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FLOOD RISK ASSESSMENT for Proposed Development at Foster Street, Harlow, Essex, CM17 9HS Grid Reference: 548850E,209000N Prepared on behalf of C J Pryor Ltd & Anderson Design and Build August 2014 Reference: ST2331/FRA-1408-Foster Street Revision 0 Flood Risk Assessment Foster Street, Harlow This report has been prepared by Stomor Ltd. based upon information obtained from others. Stomor Ltd cannot be held responsible for inaccuracies in this information. This report has been prepared for the Client for their sole and specific use. No professional liability or warranty shall be extended to other parties in connection with this report without the explicit written agreement of Stomor Ltd and payment of the appropriate fee. Should the Client wish to pass copies of this report to others for information, the entire report should be copied. Revision Author Checked by Issue Date 0 SJB NJM 11.08.14 Ref: ST2331/FRA-1408-Foster Street i Flood Risk Assessment Foster Street, Harlow CONTENTS 1. Introduction Page 1 2. Site Location Page 4 3. Site Background Page 6 4. Existing Drainage Page 8 5. Proposed Development Page 11 6. Proposed Site Drainage Page 12 7. Potential Sources of Flooding Page 19 8. Summary and Recommendations Page 22 APPENDICES A Site Location Plan, ST-2331-20 B Thames Water Utilities Sewer Records C Greenfield Runoff Calculations D Indicative Drainage Strategies, ST-2331-18-A & ST-2331-19-A E Pre-Development Enquiry & TWU Correspondence Ref: ST2331/FRA-1408-Foster Street ii Flood Risk Assessment Foster Street, Harlow 1.0 Introduction 1.1 Stomor Ltd. has been commissioned by C J Pryor Ltd and Anderson Design and Build to prepare a Flood Risk Assessment (FRA) associated with proposed development on Foster Street, Harlow. A Site Location Plan, Drawing ST-2331-20, is provided in Appendix A. 1.2 The proposed development is to be split across two sites located on the north and south sides of Foster Street. The southern site covers a total area of approximately 2.7ha which is under the ownership of C J Pryor Ltd and comprises two parcels of land; the operational brownfield western part, and the greenfield eastern part. The northern site covers an area of approximately 0.57ha and is currently under the ownership of C J Pryor Ltd. 1.3 For the purposes of this assessment, the northern site will be referred to as the Foster Street North and the southern site will be referred to as the Foster Street South. 1.4 The proposed development of the two sites will be assessed for up to 16 residential units on the Foster Street North site and up to 69 residential units on the Foster Street South site. Current proposals for the sites comprise a lower number of 9 and 65 units on the north and south sites respectively, but to provide a more robust assessment the higher figures will be used in the Flood Risk Assessment. 1.5 Policy Context 1.5.1 This FRA has been prepared in accordance with the relevant national, regional and local planning policy and statutory authority guidance as follows: National policy regarding flood risk as contained within the National Planning Policy Framework (NPPF) dated March 2012, issued by Communities and Local Government and the accompanying Planning Practice Guidance. The Environment Agency (EA) Flood Risk Standing Advice (FRSA) version 3.1 issued April 2012. Epping Forest District Council (EFDC) Combine Policies Local Plan (1998) & Alterations (2006), published in 2008; Policies U2A – Development in Flood Risk Areas, U2B – Flood Risk Assessment Zones, U3A - Catchment Areas and U3B - Sustainable Drainage Systems. Ref: ST2331/FRA-1408-Foster Street Page | 1 Flood Risk Assessment Foster Street, Harlow EFDC & Harlow Council (HC) Strategic Flood Risk Assessment (SFRA) issued April 2011. 1.5.2 Furthermore, the FRA follows the methodology prescribed in CIRIA document C624: Development and Flood Risk, Guidance for the Construction Industry. 1.6 Vulnerability and the NPPF Sequential Test 1.6.1 The NPPF follows a sequential risk based approach in determining the suitability of land for development in flood risk areas, with the intention of steering all new development to the lowest flood risk areas. 1.6.2 The Indicative Floodplain Map obtained from the EA website is provided in Figure 1.1, which shows that the site lies within Flood Zone 1 – Low Probability of Flooding. Figure 1.1 - Environment Agency Indicative Floodplain Map (http://maps.environment-agency.gov.uk) 1.6.3 Flood Zones 1, 2 and 3 are described in the table below: Zone 1 Land assessed as having a less than 1 in 1000 annual probability of river or Low Probability sea flooding in any year (<0.1%) Zone 2 Land assessed as having between a 1 in 100 and 1 in 1000 annual Medium probability of river flooding (1% - 0.1%) or between a 1 in 200 and 1 in 1000 Probability annual probability of sea flooding (0.55% – 0.1%) in any year. Land assessed as having a 1 in 100 or greater annual probability of river Zone 3a flooding (>1%) or a 1 in 200 or greater annual probability of flooding from the High Probability sea (>0.5%) in any year. Ref: ST2331/FRA-1408-Foster Street Page | 2 Flood Risk Assessment Foster Street, Harlow Land where water has to flow or be stored in times of flood. (Land which Zone 3b would flood with an annual probability of 1 in 20 (5%) or greater in any year The Functional or is designed to flood in an extreme (0.1%) flood, or at another probability to Floodplain be agreed between the LPA and the Environment Agency, including water conveyance routes). 1.6.4 The Flood Risk and Costal Change Category (ID 7) of the PPG and associated documents set out that for sites in Flood Zone 1, development proposals on sites comprising one hectare or above the vulnerability to flooding from other sources as well as from river and sea flooding, and the potential to increase flood risk elsewhere through the addition of hard surfaces and the effect of the new development on surface water run-off, should be incorporated in a flood risk assessment. This need only be brief unless the factors above or other local considerations require particular attention. 1.6.5 The Flood Risk and Costal Change Category of the PPG and associated documents identifies that site-specific flood risk assessments should identify and assess the risks of all forms of flooding to and from the development and demonstrate how these flood risks will be managed so that the development remains safe throughout its lifetime, taking climate change into account. 1.6.6 The proposed development will be situated within Flood Zone 1, as identified by Figure 1.1 above. PPG identifies that all uses of land are appropriate within this Flood Zone. Ref: ST2331/FRA-1408-Foster Street Page | 3 Flood Risk Assessment Foster Street, Harlow 2.0 Site Location 2.1 The sites are located in the hamlet of Foster Street, to the east of Harlow and the M11. As previously stated the proposed development is to be split across two sites; Foster Street North, on the north side of Foster Street, and Foster Street South, on the south side. 2.2 The nearest watercourse to the sites is Shonks Brook which is located approximately 860m to the south. However, the EA Indicative Flood Maps indicate that a tributary for Shonks Brook runs along the southern side of the Foster Street South site to connect to Shonks Brook near to the junction between Mill Street and Hastingwood Road. Shonks Brook runs from the M11 towards the south east to connect to Crispey Brook which in turn connects to the River Roding in Chipping Ongar. 2.3 Foster Street North Site 2.3.1 The Foster Street North site is brownfield and currently comprises several agricultural buildings which are generally surrounded by gravelled areas. The main access to the site is a gated access taken from Foster Street to the south east, although there also appears to be an additional access from the west of the site via a gravel track from Foster Street. 2.3.2 There are several drainage ditches in the vicinity of the site, with ditches in place along the north and north east boundaries. In addition, a drainage ditch runs through part of the south west side of the site. 2.3.3 An Affinity Water pumping station and electricity sub-station are currently located in the south west of the site, with associated overhead power lines running towards the north before heading east and west from the north west corner of the site. 2.3.4 Agricultural land surrounds the site to the north, east and west. Foster Street abuts the south of the site, while two residential properties known as ‘Old Farm Cottages’ abut the site to the south east. There is a parcel of land to the west of the site between the western boundary and properties No. 1 & 2 Shoe Lane. 2.3.5 The highest recorded level on the site is 97.26m Above Ordinance Datum (AOD) recorded on the north east side of the electricity sub-station. Excluding the drainage ditches, the lowest site level is 95.86m AOD located in the north eastern corner. Ref: ST2331/FRA-1408-Foster Street Page | 4 Flood Risk Assessment Foster Street, Harlow 2.4 Foster Street South Site 2.4.1 The southern site is formed of two parcels of land; the existing operational brownfield part on the western part of the site covering an area of approximately 1.3ha, and an area of greenfield land to the east which covers the remainder of the site which is sometimes used for the storage of vehicles and earth moving equipment.

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