Broden Stables, Crondall

Crondall Developments Ltd Broden Stables, Crondall Flood Risk Assessment, Surface Water & Foul Water Drainage Strategies 132739-R1(2)-FRA AUGUST 2016 RSK GENERAL NOTES Project No.: 132739-R1(2)-FRA Site: Broden Stables, Crondall Title: Flood Risk Assessment, Surface Water & Foul Water Drainage Strategies Client: Crondall Developments Ltd Date: 31st August 2016 Office: Hemel Hempstead Status: Final Author S Williams Technical reviewer M Cheeseman Signature Signature Date: 31st August 2016 Date: 31st August 2016 Project manager M Durant Project Director M Cheeseman Signature Signature Date: 31st August 2016 Date: 31st August 2016 Reviewed Approved Issue No Version/Details Date issued Author by by 1 132739-R1(0)-FRA 17th June 16 SW MD MC 2 132739-R1(1)-FRA 24th June 16 SW MD MC 3 132739-R1(2)-FRA 31st August 16 SW MD MC RSK LDE Ltd (RSK) has prepared this report for the sole use of the client, showing reasonable skill and care, for the intended purposes as stated in the agreement under which this work was completed. The report may not be relied upon by any other party without the express agreement of the client and RSK. No other warranty, expressed or implied, is made as to the professional advice included in this report. Where any data supplied by the client or from other sources have been used, it has been assumed that the information is correct. No responsibility can be accepted by RSK for inaccuracies in the data supplied by any other party. The conclusions and recommendations in this report are based on the assumption that all relevant information has been supplied by those bodies from whom it was requested. No part of this report may be copied or duplicated without the express permission of RSK and the party for whom it was prepared. Where field investigations have been carried out, these have been restricted to a level of detail required to achieve the stated objectives of the work. This work has been undertaken in accordance with the quality management system of RSK LDE Ltd. Crondall Developments Ltd Broden Stables, Crondall Flood Risk Assessment, Surface Water & Foul Water Drainage Strategies 132739-R1(2)-FRA CONTENTS 1 INTRODUCTION .............................................................................................................................. 1 2 CONTEXT AND SCOPE OF WORK ................................................................................................ 2 3 SITE DESCRIPTION ........................................................................................................................ 3 3.1 Location .................................................................................................................................... 3 3.2 Land use and topography ......................................................................................................... 3 3.3 Hydrology ................................................................................................................................. 3 3.4 Geology .................................................................................................................................... 4 3.5 Hydrogeology ........................................................................................................................... 5 3.6 History ...................................................................................................................................... 5 4 DEVELOPMENT PROPOSALS ....................................................................................................... 6 5 LEGISLATION AND POLICY CONTEXT ........................................................................................ 7 5.1 National policy .......................................................................................................................... 7 5.2 Local policy ............................................................................................................................... 8 6 SOURCES OF INFORMATION ....................................................................................................... 9 6.1 Environment Agency consultation ............................................................................................ 9 6.2 Hampshire County Council ..................................................................................................... 10 6.3 Hart District Council ................................................................................................................ 11 6.4 Site walkover .......................................................................................................................... 11 6.5 Relevant studies ..................................................................................................................... 12 6.6 Drainage ................................................................................................................................. 13 7 SOURCES OF FLOOD RISK ......................................................................................................... 14 7.1 Criteria .................................................................................................................................... 14 7.2 Flooding from rivers (fluvial flood risk) .................................................................................... 14 7.3 Flooding from the sea (tidal flood risk) ................................................................................... 15 7.4 Flooding from the land (overland pluvial flood risk) ................................................................ 15 7.5 Flooding from groundwater .................................................................................................... 16 7.6 Flooding from sewers ............................................................................................................. 17 7.7 Other sources of flooding ....................................................................................................... 18 7.8 Flood risk resulting from the development ............................................................................. 18 8 PLANNING CONTEXT ................................................................................................................... 20 8.1 Application of planning policy ................................................................................................. 20 8.2 Land use vulnerability ............................................................................................................. 20 8.3 Sequential Test ....................................................................................................................... 20 9 SURFACE WATER DRAINAGE ASSESSMENT .......................................................................... 22 9.1 Scope .................................................................................................................................... 22 9.2 Pre-development situation ...................................................................................................... 22 9.3 Limiting discharge for design .................................................................................................. 22 9.4 Post-development situation .................................................................................................... 23 10 FOUL DRAINAGE STRATEGY ..................................................................................................... 29 10.1 Overview ................................................................................................................................. 29 10.2 Pre-development situation ...................................................................................................... 29 10.3 Post-development situation .................................................................................................... 29 Crondall Developments Ltd i Broden Stables, Crondall Flood Risk Assessment, Surface Water & Foul Water Drainage Strategies 132739-R1(2)-FRA 11 FLOOD MITIGATION MEASURES ............................................................................................... 30 11.1 Overland flood flow ................................................................................................................. 30 11.2 Finished floor levels ................................................................................................................ 30 12 CONCLUSIONS AND RECOMMENDATIONS ............................................................................. 31 13 REFERENCES ............................................................................................................................... 32 FIGURES Figure 1 – Site Location Map Figure 2 – Topographic Survey and Existing Site Layout Figure 3 – Proposed Site Layout Showing Land Uses Figure 4a – Environment Agency Flood Map for Planning (Rivers & Sea) Figure 4b – Environment Agency Risk of Flooding form Rivers and Sea Map Figure 5 – Environment Agency Risk of Flooding from Surface Water Map Figure 6 – Environment Agency Risk of Flooding from Reservoirs Map Figure 7a – Indicative Surface Water Drainage Strategy Option 1 Figure 7b – Indicative Surface Water Drainage Strategy Option 2 Figure 8 – Indicative Foul Water Drainage Strategy APPENDICES Appendix A – Service Constraints Appendix B – Environment Agency Correspondence Appendix C – Hampshire County Council Correspondence Appendix D – Hart District Council Correspondence Appendix E – Thames Water Sewer Records and Correspondence

Load more