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RENEWABLE ENERGY CENTRE, HAMS HALL, COLESHILL

FLOOD RISK ASSESSMENT AND DRAINAGE STRATEGY

KILBRIDE GROUP

MAY 2016

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RENEWABLE ENERGY CENTRE, HAMS HALL, COLESHILL FLOOD RISK ASSESSMENT AND DRAINAGE STRATEGY

i K116 - DOC01 - FRA and Drainage Strategy - Issue 3

May 2016

DOCUMENT CONTROL

Job No K116

File Reference G:\workfiles\K116\REPORTS\K116 - DOC01 - FRA and Drainage Strategy - Issue 3.docx

Name Date Initials

Prepared By N. Glowacka 09.05.2016

Checked By M. Skivington 10.05.2016

Issue Date Comments Approved

1 13.05.2016 -

G. Eves

BSc CEng MICE MCIHT

2 24.05.2016 Application Site Layout

updated.

G. Eves

BSc CEng MICE MCIHT

3 25.05.2016 Application Site Layout

updated.

G. Eves

BSc CEng MICE MCIHT

This document has been prepared for the exclusive use of the client in connection with the project and its copyright remains vested in PFA Consulting. Unless otherwise agreed in writing by PFA Consulting, no person or party may copy, reproduce, make use of or rely upon its contents other than for the purposes for which it was originally prepared and provided. Opinions and information provided in this document have been provided using due care and diligence. It should be noted and is expressly stated that no independent verification of any information supplied to PFA Consulting has been made. Warning: This document may contain coloured images which may not print satisfactorily in black and white. It may also contain images originally created at a size greater than A4 which may not print satisfactorily on small printers. If copying is authorised but difficulty is incurred in reproducing a paper copy of this document, or a scaled copy is required, please contact PFA Consulting. Authorisation for reproducing plans based upon Ordnance Survey information cannot be given. © PFA Consulting Ltd 2016


ii K116 - DOC01 - FRA and Drainage Strategy - Issue 3

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iii K116 - DOC01 - FRA and Drainage Strategy - Issue 3

May 2016

CONTENTS

PAGE NO.

1. EXECUTIVE SUMMARY ............................................................................. 1

2. INTRODUCTION ...................................................................................... 2

3. SCOPE OF THE ASSESSMENT ..................................................................... 3

Development Plan Policy ................................................................................................................................... 5

Summary of Scope ............................................................................................................................................. 6

4. FLOOD RISK ASSESSMENT ........................................................................ 7

Site Location and Local Watercourses ............................................................................................................... 7

Site Levels .......................................................................................................................................................... 7

Ground Conditions ............................................................................................................................................. 7

Groundwater Source Protection ........................................................................................................................ 8

Definition of the Flood Hazard ........................................................................................................................... 8

Flooding from Watercourses ........................................................................................................................ 9

Flooding from Surface Water ....................................................................................................................... 9

Flooding from Groundwater ...................................................................................................................... 10

Flooding from Overwhelmed Sewers and Drainage Systems .................................................................... 10

Flooding from Artificial Sources ................................................................................................................. 10

Summary of Flood Hazards ........................................................................................................................ 10

Probability ........................................................................................................................................................ 11

The Development Proposals ............................................................................................................................ 11

The Sequential Test and Flood Zone ‘Compatibility’ ....................................................................................... 12

5. OUTLINE DRAINAGE STRATEGY ............................................................... 13

Design Criteria.................................................................................................................................................. 13

Climate Change .......................................................................................................................................... 13

Standard of Protection ............................................................................................................................... 13

Sustainable Drainage Systems .................................................................................................................... 14

Surface Water Drainage Strategy .................................................................................................................... 15

Summary of Proposals................................................................................................................................ 15

Pre Development Runoff Rates .................................................................................................................. 16

Proposed Surface Water Flow Balancing and Post Development Runoff Rates ........................................ 17

Non-Statutory Technical Standards for SuDS ............................................................................................. 18

Flood Risk Management Measures.................................................................................................................. 19

Minimum Ground Floor Levels ................................................................................................................... 19

Off Site Impact............................................................................................................................................ 19


iv K116 - DOC01 - FRA and Drainage Strategy - Issue 3

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Overland Flood Flow Paths......................................................................................................................... 19

Flood Risk Management Measures ............................................................................................................ 20

Safe Access and Egress .................................................................................................................................... 20

Residual Risk .................................................................................................................................................... 20

Proposed Foul Water Drainage Arrangements ................................................................................................ 21

Maintenance Strategy...................................................................................................................................... 22

6. CONCLUSIONS ...................................................................................... 23

FIGURES Figure 1 Site Location Plan Figure 2 Environment Agency’s Flood Map for Planning Figure 3 Environment Agency’s Aquifer Designation Map Figure 4 Environment Agency’s Risk of Flooding from Surface Water Map Figure 5 Severn Trent Water Public Sewer Map Extract TABLES Table A: Pre-development Potential Flood Risk from All Sources of Flooding Table B: Greenfield Runoff Rates Table C: Proposed Surface Water Drainage Network Table D: Compliance with non-statutory technical standards for sustainable drainage systems Table E: Post-development Potential Flood Risk from All Sources of Flooding Table F: Attenuation Tank Maintenance Procedures APPENDICES Appendix 1 DEFRA and Environment Agency’s Guidance: ‘Flood risk assessment in flood zone

1 and critical drainage areas’ Appendix 2 Drawing No. K116/01 Rev. A – Topographical Survey with Overland Flow Paths Appendix 3 Drawing No. K116/02 – SAAR and WRAP Map Appendix 4 Illustrative Masterplan – Pegasus Design – Drawing number K.173_05 Rev. E Appendix 5 Appendix 6 Appendix 7 Appendix 8

Drawing No. K116/03 Rev. B – Indicative Surface Water Drainage Arrangements Plan Micro Drainage Calculations – Greenfield Runoff Micro Drainage Calculations – Proposed Surface Water Drainage System

Model Details

Simulation Results (1:1, 1:30, 1:100, 1:100 + 20%, 1:100 + 40%) Public Sewer Map – Severn Trent Water


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1. EXECUTIVE SUMMARY

This Flood Risk Assessment and Drainage Strategy has been prepared on behalf of Rolton Kilbride 1.1.in connection with proposals for a Renewable Energy Centre development that generates power and heat.

The site is situated entirely within Flood Zone 1 which has the lowest chance of flooding from 1.2.watercourses. The risk of other forms of flooding affecting the development site has been assessed as low.

A sustainable surface water drainage strategy is proposed which incorporates attenuation and 1.3.flow control devices which restrict runoff from the proposed development to greenfield runoff rates. It is proposed that runoff from the development will drain to the public sewer located to the south east to the site.

Pollution control measures will also be incorporated into the drainage system. 1.4.

The overall conclusions drawn from this Flood Risk Assessment are that the development would 1.5.be appropriately safe for its lifetime taking account of the vulnerability of its users, does not increase flood risk elsewhere and the development would reduce flood risk overall.



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2. INTRODUCTION

This Flood Risk Assessment and Drainage Strategy has been prepared on behalf of Rolton Kilbride 2.1.in connection with proposals for a Renewable Energy Centre that will generate power and heat on land at Hams Hall, Coleshill.

The overall site comprises around 1.96 hectares and is located within Hams Hall Industrial Park in 2.2.Coleshill, east of the Birmingham to Derby Railway Line and north of the Hams Hall Rail Freight Terminal. The entire site lies within a great hook of the River Tame. The location of the site is shown edged red on Figure 1 below.

Figure 1: Site Location Plan Based on Ordnance Survey mapping

© Crown copyright. All rights reserved. PFA Consulting Licence No. 100000054

The identified land is allocated as an ‘Employment Site’ in North Warwickshire Borough Council’s 2.3.Development Management Plan – Draft Policies 2015 (Policy DM3). Policy DM3 lists Hams Hall as an existing industrial estate designated for local employment purposes with permitted changes of use between the B1 light industrial, B2 general industrial and B8 warehouse and distribution Use Classes.

The main purpose of this site-specific Flood Risk Assessment is to provide sufficient flood risk 2.4.information to support a planning application for the development proposals in order to demonstrate that the development would be appropriately safe for its lifetime taking account of the vulnerability of its users, without increasing flood risk elsewhere, and, where possible, would reduce flood risk overall.



May 2016

3. SCOPE OF THE ASSESSMENT

The Government’s National Planning Policy Framework (NPPF), published in March 2012, sets out 3.1.the Government’s policy on development and flood risk. On 6 March 2014 the Department for Communities and Local Government (DCLG) launched the Government’s planning practice guidance to the NPPF as a web-based resource. The category dealing with flooding is contained in Flood Risk and Coastal Change1.

The NPPF states in paragraph 100 that Local Plans should be supported by a Strategic Flood Risk 3.2.Assessment (SFRA), and should apply a sequential, risk-based approach to the location of development. As set out in the NPPF, inappropriate development in areas at risk of flooding should be avoided by directing development away from areas at highest risk, but where development is necessary, making it safe without increasing flood risk elsewhere2.

A Level 1 SFRA was prepared by Halcrow Group Limited on behalf of Warwickshire County Council 3.3.in January 2008 to support the development of its Local Development Framework. The SFRA provides an overview of flood risk from all sources including from rivers and the sea, directly from rainfall on the ground surface and rising groundwater, overwhelmed sewers and drainage systems, and from reservoirs, canals and lakes and other artificial sources.

As set out in the NPPF3, the aim of the Sequential Test is to steer new development to areas with 3.4.the lowest probability of flooding. Paragraph 19 in Section 5 of the Flood Risk and Coastal Change Planning Practice Guidance4 states that the flood zones, as refined in the SFRA for the area, provide the basis for applying the Sequential Test.

A copy of the Environment Agency’s Flood Map for Planning, obtained from its website, which 3.5.shows the Flood Zones in the vicinity of the site, is reproduced as Figure 2 below.

1 Planning practice guidance reference ID: 7 Updated: 15 04 2015. 2 National Planning Policy Framework Paragraph 100. 3 National Planning Policy Framework Paragraph 101. 4 Planning practice guidance reference ID: 7-019-20140306



May 2016

Figure 2: EA Flood Map for Planning

The Environment Agency’s Flood Zones refer to the probability of river and sea flooding, ignoring 3.6.the presence of defences, and show the extent of the natural floodplain and the additional extent of an extreme flood. The Environment Agency’s Flood Map for Planning shows the area that could be affected by flooding, either from rivers or the sea, coloured dark blue corresponding to Flood Zone 3. The light blue area is Flood Zone 2 and shows the additional extent of an extreme flood from rivers or the sea. These two colours show the extent of the natural floodplain if there were no flood defences or certain other manmade structures and channel improvements. Where there is no blue shading, this shows the area where flooding from rivers and the sea is very unlikely corresponding to Flood Zone 1.

From an inspection of the Flood Map it can be seen that the site entirely falls within Flood Zone 1 3.7.which indicates the lowest risk of flooding, having less than a 1 in 1000 annual probability of river or sea flooding.

As set out in the NPPF5, local planning authorities should only consider development in flood risk 3.8.areas appropriate where informed by a site-specific flood risk assessment. Footnote 20 in the NPPF states that site-specific flood risk assessment is required for proposals of 1 hectare or greater in Flood Zone 1.

Paragraph 30 in Section 10 of the Flood Risk and Coastal Change Planning Practice Guidance6 3.9.advises that a site-specific flood risk assessment is carried out to assess the flood risk to and from a development site. The assessment should demonstrate how flood risk will be managed now and

5 National Planning Policy Framework Paragraph 103. 6 Planning practice guidance reference ID: 7-030-20140306.



May 2016

over the development’s lifetime, taking climate change into account, and with regard to the vulnerability of its users.

For the purposes of applying the NPPF, paragraph 2 in Section 1 of the Flood Risk and Coastal 3.10.Change Planning Practice Guidance7 advises that “flood risk” is a combination of the probability and the potential consequences of flooding from all sources - including from rivers and the sea, directly from rainfall on the ground surface and rising groundwater, overwhelmed sewers and drainage systems, and from reservoirs, canals and lakes and other artificial sources.

Paragraph 31 in Section 10 of the Flood Risk and Coastal Change Planning Practice Guidance8 3.11.advises that the information provided in the flood risk assessment should be credible and fit for purpose. Site-specific flood risk assessments should always be proportionate to the degree of flood risk and make optimum use of information already available, including information in a SFRA for the area, and the interactive flood risk maps. A flood risk assessment should also be appropriate to the scale, nature and location of development.

Section 26 of the Flood Risk and Coastal Change Planning Practice Guidance9 provides a Checklist 3.12.for the preparation of a site-specific flood risk assessment.

With regard to what further advice is available on the preparation of a site-specific flood risk 3.13.assessment, paragraph 32 in Section 10 of the Flood Risk and Coastal Change Planning Practice Guidance10 refers to the Environment Agency Standing Advice on flood risk.

Guidance from the Department for Environment, Food & Rural Affairs and Environment Agency, 3.14.published on the Government’s GOV.UK website, sets out when local planning authorities must consult the Environment Agency, their Lead Local Flood Authority (LLFA) or both on any proposed developments at a higher risk from flooding before making a decision.

Warwickshire County Council is the LLFA and is responsible for managing local flood risk from 3.15.surface water, groundwater and ordinary watercourses in Warwickshire.

Guidance from Department for Environment, Food & Rural Affairs (DEFRA) and the Environment 3.16.Agency, on the Government’s GOV.UK website, includes guidance on how to carry out a flood risk assessment entitled: ‘Flood risk assessment in flood zones 2 and 3’, and ‘Flood risk assessment in flood zone 1 and critical drainage areas’. This guidance provides information on the range of factors that need to be considered when assessing flood risk.

The relevant guidance for the proposed development is entitled: ‘Flood risk assessment in flood 3.17.zone 1 and critical drainage areas’. A copy of this guidance is reproduced in Appendix 1.

Development Plan Policy The Local Plan for North Warwickshire consists of a number of documents, all forming part of 3.18.

Development Plan. The Core Strategy, adopted in October 2014, is a key part of the Local Plan and contains a vision and strategic objectives for the Borough as well as Core Policies for next 20 years.

Relevant policies from the local plan include Policy NW10. 3.19.

7 Planning practice guidance reference ID: 7-002-20140306. 8 Planning practice guidance reference ID: 7-031-20140306. 9 Planning practice guidance reference ID: 7-068-20140306 10 Planning practice guidance reference ID: 7-032-20150415.



May 2016

Policy NW10: Development Considerations states: 3.20.

“Development should meet the needs of residents and businesses without compromising the ability of future generations to enjoy the same quality of life that the present generation aspires to. Development should:

(..)

11. manage the impacts of climate change through the design and location of development, including sustainable drainage, water efficiency measures, use of trees and natural vegetation and ensuring no net loss of flood storage capacity; and

12. protect the quality and hydrology of ground or surface water sources so as to reduce the risk of pollution and flooding, on site or elsewhere.

…”

Summary of Scope The scope of this Flood Risk Assessment is to provide sufficient information to satisfy the relevant 3.21.

requirements of the NPPF, DEFRA/Environment Agency guidance, the planning practice Site-Specific Flood Risk Assessment Checklist, and Local Plan Policies.



May 2016

4. FLOOD RISK ASSESSMENT

Site Location and Local Watercourses The Site Location Plan and the Environment Agency’s Flood Map for Planning are based on the 4.1.

Ordnance Survey map of the area, and show geographical features and identify watercourses and other bodies of water in the vicinity of the site.

The site is located on the former Hams Hall Substation, east of the Birmingham to Derby Railway 4.2.Line and north to the Hams Hall Rail Freight Terminal. The site has been cleared of buildings and currently comprises consolidated land covered by crushed hardcore and rubble. The site is believed to be effectively 100% impermeable.

The entire site is bounded by a 2.4m high concrete wall and a palisade fence of comparable 4.3.height. The National Grid Areas adjoined to the western boundary of the site and to the north east corner of the site are additionally defended by lines of Armco Barrier.

The nearest water features are two small ponds located in the vicinity of the Faraday Avenue and 4.4.Canton Lane roundabout approximately 0.3km east of the site. The River Tame is a main river and creates a great hook around the Hams Hall Industrial Park. The closest point of the River Tame is located approximately 0.7km to the north-east of the site.

Flood defences are identified within the left bank of the River Tame to the south of the site and 4.5.consist of earth embankments and concrete revetments.

The existing drainage arrangements for the site are unknown. A Topographical Survey, 4.6.undertaken by Brunel Surveys Ltd in April 2016 does not identify any drainage features within the site. A copy of the Topographical Survey with indicative overland flow directions is shown on Drawing Number K116/01 Rev. A reproduced in Appendix 2.

Site Levels The Topographical Survey indicates that the entire site is effectively flat and slopes from a 4.7.

maximum level of 80.09m AOD in the south-western corner of the site to 79.16m AOD in the south-eastern corner of the site.

Ground Conditions The British Geological Survey (BGS) geological mapping of the area shows the majority of the site 4.8.

is underlain by Mudstone Bedrock and River Terrace Superficial Deposits, 2 – Sand and Gravel. Superficial Deposits were formed from rivers depositing mainly sand and gravel detrital material in channels to form river terrace deposits, with fine silt and clay from overbank floods forming floodplain alluvium, and some bogs depositing peat.

Based on the Flood Studies Report Winter Rainfall Acceptance Potential (WRAP) Map, as shown 4.9.reproduced on Drawing Number K116/02 in Appendix 3, the site is located in a ‘Soil Index Class 4’ area. Soil Index Class 4 has a relatively low winter rainfall acceptance potential and high standard percentage runoff, and so suggests the underlying soil has poor permeability.

The Cranfield Soil and AgriFood Institute (CSAI), incorporating the National Soil Resources 4.10.Institute (NSRI,) at Cranfield University maintains soil reports and maps for England and Wales. The Soilscapes dataset map indicates that soils in the area are ‘loamy soils with naturally high groundwater’. These soils are identified as being ‘naturally wet’ which indicates permeable soil with high ground water levels that has drained from surrounding landscape.



May 2016

The above confirms that infiltration is not an appropriate means of surface water disposal. 4.11.

Groundwater Source Protection From an inspection of the Environment Agency’s Aquifer Designation Map on its website the site 4.12.

is underlain by a ‘Secondary B Aquifer’. Secondary B Aquifers are “predominantly lower permeability layers which may store and yield limited amounts of groundwater due to localised features such as fissures, thin permeable horizons and weathering. These are generally the water-bearing parts of the former non-aquifers”. A copy of the Environment Agency’s Aquifer Designation Map is reproduced in Figure 3 below.

Figure 3: EA Aquifer Designation Map

From an inspection of the Environment Agency’s Groundwater Source Protection Zone Map the 4.13.site does not fall within a Groundwater Source Protection Zone.

Definition of the Flood Hazard In addition to flooding from rivers and the sea it is also necessary to consider the potential 4.14.

consequences of flooding from all other sources, which include directly from rainfall on the ground surface and rising groundwater, overwhelmed sewers and drainage systems, and from reservoirs, canals and lakes and other artificial sources.

The Environment Agency’s interactive Flood Hazard Maps, on its website, include maps showing 4.15.risk of flooding from rivers and sea, from reservoirs, and from surface water, and indicate the extent, depth and velocity of water for a number of scenarios. These Maps are known as Risk of Flooding from Rivers and Sea Map, Risk of flooding from Surface Water Map, and Risk of flooding



May 2016

from Reservoirs Map. The Maps show the chance of flooding in one of four categories: High (>1 in 30), Medium (<1 in 30), Low (1 in 100-1000), and Very Low (<1 in 1000).

The Environment Agency advises that the information provided by the Flood Hazard Maps is not 4.16.suitable for land-use planning and the Flood Map for Planning needs to be used for this purpose. Nonetheless these Flood Hazard Maps contain information which needs to be taken into account as part of a flood risk assessment.

Flooding from Watercourses As reproduced on Figure 2, the Environment Agency’s Flood Map for Planning shows that the site 4.17.

lies entirely within Flood Zone 1.

The SFRA contains no record of historic flooding from watercourses in the vicinity of the 4.18.application site.

Flooding from Surface Water The Environment Agency’s Risk of Flooding from Surface Water Map indicates where surface 4.19.

water may be expected to flood or pond. Surface water flooding happens when rainwater does not drain away through the normal drainage systems or soak into the ground, but lies on or flows over the ground instead. A copy of the Environment Agency’s Risk of Flooding from Surface Water Map is reproduced in Figure 4 below.

Figure 4: EA Risk of Flooding from Surface Water Map



May 2016

The Risk of Flooding from Surface Water Map shows the majority of the site lies in an area with a 4.20.‘very low’ risk of surface water flooding. There is a strip of ‘low’ risk area running along the site’s eastern boundary. This is associated with overland flows within the site being held back by a concrete wall running along the boundary.

Flooding from Groundwater No previous incidences of groundwater emergence have been recorded on or near the application 4.21.

site.

The North Warwickshire Borough Council SFRA states that based on Environment Agency 4.22.groundwater levels monitoring no records of flooding from groundwater within North Warwickshire Borough are identified.

Flooding from Overwhelmed Sewers and Drainage Systems Flooding from sewers and drainage systems occurs when the sewer or drainage system is 4.23.

overwhelmed as a result of a blockage or excessive flow exceeding its capacity. Enquiries have been made to Severn Trent Water to establish the location of the existing public sewers in the vicinity of the site.

There is no existing off-site public sewer network in the immediate vicinity of the site. There are 4.24.public foul and storm water sewers approximately 0.2km to the south-east and south west of the site.

The SFRA identifies that the development site lies in a post code area affected by sewer flooding, 4.25.however it relates to a wider area where only one incident of sewer flooding was identified. Subsequently, it is considered that the risk of flooding from an overwhelmed sewer system is very low.

Flooding from Artificial Sources The Environment Agency’s Risk of Flooding from Reservoirs Map indicates the site is unaffected 4.26.

by flooding from any reservoirs.

Summary of Flood Hazards A summary of the potential risk from all sources of flooding associated with existing conditions 4.27.

pre-development is shown in Table A below.

Table A: Pre-development Potential Flood Risk from All Sources of Flooding

Flood Source Potential Risk

Description Very Low Low Medium High

Watercourses X

The site is located in Flood Zone 1.

Surface Water X The EA’s Risk of Flooding from Surface Water Map shows the majority of the site lies in an area with a ‘very low’ risk of surface water flooding.

Groundwater X

The SFRA does not identify any groundwater flooding affecting the site.

Overwhelmed Sewers

X There is no existing sewer network in the immediate vicinity of the site, and it is considered that the risk of sewer flooding is low.

Artificial Sources X The site is not affected



May 2016

The SFRA, and historic flood information provided by the Environment Agency, provides an 4.28.assessment of the impact of other sources of potential flooding. Based on the SFRA there are no historic flood incidents recorded on the site from all sources of potential flooding.

The pre-development potential flood risk to the site from all sources of flooding is considered to 4.29.be very low.

Probability The site falls within Flood Zone 1. Table 1: Flood Zones, in Section 25 of the Flood Risk and Coastal 4.30.

Change Planning Practice Guidance (Reference ID: 7-065-20140306), provides a definition of each Flood Zone. Flood Zone 1 Low Probability is defined as land having a less than 1 in 1000 annual probability of river or sea flooding.

The Development Proposals The development proposals comprise the construction of a Renewable Energy Centre that will 4.31.

generate power and heat. The Renewable Energy Centre will employ a thermal conversion process to generate power and heat from Refuse Derived Fuel, commercial and industrial waste, construction and demolition waste and potential municipal solid waste. The facility will not accept hazardous clinical waste.

The feedstock consists of residual waste material that has available recyclables removed or has 4.32.previously passed through recovery centres for re-use and recycling and has been deemed to have no further use. Currently such residual waste would typically be landfilled however the Proposed Development would provide a facility for the recovery of energy (and potential heat) whilst also reducing the volume of waste being landfilled.

Process equipment for the Renewable Energy Centre will be located within a building resembling 4.33.a standard industrial warehouse, with one combined chimney stack. The Turbine Room, Air Cooled Condenser and Fire Water Tank are included as external elements. A copy of the Illustrative Masterplan, Drawing Number K.173_05 Rev. E, prepared by Pegasus Design, showing the development proposals, is reproduced in Appendix 4.

For context the general process is summarised below: 4.34.

HGVs deliver waste to the plant and the wastes are deposited into an 8m deep waste bunker for shredding and separating of ferrous materials.

A computerised grab feeds the waste into the waste hopper. The fuel then goes into a gasification chamber where the wastes are starved of oxygen at a temperature of 850°C.The syn gas is driven off and sent to the oxidation chamber where the composition of the mixture is adjusted to maximise the efficiency of the combustion process.

The hot flue gases go through a system of boilers and pass through a turbine to produce electricity. The flue is combined with lime for a basic dry clean up and released into the chimney stack. The inert bottom ash and hazardous fly ash material is left behind and disposed of accordingly.

The pollutants in the stack will comply with the Industrial Emissions Directive (2010/75/EU). All non-hazardous material can be recycled or used, e.g. for secondary aggregates, while the hazardous material is stored in a sealed system which is taken off site for neutralisation.



May 2016

There is therefore no foul water discharge produced as a result of the waste handling process - 4.35.the only foul water disposal requirement being ‘domestic flow’ from the welfare facilities on the site (toilets, showers and mess room).

If areas are required for vehicle cleaning, or if wash down of areas inside buildings is required, the 4.36.waste water will be collected in tanks and disposed of off-site at an appropriately licenced facility.

The Renewable Energy Centre is to be designed to operate continuously, 24 hours a day, 7 days 4.37.per week. The Renewable Energy Centre will provide the opportunity for power to be supplied to local businesses or direct to the National Grid.

The proposed development has sustainability benefits and would provide a facility for the 4.38.recovery of energy (including heat) from waste material whilst also reducing the volumes of waste being sent to landfill.

The plant will be subject to an Environmental Permit which includes the regulation of the 4.39.management of waste materials and water on site.

The Sequential Test and Flood Zone ‘Compatibility’ Paragraph 100 of the NPPF states that inappropriate development in areas at risk of flooding 4.40.

should be avoided by directing development away from areas at highest risk, but where development is necessary, making it safe without increasing flood risk elsewhere.

Paragraph 101 of the NPPF states: “The aim of the Sequential Test is to steer new development to 4.41.areas with the lowest probability of flooding. Development should not be allocated or permitted if there are reasonably available sites appropriate for the proposed development in areas with a lower probability of flooding. The Strategic Flood Risk Assessment will provide the basis for applying this test. A sequential approach should be used in areas known to be at risk from any form of flooding.”

The application site lies entirely within Flood Zone 1 in an area with a low probability of flooding 4.42.and subsequently the Sequential Test is passed.

Table 2: Flood Risk Vulnerability Classification, in Section 25 of the Flood Risk and Coastal Change 4.43.Planning Practice Guidance11, categorises different types of development according to their vulnerability to flood risk. Table 3: Flood risk vulnerability and flood zone ‘compatibility’, in Section 25 of the Flood Risk and Coastal Change Planning Practice Guidance12, maps these vulnerability classes against the flood zones to indicate where development is appropriate and where development should not be permitted.

With reference to Table 3, all uses of land are appropriate in Flood Zone 1. 4.44.

11 Planning practice guidance reference ID: 7-066-20140306. 12 Planning practice guidance reference ID: 7-067-20140306.



May 2016

5. OUTLINE DRAINAGE STRATEGY

Design Criteria

Climate Change The NPPF requires development to take account of the impacts of climate change. The allowances 5.1.

to be made for climate change effects when assessing flood risk are related to the lifetime of the development.

In accordance with Section 4.6 of BS 8533:2011 ‘Assessing and managing flood risk in 5.2.development–Code of practice’, the lifetime of a non-residential development is 75 years.

Under heading 4 in the Site-Specific Flood Risk Assessment Checklist in Section 26 of the Flood 5.3.Risk and Coastal Change Planning Practice Guidance13, it asks how flood risk at the site is likely to be affected by climate change and states that further information on climate change and development and flood risk is available on the Environment Agency’s web site. Guidance published by the Environment Agency on 19 February 2016, entitled ‘Flood risk assessments: climate change allowances’, sets out the allowances to be used for peak river flow by river basin district, peak rainfall intensity, sea level rise, offshore wind speed and extreme wave height.

The peak rainfall intensity allowances to be used when designing urban drainage systems are 5.4.given in Table 2 of ‘Flood risk assessments: climate change allowances’. Both the central and upper end allowances need to be assessed to understand the range of impact. The total potential change anticipated for 2060 to 2115 is 20% for the central category, and 40% for the upper end category.

Standard of Protection In terms of providing an acceptable standard of protection against flooding for new development, 5.5.

paragraph 54 in Section 22 of the Flood Risk and Coastal Change Planning Practice Guidance14 advises how development can be made safe from flood risk. Reference is made to the ability of users to safely access and exit a building during a ‘design flood’. Paragraph 55 in Section 22 of the Flood Risk and Coastal Change Planning Practice Guidance15 defines a ‘design flood’: “This is a flood event of a given annual probability, which is generally taken as:

a fluvial (river) flooding likely to occur with a 1% annual probability (a 1 in 100 chance each year) or ;

against which the suitability of a proposed development is assessed and mitigation measures, if any, are designed.”

DEFRA published its ‘Sustainable drainage systems: non-statutory technical standards’ in March 5.6.2015 which should be used in conjunction with the NPPF and planning practice guidance. Standard S7 states that “flooding does not occur on any part of the site for a 1 in 30 year rainfall event”. Standard S8 goes on to state that the drainage system must be designed so that flooding does not occur during a 1 in 100 year rainfall event in any part of a building or any utility plant susceptible to water.

13 Planning practice guidance reference ID: 7-068-20140306 14 Planning practice guidance reference ID: 7-054-20150415 15 Planning practice guidance reference ID: 7-055-20140306



May 2016

Sustainable Drainage Systems Government policy set out in paragraph 103 of the NPPF expects local planning authorities to give 5.7.

priority to the use of sustainable drainage systems (SuDS) in determining planning applications.

Paragraph 51 in Section 21 of the Flood Risk and Coastal Change Planning Practice Guidance16 5.8.advises that sustainable drainage systems are designed to control surface water runoff close to where it falls and mimic natural drainage as closely as possible. Sustainable drainage systems provide opportunities to:

reduce the causes and impacts of flooding;

remove pollutants from urban runoff at source;

combine water management with green space with benefits for amenity, recreation and wildlife.

In terms of what sort of sustainable drainage system should be considered, paragraph 80 in 5.9.Section 21 of the Flood Risk and Coastal Change Planning Practice Guidance17 advises that, generally, the aim should be to discharge surface water runoff as high up the following hierarchy of drainage options as reasonably practicable:

into the ground (infiltration);

to a surface water body;

to a surface water sewer, highway drain, or another drainage system;

to a combined sewer.

‘DRAFT Flood Risk and Drainage Planning Advice – Version 2’ published by Warwickshire County 5.10.Council in September 2015 provides the guidance on the local requirements and application of SuDS in Warwickshire. The guidance requires provision of SuDS “which seeks to mimic natural drainage systems and retain water on site, as opposed to traditional drainage approaches which involve piping water off-site as quickly as possible”.

The Government published its ‘Non-statutory technical standards for sustainable drainage 5.11.systems’ in March 2015. The technical standards relate to the design, construction, operation and maintenance of sustainable drainage systems and have been published as guidance.

Paragraph 81 in Section 21 of the Flood Risk and Coastal Change Planning Practice Guidance18 5.12.states that in considering a development that includes a sustainable drainage system the local planning authority will want to be satisfied that the proposed minimum standards of operation are appropriate. Paragraph 8219 advises that the decision on whether a sustainable drainage system would be inappropriate is a matter of judgement for the local planning authority, taking advice from the relevant flood risk management bodies , including on what sort of sustainable drainage system they would consider to be ‘reasonably practicable’. Paragraph 82 states that the judgement of what is reasonably practicable should be by reference to the technical standards.

The non-statutory technical standards for sustainable drainage systems set out peak flow control 5.13.standards (S2 and S3) and volume control technical standards (S4, S5 and S6). For developments which were previously developed, the corresponding runoff rate for these events must be as close as reasonably practicable to the greenfield runoff rate, but should never exceed the rate of discharge from the development prior to redevelopment for that event.

16 Planning practice guidance reference ID: 7-051-20150323 17 Planning practice guidance reference ID: 7-080-20150323 18 Planning practice guidance reference ID: 7-081-20150323 19 Planning practice guidance reference ID: 7-082-20150323



May 2016

In terms of volume control, where reasonably practicable, for developments which have been 5.14.previously developed this runoff volume must be constrained to a value as close as is reasonably practicable to the greenfield runoff volume, but should never exceed the runoff volume prior to redevelopment for that event. Where it is not reasonably practicable to constrain the volume of runoff as described it must be discharged at a rate that does not adversely affect flood risk.

Paragraph 83 in Section 21 of the Flood Risk and Coastal Change Planning Practice Guidance20 5.15.advises that in terms of the overall viability of a proposed development, expecting compliance with the technical standards is unlikely to be reasonably practicable if more expensive than complying with building regulations provided that where there is a risk of flooding the development will be safe and flood risk is not increased elsewhere.

Paragraph 85 in Section 21 of the Flood Risk and Coastal Change Planning Practice Guidance21 5.16.advises that any sustainable drainage system should be designed so that the capacity takes account of the likely impacts of climate change.

Guidance on the design and construction of SuDS is also provided in the ‘Interim Code of Practice 5.17.for Sustainable Drainage Systems’, published by the National SUDS Working Group in July 2004, in other Ciria documents including Ciria C753 ‘The SuDS Manual’ published in November 2015, as well as in the Environment Agency’s document entitled ‘Sustainable Drainage Systems (SUDS) An introduction’.

Surface Water Drainage Strategy

Summary of Proposals A sustainable drainage strategy, involving the implementation of SuDS, is proposed for managing 5.18.

the disposal of surface water runoff from the proposed development on the site.

As the use of infiltration devices is not appropriate flow balancing methods are proposed. 5.19.Proposals comprise a pipe system and a tank in order to attenuate surface water runoff and, as the brownfield runoff rates are unknown, it is proposed to restrict runoff to greenfield rates. It is proposed that the surface water from the designed network will discharge to the existing off-site public sewer located approximately 100m to the south east of the site.

A preliminary surface water drainage strategy is shown on the Indicative Surface Water Drainage 5.20.Strategy Plan, Drawing No. K116/03 Rev. B, a copy of which is contained in Appendix 5.

Pollution control measures include the use of deep trapped gullies and bypass separators and/or 5.21.full retention separators. All road areas and other areas that drain into gullies should pass through deep trapped gullies. The Environment Agency/s Pollution Prevention Guidelines (PPGs) were withdrawn in December 2015. In the absence of specific guidance BS EN 858-2:200322 is relevant to this development. Annex B – ‘configuration and application of separator systems’ states that, for rainwater from vehicle parks (which is assumed to include HGV turning areas) discharging to a surface water sewer, drainage waters should discharge via a sludge trap and Class 1 Full Retention Separator.

20 Planning practice guidance reference ID: 7-083-20150323 21 Planning practice guidance reference ID: 7-085-20150323 22 BS EN 858-2:2003 Separator systems for light liquids (e.g. oil and petrol). Selection of nominal size, installation, operation and maintenance.



May 2016

The HGV turning areas and unloading areas are considered to be at risk of regular contamination 5.22.and at risk of larger spills. Subsequently, alarmed Full Retention Class 1 Separators are proposed in these areas in accordance with BS EN 858-1:200223 and BS EN 858-2:2003.

The proposed drainage strategy would ensure that surface water arising from the developed site 5.23.would be managed in a sustainable manner to mimic the surface water flows arising from the site prior to the proposed development, while reducing the flood risk to the site itself and elsewhere, taking climate change into account.

Pre Development Runoff Rates Warwickshire County Council published its ‘DRAFT Flood Risk and Drainage Planning Advice – 5.24.

Version 2’ which gives guidance and requirements for permitted surface water discharge rates in the local area. The document states: “In accordance with BS 8582:2013 Code of Practice (Surface Water Management for Development Sites), surface water run-off from all previously developed sites should be reduced to the equivalent greenfield run-off rate wherever possible.

Only where this is technically not feasible and the site is shown to benefit from a positive outfall will WCC allow the use of the existing brownfield flow rate to be used subject to a minimum of 50% betterment.”

In accordance with the guidance above, both the greenfield and brownfield flow rates have been 5.25.calculated to determine the proposed surface water discharge from the site.

Greenfield Runoff Rates Peak Flow Control Standard S2 contained in the ‘non-statutory technical standards for sustainable 5.26.

drainage systems’ states: “For greenfield developments, the peak runoff rate from the development to any highway drain, sewer or surface water body for the 1 in 1 year rainfall event and the 1 in 100 year rainfall event should never exceed the peak greenfield runoff rate for the same event.”.

Warwickshire County Council’s ‘DRAFT Flood Risk and Drainage Planning Advice – Version 2’ 5.27.states: “If complex controls are to be used for control of discharge rates (not our preferred method), calculations for the greenfield runoff rate should be provided for the 1 in 1 year, 1 in 30 year, 1 in 100 year return periods and 1 in a 100 year plus an allowance for climate change”.

Chapter 24 of the SuDS Manual (Ciria C753) presents the design methods to estimate runoff for a 5.28.greenfield site and Table 24.1 provides a summary of runoff estimate methods. The Institute of Hydrology report 12424 (IH124) has been used to calculate QBAR for the development site. QBAR is defined as the Mean Annual Flood with a return period in the region of 2.3 years. The formula has been applied for a site with a 50 ha area and results factored based on the ratio of the actual site area and the application area (50 ha).

The ICP SuDS Method contained with XP Solutions’ Micro Drainage software system (Version 5.29.2015.1) calculates QBAR based on the IH124 methodology with pro-rata values for sites smaller than 50ha. FSSR 2 and 14 regional growth curve factors have been used to calculate the greenfield peak flow rates for 1, 30 and 100 year return periods.

23 BS EN 858-1:2002 Separator systems for light liquids (e.g. oil and petrol). Principles of product design, performance and testing, marking and quality control. 24 Marshall and Bayliss (1994) Flood Estimation for Small Catchments, Report 124, Institute of Hydrology, Wallingford, Oxon, UK.



May 2016

The FSR WRAP Map, shown in Appendix 3, indicates the site is located in ‘Soil Index Class 4’, 5.30.which has high standard percentage runoff and suggests the underlying soil has relatively poor permeability. A Soil Index value of 0.45 has been used to calculate QBAR using the ICP SuDS Method.

QBAR has been calculated for the site in an undeveloped state. Copies of the MicroDrainage 5.31.greenfield runoff calculations are included in Appendix 6. A summary of the pre development greenfield runoff rates for the various return period events is shown in Table B. Values of greenfield runoff rates for 1 in 100 year plus 20% and 40% climate change allowance have been manually calculated and added to the table. The mean annual peak rate of runoff, referred to as QBAR in ICP SuDS Method, for the pre-development greenfield site is 8.2 l/s.

Table B: Greenfield Runoff Rates

Return Period (Years) 1 QBARa 30 100 100+20% 100+40%

Greenfield Runoff Rates (l/s) 7.0 8.2 18.6 26.1 31.3 36.5 a

QBAR = Mean Annual Flood with an approximate return period of 2.3 years.

By limiting the developed rate of runoff to the mean annual peak rate of runoff, QBAR, for all 5.32.rainfall events up to the 100 year return period event, including an allowance for climate change, the proposed development would reduce flood risk overall when compared to existing greenfield rates.

Brownfield Runoff Rates Warwickshire County Council’s ‘DRAFT Flood Risk and Drainage Planning Advice – Version 2’ 5.33.

states “To establish an acceptable brownfield discharge rate, WCC recommends that a minimum of 50% betterment is applied to the lowest value based on the following assessments:

b) Estimate using either the rational method or modified rational method, using the industry standard figure of 35 mm/hr as recommended in Part E of the CIRIA Guidance document X108 ‘Drainage of development sites’.”.

The Rational Method equation is set out below: 5.34.

Q (l/s) = 2.78 x l (mm/hr) x A (ha)

The rainfall intensity (l) has been set as an industry standard figure of 35 mm/hr as 5.35.recommended. The pre development site is entirely impermeable and so the impermeable area of 1.935 ha has been used in the above equation. This results in a peak flow of 188.28 l/s. The result of this exercise is reproduced below.

Q (l/s) = 2.78 x 35 (mm/hr) x 1.935 (ha) = 188.28 (l/s)

This is a much higher flow rate than the greenfield runoff rate calculate above. Therefore, 5.36.restricting runoff to greenfield rates will be a significant benefit.

Proposed Surface Water Flow Balancing and Post Development Runoff Rates The use of flow balancing methods, comprising a pipe system with online below ground 5.37.

geocellular tank, are proposed in order to attenuate surface water runoff to greenfield runoff rates with discharge to the local public sewer system.



May 2016

Preliminary storage calculations have been undertaken to establish the required storage for the 5.38.development catchment areas on the site using the Quick Storage Estimate module in XP Solutions’ Micro Drainage software system (Version 2015.1) for the 1 in 1, 30 and 100 year events plus a 20% and 40% increase in peak rainfall intensity to take account of climate change. The outflow from the drainage system has been constrained to 1:1 year QBAR, and hence a reduced rate of runoff for higher return periods. Copies of the Micro Drainage results summaries for the development catchment areas are reproduced in Appendix 7 and Table C below.

Table C: Proposed Surface Water Drainage Network

The attenuation tank shown on the Indicative Surface Water Drainage Arrangements Plan, 5.39.Drawing No. K116/03 Rev. B in Appendix 5, indicates the location and sizes of the required storage facilities to serve the various development areas and is subject to detailed design.

The above plan and calculations demonstrate that a suitable means of drainage can be provided 5.40.to drain the developed site in terms of surface water runoff in accordance with the relevant guidance and standards.

Non-Statutory Technical Standards for SuDS The Department for Environment, Food and Rural Affairs (DEFRA) published its ‘Sustainable 5.41.

drainage systems: non-statutory technical standards for sustainable drainage systems’ in March 2015 which should be used in conjunction with the National Planning Policy Framework and planning practice guidance.

Table D demonstrates how the proposed development complies with the standards set out in the 5.42.non-statutory technical standards.

Table D: Compliance with non-statutory technical standards for sustainable drainage systems

Standard Justification for compliance

Flood risk outside the development

S1 N/A – drainage system discharges to a public sewer system. Therefore S2, S3, S4 and S6 apply.

Peak flow control

S2 N/A – site is a brownfield development.

S3 Surface water discharge rates have been restricted to the QBAR greenfield runoff rates which are reported in Table B of this report. The outflow rates from the drainage system are reported in Table C of this report and satisfy requirements of S3.

Volume control

S4 N/A – site is a brownfield development.

S5 & S6 The extent of impermeable area in pre development site is approximately 100% and it will not change as a result of the proposed development.

Critical Storm Event

1 30 100 100 + 20% 100 +40%

Greenfield Runoff Rate (l/s) 7.0 18.6 26.1 31.3 36.5

Approximate Attenuation (m3)

a 223.37 667.41 968.99 1205.24 1444.91

Calculated Discharge Rate (l/s) 6.9 6.9 6.9 6.9 7.0 a Notes: Includes storage in pipe network



May 2016

Flood Risk within the development

S7 The surface water drainage system has been designed so that no flooding of the site occurs during the 1 in 30 year rainfall event. S7 is therefore satisfied based on the calculations contained in Appendix 7.

S8 As the calculations contained in Appendix 7 show that no flooding occurs within the surface water drainage network as a result of the 1 in 100 year storm event, it follows that no flooding of property occurs within the 100 years storm event and S8 is therefore satisfied.

S9 For extreme events (greater than 1 in 100 year storm) the proposed development will intercept any uncontrolled overland flow and direct it into the proposed drainage system. During extreme rainfall the site levels will be designed to direct exceedance flows towards the existing public sewer system.

Structural integrity

S10

The detailed design of the surface water drainage system will comply with this standard. The geocellular storage will be designed to maximum vehicle loading (loaded HGVs) in accordance with manufacture’s specification following a ground investigation.

S11

The preliminary surface water drainage design outlined in Appendix 5 of the FRA demonstrates it is feasible to drain the site based on geocellular storage and oversized pipes. The materials will be specified by the designer at the detailed ‘technical’ design stage.

Designing for maintenance considerations

S12 N/A - Pumping is not proposed.

Construction

S13

The proposed surface water drainage network will connect into the existing public sewer within the Faraday Avenue, approximately 200m to the south east of the development site. The detailed design and construction of the system will ensure that the made of communication with the existing drainage system would not be prejudicial to the structural integrity and functionally of the drainage system.

S14 Drainage system to be inspected prior to site handover and any faults rectified.

Flood Risk Management Measures

Minimum Ground Floor Levels Minimum ground floor levels for all built development on the site will be set at least 150 - 300mm 5.43.

above the general ground level.

Off Site Impact By restricting the rate of runoff to greenfield rates and intercepting uncontrolled overland flows 5.44.

the proposed development will reduce flood risk overall.

Overland Flood Flow Paths Overland flood flow paths would follow the current topography of the land, as per the existing 5.45.

scenario, and flow towards the existing public sewer system in the Faraday Avenue. The proposed surface water drainage network would intercept overland flows.



May 2016

Flood Risk Management Measures A summary of the potential risk from all sources of flooding post-development with the various 5.46.

development mitigation measures incorporated is shown in Table E below.

Table E: Post-development Potential Flood Risk from All Sources of Flooding

Flood Source Potential Risk

Description Very Low Low Medium High

Watercourses X

The site is located in Flood Zone 1, which refers to less than 1 in 1000 annual probability of river or sea flooding (<0.1%).

Surface Water X

The risk would be further mitigated by providing a surface water drainage network which intercepts any surface water flows.

Groundwater X

The SFRA does not identify any groundwater flooding affecting the site.

Overwhelmed Sewers X

Provision of suitable designed sewer system to adoptable standards connecting into the public system will mitigate future risk.

Artificial Sources X The site is not affected

Off-site Impacts X

By reducing the rate of runoff and intercepting overland flows the proposed development would reduce flood risk overall.

By reducing the rate of runoff and intercepting overland flows the proposed development would 5.47.reduce flood risk overall.

Safe Access and Egress Safe access and egress to and from the development is a route that is safe for use without the 5.48.

intervention of the emergency services or others. The site and surrounding road network, are not affected by flooding and so it is considered that safe access and egress routes will be available.

Residual Risk Paragraph 41 in Section 14 of the Flood Risk and Coastal Change Planning Practice Guidance25 5.49.

advises that residual risks are those remaining after applying the sequential approach to the location of development and taking mitigating actions.

The site lies within Flood Zone 1 and so the proposed development is fully in accordance with the 5.50.sequential approach to development set out in the NPPF, the aim of which is to steer new development to areas with the lowest probability of flooding.

The proposed drainage measures would ensure that there is little or no residual risk of property 5.51.flooding occurring during events well in excess of the minimum acceptable standard of protection for new property, which requires that no flooding of property should occur as a result of a one in 100 year storm event including an appropriate allowance for climate change.

25

Planning practice guidance reference ID: 7-041-20140306



May 2016

For extreme events it is considered that the proposed development would intercept any 5.52.uncontrolled overland flow and direct it into the proposed drainage system. The proposed drainage measures would ensure the proposed development would have adequate flood protection for extreme events over the lifetime of the development.

Proposed Foul Water Drainage Arrangements Enquiries have been made to Severn Trent Water to establish the location of the existing public 5.53.

sewers in the vicinity of the site. A copy of a public sewer map is reproduced in Appendix 8 and an extract of the public sewer map is reproduced in Figure 4 below.

Figure 4: Severn Trent Water Public Sewer Map Extract

The public sewer map indicates there are existing public surface and foul water sewers located to 5.54.the south west and south east of the site.

In terms of the adequate point of connection for surface and foul flows from the proposed 5.55.development to the public water sewer system it is proposed to connect to the sewer located south east to the site.

In terms of foul drainage, it has been demonstrated that a suitable connection point (to the south 5.56.east of the site) can serve the proposed development.



May 2016

Maintenance Strategy Paragraph 85 in Section 21 of the Flood Risk and Coastal Change Planning Practice Guidance26 5.57.

advises that when planning a sustainable drainage system, developers need to ensure their design takes account of maintenance requirements of both surface and subsurface components so that it continues to provide effective drainage for properties.

In terms of the maintenance strategy for the proposed drainage measures, the main off-site 5.58.surface and foul water drainage systems would be adopted by Severn Trent Water, in its role as sewerage undertaker, under a Section 104 Agreement of the Water Industry Act 1991. Severn Trent Water would therefore be responsible for the future maintenance of the adopted drainage systems

It is proposed that the surface water drainage system (including the below ground geocellular 5.59.tank) would be adopted and maintained by the site owner and specialist Management Company. This is in accordance with the current arrangements.

The proposed maintenance procedures for attenuation tanks are set out in Table F. 5.60.

Table F: Attenuation Tank Maintenance Procedures

Maintenance Schedule Required Action Frequency

Regular Maintenance

Inspect and identify any areas that are not operating correctly. If required, take remedial action.

Monthly for 3 months, then annually

Remove debris from the catchment surface (where it may cause risks to performance).

Monthly

Remove sediment from pre-treatment structures and/or internal forebays

Annually, or as required

Remedial actions Repair/rehabilitate inlets, outlet, overflows and vents

As required

Monitoring

Inspect/check all inlets, outlets, vents and overflows to ensure that they are in good condition and operating as designed

Annually

Survey inside of tank for sediment build-up and remove if necessary

Every 5 years or as required

Guidance on the operation and maintenance requirements of sustainable drainage systems is 5.61.contained in The SuDS Manual (CIRIA C753). There are three categories of maintenance: regular, occasional and remedial. The Management Company would be responsible for putting in place a suitable maintenance plan.

Regular maintenance consists of basic tasks including litter and debris removal, and includes 5.62.inspections and monitoring to identify potential system failures such as blockages, silt and sediment build-up, eroded or damaged areas, and condition of inlets and outlets.

Occasional Maintenance comprises tasks that are likely to be required periodically for example 5.63.sediment removal and jetting of gullies.

Remedial Maintenance comprises intermittent tasks to rectify faults and would comprise 5.64.inlet/outlet repairs, erosion repairs, and dealing with a spillage event.

26

Planning practice guidance reference ID: 7-085-20150323



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6. CONCLUSIONS

This Flood Risk Assessment and Drainage Strategy has been prepared on behalf of Rolton Kilbride 6.1.in connection with proposals for a Renewable Energy Centre development that generates power and heat located within Hams Hall Industrial Park in Coleshill.

The overall site comprises approximately 1.96 hectares, and is located within Hams Hall Industrial 6.2.Park in Coleshill, east of the Birmingham to Derby Railway Line and north to the Hams Hall Rail Freight Terminal. The site lies in a great hook of the River Tame.

Hams Hall is allocated as an ‘Employment Site’ in North Warwickshire Borough Council’s 6.3.Development Management Plan – Draft Policies 2015 (Policy DM3). Policy DM3 lists Hams Hall as an existing industrial estate designated for local employment purposes with permitted changes of use between the B1 light industrial, B2 general industrial and B8 warehouse and distribution Use Classes.

The site has been cleared of buildings and currently consists of consolidated land covered by 6.4.crushed hardcore and rubble. The site is effectively flat and slopes from maximum level of 80.09m AOD in south-western corner of the site to 79.16m AOD in south-eastern corner.

The nearest water features are two small ponds located in the vicinity of Faraday Avenue and 6.5.Canton Lane roundabout approximately 0.3km east of the site. The River Tame is a main river and is approximately 0.7km to the north-east of the site at its nearest point.

From an inspection of the Flood Map it can be seen that the entire site falls within Flood Zone 1 6.6.which indicates the lowest risk of flooding, having a less than 1 in 1000 annual probability of river or sea flooding. Consequently, the Sequential Test is satisfied.

It is considered the pre-development potential flood risk to the site from all sources of flooding is 6.7.considered to be very low.

A sustainable drainage strategy, involving the implementation of SuDS, is proposed for managing 6.8.the disposal of surface water runoff from the proposed development on the site.

It is considered that the use of infiltration devices for site drainage is not appropriate for the site 6.9.due to impermeable soils. Site flow balancing methods with discharge to an offsite public sewer are proposed in keeping with the site’s existing surface water drainage arrangements. The proposed flow balancing method comprises a pipe system with an online below ground attenuation tank, in order to attenuate surface water runoff to greenfield runoff rates.

This strategy takes account of the most recent advice and policy regarding climate change 6.10.allowances and surface water drainage.

Pollution control measures are incorporated into the surface water drainage network and will 6.11.include the use of deep trapped gullies and full retention separators in accordance with BS EN 858-2:2003.

It is considered that these arrangements satisfy the requirements of DEFRA’s ‘Sustainable 6.12.drainage systems: non-statutory technical standards for sustainable drainage systems’.

To minimise residual flood risk it is proposed that the finished floor level of any buildings and 6.13.sensitive plant is raised by 150 – 300 mm above the existing ground as is standard practice.



May 2016

The proposed drainage measures would ensure that there is little or no residual risk of property 6.14.flooding occurring during events well in excess of the minimum acceptable standard of protection for new property, which requires that no flooding of property should occur as a result of a one in 100 year storm event including an appropriate allowance for climate change.

An outline maintenance strategy for the proposed foul and surface water drainage measures has 6.15.been set out in this document. It is proposed that the surface water drainage system (including the below ground geocellular tank) would be adopted and maintained by the site owner or a specialist Management Company.

For extreme events it is considered that the proposed development would intercept any 6.16.uncontrolled overland flow and direct it into the proposed drainage system. The proposed drainage measures would therefore ensure the proposed development would have adequate flood protection for extreme events over the lifetime of the development.

It is considered that the proposed foul and surface water drainage arrangements can be covered 6.17.by a suitably worded condition requiring the submission of details to be submitted to and approved by the Local Planning Authority.

The overall conclusions drawn from this Flood Risk Assessment are that the development would 6.18.be appropriately safe for its lifetime taking account of the vulnerability of its users, the development would not increase flood risk elsewhere, and would reduce flood risk overall.

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