Elmbridge Outline Water Cycle Study: Phase 2- Outline Report Elmbridge Borough Council Project Number 60565750 FINAL October 2019 Elmbridge Outline Water Cycle Study FINAL October 2019 Quality information Prepared by Checked by Verified by Approved by Hannah Booth Amy Ruocco Carl Pelling Sarah Kelly Graduate Water Senior Water and Flood Technical Head, Water Regional Director, Water, Consultant Risk Consultant Resources Ports & Power Christina Bakopoulou Flood Risk Engineer Sarah Waite Consultant Hydrologist Revision History Revision Revision date Details Authorized Name Position 1 19/09/2019 Draft for client & AR Amy Ruocco Project Manager stakeholder comment 2 08/10/2019 Final SK Sarah Kelly Regional Director 3 31/10/2019 Final minor SK Sarah Kelly Regional Director amendments Prepared for: Elmbridge Borough Council Prepared by: AECOM Infrastructure & Environment UK Limited Midpoint, Alencon Link Basingstoke Hampshire RG21 7PP United Kingdom T: +44(0)1256 310200 aecom.com Project No.: 60565750 © 2019 AECOM Infrastructure & Environment UK Limited. All Rights Reserved. This document has been prepared by AECOM Infrastructure & Environment UK Limited (“AECOM”) for sole use of our client (the “Client”) in accordance with generally accepted consultancy principles, the budget for fees and the terms of reference agreed between AECOM and the Client. Any information provided by third parties and referred to herein has not been checked or verified by AECOM, unless otherwise expressly stated in the i AECOM Elmbridge Outline Water Cycle Study FINAL October 2019 document. No third party may rely upon this document without the prior and express written agreement of AECOM. ii AECOM Elmbridge Outline Water Cycle Study FINAL October 2019 Table of Contents List of Acronyms ......................................................................................................... vi Executive summary ................................................................................................... vii 1. Introduction ...................................................................................................... 1 1.1 Background ........................................................................................................................................ 1 1.2 WCS History ....................................................................................................................................... 1 1.3 Study Governance .............................................................................................................................. 1 1.4 Outline WCS Scope ............................................................................................................................ 2 1.5 Key Assumptions and Conditions ......................................................................................................... 3 1.6 Report Structure .................................................................................................................................. 4 2. Study Drivers ................................................................................................... 5 2.1 Introduction ......................................................................................................................................... 5 2.2 OFWAT Price Review .......................................................................................................................... 5 2.3 Water Framework Directive ................................................................................................................. 5 3. Future Housing Growth ................................................................................... 7 3.1 Future Housing Growth Options ........................................................................................................... 7 3.2 Housing .............................................................................................................................................. 7 3.3 Employment Land ............................................................................................................................... 8 4. Wastewater Treatment Strategy ...................................................................... 9 4.1 Wastewater in the Borough .................................................................................................................. 9 4.2 Management of STW Discharges ...................................................................................................... 10 4.3 WFD Compliance .............................................................................................................................. 11 4.4 Habitats Directive .............................................................................................................................. 12 4.5 Wastewater Assessment Overview .................................................................................................... 13 4.6 STW Headroom Assessment ............................................................................................................. 15 4.7 Water Quality Assessment & Infrastructure Requirements .................................................................. 17 4.8 Ecological Appraisal .......................................................................................................................... 26 4.9 Summary of the Wastewater Treatment Strategy ................................................................................ 29 5. Water Supply Strategy ................................................................................... 30 5.1 Introduction ....................................................................................................................................... 30 5.2 Abstraction Licensing Strategies ........................................................................................................ 30 5.3 Water Resource Planning in the Borough ........................................................................................... 32 5.4 Water Supply .................................................................................................................................... 32 5.5 Water Efficiency Plan ........................................................................................................................ 40 6. Major Development Site Assessment ............................................................ 50 6.1 Introduction ....................................................................................................................................... 50 6.2 Assessment Methodologies ............................................................................................................... 50 6.3 Site Assessment tables ..................................................................................................................... 52 7. WCS Outcomes, Recommendations and Policy ............................................ 63 7.1 Water Cycle Study Main Outcomes .................................................................................................... 63 7.2 Policy Recommendations Overview ................................................................................................... 64 7.3 Further Recommendations ................................................................................................................ 66 Appendix A Policy and Legislative Drivers Shaping the WCS .................................. 67 Appendix B Relevant Planning Documents to the WCS........................................... 69 Appendix C STW Capacity Assessment Results ...................................................... 70 Modelling Software ......................................................................................................................................... 70 Modelling assumptions - SIMCAT .................................................................................................................... 70 Model Runs - SIMCAT .................................................................................................................................... 77 Model Results - SIMCAT ................................................................................................................................. 77 iii AECOM Elmbridge Outline Water Cycle Study FINAL October 2019 Water Quality Modelling Methodology - RQP ................................................................................................... 80 Modelling Assumptions - RQP ......................................................................................................................... 81 Assessment Tables - RQP............................................................................................................................... 83 Appendix D Water Neutrality .................................................................................... 84 Twin-Track Approach ...................................................................................................................................... 84 The Pathway Concept ..................................................................................................................................... 84 Improving Efficiency in Existing Development .................................................................................................. 85 Financial Cost Considerations for Water Neutrality scenarios ..........................................................................