Flood Risk & Drainage Assessment Pipestone Proposed Residential
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Flood Risk & Drainage Assessment Pipestone Proposed Residential Development, Wakefield Road, Mapplewell, Barnsley Flood Risk and Foul Drainage Assessment December 2017 WYG Engineering part of the WYG Group creative minds safe hands www.wyg.com Flood Risk & Drainage Assessment Report Control REPORT Flood Risk & Drainage Assessment Project: Proposed Residential Development, Wakefield Rd, Mapplewell Client: Pipestone Job Number: A104788 File Origin: \\LEEDS2\Data\Projects\A100500- A110000\A104788\reports\Residential\Lidl Mapplewell Residential Site FRA Rev A March 2018.docx Document Checking: Primary Author Francisco de Borja Aguilar Initialled: Contributor Initialled: Review By Tom Beavis Initialled: Issue Date Status Checked for Issue 1 20/12/2017 First Issue 2 22/12/2017 Final Issue 3 27/03/2018 Rev A WYG Engineering part of the WYG Group creative minds safe hands www.wyg.com Flood Risk & Drainage Assessment Contents 1 INTRODUCTION ............................................................................................................................. 1 1.1 PURPOSE OF THE REPORT .................................................................................................. 1 1.2 PROPOSED DEVELOPMENT .................................................................................................. 1 1.3 REQUIREMENT FOR SURFACE WATER DRAINAGE ASSESSMENT ............................................ 1 1.4 SCOPE OF THE SURFACE WATER DRAINAGE ASSESSMENT ................................................... 1 1.5 FOUL DRAINAGE ASSESSMENT ............................................................................................ 2 1.6 LIMITATIONS OF THIS REPORT ........................................................................................... 2 2 SITE DESCRIPTION ......................................................................................................................... 3 2.1 EXISTING SITE ................................................................................................................... 3 2.2 EXISTING DRAINAGE .......................................................................................................... 4 3 FLOOD RISK ................................................................................................................................... 7 3.1 FLUVIAL FLOOD RISK .......................................................................................................... 7 3.2 SURFACE WATER FLOODING & OVERLAND FLOWS .............................................................. 7 3.3 SFRA REVIEW ..................................................................................................................... 8 3.4 BARNSLEY MBC - LOCAL FLOOD RISK MANAGEMENT STRATEGY (LFRMS) ............................ 8 3.5 SEWER FLOODING .............................................................................................................. 8 3.6 GROUNDWATER FLOODING ................................................................................................ 9 3.7 RESERVOIR FLOODING ....................................................................................................... 9 3.8 SUMMARY OF FLOOD RISK .................................................................................................. 9 4 DEVELOPMENT PROPOSALS .......................................................................................................... 10 4.1 PROPOSED DEVELOPMENT ................................................................................................ 10 4.2 SEQUENTIAL & EXCEPTION TEST ...................................................................................... 10 4.3 LOCAL PLANNING POLICY ................................................................................................. 10 4.4 DEVELOPMENT AND FLOOD RISK ...................................................................................... 11 4.5 ASSESSMENT OF PRE AND POST DEVELOPMENT AREAS ..................................................... 11 4.6 PROPOSED MITIGATION ................................................................................................... 12 4.7 SURFACE WATER DRAINAGE STRATEGY ............................................................................ 13 4.8 MINIMUM FINISHED FLOOR LEVELS & OVERLAND FLOOD ROUTE....................................... 14 4.9 RESIDUAL FLOOD RISK ..................................................................................................... 15 4.10 FUTURE MAINTENANCE RESPONSIBILITIES ....................................................................... 15 5 SUDS……………… ........................................................................................................................... 16 5.1 SUDS AND DESIGN PRINCIPLES ........................................................................................ 16 5.2 PROPOSED SURFACE WATER DRAINAGE PRINCIPLES ......................................................... 18 5.3 WATER QUALITY .............................................................................................................. 19 5.4 FUTURE SUDS MAINTENANCE RESPONSIBILITIES .............................................................. 20 6 FOUL DRAINAGE ASSESSMENT ...................................................................................................... 22 6.1 EXISITING FOUL DRAINAGE .............................................................................................. 22 6.2 PROPOSED FOUL DRAINAGE STRATEGY ............................................................................ 22 7 CONSENTS REQUIRED .................................................................................................................. 23 7.1 WATER INDUSTRY ACT 1991 ............................................................................................. 23 7.2 OFF SITE SURFACE WATER SEWER ................................................................................... 23 8 CONCLUSIONS & RECOMMENDATIONS .......................................................................................... 24 8.1 CONCLUSIONS .................................................................................................................. 24 8.2 RECOMMENDATIONS ........................................................................................................ 25 WYG Engineering part of the WYG Group creative minds safe hands Proposed Residential Development, Wakefield Road, Mapplewell – Flood Risk & Foul Drainage Assessment 1 Flood Risk & Drainage Assessment APPENDICES Appendix A - Indicative Masterplan Appendix B - Topographic Survey and Utility Survey Appendix C - YW Sewer Record Appendix D - Correspondence with Barnsley MBC LLFA Appendix E - Greenfield Runoff Calculations Appendix F - Proposed Indicative Drainage Appendix G - Supporting Micro Drainage Calculations Appendix H - Typical SUDS Details Appendix I - YW Pre Development Enquiry WYG Engineering part of the WYG Group creative minds safe hands Proposed Residential Development, Wakefield Road, Mapplewell – Flood Risk & Foul Drainage Assessment 2 Flood Risk & Drainage Assessment 1 INTRODUCTION 1.1 PURPOSE OF THE REPORT Pipestone has commissioned WYG Engineering Ltd to undertake a Flood Risk and Drainage Assessment (FRDA) in respect of the proposed residential development in Wakefield Road, Mapplewell. This report has been prepared to accompany the outline planning application for the development as set out below. It should be noted that in developing the surface water and foul drainage strategies for this development due consideration has been made in respect of the separate detailed planning application for a new retail unit which is to be submitted for the site immediately to the south of the proposed residential development. This report (Version Rev A) has been updated to incorporate the revised off site surface water drainage proposals and the recent investigations into the existing foul drainage connection to the Yorkshire Water public sewer system. 1.2 PROPOSED DEVELOPMENT The proposed development is to consist of up to 82 dwellings and associated landscape and infrastructure. The application site is brownfield as it was occupied by an industrial unit that has now been demolished. The proposed development is classified as ‘More Vulnerable’ in accordance with Table 2 of the PPG - Flood Risk & Coastal Change (PPG). A copy of the Indicative Masterplan is contained in Appendix A. 1.3 REQUIREMENT FOR SURFACE WATER DRAINAGE ASSESSMENT According to flood risk mapping provided by the EA, the site is located within Flood Zone 1: i.e. land assessed as having an annual probability of river flooding lower than 1 in 1000 ( <0.1% Annual Exceedance Probability (AEP). However, as the site area exceeds 1 Ha, in accordance with the Planning Practice Guidelines (Flood Risk & Coastal Change) 1, a Flood Risk Assessment is required to support the outline planning application. 1.4 SCOPE OF THE SURFACE WATER DRAINAGE ASSESSMENT The FRDA will be undertaken in accordance with the guidelines of the Environment Agency Flood Risk Assessment Guidance in FZ 1 https://www.gov.uk/guidance/flood-risk-assessment-in-flood-zone-1- andcritical-drainage-areas 1 NPPF Section 103 note 20 WYG Engineering part of the WYG Group creative minds safe hands Proposed Residential Development, Wakefield Road, Mapplewell – Flood Risk & Foul Drainage Assessment 1 Flood Risk & Drainage Assessment In line with the NPPG and the EA requirements, the FRA will review the existing fluvial and