Gatwick Sub-Region Water Cycle Study
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Gatwick Sub-Region Water Cycle Study Final Report August 2020 www.jbaconsulting.com Crawley Borough Council, Horsham District Council, Mid Sussex District Council & Reigate and Banstead District Council CIN-JBAU-XX-XX-RP-EN-0001-A1-C03-WCS_Report.docx i JBA Project Manager Ed Hartwell BSc MSc MCIWEM C.WEM FRGS 35 Perrymount Rd Haywards Heath RH16 3BW Revision History Revision Ref/Date Amendments Issued to S3-P01 – 28/02/2020 Draft Report Crawley Borough Council Horsham District Council Mid Sussex District Council Reigate and Banstead District Council South East Water SES Water Southern Water Thames Water Environment Agency S3-P02 – 20/07/2020 Draft Final Crawley Borough Council Horsham District Council Mid Sussex District Council Reigate and Banstead District Council A1-P03 – 28/08/2020 Final Crawley Borough Council Horsham District Council Mid Sussex District Council Reigate and Banstead District Council Contract This report describes work commissioned by Crawley Borough Council. Richard Pardoe, Holly Cavill and Saskia Salwey of JBA Consulting carried out this work. Prepared by .................................. Louise Morgan BSc Technical Assistant .................................................... Saskia Salwey BSc Assistant Analyst .................................................... Holly Cavill BSc Analyst .................................................... Richard Pardoe MSc MEng Analyst Gatwick sub-region Water Cycle Study ii Reviewed by .................................. Paul Eccleston BA CertWEM CEnv MCIWEM C.WEM Technical Director Purpose This document has been prepared as a Final Report for Crawley Borough Council acting on behalf of the councils in the Gatwick Sub-Region (Crawley Borough Council, Horsham District Council, Mid Sussex District Council, and Reigate and Banstead District Council, hereby referred to as “the Councils”). JBA Consulting accepts no responsibility or liability for any use that is made of this document other than by the Councils for the purposes for which it was originally commissioned and prepared. JBA Consulting has no liability regarding the use of this report except to Crawley Borough Council. Copyright © Jeremy Benn Associates Limited 2020. Carbon Footprint JBA is aiming to reduce its per capita carbon emissions. Gatwick sub-region Water Cycle Study iii Executive Summary In November 2019, JBA Consulting was commissioned by Crawley Borough Council acting on behalf of the councils in the Gatwick Sub-Region (Crawley Borough Council, Horsham District Council, Mid Sussex District Council and Reigate and Banstead Council), to undertake a joint Water Cycle Study (WCS) to inform and provide updated evidence for the councils pre-existing and emerging Local or District Plans. This study assesses the potential issues relating to future development within the Gatwick Sub-Region and the impacts on water supply, wastewater collection and treatment and water quality. 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 to the existing water infrastructure network, including increased intensive 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 This study will assist the councils in the Gatwick Sub-Region 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, the requirements of the environment (and the environmental legislative tests) and by recommending potential solutions to these conflicts. The Water Cycle Study has been carried out in co-operation with the water companies, the Environment Agency (EA) and Natural England (NE) whilst also using published information from the neighbouring Local Planning Authorities (LPAs). Potential development sites were provided by Crawley Borough Council (CBC), Horsham District Council (HDC), Mid Sussex District Council (MSDC) and Reigate & Banstead Borough Council Gatwick sub-region Water Cycle Study iv (RBBC) and wastewater treatment works (WwTW) likely to serve growth in the area were identified using the Environment Agency Consented Discharges to Controlled Waters database. Each development site was then allocated to a WwTW in order to understand the additional wastewater flow resulting from the planned growth. Available information was collated on water policy and legislation, water resources, water quality, and environmental designations within the study area. The objective of the study is to provide evidence to guide development towards the most sustainable sites. Red / Amber /Green (RAG) assessments have been prepared at the site scale where possible for the different aspects of the water cycle. It should be remembered that where a development is scored amber or red in a water supply or wastewater infrastructure assessment, it does not mean that development cannot or should not take place in that location, merely that significant infrastructure may be required to accommodate it. The decision on the suitability of sites is made up of a number of assessments outside the scope of this report. Many of the assessments in this report are based on the assumption that every identified potential allocation will come forward during the plan period and as such represents the ‘worst case’ for growth within each wastewater catchment. In reality the level of growth in each catchment is likely to be less and further analysis will be undertaken based on the final selection of sites. Water Resources South East Water (SEW), SES Water (SESW) and Southern Water (SW) are responsible for supplying the study area with water. In common with most of the south east, all of the Gatwick Sub-Region is an area of serious water stress. The more stringent water efficiency target for new development of 110 l/p/d allowed under Building Regulations is justified, however there is a clear need to go further than this. Southern Water have made reducing per capita consumption to 100 l/p/d an integral part of their water resource management plan. The WCS therefore recommends that the councils adopt a policy requiring all new development to achieve 100 l/p/d and to achieve 80 l/p/d in strategic developments. This approach is supported by all three water supply companies in the study area, the Environment Agency and Natural England. Growth plans defined in Water Resource Management Plans (WRMPs) are broadly in line with Ministry of Housing Communities and Local Government household projections. Planned growth during the plan period for Horsham, Mid Sussex and Reigate and Banstead exceeds the percentage level of growth accounted for in WRMPs. In Crawley it is in line with the WRMP. SES Water, SEW and SW have confirmed that they have sufficient water resources to serve the proposed level of growth, however challenges have been identified in the Hardham catchment and discussions are ongoing to investigate the sustainability of this abstraction. Water supply infrastructure All the sites assessed in the study were given a green or amber score by SEW and SW based on the size of the development, and the likelihood of network reinforcement being required. No constraints to providing this reinforcement were identified. SESW did not provide a site by site assessment, advising that this would be done on a case by case process and the local plan develops. Wastewater collection infrastructure Southern Water and Thames Water (TW) provide wastewater services to the Gatwick Sub-Region 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 SW and TW is therefore essential to ensure that sewerage capacity can be provided without delaying development. Wastewater infrastructure upgrades would be required in order to serve the proposed level of growth. No constraints to providing this infrastructure have been identified by SW or TW. Gatwick sub-region Water Cycle Study v Wastewater treatment capacity SW and TW provided an assessment of the WwTW serving growth in their area based on the size of the development. JBA also performed a flow permit assessment in parallel to this based on the current flows provided by the water companies, flow permit and the additional effluent