FLOOD RISK & DRAINAGE IMPACT ASSESSMENT REPORT

FLOOD RISK & DRAINAGE IMPACT ASSESSMENT REPORT

Higher College Farm, Hothersall, Preston

Report Ref BEK-17303-1-RevB November 2018

REPORT PREPARED FOR

MR M HURST Higher College Farmhouse

Lower Road Hothersall

Preston PR3 2YY

Project Quality Assurance Information Sheet

FLOOD RISK AND DRAINAGE IMPACT ASSESSMENT

Higher College Farm, Hothersall, Preston

Report Status Final

Report No BEK-17303-1

Rev No B

Date November 2018

Prepared For

MR M HURST Higher College Farmhouse

Lower Road Hothersall Preston, PR3 2YY

Prepared By

BEK ENVIRO LIMITED Suite One

No 3 Mitton Road Business Park Mitton Road

Whalley Lancashire

BB7 9YE

Author

David Emmott BSc (Hons) MSc AMIEnvSci

Checked By

Michael Buckley BSc (Hons) MSc MIEnvSci CEnv

Contact [email protected] www.bekenviro.co.uk

Office: 01254 377622 Mobile: 07906 753583 BEK Enviro Limited (BEK) 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 BEK. 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 BEK 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 BEK 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.

mailto:[email protected]

Flood Risk and Drainage Impact Assessment Higher College Farm, Hothersall Report Ref BEK-17303-1- RevB November 2018

TABLE OF CONTENTS

1. INTRODUCTION 1.1 Appointment

1.2 Background

1.3 Objective

1.4 Scope of Report

1.5 Limitations

2. DESKTOP STUDY 2.1 Site Location & Layout Plan

2.2 Topographical Survey

2.3 Existing Surface Water Flow Routes, Drains, Sewers and Watercourses

2.4 Flood Risk From Main Rivers

2.5 Surface Water and Groundwater Flood Risk

2.6 Geology and Soil Type

3. FLOOD RISK ASSESSMENT

3.1 Sequential and Exception Test

3.2 Historical Flooding

3.3 Surface Water Runoff

3.4 Fluvial Flooding

3.5 Reservoir Flooding

3.6 Groundwater

3.7 Surface Water

4. INDICATIVE DRAINAGE STRATEGY

4.1 Surface Water Drainage Hierarchy

4.2 Infiltration

4.3 Discharge to Watercourse

4.4 Preliminary Drainage Design

4.5 Outfall Locations

4.6 Discharge Rates

4.7 On-Site Storage Requirements

5. CONCLUSIONS & RECOMMENDATIONS

APPENDICES Appendix A Topographical Survey

Appendix B Greenfield Runoff Rates

Appendix C On-Site Storage Requirements

Appendix D Preliminary Drainage Design

Appendix E Drawings

Flood Risk and Drainage Impact Assessment Higher College Farm, Hothersall Report Ref BEK-17303-1- RevB November 2018

DRAWINGS BEK Drawing No 17303-1 Site Location Plan

BEK Drawing No 17303-2 Site Layout Plan

Flood Risk & Drainage Impact Assessment – Higher College Farm, Hothersall Report Ref BEK-17203-1 RevB November 2018

1. INTRODUCTION

1.1 Appointment

1.1.1 BEK Enviro Limited (BEK) has been commissioned by Mark Hurst to provide a Flood Risk & Drainage Impact Assessment for Higher College Farmhouse, Hothersall, Preston (hereafter referred to as ‘the site’) to assess the potential risks associated with flood risk to the site for residential use.

1.1.2 The site is located within Flood Zone 1 of the Environment Agency Flood Map;

and as such has a low risk of fluvial flooding.

1.2 Background

1.2.1 A site specific flood risk assessment provides an appraisal of flood risk both within the application site and any potential impact that the development will have on flood risk elsewhere; and provide recommendations for mitigation measures which may be included within the design of the development to reduce the overall risk of flooding.

1.2.2 An initial assessment indicates that the primary source of flooding risk to the

development is an increase in surface water runoff as a result of development. 1.3 Objective and Scope of Work 1.3.1 The objective of this report is to evaluate the issues in regard to flood risk at the

application site i.e. development of 21 new residential units at Higher College Farm, Hothersall, Preston, Lancashire.

1.3.2 The Flood Risk and Drainage Impact Assessment has been prepared to inform ‘An

outline planning application for a self-build residential scheme’. Specifically the following information is required as a minimum:

Detailed site location and layout plans Desktop study to incorporate maps showing:

Topography of the development site, with contours at 1 m intervals

Existing surface water flow routes, drains, sewers and watercourses

Flood risk from main river and coastal sources

Surface water and groundwater flood risk

Geological and soil types

Flood Risk Assessment:

Suitability of the proposed development in accordance with current planning policy

Identify the risk to both the development and people from all forms of flooding

Provide a preliminary assessment of foul and surface water management


Review the relevant background information for the site, including: o National Planning Policy Framework o Planning Practice Guidance o Building Regulations Approved Document H o Environment Agency Flood Mapping o Lancashire County Council Strategic Flood Risk Assessment (2007) o BGS – Historic Borehole Logs o Cranfield University Soilscape Viewer

Recommendation of appropriate measures to mitigate against flooding both within the proposed development, and neighbouring land and property.

Indicative Site Drainage Strategy, including:

Preliminary sustainable drainage proposals

Outfall Locations

Discharge Rates

On-site storage requirements

1.4 Scope of Report 1.4.1 The information provided within this report was undertaken via a desktop

investigation using the guidance provided by Lancashire County Council in their Pre-Application Advice.

1.4.2 This report provides details of the information requested by Lancashire County

Council to demonstrate how surface water will be managed on site, satisfying the principles of Paragraph 103 of the NPPF and Paragraph 80 of Section 10 of the PPG (Planning Policy Guidance).

1.5 Limitations 1.5.1 The conclusions and recommendations presented in this report are the result of

our professional interpretation of the information currently available. BEK reserve the right to amend the conclusions and recommendations if further information becomes available.

1.5.2 However, it should be noted that much of the information has been derived from

various internet resources and BEK takes no responsibility for the accuracy of that information.

1.5.3 The comments given in this report and the opinions expressed are based on

review of information obtained by BEK.


2. DESKTOP STUDY 2.0.1 This section provides an overview of the information to satisfy the requirements

of Lancashire County Council in their role as Lead Local Flood Authority (LLFA). 2.1 Site Location and Layout Plan 2.1.1 The site occupies a roughly rectangular plot of agricultural land of some 1.5

Hectares (11,000 m2). The site generally falls towards the south and is currently comprised of a large agricultural field. Higher College Farmhouse and associated farm buildings are located towards the south of the site.

2.1.2 Detailed site location and layout plans are provided within Appendix E of this

report. 2.2 Topographical Survey 2.2.1 A topographical survey of the site was completed by TriCAD Solutions Ltd in May

2017 and is provided within Appendix A of this report. The site is shown to fall from north to south with the general site level shown to be around 110 mAOD.

2.2.2 The highest spot level on the topographical survey is in the north-east of the site

and is shown to be 112.23 mAOD with the lowest spot level in the south-west of the site with an elevation of 106.60 mAOD.

2.3 Existing Surface Water Flow Routes, Drains, Sewers and Watercourses 2.3.1 The existing development site is comprised of an agricultural greenfield. The

agricultural field is not anticipated to have any formal drains or sewers. There is a small existing watercourse located approximately 20 m south-west of the development site.

2.3.2 It is considered that the existing farmhouse immediately south of the site is

positively drained with surface water likely to drain towards an unnamed land drain located to the south-west of the site and foul from the existing farmhouse is likely to discharge into a septic tank.

2.3.3 There a number of manholes, inspection chambers and gullies located close to

the existing farmhouse building with surface water directed towards the lowest part of the site in the south-west.

2.3.4 A surface water flow route is located towards the west of the site which flows

from adjacent to the west of Spade Mill Reservoir No 2 in a southerly direction beneath Blackburn Road and adjacent to the west of the development site. It is understood the land drain is culverted as it flows along the western boundary of the site before becoming an open channel approximately 30 m south-west of the site.


2.4 Flood Risk from Main Rivers 2.4.1 The Environment Agency flood map indicates that the development site is

located wholly within Flood Zone 1 as shown within the Figure overleaf. Flood Zone 1 is defined as land with a low probability (less than 1 in 1000 year (<0.1% AEP) annual probability of river or sea flooding in any year.

2.4.2 As such the risk of Main River and coastal flooding to the development site is

considered to be low.

Figure 1: Environment Agency Flood Map Key

2.5 Surface Water and Groundwater Flood Risk 2.5.1 Figure 2 below indicates that the risk of flooding from surface water to the

development site is very low to low. 2.5.2 However there is a surface water flow route which flows in a southerly direction

to the west of the site. The depth of flooding from this surface water flow route during the low risk event is below 300 mm adjacent to the development site.

Development Site


Figure 2 : Environment Agency Flood Risk from Surface Water Map Key

High Medium Low Very Low

2.5.3 The risk of groundwater flooding to the site is considered to be low with the

Environment Agency Groundwater Designation Map indicating that the site is underlain by superficial deposits classified as a ‘Secondary Undifferentiated Aquifer’.

2.5.4 The Environment Agency describes Secondary undifferentiated aquifers as: ‘Undifferentiated aquifers has been assigned where it has not been possible to

attribute either category A or B to a rock type. In most cases, this means that the layer in question has previously been designated as both minor and non-aquifer in different locations due to the variable characteristics of the rock type’

Development Site


Figure 3: Environment Agency Groundwater (Superficial Deposits)

Key

2.5.5 The bedrock aquifer designation is shown within the Figure below with the site shown to be located on bedrock classified as a ’Secondary A Aquifer’ described as:

‘permeable layers capable of supporting water supplies at a local rather than

strategic scale, and in some cases forming an important source of base flow to rivers. These are generally aquifers formerly classified as minor aquifers’

Site


Figure 4: Environment Agency Groundwater (Bedrock Deposits)

Key

2.5.6 Due to the location of the site on an undifferentiated secondary superficial

aquifer with a bedrock designation as a Secondary A aquifer it is not considered likely that groundwater flooding would pose a significant risk to the proposed site. Furthermore the Ribble Valley Strategic Flood Risk Assessment states that:

‘Groundwater flooding is not considered by the Environment Agency to be a

significant flood risk factor in the Ribble Valley Borough Council area.’ 2.6 Geology and Soil Type 2.6.1 Information from the British Geological Society indicates that the bedrock

geology at the development site is comprised of the Warley Wise Grit Member consisting of sandstones with part of the north of the site shown to be the Pendle Grit Member consisting of sandstone and siltstone.

Site


Figure 5: BGS Bedrock Deposits

2.6.2 The superficial geology is Till, Devensian – Diamicton (Boulder Clay). The soil type

beneath the development site is considered to be slowly permeable seasonally wet acid loamy and clayey soils with impeded drainage.

Figure 6: Soilscapes Viewer

Key

Site

Site


3. FLOOD RISK ASSESSMENT

3.0.1 It is usual for the Environment Agency to raise an objection to development applications within the floodplain, or Zones 2 and 3 of the Environment Agency flood map until the issue of flood risk has been properly evaluated. The Agency will also object to developments where the total site area is in excess of 1 Hectare until suitable consideration has been given to surface water runoff.

3.0.2 The proposed development site is located wholly within Flood Zone 1 however it

is greater than 1 hectare in size as such it is considered that a Site Specific Flood Risk Assessment is required.

3.1 Sequential and Exception Test 3.1.1 The objective of the Sequential Test is to steer new development to areas of the

lowest probability of flooding, this takes into account the flood zones and the flood risk vulnerability classification of developments.

3.1.2 The Environment Agency flood map indicates that the proposed development

site is within Flood Zone 1. Flood Zone 1 is defined as land assessed as having a less than 1 in 1000 annual probability of river flooding in any one year.

3.1.3 Proposals for the application site are for the development of new residential units

at the site. 3.1.4 In accordance with Table 2 ‘Flood Risk Vulnerability Classification’ of the

Technical Guidance to the National Planning Policy Framework, commercial developments are defined as ‘more vulnerable’ development.

Flood Risk Vulnerability Classification

Essential Infrastructure

Water Compatible

Highly Vulnerable

More Vulnerable

Less Vulnerable

Flood Zone

Zone 1

Zone 2

Exception

Test Required

Zone 3a

Exception Test Required

x Exception

Test Required

Zone 3b

Exception Test Required

x x x

Table 1: Flood Risk Vulnerability and Flood Zone Compatibility


3.1.5 ‘More Vulnerable’ developments within Flood Zone 1 are considered appropriate development. As such it is not considered that the undertaking of a Sequential/Exception Test will be required.

3.2 Historical Flooding 3.2.1 An internet search of flooding in the Hothersall area did not result in any results

however it is acknowledged that the area is essentially rural therefore historical incidents of flooding may not have been recorded.

3.2.2 A review of Ribble Valley Borough Council Strategic Flood Risk Assessment

indicates that there have been a number of historical flood event in the Ribble Valley area however Hothersall or Longridge are not referenced as having flooded.

3.2.3 A number of flooding incidents have been recorded in Ribchester located some

3.8 km south-east of the site however due to the distances involved it is not considered that the site has experienced flooding.

3.3 Surface Water Runoff 3.3.1 The proposed development site is over 1 Hectare in size therefore surface water

runoff will need to be adequately assessed in order to ensure flood risk at the site and elsewhere is not increased as a result of development.

3.3.2 Surface water runoff will be assessed in more detailed in Section 4 of this report. 3.4 Fluvial Flooding 3.4.1 As mentioned previously within Section 2.4 of this report the site is located within

Flood Zone 1 of the Environment Agency flood map. 3.4.2 Flood Zone 1 is defined as land with a low probability (less than 1 in 1000 year

(<0.1% AEP) annual probability of river or sea flooding in any year. 3.4.3 As such the risk to the site from fluvial flooding is considered to be low. 3.5 Reservoir Flooding 3.5.1 The Environment Agency Flooding from Reservoirs map identifies that the

proposed development is within the extent of flooding following a breach of a reservoir.


Figure 6: EA Flood Risk From Reservoir

3.5.2 There are two reservoirs located in close proximity to the site located some 45 m

north of the site at the closest point. The reservoirs are known as Spade Mill Reservoir No 1 and No 2 and are owned by United Utilities.

3.5.3 It is noted that reservoir flooding is extremely unlikely to happen. There has been

no loss of life in the UK from reservoir flooding since 1925. All large reservoirs are regularly inspected by reservoir panel engineers and the EA ensures that reservoirs are regularly inspected and essential safety work is undertaken as appropriate. As such the risk of flooding from this source is considered to be low.

3.6 Groundwater 3.6.1 As mentioned in Section 2.5 of this report the site is underlain by superficial

deposits comprising Boulder Clay and bedrock deposits of the Warley Wise Grit Member.

3.6.2 The superficial deposits are classified by the Environment Agency as a ‘Secondary

Undifferentiated Aquifer’. 3.6.3 The bedrock aquifer designation is classified as a ’Secondary A Aquifer’. 3.6.4 Due to the location of the site on an undifferentiated secondary superficial

aquifer with a bedrock designation as a Secondary A aquifer it is not considered likely that groundwater flooding would pose a significant risk to the proposed site. Furthermore the Ribble Valley Strategic Flood Risk Assessment states that:

‘Groundwater flooding is not considered by the Environment Agency to be a

significant flood risk factor in the Ribble Valley Borough Council area.’

Site


3.6.5 As such the risk to the site from groundwater flooding is considered to be low. 3.7 Surface Water 3.7.1 As mentioned in Section 2.5 of this report the risk of surface water flooding to

the site is considered to be very low to low with a surface water flow route located to the west of the site. As such the risk to the proposed development is considered to be low.


4. INDICATIVE DRAINAGE STRATEGY 4.1 Surface Water Drainage Hierarchy 4.1.1 The hierarchy for disposal of surface water from new developments is outlined

within the Building Regulations Approved Document H and specifies the following methods in order of preference:

Infiltration via soakaway or other suitable infiltration device

Discharge to watercourse

Discharge to public sewer

4.2 Infiltration 4.2.1 Soilscapes viewer maps show that the site is situated on slowly permeable

seasonally wet clayey and loamy soils. These types of soils would generally be unsuitable dissipation of surface water via infiltration.

4.2.2 Although considered very unlikely to be viable, the Lead Local Flood Authority

may request additional evidence that the infiltration is unviable at the site. This can be provided by completing a percolation test in accordance with DG 365 (2016) as part of a detailed drainage design.

4.3 Discharge to Watercourse 4.3.1 The nearest watercourse to the site is a land drain which flows along the western

boundary of the site in a southerly direction, it is understood that the land drain is culverted along the west of the site. The watercourse eventually discharges into the River Ribble some 3.7 km south of the site.

4.3.2 It is proposed that surface water is discharged into this land drain at existing

greenfield runoff rates. 4.4 Preliminary Drainage Design 4.4.1 The purpose of this assessment is to demonstrate that a surface water drainage

strategy is feasible for the development proposals and land available. 4.4.2 The existing site is comprised of a large agricultural field. Therefore flows leaving

the development site will be restricted to existing greenfield runoff rates using a flow control; and excess flows must be attenuated within the new drainage system prior to discharge into the land drain/culverted watercourse which runs adjacent to the west of the site.

4.4.3 It is proposed that foul from the residential dwellings buildings will be pumped

to a receiving foul sewer located towards the north of the site. The foul sewer


has been constructed as part of a new residential development off Dilworth Lane to the north of the site.

4.4.4 A preliminary drainage strategy is included within Appendix D of this report. 4.5 Outfall Locations 4.5.1 The hierarchy of surface water disposal states that surface water should be

discharged into watercourse as discharge via infiltration is unlikely to be viable. The nearest watercourse is a land drain which flows towards the south located to the south-west of the development site.

4.5.2 As such the outfall from the site will be located to the west or south-west into

the existing land drain which eventually discharges into the River Ribble some 3.7 km south of the site.

4.6 Discharge Rates 4.6.1 The existing site is wholly comprised of an agricultural greenfield. 4.6.2 Greenfield runoff rate limits are required to meet normal Greenfield runoff rate

limits are required to meet normal best criteria in line with the Environment Agency Guidance “Preliminary rainfall runoff management for developments”, W5-074/A/TR1/1 Rev. E (2012) and the CIRIA SUDS Manual (2007).

4.6.3 Utilising the HR Wallingford Greenfield Runoff Estimation for Sites website

greenfield runoff rates have been calculated for the 1 in 1 year, 1 in 30 year and 1 in 100 year return periods, and a summary of the results is tabulated below.

4.6.4 Flows in excess of this must be attenuated within the boundary of the

development prior to disposal.

Return Period Qbar Peak Flow Rate Site

1 in 1 year

10.1

8.79

1 in 30 year 17.17

1 in 100 year 21.01

Table 2: Existing Surface Water Runoff (1.13 Hectares) 4.7 On-site Storage Requirements 4.7.1 The proposed development site is comprised of 21 new residential dwellings and

associated hardstanding comprising a total impermeable area of 0.56 Hectares which represents 49.6% of the total site area.

4.7.2 Using the Surface Water Storage Requirement module on HR Wallingford

website indicative attenuation volumes for the 1 in 100 year event has been


calculated below. An additional 20% and 40% has been added to account for climate change over the lifetime of the development.

Return Period Indicative Attenuation Volumes (m3)

No Climate Change 20% Climate

Change 40% Climate

Change

1 in 100 year 201 290 378

Table 3: Indicative Attenuation Volumes (0.56 Hectares Impermeable) 4.7.3 The figures calculated above are indicative at this stage of the project and are

subject to change following the results of percolation testing at the development site, and must not be used for detailed design purposes.

4.7.4 As such it is considered that a geocellular storage tank of 24 m x 11 m and a depth

of 1.6 m at 95% porosity would be sufficient to attenuate flows on site for the 1 in 100 year plus 40% climate change rainfall event prior to discharge at greenfield runoff rate.

4.7.5 Alternatively, a mixture of attenuation and SUDS structures such as oversized

pipes, swales, permeable paving and attenuation storage tanks could be utilised within the site to attenuate surface water prior to discharge.

4.7.6 It is noted that the current proposed site plans indicate that geocellular storage

tanks could be located within the public open space of the site, alternatively private driveways could potentially be constructed from permeable paving, oversized pipes could be utilised beneath the roads within the site and swales could be utilised within the grassed areas of the site.


5. CONCLUSION AND RECOMMENDATIONS

5.1 The proposed development at Higher College Farm, Hothersall comprises the development of 21 residential dwellings and associated infrastructure and landscaping.

5.2 The site is shown to be located within Flood Zone 1 of the Environment Agency

Flood map. 5.3 The primary source of flood risk to the site is identified to be from an increase in

surface water runoff as a result of development. 5.4 Environment Agency surface water flood maps indicate the site is at very low risk

of surface water flooding with a surface water flow route adjacent to the west of the site. It is considered that the surface water flow route is an existing unnamed watercourse/land drain and the risk of flooding from this source to the development is considered to be low.

5.5 The site is within an area that would experience flooding following a breach of

the reservoirs located to the north of the site, however reservoir flooding is extremely unlikely to happen and the EA undertake routine inspection of reservoirs to ensure the risks of failure are low. As such this is considered to represent a low risk of flooding to the site.

5.5 The risks from secondary sources of flooding such as groundwater flooding, river

flooding and artificial water sources have been investigated and are deemed to present a low risk of flooding to the site.

5.6 The site is comprised of an agricultural greenfield therefore greenfield runoff

rates have been determined using IOH124 method. 5.7 Greenfield runoff rates have been determined to be 8.79 l/s, 17.17 l/s and 21.01

l/s for the 1 in 1 year, 1 in 30 year and 1 in 100 year return periods respectively. 5.8 It is considered that infiltration at the site is unlikely to be viable due to the

underlying boulder clay at the site therefore following the hierarchy of surface water disposal, it is recommended that surface water is discharged into the unnamed watercourse/land drain to the west of the site.

5.9 Surface water attenuation requirements have been determined using the limiting

greenfield discharge rate for the site. The maximum attenuation storage required is 378 m3 however this is subject to change following production of a detailed drainage design for the site.

5.10 Therefore the proposed development would be able to manage surface water

generated as a result of the development and would not increase flood risk at the development site or downstream of the site.

APPENDIX A

Topographical Survey

1

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1

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113.6

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107.20

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107.37

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FFL107.38

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107.28

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111.11

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113.65

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112.40

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111.71

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111.02

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110.40

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111.03

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111.05

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109.59

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1

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107.35

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107.4

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106.7

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106.72

106.70

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109.59

106.8

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107.20

106.6

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106.7

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107.89

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107.8

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108.8

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106.61

107.01

107.22

107.0

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107.2

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107.45

107.3

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106.80

106.96

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113.09

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110.4

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113.6

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112.1

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109.31

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111.03

EH

110.39

107.49

107.47

107.50

107.48

107.49

107.65

107.70

107.91

107.94

108.18

108.19

CL108.09

108.1

2

108.17

108.2

1

108.2

1

108.641

0

8

.

3

3

TL

10

8.3

1

108.12

10

8.1

0

107.98

10

8.1

5

10

8.1

1

RH110.86

EH110.64

108.42

108.08

108.11

108.14

108.10

CL108.05

108.0

8

TL108.2

7

1

0

8

.

1

0

108.12

TL108.26

TL108.11

CL108.05

108.08

CL108.06

CL108.07

1

0

8

.

0

8

STONE FLAGS

107.64

1

0

7

.

6

4

1

0

7

.

6

9

1

0

7

.

9

7

1

0

8

.

0

8

1

0

7

.

6

2

1

0

7

.

5

3

1

0

7

.9

4

108.09

108.0

8

107.9

5

1

0

7

.

5

2

107.5

3

CL107.40

107.4

5

TL107.5

1

107.5

2

CL107.44

CL107.44

CL107.43

107.5

4

107.5

4

107.37

CH

IPP

ING

S

W

OO

D C

HIP

PIN

GS

107.5

1

107.4

8

107.4

6

CL107.41

STONE FLAGS

STONE FLAGS

GRASS

1

0

8

.3

9

1

0

8

.

3

7

1

0

8

.

4

1

1

0

8

.

8

4

108.6

0

108.5

9

108.4

8

108.6

4

1

0

8

.7

4

108.4

1

108.2

1

108.1

8

108.4

3

108.1

6

108.1

6

108.1

3

EH

110.4

2

108.43

108.45

108.57

CHIPPINGS

1

0

7

.

9

8

108.02

107.80

107.81

1

0

8

.

6

6

108.80

108.50

108.53

1

0

8

.5

5

1

0

8

.6

3

108.62

1

0

8

.6

4

109.2

5

109.1

9

109.0

4

1

0

8

.

5

6

1

0

8

.5

0

1

0

8

.4

5

108.65

1

0

8

.7

3

1

0

9

.

0

1

109.15

1

0

9

.

2

4

1

0

9

.3

7

1

0

9

.

2

6

1

0

9

.

0

4

R

H

115.23

1

0

8

.7

7

108.89

1

0

9

.0

7

1

0

9

.1

5

1

0

9

.2

9

1

0

9

.4

3

1

0

9

.3

4

1

0

9

.3

1

1

0

9

.

2

2

1

0

8

.

8

5

1

0

8

.

3

5

1

0

8

.

2

6

108.1

3

108.2

2

Vent

108.3

2

108.6

7

108.7

9

108.8

1

1

0

8

.5

8

108.34

CL109.42

109.1

6

109.3

5

109.4

5

109.3

7

109.2

7

109.0

0

108.5

8

109.1

0

109.2

9

109.3

6

109.4

5

109.3

7

109.3

8

109.2

3

109.2

0

109.2

8

109.2

2

109.4

0

109.5

3

109.5

8

109.5

5

109.5

7

109.3

7

109.6

4

109.8

5

109.9

4

109.8

9

109.8

6

109.6

2

1

0

8

.8

2

1

0

9

.0

8

1

0

9

.3

7

1

0

9

.0

4

1

0

7

.0

0

m

107.00m

1

0

8

.

0

0

m

1

0

8

.0

0

m

109.00m

1

0

9

.

0

0

m

Hedge

Hedge

Post &

Panel F

ence

H

e

d

g

e

Hedge

H

edge

H

edge

Hedge

P

ost &

W

ire F

ence

Post &

W

ire F

ence

Post &

W

ire F

ence

Post &

W

ire F

ence

Post &

W

ire F

ence

Hedge

H

edge

Hedge

H

e

d

g

e

H

e

d

g

e

H

e

d

g

e

H

e

d

g

e

H

e

d

g

e

CHIPPINGS

CHIPPINGS

CHIPPINGS

Hedge

Hedge

Hedge

H

e

d

g

e

H

e

d

g

e

Reta

inin

g W

all

R

eta

inin

g W

all

R

e

t

a

i

n

i

n

g

W

a

l

l

R

e

t

a

i

n

i

n

g

W

a

l

l

MH

IC

IC

GU

GU

GU

GU

IC

IC

IC

IC

IC

IC

IC

GU

GU

GU

GU

GU

GU

R

e

t

a

i

n

i

n

g

W

a

l

l

GRASS

GRASS

GRASS

GU

MH

MH

GU

Vegetation

Post &

W

ire F

ence

GU

GU

E

H

1

0

9

.

1

9

BBQ

Gully C

hannel

W

a

l

l

W

a

l

l

Wall

W

all

W

all

W

all

GU

MH

GU

MH

GU

108.00m

1

0

8

.0

0

m

Site Address

Project Description

Drawing Title

Scale Date Drawn By

Drawing Number

Rev. Description.

Notes

All Dimensions to be checked on site. Walls shown on

plans are not to be assumed to be solid & should be

checked for thickness, construction, load bearing capacity

& stability.

The contents of this drawing and entities used are copyright TriCAD Solutions Ltd 2010 ©

Higher College Farm

Lower Road

Hothersall PR3 2YY

Site Survey

Existing Site Layout

1:200@A1 30/05/2017 MW

TRI-2005-01

0 Issued

North

0 2 4 6 8 10 12 14 16 18 20Metres

Top of WallTW

Man Hole

Telegraph Pole

Gully

Cover Level

MH

TP

GU

CL

Ridge/Roof HeightRH

Eaves HeightEH

Finished Floor LevelFFL

BT CoverBT

Water ValveWV

Sign PostSP

Soil Vent PipeSVP

Inspection CoverIC

Threshold LevelTL

Cable HeightCH

NOTE

All levels and coordinates relate to OSGB36(15) using GNSS data.

Levels defining edge of carriageway are observed at channel (bottom

of kerb).

Top of FenceTF

BollardBOL

Top of HedgeTH

ABBREVIATIONS

Drop KerbDK

1

23

109.46

109.91

1

1

0

.1

8

110.53

110.86

110.86

111.20

1

1

1

.1

7

1

1

1

.4

4

111.62

1

1

1

.8

7

112.11

112.23

112.19

112.25

1

1

2

.0

7

112.03

109.8

6

109.6

2

109.6

3

109.5

2

109.9

6

109.8

6

109.8

6

110.0

7

110.1

2

110.4

4

110.3

4

110.1

9

110.1

2

110.4

1

110.7

6

110.5

1

110.4

4

110.5

4

110.5

7

110.8

0

110.7

1

110.6

6

111.0

3

111.3

7

110.9

7

110.9

7

110.9

7

111.0

0

111.1

8

111.2

0

111.2

5

111.5

2

111.8

5

111.9

4

111.8

6

111.6

5

T

H

1

1

3

.7

7

T

H

1

1

3

.9

2

TH

113.96

112.68

112.66

112.65

112.59

112.56

112.51

112.50

112.47

112.45

112.38

112.31

1

1

2

.2

8

1

1

2

.2

6

1

1

2

.1

9

1

1

2

.1

5

112.08

112.14

112.25

112.37

112.27

112.33

112.43

112.4

7

112.4

3

1

1

2

.

4

6

1

1

2

.

3

7

1

1

2

.

4

61

1

2

.

5

7

112.46

112.53

112.54

112.49

112.54

112.53

112.56

112.63

112.70

112.63

112.63

112.70

112.75

112.67

112.6

1

TH

114.7

4

112.6

3

112.5

8

112.5

9

112.6

0

112.5

8

TH

114.4

7

1

1

2

.5

9

T

H

1

1

4

.6

9

TH

114.23

112.52

112.48

112.40

1

1

2

.3

6

1

1

2

.1

2

1

1

0

.0

0

m

1

1

1

.

0

0

m

1

1

2

.0

0

m

Post &

W

ire F

ence

Post &

W

ire F

ence

Post &

W

ire F

ence

Post &

W

ire F

ence

Hedge

Hedge

Hedge

GU

GU

GU

GU

H

edge

H

e

d

g

e

K

e

rb

K

erb

K

erb

K

erb

K

erb

K

erb

K

erb

K

erb

K

erb

K

erb

K

erb

DK

361550.626

437261.929

TC

E

N

Ht

04

361676.688

437280.247

112.765

L

o

w

e

r R

o

a

d

Site Address

Project Description

Drawing Title

Scale Date Drawn By

Drawing Number

Rev. Description.

Notes




& stability.


Higher College Farm

Lower Road

Hothersall PR3 2YY

Site Survey


1:200@A1 30/05/2017 MW

TRI-2005-02

0 Issued

North

0 2 4 6 8 10 12 14 16 18 20Metres

Top of WallTW

Man Hole

Telegraph Pole

Gully

Cover Level

MH

TP

GU

CL

Ridge/Roof HeightRH

Eaves HeightEH


BT CoverBT

Water ValveWV

Sign PostSP

Soil Vent PipeSVP

Inspection CoverIC

Threshold LevelTL

Cable HeightCH

NOTE



of kerb).

Top of FenceTF

BollardBOL

Top of HedgeTH

ABBREVIATIONS

Drop KerbDK

1

23

1

0

9

.8

8

1

0

9

.8

9

1

0

9

.7

4

1

0

9

.7

2

1

0

9

.5

9

1

0

9

.5

0

1

0

9

.1

3

1

0

9

.2

6

1

0

8

.9

0

1

0

8

.8

7

TP

C

H

1

1

7

.

1

6

1

1

2

.0

3

1

1

1

.6

6

111.8

8

112.2

2

112.06

1

1

1

.

9

3

1

1

1

.

7

0

1

1

1

.

2

3

1

1

1

.

0

5

1

1

1

.

2

1

1

1

0

.

8

6

1

1

0

.2

9

109.87

1

0

9

.

8

9

1

0

9

.

4

3

1

0

9

.4

3

1

0

9

.3

4

1

0

9

.3

1

109.5

5

109.6

4

109.8

5

109.9

4

110.1

2

110.1

4

110.0

2

109.5

8

109.9

8

110.2

6

110.3

7

110.4

4

110.5

7

110.5

1

110.2

2

110.0

0

110.7

1

110.6

0

110.7

2

110.8

1

111.0

0

110.9

9

110.9

9

111.3

5

111.5

6

111.8

3

111.3

2

111.2

4

111.1

8

111.5

0

111.5

5

111.8

6

112.0

3

111.6

5

T

H

1

1

3

.

5

0

T

H

113.62

TH

113.5

5

T

H

1

1

3

.7

7

1

0

8

.8

2

1

0

9

.0

8

1

0

9

.3

7

1

0

9

.0

4

1

0

9

.

9

1

1

0

9

.

9

7

1

0

9

.5

2

1

0

9

.9

0

1

1

0

.0

2

1

0

9

.9

2

1

0

9

.9

5

1

1

0

.0

4

1

0

9

.

9

7

1

1

0

.

0

5

1

1

0

.

1

2

1

0

9

.6

7

1

0

9

.8

1

1

0

9

.8

8

1

0

9

.9

9

1

1

0

.0

0

1

1

0

.

4

0

1

1

0

.

0

9

1

1

0

.

1

9

1

1

0

.

4

8

1

1

0

.

3

8

1

1

0

.

3

0

1

1

0

.

4

0

1

1

0

.

6

7

1

1

1

.

1

6

1

1

0

.

8

5

C

H

118.48

1

1

2

.1

9

1

1

2

.0

9

1

1

1

.9

6

1

1

1

.8

1

1

1

1

.5

7

1

1

1

.3

6

1

1

1

.2

3

1

1

1

.1

3

111.02

1

1

1

.

1

0

1

1

1

.1

8

1

1

1

.1

3

1

1

1

.2

9

111.58

111.8

5

112.0

3

112.1

2

111.93

111.82

1

1

1

.5

7

111.66

1

1

1

.3

8

1

1

1

.3

1

1

1

1

.1

3

1

1

1

.2

0

1

1

1

.1

1

1

1

1

.0

5

1

1

0

.9

7

1

1

1

.0

3

1

1

1

.1

1

1

1

1

.0

7

1

1

1

.

1

1

BOL

BOL

CL110.98

TARMAC

CHIPPINGS

1

1

0

.

8

1

1

1

0

.

4

4

1

1

0

.

2

9

1

1

0

.

2

3

1

1

0

.

3

0

1

1

0

.

5

4

1

1

1

.

1

3

111.4

5

1

1

1

.1

8

1

1

1

.

3

4

P

o

s

t

&

R

a

il

F

e

n

c

e

1

1

2

.1

3

P

o

s

t &

W

ire

F

e

n

c

e

112.0

0

1

1

1

.9

4

1

1

2

.1

5

1

1

2

.2

7

112.45

SP

TP

BT

T

H

1

1

2

.

7

4

T

H

1

1

2

.8

2

T

H

1

1

3

.7

0

SP

111.18

1

1

1

.

1

5

1

1

1

.2

6

1

1

1

.3

3

1

1

1

.5

5

1

1

1

.4

9

1

1

1

.6

7

1

1

1

.7

7

1

1

1

.9

0

1

1

1

.8

4

1

1

1

.9

5

1

1

2

.0

2

1

1

2

.1

5

112.08

1

1

1

.9

3

112.03

112.2

1

111.8

6

111.68

111.80

1

1

1

.8

1

109.00m

1

1

0

.

0

0

m

111.0

0m

112.00m

1

1

2

.

0

0

m

1

1

2

.0

0

m

GU

112.05

GU

GU

GU

GU

GU

GU

MH

Hedge

H

e

d

g

e

H

e

d

g

e

H

e

d

g

e

H

e

d

g

e

H

e

d

g

e

H

e

d

g

e

H

e

d

g

e

H

e

d

g

e

H

e

d

g

e

H

edge

TH

114.41

T

H

1

1

3

.8

2

Kerb

Kerb

K

e

rb

K

e

rb

K

e

rb

K

e

rb

K

e

rb

K

e

rb

K

e

rb

K

e

rb

K

e

rb

DK

DK

CHIPPINGS

CHIPPINGS

TC

E

N

Ht

01

361443.031

437243.911

111.630

TC

E

N

Ht

02

361492.239

437253.205

111.244

TC

E

N

Ht

03

361550.626

437261.929

112.201

L

o

w

e

r R

o

a

d

Site Address

Project Description

Drawing Title

Scale Date Drawn By

Drawing Number

Rev. Description.

Notes




& stability.


Higher College Farm

Lower Road

Hothersall PR3 2YY

Site Survey


1:200@A1 30/05/2017 MW

TRI-2005-03

0 Issued

North

0 2 4 6 8 10 12 14 16 18 20Metres

Top of WallTW

Man Hole

Telegraph Pole

Gully

Cover Level

MH

TP

GU

CL

Ridge/Roof HeightRH

Eaves HeightEH


BT CoverBT

Water ValveWV

Sign PostSP

Soil Vent PipeSVP

Inspection CoverIC

Threshold LevelTL

Cable HeightCH

NOTE



of kerb).

Top of FenceTF

BollardBOL

Top of HedgeTH

ABBREVIATIONS

Drop KerbDK

1

23

APPENDIX B

Greenfield Runoff Rates

This report was produced using the greenfield runoff tool developed by HR Wallingford and available at www.uksuds.com. The use of this tool is subject to the UK SuDS terms and conditions and licence agreement, which can both be found at http://uksuds.com/terms-and-conditions.htm. The outputs from this tool have been used to estimate storage volume requirements. The use of these results is the responsibility of the users of this tool. No liability will be accepted by HR Wallingford, the Environment Agency, CEH, Hydrosolutions or any other organisation for use of this data in the design or operational characteristics of any drainage scheme.

Greenfield runoff estimation for sites

www.uksuds.com │ Greenfield runoff tool

This is an estimation of the greenfield runoff rate limits that are needed to meet normal best practice criteria in line with Environment Agency guidance “Preliminary rainfall runoff management for developments”, W5-074/A/TR1/1 rev. E (2012) and the SuDS Manual, C753 (Ciria, 2015). This information on greenfield runoff rates may be the basis for setting consents for the drainage of surface water runoff from sites.

Site name:

Calculated by:

Latitude:

Longitude:

Reference:

Date:

Site coordinates

Site location:

Site characteristicsTotal site area (ha)

MethodologyQbar estimation methodSPR estimation method

Default Edited

SOIL typeHOST classSPR/SPRHOST

Hydrological characteristics Default Edited

SAAR (mm)Hydrological region Growth curve factor: 1 year Growth curve factor: 30 year Growth curve factor: 100 year

Notes:(1) Is QBAR < 2.0 l/s/ha?

(2) Are flow rates < 5.0 l/s?

(3) Is SPR/SPRHOST ≤ 0.3?

Greenfield runoff rates Default Edited

Qbar (l/s)1 in 1 year (l/s)1 in 30 years (l/s)1 in 100 years (l/s)

Methodology IH124

0.47

8.79

1.7

21.01

0.87 0.87

10

1.13

2018-11-22T12:42:45

Hothersall

---

2.5854° W

8.79

Higher College Farm

10.1

David Emmott

2.08

10.1

Calculate from SOIL type

53.82953° N

11851185

44

21.01

2.08

Calculate from SPR and SAAR

10

---

17.17 17.17

1.7

6494316

0.47

APPENDIX C

On-site Storage Requirements

Surface water storage requirements for sites

www.uksuds.com │ Storage estimation tool

This report was produced using the Storage estimation tool developed by HR Wallingford and available at www.uksuds.com. The use of this tool is subject to the UK SuDS terms and conditions and licence agreement, which can both be found at http://uksuds.com/terms-and-conditions.htm. The outputs from this tool have been used to estimate storage volume requirements. The use of these results is the responsibility of the users of this tool. No liability will be accepted by HR Wallingford, the Environment Agency, CEH, Hydrosolutions or any other organisation for use of this data in the design or operational characteristics of any drainage scheme.

This is an estimation of the storage volume requirements that are needed to meet normal best practice criteria in line with Environment Agency guidance “Preliminary rainfall runoff management for developments”, W5-074/A/TR1/1 rev. E (2012) and the SuDS Manual, C753 (Ciria, 2015). It is not to be used for detailed design of drainage systems. It is recommended that hydraulic modelling software is used to calculate volume requirements and design details before finalising the drainage scheme.

Site name:

Calculated by:

Latitude:

Longitude:

Reference:

Date:

Site coordinates

Site location:

* Where rainwater harvesting or infiltration has been used for managing surface water runoff such that the effective impermeable area is less than 50 % of the ‘area positively drained’, the ‘net site area’ and the estimates of Qbar and other flow rates will have been reduced accordingly.

Site characteristicsTotal site area (ha)Significant public open space (ha)Area positively drained (ha)Pervious area contribution (%)Impermeable area (ha)Percentage of drained area that is impermeable (%)Impervious area drained via infiltration (ha)Return period for infiltration system design (year)Impervious area drained to rainwater harvesting systems (ha)Return period for rainwater harvesting system design (year)Compliance factor for rainwater harvesting system design (%)Net site area for storage volume design (ha)Net impermeable area for storage volume design (ha)

Design criteriaVolume control approach

Default Edited

Climate change allowance factorUrban creep allowance factorInterception rainfall depth (mm)Minimum flow rate (l/s)

Qbar estimation methodSPR estimation method

Default Edited

Qbar total site area (l/s)SOIL typeHOST classSPR

Hydrology Default Edited

SAAR (mm)M5-60 Rainfall Depth (mm)‘r’ Ratio M5-60/M5-2 day Rainfall 100 yrs 6 hrsRainfall 100 yrs 12 hrsFEH/FSR conversion factor Hydrological region Growth curve factor: 1 year Growth curve factor: 10 yearGrowth curve factor: 30 year Growth curve factor: 100 year

Site discharge rates Default Edited

Qbar total site area (l/s)Qbar net site area (l/s)1 in 1 year (l/s)1 in 30 years (l/s)1 in 100 years (l/s)

Estimated storage volumes Default Edited

Interception storage (m3)Attenuation storage (m3)Long term storage (m3)Treatment storage (m3)Total storage (excluding treatment) (m3)

Methodology IH124

1.0

Use long term storage


5

5.01

1.1 1.1

0.47

10.1

91

N/A

30

70


0

8.5

David Emmott

5

1.7

1.19

6767

11851185

5

Longridge

1.0

10

91

N/A

22

53.82923° N

0.5599999999999999

1.7

20

0.87 0.87

--

0.3

10.1100

6494322

0.47

2.08

1.38

315

0.57

10.410.4

20

0

1.13

2.58537° W

2018-11-22T12:58:55

8.5

99.96

2.08

10

0.366

315

0.56

0.5599999999999999

22

5.01

0.56

5

10

1.19

1.38

4 4

201201

Higher College

5

5

10.1

http://www.uksuds.com


http://uksuds.com/terms-and-conditions.htm





Site name:

Calculated by:

Latitude:

Longitude:

Reference:

Date:

Site coordinates

Site location:




Default Edited



Default Edited








Methodology IH124

1.2



5

5.01

1.1 1.1

0.47

10.1

91

N/A

30

70


0

8.5

David Emmott

5

1.7

1.19

6767

11851185

5

Longridge

1.2

10

91

N/A

22

53.82923° N

0.5599999999999999

1.7

20

0.87 0.87

--

0.3

10.1100

6494322

0.47

2.08

1.38

404

0.57

10.410.4

20

0

1.13

2.58537° W

2018-11-22T12:58:20

8.5

99.96

2.08

10

0.366

404

0.56

0.5599999999999999

22

5.01

0.56

5

10

1.19

1.38

4 4

290290

Higher College

5

5

10.1








Site name:

Calculated by:

Latitude:

Longitude:

Reference:

Date:

Site coordinates

Site location:




Default Edited



Default Edited








Methodology IH124

1.4



5

5.01

1.1 1.1

0.47

10.1

91

N/A

30

70


0

8.5

David Emmott

5

1.7

1.19

6767

11851185

5

Longridge

1.4

10

91

N/A

22

53.82923° N

0.5599999999999999

1.7

20

0.87 0.87

--

0.3

10.1100

6494322

0.47

2.08

1.38

492

0.57

10.410.4

20

0

1.13

2.58537° W

2018-11-22T12:54:58

8.5

99.96

2.08

10

0.366

492

0.56

0.5599999999999999

22

5.01

0.56

5

10

1.19

1.38

4 4

378378

Higher College

5

5

10.1




APPENDIX D

Preliminary Drainage Design

G

eocellula

r S

torage

24 m

x 11 m

x1.6 m

Foul connection into

existing foul sewer north

of site. Exact location to

be confirmed

Surface Water Connection

into watercourse restricted

to greenfield runoff rates

Hydrobrake or similar to

restrict discharge rate

from geocelluar tank

LEGEND

FILE_NAME

HIGHER COLLEGEFARMHOUSE, HOTHERSALL,

PRESTON

NTS D.E. M.B. 23/11/18

17303-5 -

PRELIMINARY DRAINAGEDESIGN

Suite One, No 3 Mitton Road Business Park, Mitton Road,Whalley, Lancashire BB7 9YE

Tel: 01254 377622 Mob: 07906753583 Email: [email protected]

Web: www.bekenviro.co.uk

PROPOSED SURFACE

WATER DRAIN

MR M HURST

PROPOSED SW

MANHOLE

PROPOSED FOUL

DRAIN

PROPOSED FOUL

MANHOLE

FLOOD RISK & DRAINAGE IMPACT ASSESSMENT REPORT

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