Tandridge District Council Water Cycle Study – Phase 2 Outline Study

June 2018 www.jbaconsulting.com

Tandridge District Council

Council Offices Station Road East Oxted Surrey RH8 0BT

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JBA Project Manager Alistair Clark 8a Castle Street Wallingford Oxfordshire OX10 8DL

Revision history Revision Ref/Date Amendments Issued to V1.0 Draft Report Mark Bristow 04/06/2018 V2.0 Amendments in response to feedback from TDC Mark Bristow 28/06/2018 and addition of Water Quality Assessment.

Contract This report describes work commissioned by Tandridge District Council in February 2018. Tandridge District Council’s representative for the contract was Mark Bristow. Alistair Clark and Richard Pardoe of JBA Consulting carried out this work.

Prepared by ...... Richard Pardoe MSc MEng

Analyst

...... Nathan Chapman BSc

Assistant Analyst

Reviewed by ...... Alistair Clark BSc MSc

Senior Analyst

Purpose This document has been prepared as a Final Report for Tandridge District Council. JBA Consulting accepts no responsibility or liability for any use that is made of this document other than by the Client for the purposes for which it was originally commissioned and prepared. JBA Consulting has no liability regarding the use of this report except to Tandridge District Council.

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Acknowledgements JBA Consulting would like to thank Mark Bristow of Tandridge District Council, Charlotte Mayall of Southern Water, Alison Murphy of Sutton and East Surrey Water and Nicky McHugh of Thames Water for their assistance in preparing this report.

Carbon footprint A printed copy of the main text in this document will result in a carbon footprint of 363g if 100% post-consumer recycled paper is used and 462g if primary-source paper is used. These figures assume the report is printed in black and white on A4 paper and in duplex. JBA is aiming to reduce its per capita carbon emissions.

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Executive summary In March 2018, JBA Consulting was commissioned by Tandridge District Council to undertake a Water Cycle Study (WCS). This study assesses the potential issues relating to future development within the Tandridge district and the impacts on water supply, wastewater collection and waste water treatment. The Water Cycle Study is required to assess the constraints and requirements that will arise from potential growth on the water infrastructure. New homes require the provision of clean water, safe disposal of wastewater and protection from flooding. The allocation of large numbers of new homes in certain locations may result in the capacity of existing available infrastructure being exceeded, a situation that could potentially cause service failures to water and wastewater customers, adverse impacts to the environment, or high costs for the upgrade of water and wastewater assets being passed on to the bill payers. In addition to increased housing demand, future climate change presents further challenges and pressure on the existing water infrastructure network, including an increased intensity of rainfall events and a higher frequency of drought events. Sustainable planning for water must now take this into account. The water cycle can be seen in the figure below and shows how the natural and man-made processes and systems interact to collect, store or transport water in the environment. The Water Cycle

Source: Environment Agency – Water Cycle Study Guidance

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This study will assist the council to select and develop sustainable development allocations where there is minimal impact on the environment, water quality, water resources, infrastructure, and flood risk. This has been achieved by identifying areas where there may be conflict between any proposed development and the requirements of the environment and by recommending solutions to these conflicts. The phase 1 scoping study concluded that the following assessments were required as part of the outline study:

• Water resources • Water supply infrastructure • Wastewater collection infrastructure • Wastewater treatment capacity • Water quality • Flood risk from additional foul flow • Odour from WwTW • Environmental opportunities and constraints

The purpose of this phase 2 outline study is to build on the growth forecast developed in the phase 1 scoping study and carry out the assessments listed above, providing part of the evidence base for the Tandridge Local Plan.

Water resources The phase 1 scoping study concluded that further assessment of water resources was required in phase 2 to understand the difference between the forecast in the water resource management plan (WRMP) and the objectively assessed need (OAN) for Tandridge, and to take a regional view of growth across the water resource zone (WRZ) to ensure growth is adequately provided for in the WRMP. It was shown that growth within Tandridge is broadly in line with the average across the WRZ. Sutton and East Surrey Water were asked to comment on the use of the econometric forecast in their WRMP and confirmed that it was chosen as it provides the best fit to historic growth data. They carry out uncertainty analysis that includes higher than predicted growth, and the forecast is reassessed annually with a complete revision every five years. Based on the comments from Sutton and East Surrey Water, and the evidence presented in their WRMP that there is a water resource surplus predicted until 2047, there is sufficient time to adapt the term plan to include emerging trends in population and no further assessment of water resources is required in a phase three detailed study.

Water supply infrastructure SESW carried out a modelling study of the impact of the development sites on the water supply network. This concluded that eight of the proposed sites WILL require network reinforcements, and a further fourteen MAY require reinforcement. There is capacity at the remaining sites to serve the proposed growth. No significant constraints to the provision of these upgrades have been identified, however extensive reinforcement will be required at the South Godstone garden community site including a new main to connect to the Blindley Heath trunk main.

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Early developer engagement with SESW is essential to ensure that, where necessary, network reinforcement is delivered prior to developments becoming occupied. No further assessment is required in a phase 3 WCS.

Wastewater collection infrastructure Southern Water and Thames Water provided a site by site RAG assessment of wastewater infrastructure within their catchments. The study concluded that upgrades to the sewerage network were required in order to serve the potential garden community sites, and five other potential development sites. No significant constraints to provision of this infrastructure have been identified. Sewerage Undertakers have a duty under Section 94 of the Water Industry Act 1991 to provide sewerage and treat wastewater arising from new domestic development. Except where strategic upgrades are required to serve very large or multiple developments, infrastructure upgrades are usually only implemented following an application for a connection, adoption, or requisition from a developer. Early developer engagement with water companies is therefore essential to ensure that sewerage capacity can be provided without delaying development. No further assessment of wastewater sewerage network capacity is required as part of a phase 3 detailed study.

Wastewater treatment capacity A headroom assessment was carried out by JBA Consulting on the WwTW likely to serve growth within Tandridge, and a RAG assessment with comments was provided by Southern Water and Thames Water on their infrastructure. Nine wastewater treatment works (WwTW) are likely to serve growth within Tandridge. Beddington and Longreach are very large works to the north of Tandridge, and planned growth within Tandridge represents a negligible increase wastewater flows. No further assessment was made of these works, and Thames Water confirmed that there is capacity to receive additional flow. Edenbridge is predicted to receive only a small increase in flow from two committed sites and is therefore not assessed. Capacity is available at Felbridge and Godstone WwTW to serve proposed growth throughout the Local Plan period. Burstow WwTW is currently close to its permit limit and additional flow will cause its permit to be exceeded within the next five years. A new permit, or upgrades to this WwTW are required. Lingfield WwTW has the capacity to accept planned growth up to AMP10 (2035-2040) in the scenario where one garden community site is provided (South Godstone). In the unlikely event of two garden community sites being provided in this catchment, its permit would be exceeded in AMP9 (2030-2035). Oxted is currently exceeding its DWF permit due to infiltration and it is intended that an infiltration scheme is included in the draft PR19 plan. This should enable Southern Water to meet the forecast growth in the Oxted catchment in 2020-2025. Any development in this catchment must be carefully phased with upgrades to this works, and early engagement between the developer and Southern Water is essential. Reigate WwTW is currently close to its permit. Much of the growth in this catchment is from outside Tandridge and is likely to be accommodated through a planned capacity upgrade. Should the Redhill Aerodrome garden community site be adopted, a further upgrade will be required to the WwTW at a potential cost of £20M. Clarity is therefore required at an early stage to avoid sunk cost in Thames Water’s upgrade plans. Further study of the schedule of upgrades at Burstow, Lingfield, Oxted and Reigate WwTW is recommended as part of a phase 3 detailed study.

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Water quality • Proposed levels of growth to be treated by Burstow, Felbridge and Oxted WwTW's would not lead to a deterioration, either of 10% or of class in any of the measures determinands. Existing treatment permits are therefore suitable for these works. • Increased effluent discharges due to growth at Lingfield WwTW is predicted to lead to deterioration of 10% or more, and/or of class. In all cases, deterioration could be prevented by a tightening of permits and possible infrastructure improvements for effluent to be treated at technically achievable limit (TAL). • At Godstone WwTW, Ammonia is predicted to deteriorate by 10% or more and Phosphate, already classed as Bad, deteriorating by more than 3%. In both cases, deterioration can be limited through infrastructure improvements and tighter permit limits. • At Godstone WwTW, assuming upstream water quality meets Good status and effluent is treated at TAL, BOD is still predicted to deteriorate from Good to Moderate status. The downstream sampling point WQ TH-E0000902, BOD class is predicted to remain at Good status, however, BOD has not been classified within the WFD 2016 classification for the Gibbs Brook therefore, it cannot be assessed in regard to class deterioration. • None of the receiving watercourses currently meet Good class for Phosphorous downstream of the WwTW's investigated. In all cases current technology to treat Phosphorous is limited. Assuming that upstream water quality can be improved to meet Good, then Good class could be met downstream of Felbridge, Godstone, Lingfield and Oxted WwTWs. This is achievable through upgrading treatment technologies so that effluent is treated to the technically achievable limit and would not be compromised in the future by the proposed scale of development. At Burstow WwTW, Good class could not be met in the present day or through treatment at TAL. The Burstow Stream is currently Poor with the objective to meet Moderate by 2027. • At Reigate (Earlswood) WwTW, based on SIMCAT results, all determinands currently are classed as 'Bad'. There is however, no deterioration greater than 3% when tested with future growth. Through treatment at TAL, both BOD and Phosphate can be improved to meet Good class, with Ammonia improving to Moderate class. The Earlswood Brook has not been classified within WFD waterbody classifications therefore, the Mole (Horley to Hersham) has been assigned for the reach. The reach currently meets Moderate ecological status, with Ammonia meeting Good and both BOD and Phosphate meeting Poor. • An analysis of the potential impacts of reduced river flows (10% reduction in mean flow, and 20% Q95) as a result of climate change indicate that there is a significant risk of deterioration of water quality. It is expected that future River Basin Management Plans will investigate this risk further and consider how it can be mitigated. Wherever possible, plans should promote "no-regrets" decisions which enhance the resilience of river systems to climate change impacts, for example by promoting Catchment Based Approaches. The planned growth within Tandridge District and its neighbouring authorities can be accommodated without causing a deterioration in water quality for sanitary determinands and nutrients, so long as timely interventions to prevent deterioration are implemented by Thames Water, Southern Water and the Environment Agency. No additional assessment of water quality is recommended in a Phase 3 WCS.

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Flood risk from additional foul flow A detailed assessment of flood risk can be found in the Tandridge District Council’s Level 1 Strategic Flood Risk Assessment (December 2017). The impact of increased effluent flows due to planned growth is not predicted to have a significant impact on flood risk in any of the receiving watercourses. No further assessment is recommended in a phase 3 WCS.

Odour from WwTW Three sites are close enough to a WwTW that a further odour assessment is recommended as part of the planning process. The cost for this should be met by the developer. No further assessment of odour is recommended in the phase 3 detailed study. Any future assessment should be carried out as part of the planning process.

Environmental constraints A number of SSSIs exist within Tandridge, and a hydrological pathway exists to a SAC (Mole Gap to Reigate Escarpment) to the north west. WwTWs are considered to be point sources of pollution, but the water quality study has showed that the impact of additional discharge from WwTW can be mitigated by upgrades / improvements to treatments works and tightened permits. The impact on sites with environmental designations downstream is therefore likely to be minimal. Development sites within Tandridge could be sources of diffuse pollution from surface runoff, with some of the development sites having a direct surface water pathway to a SSSI. Runoff in these sites should be managed through implementation of a SuDS scheme with a focus on treating the water quality of surface runoff. The cumulative impact of all development within a catchment should be considered, and incorporation of SuDS encouraged on sites even where there is no direct pathway to a SSSI. No further assessment of environmental constraints and opportunities is recommended in a phase 3 detailed study.

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Contents 1 Introduction 14 1.1 Terms of Reference 14 1.2 The Water Cycle 14 1.3 Impacts of Development on the Water Cycle 15 1.4 Objectives 15 1.5 Study Area 15 1.6 Record of Engagement 16 1.6.1 Introduction 16 1.6.2 Outline Study Engagement 16 2 Future Growth in Tandridge 17 2.1 Tandridge District 17 2.2 Growth in Tandridge 18 2.3 Components of development forecast 18 2.3.1 Garden community sites 18 2.3.2 Summary 19 2.4 Growth in Neighbouring LPAs 19 3 Legislative and Policy Framework 20 3.1 Introduction 20 3.2 Changes since Phase 1 Scoping study 20 4 Water Resources and Water Supply 21 4.1 Introduction 21 4.1.1 Surface Waters 21 4.2 Availability of Water Resources 22 4.2.1 Conclusions of phase 1 scoping study 22 4.2.2 Water Resource Assessment: Water Resource Management Plans 22 4.2.3 Population and Household Growth 22 4.2.4 Sutton and East Surrey Water assessment 25 4.2.5 Conclusions 26 4.3 Water Supply Infrastructure 27 4.3.1 Introduction 27 4.3.2 Methodology 27 4.3.3 Results 28 4.3.4 Conclusions 29 4.3.5 Recommendations 30 5 Wastewater collection 31 5.1 Sewerage Undertaker for Tandridge 31 5.2 Sewerage System Capacity Assessment 31 5.3 Methodology 32 5.3.1 Data Collection 32 5.4 Results 33 5.5 Conclusions 34 5.6 Recommendations 35 6 Wastewater Treatment 36 6.1 Wastewater Treatment Works in Tandridge 36 6.2 Wastewater Treatment Works Flow Permit Assessment 37 6.2.1 Introduction 37 6.3 Methodology 39

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6.4 Results 39 6.4.1 Beddington WwTW 39 6.4.2 Burstow WwTW 39 6.4.3 Edenbridge WwTW 40 6.4.4 Felbridge WwTW 40 6.4.5 Godstone WwTW 41 6.4.6 Lingfield WwTW 42 6.4.7 Longreach WwTW 43 6.4.8 Oxted WwTW 43 6.4.9 Reigate WwTW 44 6.5 Impact of higher than expected growth 45 6.6 Conclusions 45 6.6.1 Recommendations 46 7 Water quality assessment 47 7.1 Introduction 47 7.2 Methodology 47 7.2.1 Data Collection 49 7.3 Results 50 7.4 Priority substances and other EU-level dangerous substances 52 7.5 Recommendations 53 8 Flood Risk Management 54 8.1 Assessment of Additional Flood Risk from Increased WwTW Discharges 54 8.1.1 Introduction 54 8.2 Methodology 54 8.3 Results 54 8.4 Impact of higher than expected growth 55 8.5 Conclusions 55 8.6 Recommendations 55 9 Odour Assessment 56 9.1 Introduction 56 9.2 Methodology 56 9.2.1 Data Collection 56 9.2.2 Results 56 9.3 Conclusions 57 10 Environmental Opportunities and Constraints 58 10.1 Introduction 58 10.2 Sites with Environmental Designation 58 10.2.1 Sites protected by European designations 58 10.2.2 Sites of Special Scientific Interest 60 10.3 Point source pollution 61 10.4 Diffuse sources of water pollution 61 10.5 Surface Water Drainage and SuDS 65 10.5.1 Use of SuDS in Water Quality Management 66 10.5.2 Additional benefits 68 10.6 Conclusions 69 10.7 Recommendations 69 11 Climate change Impact Assessment 71 11.1 Approach 71 11.1.1 Wastewater collection and treatment 71 11.1.2 Water quality 71 11.2 Results summary 71

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11.3 Conclusions and Recommendations 72 12 Summary and overall conclusions 74 12.1 Summary of phase 2 outline study 74 12.2 Recommendations 77 12.3 Requirement for phase 3 detailed study 83 12.3.1 A realistic approach 83 12.3.2 Strategic schemes 83 12.3.3 Safeguarding strategic sites 83

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List of Figures Figure 1.1 The Water Cycle 15 Figure 2.1 Map of the water cycle study area and potential development sites 17 Figure 4.1 Watercourses within the study area 21 Figure 4.2 Local authorities within Sutton and East Surrey water resource zone 24 Figure 6.1 WwTWs serving Tandridge 36 Figure 6.2 Overview of typical combined sewerage system and WwTW discharges 37 Figure 6.3 Headroom assessment for Burstow WwTW 40 Figure 6.4 Headroom assessment for Felbridge WwTW 41 Figure 6.5 Headroom assessment for Godstone WwTW 41 Figure 6.6 Headroom assessment for Lingfield WwTW 42 Figure 6.7 Headroom assessment for Oxted WwTW 43 Figure 6.8 Headroom assessment for Reigate WwTW 44 Figure 7.1 Water quality impact assessment following EA Thames West guidance 48 Figure 7.3: WFD Cycle 2 Water Quality Classifications of Watercourses in Tandridge District 49 Figure 10.1 Sites with environmental designations within or close to Tandridge 59 Figure 10.2 SSSIs within Tandridge in relation to potential development sites 60

List of Tables Table 2.1 Indicative figures for housing and employment in garden community sites 19 Table 2.2 Summary of housing development 19 Table 4.1 Summary of growth forecasts 23 Table 4.2 Growth within water resource zone by local authority 25 Table 4.3 Summary of RAG score for water resources 26 Table 4.4 Summary of RAG score by site 28 Table 5.1 Southern Water and Thames Water RAG assessment of sewerage network capacity 33 Table 5.2 Wastewater collection system assessment recommendations 35 Table 6.1 Indicative growth served by each WwTW (realistic scenario) 38 Table 8.1 Summary of DWF increase as a percentage of Q30 and Q100 peak flow 55 Table 8.2 Summary of Flood Risk Management Recommendations 55 Table 10.1 WwTW relative to sites with environmental designations 61 Table 10.2 Potential sources of diffuse pollution and receptors 62 Table 11.1 Climate change pressures scoring matrix 71 Table 11.2 Scoring of climate change consequences for the Water cycle Study 72 Table 11.3 Climate change actions 73 Table 12.1 Summary of phase 2 outline study conclusions 74

Abbreviations ALS Abstraction Licensing Strategy AMP Asset Management Plan AMR Automatic Meter Reading AONB Area of Outstanding Natural Beauty AP Assessment Point ASNW Ancient Semi-Natural Woodland BERR Department for Business Enterprise and Regulatory Reform BIDS Business, Industrial, Distribution and Storage BOD Biochemical Oxygen Demand

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BREEAM Building Research Establishment Environmental Assessment Methodology CAMS Catchment Abstraction Management Strategies CAPEX Capital Expenditure CED Common End Date CFMP Catchment Flood Management Plan CfSH Code for Sustainable Homes CSO Combined Sewer Overflow DCLG Department of Communities and Local Government DWF Dry Weather Flow DWI Drinking Water Inspectorate DYAA Dry Year Annual Average DYCP Dry Year Critical Period EA Environment Agency EC European Community ECA European Communities Act EDNA Economic Development Needs Assessment EFI Ecological Flow Indicator EP Environmental Permit EU European Union FEH Flood Estimation Handbook FFT Flow to Full Treatment FWMA Flood and Water Management Act FZ Flood Zone GES Good Ecological Status GIS Geographic Information Systems HOF Hands-Off Flow HOL Hands-off Level IDB Internal Drainage Board IDP Infrastructure Delivery Plan JBA Jeremy Benn Associates LLFA Lead Local Flood Authority LPA Local Planning Authority l/p/d Litres per person per day Ml/d Mega (Million) litres per day NE Natural England

NH4 Ammonia NPPF National Planning Policy Framework NYAA Normal Year Average Annual OAN Objectively Assessed Need OfWAT Water Service Regulation Authority ONS Office of National Statistics OPEX Operational Expenditure OS Ordnance Survey

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P Phosphorous PDL Previously Developed Land PE Population Equivalent p/h Person per house PPS Planning Policy Statement RAG Red / Amber / Green assessment RBD River Basin District RBMP River Basin Management Plan ReFH Revitalised Flood Hydrograph RNAG Reason for Not Achieving Good (Status) RQP River Quality Planning tool RZ Resource Zone SA Sustainability Appraisals SAC Special Area of Conservation SBP Strategic Business Plan SEA Strategic Environmental Assessment SEPA Scottish Environmental Protection Agency SESW Sutton and East Surrey Water SFRA Strategic Flood Risk Assessment SHELAA Strategic Housing and Economic Land Availability Assessment SHMA Strategic Housing Market Assessment SPA Special Protection Area SPD Supplementary Planning Document SPZ Source Protection Zone SS Suspended Solids SSSI Site of Special Scientific Interest SU Sewerage Undertaker SW Southern Water SuDS Sustainable Drainage Systems SWMP Surface Water Management Plan TCAMS Thames Catchment Abstraction Management Strategy TDC Tandridge District Council TW Thames Water UWWTD Urban Waste Water Treatment Directive WaSC Water and Sewerage Company WCS Water Cycle Study WFD Water Framework Directive WRMP Water Resource Management Plan WRZ Water Resource Zone WQA Water Quality Assessment WSZ Water Supply Zone WTW Water Treatment Works WwTW Wastewater Treatment Works

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1 Introduction

1.1 Terms of Reference JBA Consulting was commissioned by Tandridge District Council to undertake a Water Cycle Study (WCS) for Tandridge district to inform the Local Plan. The purpose of the WCS along with the Strategic Flood Risk Assessment (SFRA) is to form part of a comprehensive and robust evidence base for the Local Plan which will set out a vision and framework for development in the district up to 2033 and will be used to inform decisions on the location of future development. Unmitigated future development and climate change can adversely affect the environment and water infrastructure capability. A WCS will provide the required evidence, together with an agreed strategy to ensure that planned growth occurs within environmental constraints, with the appropriate infrastructure in place in a timely manner so that planned allocations are deliverable. A phase one scoping study was completed in May 2018, and established that further assessment was required in the following areas:

1.2 The Water Cycle National Planning Policy Framework Practice Guidance on Water Supply, Wastewater and Water Quality1 describes a water cycle study as: "a voluntary study that helps organisations work together to plan for sustainable growth. It uses water and planning evidence and the expertise of partners to understand environmental and infrastructure capacity. It can identify joined up and cost-effective solutions, that are resilient to climate change for the lifetime of the development. The study provides evidence for Local Plans and sustainability appraisals and is ideally done at an early stage of plan-making. Local authorities (or groups of local authorities) usually lead water cycle studies, as a chief aim is to provide evidence for sound Local Plans but other partners often include the Environment Agency and water companies." The Environment Agency's guidance on WCS2 recommends a phased approach: • Phase 1: Scoping study, focussing on formation of a steering group, identifying issues for consideration and the need for an outline study. • Phase 2: Outline study, to identify environmental constraints, infrastructure constraints, a sustainability assessment and consideration of whether a detailed study is required.

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1 Planning Practice Guidance: Water supply, wastewater and water quality, Department for Communities and Local Government (2014). Accessed online at: http://planningguidance.planningportal.gov.uk/blog/guidance/ on: 09/03/2018 2 Water Cycle Study Guidance, Environment Agency (2009). Accessed online at: http://webarchive.nationalarchives.gov.uk/20140328084622/http://cdn.environment-agency.gov.uk/geho0109bpff-e-e.pdf on: 09/03/2018 2018s0255 TDC WCS Phase 2 Outline v2.0 14

• Phase 3: Detailed study, to identify infrastructure requirements, when they are required, how they will be funded and implemented and an overall assessment of the sustainability of proposed infrastructure.

Figure 1.1 below shows the main elements that compromise the Water Cycle and shows how the natural and man-made processes and systems interact to collect, store or transport water in the environment.

Figure 1.1 The Water Cycle

1.3 Impacts of Development on the Water Cycle New homes require the provision of clean water, safe disposal of wastewater and protection from flooding. It is possible that allocating large numbers of new homes at some locations may result in the capacity of the existing available infrastructure being exceeded. This situation could potentially lead to service failures to water and wastewater customers, have adverse impacts on the environment or cause the high cost of upgrading water and wastewater assets being passed on to bill payers. Climate change presents further challenges such as increased intensity and frequency of rainfall and a higher frequency of drought events that can be expected to put greater pressure on the existing infrastructure.

1.4 Objectives As a WCS is not a statutory instrument, Local Planning Authorities are advised to prioritise the different stages of the WCS to integrate with their Local Plan programme. This outline report is written as an interim report to support the development of the Local Plan and to identify whether a detailed WCS is required. This study will apply the growth forecast developed in phase 1 and assess its impact on water and wastewater infrastructure and the environment.

1.5 Study Area This WCS outline report has been written for Tandridge District Council. This Local Authority area covers 248km2 and includes the towns of Caterham, Godstone, Lingfield, and Oxted and has a population of approximately 87,000. The area is located within the River Mole, and River Medway catchments to the west and east respectively. The area north of the North Downs is in the catchment of the Caterham Bourne. Water supply services for Tandridge are provided by Sutton and East Surrey Water, and wastewater serves are split between Thames Water and Southern Water. 2018s0255 TDC WCS Phase 2 Outline v2.0 15

1.6 Record of Engagement

1.6.1 Introduction Preparation of a WCS requires significant engagement with stakeholders, both within the Local Planning Authority, with water and wastewater utilities, with the environment agency, and where there may be cross-boundary issues, with neighbouring local authorities. This section forms a record of engagement for the WCS.

1.6.2 Outline Study Engagement The preparation of the scoping study was supported by the following engagement:

Engaged TDC Parties Southern Water Sutton and East Surrey Water Thames Water Details Site by site assessment of water infrastructure, and WwTW. Follow-up discussions to clarify scoring.

Engaged Natural England Parties Details Clarification of Impact Risk Zones (email exchange)

Engaged Environment Agency Parties Details Supply of water quality data and SIMCAT models

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2 Future Growth in Tandridge

2.1 Tandridge District Figure 2.1 shows the location of potential development sites within the TDC boundary.

Figure 2.1 Map of the water cycle study area and potential development sites

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2.2 Growth in Tandridge The Strategic Housing Market Assessment (SHMA)3 carried out in 2015 provided a detailed analysis of population demographics and the housing market within Tandridge and resulted in the definition of the Objectively Assessed Need (OAN)4 for the district. This assessment was based on the Department for Communities and Local Government (DCLG) 2012-based household projections, updated with the 2014 mid-year estimates released in June 2015 and the international migration statistics for the year up to March 2015. The conclusion of the assessment was that a total of 9,440 houses were required during the plan period (2013-2033) or an average of 470 / year.

2.3 Components of development forecast For the purpose of the assessments within the WCS, a baseline growth forecast is defined for development in Tandridge over the Local Plan period. This forecast is made up of the following components: • Housing and Economic Land Availability Assessment (HELAA) • Garden community sites • Commitments (development sites already in the planning system, but not yet built) • Windfall • Development from outside the Tandridge boundary, but served by infrastructure within or shared with Tandridge (this forecast has not yet been received from neighbouring LPAs so is not included in this report, however this will be documented in the Phase 1 report and included in future assessments) These have been collated into an overall forecast summarised in Table 2.2 below. The full assessment of growth can be found in the Phase 1 Scoping study.

2.3.1 Garden community sites The Spatial Approaches Topic Paper (2015)5 presented the concept of a new or extended settlement as a route to deliver the growth required within the district. Three broad locations are considered within the WCS: • Redhill Aerodrome • South Godstone • Blindley Heath Two scenarios for Garden community sites will be analysed, the first where one garden community site is adopted, South Godstone has been chosen for this purpose. The second tests the unlikely event of the Council being expected to provide three garden community sites representing the most extreme case for water demand.

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3 Strategic Housing Market Assessment, TDC (2015). Accessed online at: https://www.tandridge.gov.uk/Portals/0/Documents/Planning%20and%20building/Planning%20strategies%20and%2 0policies/Local%20plan/Evidence%20base%20and%20technical%20studies/Strategic-Housing-Market-Assessment- 2015-Front-Page.pdf on: 26/02/2018 4 The Objectively Assessed Housing Needs of Tandridge, NMSS (2015). Accessed online at: https://www.tandridge.gov.uk/Portals/0/Documents/Planning%20and%20building/Planning%20strategies%20and%2 0policies/Local%20plan/Evidence%20base%20and%20technical%20studies/Strategic-Housing-Market-Assessment- 2015-Tandridge-Objectively.pdf on: 26/02/2018 5 Spatial Approaches Topic Paper, TDC (2015). Accessed online at: https://www.tandridge.gov.uk/Portals/0/Documents/Planning%20and%20building/Planning%20strategies%20and%20policies/Local% 20plan/Evidence%20base%20and%20technical%20studies/Spatial-Approaches-Topic-Paper.pdf on: 27/02/2018 2018s0255 TDC WCS Phase 2 Outline v2.0 18

Table 2.1 Indicative figures for housing and employment in garden community sites

Broad Location Housing Employment (no. units of employees) Redhill Aerodrome 7000 2822 South Godstone 4000 2615 Blindley Heath 3000 2619

Consideration of these broad locations is at a very early stage; the estimates of housing units and employment land are indicative only. It is therefore prudent to consider the effect on water infrastructure if the size of the development was increased, or the mix of housing and employment land was changed such that the water demand increased. A further scenario will therefore be considered where the garden community site water and wastewater demand are increased by 10%.

2.3.2 Summary Table 2.2 summarises the development within Tandridge. The most realistic scenario includes just one garden community site (South Godstone has been chosen for this analysis). Table 2.2 Summary of housing development

Housing units (All Housing units sites) (Realistic scenario) Completions 2013 to 1,518 1,518 2017 Commitments 2017/2018 1,115 1,115

HELAA 1,806 1,806

Garden community 14,000 4,000

Windfall 2013-2033 540 540

Total 18,979 8,979 Objectively Assessed 9,440 9,440 Need

2.4 Growth in Neighbouring LPAs In the phase 1 scoping study, neighbouring authorities were approached under a duty to cooperate request to understand how growth in neighbouring authorities may impact water infrastructure within or shared with Tandridge. This allows the full picture of growth to be taken into account when carrying out flow capacity and water quality assessments. Responses to the DTC request are documented in the phase 1 scoping study and have been included in all the assessments within the phase 2 outline study.

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3 Legislative and Policy Framework

3.1 Introduction Several national, regional and local policies must be considered by the LPAs, water companies, and developers during the planning stage. A summary of these policies can be found in section 3 of the Phase 1 Scoping study.

3.2 Changes since Phase 1 Scoping study No major changes to relevant legislation and policy have been made since publication of the phase 1 scoping study. It should be noted that consultation on the draft revised National Planning Policy Framework (NPPF) closed in May 2018 and publication of the updated framework is expected in late summer 2018. The draft update to the NPPF included limited changes that would directly impact the water cycle study, however it may need to be revisited should significant changes be made to the NPPF when published.

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4 Water Resources and Water Supply

4.1 Introduction

4.1.1 Surface Waters Figure 4.1 shows the main watercourses within the study area, which is divided between two catchments, the Mole to the west and the Medway to the east.

Figure 4.1 Watercourses within the study area

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4.2 Availability of Water Resources

4.2.1 Conclusions of phase 1 scoping study The phase 1 scoping study concluded that: • Tandridge lies in an area classed by the EA as being under “serious water stress”. Water resources are limited in this region, although Sutton and East Surrey’s WRMP shows a supply surplus until 2047. • Four Abstraction Licencing Strategies (ALS) apply to Tandridge and impose restrictions on water abstraction from both groundwater and surface water sources. Surface water abstractions are frequently limited by restrictions in the Thames Catchment Abstraction Management (CAMs) region which takes precedence over the Mole and London ALS. • The econometric forecast has been used in SESW’s WRMP. This forecasts lower growth than would occur if the OAN is delivered. SESW will be asked to comment on this as part of the phase 2 outline study. A regional view, including forecasts from all the authorities within the water resource zone also needs to be taken in account in order to ensure that growth is adequately provided for in the WRMP. • A water supply-demand deficit is forecast by 2047 • A PCC of 122 l/p/d and occupancy rate of 2.41 will be used in the water cycle study • Opportunities should be taken to further reduce water consumption by adopting the higher standard 110l/p/d for residential developments and adopting the BREEAM standard to reduce consumption in new non-residential buildings. A detailed review of water resources can be found in section 4 of the phase 1 scoping study.

4.2.2 Water Resource Assessment: Water Resource Management Plans When new development within a Local Planning Authority is being planned, it is important to ensure that there are sufficient water resources in the area to cover the increase in demand without risk of shortages in the future or during periods of high demand, and without causing a negative impact on the waterbodies from which water is abstracted. The aim of this assessment was to compare the future additional demand as a result of development proposed within the emerging Local Plan, with the demand allowed for by Sutton and East Surrey Water in their Water Resource Management Plan. At the time of writing the Draft 2019 WRMP6 was undergoing a public consultation, due to end 25 May 2018. This is the version discussed below, however it should be noted that this is subject to change pending the results of the consultation.

4.2.3 Population and Household Growth Experian were commissioned by SESW to provide population and household growth forecasts as part of a project including other water companies in the south east. Four forecasts were prepared using different methods (Trend based – from ONS statistics, Plan based – from LPA plans, Econometric – taking into account economic pressures, and Hybrid – a combination of plan based and econometric). The econometric forecast was used to project household demand in the WRMP. The forecast extrapolates to the end of SESW’s planning period (2080) and shows a 70% increase in households and a 41% increase in population (with declining occupancy rates predicted). For the local plan period, 17% growth was predicted over the whole of the water resource zone. The household growth forecast used is therefore less than will occur if the OAN is delivered (Table 4.1).

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6 Draft Water Resources Management Plan 2019, Sutton and East Surrey Water (2018). Accessed online at: http://www.waterplc.com/userfiles/file/DraftWRMP19mainreport.pdf on: 10/04/2018 2018s0255 TDC WCS Phase 2 Outline v2.0 22

Table 4.1 Summary of growth forecasts

Forecast Percentage growth from base years (2015) to end of local plan period (2033) SESW – Econometric for WRZ 17% DCLG - Tandridge 23% OAN - Tandridge 26%* * OAN base year is 2013, completions for 2013/14 have been removed so percentage is based on 2015 base year.

Sutton and East Surrey Water were asked to comment on the difference between the econometric forecast and the level of growth forecast if the OAN is delivered:

“We have selected the econometric forecast, which is between the trend and plan based forecasts. We have chosen this based on historical evidence and also other factors. We carry out uncertainty analysis and include this in the supply needs assessment – termed headroom. Higher than predicted growth is a major factor in this analysis. We are planning on significant demand management measures between 2020 and 2025 which will increase the gap between supply and demand further despite population growth. We also re-assess the forecasts each year, before a complete revision in 5 years’ time.”

The SESW water resource zone covers fourteen local authorities including Tandridge (shown in Figure 4.2, and so a regional approach is required in order to ensure that the growth within Tandridge is fully accounted for within the SESW WRMP.

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Figure 4.2 Local authorities within Sutton and East Surrey water resource zone

The spatial boundary for the Water Resource Zone was provided by SESW and used to overlay the local authority boundaries. The Department for Communities and Local Government (DCLG) February 2016 estimates of household growth up to 20397 were collated for the fourteen local authorities which lie within the WRZ. The percentage of the current population of each local authority within the WRZ was estimated from the OS Code Point dataset and spatial data provided for the WRZ. The assessment has used DCLG figures, because they are available for all LPAs within the water resource zone, and over a consistent timescale. The resulting total number of households in the base year within the WRZ is comparable with the figure quoted in the SESW WRMP. Table 4.2 below shows the growth in each local authority area in comparison to the growth forecast by SESW. Mean growth in households from 2015 to 2033 across all of the local authorities is 24%, slightly higher than the figure for Tandridge (23%). Over the same period SESW forecast household growth to be 17%.

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7 Department for Communities and Local Government (2016) 2014-Based Household Projections, 2012 - 2039. Accessed online at https://www.gov.uk/government/statistical-data-sets/live-tables-on-household-projections on 01/05/2018 2018s0255 TDC WCS Phase 2 Outline v2.0 24

Table 4.2 Growth within water resource zone by local authority

Local authority Estimated 2015 Estimated 2033 % Growth Baseline Household over plan household Projection period population Bromley Borough 19 23 25% Crawley Borough 1,758 2,164 23% Croydon borough 36,389 46,806 29% Elmbridge District 8,664 9,956 15% Epsom and Ewell 12,981 16,043 24% District Guildford District 1,497 1,757 17% Horsham District 14 17 19% Merton Borough 10,682 13,249 24% Mid Sussex District 842 1,020 21% Mole Valley District 35,369 40,889 16% Reigate and 58,647 73,481 25% Banstead District Sevenoaks District 7,162 8,482 18% Sutton Borough 81,537 103,652 27% Tandridge District 34,005 41,953 23% TOTAL 289,566 359,490 24% SESW Water WRZ 286,660 340,240 17% total from WRMP

4.2.4 Sutton and East Surrey Water assessment Sutton and East Surrey Water provided comments and a Red/Amber/Green assessment of the proposed development sites. This can be found in Appendix A and summarised below in Table 4.3. An “amber” rating was given to the three garden community sites, “Insufficient evidence in adopted WRMP to confirm that the planned increase in demand can be met”. SESW stated that further modelling was required once final property numbers confirmed. The remaining sites were given a “green” rating confirming that “the adopted WRMP has planned for the increase in demand, or there is sufficient time to address supply demand issues in the next WRMP.”

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Table 4.3 Summary of RAG score for water resources

Water resource RAG score RAG Score description Site references SESW Comments given by SESW GV3 (South Godstone Further modelling garden community) required once final Insufficient evidence in property numbers adopted WRMP to confirm BH007 (Blindley Heath Amber garden community) confirmed. that the planned increase in demand can be met NUT017 (Redhill Aerodrome garden community) Adopted WRMP has All remaining sites N/A planned for the increase in Green demand, or sufficient time to address supply demand issues in the next WRMP.

4.2.5 Conclusions • Growth within Tandridge is comparable in percentage terms with the average growth across the other local authorities within the water resource zone. • Forecast household growth used with SESW WRMP is lower (17%) compared with the DCLG household projections (24%) and the OAN for Tandridge (26%). • SESW carry out uncertainty analysis which includes higher than predicted growth, and the forecast is reassessed annually with a complete revision every 5 years. • Further modelling of garden community sites is required once final property numbers are confirmed.

On the basis that there is a water resource surplus predicted until 2047, and there is sufficient time to adapt the long-term plan to include emerging trends in population, no further assessment of water resources is recommended in a phase 3 detailed study.

Action Responsibility Timescale Continue to regularly review forecast and actual household SESW Ongoing growth across the supply region through WRMP Annual Update reports, and where significant change is predicted, engage with Local Planning Authorities. Take the latest growth forecasts into account in the emerging 2019 WRMP. Provide yearly profiles of projected housing growth to water TDC Ongoing companies to inform the WRMP. Use planning policy to require the 110l/person/day water TDC In Local consumption target permitted by National Planning Policy Plan Guidance in water-stressed areas and use the BREEAM standard to require percentage improvement over baseline building water consumption of at least 12.5%.

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Action Responsibility Timescale Water companies should advise TDC of any strategic water SESW In Local resource infrastructure developments within the council's Plan boundary, where these may require safeguarding of land to prevent other type of development occurring. At present, none have been identified. Further modelling of garden community sites is required SESW Once once final property numbers are confirmed. Local Plan finalised.

4.3 Water Supply Infrastructure

4.3.1 Introduction An increase in water demand adds pressure to the existing supply infrastructure. This is likely to manifest itself as low pressure at times of high demand. An assessment is required to identify whether the existing infrastructure is adequate or whether upgrades will be required. The time required to plan, obtain funding and construct major pipeline works can be considerable and therefore water companies and planners need to work closely together to ensure that the infrastructure is able to meet growing demand. Water supply companies make a distinction between supply infrastructure, the major pipelines, reservoirs and pumps that transfer water around a WRZ, and distribution systems, smaller scale assets which convey water around settlements to customers. This outline study is focused on the supply infrastructure. It is expected that developers should fund water company impact assessments and modelling of the distribution systems to determine requirements for local capacity upgrades to the distribution systems. All sites within Tandridge would be served by Sutton and East Surrey Water. Tandridge District Council have engaged with Sutton and East Surrey Water at an early stage in their local plan process to discuss the infrastructure required. In addition to the work undertaken by water companies, there are opportunities for the local authority and other stakeholders to relieve pressure on the existing water supply system by increasing water efficiency in existing properties. This can contribute to reducing water consumption targets and help to deliver wider aims of achieving water neutrality. A cost-effective solution can be for local authorities to co-ordinate with water supply companies and “piggy back” on planned leakage or metering schemes, to survey and retrofit water efficient fittings into homes8. This is particularly feasible within property owned or managed by the local authorities, such as social housing.

4.3.2 Methodology Sutton and East Surrey Water were provided with a complete list of sites and the potential / equivalent housing numbers for each. Using this information, they were asked to comment on the impact of the proposed growth on water supply infrastructure in the Tandridge area. A RAG assessment was then applied using the following definitions to score each site:

————————————————————————————————————————————— 8 Waterwise (2009) Water Efficiency Retrofitting: A Best Practice Guide. Available at: http://www.waterwise.org.uk/wp-content/uploads/2018/01/Waterwise-2009_Water-efficiency-Retrofitting_Best- practice.pdf 2018s0255 TDC WCS Phase 2 Outline v2.0 27

Infrastructure and/or treatment work upgrades are required to Infrastructure and/or treatment Capacity available to serve the serve proposed growth, but no upgrades will be required to serve proposed growth significant constraints to the proposed growth. Major constraints provision of this infrastructure have been identified. have been identified

SESW also carried out a modelling study in which all development sites were added to the model, providing a “worst case scenario”. The following additional criteria were used to inform their RAG score: • Green - <0.5m pressure change • Amber – reinforcement may be required – 0.5m to 1.0m pressure change • Amber – reinforcement will be required - > 1.0m pressure change • Red – > 1.0m pressure drop - reinforcement will be required AND major constraints have been identified Data collection The following data sets are used to assess the water supply and distribution capacity: • Site locations in GIS format (provided by Tandridge District Council) • A technical note outlining the growth scenario and potential housing numbers for each site • Site tracker spreadsheet (See Appendix A)

4.3.3 Results Table 4.4 summarises the scoring given to each site by SESW. The modelling work carried out by SESW identified eight sites where reinforcement WILL be required, and a further fourteen where reinforcement MAY be required. The remaining sites were assessed as having capacity to serve the proposed growth. No major constraints to providing infrastructure upgrades were identified. Table 4.4 Summary of RAG score by site

Water supply networks RAG Score Site references SESW Comments RAG score description given by SESW Infrastructure and/or treatment upgrades will be required to serve RED None N/A proposed growth. Major constraints have been identified. Infrastructure and/or CAT007, CAT040, Reinforcement will be treatment work GOD010, required upgrades are required GOD021, OXT067, Amber to serve proposed SMA004, SMA040, WAR012 growth, but no

significant constraints to the provision of this

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Water supply networks RAG Score Site references SESW Comments RAG score description given by SESW infrastructure have been identified. Infrastructure and/or BHE007, CMP1, CMP6, Reinforcement may be treatment work ENA12, ENA22, ENA30, required upgrades are required ENA8, NUT017, GV3, to serve proposed SMA039, WAR005, WAR019, Amber growth, but no WAR036, WAR038 significant constraints to the provision of this infrastructure have been identified. CAT016, CAT044, N/A CAT079, CAT081, CMP2, CMP4, Capacity available to ENA27, ENA21, ENA23, Green serve the proposed LIN030, OXT016, OXT021, OXT068, growth OXTC1, SMA008, SMA030, UCS02, UCS09, UCS11, WAR011, WAR016, WAR023

SESW stated that the South Godstone garden community site would be supplied from the Bough Beech WTW, which would have capacity to serve the forecast growth based on the information supplied. Extensive reinforcement is needed to build a new strategic connection to the trunk main at Blindley Heath. This will require a new main between 1.5 and 2km long. This garden community site, if adopted is likely to commence construction in 2025/26 allowing time for this work to be completed assuming developers engage with SESW at the earliest opportunity.

4.3.4 Conclusions • Water supply network reinforcements will be required at eight of the proposed sites and may be required at a further fourteen. • The remaining sites have capacity to serve the proposed growth • The South Godstone garden community site will require extensive reinforcement and a new main 1.5 to 2km long to connect to the Blindley Heath trunk main. • No significant constraints to the provision of these upgrades have been identified.

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4.3.5 Recommendations Action Responsibility Timescale

Undertake technical study to understand infrastructure requirement for potential garden community sites SESW including land that should be TDC TBC safeguarded for Developers infrastructure, and timeline for provision of new connection to trunk main. Undertake technical studies to understand options to provide sufficient bulk and local transfer capacity to sites SESW TBC evaluated as amber and communicate results with TDC. Encourage the use of rainwater harvesting and non- potable water recycling in new TDC development sites, in SESW In local plan particular the garden Developers community sites in order to reduce water demand.

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5 Wastewater collection

5.1 Sewerage Undertaker for Tandridge Southern Water and Thames Water are the Sewerage Undertakers (SUs) for Tandridge. The role of sewerage undertaker includes the collection and treatment of wastewater from domestic and commercial premises, and in some areas, it also includes the drainage of surface water from building curtilages to combined or surface water sewers. It excludes, unless adopted by the SU, systems that do not connect directly to the wastewater network, e.g. Sustainable Drainage Systems (SuDS) or highway drainage. At present, Thames Water do not adopt most forms of SuDS systems, however they will adopt conventional piped surface water drainage systems downstream of private or third-party SuDS, where these drain the building curtilage. Southern Water do not adopt SuDS schemes. Increased wastewater flows into collection systems due to growth in populations or per- capita consumption can lead to an overloading of the infrastructure, increasing the risk of sewer flooding and, where present, increasing the frequency of discharges from Combined Sewer Overflows (CSOs). Likewise, headroom at Wastewater Treatment Works (WwTW) can be eroded by growth in population or per-capita consumption, requiring investment in additional treatment capacity. As the volumes of treated effluent rises, even if the effluent quality is maintained, the pollutant load discharged to the receiving watercourse will increase. In such circumstances the Environment Agency as the environmental regulator, may tighten consented effluent consents to achieve a "load standstill", i.e. ensuring that as effluent volume increases, the pollutant discharged does not increase. Again, this would require investment by the water company to improve the quality of the treated effluent. In combined sewerage systems, or foul systems with surface water misconnections, there is potential to create headroom in the system, thus enabling additional growth, by the removal of surface water connections. This can most readily be achieved during the redevelopment of brownfield sites which have combined sewerage systems, where there is potential to discharge surface waters via sustainable drainage systems (SuDS) to groundwater, watercourses or surface water sewers. In some areas of Tandridge, there are known issues of surface water causing localised flooding. Strategic schemes to provide improved local surface water drainage may be required in such areas, rather than solely relying upon on-site soakaways on brownfield or infill plots.

5.2 Sewerage System Capacity Assessment New residential developments add pressure to the existing sewerage systems. An assessment is required to identify the available capacity within the existing systems, and the potential to upgrade overloaded systems to accommodate future growth. The scale and cost of upgrading works may vary significantly depending upon the location of the development in relation to the network itself and the receiving WwTW. It may be the case that an existing sewerage system is already working at its full capacity and further investigations have to be carried out to define which solution is necessary to implement an increase in its capacity. New infrastructure may be required if, for example, a site is not served by an existing system. Such new infrastructure will normally be secured through private third-party agreements between the developer and utility provider. Sewerage Undertakers must consider the growth in demand for wastewater services when preparing their five-yearly Strategic Business Plans (SBPs) which set out investment for the next Asset Management Plan (AMP) period. Typically, investment is committed to provide new or upgraded sewerage capacity to support allocated growth with a high certainty of being delivered. Additional sewerage capacity to service windfall sites, smaller infill development or to connect a site to the sewerage network across third party land is normally funded via developer contributions, as third-party arrangements between the developer and utility provider.

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5.3 Methodology Southern Water and Thames Water were provided with a list of the sites and forecast housing numbers. Using this information, they were asked to assess each site using the range of datasets they hold. The following red / amber / green traffic light definition was used to score each site:

Infrastructure and/or treatment Infrastructure and/or treatment work upgrades are required to upgrades will be required to Capacity available to serve the serve proposed growth, but no serve proposed growth. Major proposed growth significant constraints to the constraints have been provision of this infrastructure identified. have been identified

5.3.1 Data Collection The following datasets were to assess the sewerage system capacity: • Site locations in GIS format (provided by Tandridge District Council) • Site tracker spreadsheet (see Appendix A)

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5.4 Results Table 5.1 summarises the assessment made by Southern Water and Thames Water on the sewerage network capacity. Eight sites were given an “amber” score, including all three potential garden community sites. Table 5.1 Southern Water and Thames Water RAG assessment of sewerage network capacity

Water supply RAG Score Site networks TW / SW Comments description references RAG score given Infrastructure and/or treatment upgrades will be required to serve N/A RED None proposed growth. Major constraints have been identified. BHE007 Southern Water GOD010 “Delivery of network reinforcement will need to be GV3 aligned with the occupation of development” OXT067 Thames Water “The scale of development/s is likely to require Infrastructure upgrades to the wastewater network. It is and/or treatment recommended that the Developer and the Local work upgrades Planning Authority liaise with Thames Water at the are required to earliest opportunity to agree a housing and serve proposed infrastructure phasing plan. The plan should growth, but no determine the magnitude of spare capacity Amber currently available within the network and what significant CMP2 phasing may be required to ensure development constraints to the NUT017 provision of this does not outpace delivery of essential network SMA30 upgrades to accommodate future development/s. infrastructure WAR005 Failure to liaise with Thames Water will increase the have been risk of planning conditions being sought at the identified. application stage to control the phasing of development in order to ensure that any necessary infrastructure upgrades are delivered ahead of the occupation of development. The developer can request information on network infrastructure by visiting the Thames Water website https://developers.thameswater.co.uk/Developing- a-large-site/Planning-your-development.” Southern Water Capacity available “Where existing capacity is currently available, it is All other Green to serve the not possible to guarantee future reservation of this sites proposed growth capacity” Thames Water

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Water supply RAG Score Site networks TW / SW Comments description references RAG score given “On the information available to date we do not envisage infrastructure concerns regarding wastewater networks in relation to this development/s. It is recommended that the Developer and the Local Planning Authority liaise with Thames Water at the earliest opportunity to advise of the developments phasing. Please contact Thames Water Development Planning, either by email [email protected] tel: 02035779998 or in writing Thames Water Utilities Ltd, Maple Lodge STW, Denham Way, Rickmansworth, Hertfordshire, WD3 9SQ”

Thames water provided some additional comments on the Redhill Aerodrome garden community site: “It’s also important to note that we would also need to understand the impact to the network and confirm how the anticipated flows would be conveyed to the works. Again, certainty of development coming forward and the proposed phasing and scale are all key pieces of information we would need to feed in to our planning process.” “Upgrades are required and aren’t as simple as a new rising main (due to distance) and the size of the proposed development may mean the existing sewer needs upsizing to accommodate anticipated flows. However, we agree that amber would be an acceptable score.” Sewerage Undertakers have a duty under Section 94 of the Water Industry Act 1991 to provide sewerage and treat wastewater arising from new domestic development. Except where strategic upgrades are required to serve very large or multiple developments, infrastructure upgrades are usually only implemented following an application for a connection, adoption, or requisition from a developer. Early developer engagement with water companies is therefore essential to ensure that sewerage capacity can be provided without delaying development.

5.5 Conclusions • Upgrades to the wastewater sewerage network will be required in order to serve the potential garden community sites, and 5 other potential development sites. No significant constraints to provision of this infrastructure have been identified. • Early discussions with the sewerage undertaker are required in order to ensure that sufficient wastewater provision is in place prior to occupation of developments.

No further assessment of wastewater sewerage network capacity is recommended as part of a phase 3 detailed study.

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5.6 Recommendations Table 5.2 Wastewater collection system assessment recommendations

Action Responsibility Timescale Take into account wastewater infrastructure constraints in phasing TDC Ongoing development in partnership with the SW / TW sewerage undertaker Developers will be expected to work with the sewerage undertaker closely and early in the planning promotion process to develop an outline Drainage Strategy for sites. The Outline Drainage strategy should set out the following: What – What is required to serve the site Where – Where are the assets / upgrades to be located SW / TW and Ongoing When – When are the assets to be Developers delivered (phasing) Which – Which delivery route is the developer going to use s104 s98 s106 etc. The Outline Drainage Strategy should be submitted as part of the planning application submission, and where required, used as a basis for a drainage planning condition to be set. Developers will be expected to demonstrate to the Lead Local Flood Authority (LLFA) that surface water from a site will be disposed using a sustainable drainage Developers Ongoing system (SuDS) with connection to surface LLFA water sewers seen as the last option. New connections for surface water to foul sewers will be resisted by the LLFA.

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6 Wastewater Treatment

6.1 Wastewater Treatment Works in Tandridge There are nine WwTW that are likely to serve growth within Tandridge shown in Figure 6.1 below: • Beddington • Lingfield • Burstow • Longreach • Edenbridge • Oxted • Felbridge • Reigate • Godstone Six of these also serve growth in neighbouring authorities areas, and of these six, three are located outside of Tandridge.

Figure 6.1 WwTWs serving Tandridge

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6.2 Wastewater Treatment Works Flow Permit Assessment

6.2.1 Introduction The Environment Agency is responsible for regulating sewage discharge releases via a system of Environmental Permits (EPs). Monitoring for compliance with these permits is the responsibility of both the EA and the plant operators. Figure 6.2 summarises the different types of wastewater releases that might take place, although precise details vary from works to works depending on the design. During dry weather, the final effluent from the Wastewater Treatment Works (WwTW) should be the only discharge (1). With rainfall, the storm tanks fill and eventually start discharging to the watercourse (2) and Combined Sewer Overflows (CSOs) upstream of the storm tanks start to operate (3). The discharge of storm sewage from treatment works is allowed only under conditions of heavy rain or snow melt, and therefore the flow capacity of treatment systems is required to be sufficient to treat all flows arising in dry weather and the increased flow from smaller rainfall events. After rainfall, storm tanks should be emptied back to full treatment, freeing their capacity for the next rainfall event.

Figure 6.2 Overview of typical combined sewerage system and WwTW discharges

Environmental permits are used alongside water quality limits as a means of controlling the pollutant load discharged from a water recycling centre to a receiving watercourse. Sewage flow rates must be monitored for all WwTWs where the permitted discharge rate is greater than 50 m3/day in dry weather. Permitted discharges are based on a statistic known as the Dry Weather Flow (DWF). As well as being used in the setting and enforcement of effluent discharge permits, the DWF is used for WwTW design, as a means of estimating the ‘base flow’ in sewerage modelling and for determining the flow at which discharges to storm tanks will be permitted by the permit (Flow to Full Treatment, FFT). WwTW Environmental Permits also consent for maximum concentrations of pollutants, in most cases Suspended Solids (SS), Biochemical Oxygen Demand (BOD) and Ammonia (NH4). Some works (usually the larger works) also have permits for Phosphorous (P). These are determined by the Environment Agency with the objective of ensuring that the receiving watercourse is not prevented from meeting its environmental objectives, with specific regard to the Chemical Status element of the Water Framework Directive (WFD) classification.

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Increased domestic population and/or employment activity can lead to increased wastewater flows arriving at a WwTW. Where there is insufficient headroom at the works to treat these flows, this could lead to failures in flow consents. Table 6.1 Indicative growth served by each WwTW (realistic scenario)

WwTW Sewerage Permitted Additional Indicative Comments undertaker Maximum housing number of DWF units employees (Ml/d) proposed (Preferred options) Beddington TW 234 2,033 324 Large treatment works serving multiple local authorities. Growth in Tandridge is likely to make up a very small proportion of future flows. Burstow TW 1.596 383 6 Edenbridge SW 2.24 389 0 Minimal growth from within Tandridge (2 houses) Felbridge SW 1.312 92 896 Godstone SW 1.202 251 714 Provision for potential garden community site (GV3) will need to be investigated further. Lingfield SW 3.656 4,138 2,768 Garden community (GV3 – (GV3 – sites (GV3 and 4,000) 2,619) BHE007) likely to be served by this works, Longreach TW 186 9 6 Large treatment works with very minor contribution of growth from Tandridge. Oxted SW 4.724 503 719 Reigate TW 13.334 1,463 47 Minimal growth from (Earlswood) within Tandridge in realistic scenario (without garden community site). Majority from RBBC. Figures include growth commitments, windfall, sites identified through local plan process and growth from neighbouring authorities. Redhill Aerodrome would add an additional 7000 homes to Reigate total – split between TDC and Reigate and Banstead.

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6.3 Methodology Southern Water and Thames Water were provided with the list of proposed development sites and the potential housing numbers for each site (See Appendix A). The water companies were then invited to provide an assessment of the receiving WwTW and provide any additional comments about the impacts of the development. A parallel assessment of WwTW capacity was carried out using measured flow data supplied by the water companies. The process was as follows: • Calculate the current measured Dry Weather Flow (DWF). This was calculated as the 80-percentile exceedance flow for the period January 2015 to December 2017. • The flow data was cleaned to remove zero values and low outlier values which would bring the measured DWF down. • Potential development sites and existing commitments were assigned to a WwTW using the sewerage drainage area boundaries. • For each site, the future DWF was calculated assuming an occupancy rate of 2.41p/h, a per-capita consumption of 122 l/p/d (from SESW WRMP) and the assumption that 95% of water used is returned to sewer. Permitted headroom was used as a substitute for actual designed hydraulic capacity for each WwTW being assessed. The following red / amber / green traffic light definition was used by SW and TW to score each site:

Infrastructure and/or treatment Infrastructure and/or upgrades will be required to treatment upgrades will be Capacity available to serve serve proposed growth, but no required to serve proposed the proposed growth significant constraints to the growth. Major constraints provision of this infrastructure have been identified. have been identified

6.4 Results

6.4.1 Beddington WwTW Beddington WwTW is a very large works north of Tandridge serving approximately 360,000 people in Surrey and South London. Within the study area it is likely to serve development sites around Caterham, Whyteleafe and Woldingham. Thames Water confirmed that the additional growth during the Local Plan period results in an immaterial change to Beddington and they have no concerns. Due to the size of Beddington WwTW catchment, and the relatively small amount of growth within Tandridge it is likely to serve, no further assessment of this treatment works was carried out. WwTW Flow capacity RAG Score Comments from TW Capacity available to serve the proposed growth “Immaterial change – no concerns”

6.4.2 Burstow WwTW Burstow WwTW lies west of the M23 east of Smallfield and is likely to serve new development sites in and around Smallfield. Thames Water state the works is approaching its capacity and the cumulative proposed flow needs to be assessed to understand risk. A headroom assessment has been completed that includes all of the proposed sites within its catchment (Figure 6.3). It can be seen that under the scenario of all of the development sites within Smallfield being adopted, the WwTW is likely to exceed its permit within the next five years.

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Figure 6.3 Headroom assessment for Burstow WwTW

WwTW Flow capacity RAG Score Comments from TW Infrastructure and/or treatment work upgrades are required to serve proposed growth, but no “Approaching capacity limit. Cumulative proposed flow will need to be assessed to significant constraints to the provision of this understand risk” infrastructure have been identified.

Thames Water provided a further comment that “there are currently no drivers to implement upgrades to Burstow STW. There are currently works to ensure resilience.”

6.4.3 Edenbridge WwTW Edenbridge WwTW does not serve any new development sites included within this study, and only one committed site. No assessment was therefore made of this WwTW.

6.4.4 Felbridge WwTW Felbridge WwTW lies in the south of the study area, serving properties within Felbridge and the surrounding area. It is likely to serve the employment sites ENA27, ENA16, ENA22 some existing commitments in the area, and growth from Mid Sussex (63 houses). Southern Water state that the works will be close to its DWF limit by AMP6 (2020) and a new permit may be required if more developer queries come forward. The headroom assessment (Figure 6.4) shows that capacity is available throughout the Local Plan period and beyond.

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Figure 6.4 Headroom assessment for Felbridge WwTW

WwTW Flow capacity RAG Score Comments from SW Infrastructure and/or treatment work upgrades are required to serve proposed growth, but no “DWF close to limit by AMP6. New permit would be needed if more significant constraints to the provision of this developer queries come forward” infrastructure have been identified.

6.4.5 Godstone WwTW The Godstone WwTW catchment covers the settlements of Godstone and Tyler’s Green, and is likely to serve a number of development sites in this area (GOD010, GOD021 and ENA030). Southern Water gave the WwTW a “green” RAG score stating that there is capacity available to serve the proposed growth. The headroom assessment (Figure 6.5) confirms that the WWTW is predicted to stay within its permit for the whole of the Local Plan period and beyond.

Figure 6.5 Headroom assessment for Godstone WwTW

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WwTW Flow capacity RAG Score Comments from SW Capacity available to serve the proposed “566 units headroom on DWF. FFT growth closed to permitted FFT”

The Godstone catchment is close to the north of the proposed South Godstone garden community site, however there is unlikely to be sufficient headroom at this WwTW to be able to serve a significant proportion of this growth without significant upgrades.

6.4.6 Lingfield WwTW Lingfield WwTW lies to the north of Lingfield, and has a catchment covering the settlements of South Godstone, Blindley Heath, Lingfield, Dormansland and the surrounding rural area. The potential garden community sites at Blindley Heath and South Godstone are likely to be served by Lingfield WwTW. In the assessment made by Southern Water a green score was given to smaller sites as there would be sufficient capacity to accommodate these, however the garden community sites were given an amber score highlighting the need for upgrades to accommodate this growth. The amber score has therefore been applied to all sites served by Lingfield WwTW. The headroom assessment (Figure 6.6) predicted that there would be capacity available for the whole of the Local Plan period and up to 2037 where the DWF permit may be exceeded. In the unlikely scenario of both South Godstone and Blindley Heath garden community sites being allocated the permit is likely to be exceeded during AMP9 (2030-2035).

Figure 6.6 Headroom assessment for Lingfield WwTW

WwTW Flow capacity RAG Score Comments from SW Infrastructure and/or treatment work Smaller sites - “End of AMP6 will provide upgrades are required to serve proposed sufficient capacity” growth, but no significant constraints to Garden community sites - “Not planned in the provision of this infrastructure have the current growth scheme (horizon 2030)” been identified.

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6.4.7 Longreach WwTW Longreach WwTW lies 22km to the north east of the area and is a very large WwTW serving a population in excess of 800,000 in Surrey, Kent and South London. A small number of committed sites are likely to be served by Longreach in the north east of the study area, but no sites identified in the Local Plan process are predicted to be served by this works. For this reason, Longreach WwTW has not been assessed further in this study.

6.4.8 Oxted WwTW Oxted WwTW lies south of the town of Oxted and serves Oxted, Hurst Green and the outlying villages. The six development sites within Oxted and Hurst Green are likely to be served by this WwTW as well as the employment site (ENA08) to the north east. Southern Water have scored this WwTW as amber and stated that whilst the development sites can be accommodated individually, when taken collectively the DWF permit would be exceeded. The headroom assessment (Figure 6.7) shows that the DWF permit is currently being exceeded and there is no capacity for additional growth with significant upgrades. Southern Water have confirmed this analysis and made the following comment: “Southern Water are aware of this issue, which is caused by infiltration into the sewer network in the Oxted catchment. SW is currently preparing its business plan for the period 2020-2025 which will be submitted to Ofwat in September this year – it’s intended that there will be an infiltration reduction scheme for Oxted included in the plan, however it is not guaranteed to be in the final plan at this stage, as it will be subject to scrutiny by the water industry’s economic regulator.” “This should enable Southern Water to meet the forecast growth demand in Oxted catchment in 2020-2025”.

Figure 6.7 Headroom assessment for Oxted WwTW

WwTW Flow capacity RAG Score Comments from SW “All ok individually for Oxted. If considered Infrastructure and/or treatment work together: DWF permit is exceeded and new upgrades are required to serve proposed permit required; FFT close to permit. AMP6 growth, but no significant constraints to capacity increase scheme will address a the provision of this infrastructure have maximum of 1000 dwellings as per been identified. forecast. No other query received. Good for AMP7” 2018s0255 TDC WCS Phase 2 Outline v2.0 43

6.4.9 Reigate WwTW Reigate WwTW is a large WwTW 2km to the west of Tandridge and south of the town of Reigate. It serves a population in excess of 50,000 in a catchment covering much of Redhill and Reigate. Within Tandridge, this works is likely to serve a number of committed sites, and outside Tandridge a large amount of growth from the LPA area of Reigate and Banstead (1396 homes). The Redhill Aerodrome potential garden community site (shared with Reigate and Banstead Borough Council) is also likely to be served by this WwTW. Reigate WwTW is being upgraded in this AMP period (2015-2020), with an enhancement to the filters and the installation of tertiary treatment. This will allow the works to accommodate a tighter consent and moderate growth up to 2026. The potential garden community site at Redhill Aerodrome was not accounted for in Thames Water’s plan and have they have made the following comment:

“The proposed Redhill Aerodrome development would change our current proposals of enhancing the existing filters to replacing them with an activated sludge plant (ASP). Hence this is a step change in treatment technology. Also, the DWF limit may be impacted due to the proposed flow. An estimated £20M, over the existing planned cost this AMP, would be needed to bridge this step change in technology. Detailed design is to commence later this year hence we require certainty of whether this site is going ahead and timescales to ensure there are no sunk costs with what we are planning to deliver this AMP.”

Thames Water have therefore assessed this WwTW as red highlighting the need for upgrades to the WwTW and that major constraints have been identified. The headroom assessment (Figure 6.8) confirms this assessment, showing minimal capacity in the current AMP period. The Redhill Aerodrome garden community site would cause the DWF permit to be exceeded in AMP7 (2025-2030).

Figure 6.8 Headroom assessment for Reigate WwTW

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WwTW Flow capacity RAG Score Comments from TW “Works being upgraded to achieve tighter Infrastructure and/or treatment upgrades consent and 2026 growth horizon. will be required to serve proposed growth. Development may exceed DWF limit and Major constraints have been identified. potentially drive tighter effluent consent. Consequence is a step up in treatment technology at a cost in excess of £20m.”

6.5 Impact of higher than expected growth Further analysis was undertaken in which the number of houses provided on each of the garden community sites was increased by 10%. This was found to have a minor increase on the total volume of wastewater treated at Lingfield, and Reigate WwTW, which could result in upgrades being required slightly earlier, but did not change either of the conclusions for those WwTW.

6.6 Conclusions • Southern Water made a further general comment “It should be noted that Southern Water has a statutory duty to serve new development, and whilst individual investment projects to accommodate growth may change or be replaced by alternatives over time, the end result is that given sufficient planning certainty over the location and timing of new growth, this will be accommodated within Southern Water’s wastewater networks.” • Planned growth in Tandridge represents a negligible increase in wastewater flows at Beddington and Longreach WwTW which both have capacity to receive the additional flow. • Capacity is available at Felbridge and Godstone WwTW to serve proposed growth in these catchments throughout the Local Plan period. • Burstow is currently close to its permit limit and addition flow will cause its permit to be exceeded within the next 5 years. A new permit, or upgrades to this WwTW are required. • Lingfield WwTW has the capacity to accept planned growth up to AMP10 (2035- 2040) in the scenario where one garden community site is provided (South Godstone). In the unlikely event of two garden community sites being provided in this catchment, its permit would be exceeded in AMP9 (2030-2035). Final plans for a garden community site within this catchment should be discussed with Southern Water as early as possible to allow upgrades to Lingfield WwTW to be included in its long-term plans. • Oxted is currently exceeding its DWF permit due to infiltration and the current plan is for an infiltration scheme to be included in the draft PR19 plan. This should enable Southern Water to meet the forecast growth in Oxted catchment in 2020- 2025. Any development in this catchment must be carefully phased with upgrades to this works. • Reigate WwTW is currently close to its permit. Much of the growth in this catchment is from outside Tandridge and is likely to be accommodated through a planned capacity upgrade. Should the Redhill Aerodrome garden community site be adopted, a further upgrade will be required to the WwTW at a potential cost of £20M. Thames Water need clarity on whether this site will be adopted at an early stage to avoid sunk cost in their existing upgrade scheme. Further study of the schedule of upgrades at Burstow, Lingfield, Oxted and Reigate WwTW is recommended as part of a phase 3 detailed study.

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6.6.1 Recommendations Action Responsibility Timescale

Confirmation of whether the TDC As soon as practical Redhill Aerodrome garden community site will be adopted is required as early as possible for inclusion in Thames Water’s plans. Consider the available TDC Ongoing WwTW capacity when phasing development going to the same WwTW. This is particularly the case for developments to be served by Oxted and Burstow WwTW, until such time as there is sufficient available evidence that headroom capacity is not an issue. Provide Annual Monitoring TDC Ongoing Reports to Southern Water and Thames Water detailing projected housing growth in the Local Authority. Southern Water and Thames SW / TW Ongoing Water to assess growth TDC demands as part of their wastewater asset planning activities and feedback to TDC if concerns arise.

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7 Water quality assessment

7.1 Introduction An increase in the discharge of effluent from Wastewater Treatment Works (WwTW) as a result of development and growth in the area in which they serve can lead to a negative impact on the quality of the receiving watercourse. Under the Water Framework Directive (WFD), a watercourse is not allowed to deteriorate from its current WFD classification (either as an overall watercourse or for individual elements assessed). It is Environment Agency (EA) policy to model the impact of increasing effluent volumes on the receiving watercourses. Where the scale of development is such that a deterioration is predicted, a variation to the Environmental Permit (EP) may be required for the WwTW to improve the quality of the final effluent, so that the increased pollution load will not result in a deterioration in the water quality of the watercourse. This is known as "no deterioration" or "load standstill". The need to meet river quality targets is also taken into consideration when setting or varying a permit. The Environment Agency operational instructions on water quality planning and no- deterioration are currently being reviewed. Previous operational instructions9 (now withdrawn) set out a hierarchy for how the no-deterioration requirements of the WFD should be implemented on inland waters. The potential impact of development should be assessed in relation to the following objectives: • Could the development cause a greater than 10% deterioration in water quality? This objective is to ensure that all the environmental capacity is not taken up by one stage of development and there is sufficient capacity for future growth. • Could the development cause a deterioration in WFD class of any element assessed? This is a requirement of the Water Framework Directive to prevent a deterioration in class of individual contaminants. The "Weser Ruling"10 by the European Court of Justice in 2015 specified that individual projects should not be permitted where they may cause a deterioration of the status of a water body. If a water body is already at the lowest status ("bad"), any impairment of a quality element was considered to be a deterioration. Emerging practice is that a 3% limit of deterioration is applied. • Could the development alone prevent the receiving watercourse from reaching Good Ecological Status or Potential? Is GES possible with current technology or is GES technically possible after development with any potential WwTW upgrades. A detailed water quality modelling report is included in Appendix B.

7.2 Methodology Following latest guidance from the EA's Thames area office, this assessment has been revised to use a catchment modelling approach, using the EA's SIMCAT software. This is the preferred modelling platform as it has the advantage of assessing the cumulative impacts of increased effluent from all WwTWs discharging to a river or its tributaries. The approach was applied as follows: • The SIMCAT approach was applied to all WwTWs expected to receive significant future growth within the Eden and Mole catchment.

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9 Environment Agency (2012) Water Quality Planning: no deterioration and the Water Framework Directive. Accessed online at http://www.fwr.org/WQreg/Appendices/No_deterioration_and_the_WFD_50_12.pdf on 20/12/2017 10 European Court of Justice (2015) PRESS RELEASE No 74/15 Accessed online at: https://curia.europa.eu/jcms/upload/docs/application/pdf/2015-07/cp150074en.pdf on 20/12/2017 2018s0255 TDC WCS Phase 2 Outline v2.0 47

• Treatment works along the Burstow Stream (Burstow), Eden Brook (Felbridge), Upper Eden (Oxted), Gibbs Brook (Godstone), Ray Brook (Lingfield) and the Mole (Reigate) were modelled. • The contaminants assessed at each WwTW were Biochemical Oxygen Demand (BOD), Ammonia (NH4) and Phosphorous (P). • The SIMCAT model for the Thames River Basin District (RBD) was updated to a baseline using observed river flow, river quality effluent flow and effluent quality statistics for the period 2015 – 2017, supplied by the Environment Agency. • One of the potential impacts of climate change is a reduction in river flows, which would result in lower dilution of wastewater effluent. The potential impacts of this were tested by reducing the river flow statistics within the modelled watercourses. The methodology followed is summarised in the flow chart below:

Could the development Could the development Could the development b. Is GES technically cause >10% deterioration cause deterioration in alone prevent the possible after in water quality? WFD class? receiving water from development and reaching Good potential STW No Yes No Yes Ecological Status or Yes upgrades? No Potential? Specifically: a. is GES possible now with current technology?

No Yes

No Could WFD class deterioration be prevented Yes Is the water body already Could >10% deterioration meeting Good Ecological be prevented using current Status? technology? Yes No

Yes No Sufficient Environmental Good Ecological Status Proposed development Environmental capacity can be accommodated Capacity. Proposed cannot be achieved due with a tighter permit and could be a constraint to development has no to current technology upgrade to treatment. growth significant impact on the limits. Ensure proposed This is achievable with current technology. water body's potential for growth doesn't cause reaching GES. significant deterioration.

Figure 7.1 Water quality impact assessment following EA Thames West guidance

Source: Environment Agency West Thames Area (2015) The EA advised the following technically achievable limits, and that these values should be used for modelling all WwTW potential capacity irrespective of the existing treatment technology and size of works: • BOD (95%ile) = 5mg/l • Ammonia (95%ile) = 1mg/l • Phosphate (mean) = 0.25mg/l

Note that phosphate removal has been the subject of ongoing national trials investigating novel techniques and the optimisation of existing methods. The previous TAL of 0.5mg/l was therefore reduced to 0.25mg/l on the recommendation of the Environment Agency11. This assessment did not take into consideration if it is feasible to upgrade each existing WwTW to best available technology due to constraints of costs, timing, space, carbon costs etc.

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11 Environment Agency (2017) PR19: New approaches for permitting phosphorus. Unpublished note. 2018s0255 TDC WCS Phase 2 Outline v2.0 48

Figure 7.2: WFD Cycle 2 Water Quality Classifications of Watercourses in Tandridge District

7.2.1 Data Collection The datasets used to assess the water quality impact were as follows: River data: • Flow gauges (mean and 95% exceedance flow) • Water quality sampling points (mean and standard deviation for each contaminant) WwTW Discharge data: • Final effluent flow (mean and standard deviation)

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• Effluent quality sampling points (mean and standard deviation for each contaminant) River quality target data: • Current (WFD Cycle 2016) class for each contaminant • River quality objective targets Additional wastewater demand from growth: A wastewater demand was generated using site information recorded in Appendix A, combined with a mean occupancy rate and per capita consumption provided by Thames Water and Southern Water. The scenario where all identified sites are developed was used (see Table 6.1) and where the number of houses provided on each of the garden community sites was increased by 10%.

7.3 Results

Could the development Could the development Could the development Watercourse cause a greater than cause a deterioration in prevent the water body (WwTW) 10% deterioration in WFD class of any from reaching GES? WQ? element? No infrastructure No infrastructure upgrade required to achieve upgrade required to achieve Infrastructure upgrade likely to be required, but achievable with Infrastructure upgrade likely to be required, but treatment at TAL, or not achievable with treatment at TAL Key achievable due to current technology limits. Cannot be achieved with Cannot be achieved with treatment at TAL. treatment at TAL. Environmental capacity could be a constraint on Environmental capacity growth. could be a constraint on growth.

Good status cannot be achieved for P due to No deterioration greater No class deterioration is current technology Burstow than 10% is predicted. predicted. limits. Ensure proposed growth doesn’t cause significant deterioration.

Good status cannot be achieved for P due to current technology limits. The proposed growth should not No deterioration greater No class deterioration is Felbridge prevent the waterbody than 10% is predicted. predicted. achieving good status for P in the future. Ensure proposed growth doesn’t cause significant deterioration.

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Deterioration greater than 10% is predicted for Ammonia. BOD class is predicted to Phosphate already deteriorate from 'Good' to Good status cannot be deemed Bad class is 'Moderate' according to achieved for BOD due to predicted to deteriorate the SIMCAT results, current technology greater than 3%. however as there is no limits. Consequently, Godstone Proposed development WFD 2016 classification current technology, and could be for BOD within the Gibbs not the proposed accommodated with a Brook, then BOD cannot growth, limits progress tighter permit and be assessed for class towards Good status. upgrade to WwTW. This deterioration. is achievable with treatment at TAL.

Good status cannot be achieved for P and BOD BOD class is predicted to due to current deteriorate from 'Good' to technology limits. The 'Moderate'. Proposed proposed growth should Deterioration greater development could be not prevent the Lingfield than 10% is predicted accommodated with a waterbody achieving for all determinands. tighter permit and good status for P or upgrade to WwTW. This BOD in the future. is achievable with Ensure proposed growth treatment at TAL. doesn’t cause significant deterioration.

Good status cannot be achieved for P due to current technology limits. The proposed growth should not No deterioration greater No class deterioration is Oxted prevent the waterbody than 10% is predicted. predicted. achieving good status for P in the future.

Ensure proposed growth doesn’t cause significant deterioration. As the Earlswood Brook has not been classified as a WFD waterbody, the Mole (Horley to No deterioration greater Hersham) is assigned to than 10% is predicted, the reach. The reach is nor is deterioration currently classed as greater than 3% of any No class deterioration is Moderate. BOD and Reigate determinand that is predicted. Phosphate could considered to fall into achieve Good class with Bad class (according to Ammonia achieving SIMCAT results). Moderate through treatment at TAL. Ensure proposed growth doesn't cause significant deterioration.

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• Proposed levels of growth to be treated by Burstow, Felbridge and Oxted WwTWs would not lead to a deterioration, either of 10% or of class in any of the modelled determinands. Existing treatment permits are therefore suitable for these works. • Increased effluent discharges due to growth at Lingfield WwTW is predicted to lead to deterioration of 10% or more, and/or of class. In all cases, deterioration could be prevented by a tightening of permits and possible infrastructure improvements for effluent to be treated at TAL. • At Godstone WwTW, Ammonia is predicted to deteriorate by 10% or more and Phosphate, already classed as Bad, deteriorating by more than 3%. In both cases, deterioration can be limited through infrastructure improvements and tighter permit limits. • At Godstone WwTW, assuming upstream water quality meets Good status and effluent is treated at TAL, BOD is still predicted to deteriorate from Good to Moderate status according to SIMCAT results. Water quality sampling point TH-E0000902, 2.4km downstream of Godstone WwTW, BOD class is predicted to remain at Good status. As BOD has not been classified within the WFD 2016 classification for the Gibbs Brook then it will not be assessed in regard to class deterioration. • None of the receiving watercourses currently meet Good class for Phosphorous downstream of the WwTW's investigated. In all cases current technology to treat Phosphorous is limited. Assuming that upstream water quality can be improved to meet Good, then Good class could be met downstream of Felbridge, Godstone, Lingfield and Oxted. WwTWs. This is achievable through upgrading treatment technologies so that effluent is treated to the technically achievable limit and would not be compromised in the future by the proposed scale of development. At Burstow WwTW, Good class could not be met in the present day or through treatment at TAL. The Burstow stream is currently Poor with the objective to meet Moderate by 2027. • At Reigate (Earlswood) WwTW, based on SIMCAT results, all determinands currently are classed as 'Bad'. There is however, no deterioration greater than 3% when tested with future growth. Through treatment at TAL, both BOD and Phosphate can be improved to meet Good class, with Ammonia improving to Moderate class. The Earlswood Brook has not been classified within WFD waterbody classifications therefore, the Mole (Horley to Hersham) has been assigned for the reach. The reach currently meets Moderate ecological status, with Ammonia meeting Good and both BOD and Phosphate meeting Poor. • An analysis of the potential impacts of reduced river flows as a result of climate change indicate that there is a significant risk of deterioration of water quality. It is expected that future River Basin Management Plans will investigate this risk further and consider how it can be mitigated. Wherever possible, plans should promote "no-regrets" decisions which enhance the resilience of river systems to climate change impacts, for example by promoting Catchment Based Approaches. • The planned growth within Tandridge District and its neighbouring authorities can be accommodated without causing a deterioration in water quality for sanitary determinands and nutrients, so long as timely interventions to prevent deterioration are implemented by Thames Water, Southern Water and the Environment Agency. No additional phase 3 assessment of water quality impacts is required.

7.4 Priority substances and other EU-level dangerous substances As well as the general chemical and physicochemical water quality elements (BOD, NH4, P etc.) addressed above, a watercourse can fail to meet GES due to exceeding permissible concentrations of hazardous substances. Currently 33 substances are defined as hazardous or priority hazardous substances, with others under review. Such substances may pose risks both to humans (when contained in drinking water) and to aquatic life and animals feeding in aquatic life. These substances are managed by a range of different approaches, including EU and international bans on manufacturing and use, targeted bans, selection of safer alternatives and end-of-pipe treatment solutions. There is considerable concern within the UK water industry that regulation of these substances by setting permit values which require their removal at wastewater treatment works will place a huge cost burden

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upon the industry and its customers, and that this approach would be out of keeping with the "polluter pays" principle. We also consider how the planning system might be used to manage priority substances: • Industrial sources – whilst the WCS covers potential employment sites, it doesn't consider the type of industry and therefore likely sources of priority substances are unknown. It is recommended that developers should discuss potential uses which may be sources of priority substances from planned industrial facilities at an early stage with the EA and, where they are seeking a trade effluent consent, with the sewerage undertaker. • Agricultural sources - There is limited scope for the planning system to change or regulate agricultural practices. • Surface water runoff sources - some priority substances e.g. heavy metals, are present in urban surface water runoff. It is recommended that future developments would manage these sources by using SuDS that provide water quality treatment, designed following the CIRIA SuDS Manual. • Domestic wastewater sources - some priority substances are found in domestic wastewater as a result of domestic cleaning chemicals, detergents, or materials used within the home. Whilst an increase in the population due to housing growth could increase the total volumes of such substances being discharged to the environment, it would seem more appropriate to be managing these substances through regulation at source, rather than through restricting housing growth through the planning system. No further analysis of priority substances will be undertaken as part of the Water Cycle Study.

7.5 Recommendations

Action Responsibility Timescale

Provide Annual Monitoring Reports to TDC Ongoing Southern Water and Thames Water detailing projected housing growth in the Local Authority.

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8 Flood Risk Management

8.1 Assessment of Additional Flood Risk from Increased WwTW Discharges

8.1.1 Introduction In catchments with a large planned growth in population and which discharge effluent to a small watercourse, the increase in the discharged effluent might have a negative effect on the risk of flooding. An assessment has been carried out to quantify such an effect.

8.2 Methodology The following process has been used to assess the potential increased risk of flooding due to extra flow reaching a specific WwTW: • Calculate the increase in DWF attributable to planned growth; • Identify the point of discharge of these WwTWs; • At each outfall point, use the FEH CD-ROM v3.0 to extract the catchment descriptors; • Use FEH Statistical method to calculate peak 1 in 30 (Q30) and 1 in 100 (Q100) year fluvial flows; • Calculate the additional foul flow as a percentage of the Q30 and Q100 flow

A red / amber / green score was applied to score the associated risk as follows:

Additional flow ≥5% of Q30. Additional flow ≥5% of Q100. Additional flow ≤5% of Q30. Low Moderate risk that increased High risk that increased risk that increased discharges will discharges will increase fluvial discharges will increase fluvial increase fluvial flood risk flood risk flood risk

The following datasets were used to assess the risk of flooding: • Current and predicted future DWF for each WwTW • Location of WwTW outfalls • Catchment descriptors from FEH CD-ROM v3.012

Beddington and Longreach WwTWs are outside the TDC study area and the contribution of new development growth from Tandridge is significant. For this reason, the impact of additional flows on flood risk downstream of these two WwTW was not studied.

8.3 Results Table 8.1 below reports the additional flow from each WwTW as a percentage of the Q30 and Q100 peak flow. This shows that the additional flows from the WwTW post development, would have a negligible effect on the predicted peak flow events with return periods of 30 and 100 years.

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Table 8.1 Summary of DWF increase as a percentage of Q30 and Q100 peak flow

FEH Stat FEH Stat Additional Additional Flow Flow WwTW Q30 Q100 Average Flow increase % increase % (m3/s) (m3/s) DWF (Ml/d) (m3/s) Q30 Q100 Burstow 13.51 16.72 0.1242 0.0014 0.0% 0.0% Felbridge 3.88 5.21 0.1148 0.0013 0.0% 0.0% Godstone 2.15 2.9 0.1505 0.0017 0.1% 0.1% Lingfield 19.02 23.62 2.8451 0.0329 0.2% 0.1% Oxted 6.38 8.56 0.2306 0.0027 0.0% 0.0% Reigate 3.19 4.24 3.0046 0.0348 1.1% 0.8%

8.4 Impact of higher than expected growth Further analysis was undertaken in which the number of houses provided on each of the garden community sites was increased by 10%. This was found to have a minor increase on the total volume of wastewater treated at Lingfield, and Reigate WwTWs, which would result in a corresponding increase in the flow as a percentage of the Q30 and Q100 flood flow. In all cases this increase is <=0.1% and so the conclusion of the assessment would be unchanged.

8.5 Conclusions • A detailed assessment of flood risk can be found within the Tandridge District Council Level 1 Strategic Flood Risk Assessment (December 2017). • The impact of increased effluent flows is not predicted to have a significant impact upon flood risk in any of the receiving watercourses. • An increase in the size of the garden community sites by 10% would have a negligible impact. Increases in discharges of treated wastewater effluent as a result of growth are not expected to significantly increase flood risk. No further assessment is recommended in a phase 3 WCS.

8.6 Recommendations Table 8.2 Summary of Flood Risk Management Recommendations

Action Responsibility Timescale Proposals to increase discharges to a watercourse may also require a flood risk activities environmental permit from the EA (in the case of discharges Thames Water / During design of to Main River), or a land drainage Southern Water WwTW upgrades consent from the Lead Local Flood Authority (in the case of discharges to an Ordinary Watercourse).

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9 Odour Assessment

9.1 Introduction Where new developments encroach upon an existing Wastewater Treatment Works (WwTW), odour from that site may become a cause for nuisance and complaints from residents. Managing odour at WwTWs can add considerable capital and operational costs, particularly when retro-fitted to existing WwTWs. National Planning Policy Guidance recommends that plan-makers consider whether new development is appropriate near to sites used (or proposed) for water and wastewater infrastructure, due to the risk of odour nuisance.

9.2 Methodology Sewerage undertakers recommend that an odour assessment may be required if the site of a proposed development is close to a WwTW and is encroaching closer to the WwTW than existing urban areas. For Thames Water, this is development sites less than 800m from the WwTW. An updated methodology to that described in the scoping study was applied taking into account the size of the WwTW as well as its proximity to development sites. The Anglian Water Asset Encroachment Risk Assessment Methodology13 was used to give each WwTW a classification based on the population served (population equivalent calculated from consented DWF). A risk category for each development was then assigned based on both the distance from the nearest WwTW and its relative size. Another important aspect is the location of the site in respect to the WwTW. Historic wind direction records for sites around Tandridge indicate that the prevailing wind is from south southwest at both Gatwick and Biggin Hill METAR weather stations.14.

A red / amber / green assessment was applied:

Site location is such that an Site is in an area with Site is unlikely to be impacted by odour impact assessment is confirmed WwTW odour odour from WwTW recommended issues

9.2.1 Data Collection The datasets used to assess the impact of odour from a WwTW were: • Site location in GIS format (provided by TDC) • WwTW locations (from "Consented discharges to controlled waters with conditions" database) • WwTW flow permit (from "Consented discharges to controlled waters with conditions" database) • Site tracker spreadsheet (see Appendix A)

9.2.2 Results Three sites have been given an “amber” assessment: • NUT17 – 493m from Reigate WwTW • ENA22 – 98m from Felbridge WwTW • OXT067 – 169m from Oxted WwTW

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13 Anglian Water (2012) Asset Encroachment Risk Assessment Methodology: Guidance document. Accessed online at: http://www.anglianwater.co.uk/_assets/media/121212_Asset_Encroachment_Risk_Assessment_Methodology_publish(1).pdf on: 20/12/2017 14 RenSMART website http://www.rensmart.com/Weather/WindArchive#monthlyLayer accessed on 20/12/2017 2018s0255 TDC WCS Phase 2 Outline v2.0 56

In the phase 1 scoping study, OXT021 and GV3 were highlighted as being within 800m of a WwTW. However, once a more detailed assessment was carried out, it was found that OXT021 was 760m from Oxted WwTW, and due to the size of the works, unlikely to experience nuisance odour. GV3 is 545m from Godstone WwTW, but as in the case of OXT021, the works the size of this works makes it unlikely that nuisance odour will be experienced. In the case of the three sites given an amber assessment, further odour assessment may be required as part of the planning process. The cost of this should be met by the developer. Should any of the WwTW have their flow permit increased this assessment may need to be re-visited, as the volume of wastewater being treated may increase the amount of odour being generated and place sites previously at low risk of nuisance odour at higher risk.

9.3 Conclusions Three sites: NUT017, ENA22 and OXT067 are close enough to a WwTW that a further odour assessment is recommended as part of the planning process. No further assessment of odour is recommended in the phase 3 detailed study. Any future assessment should be carried out as part of the planning process.

Action Responsibility Timescale Consider odour risk in the sites identified to be at risk from nuisance TDC Ongoing odour Carry out an odour assessment for Site Developers Ongoing 'amber' assessed sites.

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10 Environmental Opportunities and Constraints

10.1 Introduction Development has the potential to cause an adverse impact on the environment through a number routes such as worsening of air quality, pollution to the aquatic environment, or disturbance to wildlife. Of relevance in the context of a Water Cycle Study is the impact of development on the aquatic environment. Water pollution is usually categorised as either diffuse or point source. Point source sources come from a single well-defined point, an example being the discharge from a WwTW. Diffuse pollution is defined as “unplanned and unlicensed pollution from farming, old mine workings, homes and roads. It includes urban and rural activity and arises from industry, commerce, agriculture and civil functions and the way we live our lives.” Examples of diffuse sources of water pollution include: • Contaminated runoff from roads – this can include metals and chemicals • Drainage from housing estates • Misconnected sewers (foul drains to surface water drains) • Accidental chemical / oil spills from commercial sites • Surplus nutrients, pesticides and eroded soils from farmland • Septic tanks and non-mains sewer systems After or during heavy rainfall, the first flush of water carrying accumulated dust and dirt of often highly polluting. Development has the potential to increase the diffuse pollution by providing additional sources from roads and housing estates. Potential impacts on receiving surface waters include the blanketing of river beds with sediment, a reduction in light penetration from suspended solids, and a reduction in natural oxygen levels, all of which can lead to a loss in biodiversity.

10.2 Sites with Environmental Designation

10.2.1 Sites protected by European designations The Habitats Regulations Assessment process is designed to ensure that consideration is given within planning policy to sites protected by European Directives, namely Special Areas of Conservation (SAC) or Special Protection Areas (SPA). Whilst there are no such designated sites within Tandridge, the Habitat Regulations Assessment Stage 1: Screening report15 identifies two sites (Ashdown Forest SAC and SPA and Mole Gap to Reigate Escarpment SAC) within neighbouring districts that, taking a precautionary approach, were included in the HRA process. These are and shown in Figure 10.1 below.

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15 Habitat Regulations Assessment Stage 1: Screening (2017 Update), Tandridge District Council (2017). Accessed online at: https://www.tandridge.gov.uk/Portals/0/Documents/Planning%20and%20building/Planning%20strategies%20and%20policies/Local% 20plan/Local%20plan%202033/Technical%20Assessment%20documents%20published%20in%202017/Habitat-regulations- assessment-stage1-screening-2017.pdf on: 24/05/2018 2018s0255 TDC WCS Phase 2 Outline v2.0 58

Figure 10.1 Sites with environmental designations within or close to Tandridge

In the case of Ashdown Forest SAC and SPA, there is no hydrological pathway from WwTW or development sites within Tandridge and so this site will not be discussed further. The Mole Gap to Reigate Escarpment SAC lies on the North Downs and has the River Mole flowing past it. The River Mole is fed in part from tributaries within Tandridge such as Burstow Stream and Salfords Stream. The impact of development within these catchments on water quality downstream, and its resulting impact on the SAC should therefore be considered.

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10.2.2 Sites of Special Scientific Interest SSSIs are not subject to the HRA process, but are protected under the Wildlife and Countryside Act, and the impact of development on these sites must also be considered. Twelve SSSIs lie in or within 2km of Tandridge. These are shown in Figure 10.2 below.

Figure 10.2 SSSIs within Tandridge in relation to potential development sites

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10.3 Point source pollution The main sources of point source pollution in Tandridge are the WwTW. The effect of additional wastewater flows on water quality is assessed in section 7, and a summary of their probably impact following a source-pathway-receptor approach is presented in Table 10.1. In the majority of cases deterioration in water quality from additional wastewater flow could be prevented by treatment at technically achievable limit (TAL). Table 10.1 WwTW relative to sites with environmental designations

Source Pathway Receptor Distance Probable Impact downstream (km) Burstow WwTW Burstow Mole Gap to 21 Minor - deterioration Stream and Reigate can be prevented by River Mole Escarpment treatment at TAL SSSI / SAC (TQ199532) Felbridge Felbridge Lingfield 8.5 Minor - deterioration Water / Cernes SSSI can be prevented by Eden Brook (TQ 419446) treatment at TAL Felbridge Hedgecourt ~200m Negligible Water SSSI (upstream) (TQ335403) Godstone Gibbs Brook Lingfield 10.5 Minor - deterioration Cernes SSSI can be prevented by (TQ 419446) treatment at TAL Lingfield Eden Brook Lingfield 3.2 Minor - deterioration Cernes SSSI can be prevented by (TQ 419446) treatment at TAL

Oxted Upper Eden Lingfield 8.7 SSSI is upstream of / Middle Cernes SSSI confluence with Eden Eden (TQ 419446) Brook. Upper Eden Staffhurst 1.5 Negligible / No direct Wood SSSI pathway (TQ 412486) Reigate River Mole Mole Gap to 18 Minor - deterioration Reigate can be prevented by Escarpment treatment at TAL SSSI / SAC (TQ199532)

10.4 Diffuse sources of water pollution The most likely sources of diffuse pollution from new developments include drainage from housing estates, and runoff from roads. Sites within Tandridge that could be considered as sources of additional runoff, and receptors in the form of sites with environmental designations are summarised in Table 10.2 below. The pollution risk posed by a site will depend on the sensitivity of the receiving environment, the pathway between the source of the runoff and the receiving waters, and the level of dilution available. A probable impact score of low, medium or high was applied to each site to provide an indication of the likely impact prior to any mitigation being applied. It should be noted that this is a desk-based assessment to highlight risk and should not replace the appropriate level assessment on a site by site basis.

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Table 10.2 Potential sources of diffuse pollution and receptors

Source Pathway Receptor Distance Probable Impact (km) Minimal impact considering distance to SAC, however cumulative impact across all developments, NUT017, especially if Redhill SMA039, Aerodrome garden SMA030, Surface runoff to community site Mole Gap to SMA008, tributaries to comes forward, Reigate SMA015, River Mole >20km should be Escarpment SAC SMA030, (Burstow and considered. / SSSI SMA004, Salfords Stream) SSSI contains SMA040, some ponds that ENA016 may be sensitive to pollution events, however these are some distance from the River Mole. Probable impact - LOW SSSI is a relict damp grassland with ponds and a stretch of the Ray Brook. As such it may be sensitive to changes in the aquatic environment.

Surface runoff Site is adjacent from the potential to SSSI. A garden community tributary to Eden site at Blindley BHE007 Brook passes Heath is likely to Blindley Heath Runoff from through the pass through this garden SSSI 0 SSSI and surface site, so the impact (TQ367448) community water pathways on the SSSI could site flow from be significant. eastern part of site to SSSI. Impact possible – the inclusion of SuDS and appropriate management of runoff should limit pollution risk and potentially improve the situation relative to rural runoff

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Source Pathway Receptor Distance Probable Impact (km) SSSI is an area of semi-natural downland habitat, and ancient woodland, with no mention of water Farthing Downs sensitive features. Surface water and Happy Surface water CAT081 pathway through 1800m Valley SSSI pathway runs SSSI (TQ304572) through SSSI, but results from a small site compared to the catchment. Probable impact - LOW This SSSI consists of pond and wetland habitat and as such may be sensitive to pollution from urban runoff.

The citation from Natural England states “the relatively small area and water volume of ponds means they are particularly Surface water vulnerable to pathway from pollutions events, GOD010 to and accidental ordinary spillages may watercourse east Godstone Ponds affect the whole GOD010 of Godstone and SSSI 850m pond. Management GOD021 into Godstone (TQ353515) of the surrounding Ponds SSSI areas should aim GOD021 is less to maintain good obviously water quality by connected limiting inputs of silt and nutrients” and “where swamp is in continuity with a waterbody, the water quality in the waterbody will affect the swamp.” Impact possible – the inclusion of SuDS and appropriate management of runoff should limit pollution risk and potentially improve the 2018s0255 TDC WCS Phase 2 Outline v2.0 63

Source Pathway Receptor Distance Probable Impact (km) situation relative to rural runoff

Hedgecourt SSSI is described in the citation as the most important wetland site remaining in SE Surrey and as such may be sensitive to changes in the aquatic environment. One small commercial site Surface runoff to has the potential Felbridge Water, Hedgecourt to impact water ENA027 which flows into SSSI 1200m quality through Hedgecourt Lake (TQ335403) runoff but is not SSSI. well connected to the SSSI. Impact possible – the inclusion of SuDS and appropriate management of runoff should limit pollution risk and potentially improve the situation relative to rural runoff SSSI on bank of River Eden. The citation includes “The northern boundary of the site is marked by GV3, BHE007, the slow-flowing ENA021, Eden Brook; the ENA023, aquatic UCS09, communities of UCS11, A large this river, and of ENA12, catchment drains Lingfield Cernes the ditches that GOD010, to the River SSSI (TQ flow into it, OXT016, Eden upstream 419446) contribute to the OXT067, of this SSSI. interest of the OXT021, area”. GOD021, LIN030, Most significant ENA022, impact likely from OXTC01 the two garden community sites. There may be a cumulative impact from all of the development sites within this 2018s0255 TDC WCS Phase 2 Outline v2.0 64

Source Pathway Receptor Distance Probable Impact (km) catchment. Impact possible – the inclusion of SuDS and appropriate management of runoff should limit pollution risk and potentially improve the situation relative to rural runoff Probable impact No pathway from Quarry Hangers - NEGLIGIBLE N/A development SSSI - sites (TQ314538

Caterham Bourne is within a culvert CAT007, Surface runoff to Riddlesdown for most of its CAT040, Caterham SSSI length past this WAR016, Bourne (TQ328600) SSSI. WAR019 Probable impact - NEGLIGIBLE Probable impact No pathway from Saltbox Hill - NEGLIGIBLE N/A development SSSI - sites (TQ401603)

Probable impact No pathway from Staffhurst Wood - NEGLIGIBLE N/A development SSSI - sites (TQ412486)

Probable impact No pathway from Titsey Woods - NEGLIGIBLE N/A development SSSI - sites (TQ420542)

SSSI is above Probable impact Westerham development site - NEGLIGIBLE ENA08 Mines SSSI 80m so no surface (TQ455529) water pathway Woldingham & Probable impact No pathway from Oxted Downs - NEGLIGIBLE N/A development - SSSI sites (TQ369539)

10.5 Surface Water Drainage and SuDS Since April 201516, management of the rate and volume of surface water has been a requirement for all major development sites, through the use of Sustainable Drainage Systems (SuDS).

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16 Department for Communities and Local Government (2014) House of Commons: Written Statement (HCWS161) Written Statement made by: The Secretary of State for Communities and Local Government (Mr Eric Pickles) on 18 Dec 2014. Available at: https://www.parliament.uk/documents/commons-vote-office/December%202014/18%20December/6.%20DCLG-sustainable- drainage-systems.pdf 2018s0255 TDC WCS Phase 2 Outline v2.0 65

Surrey County Council, as Lead Local Flood Authority (LLFA) within the Tandridge, is a statutory consultee to the planning system for surface water management within major development, which covers the following development scenarios:

• 10 or more dwellings • a site larger than 0.5 hectares, where the number of dwellings is unknown • a building greater than 1,000 square metres • a site larger than 1 hectare

SuDS are drainage features which attempt to replicate natural drainage patterns, through capturing rainwater at source, and releasing it slowly into the ground or a water body. They can help to manage flooding through controlling the quantity of surface water generated by a development and improve water quality by treating urban runoff. SuDS can also deliver multiple benefits, through creating habitats for wildlife and green spaces for the community. National standards on the management of surface water are outlined within the Defra Non- statutory Standards for Sustainable Drainage Systems17, with local guidance specified by Surrey County Council18. The CIRIA C753 SuDS Manual19 provides the industry best practice guidance for design and management of SuDS.

10.5.1 Use of SuDS in Water Quality Management SuDS allow the management of diffuse pollution generated by urban areas through the sequential treatment of surface water reducing the pollutants entering lakes and rivers, resulting in lower levels of water supply and wastewater treatment being required. This treatment of diffuse pollution at source can contribute to meeting WFD water quality targets, as well as national objectives for sustainable development. This is usually facilitated via a SuDS Management Train of a number of components in series that provide a range of treatment processes delivering gradual improvement in water quality and providing an environmental buffer for accidental spills or unexpected high pollutant loadings from the site.

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17 Sustainable Drainage Systems, Non-statutory technical standards for sustainable drainage systems, DEFRA (2015). Accessed online at: https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/415773/sustainable-drainage- technical-standards.pdf on: 29/05/2018 18 Water. People. Places. A guide for master planning sustainable drainage into developments. South East 7 (2013). Accessed online at: https://www.susdrain.org/files/resources/other- guidance/water_people_places_guidance_for_master_planning_sustainable_drainage_into_developments.pdf on: 29/05/2018 19 CIRIA Report C753 The SuDS Manual, CIRIA (2015). Accessed online at: https://www.ciria.org/Resources/Free_publications/SuDS_manual_C753.aspx on: 29/05/2018 2018s0255 TDC WCS Phase 2 Outline v2.0 66

•Where practicable, treatment systems should be designed to to be close to source of runoff •It is easier to design effective treatment when the flow rate and pollutant loadings are relatively low Manage surface •Treatment provided can be proportionate to pollutant loadings water close to •Accidental spills or other pollution events can be isolated more source easily without affecting the downstream drainage system •Encourages ownership of pollution •Poor treatment performance or component damage/failure can be delt with more effectively without impacting on the whole site

•Where practicable, treatment systems should be designed to be on the surface •Where sediments are exposed to UV light, photolysis and volatilisation processes can act to break down contaminants •If sediment is trapped in accessible parts of the SuDS, it can be removed more easily as part of maintenance •It enables use of evapotranspiration and some infiltration to Treat surface the ground to reduce runoff volumes and associated total water runoff on contamination loads (provided risk to groundwater is managed the surface appropriately) •It allows treatment to be delivered by vegetation •Sources of pollution can be easily identified •Accidental spills or misconnections are visible immediately and can be dealt with rapidly •Poor treatment performance can be easily identified during routine inspections, and remedial works can be planned efficiently

•SuDS design should consider the likely presence and significant Treat surface of any contaminat that may pose a risk to the receiving water runoff to environment remove a range •The SuDS component or combination of components selected of contaminants should include treatment processes that, in combination, are likely to reduce this risk to acceptably low levels

•The SuDS design should consider and mitigate the risks of Minimise risk of sediments (and other contaminants) being remobilised and sediment washed into receiving surface waters during events greater remobilisation than those which the component has been specifically designed for

•By using a number of components in series, SuDS can help insure that accidental spills are trapped in/on upstream Minimise component surfaces, facilitating contamination managementand removal. impacts from •The selected SudS components should deliver a robust accidental spills treatment design that manages risks appropriately - taking into account eht e uncertainty and variability of pollution ladings and treatment processes

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Managing pollution close to its source can help keep pollutant levels and accumulation rates low, allowing natural processes to be more effective. Treatment can often be delivered within the same components that are delivering water quantity design criteria, requiring no additional cost or land-take. SuDS designs should control the ‘first flush’ of pollutants (usually mobilised by the first 5mm of rainfall) at source, to ensure contaminants are not released from the site. Best practise is that no runoff should be discharged from the site to receiving watercourses or sewers for the majority of small (e.g. less than 5mm) rainfall events. Infiltration techniques will need to consider Groundwater Source Protection Zones (GSPZs) and are likely to require consultation with the Environment Agency. Early consideration of SuDS within master planning will typically allow a more effective scheme to be designed.

10.5.2 Additional benefits Flood Risk The Tandridge Level 1 and Level 2 Strategic Flood Risk Assessment contains recommendations for SuDS to manage surface water on development sites, with the primary aim of reducing flood risk. SuDS are most effective at reducing flood risk for relatively high intensity, short and medium duration events, and are particularly important in mitigating potential increases in surface water flooding, sewer flooding and flooding from small and medium sized watercourses resulting from development. Water Resources A central principle of SuDS is the use of surface water as a resource. Traditionally, surface water drainage involved the rapid disposal of rainwater, by conveying it directly into a sewer or wastewater treatment works. SuDS techniques such as rainwater harvesting, allow rainwater to be collected and re-used as non-potable water supply within homes and gardens, reducing the demand on water resources and supply infrastructure. Climate Resilience Climate projections for the UK suggest that winters may become milder and wetter and summers may become warmer, but with more frequent higher intensity rainfall events, particularly in the south east. This would be expected to increase the volume of runoff, and therefore the risk of flooding from surface water, and diffuse pollution, and reduce water availability. SuDS offer a more adaptable way of draining surfaces, controlling the rate and volume of runoff leaving urban areas during high intensity rainfall, and reducing flood risk to downstream communities through storage and controlled release of rainwater from development sites. Through allowing rainwater to soak into the ground, SuDS are effective at retaining soil moisture and groundwater levels, which allows the recharge of the watercourses and underlying aquifers. This is particularly important where water resource availability is limited, and likely to become increasingly scare under future drier climates. Biodiversity The water within a SuDS component is an essential resource for the growth and development of plants and animals, and biodiversity benefits can be delivered even by very small, isolated schemes. The greatest value can be achieved where SuDS are planned as part of a wider green landscape, providing important habitat, and wildlife connectivity. With careful design, SuDS can provide shelter, food, foraging and breeding opportunities for a variety of species including plants, amphibians, invertebrates, birds, bats and other animals.

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Amenity Designs using surface water management systems to help structure the urban landscape can enrich its aesthetic and recreational value, promoting health and well-being and supporting green infrastructure. Water managed on the surface rather than underground can help reduce summer temperatures, provide habitat for flora and fauna and act a resource for local environmental education programmes and working groups and directly influence the sense of community in an area.

10.6 Conclusions • A number of SSSIs exist within Tandridge, and a hydrological pathway exists to a SAC (Mole Gap to Reigate Escarpment) to the north west. • WwTWs serving growth within Tandridge are the most significant point sources of pollution in the study area. • Additional discharge from WwTW is unlikely to impact sites with environmental designations. See section 7. • Development sites within Tandridge could be sources of diffuse pollution from surface runoff. • Several of the proposed development sites could have a direct surface water pathway to SSSI. • Runoff in these sites should be managed through implementation of a SuDS scheme with a focus on treating the water quality of surface runoff from development sites. • Opportunities exist for these SuDS schemes to offer multiple benefits of flood risk reduction, amenity value and biodiversity. • SuDS for a single site could be demonstrated to have limited impact, but it is the cumulative impact of all development in the catchment (combined with the potential effects of climate change) that should be taken into account. For this reason, SuDS should also be considered on sites that do not have a direct pathway to a SSSI. No further assessment of environmental constraints and opportunities is recommended in a phase 3 detailed study.

10.7 Recommendations

Action Responsibility Timescale

The Local plan should include policies that TDC Ongoing require development sites where a pathway exists for surface water to a site with an environmental designation to adopt SuDS to manage water quality of surface runoff. The local plan should include policies that TDC encourage development sites where no obvious pathway exists to a site with an environmental designation to consider the adoption of SuDS to manage the cumulative impact of development within the catchment, unless it is not reasonably practicable to do so. Encourage the use of rainwater harvesting to TDC Ongoing manage surface water in new developments in order to reduce water demand. 2018s0255 TDC WCS Phase 2 Outline v2.0 69

In partnership, identify opportunities for TDC Ongoing incorporating SuDS into open spaces and SW green infrastructure, to deliver strategic flood TW risk management and meet WFD water quality EA targets. NE Developers should include the design of SuDS Developers Ongoing at an early stage to maximise the benefits of the scheme Work with developers to discourage connection TDC Ongoing of new developments into existing surface water SW and combined sewer networks. Prevent TW connections into the foul network, as this is a Developers significant cause of sewer flooding.

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11 Climate change Impact Assessment

11.1 Approach A qualitative assessment was undertaken to assess the potential impacts of climate change on the assessments made in this water cycle study. This was done using a matrix which considered both the potential impact of climate change on the assessment in question, and also the degree to which climate change has been considered in the information used to make the assessment. The impacts have been assessed on a TDC area wide basis; the available climate models are generally insufficiently refined to draw different conclusions for different parts of Tandridge or doing so would require a degree of detail beyond the scope of this study. Table 11.1 Climate change pressures scoring matrix

Impact of pressure Low Medium High Yes - quantitative Have climate consideration change Some pressures been consideration

considered in but qualitative the only assessment? Not considered

11.1.1 Wastewater collection and treatment Thames Water have published a risk assessment20 for both wastewater treatment and wastewater sewerage networks that identifies the level of threat from climate change in key service areas. In the case of WwTW, the highest perceived risks are in asset performance and pollution incidents, both of which can be attributed to an increased risk of flooding. In the case of the wastewater network, sewer flooding, resulting from increased rainfall intensity overwhelming the sewer network is added to the risks of impacts on asset performance and pollution incidents. Southern Water acknowledge the risk posed by climate change in their annual report21 highlighting the need to protect WwTW and pumping stations from flooding, and the risk posed sewer infrastructure being overwhelmed.

11.1.2 Water quality As presented in more detail in section 7 and Appendix B, the potential impacts of climate change on water quality in rivers receiving discharges of wastewater effluent were tested by reducing the river flow statistics within the modelled watercourses. The results indicate that indicate that there is a significant risk of deterioration of water quality as a consequence of reduced river flows, leading to reduced dilution of treated effluent.

11.2 Results summary Table 11.2 summarises the impact of climate change, and whether it has been taken into account in the assessments contained in the water cycle study. Wastewater collection is scored as "red". This is because whilst both Thames Water and Southern Water have —————————————————————————————————————————————

20 Thames Water's progress in planning for climate change, Thames Water (2016). Accessed online at: https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/519218/climate-adrep-thames-water.pdf on: 25/01/18 21 Annual Report & Financial Statements 2016-17, Southern Water (2017). Accessed online at: https://annualreport.southernwater.co.uk/media/1124/southernwater_annualreport_2016_17.pdf on: 01/06/2018 2018s0255 TDC WCS Phase 2 Outline v2.0 71

published a climate risk assessment for their assets showing they are considering the issue at a strategic level, the assessment within this water cycle did not include the impact of climate change.

Table 11.2 Scoring of climate change consequences for the Water cycle Study

Assessment Impact of Pressure (source of Have climate change pressures been RAG information) considered in the Water Cycle Study (Phases 1 and 2)?

Water High (1) and (2) Yes - quantitative within WRMP and RMBP. resources Climate change impacts on consumption have been calculated in accordance with UKWIR report “Impact of Climate Change on Water Demand” (2013). Water supply Medium - some increased Yes - qualitative consideration within WRMP infrastructure demand in hot weather

Wastewater High - Intense summer rainfall Yes - Qualitative consideration in Thames Collection and higher winter rainfall Water's climate change adaptation report, and increases flood risk Southern Water’s annual report. This has not been considered in site by site assessments. Wastewater Medium - Increased winter Yes - Qualitative consideration in Thames treatment flows and more extreme Water's climate change adaptation report, and weather events reduces flow Southern Water’s annual report. headroom This has not been considered in site by site assessments.

WwTW odour Low No - not considered

Water quality Nutrients: High (1) (3) Yes, sensitivity to reductions in river flow has Sanitary determinands: Medium been tested and indicates there could be a

(1) to High (3) significant risk of a deterioration in water quality as a result of reduced river flows. Flooding from Low No - not considered increased

WwTW discharge (1) River Basin Management Plan (2) Sutton and East Surrey Water WRMP (3) Water quality modelling presented in section X and Appendix B of this study.

11.3 Conclusions and Recommendations No additional assessments of the impact of climate change are recommended for the Phase 3 Detailed WCS.

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Table 11.3 Climate change actions

Action Responsibility Timescale

When undertaking detailed EA, SESW, SW, TW, TDC As required assessments of environmental or asset capacity, consider how the latest climate change guidance can be included. Take "no regrets" decisions in TDC, Developers As required the design of developments which will contribute to mitigation and adaptation to climate change impacts. For example, consider surface water exceedance pathways when designing the layout of developments.

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12 Summary and overall conclusions

12.1 Summary of phase 2 outline study The phase 2 outline water cycle study has been carried out with cooperation with Sutton and East Surrey Water, Southern Water and Thames Water. Table 12.1 summarises the conclusions of the individual assessments and outlines the requirement for a phase 3 detailed study. The overall assessment is that no strategic scale water or wastewater constraints on growth have been identified within Tandridge. Constraints over flow capacity at Oxted and Reigate remain however and will be discussed further in a phase 3 detailed study. A site by site summary of the results of the assessments undertaken is included in Appendix A. Table 12.1 Summary of phase 2 outline study conclusions

Assessment Conclusion Requirement for Detailed Study Water resources • Forecast growth used within SESW Based on the WRMP is lower (17%) compared with comments from the DCLG household projects (24%) Sutton and East and OAN for Tandridge (26%) over the Surrey Water, and local plan period. the evidence • SESW carry out uncertainty analysis presented in their which includes higher than predicted WRMP that there is a growth, and forecast is reassessed water resource annual with a complete revision every 5 surplus predicted years. until 2047, there is • Further modelling of garden community sufficient time to sites is required once final property adapt the term plan numbers are confirmed. to include emerging trends in population and no further assessment of water resources is required in a phase three detailed study. Water supply • Water supply network reinforcements Early developer infrastructure will be required at 8 of the proposed engagement with sites and may be required at a further SESW is essential to 14. ensure that, where • The remaining sites have capacity to necessary, network serve the proposed growth. reinforcement is • The South Godstone garden community delivered prior to site will require extensive reinforcement developments and a new main 1.5 to 2km long to becoming occupied. connect to the Blindley Heath trunk No further main. assessment is recommended in a • No significant constraints to the phase 3 WCS. provision of these upgrades has been identified. Wastewater collection • Upgrades to the wastewater sewerage No further and treatment network will be required in order to assessment of serve the potential garden community wastewater sites, and five other potential sewerage network development sites. No significant capacity is constraints to the provision of this recommended as part infrastructure have been identified. of a phase 3 detailed • Early discussions with the sewerage study. undertaker are required in order to ensure that sufficient wastewater provision is in place prior to occupation.

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Assessment Conclusion Requirement for Detailed Study Wastewater Treatment • Southern Water made a further Further study of the Works Flow Permit general comment “It should be schedule of upgrades assessment noted that Southern Water has a at Burstow, Lingfield, statutory duty to serve new Oxted and Reigate development, and whilst WwTW is individual investment projects to recommended as part accommodate growth may of a phase 3 detailed change or be replaced by study. alternatives over time, the end result is that given sufficient planning certainty over the location and timing of new growth, this will be accommodated within Southern Water’s wastewater networks.” • Planned growth in Tandridge represents a negligible increase in wastewater flows at Beddington and Longreach WwTW which both have capacity to receive the additional flow. • Capacity is available at Felbridge and Godstone WwTW to serve proposed growth in these catchments throughout the Local Plan period. • Burstow is currently close to its permit limit and addition flow will cause its permit to be exceeded within the next 5 years. A new permit, or upgrades to this WwTW are required. • Lingfield WwTW has the capacity to accept planned growth up to AMP10 (2035-2040) in the scenario where one garden community site is provided (South Godstone). In the unlikely event of two garden community sites being provided in this catchment, its permit would be exceeded in AMP9 (2030- 2035). Final plans for a garden community site within this catchment should be discussed with Southern Water as early as possible to allow upgrades to Lingfield WwTW to be included in its long-term plans. • Oxted is currently exceeding its DWF permit due to infiltration and the current plan is for an infiltration scheme to be included in the draft PR19 plan. This should enable Southern Water to meet the forecast growth in Oxted catchment in 2020-2025. Any development in this catchment must be carefully phased with upgrades to this works. Reigate WwTW is currently close to its permit. Much of the growth in this catchment is from outside Tandridge and is likely to be accommodated through a planned capacity upgrade. Should the Redhill Aerodrome garden community site be adopted, a further upgrade will be 2018s0255 TDC WCS Phase 2 Outline v2.0 75

Assessment Conclusion Requirement for Detailed Study required to the WwTW at a potential cost of £20M. Thames Water need clarity on whether this site will be adopted at an early stage to avoid sunk cost in their existing upgrade scheme. Water quality impact • Proposed levels of growth with the The planned growth assessment Burstow, Felbridge and Oxted within Tandridge wastewater catchments can be District and its accommodated without a deterioration neighbouring of 10% or in class for any of the authorities can be modelled determinands. Existing accommodated permits are therefore suitable for these without causing a works. deterioration in • Increased discharge at Lingfield WwTW water quality for would lead to a deterioration of 10% or sanitary more, and/or of class. This could be determinands and prevented through treatment at TAL. nutrients, so long as • At Godstone WwTW, deterioration in timely interventions ammonia and phosphate can be to prevent prevented through treatment at TAL. deterioration are BOD is not classified within the 2016 implemented by WFD classification. Thames Water, Southern Water and • At Reigate (Earlswood) WwTW, the Environment deterioration was predicted to be less Agency. No additional than 3% in any determinand. phase 3 assessment • The potential impacts of reduced river of water quality flows in a climate change scenario impacts is indicate there is a significant risk of recommended. deterioration in water quality. Flood risk from • A detailed assessment of flood risk can Increases in additional WwTW flow be found within the Tandridge District discharges of treated Council Level 1 Strategic Flood Risk wastewater effluent Assessment (December 2017). as a result of growth • The impact of increased effluent flows is are not expected to not predicted to have a significant significantly increase impact upon flood risk in any of the flood risk. No further receiving watercourses. assessment is • An increase in the size of the garden recommended in a community sites by 10% would have a phase 3 WCS. negligible impact. WwTW odour • Three sites (NUT017, ENA22 and No further assessment OXT067) are close enough to a WwTW assessment of odour that a further odour assessment is is recommended in recommended as part of the planning the phase 3 detailed process. The cost for this should be met study. Any future by the developer. assessment should be carried out as part of the planning process. Environmental • A number of SSSIs exist within No further Constraints and Tandridge, and a hydrological assessment of Opportunities pathway exists to a SAC (Mole Gap environmental to Reigate Escarpment) to the north constraints and west. opportunities is • WwTW serving growth within recommended in a Tandridge are point sources of phase 3 detailed pollution study. • Additional discharge from WwTW is 2018s0255 TDC WCS Phase 2 Outline v2.0 76

Assessment Conclusion Requirement for Detailed Study unlikely to impact sites with environmental designations. See section 7.Development sites with Tandridge could be sources of diffuse pollution from surface runoff • Several of the proposed development sites could have a direct surface water pathway to SSSI • Runoff in these sites should be managed through implementation of a SuDS scheme with a focus on treating surface runoff from development sites. • Opportunities exist for these SuDS schemes to offer multiple benefits of flood risk reduction, amenity value and biodiversity. • SuDS for a single site could be demonstrated to have limited impact, but it is the cumulative impact of all development in the catchment (combined with the potential effects of climate change) that should be taken into account. For this reason, SuDS should also be considered on sites that do not have a direct pathway to a SSSI.

12.2 Recommendations Aspect Action Responsibility Timescale

Water Continue to regularly SESW Ongoing resources review forecast and actual household growth across the supply region through WRMP Annual Update reports, and where significant change is predicted, engage with Local Planning Authorities. Take the latest growth forecasts into account in the emerging 2019 WRMP. Provide yearly profiles of TDC Ongoing projected housing growth to water companies to inform the WRMP Use planning policy to TDC In Local Plan require the 110l/person/day water consumption target permitted by National Planning Policy Guidance

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Aspect Action Responsibility Timescale

in water-stressed areas and use the BREEAM standard to require percentage improvement over baseline building water consumption of at least 12.5%. Water companies should SESW In Local Plan advise TDC of any strategic water resource infrastructure developments within the council's boundary, where these may require safeguarding of land to prevent other type of development occurring. At present, none have been identified. Further modelling of SESW Once Local Plan garden community sites finalised. is required once final property numbers are confirmed. Water supply Undertake technical SESW TBC infrastructure study to understand TDC infrastructure Developers requirement for potential garden community sites including land that should be safeguarded for infrastructure, and timeline for provision of new connection to trunk main. Undertake technical SESW TBC studies to understand options to provide sufficient bulk and local transfer capacity to sites evaluated as amber and communicate results with TDC. Encourage the use of TDC In local plan rainwater harvesting SESW and non-potable water Developers recycling in new development sites, in particular the garden community sites. Wastewater Take into account TDC Ongoing collection wastewater SW / TW infrastructure

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Aspect Action Responsibility Timescale

constraints in phasing development in partnership with the sewerage undertaker Developers will be SW / TW and Ongoing expected to work with Developers the sewerage undertaker closely and early in the planning promotion process to develop an outline Drainage Strategy for sites. The Outline Drainage strategy should set out the following: What – What is required to serve the site Where – Where are the assets / upgrades to be located When – When are the assets to be delivered (phasing) Which – Which delivery route is the developer going to use s104 s98 s106 etc. The Outline Drainage Strategy should be submitted as part of the planning application submission, and where required, used as a basis for a drainage planning condition to be set. Developers will be Developers Ongoing expected to LLFA demonstrate to the Lead Local Flood Authority (LLFA) that surface water from a site will be disposed using a sustainable drainage system (SuDS) with connection to surface water sewers seen as the last option. New connections for surface water to foul 2018s0255 TDC WCS Phase 2 Outline v2.0 79

Aspect Action Responsibility Timescale

sewers will be resisted by the LLFA.

Confirmation of TDC whether the Redhill Aerodrome garden community site will be adopted is required as early as possible for inclusion in Thames Water’s plans. Wastewater Consider the available TDC Ongoing treatment WwTW capacity when phasing development going to the same WwTW. This is particularly the case for developments to be served by Oxted WwTW, until such time as there is sufficient available evidence that headroom capacity is not an issue. Provide Annual TDC Ongoing Monitoring Reports to Southern Water and Thames Water detailing projected housing growth in the Local Authority. Southern Water and SW / TW Ongoing Thames Water to TDC assess growth demands as part of their wastewater asset planning activities and feedback to TDC if concerns arise. Water quality Provide Annual TDC Ongoing Monitoring Reports to Southern Water and Thames Water detailing projected housing growth in the Local Authority. Flood risk Proposals to increase management discharges to a During design of Thames Water / watercourse may also WwTW Southern Water require a flood risk upgrades activities

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environmental permit from the EA (in the case of discharges to Main River), or a land drainage consent from the Lead Local Flood Authority (in the case of discharges to an Ordinary Watercourse). Odour from Consider odour risk in WwTW the sites identified to TDC Ongoing be at risk from nuisance odour Carry out an odour assessment for Site Developers Ongoing 'amber' assessed sites. Environmental The Local plan should TDC Ongoing constraints include policies that and require development opportunities sites where a pathway exists for surface water to a site with an environmental designation to adopt SuDS to manage water quality of surface runoff. The local plan should TDC Ongoing include policies that encourage development sites where no obvious pathway exists to a site with an environmental designation to consider the adoption of SuDS to manage the cumulative impact of development within the catchment, unless it is not reasonably practicable to do so. Encourage the use of TDC Ongoing rainwater harvesting to manage surface water in new developments in order to reduce water demand.

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Aspect Action Responsibility Timescale

In partnership, TDC Ongoing identify opportunities SW for incorporating SuDS TW into open spaces and EA green infrastructure, NE to deliver strategic flood risk management and meet WFD water quality targets. Developers should Developers Ongoing include the design of SuDS at an early stage to maximise the benefits of the scheme Work with developers TDC Ongoing to discourage SW connection of new TW developments into Developers existing surface water and combined sewer networks. Prevent connections into the foul network, as this is a significant cause of sewer flooding. Climate When undertaking EA, SESW, SW, TW, As required change detailed assessments of TDC environmental or asset capacity, consider how the latest climate change guidance can be included. Take "no regrets" TDC, Developers As required decisions in the design of developments which will contribute to mitigation and adaptation to climate change impacts. For example, consider surface water exceedance pathways when designing the layout of developments.

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12.3 Requirement for phase 3 detailed study

12.3.1 A realistic approach The aim of a phase 3 detailed study is to identify infrastructure requirements to support proposed growth, when they are required, and how they might be funded. The tools to assess the costs of upgrades (models of water and wastewater systems, detailed knowledge of treatment works condition and processes) are not normally supplied by water companies. Therefore, it is recommended that a phase 3 study takes a realistic approach and assesses the overall quantum of cost within a settlement. This will be done by: • by using the RAG assessments to highlight where investment will be required to several or all of the water and wastewater assets. • asking the water companies to highlight where schemes may be particularly complex (for example if there is insufficient land available to upgrade a treatment works). • Identify mitigation options, alongside potential sources of funding.

12.3.2 Strategic schemes In some locations, there may be benefits in clustering development so that strategic schemes can be developed to serve them. For example, several housing developments along a valley could be served by a new strategic trunk sewer.

12.3.3 Safeguarding strategic sites The phase 3 water cycle study will take the opportunity to engage with the water companies to confirm whether any sites within the district should be safeguarded for possible future strategic developments, such as a major new water supply or a new WwTW. Similarly, opportunities may exist for old WwTW requiring upgrades to be abandoned and moved to a site further from the settlement, freeing land for development – as in the example of Reading WwTW. The WCS will capture known opportunities and make recommendations for safeguarding of sites.

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Appendices

A Appendix A – Site tracker spreadsheet

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B Appendix B – Water Quality Assessment

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