have wider benefits beyond flood risk by reducing the amount of pollutants or

suspended material present in any potential outflows. In addition, they can add to the amenity and

biodiversity value of a development (this is particularly relevant for retention ponds).

Other Methods

Other typical SUDS methods include techniques such as greenroofs, water harvesting, wetlands, filter

drains and filter strips. They are potentially viable options for the proposed site and can have wider




sustainability benefits. However they do not generally constitute a significant volumetric input into

attenuation.




Appendix F – Developer Checklist

Key Water Cycle strategy Recommended Policy

Environment Agency and Natural England policy and recommendations

Local Policy

National Policy or Legislation

No. Flood Risk Assessment requirement checklist Answer Policy

/Legislation

1 Is the Development within Flood Zones 2 or 3 as defined by the flood zone mapping in the Milton Keynes SFRA?

Y - go to 5 N - go to 2

2 Development is within Flood Zone 1: • Site larger than 1 Ha? • Site smaller than 1 Ha?

go to 5 go to 3

3 Is the development residential with 10 or more dwellings or is the site between 0.5Ha and 1Ha?


4 Is the development non-residential where new floorspace is 1,000m

2 or the site is 1 Ha or more?


5 The development constitutes major development or lies within Flood Zone 2 or 3 and requires a Flood Risk Assessment (in accordance with PPS25 and the Milton Keynes SFRA) and the Environment Agency are required to be consulted.

Go to 8

6 The development constitutes major development and is likely to require a Flood Risk Assessment (in accordance with PPS25 and the Milton Keynes SFRA) but the Environment Agency may not be required to be consulted.

Go to 8

7 An FRA is unlikely to be required for this development, although a check should be made against the Milton Keynes SFRA and with Milton Keynes Council to ensure that there is no requirement for a FRA on the grounds of critical drainage issues. Does the SFRA or do Milton Keynes Council consider than an FRA is required?

Y – go to 8 N – go to 9

8 Has an FRA been produced in accordance with PPS25 and the Milton Keynes SFRA?

Y/N or N/A

PP

S2

5




No. Surface water runoff Answer Policy

/Legislation

9 A) What was the previous use of the site? B) What was the extent of impermeable areas both before and after development?

% before % after

EA Requirement for FRA.

10 If development is on a Greenfield site, have you provided evidence including calculations that post development run-off will not be increased above the Greenfield runoff rates and volumes using SUDS attenuation features where feasible (see also 18 onwards). If development is on a brownfield site, have you provided evidence including calculations that the post development run-off rate has not been increased, and as far as practical, will be decreased below existing site runoff rates using SUDS attenuation features where feasible (see also 17 onwards). Where a previous connection was made to a combined sewer, AWS are encouraging developers to dispose of surface water by an alternative means. Developers no longer have the right to connect.

Y/N or N/A

Y/N or N/A

PPS25

11 Is the discharged water only surface water (e.g. not foul or from highways)? If no, has a discharge consent been applied for?

Y/N

Y/N

Water Resources Act 1991

12 A) Does your site increase run-off to other sites? B) Which method to calculate run-off have you used?

Y/N

PPS 25 Preliminary Rainfall

Runoff Management for

Developments and the Interim Code of Practice for SUDS

13 Have you confirmed that any surface water storage measures are designed for varying rainfall events, up to and including, a 1 in 100 year + climate change event (see PPS25 Annex B, table B.2)?

Y/N PPS25 Preliminary Rainfall

Runoff Management for

Developments and the Interim Code of Practice for SUDS

14 For rainfall events greater than the 1 in 100 year + climate change, have you considered the layout of the development to ensure that there are suitable routes for conveyance of surface flows that exceed the drainage design?

Y/N

15 Have you provided layout plans, cross section details and long section drawings of attenuation measures, where applicable?

Y/N

PPS25 Guidance Notes




16 If you are proposing to work within 9 m of a watercourse have you applied, and received Flood Defence Consent from the EA?

Y/N or N/A Water Resources Act 1991

Land Drainage Act 1991

EA Land Drainage and Sea Defence

Byelaws enforceable under Water Resources

Act 1991

17 If you are proposing any culverting of watercourses have you applied for consent from the EA/IDB. If a development is within the Board’s district or drains to the Board’s district, a developer needs to liaise with the IDB for all development

Y/N or N/A Land Drainage Act 1991

18 The number of outfalls from the site should be minimised. Any new or replacement outfall designs should adhere to standard guidance form SD13, available from the local area Environment Agency office. Has the guidance been followed?

Y/N Guidance Driven by the Water

Resources Act 1991

No. Sustainable Drainage Systems (SUDS) Answer Policy

/Legislation

19 A) Has the SUDS hierarchy been considered during the design of the attenuation and site drainage? Provide evidence for reasons why SUDS near the top of the hierarchy have been disregarded. B) Have you provided detail of any SUDS proposed with supporting information, for example, calculations for sizing of features, ground investigation results and soakage tests? See CIRIA guidance for more information. http://www.ciria.org.uk/SUDS/697.htm

Y/N

PP

S2

5 G

uid

an

ce

20 A) Are Infiltration SUDS to be promoted as part of the development? If Yes, the base of the system should be set at least 1m above the groundwater level and the depth of the unsaturated soil zones between the base of the SUDS and the groundwater should be maximised. Notwithstanding this, soakaways and other infiltration devices should be no deeper than 2m unless otherwise agreed in writing with the Environment Agency. B) If Yes – has Infiltration testing been undertaken to confirm the effective drainage rate of the SUDS?

Y/N

Y/N

21 A) Are there proposals to discharge clean roof water direct to ground (aquifer strata)? B) If Yes, have all water down-pipes been sealed against pollutants entering the system form surface runoff or other forms of discharge?

Y/N

Y/N

22 Is the development site above a Source Protection Zone (SPZ)?

If Y go to 22 If N go to 23

Groundwater Regulations 1998




23 A) Is the development site above an inner zone (SPZ1)? B) If yes, discharge of Infiltration of runoff from car parks, roads and public amenity areas is likely to be restricted – has there been discussion with the EA as to suitability of proposed infiltration SUDS?

Y/N

Y/N

Groundwater Regulations 1998

24 A) For infill development, has the previous use of the land been considered? B) Is there the possibility of contamination? C) If yes, infiltration SUDS may not be appropriate and remediation required to be undertaken. A groundwater Risk Assessment is likely to be required (Under PPS23) Has this been undertaken before the drainage design is considered in detail?

Y/N

Y/N

Y/N PPS23

25 Have oil separators been designed into the highway and car parking drainage? PPG23: http://publications.environment-agency.gov.uk/pdf/PMHO0406BIYL-e-e.pdf

Y/N PPG23

26 Have you confirmed whether the proposed SUDS are to be adopted as part of public open space, or by a wastewater undertaker and provide supporting evidence? Alternatively, have you provide details of the maintenance contributions to be provided over the life of the development.

Y/N

Y/N

27 Have you provided details of any proposed measures to encourage public awareness of SUDS and increase community participation?

Y/N

No. Water Consumption Answer Policy

/Legislation

28 A) Have you provided the expected level of water consumption and hence the level to be attained in the Code for Sustainable Homes http://www.planningportal.gov.uk/england/professionals/en/1115314116927.html B) Have you considered whether the development can achieve a water consumption lower than 120 l/h/d (105 l/h/d for Levels 3 & 4 in the Code for Sustainable Homes, 80l/h/d as required for Levels 5 & 6)

Y/N

29 Is the proposed development likely to achieve a water consumption of between 120 l/h/d and 135 l/h/d as consistent with the latest DEFRA strategy? http://www.defra.gov.uk/environment/water/strategy/pdf/future-water.pdf

Y/N

30 Have you Provided details of water efficiency methods to be installed in houses?

Y/N

31 Have you confirmed whether the development will utilise rainwater harvesting (minimum tank size 2.5m

3 per house, see

http://www.environment-agency.gov.uk/subjects/waterres/286587/286911/548861/861599/?lang=_e

Y/N




32 Has a practicable alternative strategy been included for the supply of water for fire fighting?

Y/N

33 Have you confirmed whether grey water recycling is to be utilised and provided details?

Y/N

34 Have you provided details of any proposed measures to increase public awareness and community participation in water efficiency?

Y/N

No. Pollution prevention Answer Policy

/Legislation

35 Have you provided details of construction phase works method statement, outlining pollution control and waste management measures? See PPG2, PPG5, PPG6, PPG21 (http://www.environment-agency.gov.uk/business/444251/444731/ppg/?version=1&lang=_e ) and DTI Site Waste Management Plan, (SWMP, http://www.constructingexcellence.org.uk/resources/publications/view.jsp?id=2568)

Y/N PPG2, PPG5, PPG6, PPG21

36 A) Have you provided details of pollution prevention measures for the life of the development, such as oil and silt interceptors? B) Have you considered whether permeable pavement areas are protected from siltation? C) Have you provided details of maintenance – as with the SUDS?

Y/N

Y/N

Y/N

No. Water Supply and Sewage Treatment Answer Policy

/Legislation

37 Have you provided evidence to confirm that water supply capacity is available, and that demand can be met in accordance with the Milton Keynes Stage 1 WCS?

Y/N

38 Have you provided evidence to confirm that sewerage and wastewater treatment capacity is available, and that demand can be met in accordance with the Milton Keynes Stage 1 WCS?

Y/N

No. Conservation / Enhancement of Ecological Interest Answer Policy

/Legislation 39 Have you confirmed that any green infrastructure, such as the

surface water system, links to the neighbouring green infrastructure (River Corridors) to assist the creation and maintenance of green corridors?

Y/N Green Infrastructure Study




40 Have you confirmed that at least 25% of flood attenuation ponds/wetlands will be designed for multifunctional uses, such as providing access, footpaths, cycleways, recreational uses, and submit outline details as suggested under Natural England guidelines?

Y/N

41 A) Have you shown the impacts your development may have on the water environment? B) Is there the potential for beneficial impacts?

Y/N

Y/N

Town and Country Planning

Regulations 1999.

42 Have you confirmed all ponds within 500m of the site boundary have been surveyed for presence of great-crested newt populations?

Y/N Habitats Directive

Further information can be found in the EAs guide for developers - http://www.environment-agency.gov.uk/business/444304/502508/1506471

Milton Keynes Water Cycle Study Outline Strategy · 2013. 10. 3. · Milton Keynes Council Water...

Documents

Transcript of Milton Keynes Water Cycle Study Outline Strategy · 2013. 10. 3. · Milton Keynes Council Water...