Waverley Borough Council Water Quality Assessment

Waverley Borough Council Waverley Borough Council Water Quality Assessment

23 June 2017

Amec Foster Wheeler Environment & Infrastructure UK Limited

3 © AMEC Environment & Infrastructure UK Limited

Contents

Glossary 6

Summary 7

1. Introduction 9 1.1 Purpose of the Water Quality Assessment 9 1.2 Aims and objectives 9 1.3 Local Plan and the growth areas 10

2. Water Quality Assessments 12 2.1 Overview 12 2.2 Assessment methodology 12 Data collation 12 Baseline data 13 Growth Scenarios 16 Use of Simcat and River Quality Planning (RQP) tool 17 Graphical representation of Results 17 Overall assumptions and caveats for all water quality assessments 18

3. Results 20 3.1 Overview 20 3.2 Cranleigh, Alfold, Dunsfold, Ewhurst, Hascombe and Dunsfold Aerodrome Growth Areas 20 Upstream impacts 20 No deterioration – preventing class deterioration 20 No deterioration – limiting in class deterioration to below the 10% threshold 20 Length of river impacted 21 Getting to Good (or 2027 objective) 21 Downstream impacts beyond main water body 21 Indicative permit calculations 21 Impact of quicker housing growth 22 3.3 Elstead, Peper Harow and Thursley Growth Areas 24 Upstream impacts 24 No deterioration – preventing class deterioration 24 No deterioration – limiting in class deterioration to below the 10% threshold 24 Length of river impacted 24 Getting to Good (or 2027 objective) 24 Downstream impacts beyond main water body 24 Indicative permit calculations 25 3.4 Farnham, Churt, Dockenfield, Frensham and Tilford Growth Areas 27 Upstream impacts 27 No deterioration – preventing class deterioration 27 No deterioration – limiting in class deterioration to below the 10% threshold 27 Length of river impacted 27 Getting to Good (or 2027 objective) 27 Downstream impacts beyond main water body 28 Indicative permit calculations 28 3.5 Godalming, Busbridge, Hambledon, Witley Growth Areas 30 Upstream impacts 30 No deterioration – preventing class deterioration 30 No deterioration – limiting in class deterioration to below the 10% threshold 30 Length of river impacted 30 Getting to Good (or 2027 objective) 30

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Downstream impacts beyond main water body 31 Indicative permit calculations 31 3.6 Bramley and Wonersh Growth Areas 33 Upstream impacts 33 No deterioration – preventing class deterioration 33 No deterioration – limiting in class deterioration to below the 10% threshold 33 Length of river impacted 33 Getting to Good (or 2027 objective) 33 Downstream impacts beyond main water body 34 Indicative permit calculations 34 3.7 Haslemere Growth Area 36 Upstream impacts 36 No deterioration – preventing class deterioration 36 No deterioration – limiting in class deterioration to below the 10% threshold 36 Length of river impacted 36 Getting to Good (or 2027 objective) 36 Downstream impacts beyond main water body 36 Indicative permit calculations 36 3.8 Chiddingfold Growth Area 38 Upstream impacts 38 No deterioration – preventing class deterioration 38 No deterioration – limiting in class deterioration to less than 10% from baseline 38 Getting to Good (or 2027 objective) 38 Downstream impacts beyond main water body 38 Indicative permit calculations 39 3.9 Dry Weather flow assessments 40

4. Conclusions 42

5. References 43

Table 1 Summary of the indicative permit standards for phosphate (annual average), BOD (95th percentile) or ammonia (95th percentile) required to get water bodies to Good Ecological Status or prevent deterioration downstream WwTWs that serve growth areas in the Waverley Local Plan. 8 Table 1.1 Growth Areas and their planned housing growth along with the relevant wastewater treatment works. 10 Table 2.1 Data collated and its purpose for the water quality assessments 13 Table 2.2 Water Framework Directive classifications for Surface Water Bodies (2015 Cycle) 14 Table 2.3 Water Framework Directive Standards for water quality (in mg\l) at sample points assessed for the seven WwTWs Error! Bookmark not defined.

Figure 1.1 Growth Areas Figure 2.1 Example graph showing the Simcat model results for the water quality impacts of future housing growth due to one wastewater treatment works. 18 Figure 3.1 Modelled changes in concentrations (in mg/l), of phosphates (A - Average), BOD (B - 90%ile) and Ammonia (C - 90%ile) down the Cranleigh Waters from the upstream sample point PWER0004 to downstream sample point PWER0006, due to growth. Please note: A lack of deterioration can mean that the baseline is indistinguishable from the predicted impact line. 23 Figure 3.2 Modelled changes in concentrations (in mg/l), of Phosphates (A - Average), BOD (B - 90%ile) and Ammonia (C - 90%ile) down the River Wey from the upstream sample point PWER0110 to the end of the modelled Simcat reach downstream of Elstead WwTW, due to growth. Please note: A lack of deterioration can mean that the baseline is indistinguishable from the predicted impact line. 26 Figure 3.3 Modelled changes in concentrations (in mg/l), of Phosphates (A - Average), BOD (B - 90%ile) and Ammonia (C - 90%ile) down the River Wey from the head of the Simcat reach to downstream sample point PWER0126, due to growth. Please note: A lack of deterioration can mean that the baseline is indistinguishable from the predicted impact line. 29 Figure 3.4 Modelled changes in concentrations (in mg/l), of Phosphates (A - Average), BOD (B - 90%ile) and Ammonia (C - 90%ile) down the River Wey from the upstream sample point PWER0029 to downstream sample point PWER0151, due to growth. Please note: A lack of deterioration can mean that the baseline is indistinguishable from the predicted impact line. 32 Figure 3.5 Modelled changes in concentrations (in mg/l), of Phosphates (A - Average), BOD (B - 90%ile) and Ammonia (C - 90%ile) down the Cranleigh Waters from the upstream sample point PWER0006 to the end of the modelled Simcat reach, due to growth. Please note: A lack of deterioration can mean that the baseline is indistinguishable from the predicted impact line. 35 Figure 3.6 Modelled changes in concentrations (in mg/l), of Phosphates (A - Average), BOD (B - 90%ile) and Ammonia (C - 90%ile) down the South Wey from the head of the reach to downstream sample point PWER0026, due to growth. Please note: A lack of deterioration can mean that the baseline is indistinguishable from the predicted impact line. 37

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Appendix A Input data and modelling outputs (Excel workbook) Appendix B WFD water body and growth area maps

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Glossary

BAT Best Available Technology

BOD Biological Oxygen Demand

BC Borough Council

dpa dwellings per annum

GES Good Ecological Status

m2 Square meters

mg/l Milligrams per litre

Ml/d Mega litres per day

P Phosphorous

RQP River Quality Planning Tool

RBMP River Basin Management Plan

SIMCAT Environment Agency water quality model

WFD Water Framework Directive

WQA Water Quality Assessment

WwTW Wastewater Treatment Works

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Summary

Waverley Borough Council (referred to as the Council in this report) identified twenty two growth areas for sustainable growth in the Waverley Local Plan to help meet their housing needs, including proposals for up to 9,383 homes, to be built by 2032. As part of the evidence base to support the Plan the Council commissioned a Water Cycle Study (WCS, Capita, 2016). The WCS aimed to identify if the housing growth could impact on water quality of rivers in the area through increased discharges of treated sewage effluent from the major wastewater treatment works. This initial WCS did identify potential constraints to housing growth. To investigate these constraints further a new Water Quality Assessment (WQA) was commissioned by the Council to clarify the potential constraints and any future impacts on water quality related to housing growth within Waverley Borough that is linked to the wastewater treatment works (WwTWs) at Chiddingfold, Cranleigh, Elstead, Farnham, Godalming, Haslemere and Shamley Green. Any impacts were to be investigated in line with the WCS guidance1 and Water Framework Directive objectives (WFD) as set out in the Thames and South East River Basin Management Plans (RBMPs), specifically:

 to identify the impacts on water quality in receiving watercourses from future housing growth downstream of the seven WwTWs (i.e. from increases in discharges of treated sewage effluent from 2015 onwards);

 clarify if future housing growth will impact on the WFD objectives below  No Deterioration in class of any element.

 Ensuring the WFD water bodies can achieve the 2027 objectives as set out in the 2015 RBMPs

 Limiting in class deterioration to less than a 10% deterioration threshold from current conditions (an aspirational objective set by the Environment Agency)

 model the potential future discharge permit standards from the WwTWs to reverse potential deterioration in downstream river quality; and

 identify if there are any cumulative impacts from increases in discharges from WwTWs within the same catchment.

For all growth areas housing numbers were provided for each growth period used in the WQA (i.e. 2016- 2020, 2021-2026 and 2027-2032). For the WQA increases in effluent based on assumed occupancy rates for the housing numbers were calculated and added to the current volume of treated effluent discharged from the relevant WwTWs. The impact of this increase in treated sewage effluent on the receiving watercourses was then modelled for each growth period using the Environment Agency’s Simcat or the River Quality Planning (RQP) tools and then assessed against the current condition of the watercourses and the objectives set above. Where a potential significant deterioration was identified indicative permit standards were calculated for WwTWs, which would prevent the deterioration. The key findings of this WQA are:

 the proposed growth will impact on seven water company WwTWs (Farnham, Cranleigh, Elstead, Shamley Green, Haslemere, Godalming and Chiddingfold);

 future growth will not cause a deterioration in WFD class downstream of any of the of WwTW although the risk of deterioration will be increased downstream of Shamley Green WwTW;

 there will only be minor deterioration in water quality downstream of the majority of WwTW because of future growth (i.e. less than 10% deterioration threshold);

 water quality will exceed the 10% deterioration threshold downstream of Cranleigh WwTW and Farnham WwTW for phosphates (and ammonia for Cranleigh). The indicative permit standards

1 Guidance provided by the Environment Agency on the current best practice in undertaking Water Cycle Studies, their purpose, scope and processes for completion.

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needed to prevent this deterioration were calculated and assessed to be technically feasible and therefore not a constraint to growth i.e. new permits are required and the technology exists to meet them;

 future growth will not impact on the water body objectives set in the 2015 Thames and South East RBMP due to the technically infeasible solutions already required prior to growth for phosphates. However, this could change on completion of a national study being undertaken by water companies looking at technical, cost effective technologies for phosphate removal from final treated sewage effluent;

 Only three new indicative permits, at two WwTWs, have been assessed as being required over the lifetime of the Local Plan in order to support future proposed housing growth (Table 1);

 Future predicted water quality impacts are not constraint to housing growth proposed in the Waverley Local Plan; and

 So long as the proposed housing numbers and growth areas remain the same no further work is required to assess future water quality impacts.

 The high level capacity assessment indicated that Cranleigh WwTW could require an upgrade in order to support future housing growth. Since the original assessments were undertaken in this study Thames Water have confirmed that a separate study will be completed by later summer 2017 confirming options for the Dunsfold Aerdrome site and therefore whether Cranleigh is likely to require an upgrade.

WwTW Current permit Capacity Now (prior to 2016-2020 2021-2026 2027-2032 standards (mg\l) upgrades growth) (mg/l) (due to (due to (due to growth) (mg/l) growth) (mg/l) growth) (mg/l)

Cranleigh 2 (phosphate) Capacity 0.1* (phosphate) No new 0.5** 1.8** 3 (ammonia) upgrades permits (phosphate) (ammonia) 8 (BOD) potentially by predicted to be 2026 necessary for this period

Elstead 10 (ammonia) 2* (phosphate) 20 (BOD)

Farnham 2 (phosphate) No capacity 0.1* (phosphate) 1.4** 3 (ammonia) upgrades (phosphate) 10 (BOD) required

Godalming 2 (phosphate) 0.1* (phosphate) 4 (ammonia) 10 (BOD)

Shamley Green 20 (ammonia) 0.4* (phosphate) 30 (BOD)

Haslemere 2 (phosphate) 0.9* (phosphate) 3 (ammonia) 15 (BOD)

Chiddingfold 1 (phosphate) 0.1* (phosphate) 8 (ammonia) 20 (BOD)

* = Required to get the water body to Good Ecological Status. Supplied by the EA ** = Preventing deterioration greater than 10%

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1. Introduction

This introductory section of the report provides an overview of reason for the Water Quality Assessment.

1.1 Purpose of the Water Quality Assessment

1.1.1 Waverley Borough Council are currently producing their Local Plan for future housing growth; which was submitted for examination in December 2016. Waverley Borough Council are seeking to achieve housing growth of 519 homes per year up to 2032 across its area. To ensure that this would not have a negative impact on the environment the Council commissioned a high level Water Cycle Study (WCS, Capita, 2016). The WCS identified potential environmental constraints to the delivery of 519 homes per year, as well as more work that needs to be done in relation to water quality, potential future impacts and the mitigation required at wastewater treatment works. The Environment Agency indicated that this additional work was required in order for the Local Plan to be found sound and that the projected growth in the Local Plan can be accommodated within the lifetime of the Plan.

1.1.2 The purpose of this Water Quality Assessment (WQA) is to understand the environmental impact of proposed future housing growth within Waverley Borough on the watercourses which received discharges of treated sewage effluent from Wastewater Treatment Works (WwTWs) at Chiddingfold, Cranleigh, Elstead, Farnham, Godalming, Haslemere and Shamley Green. Any impacts have been investigated in line with the Water Framework Directive objectives (WFD). The WFD is a key directive that seeks to protect and improve the water environment and its ecology. Its overarching aim is to prevent deterioration in the status of water bodies and to achieve ‘Good Status’ for rivers, lakes and groundwater by no later than 2027. This includes:

 protecting all forms of water (inland, surface, transitional, coastal and ground);  restoring the ecosystems in and around these bodies of water; and

 reducing pollution in water bodies.

1.1.3 Along with the above WFD objectives, the WQA was based on guidance from the Environment Agency (West Thames Area) for the Waverley area and the Water Cycle Study Guidance and Requirements (EA, November 2015).

1.2 Aims and objectives

1.2.1 In agreement with the Environment Agency a number of objectives were set for the WQA, which are:

 clarify if future housing growth will impact on the WFD objectives to:

 ensure No Deterioration in WFD class of any element from the 2015 baseline;

 Ensure the WFD water bodies can achieve the 2027 objectives as set out in the 2015 RBMPs;

 Limit in class deterioration to less than 10% from the 2015 baseline (an aspirational objective set by the Environment Agency);

 model the potential future discharge permit standards from the WwTWs to reverse potential deterioration in downstream river quality; and

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 Identify if there are any cumulative impacts from increases in discharges from WwTWs within the same catchment.

1.3 Local Plan and the growth areas

1.3.1 The Waverley Borough Council area is located in the South East of England and falls predominantly within the upper reaches of the Wey catchment (Surrey). The Local Plan for the Council identifies urban areas for sustainable growth to help meet their needs, across the Council’s main towns and villages. Development is proposed at 22 urban locations, across seven major urban areas (Figure 1.1), where development would provide new homes and infrastructure in a sustainable way over the lifetime of the Local Plan, up to 2032.

1.3.2 This housing growth would impact on seven major wastewater treatment works that serve the areas. Table 1.1 and Appendix A show the housing growth planned at each of the urban areas and their associated WwTWs.

1.3.3 There is a proposal for the growth at Dunsfold Aerodrome site to have an onsite WwTW. For the purpose of this study this growth is assumed to discharge to Cranleigh WwTW. This allows representation of a ‘worst-case’ maximum potential discharge to Cranleigh WwTW, should this proposal not get taken forward. An investigation into the options for the Dunsfold Aerodrome site is being undertaken by Arcadis on behalf of Thames Water. The study will be completed within three months (i.e. by late summer 2017). The outcomes of the study will decide the future options for the site and therefore is outside the scope of this assessment. However, if onsite treatment is pursued it would reduce the impact on Cranleigh WwTW.

1.3.4 For each growth area the housing numbers and therefore results were produced based on 6-yearly RBMP cycles, in order to bring the WQA in line with the WFD. Although the WFD objectives currently only state objectives for getting to Good Status by 2027, the six year planning cycle continues beyond that in order to ensure no deterioration. Any growth beyond 9,383 dwellings, noted in Table 1.1, would need to be included in further studies and fall outside the scope of this WQA.

Table 1.1 Growth Areas and their planned housing growth along with the relevant wastewater treatment works.

Growth area WwTW 2016-2020 2021-2026 2027-2032

Chiddingfold Chiddingfold 9 95 10

Cranleigh Cranleigh 1282 113 67

Alfold 143 2 3

Dunsfold 85 2 7

Ewhurst 64 1 3

Hascombe 4 0 0

Dunsfold Aerodrome 110 1025 1465

Elstead Elstead 85 58 16

Peper Harow 0 0 5

Thursley 1 1 1

Farnham Farnham 1662 248 258

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Growth area WwTW 2016-2020 2021-2026 2027-2032

Churt 7 2 2

Dockenfield 7 2 2

Frensham 14 3 8

Tilford 14 2 3

Godalming Godalming 686 98 242

Busbridge 67 2 22

Hambledon 2 0 0

Witley 51 432 41

Haslemere Haslemere 478 89 170

Bramley Shamley Green 59 10 19

Wonersh 14 3 4

Note: Growth predictions as of November 2016. The figures in this table, provided by Waverley Borough Council, are derived from the Local Plan housing trajectory and differ slightly from those in the Local Plan allocations. The table above includes all green rated LAA sites and the windfall estimate for villages as a whole has been distributed and included in the assessment.

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4 # 1 0 0 0 7 4 1 0 0 0

6 Farnham 4 1 0 # 0 0 5 4 1 0 0 0

4 # 4 1

0 # 0

0 Shamley Green

3 Elstead Godalming 4 1 0 0 0 2 4 1 0 0 0 1 4 1 0 0 0 0 4 1 0 0

0 # 9 3 1 0 0

0 Cranleigh 8 3 1 0 0 0 7 3 1 0 # 0 0 6 3 1 0

0 Chiddingford 0 5 3 1 0 0 0 4 3 1 0 0 0 3 3 1 0 0

0 # Haslemere 2 3 1 0 0 0 1 3 1 0 0 0 0 3 1 0 0 0 9 2 1 0 0 0 8 2 1 0 0 0 7 2 1 0

d 0

x 0

m 6

. 2

. K1 ey

F \ WwTWs Waverley Borough s #

n i Council Wastewater

a r Watercourse

D Treatment Work

Q Assessments

v a Figure 1.1

9 Growth Areas

s 0 2 4 6 km

o r Scale at A4: 1:150,000

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2. Water Quality Assessments

This section of the report provides a summary of the data, methods and results for the Water Quality Assessments for the main WwTWs associated with the growth areas.

2.1 Overview

2.1.1 In order to complete the WQA and assess whether future housing growth would impact on water quality and WFD compliance a series of steps had to be taken including:

 Data collation;

 Setting the baseline;  Clarifying the growth scenarios;

 Modelling the water quality impact of future housing growth on the receiving watercourses; and

 Modelling any new environmental permit standards that might be required to support growth.

2.1.2 The data collation step was the most important in order to ensure that the correct data was used to assess the water quality impacts over the lifetime of the Local Plan. Following a data collation step, a review was undertaken of the information, to get an understanding of the current ‘baseline’ receiving water conditions. Growth plans provided by the Council were allocated to appropriate WwTW catchments, and used to calculate the increase in discharge at the WwTWs. Simcat was used to model the impacts of the discharge increases, before being plotted graphically. Where a deterioration in WFD class was predicted or the water quality exceeds the 10% deterioration at the downstream point, the River Quality Planning tool (RQP) was used. This enabled understanding of consent requirements at the individual WwTWs to ensure receiving water quality does not cause a deterioration in WFD class or exceed the 10% deterioration threshold. Further detail on these steps are described in the sections below, and assumptions and caveats used in the modelling are summarised.

2.2 Assessment methodology

Data collation 2.2.1 For the WQA a number of data sets were required from the Environment Agency and Waverley Borough Council (Table 2.1). This included information on the growth being considered, estimates of river flow, river quality and also data on effluent flow and quality. For the river and effluent quality the main focus was on phosphates, ammonia and Biological Oxygen Demand (BOD, a proxy for Dissolved Oxygen in rivers).

2.2.2 All data sets were reviewed to ensure that information was complete and suitable, before being converted to a format for use within the model. Where sample data was not available existing model data from the Environment Agency’s Simcat tool or mid EQS class boundary values were used instead2.

2 Any data gaps were filled based on guidance from the Environment Agency and are noted in the later sections.

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Table 2.1 Data collated and its purpose for the water quality assessments

Data Description and purpose Source

WwTW effluent quality data (2010- Current WwTW quality (BOD, Ammonia and Phosphate) Environment Agency 2015) discharged to receiving waters. For input to the Simcat and RQP modelling tools.

WwTW flow data (2010-2015) Current WwTW flows discharged to receiving waters. For Environment Agency input to the Simcat and RQP modelling tools.

River quality data (2010-2015) Current river quality (BOD, Ammonia and Phosphate) in Environment Agency receiving waters upstream and downstream of WwTWs (where available). For input to the Simcat and RQP modelling tools.

River flow data (2010-2015) Current river flow in receiving waters upstream and Environment Agency downstream of WwTWs (where available). For input to the Simcat and RQP modelling tools.

Simcat model (Thames catchment) Water quality model for the Thames Catchment, used to Environment Agency undertake the WQA

Growth areas and annual housing Proposed future dwelling numbers in each growth area. Waverley Borough numbers For input to the Simcat and RQP modelling tools to Council understand potential discharge increase at WwTWs

Baseline data 2.2.3 This section provides a high level summary of the current conditions of the watercourses associated with the growth areas and their WwTWs.

2.2.4 The growth areas are spread across six WFD water bodies, predominantly located in the Thames River Basin District (RBD), with Chiddingfold being located in the South East RBD (Appendix Figures B1-6). As reported in the 2015 Cycle 2 RBMPs all of the water bodies are at less than Good Ecological Status although water quality was generally found to be compliant (Table 2.2). This was except for phosphates which was at Moderate or Poor Status in all water bodies.

2.2.5 The main baseline water quality data can be found in Appendix A. As noted previously all growth areas were assigned to a major WwTW for the WQA. River and discharge data was then collated for these sites including:

 WwTW effluent quality and volume ;

 river quality data from upstream and downstream of the WwTWs;

 Simcat estimates for river flow and quality where no other data was available; and  volume estimates for increase in effluent due to proposed housing growth.

2.2.6 Where no river quality data was available, estimates from the Simcat model were used. Except for Chiddingfold WwTW where upstream quality was assumed to be the mid-range values for the WFD classifications3 (i.e. for BOD Good Status is 4 mg\l, therefore the 90%ile mid-range estimate was 3.5 mg\l).

2.2.7 Table 2.3 shows the WFD Standards that were used for all downstream sample points in the WwTW assessments when calculating any permits. Ammonia standards were the same for all sample points, however, the phosphate standards varied between the rivers.

3 As agreed with the Environment Agency

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Table 2.2 Water Framework Directive classifications for Surface Water Bodies (2015 Cycle4)

Growth area WwTW Receiving Watercourse WFD Waterbody Overall water Element(s) Not Element(s) at Good or High body status achieving Good Status Status

Chiddingfold Chiddingfold

Cranleigh Cranleigh Waters Cranleigh Waters Moderate Macrophytes Temperature GB106039017810 (Moderate) BOD Alfold Phosphates Ammonia (Moderate) pH Dissolved Oxygen Dunsfold Fish Cranleigh Invertebrates Ewhurst Chemicals and Specific pollutants Hascombe

Dunsfold Aerodrome

Bramley Shamley Green Wonersh

Elstead Wey Wey (Tilford to Moderate Macrophytes Temperature Shalford) (Moderate) Ammonia GB106039017820 Fish pH Peper Harow Elstead (Moderate) Dissolved Oxygen Phosphates Invertebrates Thursley (Moderate) Chemicals

Farnham Wey North Wey (Alton to Moderate Macrophytes Temperature Tilford) (Moderate) Ammonia Churt GB106039017830 Fish pH (Moderate) Dissolved Oxygen Phosphates (Poor) Invertebrates Dockenfield Farnham Chemicals and Specific pollutants Frensham

Tilford

4 More information available on the Environment Agency’s Catchment Data Explorer website - http://environment.data.gov.uk/catchment-planning/

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Growth area WwTW Receiving Watercourse WFD Waterbody Overall water Element(s) Not Element(s) at Good or High body status achieving Good Status Status

Godalming Wey Wey (Tilford to Moderate Macrophytes Temperature Shalford) (Moderate) Ammonia Busbridge GB106039017820 Fish pH Godalming (Moderate) Dissolved Oxygen Phosphates Invertebrates Hambledon (Moderate) Chemicals Witley

Haslemere Wey South Wey Moderate Fish Temperature (Haslemere to (Poor) Ammonia Bordon) Phosphates (Poor) pH Haslemere GB106039017700 Dissolved Oxygen Invertebrates Chemicals

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Table 2.3 Water Framework Directive Standards for water quality (in mg\l) at sample points assessed for the seven WwTWs

Determinand River Sample Relevant WwTW High Good Moderate Poor Bad point

Phosphate PWER0006 Cranleigh STW 0.03 0.059 0.154 0.956 2

PWER0046 Elstead STW 0.035 0.066 0.169 0.993 2

PWER0126 Farnham STW 0.04 0.074 0.183 1.027 2

PWER0151 Godalming STW 0.037 0.07 0.176 1.009 2

d\s Shamley Shamley Green 0.03 0.059 0.154 0.956 2 Green STW

PWER0026 Haslmere STW 0.018 0.038 0.109 0.829 2

F0003142 Chiddingfold STW 0.03 0.05 0.15 0.5 2

BOD PWER0006 Cranleigh STW 4 5 6.5 9 11

PWER0046 Elstead STW 4 5 6.5 9 11

PWER0126 Farnham STW 3 4 6 7.5 9.5

PWER0151 Godalming STW 4 5 6.5 9 11

d\s Shamley Shamley Green 4 5 6.5 9 11 Green STW

PWER0026 Haslmere STW 3 4 6 7.5 9.5

F0003142 Chiddingfold STW 3 4 6 7.5 9.5

Ammonia All All 0.3 0.6 1.1 2.5 4.5

2.2.8 To assess whether future housing would cause a greater than 10% deterioration in water quality in the receiving watercourses a 10% threshold had to be set. This was done by setting the 2015 baseline (i.e. what is the water quality now) and then adding 10% onto it.

Growth Scenarios 2.2.9 The Council provided Amec Foster Wheeler with details of the proposed growth plans within the Local Plan, which only included housing growth. Economic development growth proposals were not considered. This results in a total of 9383 new dwellings with annual rates dependent on the growth area which were then grouped and the sum calculated for each time period (2016-2020, 2021-2026 etc). Only one set of annual rates were provided for each growth area.

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2.2.10 Models were run for each period showing what the potential water quality impacts could be on the receiving watercourses by 2020, 2026 and 2032. The model results were assessed against the WFD objectives and the WQA objectives as set out in section 1.2.

Use of Simcat and River Quality Planning (RQP) tool 2.2.11 For all of the WwTW assessments, Simcat and RQP models were identified to be the most appropriate tool to undertake the modelling as they use monte carlo calculations5. This allows probable scenarios to be modelled when assessing future impacts. The Simcat model allows for more complex scenarios to be modelled (e.g. catchments), where either multiple WwTWs might interact or other sources or pollutants might need to be accounted for. The RQP tool is more simplistic and can be used for modelling point source impacts of single discharges. Both models were used to model the impacts on the WwTW discharges on phosphate, ammonia and BOD concentrations in rivers.

2.2.12 As the majority of the growth areas and WwTWs are located in the Wey catchment, Simcat was used to model the potential water quality impacts of increased discharges of treated sewage effluent from the proposed future housing growth. This was done in order to account for upstream impacts from growth areas as well as impacts from individual WwTWs (e.g. the impact on Cranleigh Waters at Shamley Green WwTW will also be dependent on the upstream impact from Cranleigh WwTW). Chiddingfold WwTW is located in the upper reaches of the Arun catchment and has no major upstream influences and as such was modelled using the RQP tool. The RQP tool was also used to model any indicative permit standards for WwTWs.

2.2.13 A review was undertaken of the calibration of the Simcat model, following an update to the current baseline flow and water quality both at the WwTWs and within the receiving waters. Where a mismatch remained between the observed data and the modelled outputs actions were taken to improve this, with pre-existing calibration used if required.

2.2.14 It is expected that any upgrade to any of the seven WwTWs (i.e. Elstead, Farnham, Haslemere, Godalming, Cranleigh, Shamley Green, and Chiddingfold) would include increasing the capacity to mitigate any emergency discharges like storm events. However, these have not been modelled in this WQA as they are intermittent events and are unlikely to impact on long term water quality compliance.

Graphical representation of Results 2.2.15 To more easily assess the extent of water quality impacts due to increased discharges of treated sewage effluent caused by future housing growth, the model outputs from Simcat were put into graphical format. The graphs were set out to show the potential impacts at the end of each period of housing growth, estimates on the length of river reach impacted as well showing whether the impacts would cause significant deterioration. Figure 2.1 shows an example of the graphs which specifically show:

 WFD class boundaries specific to the determinand and watercourse (marked as A);

 The upstream actual or estimate river quality (marked as B);

 The point and immediate impact of the WwTW discharge (marked as C);  The downstream point used for the deterioration assessments (marked as D);

 The 2015 baseline set using current data from which the impact of increase in volume of treated effluent was modelled (marked as E);

 The results showing the level of impact of the increases in the treated effluent at the end of each growth period (marked as F); and

5 A standard mathematical method used for probabilistic modelling.

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 The 10% deterioration threshold, set based on the 2015 baseline and used as an aspirational target by the Environment Agency (marked as G).

2.2.16 If the future predictions of water quality (i.e. 2020, 2026 and 2032 predictions in Figure 2.1) were above the baseline, then a deterioration was identified. However, it was only deemed to be significant if the results showed that at the downstream sample point, the concentrations were either a different WFD class or were greater than the 10% threshold. For example Figure 2.1 shows that although all future predictions show a deterioration from the baseline by PWER0006 they are still Moderate Status. Therefore there is no class deterioration. However, by 2026 the deterioration does exceed the 10% deterioration threshold. Therefore an indicative permit would need to be calculated in order to show how to prevent it.

2.2.17 Should a length of watercourse greater than 1.5km or 15% of the overall waterbody length show deterioration in WFD class or exceed the 10% threshold then there is considered to be a significant length of river deterioration. Figure 2.1 indicates that in this particular example more than 1.5km of watercourse has deteriorated in WFD class in the 2032 scenario and deterioration over the 10% threshold in 2026 and 2032 is greater than 1.5km and therefore there is considered to be a significant length of river deterioration.

2.2.18 Section 3 contains the graphs and explanatory text for the seven WwTWs. The background data and results can be found in Appendix A.

2.2.19 It should be noted that in cases where the future predictions show no change from the 2015 baseline, the lines will overlap on the graph which may hide the 2015 baseline. However, all graphs include all scenarios noted in the legends.

Figure 2.1 Example graph showing the Simcat model results for the water quality impacts of future housing growth due to one wastewater treatment works.

Overall assumptions and caveats for all water quality assessments 2.2.20 A number of assumptions and caveats have been identified and used when undertaking the water quality modelling work. These were taken from standard approaches in the UK and were used in order to improve the certainty behind the findings and to take a precautionary approach due to some uncertainties (e.g. number of people who will eventually live in the dwellings). The assumptions and caveats are:

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 A single dwelling has an occupancy of 5 people (this follows national guidance but presents a worst case scenario compared to the national average of 2.3)7

 Assessment undertaken based on 120l/per person/per day residential waste water flow loading to a WwTW (equivalent to Level 1 / 2 of the Code for Sustainable Homes). Following representations made at pre-submission stage, the submission version of the Waverley Local Plan was amended to include reference to lower water usage. Policy CC2 ‘Sustainable Construction and Design’ states ‘that new dwellings shall be required to meet with the requirement of 110 litres per person per day’;

 There has been no consideration of future climate change within the modelling itself, however consideration is made when discussing the results (Section 3);

 The water quality modelling was based on predicted flow estimates for growth on top of current mean discharge volume irrespective of the WwTW Dry Weather Flow (DWF) permit (i.e. the volume of effluent going to the works during dry conditions). It is assumed that the permitted DWF will be increased in line with growth predictions and other required permit changes based on the model results;

 Future impacts were assessed based on the current quality of effluent the WwTWs produce (e.g. a baseline set using 2010-2015 data) as set out in Appendix A;

 For Chiddingfold WwTW upstream quality was assumed to be the mid-range values for the WFD classifications6 (i.e. for BOD Good Status is 4 mg\l, therefore the 90%ile mid-range estimate was 3.5 mg\l);

 For this report it is assumed that the increase in flows for Dunsfold Aerodrome will go to Cranleigh WwTW. Any new permits for onsite treatment or transfer to alternative WwTW will have to be modelled outside of this report;

 Growth at Alfold has the potential to drain to Loxwood WwTW rather than Cranleigh WwTW, however this would not be confirmed until specific sites are designated. Therefore this option is not considered in this assessment, and the inclusion provides an assessment of worst case growth at Cranleigh WwTW;

 Waverley Borough Council confirmed that on 5th January 2017, an appeal was allowed for the erection of 120 dwellings at the Hewitts Industrial Estate, Cranleigh. This site was not considered in the assessment, which is based on information available in November 2016;

 The Simcat model used assumes a continued over performance for phosphate at Cranleigh WwTW. The current permit at the WwTW is 2mg/l, but Thames Water actually operate it at 0.5mg/l; and

 The assessment has been undertaken on the assumption that there is no deterioration in WwTW performance as a result of growth. This study only reviews the impact of increased flows from the WwTWs as a result of growth, no consideration has been made of any deterioration in quality as headroom is taken up.

2.2.21 It is important to note that the household occupancy value used is based on an assumption that an average house comprises 3 bedrooms, a size which is ‘designed for a minimum population of 5 people7. This is an overestimate based on an average household size of 2.4 persons7 in 2011. For the purposes of modelling the use of 5 persons per dwelling provides a ‘worst case’ Scenario for consideration.

6 As agreed with the Environment Agency 7 http://www.ons.gov.uk/ons/rel/census/2011-census/population-estimates-by-five-year-age-bands--and-household-estimates--for-local- authorities-in-the-united-kingdom/stb-population-and-household-estimates-for-the-united-kingdom-march-2011.html

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3. Results

This section of the report provides the results of the WQA undertaken for the proposed housing numbers for the growth areas in Waverley Borough Council.

3.1 Overview

3.1.1 The impacts of proposed growth were based on the baseline and assumptions detailed in Section 2. Modelling of the water quality impacts of housing growth has been summarised in the following section, along with a cumulative assessment for all growth areas. This takes account of the impact of growth plans to 2020, 2026 and 2032 to allow understanding of the timescales of the impacts. For each growth area consideration is made of the baseline receiving water classification followed by any potential for changes in WFD class or deterioration in exceedance of the 10% deterioration threshold due to growth. The potential to reach the WFD objective of Good Status is considered where this is not currently the case. Any possible impacts beyond the main water body are also considered.

3.2 Cranleigh, Alfold, Dunsfold, Ewhurst, Hascombe and Dunsfold Aerodrome Growth Areas

3.2.1 The growth areas of Cranleigh, Alfold, Dunsfold, Ewhurst, Hascombe and Dunsfold Aerodrome are all considered to be served by Cranleigh WwTW and as such could impact on the WFD water body Cranleigh Waters.

3.2.2 While there is the potential for Growth within Dunsfold Aerodrome site to discharge to an onsite WwTW (Section 1.3.3), inclusion within this assessment allows a ‘worst-case’ capacity consideration at Cranleigh WwTW, should the proposal not be taken forward.

Upstream impacts 3.2.3 The WwTW is towards the upper reaches of the water body with no other major WwTWs upstream. As such there are no predicted impacts upstream of Cranleigh WwTW associated to housing growth.

3.2.4 The Environment Agency’s Thames RBMP has set an overall objective of Moderate Status by 2027 for this water body, which is the current classification. This is due to phosphates not being predicted to improve. As such, for the purpose of this WQA no upstream improvements were predicted when assessing the impact of future growth.

No deterioration – preventing class deterioration 3.2.5 No deterioration of WFD class has been identified for any of the determinands downstream of the WwTW during the life of the Local Plan beyond the status noted in the baseline (i.e. the classification was Moderate before and after housing growth, Figure 3.1).

No deterioration – limiting in class deterioration to below the 10% threshold 3.2.6 The modelling results for phosphates indicate that by 2026 there will be a greater than 10% deterioration in water quality by sample point PWER0006 (17%, Figure 3.1). For ammonia, all housing growth projections caused a greater than 10% deterioration at the downstream sampling point. This was seen with a 20% deterioration by 2020, 37% by 2026 and a 53% deterioration by 2032. This indicates there will be a deterioration greater than the Environment Agency’s aspirational 10% threshold. Therefore consideration will need to be made of permit limits (for

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phosphates and ammonia) that would be required at the WwTW to ensure this deterioration is mitigated (considered further in Section 3.2.13). The modelling indicated that at no point would BOD levels deteriorate more than 10% from the 2015 baseline.

Length of river impacted 3.2.7 From the point of discharge, a length of more than 1.5km of river, will be of Poor status within 2032 (Figure 3.1). Growth planned within 2026 and 2032 will impact on more than 1.5km, which will exceed the 10% deterioration threshold (for phosphate and ammonia). Therefore there is considered to be potential for a significant length of river deterioration. As such a new permit would be required in order to mitigate the impact.

Getting to Good (or 2027 objective) 3.2.8 When using the 2015 baseline and growth predictions, ammonia and BOD remained at High status respectively at PWER0006. As such no further assessments were undertaken, although it should be noted that continued compliance to High is dependent upon Cranleigh WwTW continuing to produce treated effluent to the same quality as noted in Appendix A.

3.2.9 In the baseline and WFD classifications phosphates have been assessed as being Moderate Status at PWER0006 with a 2015 objective of Moderate. Therefore growth is unlikely to impact achievement of the WFD objective.

3.2.10 For the WFD the Environment Agency undertook a national review of what would be required to get phosphates in rivers to Good Status. The Environment Agency’s review of the permits indicated that a Permit of 0.1 mg\l would be required at Cranleigh WwTW to get the water body to Good Status prior to the proposed development. The permit for phosphate is less than the 0.5 mg\l technically feasible threshold set by the Environment Agency and Ofwat. Although an assumption of achieving 0.1 mg\l is now being made by water companies. As such the water body downstream of Cranleigh WwTW could get to Good Status for phosphate irrespective of future housing growth. As this is the tightest permit possible housing growth is likely to have limited or no impact on the water bodies future ability to reach GES8 for the water quality determinands.

Downstream impacts beyond main water body 3.2.11 As no significant deterioration (i.e. deterioration in WFD class) is predicted by the downstream sample point no impacts are expected in the next downstream water body. As such no assessments were undertaken on water bodies further downstream.

Indicative permit calculations 3.2.12 As no deterioration of WFD class has been identified at the downstream sample point for any of the determinands no new indicative permit limits were calculated for that objective. However, as indicative permit limits were calculated for ammonia and phosphates to:

 prevent the predicted greater than 10% deterioration; and

 reduce the length of river impacted.

3.2.13 The modelling indicated that consents of 1.8 mg\l and 0.5 mg\l would be required for ammonia and phosphates respectively. A high level review indicates that there are technological feasible solutions for both indicative consents.

8 This is dependent upon the outcome of the national study, due to be published in 2017, looking at what permit limits will be technically and economically feasible in the UK in the future.

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Impact of quicker housing growth 3.2.14 Based on a planning decision by Waverley Council for the Knowle Park Initiative, it was agreed that 265 homes could be brought forward for construction. This meant that a potential change to the phasing of growth shown in Table 3.1. This had the potential to change how early a significant impact could be seen in the receiving watercourse but would have no bearing on the results indicated for 2030 as the total number of houses in that period did not change.

Table 3.1 Changes in housing growth for Cranleigh Waters, pre and post Knowle Park decision.

2015-2020 2020-2025 2025-2030 Total

As before 1688 1143 1545 4376

Change based on 1953 878 1545 4376 Knowle Park Initiative 3.2.15 The modelling indicated that bringing 265 homes would increase the dry weather weather (DWF) by 15% beyond the original phasing, although the cumulative number of houses by 2025 would remain the same. The modelling results from this updated phasing indicated that for the 2020 predictions there was no significant effect on the results shown above and in Figure 3.1. The results still indicated that even with greater housing growth earlier there would be no significant deterioration in class with both phosphate and ammonia still showing greater 10% deterioration. There was no impact on the predictions for 2025 and 2030.

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Figure 3.1 Modelled changes in concentrations (in mg/l), of phosphates (A - Average), BOD (B - 90%ile) and Ammonia (C - 90%ile) down the Cranleigh Waters from the upstream sample point PWER0004 to downstream sample point PWER0006, due to growth. Please note: A lack of deterioration can mean that the baseline is indistinguishable from the predicted impact line.

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3.3 Elstead, Peper Harow and Thursley Growth Areas

3.3.1 The growth areas of Elstead, Peper Harow and Thursley are all served by Elstead WwTW and as such could impact on the WFD water body Wey (Tilford to Shalford).

Upstream impacts 3.3.2 Elstead WwTW is located on the main River Wey with several other major WwTW upstream (e.g. Haslemere and Farnham). However, as shown in Figure 3.2 no significant changes in water quality were predicted over the lifetime of the Local Plan. As such housing growth at sites higher up in the catchment is not expected to impact on the growth areas served by Elstead WwTW.

3.3.3 The Environment Agency’s Thames RBMP has set an objective of Moderate Status by 2027 for this water body, which is the current classification. As such, for the purpose of this WQA no upstream improvements were predicted when assessing the impact of future growth.

No deterioration – preventing class deterioration 3.3.4 No deterioration of WFD class has been identified for any of the determinands downstream of the WwTW during the life of the Local Plan beyond the status noted in the 2015 baseline (i.e. the downstream classification is the same before and after housing growth, Figure 3.2). In particular BOD shows no change from 2015 to the end of the plan period.

No deterioration – limiting in class deterioration to below the 10% threshold 3.3.5 The modelling of the future housing growth indicate that although there will be some deterioration downstream of Elstead WwTW it will be less than the Environment Agency’s aspirational 10% threshold. This indicates that water quality should not be a constraint to future housing.

Length of river impacted 3.3.6 From the point of discharge, there are no WFD class deteriorations for any determinand, and all impact modelled is below the 10% deterioration threshold. Therefore there is not considered to be any significant length of river deterioration.

Getting to Good (or 2027 objective) 3.3.7 When using the 2015 baseline and growth predictions, ammonia and BOD remained at High status downstream of Elstead WwTW. As such no further assessments were undertaken, although it should be noted that continued compliance to High is dependent upon Elstead WwTW and upstream WwTWs continuing to produce treated effluent to the same quality as noted in Appendix A.

3.3.8 In the baseline and WFD classifications phosphates have been assessed to be Moderate Status with a 2015 objective of Moderate. Therefore growth is unlikely to impact achievement of the WFD objective.

3.3.9 The Environment Agency’s review of the permits indicated that a permit of 2 mg\l would be required to get the water body to Good Status prior to the proposed development (this is as well as further improvements at upstream WwTWs). Therefore the housing growth is likely to have limited or no impact on the water bodies future ability to reach GES, should this become the objective.

Downstream impacts beyond main water body 3.3.10 As no significant deterioration is predicted by the downstream sample point no impacts are expected in the next downstream water body. As such no further assessments were undertaken.

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Indicative permit calculations 3.3.11 As no significant deterioration has been identified for any of the determinands no new indicative permit limits were calculated.

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Figure 3.2 Modelled changes in concentrations (in mg/l), of Phosphates (A - Average), BOD (B - 90%ile) and Ammonia (C - 90%ile) down the River Wey from the upstream sample point PWER0110 to the end of the modelled Simcat reach downstream of Elstead WwTW, due to growth. Please note: A lack of deterioration can mean that the baseline is indistinguishable from the predicted impact line.

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3.4 Farnham, Churt, Dockenfield, Frensham and Tilford Growth Areas

3.4.1 The growth areas of Farnham, Churt, Dockenfield, Frensham and Tilford are all served by Farnham WwTW and as such could impact on the WFD water body North Wey (Alton to Tilford).

Upstream impacts 3.4.2 Farnham WwTW is located on the North arm of the River Wey with only one WwTW upstream (i.e. Alton WwTW). However, no significant growth was included in this WQA for Alton as it falls within a different council area and no information was available. Additionally as any growth at Alton would need to abide by the same WFD objectives it is expected that any deterioration would not be significant and therefore would not impact on the growth areas served by Farnham WwTW.

3.4.3 As the upstream data indicates that the determinands are already at Good or High Status no further improvements are expected so no changes were predicted for upstream quality as part of the Thames RBMP and 2027 objectives.

No deterioration – preventing class deterioration 3.4.4 No deterioration of WFD class from the 2015 baseline has been identified at PWER0126, downstream of Farnham WwTW, for any of the determinands due to housing growth (Figure 3.3). The results indicate that ammonia and BOD will remain at Good Status, whilst phosphates will remain at Poor Status.

No deterioration – limiting in class deterioration to below the 10% threshold 3.4.5 The modelling results for phosphates indicate that by 2032 deterioration will exceed the Environment Agency’s aspirational 10% threshold by sample point PWER0126 (11%, Figure 3.3). Therefore consideration will need to be made of permit limits that would be required at the WwTW to ensure this deterioration is mitigated (considered further in Section 3.4.12). Deteriorations in ammonia and BOD would not be significant and would not exceed their thresholds.

Length of river impacted 3.4.6 From the point of discharge, there are no WFD class deteriorations for any determinand, and all impact modelled for BOD and ammonia is below the 10% deterioration threshold. 2032 growth has the potential to exceed the 10% deterioration threshold, however the length of reach impacted will be less than 1.5km. Therefore there is not considered to be any significant length of river deterioration.

Getting to Good (or 2027 objective) 3.4.7 When using the 2015 baseline and growth predictions, ammonia and BOD remained at Good Status respectively at PWER0126. As such no further assessments were undertaken, although it should be noted that continued compliance to High is dependent upon Farnham WwTW continuing to produce treated effluent to the same quality as noted in Appendix A.

3.4.8 In the baseline and WFD classifications phosphates have been assessed to be Poor Status with a 2015 objective of Poor status. Therefore growth is unlikely to impact achievement of the WFD objective.

3.4.9 The Environment Agency’s review of the permits indicated that a phosphate permit of 0.1 mg\l would be required to get the water body to Good Status prior to the proposed development (this is as well as further improvements at upstream WwTWs). The permit for phosphate is less than the 0.5 mg\l technically feasible threshold set by the Environment Agency and Ofwat, although an assumption of achieving 0.1 mg\l is now being made by water companies. As such the water body downstream of Farnham WwTW could get to Good Status for phosphate irrespective of future

housing growth. As this is the tightest permit possible housing growth is likely to have limited or no impact on the water bodies future ability to reach GES9 for the water quality determinands.

Downstream impacts beyond main water body 3.4.10 As no significant deterioration is predicted by the downstream of the WwTW no impacts are expected in the next downstream water body. As such no further assessments were undertaken.

Indicative permit calculations 3.4.11 As no deterioration of WFD class has been identified for any of the determinands at the downstream sample point no new indicative permit limits were calculated for that particular WFD objective. However, indicative permit limits were calculated for phosphates to prevent the predicted greater than 10% deterioration.

3.4.12 The modelling indicated that a consent of 1.4 mg\l would be required. A high level review indicates that is technologically feasible and could be delivered in order to support future housing growth. As deterioration in ammonia and BOD was predicted to be less than 10%, no new indicative permit limits were calculated for them.

9 This is dependent upon the outcome of the national study, due to be published in 2017, looking at what permit limits will be technically and economically feasible in the UK in the future.

Figure 3.3 Modelled changes in concentrations (in mg/l), of Phosphates (A - Average), BOD (B - 90%ile) and Ammonia (C - 90%ile) down the River Wey from the head of the Simcat reach to downstream sample point PWER0126, due to growth. Please note: A lack of deterioration can mean that the baseline is indistinguishable from the predicted impact line.

3.5 Godalming, Busbridge, Hambledon, Witley Growth Areas

3.5.1 The growth areas of Godalming, Busbridge, Hambledon and Witley are all served by Godalming WwTW and as such could impact on the WFD water body Wey (Tilford to Shalford) water body.

Upstream impacts 3.5.2 Godalming WwTW is located on the main River Wey with several major WwTW upstream, including Farnham, Haslemere and Elstead WwTW. However, as with the model for Elstead WwTW no significant upstream impacts were seen on water quality. As such upstream influences are not expected to impact on the growth areas served by Godalming WwTW.

3.5.3 The Environment Agency’s Thames RBMP has set an objective of Moderate Status by 2027 for this water body, which is the current classification. As such, for the purpose of this WQA no upstream improvements were predicted when assessing the impact of future growth.

No deterioration – preventing class deterioration 3.5.4 No deterioration of WFD class has been identified for any of the determinands downstream of the WwTW during the life of the Local Plan due to housing growth from the 2015 baseline (Figure 3.4). In particular phosphate concentrations show no change from 2015 to the end of the plan period. The results indicate that ammonia and BOD will remain at High Status downstream of the WwTWs, whilst phosphates will remain at Moderate Status.

No deterioration – limiting in class deterioration to below the 10% threshold 3.5.5 The modelling of the future housing growth indicate that although there will be some deterioration downstream of Godalming WwTW it will be less than the Environment Agency’s aspirational 10% threshold. This indicates that water quality should not be a constraint to future housing.

Length of river impacted 3.5.6 From the point of discharge, there are no WFD class deteriorations for any determinand, and all impact modelled is below the 10% deterioration threshold. Therefore there is not considered to be any significant length of river deterioration.

Getting to Good (or 2027 objective) 3.5.7 When using the 2015 baseline and growth predictions, ammonia and BOD remained at High Status respectively at PWER0126. As such no further assessments were undertaken, although it should be noted that continued compliance to High is dependent upon Farnham WwTW continuing to produce treated effluent to the same quality as noted in Appendix A.

3.5.8 In the baseline and WFD classifications phosphates have been assessed to be Moderate Status with a 2015 objective of Moderate. Therefore growth is unlikely to impact achievement of the WFD objective.

3.5.9 The Environment Agency’s review of the permits for phosphates indicated that a permit of 0.1 mg\l would be required to get the water body to Good Status prior to the proposed development (this is as well as further improvements at upstream WwTWs). The permit for phosphate is less than the 0.5 mg\l technically feasible threshold set by the Environment Agency and Ofwat, although an assumption of achieving 0.1 mg\l is now being made by water companies. As such the water body downstream of Godalming WwTW could get to Good Status for phosphate irrespective of future

housing growth. As this is the tightest permit possible housing growth is likely to have limited or no impact on the water bodies future ability to reach GES10 for the water quality determinands.

Downstream impacts beyond main water body 3.5.10 As no significant deterioration is predicted by the downstream of the WwTW no impacts are expected in the next downstream water body. As such no further assessments were undertaken.

Indicative permit calculations 3.5.11 As no deterioration of WFD class has been identified for any of the determinands no new indicative permit limits were calculated.

3.5.12 All future predictions for water quality downstream of Godalming WwTW indicated that deterioration would be less than 10%. Therefore no new indicative permit limits were calculated.

10 This is dependent upon the outcome of the national study, due to be published in 2017, looking at what permit limits will be technically and economically feasible in the UK in the future.

Figure 3.4 Modelled changes in concentrations (in mg/l), of Phosphates (A - Average), BOD (B - 90%ile) and Ammonia (C - 90%ile) down the River Wey from the upstream sample point PWER0029 to downstream sample point PWER0151, due to growth. Please note: A lack of deterioration can mean that the baseline is indistinguishable from the predicted impact line.

3.6 Bramley and Wonersh Growth Areas

3.6.1 The growth areas of Bramley and Wonersh are served by Shamley Green WwTW and as such could impact on the WFD water body Cranleigh Waters.

Upstream impacts 3.6.2 Shamley Green WwTW is located on the Cranleigh Waters downstream of Cranleigh WwTW and its associated growth areas. The modelling predicts that the upstream influences from Cranleigh WwTW could cause a significant deterioration in upstream water quality before the watercourse reaches Shamley Green WwTW (i.e. greater than 10% deterioration). However, there is no clear evidence that show whether it has a cumulative affect with the Shamley Green WwTW discharge.

3.6.3 The Environment Agency’s Thames RBMP has set an objective of Moderate Status by 2027 for this water body, which is the current classification. As such, for the purpose of this WQA no upstream improvements were predicted when assessing the impact of future growth.

No deterioration – preventing class deterioration 3.6.4 No deterioration of WFD class has been predicted for any determinands downstream of the WwTW during the life of the Local Plan (i.e. the classification is the same both before and after housing growth, Figure 3.5). The results indicate that ammonia and BOD will remain at High Status downstream of the WwTWs, whilst phosphates will remain at Poor Status. It should be noted though that, the modelling did predict that BOD would deteriorate to the High Good boundary and as such the risk of deterioration is increased by the proposed housing growth. It is the role of the EA to monitor the quality of the rivers and assess them against WFD standards. If a deterioration from the baseline occurs they will investigate the reasons and work with relevant stakeholders to reverse any deterioration. As such the EA will assess the status of this waterbody as the plan progresses.

No deterioration – limiting in class deterioration to below the 10% threshold 3.6.5 The modelling of the future housing growth indicate that although there will be some deterioration downstream of Shamley Green WwTW it will be less than the Environment Agency’s aspirational 10% threshold. This indicates that water quality should not be a constraint to future housing.

Length of river impacted 3.6.6 From the point of discharge, there are no WFD class deteriorations for any determainand, and all impact modelled is below the 10% deterioration threshold. Therefore there is not considered to be any significant length of river deterioration.

Getting to Good (or 2027 objective) 3.6.7 When using the 2015 baseline and growth predictions, ammonia and BOD remained at High Status downstream of Shamley Green WwTW. As such no further assessments were undertaken, although it should be noted that continued compliance to High is dependent upon Farnham WwTW continuing to produce treated effluent to the same quality as noted in Appendix A.

3.6.8 In the baseline and WFD classifications phosphates have been assessed as being Moderate Status with a 2027 objective of Moderate (this is based on sample point PWER0006 and not the status of the waterbody downstream of the WwTW). Between this and the fact that no significant deterioration is predicted from the 2015 baseline, growth is not predicted to impact on the water body’s ability to achieve the 2027 objective. Although it should be noted the EA will reconsider all WFD objectives for the third RBMP to be published 2021.

3.6.9 The Environment Agency’s review of the permits indicated that a phosphate permit of 0.4 mg\l would be required to get the water body to Good Status prior to the proposed development (this is

as well as further improvements at Cranleigh WwTW). The permit for phosphate is less than the 0.5 mg\l technically feasible threshold set by the Environment Agency and Ofwat, although an assumption of achieving 0.1 mg\l is now being made by water companies. As such the water body downstream of Shamley Green WwTW could get to Good Status for phosphate irrespective of future housing growth. As this is the tightest permit possible housing growth is likely to have limited or no impact on the water bodies future ability to reach GES for the water quality determinands.

Downstream impacts beyond main water body 3.6.10 As no significant deterioration is predicted by the downstream of the WwTW no impacts are expected in the next downstream water body. As such no further assessments were undertaken.

Indicative permit calculations 3.6.11 As no deterioration of WFD class has been identified for any of the determinands and all deterioration was predicted to be less than 10% no new indicative permit limits were calculated.

Figure 3.5 Modelled changes in concentrations (in mg/l), of Phosphates (A - Average), BOD (B - 90%ile) and Ammonia (C - 90%ile) down the Cranleigh Waters from the upstream sample point PWER0006 to the end of the modelled Simcat reach, due to growth. Please note: A lack of deterioration can mean that the baseline is indistinguishable from the predicted impact line.

3.7 Haslemere Growth Area

3.7.1 The Haslemere growth area is served by Haslemere WwTW and as such could impact on the WFD water body South Wey (Haslemere to Bordon).

Upstream impacts 3.7.2 Haslemere WwTW is located near the upper reaches of this arm of the River Wey and there are no major WwTWs upstream of it. As such there are no predicted upstream changes predicted over the lifetime of the Local Plan which could influence proposed housing growth.

3.7.3 As the upstream data indicates that the determinands are already at Good or High Status no further improvements are expected so no changes were predicted for upstream quality as part of the Thames RBMP and 2027 objectives.

No deterioration – preventing class deterioration 3.7.4 No deterioration of WFD class has been predicted for any determinands downstream of the WwTW during the life of the Local Plan beyond that seen in the baseline (Figure 3.6). The results indicate that ammonia and BOD will remain at High Status, whilst phosphates will remain at Poor Status.

No deterioration – limiting in class deterioration to below the 10% threshold 3.7.5 The modelling results for future housing growth indicated that deterioration in water quality downstream of Haslemere WwTW will be less than the Environment Agency’s aspirational 10% threshold. This indicates that water quality should not be a constraint to future housing.

Length of river impacted 3.7.6 From the point of discharge, there are no WFD class deteriorations for any determainand, and all impact modelled is below the 10% deterioration threshold. Therefore there is not considered to be any significant length of river deterioration.

Getting to Good (or 2027 objective) 3.7.7 When using the 2015 baseline and growth predictions, ammonia and BOD remained at High Status respectively by sample point PWER0026. As such no further assessments were undertaken, although it should be noted that continued compliance to High is dependent upon Haslemere WwTW continuing to produce treated effluent to the same quality as noted in Appendix A.

3.7.8 In the baseline and WFD classifications phosphates have been assessed as being Poor Status with a 2027 objective of Good.

3.7.9 The Environment Agency’s review of the permits indicated that a phosphate permit of 0.9 mg\l would be required to get the water body to Good Status prior to the proposed development. As the predicted downstream deterioration for phosphate is less than 8% from the 2015 baseline, the proposed housing growth is not expected to have a significant impact on the permit required to get the water body too good by 2027.

Downstream impacts beyond main water body 3.7.10 As no significant deterioration is predicted by the downstream of the WwTW no impacts are expected in the next downstream water body. As such no further assessments were undertaken.

Indicative permit calculations 3.7.11 The modelling results indicated that no significant deterioration is predicted at the downstream sampling point due to housing growth. As such no new indicative permit limits were calculated.

Figure 3.6 Modelled changes in concentrations (in mg/l), of Phosphates (A - Average), BOD (B - 90%ile) and Ammonia (C - 90%ile) down the South Wey from the head of the reach to downstream sample point PWER0026, due to growth. Please note: A lack of deterioration can mean that the baseline is indistinguishable from the predicted impact line.

3.8 Chiddingfold Growth Area

3.8.1 The Chiddingfold growth area is served by Chiddingfold WwTW and as such could impact on the WFD water body Loxwood Stm-Hambledon Tributary.

3.8.2 As Chiddingfold WwTW is located within the upper reaches of the Arun catchment, the RQP tool was used to undertake the assessment at this WwTW. However, outputs from the RQP tool do not enable the same graphical representation of upstream and downstream influences as produced when using Simcat. However, although no graphical representation is in this report the same considerations and assessments of possible downstream impacts were undertaken and are included below.

Upstream impacts 3.8.3 No upstream data was available for the water quality assessments. As per guidance from the Environment Agency the mid class boundaries for water quality standards were used. In line with the 2015 RBMP classifications and 2027 objectives the High Status standard were used for ammonia and the Good Status standards were used for BOD and phosphate.

3.8.4 Chiddingfold WwTW is located near the upper reaches of the water body and there are no major WwTWs upstream of it. As such there are no predicted upstream changes expected over the lifetime of the Local Plan which could influence proposed housing growth.

No deterioration – preventing class deterioration 3.8.5 No deterioration of WFD class has been predicted for any determinands downstream of the WwTW during the life of the Local Plan from the modelled 2015 baseline.

No deterioration – limiting in class deterioration to less than 10% from baseline 3.8.6 The modelling results for future housing growth indicated that deterioration in water quality downstream of the WwTW will be less than the Environment Agency’s aspirational 10% threshold. This indicates that water quality should not be a constraint to future housing.

Getting to Good (or 2027 objective) 3.8.7 The WFD 2027 objective for phosphate is to reach Good Status by 2027 based on a current classifications noted in the 2015 RBMP. The baseline in this WQA represents a worst case scenario and as such was used for the water quality assessments.

3.8.8 An assessment of what quality of effluent would be needed prior to growth to get the waterbody to Good Ecological Status was undertaken. This indicated that permits of 0.1 mg\l (phosphates), 1.2 mg\l (ammonia) and 4 mg\l (BOD) would be required. The permit for phosphate is less than the 0.5 mg\l technically feasible threshold set by the Environment Agency and Ofwat, although an assumption of achieving 0.1 mg\l is now being made by water companies. As such the waterbody downstream of Chiddingfold WwTW could get to Good Status for phosphate irrespective of future housing growth. As this is the tightest permit possible housing growth is likely to have limited or no impact on the water bodies future ability to reach GES for the water quality determinands.

Downstream impacts beyond main water body 3.8.9 As no significant deterioration from the modelled 2015 baseline is predicted by the downstream of the WwTW no impacts are expected in the next downstream water body. As such no further assessments were undertaken.

Indicative permit calculations 3.8.10 The modelling results indicated that no significant deterioration from the modelled 2015 baseline is predicted due to housing growth. As such no new indicative permit limits were calculated.

Table 3.2 Chiddingfold WwTW RQP modelling results

Determinand WFD Class deterioration Baseline 2020 2026 2032 threshold Scenario Scenario Scenario

Quality D/S of 10% deterioration discharge in baseline directly D/S of discharge

Phosphate 0.5 (Poor/Bad boundary) 0.44 0.48 0.44 0.45 0.45 (mean, mg/l)

BOD (90%ile, 7.5 (Poor/Bad boundary) 6.35 6.99 6.36 6.40 6.40 mg/l)

Ammonia 2.5 (Poor/Bad boundary) 1.74 1.91 1.74 1.76 1.77 (90%ile, mg/l)

3.9 Dry Weather flow assessments

3.9.1 Each WwTW has a Dry Weather Flow permit which shows how much the WwTW can discharge on a daily basis to surface waters. The permit is set so as to protect the receiving waters and also helps with modelling indicative consents and providing an indication of whether the works is reaching it physical capacity for treating foul flows. In order to ensure that there was the physical capacity a high level assessment of the available capacity of all the WwTWs to accommodate the planned growth was undertaken.

3.9.2 Overall increases in DWF of between 2-89% were predicted for the WwTWs when looking at a worse case scenario for population size (e.g. 5 people per household). Shamley Green is predicted to have the smallest increase with Cranleigh having the largest increase. For most works however, the DWF flows by 2030 were predicted to remain below the permitted levels. This indicated that the WwTWs should have sufficient capacity to cope with the planned housing growth. This was except for Cranleigh which could potentially exceed its permit by 2020, indicating the potential need for upgrades (although see 3.9.5 for more information). As noted in section 3.2.14 a potential change to the phasing of housing feeding into Cranleigh WwTW, means that 265 homes could get built earlier. However, this did not impact on the DWF assessment for the WwTW.

3.9.3 Sensitivity testing (by applying a reduced single house occupancy of 2.5 people, rather than the 5 people considered in the main assessment) reduces the impact of the growth. With this assessment it was found that none of the WwTWs were predicted to breach their DWF permits by 2030. This indicates that all of them could have the physical capacity to cope with future housing growth.

3.9.4 The results were reviewed by Thames Water in order to ensure that the conclusions in this report were in line with any planning work already being undertaken. The conclusion of their review was:

 DWF flows used in this study for Cranleigh are greater than Thames Water’s own figures, even with the lower 2.5 housing occupancy. The main potential reasons are:

 Thames Waters per capita figures are lower than the Amec worst case scenario. This is due to this study using national guidance figures in order to ensure that there is future headroom capacity for more growth and to ensure the water environment is protected. Whereas Thames Water use figures based on their current working practices.

 Potential assumptions on infiltration being accounted for differently. This includes the potential for groundwater infiltration into the sewer network increasing flows beyond those expected from pure domestic sewage which could lead to high volumes of effluent being estimated.

 Thames Waters figures do not account for the Dunsfold Aerodrome site

3.9.5 This study indicates that under a worse case scenario Cranleigh WwTW might require a physical upgrade to cope with future housing growth as potential indicated in Table 3.3 (housing occupancy of 5 and assuming the flows from the Dunsfold Aerodrome site go to the WwTW). However, the review using a lower occupancy rate indicates that an upgrade might not be required and the current permit would be sufficient. For the purpose of this study the potential upgrade is noted and should be reviewed pending Thames Water’s further study of the options for the Dunsfold Aerodrome site. However, it should be noted that under all scenarios it is possible for housing growth to occur at the predicted rates.

Table 3.3 Dry Weather Flow assessments for the Waverley WwTWs using an occupancy rate of 5 people per house and the sensitivity testing of 2.5 people per house.

Consent 2015 Discharge volumes Assessment in relation to permit Occupancy WwTW limit DWF per house (m3/d) (Ml/d) 2020 2026 2032 2020 2026 2032

Cranleigh 5 4540 2930 3942.9 4628.9 5556.4 OK EXCEEDS EXCEEDS

Elstead 5 1591 1070 1121.9 1157.2 1170.1 OK OK OK

Farnham 5 13300 4200 5222.2 5376.1 5539.9 OK OK OK

Godalming 5 8749 6490 6973.5 7292.6 7475.5 OK OK OK

Shamley 5 2850 2320 2364.1 2372.4 2386.4 OK OK OK Green

Haslemere 5 4296 3840 4126.9 4180.5 4282.3 OK OK OK

Chiddingfold 5 639 510 515.6 572.9 579.0 OK OK OK

Cranleigh 2.5 4540 2930 3436.4 3779.4 4243.2 OK OK OK

Elstead 2.5 1591 1070 1096.0 1113.6 1120.0 OK OK OK

Farnham 2.5 13300 4200 4711.1 4788.0 4869.9 OK OK OK

Godalming 2.5 8749 6490 6731.7 6891.3 6982.7 OK OK OK

Shamley 2.5 2850 2320 2342.1 2346.2 2353.2 OK OK OK Green

Haslemere 2.5 4296 3840 3983.4 4010.3 4061.2 OK OK OK

Chiddingfold 2.5 639 510 512.8 541.4 544.5 OK OK OK

3.9.6 The Cranleigh Waters WFD water body contains both the Shamley Green WwTW and Cranleigh WwTW. Shamley Green WwTW is located approximately 5.5 km downstream of the Cranleigh WwTW, and it could be more difficult to prevent deterioration downstream of Shamley Green WwTW if Cranleigh WwTW also causes a deterioration in water quality. As indicated within Figure 3.5, potential deterioration in phosphate and BOD downstream of Cranleigh WwTW due to growth can potentially be seen all the way to just upstream of Shamley Green WwTW. However, indicative permit limits have been calculated for Cranleigh WwTW which would ensure that the waterbody further downstream (e.g. at Shamley Green WwTW) can remain at the current classifications even with an increase in discharge from Shamley Green.

3.9.7 There are no WwTWs upstream or downstream of Chiddingfold, Therefore there are no potential cumulative affects possible in this catchment.

4. Conclusions

4.1.1 The modelling in this WQA was undertaken to understand the potential future environmental impact on the receiving watercourses downstream of the growth areas and the seven WwTWs which serve them. Water quality modelling was undertaken to clarify potential changes to the existing WFD status of the watercourses from a 2015 baseline due to an increased discharge of treated sewage effluent. Future changes in water quality were also assessed against a 10% deterioration threshold and length of reach (or % of Waterbody) impacted aspirational objectives set by the Environment Agency in order to limit in class deterioration.

4.1.2 Housing numbers for the local plan growth to 2032 were considered in this WQA, which accounted for residential but not economic development growth proposals (Section 2). The phasing of the housing growth was modelled to six year cycles to bring it in line with the Environment Agency’s RBMPs.

4.1.3 The assessments for all the growth areas and their relevant WwTWs indicated that although there would be some deterioration in water quality for all determinands there would be no deterioration in WFD class by 2032. Therefore indicating that there is environmental capacity within the receiving watercourses to cope with the proposed housing numbers. However, the predicted BOD concentrations in the Cranleigh Waters did deteriorate to the High\Good Status boundary indicating an increased risk of deterioration due to growth.

4.1.4 An assessment undertaken by the Environment Agency for the 2015 RBMPs determined that it is technically infeasible to improve treatment for phosphates at WwTWs to achieve GES prior to housing growth, where the required permit is below 0.5mg/l. Based on this the modelled impacts of future housing growth are not the limiting factor that will prevent improvement to GES in the water bodies. However, should tighter permit standards become technically feasible in the future, the impacts of future housing growth would not preclude the delivery of improvement to GES through improved levels of treatment. A national water company led study, to be published in 2017, is reviewing what permits limits for phosphates will be technically feasible in the future. Until this study is complete the water bodies noted in this WQA that require a phosphate permit less than 0.5mg/l, cannot reach GES, irrespective of future growth, as a tighter permit would be required to meet this objective. This is a national issue affecting all WwTW which have a significant impact on UK rivers. What is technically feasible, and targets for water bodies, is likely to be reviewed after March 2017 when the Environment Agency and water companies start planning for the 2021-2027 river basin management plans. This is with the exception of Haslemere WwTW which only requires a phosphate permit standard of 0.9 mg\l for the waterbody to reach Good Ecological Status which is possible even after housing growth.

4.1.5 The assessments for all of the WwTWs indicated that deterioration in water quality would not be significant (i.e. no WFD class deteriorations and below the EA’s 10% threshold). This was except for downstream of Cranleigh and Farnham WwTWs where deterioration exceeded the 10% threshold for ammonia and phosphates. Calculations of indicative permit standards for Cranleigh WwTW and Farnham WwTW to prevent this deterioration were undertaken which showed that there are technically achievable permit standards that could prevent significant deterioration in the receiving watercourses.

4.1.6 The high level capacity assessment indicated that Cranleigh WwTW could require an upgrade in order to support future housing growth under a worse case scenario. Since the original assessments in this study were undertaken Thames Water have confirmed that a study has been commissioned for completion in summer 2017. The study will confirm options for the Dunsfold Aerodrome site and therefore will indicate whether Cranleigh WwTW is likely to require an upgrade.

5. References

Capita, 2016. Waverley Borough Council High Level Water Cycle Study. Available at https://www.waverley.gov.uk.

Environment Agency, 2014. Water Cycle Study Guidance. Available at Http://planningguidance.communities.gov.uk.

Appendix A Input data and modelling outputs (Excel workbook)

Appendix B WFD water body and growth area maps

23 June 2017 Doc Ref. ERea008i3R