Cole Easdon Consultants Limited

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1 FLOOD RISK ASSESSMENT FOR PROPOSED EXPANSION OF WHITEHALL GARDEN CENTRE CORSHAM ROAD, LACOCK ON BEHALF OF WHITEHALL GARDEN CENTRES LTD. OCTOBER 2015 [ISSUE 2] Head Office: Unit 2 York House Edison Park Dorcan Way Swindon Wiltshire SN3 3RB Tel cec@coleeasdon.com Cole Easdon Consultants Limited Civil Engineering ~ Highways ~ Transportation ~ Flood Risk Bristol & Swindon Incorporated in UK as Cole Easdon Consultants Ltd No

2 FLOOD RISK ASSESSMENT PROPOSED EXPANSION OF WHITEHALL GARDEN CENTRE, CORSHAM ROAD, LACOCK Cole Easdon Consultants (CEC) DOCUMENT ISSUE RECORD Client: Project: Whitehall Garden Centre Proposed Expansion of Whitehall Garden Centre, Corsham Road, Lacock Job Number: 4694 Document Title: Issuing Office: Flood Risk Assessment Swindon Issue / Revision: Issue 1 Issue 2 Description / Status: Draft for Client Comment Formal Issue Date: September 2015 October 2015 Prepared: S. Starr BSc (Hons) S. Starr BSc (Hons) Signature: Document Check: S. Coates BA (Hons) S. Coates BA (Hons) Signature: Technical Check: R. Bowley BSc CEng MCIWEM R. Bowley BSc CEng MCIWEM Signature: Authorised: R. Bowley BSc CEng MCIWEM R. Bowley BSc CEng MCIWEM Signature: File Reference: 4694 Whitehall Garden Centre, Lacock - FRA Issue Whitehall Garden Centre, Lacock - FRA Issue 2 QMF ISSUE 5 Cole Easdon Consultants (CEC) OCTOBER 2015

3 FLOOD RISK ASSESSMENT PROPOSED EXPANSION OF WHITEHALL GARDEN CENTRE, CORSHAM ROAD, LACOCK CONTENTS SECTION HEADING PAGE NO. 1.0 INTRODUCTION THE EXISTING SITE FLOOD RISK ISSUES PROPOSED DRAINAGE STRATEGY SUMMARY AND CONCLUSIONS 13 APPENDICES Appendix 1 CEC Figures CEC Figure 4694/500/Figure 1 CEC Figure 4694/500/Figure 2 Site Location Plan Flood Zone Map Appendix 2 Geological Records Appendix 3 Calculations Appendix 4 Report Excerpts Appendix 5 Public Sewer Records Appendix 6 CEC Plans & Drawings by Others CEC Plan 4694/500(A) Existing Site Plan Sheets 1 & 2 CEC Plan 4694/501(A) Proposed Drainage Strategy Sheets 1 & 2 Drawing No. P01(A) Proposed Site Layout Plan (by Andrew Aldridge Architects) QMF ISSUE 5 Cole Easdon Consultants (CEC) OCTOBER 2015

4 FLOOD RISK ASSESSMENT PROPOSED EXPANSION OF WHITEHALL GARDEN CENTRE, CORSHAM ROAD, LACOCK 1.0 INTRODUCTION 1.1 This Flood Risk Assessment has been prepared by Cole Easdon Consultants (CEC) on behalf of Whitehall Garden Centre in respect of a proposed expansion of Whitehall Garden Centre, Corsham Road, Lacock, Wiltshire. Refer to CEC Figure 4694/500/Figure 1 [Site Location Plan] in Appendix 1. Development Proposals 1.2 The development proposal comprises expansion of the existing garden centre to provide numerous retail units, additional external areas including an ice rink, sales yards, service areas and access roads. The existing gravel car park in the west of the site is to be formalised and resurfaced with tarmac. The existing access route from Corsham Road will be maintained. Refer to Drawing No. P01(A) [Proposed Site Layout Plan] (by Andrew Aldridge Architects) in Appendix 6. This layout forms the basis of CEC Plan 4694/501(A) [Proposed Drainage Strategy], also located in Appendix 6. Need for Study 1.3 The purpose of this assessment is to demonstrate that the proposals outlined above can be satisfactorily accommodated without worsening flood risk to the area, in accordance with the National Planning Policy Framework Document (NPPF). 1.4 Accordingly, this study has been prepared to: i) Assess flood risk to the development from fluvial sources; ii) Assess flood risk to the development from other potential sources, including ditches, sewers, groundwater and overland surface water flow; iii) Ensure that the development proposed will fully comply with the requirements of the EA's policy on the safeguarding of floodplains; iii) Provide a SUDS surface water drainage strategy for the site; and iv) identify a foul drainage strategy for the proposed development 1.5 A site topographical survey (referenced to Ordnance datum) has been provided to CEC and has been reviewed as part of this study. Refer to CEC Plan 4694/500(A) [Existing Site Plan Sheets 1 & 2] in Appendix 6. QMF ISSUE 5 Cole Easdon Consultants (CEC) 1 OCTOBER 2015

5 FLOOD RISK ASSESSMENT PROPOSED EXPANSION OF WHITEHALL GARDEN CENTRE, CORSHAM ROAD, LACOCK Scope of Study 1.6 In Section 2.0, we describe the characteristics of the development site and surrounding area. In Section 3.0, we assess flood risk issues. Section 4.0 covers the proposed drainage strategy and conclusions are presented in Section The following resources have been used for this study: Flood Zone Map Environment Agency (EA); Groundwater Source Protection Zones Map - Environment Agency (EA); Geological Map - British Geological Survey (BGS); and Topographical Survey Drawing 8015 Hywel John Surveys. 1.8 The following publicly available documents have also been reviewed as part of this assessment: Wiltshire Strategic Flood Risk Assessment (Scott Wilson 2008); North Wiltshire Strategic Flood Risk Assessment Level One (Scott Wilson October 2007); Wiltshire Council Surface Water Management Plan Focused on Chippenham Trowbridge and Salisbury (URS Scott Wilson (November 2011); National Planning Policy Framework (NPPF) (March 2012); Technical Guidance to the NPPF (March 2012); Sewers for Adoption, 7 th Edition A Design and Construction Guide for Developers (SFA 7) ( March 2006); CIRIA C697 The SUDS Manual; Building Regulations 2010 Approved Document H (Drainage and Waste Disposal); and Rainfall Runoff Management for Developments (Defra). 1.9 The following abbreviations are used in this report: AOD Above Ordnance Datum; EA Environment Agency; SUDS Sustainable Urban Drainage Systems; HA Highway Authority; SAB SUDS Adopting Body; FZM Flood Zone Map prepared by the Environment Agency; NPPF National Planning Policy Framework; LPA Local Planning Authority; 1% event 1 in 100 Year return period storm; and QMF ISSUE 5 Cole Easdon Consultants (CEC) 2 OCTOBER 2015

6 FLOOD RISK ASSESSMENT PROPOSED EXPANSION OF WHITEHALL GARDEN CENTRE, CORSHAM ROAD, LACOCK 1% + CC event 1 in 100 Year return period storm including a 30% allowance for climate change. QMF ISSUE 5 Cole Easdon Consultants (CEC) 3 OCTOBER 2015

7 FLOOD RISK ASSESSMENT PROPOSED EXPANSION OF WHITEHALL GARDEN CENTRE, CORSHAM ROAD, LACOCK 2.0 THE EXISTING SITE Refer to CEC Figure 4694/500/Figure 1 [Site Location Plan] in Appendix 1 and CEC Plan 4694/500(A) [Existing Site Plan Sheets 1 & 2] in Appendix The site comprises a large garden centre complex covering 8.2ha. It is located approximately 300m north west of the village of Lacock. The site address is Whitehall Garden Centre, Corsham Road, Lacock, Chippenham Wiltshire, SN15 2LZ. National grid reference ST The site contains various buildings used as shops, restaurants and other customer facilities, in addition to external yards for storage, deliveries and plant display. A tarmac car park is located adjacent to the existing site access, in the north of the site. The western part of the site comprises a landscaped park and a large gravel car park. 2.3 The site forms an irregularly shaped parcel of land with a wooded boundary of mature trees and hedgerows. The northern site boundary is formed by Corsham Road and the gardens of properties fronting the road. A track named Rosemary Lane is routed along the site s western boundary, with farmland beyond. A public footpath forms the southern boundary of the site, with further farmland located further to the south. The A350 highway, and Corsham Road delineate the eastern margin of the site. 2.4 The site is accessed from Corsham Road. 2.5 Land use in the vicinity of the site is primarily agricultural. The nearest sizeable residential areas are Chippenham, approximately 3km to the north, and Lacock, 300m to the south east. 2.6 Ground levels within the site fall to the south. Existing ground levels vary between 64.00mAOD in the north western corner of the site, to 50.00mAOD at its south west corner. Nearby Watercourses/Drainage Features 2.7 The River Avon, a Main River, drains the local catchment. An unnamed tributary of the Avon flows in a south-easterly direction some 100m west of the site s western boundary. It flows through the farmland to the south of the site, and turns to flow east beneath the A350 and through the centre of Lacock. It meets its confluence with the River Avon to the east of Lacock, some 800m south east of the site. QMF ISSUE 5 Cole Easdon Consultants (CEC) 4 OCTOBER 2015

8 FLOOD RISK ASSESSMENT PROPOSED EXPANSION OF WHITEHALL GARDEN CENTRE, CORSHAM ROAD, LACOCK 2.8 A ditch is routed along the southern boundary of the site. It outfalls to a deep, steep sided gully near the south western corner of the site, which then discharges to the unnamed tributary at Pinnell s Mill. Existing Drainage/Sewers 2.9 The site is served by a private surface water drainage system comprising gullies, linear drains and gravity pipework with a connection to the existing ditch at the southern boundary of the site. The existing impermeable area at the site measures 23,000m Wessex Water sewer records confirm that a public foul sewer (225mm diameter) flows east along Corsham Road then turns to follow a south easterly course along the site frontage, then flows south east under Cantax Hill. Foul flows from the existing kitchens and lavatories in the eastern part of the site are pumped to this system from a holding tank located in a landscaped area to the south of the westerly garden centre building. A second pump is located in the east of the site and lifts effluent to a gravity foul drain which flows along the southern side of the eastern most garden centre building. Both systems outfall to a manhole adjacent to the site s eastern boundary which connects with the existing public foul sewer in the verge of the A350. The existing drainage system is highlighted on CEC Plan 4694/500(A) [Existing Site Plan Sheets 1 & 2] in Appendix 6. Refer to Appendix 5 for Wessex Water records. Existing Ground Conditions Refer to Geological Records in Appendix An intrusive site investigation has yet to be undertaken, however the British Geological Survey (BGS) Map indicates that the locality is underlain by bedrock known as Kellaways Formation which is composed of sandstone, siltstone and mudstone. These strata are overlain by variable Alluvial deposits of clay, silt, sand and gravel. The site is brownfield land therefore made ground is likely to be present beneath the existing buildings, hard surfaced areas and car parking areas Groundwater levels are currently unknown. The lowest lying land in the vicinity of the site is near its south eastern corner, within the existing gully feature. The bed of the gully is some 3m below the lowest part of the site however it remains dry and contains water only following rainfall, this being surface water runoff rather than groundwater. It is therefore reasonable to assume that the water table lies at least 3m below the lowest part of the site, and that it is significantly deeper over much of the more elevated parts of the site. QMF ISSUE 5 Cole Easdon Consultants (CEC) 5 OCTOBER 2015

9 FLOOD RISK ASSESSMENT PROPOSED EXPANSION OF WHITEHALL GARDEN CENTRE, CORSHAM ROAD, LACOCK 2.13 The contamination status of the site is unknown, and should be considered in due course as part of an Environmental Desk Study report EA mapping classifies the bedrock beneath the area as non aquifer. The superficial gravel deposits are termed a Secondary A Aquifer (formerly a Minor Aquifer) and as such may support water supply and river base flow on a local rather than strategic scale The EA s Groundwater Source Protection Zone Map confirms that the site lies within the innermost Groundwater Source Protection Zone, therefore water abstraction for sensitive usage is likely to occur in close proximity to the site. QMF ISSUE 5 Cole Easdon Consultants (CEC) 6 OCTOBER 2015

10 FLOOD RISK ASSESSMENT PROPOSED EXPANSION OF WHITEHALL GARDEN CENTRE, CORSHAM ROAD, LACOCK 3.0 FLOOD RISK ISSUES Flood History 3.1 There is no history of flooding at the site recorded within the Strategic Flood Risk Assessment, nor the Surface Water Management Plan. 3.2 According to the documents listed above, the site is not within a Critical drainage Drainage Area. Refer to Appendix 5 for report excerpts. Fluvial/Tidal Flood Risk 3.3 The Environment Agency s Flood Zone Map (FZM) indicates that the site lies entirely within Flood Zone 1 (low risk) with less than a 1 in 1000 (0.1%) annual probability of fluvial or tidal flooding in any year. Refer to CEC Figure 4694/500/Figure 2 [Flood Zone Map] in Appendix Technical Guidance to the NPPF (Table 2: Flood Risk Vulnerability Classification) classifies the proposed site usage commercial as Less Vulnerable development. In accordance with the Technical Guidance to the NPPF (Table 3: Flood Risk Vulnerability and Flood Zone Compatibility), More Vulnerable developments are appropriate in Flood Zone Fluvial/tidal flood risk to the site is therefore low. Overland Runoff 3.6 The land in the immediate vicinity of the site is a largely undeveloped catchment including farmland and residential gardens. Surface water flows from this area will be limited to relatively minor greenfield runoff. The existing impermeable catchment within the site, along with the new buildings and hard paved areas will be directed to a new Sustainable Urban Drainage System (SUDS). This facility will accommodate any surface water runoff generated by the site, and will be designed with the capacity to contain the 1% + CC storm, in accordance with NPPF requirements. Refer to Section 4 below. 3.7 Mapping within the Strategic Flood Risk Assessment indicates that there is no record of surface water flooding at the site. Instances of highway flooding have been recorded on Corsham road and the A350, to the east of the site. It is assumed that this flooding was a result of heavy rainfall and inadequate highway drainage infrastructure or blockage of the highway drainage system. Comparison of existing road levels with those within the site QMF ISSUE 5 Cole Easdon Consultants (CEC) 7 OCTOBER 2015

11 FLOOD RISK ASSESSMENT PROPOSED EXPANSION OF WHITEHALL GARDEN CENTRE, CORSHAM ROAD, LACOCK confirms that any floodwaters in the highway would follow the road gradient to the south without accumulating to depth or encroaching upon the site, which is elevated relative to the road. Refer to Appendix 5 for report excerpts. Refer to CEC Plan 4694/500(A) [Existing Site Plan Sheets 1 & 2] in Appendix Note that there will be no discharge of surface water into the existing highway drainage system as a result of the proposals. The proposed redevelopment will not therefore exacerbate any existing highway drainage issues. Refer to Section 4 below. 3.9 Flood risk from overland flows is therefore low. Sewer Flooding 3.10 Wessex Water records confirm that there is a public foul sewer located in the in Corsham Road which follows the northern and eastern boundaries of the site. This sewer is under the management of the sewerage undertaker and should therefore be properly designed and maintained. If the sewer system were to surcharge and flood, it is likely that floodwaters would be contained within the highway corridor and would flow away from the site, to the south The existing private surface water drainage system should also be capable of accommodating runoff from the existing impermeable catchment within the site, without flooding. Notwithstanding this, the SUDS drainage provided as part of the redevelopment scheme will be designed with capacity for the 1%+CC storm in accordance with NPPF guidance There is no record of sewer flooding at the site, or in its vicinity, within the Strategic Flood Risk Assessment. Refer to Appendix 5 for report excerpts The risk of flooding from existing sewers is low. Groundwater Flooding 3.14 There is no record of groundwater flooding at the site, or in its vicinity, within the Strategic Flood Risk Assessment. Refer to Appendix 4 for report excerpts. QMF ISSUE 5 Cole Easdon Consultants (CEC) 8 OCTOBER 2015

12 FLOOD RISK ASSESSMENT PROPOSED EXPANSION OF WHITEHALL GARDEN CENTRE, CORSHAM ROAD, LACOCK 3.15 Groundwater levels are unknown at present, however the water table is probably in hydraulic continuity with the base of the valley of the unnamed watercourse and gully to the south west of the site, which is considerably lower than the lowest part of the site. In view of this it is unlikely that groundwater levels could rise sufficiently to cause flooding. In the event that groundwater emergence would ever occur within the site, it would drain off site, to the south, without accumulating to depth within the development The risk of groundwater flooding is low. QMF ISSUE 5 Cole Easdon Consultants (CEC) 9 OCTOBER 2015

13 FLOOD RISK ASSESSMENT PROPOSED EXPANSION OF WHITEHALL GARDEN CENTRE, CORSHAM ROAD, LACOCK 4.0 PROPOSED DRAINAGE STRATEGY Surface Water Refer to CEC Plan 4694/501(A) [Proposed Drainage Strategy Sheets 1 & 2] in Appendix Post development runoff will be discharged to the existing ditch at the site s southern boundary, as per the current arrangement. 4.2 The impermeable area at the site will be increased from 23,000m 2 to 46,500m 2 under the proposals, which will result in an increased surface water runoff rate. Without appropriate mitigation measures, this runoff could increase flood risk to the locality. 4.3 It is therefore proposed that post development discharge is reduced to the site s undeveloped, greenfield runoff rate. A 1 in 100 year greenfield runoff rate of 12 l/s has been calculated for the site. Refer to ICP for SuDS - IH124 Methodology Microdrainage software calculations in Appendix 3. The proposed flow restriction will ensure that there is no increase risk of flooding to downstream areas, and will in fact provide betterment over the existing situation, whereby surface water runoff from the site is discharged at an uncontrolled rate, and no storage system is present. 4.4 In accordance with NPPF guidance, on site Sustainable Urban Drainage Systems (SUDS) will be provided and will contain capacity for flows from the 1 in 100 year storm event, including an extra allowance of 30% to accommodate the predicted future impact of climate change upon rainfall patterns. 4.5 Preliminary calculations indicate that approximately 5,000m 3 on site storage will be required to accommodate the design storm. It is proposed that this volume is provided within a cellular storage SUDS system, such as Aquacell or similar approved, to be installed in the south western corner of the site, beneath the proposed car parking area. The proposed SUDS system layout is shown on CEC Plan 4694/501(A) [Proposed Drainage Strategy Sheets 1 & 2], enclosed within Appendix 6, together with a proposed surface water drainage network design. Calculations relating the drainage system can be found in Appendix 3. All calculations have been undertaken using Windes Microdrainage software. 4.6 Post development flows will be restricted by means of a hydrobrake, orifice or similar flow control device. QMF ISSUE 5 Cole Easdon Consultants (CEC) 10 OCTOBER 2015

14 FLOOD RISK ASSESSMENT PROPOSED EXPANSION OF WHITEHALL GARDEN CENTRE, CORSHAM ROAD, LACOCK Adoption 4.7 The SUDS system will be managed privately as part of the overall maintenance regime of the site. 4.8 Maintenance should be carried out in accordance with CIRIA SUDS MANUAL (2007) guidance, as shown in Table 4.1 below: Table 4.1: Maintenance Schedule Cellular Storage Operation and Maintenance Requirements Required Action Recommended Frequency Inspect and identify any areas that are not operating correctly. If required, take remedial action. Monthly for 3 months, then six monthly. Regular Maintenance Debris removal from catchment surface (where may cause risks to performance). Where rainfall infiltrates into blocks from above, check surface of filter for blockage by silt, algae or other matter. Remove and replace surface infiltration medium as necessary. Remove sediment from pre-treatment structures. Monthly. Monthly (and after large storms). Annually, or as required. Remedial Actions Monitoring Repair/rehabilitation of inlets, outlets, overflows and vents. Inspect/check all inlets, outlets, vents and overflows to ensure that they are in good condition and operating as designed. As required. Annually and after large storms. Water Quality 4.9 A bypass separator will be installed up stream of the proposed SUDS system. This will provide water quality treatment for runoff from the highway and parking areas, which could contain hydrocarbon pollutants from fuel and oil leaks or spillage. Further management of water quality will be provided by trap gullies which will retain particulates and any adhering contaminants. Rainwater Harvesting Refer to CEC Plan 4694/501(A) [Proposed Drainage Strategy Sheets 1 & 2] in Appendix The garden centre uses substantial volumes of water for irrigation. Any reduction in reliance on potable water supply will be beneficial economically and in terms of the sustainability of the site. It is therefore proposed that a rainwater harvesting tank is situated in one of the southern service yards. The tank will operate as part of the proposed surface water pipe network as an on line facility. The effective storage volume of the tank QMF ISSUE 5 Cole Easdon Consultants (CEC) 11 OCTOBER 2015

15 FLOOD RISK ASSESSMENT PROPOSED EXPANSION OF WHITEHALL GARDEN CENTRE, CORSHAM ROAD, LACOCK will be located beneath the invert level of the incoming and outgoing surface water drain such that when full the system will be by passed. Water will be removed for use by pumping The proposed tank volume is 555m 3 which is based on an average 2 weeks summer supply for year Refer to Appendix 3 for annual consumption figures. Foul Water Refer to CEC Plan 4694/501(A) [Proposed Drainage Strategy Sheets 1 & 2] in Appendix Foul flows from the site are presently disposed of by discharge to the existing public foul sewer in Corsham Road/A350. This arrangement will be maintained under the proposals As discussed in Section 2, at present 2No pump systems are employed to drain the site. It is proposed that a new piped gravity system be constructed to outfall to a new pumping station located in the south east corner of the site, on the southern side of the service road. Foul water will be pumped to the existing private chamber adjacent to the site s eastern boundary, from where it will gravitate to the existing public foul sewer The redevelopment scheme entails the addition of customer and staff lavatories, and kitchen waste water. The increase in loadings from these areas will be minimal and are not expected to impact upon the operation of the existing public foul sewer system. Any connection will be subject to Wessex Water approval at the appropriate time. QMF ISSUE 5 Cole Easdon Consultants (CEC) 12 OCTOBER 2015

16 FLOOD RISK ASSESSMENT PROPOSED EXPANSION OF WHITEHALL GARDEN CENTRE, CORSHAM ROAD, LACOCK 5.0 SUMMARY AND CONCLUSIONS 5.1 Flood risk to the proposed development from fluvial sources, overland flow, sewers and groundwater has been considered in this study. No significant risks have been identified. 5.2 The site lies within Flood Zone 1 (Low Risk) according to the FZM produced by the EA. As such, in accordance with NPPF guidance, redevelopment of the site for commercial purposes is appropriate. 5.3 Surface water discharge from the site is therefore the primary flood risk associated with the proposals. In order to mitigate flood risk from this source, post development flows will be restricted to the site s existing greenfield runoff rate; this represents significant betterment over the existing arrangement whereby flows from the extensive impermeable catchment within the garden centre are discharged without restriction. In addition, a large on site Sustainable Urban Drainage System is proposed in the form of a cellular tank facility. This will allow on site storage of flows arising from the 1 in 100 year event, including an allowance for future climate change, without increasing discharge to the receiving watercourse. 5.4 Rainwater harvesting will be employed to reduce the consumption of potable water for the purposes of irrigation and to improve the overall sustainability of the site. A tank will be provided in the southern service yard and will enable storage of 555m 3 of water, or 2 weeks average summer supply. 5.5 Post development foul flows will be discharge to the existing public foul sewer in Corsham Road/A350, as per the existing situation. The existing foul drainage system and pumps will be replaced with a new pipe network and a new pumping station. 5.6 This study has been undertaken in accordance with the principles of the NPPF document. We conclude that providing the development adheres to the conditions advised within this report, the proposals can be accommodated without increasing flood risk within the locality in accordance with objectives set by Central Government and the EA. Cole Easdon Consultants Limited October 2015 QMF ISSUE 5 Cole Easdon Consultants (CEC) 13 OCTOBER 2015

17 Appendix 1

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20 Appendix 2

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23 Appendix 3

24 Cole Easdon Consultants Page 1 York House, Edison Park Dorcan Way Swindon, SN3 3RB Date 21/09/ :41 Designed by sstarr File 4694 SW NETWORK.MDX Checked by Elstree Computing Ltd Network STORM SEWER DESIGN by the Modified Rational Method Design Criteria for Storm Pipe Sizes STANDARD Manhole Sizes STANDARD FSR Rainfall Model - England and Wales Return Period (years) 100 Add Flow / Climate Change (%) 0 M5-60 (mm) Minimum Backdrop Height (m) Ratio R Maximum Backdrop Height (m) Maximum Rainfall (mm/hr) 50 Min Design Depth for Optimisation (m) Maximum Time of Concentration (mins) 30 Min Vel for Auto Design only (m/s) 1.00 Foul Sewage (l/s/ha) Min Slope for Optimisation (1:X) 500 Volumetric Runoff Coeff Designed with Level Soffits Time Area Diagram for Storm Time (mins) Area (ha) Time (mins) Area (ha) Time (mins) Area (ha) Total Area Contributing (ha) = Total Pipe Volume (m³) = Network Design Table for Storm PN Length (m) Fall (m) Slope (1:X) I.Area (ha) T.E. (mins) Base Flow (l/s) k (mm) HYD SECT DIA (mm) Auto Design o o o o o o o 825 Network Results Table PN Rain (mm/hr) T.C. (mins) US/IL (m) Σ I.Area (ha) Σ Base Flow (l/s) Foul (l/s) Add Flow (l/s) Vel (m/s) Cap (l/s) Flow (l/s) XP Solutions

25 Cole Easdon Consultants Page 2 York House, Edison Park Dorcan Way Swindon, SN3 3RB Date 21/09/ :41 Designed by sstarr File 4694 SW NETWORK.MDX Checked by Elstree Computing Ltd Network Network Design Table for Storm PN Length (m) Fall (m) Slope (1:X) I.Area (ha) T.E. (mins) Base Flow (l/s) k (mm) HYD SECT DIA (mm) Auto Design o o o o o o o o o o o o o o o o o 900 Network Results Table PN Rain (mm/hr) T.C. (mins) US/IL (m) Σ I.Area (ha) Σ Base Flow (l/s) Foul (l/s) Add Flow (l/s) Vel (m/s) Cap (l/s) Flow (l/s) XP Solutions

26 Cole Easdon Consultants Page 3 York House, Edison Park Dorcan Way Swindon, SN3 3RB Date 21/09/ :41 Designed by sstarr File 4694 SW NETWORK.MDX Checked by Elstree Computing Ltd Network Free Flowing Outfall Details for Storm Outfall Pipe Number Outfall Name C. Level (m) I. Level (m) Min I. Level (m) D,L (mm) W (mm) Simulation Criteria for Storm Volumetric Runoff Coeff Additional Flow - % of Total Flow Areal Reduction Factor MADD Factor * 10m³/ha Storage Hot Start (mins) 0 Inlet Coeffiecient Hot Start Level (mm) 0 Flow per Person per Day (l/per/day) Manhole Headloss Coeff (Global) Run Time (mins) 60 Foul Sewage per hectare (l/s) Output Interval (mins) 1 Number of Input Hydrographs 0 Number of Storage Structures 1 Number of Online Controls 1 Number of Time/Area Diagrams 0 Number of Offline Controls 0 Number of Real Time Controls 0 Synthetic Rainfall Details Rainfall Model FSR Profile Type Summer Return Period (years) 100 Cv (Summer) Region England and Wales Cv (Winter) M5-60 (mm) Storm Duration (mins) 30 Ratio R XP Solutions

27 Cole Easdon Consultants Page 4 York House, Edison Park Dorcan Way Swindon, SN3 3RB Date 21/09/ :41 Designed by sstarr File 4694 SW NETWORK.MDX Checked by Elstree Computing Ltd Network Online Controls for Storm Hydro-Brake Optimum Manhole: 24, DS/PN: 1.012, Volume (m³): 83.2 Unit Reference MD-SHE Design Head (m) Design Flow (l/s) 12.0 Flush-Flo Calculated Objective Minimise upstream storage Diameter (mm) 143 Invert Level (m) Minimum Outlet Pipe Diameter (mm) 225 Suggested Manhole Diameter (mm) 1500 Control Points Head (m) Flow (l/s) Design Point (Calculated) Flush-Flo Kick-Flo Mean Flow over Head Range The hydrological calculations have been based on the Head/Discharge relationship for the Hydro-Brake Optimum as specified. Should another type of control device other than a Hydro-Brake Optimum be utilised then these storage routing calculations will be invalidated Depth (m) Flow (l/s) Depth (m) Flow (l/s) Depth (m) Flow (l/s) Depth (m) Flow (l/s) XP Solutions

28 Cole Easdon Consultants Page 5 York House, Edison Park Dorcan Way Swindon, SN3 3RB Date 21/09/ :41 Designed by sstarr File 4694 SW NETWORK.MDX Checked by Elstree Computing Ltd Network Storage Structures for Storm Tank or Pond Manhole: 24, DS/PN: Invert Level (m) Depth (m) Area (m²) Depth (m) Area (m²) Depth (m) Area (m²) XP Solutions

29 Cole Easdon Consultants Page 6 York House, Edison Park Dorcan Way Swindon, SN3 3RB Date 21/09/ :41 Designed by sstarr File 4694 SW NETWORK.MDX Checked by Elstree Computing Ltd Network Summary Wizard of 15 minute 1 year Summer I+0% for Storm Simulation Criteria Areal Reduction Factor Additional Flow - % of Total Flow Hot Start (mins) 0 MADD Factor * 10m³/ha Storage Hot Start Level (mm) 0 Inlet Coeffiecient Manhole Headloss Coeff (Global) Flow per Person per Day (l/per/day) Foul Sewage per hectare (l/s) Number of Input Hydrographs 0 Number of Storage Structures 1 Number of Online Controls 1 Number of Time/Area Diagrams 0 Number of Offline Controls 0 Number of Real Time Controls 0 Synthetic Rainfall Details Rainfall Model FSR Ratio R Region England and Wales Cv (Summer) M5-60 (mm) Cv (Winter) Margin for Flood Risk Warning (mm) DVD Status OFF Analysis Timestep Fine Inertia Status OFF DTS Status ON Profile(s) Summer and Winter Duration(s) (mins) 15, 30, 60, 120, 180, 240, 360, 480, 600, 720, 960, 1440, 2160, 2880, 4320, 5760, 7200, 8640, Return Period(s) (years) 1, 30, 100 Climate Change (%) 0, 0, 30 PN US/MH Name Rank Water Level (m) Surch'ed Depth (m) Flooded Volume (m³) Flow / Cap. O'flow (l/s) Pipe Flow (l/s) Status OK OK OK OK OK OK OK OK OK OK OK OK OK OK OK OK OK OK OK OK OK XP Solutions

30 Cole Easdon Consultants Page 7 York House, Edison Park Dorcan Way Swindon, SN3 3RB Date 21/09/ :41 Designed by sstarr File 4694 SW NETWORK.MDX Checked by Elstree Computing Ltd Network Summary Wizard of 15 minute 1 year Summer I+0% for Storm PN US/MH Name Rank Water Level (m) Surch'ed Depth (m) Flooded Volume (m³) Flow / Cap. O'flow (l/s) Pipe Flow (l/s) Status OK OK OK XP Solutions

31 Cole Easdon Consultants Page 8 York House, Edison Park Dorcan Way Swindon, SN3 3RB Date 21/09/ :41 Designed by sstarr File 4694 SW NETWORK.MDX Checked by Elstree Computing Ltd Network Rainfall Hyetograph for 15 minute 1 year Summer I+0% (Storm) Time (mins) Rain (mm/hr) Time (mins) Rain (mm/hr) Time (mins) Rain (mm/hr) Time (mins) Rain (mm/hr) Time (mins) Rain (mm/hr) XP Solutions

32 Cole Easdon Consultants Page 1 York House, Edison Park Dorcan Way Swindon, SN3 3RB Date 15/09/ :38 Designed by sstarr File Checked by Elstree Computing Ltd Source Control ICP SUDS Mean Annual Flood Input Return Period (years) 100 Soil Area (ha) Urban SAAR (mm) 766 Region Number Region 7 Results l/s QBAR Rural 3.7 QBAR Urban 3.7 Q100 years 11.8 Q1 year 3.1 Q30 years 8.4 Q100 years XP Solutions

33 WATER CONSUMPTION 2014/15 IRRIGATION UNIT MAINS UNIT PERIOD CONSUMPTION CUBIC METERS LACOCK 2/9/14-2/10/ /10/14-5/11/ /11/14-2/12/ /12/14-6/1/ /1/15-2/2/ /2/15-3/3/ /3/15-1/4/ /4/15-5/5/ /5/15-2/6/ /6/15-2/7/ /7/15-3/8/ /8/15-1/9/ ANNUAL WATER CONSUMPTION

34 Appendix 4

35