Haweswater Aqueduct Resilience Programme - Proposed Haslingden and Walmersley Section Environmental Statement Volume 4 Appendix 8.1: Flood Risk Assessment May 2021 Floo d Risk Assessment - Hasling den & Walmersley Secti on United U tilities Proposed Haslingden and Walmersley Section ES, Volume 4 Appendix 8.1: Flood Risk Assessment Haweswater Aqueduct Resilience Programme – Proposed Haslingden and Walmersley Section Project No: B27070CT Document Title: Proposed Haslingden and Walmersley Section ES, Volume 4 Appendix 8.1: Flood Risk Assessment Document Ref.: HBC_RBC_BMBC-HW-TA-008-001 Revision: 0 Date: May 2021 Client Name: United Utilities Water Ltd Jacobs U.K. Limited 5 First Street Manchester M15 4GU +44(0)161.235.6000 +44(0)161.235.6001 www.jacobs.com © Copyright 2021 Jacobs U.K. Limited. The concepts and information contained in this document are the property of Jacobs. Use or copying of this document in whole or in part without the written permission of Jacobs constitutes an infringement of copyright. Limitation: This document has been prepared on behalf of, and for the exclusive use of Jacobs’ client, and is subject to, and issued in accordance with, the provisions of the contract between Jacobs and the client. Jacobs accepts no liability or responsibility whatsoever for, or in respect of, any use of, or reliance upon, this document by any third party. i Proposed Haslingden and Walmersley Section ES, Volume 4 Appendix 8.1: Flood Risk Assessment Contents 1. Introduction ............................................................................................................................................................ 1 1.1 Purpose ....................................................................................................................................................................................... 1 1.2 Proposed Programme of Works Overview .................................................................................................................... 1 2. Scope and Methodology ...................................................................................................................................... 5 2.1 Introduction .............................................................................................................................................................................. 5 2.2 Assessing Flood Risk .............................................................................................................................................................. 5 2.3 Scoping Phase Assessment ................................................................................................................................................. 6 2.4 Main Phase Assessment .................................................................................................................................................... 10 3. Enabling and Construction Phase ................................................................................................................... 13 3.1 Introduction ........................................................................................................................................................................... 13 3.2 Fluvial Flood Risk ................................................................................................................................................................. 13 3.3 Surface Water Flood Risk .................................................................................................................................................. 20 3.4 Groundwater Flood Risk .................................................................................................................................................... 22 3.5 Reservoir Flood Risk ........................................................................................................................................................... 25 3.6 Mitigation ................................................................................................................................................................................ 26 4. Commissioning Phase ........................................................................................................................................ 28 4.1 Introduction ........................................................................................................................................................................... 28 4.2 Groundwater Flood Risk .................................................................................................................................................... 28 4.3 Mitigation ................................................................................................................................................................................ 28 5. Operational Phase .............................................................................................................................................. 29 5.1 Introduction ........................................................................................................................................................................... 29 5.2 Fluvial Flood Risk ................................................................................................................................................................. 29 5.3 Surface Water Flood Risk .................................................................................................................................................. 29 5.4 Groundwater Flood Risks .................................................................................................................................................. 30 5.5 Mitigation ................................................................................................................................................................................ 30 6. Decommissioning Phase ................................................................................................................................... 31 6.1 Introduction ........................................................................................................................................................................... 31 6.2 Fluvial Flood Risk ................................................................................................................................................................. 31 6.3 Groundwater Flood Risks .................................................................................................................................................. 31 6.4 Mitigation ................................................................................................................................................................................ 32 7. Summary and Conclusion ................................................................................................................................. 33 7.1 Summary ................................................................................................................................................................................. 33 7.2 Cumulative Impacts ............................................................................................................................................................ 35 7.3 Conclusion .............................................................................................................................................................................. 35 Annexe A: Flood Risk Assessment Tables ................................................................................................................... 36 Annexe B: EIA Assessment Criteria ............................................................................................................................... 37 Annexe C: Figures.............................................................................................................................................................. 40 Annexe D: Drainage Assessment .................................................................................................................................. 41 ii Proposed Haslingden and Walmersley Section ES, Volume 4 Appendix 8.1: Flood Risk Assessment 1. Introduction 1.1 Purpose 1) This Flood Risk Assessment (FRA) has been prepared to support the planning applications for the Proposed Haslingden and Walmersley Section of the Haweswater Aqueduct Resilience Programme (HARP). The assessment of Flood Risk has been carried out in combination with the Proposed Haslingden and Walmersley Section design development through the Environmental Impact Assessment (EIA) process and informs Chapter 8 (Flood Risk) of the Environmental Statement (ES). 1.1.1 Scope and structure 2) This FRA has been carried out in accordance with the National Planning Policy Framework (NPPF)1 and the Planning Practice Guidance (PPG)2. Complying with planning policy would promote a Scheme that would be appropriate given the level of local flood risks, would be safe during the construction and operational phases of its lifetime, and would not increase flood risk both on site and elsewhere. 3) This FRA will provide the evidence to demonstrate that the Proposed Haslingden and Walmersley Section complies with the above requirements. The structure of the FRA is outlined below: ▪ Section 2 describes the methodology adopted to define the scope of this assessment