Flood Map for Surface Water

Transcription

PROPOSED RESIDENTIAL DEVELOPMENT
ANSTEY ROAD, ALTON, HAMPSHIRE
Flood Risk Assessment and
Surface Water Drainage Strategy
Report No. 13-193-01
December 2013
Flood Risk Assessment and
Odyssey Markides LLP
Tuscany House
White Hart Lane
Basingstoke
Hampshire
RG21 4AF
Tel: 01256 331144
Fax: 01256 331134
[email protected]
Project No. 13-193
December 2013
13-193-01
Flood Risk Assessment and Surface Water Drainage Strategy
December 2013
________________________________________________________________________
DOCUMENT CONTROL SHEET
REV
ISSUE PURPOSE
AUTHOR
CHECKED
REVIEWED
APPROVED
DATE
-
First Issue
SW/TS
SJO
RS
BAC
Dec 13
A
Updated to suit revised
LH
TS
LH
BAC
Jan 14
layout
SW/sw/Reports/13-193-01
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CONTENTS
PAGE
Executive Summary
1.
Introduction
1
2.
Development Proposals
2
3.
Baseline Conditions
3
4.
Flood Risk Legislation and Policy Review
6
5.
The Sequential Test & The Exception Test
14
6.
Flood Risk Methodology
16
7.
Appraise Key Sources of Flood Risk
17
8.
Flood Risk Mitigation Measures
20
9.
Appraisal of Residual Flood Risk
23
10.
24
11.
Foul Drainage Strategy
28
12.
Impact on Other Land
29
13.
Conclusions
30
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APPENDICES
Figure 1
Site Location Plan
Appendix A
Proposed Masterplan
Appendix B
Topographical Survey
Appendix C
Groundwater and Flood Mapping - Environment Agency
Appendix D
Strategic Flood Risk Assessment Extracts – East Hampshire
District Council
Appendix E
Sewer Record Extracts – Thames Water Utilities Limited
Appendix F
Ground Investigation Extracts
Appendix G
Environment Agency Correspondence
Appendix H
Outline Drainage Strategy (Drawing no. 13-193-001)
Appendix I
Micro Drainage Surface Water Storage Calculations
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EXECUTIVE SUMMARY
Odyssey Markides has been commissioned by BNP Paribas to prepare a Flood Risk
Assessment incorporating a Foul and Surface Water Drainage Strategy to accompany
their planning application for the proposed residential development Anstey Road,
Alton, Hampshire.
Environment Agency mapping shows the proposed development to be in Flood Zone 1
where the probability of flooding due to tidal and/or fluvial sources is less than 0.1%.
The Flood Risk Assessment will bring together existing information collected from a
variety of sources to identify all risk of flooding including fluvial, pluvial, surface water,
groundwater, and sewer infrastructure flood risk that maybe associated with the
proposed development site.
In accordance with the National Planning Policy Framework 2012 the site requires a
site specific Flood Risk Assessment as the site area is in excess of 1 hectare.
The main aim of this combined Flood Risk and Conceptual Drainage Strategy is to
prove the viability and sustainability of the development proposals with regards to
fluvial, pluvial, surface water, groundwater and sewer infrastructure flood risk.
The Flood Risk Assessment demonstrates that the proposed development can be
safeguarded against the risks from the primary sources of flooding for its lifetime and
not exacerbate flood risk to neighbouring development.
The methodology for producing this FRA is based on the Communities & Local
Government's document National Planning Policy Framework, and Environment
Agency guidelines.
The Conceptual Surface Water Drainage Strategy is based on Environment Agency
requirements and has demonstrated that the site development proposals can cater for
storm events up to and including the predicted 1 in 100 year plus 30% climate change
by way of a Sustainable Drainage System.
The risk of flooding by fluvial, tidal, groundwater and overland flow sources has been
reviewed and considers the risk to be negligible.
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The site being in Flood Zone 1 classifies the site as having a low probability of fluvial
flooding precluding the necessity for Sequential or Exception Testing and is therefore
deemed to satisfy the NPPF.
The on-site foul water drainage proposals offer a gravity network to the south of the
site with connection into the on-site Thames Water network located along the southern
boundary of the site. Connection of the foul drainage system from the development
will be subject to a Section 106 Application in accordance with the Water Industry Act
with Thames Water.
This Flood Risk Assessment has demonstrated that the proposed development is fully
compliant with the requirements of NPPF. Issues relating to flood risk and drainage do
not represent an obstruction to the development and therefore should not hinder an
approval for planning permission of the proposed development.
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1.0
INTRODUCTION
1.1
Odyssey Markides LLP have been commissioned by BNP Paribas to
undertake a Flood Risk Assessment (FRA) and Surface Water Drainage Strategy
(SWDS) to support
the outline planning application for a proposed residential
development on land adjacent to Anstey Road in Alton, Hampshire. A site location
plan is presented as Figure 1.
1.2
The site is approximately 2.2ha and is currently occupied by a sports ground
with tennis courts, club house, bowling green and pavilion. The proposals comprise
up to 85 residential units with associated infrastructure and landscaping. A copy of
the proposed masterplan can be found in Appendix A.
1.3
This report comprises the following elements:

Review existing legislation, policy and supporting documents in relation
to flood risk and foul and surface water;

Review all elements which may cause or increase the risk of flooding to
the development and the local vicinity;

Demonstrate through use of sustainable drainage systems (SuDS) that
any potential flooding on this site can be safely mitigated;

Prepare surface and foul water drainage strategies illustrating how the
site can be drained effectively and in accordance with the requirements
of East Hampshire District Council (EHDC), Hampshire County Council
(HCC), the Environment Agency (EA) and Thames Water Utilities
Limited (TWUL).
1.4
This FRA has been prepared in accordance with the requirements set out in
the National Planning Policy Framework (Communities and Local Government,
March 2012) (NPPF), EA Guidance and correspondence and TWUL requirements.
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2.0
DEVELOPMENT PROPOSALS
2.1
The development proposals comprise up to 85 dwellings with associated
landscaping and infrastructure. The proposed masterplan is presented as
Appendix A.
2.2
Access to the residential development will be via a new junction with Anstey
Road, on the north-western boundary of the scheme.
2.3
Surface water run-off will be managed using a SuDS management train
making use of permeable paving and soakaways across the site.
2.4
The foul water drainage system will be designed in accordance with TWUL
requirements and will discharge to the existing on-site public foul sewer in the south
of the site, subject to a capacity check and agreement with TWUL. The foul
drainage strategy is discussed in detail in Chapter 11.
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3.0
BASELINE CONDITIONS
Sources of Information
3.1
The baseline conditions for this site have been established using the
following sources and references:

EA mapping;

TWUL Asset location plans;

British Geological Survey (BGS) mapping;

Existing Topographical Survey undertaken by Shaw Colegate Land and
Building Surveyors;

East Hampshire District Council (EHDC) Strategic Flood Risk Assessment
(SFRA);

Phase
1
Desk
Top
Study
by
Soils
Environmental
Services
Ltd
(SES/BNPP/SG1#1);

Trial
Pits
and
Soakaway
Tests
by
Geo-Environmental
(ref:
GE9613/GR02/131023)
Site Description
3.2
The site is bounded to the north-west by Anstey Road, to the north-east by
existing residential development, to the south-east by the Alton Line railway and to
the south-west by existing residential development. The approximate centre of the
site is at Ordnance Survey (OS) Grid Reference 472625E, 140055N.
3.3
The site is currently occupied by a sports ground and associated club house,
pavilion, tennis courts and a bowling green.
Site Topography
3.4
The site generally slopes from north-west to south-east. The highest level on
the site is approximately 105.66 mAOD near the north-west boundary of the site, the
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lowest level is approximately 102.72 mAOD in the south-east of the site. A copy of
the topographical survey can be found in Appendix B.
Geology
3.5
BGS mapping indicates that the bedrock beneath the site is the Zig Zag
Chalk Formation which comprises Chalk. The superficial stratum has been recorded
as River Terrace Deposits, 2 - Sand and Gravel.
3.6
Intrusive ground investigations including falling head infiltration testing has
been conducted on this site. Trial pits were excavated to a depth of 0.8m bgl (below
ground level). The results of the investigations indicate that the site is underlain by
River Terrace Deposits.
Hydrology
3.7
The EA’s Flood Map indicates that the site is located in Flood Zone 1. The
EA’s Flood Map is presented as part of Appendix C.
3.8
The River Wey is the closest watercourse to the site and is located
approximately 200m south-east of the site and flows from south-west to north-east.
Hydrogeology
3.9
Groundwater mapping published by the EA indicates that the site is located
over a Groundwater Vulnerability Zone designated Major Aquifer – High, with the
bedrock beneath the site designated as a Principal Aquifer and the superficial
deposits designated Secondary Aquifer A. It is not located over a groundwater
source protection zone.
The EA’s groundwater mapping is presented as part of
Appendix C.
3.10
EHDC’s SFRA indicates that there has been no known groundwater flooding
events within the vicinity of the site. Extracts from the SFRA are presented as
Appendix D.
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Existing Surface Water Drainage Regime
3.11
The existing site generally falls from north-west to south-east, towards the
Alton Railway Line. A TWUL surface water sewer exists north of the site in Anstey
Road. It is not clear if the site currently connects to the public surface water sewer.
Existing Foul Water Drainage Regime
3.12
A foul sewer currently crosses the south of the site conveying flows from
north-east to south-west, before heading south beneath Alton Railway Line,
eventually leading to Alton Sewage Treatment Works. Extracts from the TWUL
sewer records are presented as Appendix E.
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4.0
FLOOD RISK LEGISLATION AND POLICY REVIEW
Legislation
Flood and Water Management Act 2010
4.1
The Flood and Water Management Act 2010 (FWMA) received Royal Assent
on 8th April 2010. The Act was introduced to enforce some of the key proposals set
out within UK Government flood and water strategies along with the UK
Government’s response to Sir Michael Pitt’s Review of the summer 2007 floods.
4.2
Relevant to development sites, the FWMA is intended to encourage the
uptake of SuDS by removing the automatic right to connect to sewers and providing
for unitary and County Council’s to adopt SuDS for new developments.
4.3
The development proposals will adhere to the FWMA through the provision of
SuDS as a fundamental element of the surface water drainage system.
Furthermore, BNP Paribas are committed to working with the relevant stakeholders,
such as the EA, EHDC, HCC in implementing the requirements of the FWMA.
Flood Directive - The Flood Risk Regulations 2009
4.4
The Flood Risk Regulations 2009 came into force on 10th December 2009,
transporting the European Floods Directive into domestic law. In essence the
Regulations require the EA to prepare flood risk assessments, maps and plans for
sea, main river and reservoir flood risk and will require lead local flood authorities
(unitary and county councils) to do the same for all other forms of flooding.
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National Policy
National Planning Policy Framework 2012
4.5
The National Planning Policy Framework 2012 (NPPF) replaced all planning
policy statements (including Planning Policy Statement 25: Development and Flood
Risk) upon publication in March 2012.
4.6
The NPPF sets out the Government’s planning policies for England and
Wales, and how these policies should be applied. The Technical Guidance to the
NPPF (TG) published in unison with the NPPF provides additional guidance and
retains the key elements of the now superseded PPS25.
4.7
The NPPF states that “inappropriate development in areas at risk of flooding
should be avoided by directing development away from areas of highest risk, but
where development is necessary, making it safe without increasing flood risk
elsewhere.”
4.8
When determining planning applications, local planning authorities should
ensure flood risk is not increased elsewhere and only consider appropriate
development in areas at risk of flooding where, following application of the
Sequential Test (and if required, the Exception Test) it can be demonstrated that:

Within the site, the most vulnerable development is located in areas of
lowest flood risk unless there are overriding reasons to prefer a different
location; and,

Development is appropriately flood resilient and resistant, including safe
access and escape routes where required, and that any residual risk can
be safely managed, including by emergency planning; and it gives
priority to the use of Sustainable Drainage Systems. (NPPF, 2012)
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4.9
All land in England and Wales is classified into three main Flood Zones
which refer to the probability of river or sea flooding (ignoring the existence of
defences). The TG identifies and describes the EA Flood Zones as:

Flood Zone 1: Low Probability defined as land assessed as having less
than 1 in 1,000 annual probability of river or sea flooding (<0.1%),

Flood Zone 2: Medium Probability defined as land assessed as having
between 1 in 100 and 1 in 1,000 annual probability of river flooding (1% 0.1%) or between 1 in 200 and 1 in 1,000 annual probability of sea
flooding (0.5% - 0.1%),

Flood Zone 3a: High Probability defined as land assessed as having a 1
in 100 or greater annual probability of river flooding (≥1%), or a 1 in 200
or greater annual probability of sea flooding (≥0.5%),

Flood Zone 3b: The Functional Floodplain defined as land where water
has to flow or be stored in times of flood (as identified by local planning
authorities in their SFRA's).
4.10
In accordance with the NPPF. A site specific FRA is required for:

Proposals of 1 hectare or greater in Flood Zone 1,

All proposals for development in Flood Zones 2 and 3,

An area within Flood Zone 1 which has critical drainage problems,

Development or change of use to a more vulnerable class that may be
subject to other sources of flooding.
4.11
Given the above, the site requires a site-specific FRA on the basis that the
site is in excess of one hectare even though the area of development is located
within Flood Zone 1.
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4.12
Greenfield sites rely on natural drainage to convey or infiltrate rainfall. In
general, site development can reduce the permeability of the site if not well
designed, increasing the volume and rate of surface water running off the site to
nearby watercourses. This in turn potentially increases flood risk to downstream
areas. Therefore appropriate drainage flow regulation arrangements may be
required for new developments to ensure that flood risk to others is not increased
and attempts to mimic the existing characteristics of the site in the form of SuDS
wherever physically possible.
National Standards for Sustainable Drainage Systems 2011
4.13
The National Standards for Sustainable Drainage Systems (NSSDS) was
published in draft format in December 2011. This Department for Environment, Food
and Rural Affairs (DEFRA) document provides guidance on designing, constructing,
operating and maintaining drainage for surface run-off.
4.14
The standards are to be used in order to manage surface run-off in
accordance with Schedule 3 of the FWMA.
4.15
The standards state the run-off destination should be considered in the
following order of preference:
4.16

Discharge into the ground (infiltration);

Discharge to a surface water body;

Discharge to a surface water sewer;

Discharge to a combined sewer.
Although yet to be formally adopted, the NSSDS provides guidance on run-
off destination, peak flow rate, volume and control of water quality and function.
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4.17
The NSSDS sets out the requirements in order to obtain approval from the
SuDS Approving Body (SAB) for operating and maintaining SuDS. In addition to the
standards, the Local Planning Authority may set local requirements for planning
permission that have the effect of more stringent requirements than that of the
standards.
East Hampshire District Strategic Flood Risk Assessment
4.18
East Hampshire District Council are required to produce a Strategic Flood
Risk Assessment (SFRA) in accordance with the now superseded Planning Policy
Statement 251 (PPS25) and; Development & Flood Risk, a Practice Guide
Companion to the PPS25. The SFRA will “…inform the plan-making process of the
a Local Development Framework” and “…in particular inform the Core Strategy, the
Development Control Policies and the Development Provisions and Allocations
documents”.
4.19
The East Hampshire District Strategic Flood Risk Assessment (April 2008), a
living document, will inform Local Planning Authorities of flood related issues within
the District, aiding the decision process for development provision and allocations
via the Sequential Approach and Sequential Test as defined by NPPF.
4.20
The objective of the SFRA is to reduce the exposure of new developments to
flooding and minimise exacerbating risk to existing developments and reduce the
reliance on long-term maintenance of built flood defences.
4.21
The SFRA is a Level 1 study presented in a single main report document
with figures and appendices providing additional flood mapping information.
4.22
Tile Flood Maps A to E represent flood extents, produced by the Environment
Agency in December 2007 as derived from the ‘Jflow’ generalised computer
modelling. It should be noted that ‘Jflow’ is a ‘coarse modelling approach’ with a
large number of assumptions incorporated within the model. In some locations the
river centreline incorporated into Jflow modelling was found to be erroneous with the
result that the associated flood plains deviate from the natural valleys, as evident on
the tile flood maps.
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4.23
The tile flood maps can still be used to identify locations of Localised
Flooding Areas (relate to historical flooding at individual locations), sewerage
undertaker’s sewer flooding incidents and flooding due to other sources.
The Water Industry Act 1991
4.24
The Water Industry Act 1991 (WIA) (HMSO, 1991) was introduced to
consolidate previous water supply and wastewater services enactments in the UK.
Section 94 sets out the principal duties and standards of performance to sewerage
undertakers which include the duty ‘to provide, improve and extend such a system
of public sewers (whether inside its area or elsewhere) and so to cleanse and
maintain those sewers as to ensure that that area is and continues to be effectually
drained’.
4.25
Relevant to new development, Section 104 and Section 106 of the WIA
provides the framework for the adoption of sewers, subject to an agreement with the
sewerage undertaker, who in this case is TWUL.
4.26
Section 98 of the WIA provides the legal mechanism through which the
appropriate infrastructure can be requested (by the developer) and provided to drain
a specific location off-site through third party land.
4.27
Section 106 allows the sewerage undertaker a 21 day notice period prior to
the connection works being undertaken. During this time the application may be
refused if the undertaker considers that the connection mode or condition of the
connecting sewer does not satisfy the required standards. The undertaker cannot
refuse the connection based on inadequate capacity.
Transfer of Private Sewers
4.28
It should be noted that the Water Industry (Schemes for Adoption of Private
Sewers) Regulations 2011 has transferred private sewers into the ownership of
statutory sewerage companies in England since October 2011. The Government
are also taking steps to stem the proliferation of newly built sewers in order to
prevent the recurrence of existing ownership/maintenance problems in the future.
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Pitt Review
4.29
In response to the severe flooding in the UK during the summer of 2007, the
government commissioned an independent review on lessons to be learned. The
Pitt Review was comprehensive and considered all stages of flooding preparedness, response and recovery - as well as the coordination, responsibilities,
and legislation necessary to ensure the UK can advance in the area of flood risk
management.
Sewers for Adoption 7th Edition
4.30
Sewers for Adoption (SFA) 7th Edition provides guidance for developers for
the design and construction of both surface and foul water sewers to be offered for
adoption.
The guidance is provided in consultation with Water Undertakers.
However, please note that whilst SFA 7th Edition is the latest publication, until
Section 42 of the FWMA is enforced SFA 6th Edition can still be implemented.
4.31
The SFA places responsibility (in England and Wales) for existing and future
private sewers and lateral drains that connect to the public sewer system to the
water and sewerage companies.
4.32
The SFA will provide detailed guidance to support the Mandatory Build
Standard whereby; it will be mandatory for new sewers and lateral drains (between
the sewer and the serviced property boundary) to be adopted to public status by the
sewerage undertaker.
4.33
The guidance for foul sewer design in Sewers for Adoption states:
‘The design of flows for gravity sewers for residential developments should
be 4,000 litres/unit dwelling/per 24 hours.’
Building Regulations
4.34
Where drainage within a development is not to be adopted by the sewerage
undertakers, the so called private sewers will require to meet the standards as set
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out in Building Regulations 2002, Part H ‘Drainage and Waste Disposal’ guidance
on the design of private sewers.
4.35
Specific guidance can be found within the following sections of the Building
Regulations 2002 Part H.

H1 – Foul water drainage

H2 – Wastewater treatment systems and cesspools

H3 – Rainwater drainage

H4 – Building over sewers

H5 – Separate systems of drainage

H6 – Solid waste storage
Pollution Prevention Guidance
4.36
For sewers not connected to a public adopted system, the Environment
Agency’s Pollution Prevention Guidance 4 (PPG4) ‘Treatment and Disposal of
Sewage where no foul sewer is available’ should be considered.
However this
guidance states that “discharge to a foul sewer is the preferred option as the
sewage is conveyed to a purpose built and closely monitored sewage treatment
plant, so development proposals in sewered areas should connect to public sewers.”
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5.0
THE SEQUENTIAL TEST AND THE EXCEPTION TEST
The Sequential Test
5.1
The EA flood zones are the starting point for the Sequential approach
promoted by the NPPF, and are shown on the EA’s flood mapping. The TG
identifies that the overall aim of the Sequential Test is to steer new development to
Flood Zone 1 (NPPF, 2012).
5.2
As stated by the NPPF, development should not be allocated or permitted if
there are reasonably available sites appropriate for the proposed development in
areas with lower probability of flooding. The SFRA will provide the basis for applying
this test. (NPPF, 2012).
5.3
Following application of the Sequential Test, if it is not possible for the
development to be located in zones with a lower probability of flooding (Flood Zone
1), proposed sites should take into account the flood risk vulnerability of land uses
(Table 2, TG) and consider reasonable sites in Flood Zone 2, and apply the
exception test if required (Table 3, TG).
Only where there are no reasonably
available sites in Flood Zone 1 and Flood Zone 2 should the suitability of sites in
Flood Zone 3 be considered, taking into account the flood risk vulnerability of land
uses and applying the exception test if required.
The Exception Test
5.4
For the Exception Test to be passed a development proposal:

Must demonstrate that the development provides wider sustainability
benefits to the community that outweigh flood risk, informed by a SFRA;

The development should be on developable brownfield land or, if not, it
must be demonstrated that there is no such alternative land available;
and

A FRA must demonstrate that the development will be safe for its lifetime
taking into account the vulnerability of its users, without increasing flood
risk elsewhere, and where possible, reducing flood risk overall.
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5.5
The
proposed
development’s
suitability
and
vulnerability
meet
the
requirements as set by the Sequential Test criteria for Flood Zone 1, therefore,
satisfying the NPPF.
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6.0
FLOOD RISK METHODOLOGY
Development Proposal
Local Strategy Development Plan
Site Visit/Desk Study
Flood Risk
Appraise Sources of Flooding
Mitigate Flood Risk
Appraise Residual Flood Risk
Proposed Development Strategy
The assessment methodology is based on the requirements of NPPF.
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7.0
APPRAISE KEY SOURCES OF FLOOD RISK
7.1
In accordance with the NPPF requirement, all forms of flooding must be
considered within a site specific FRA to satisfy the EA. The following is a review of
the various types of flooding and an overview of the potential risk to the site, if any.
Flooding from the Sea (Tidal)
7.2
Tidal flood sources include the sea and estuaries, and tidal flooding is often
caused by high tides with meteorological and storm events. Tidal flooding can be
extremely rapid and its effects severe; deep fast-flowing water can create an
extreme hazard.
7.3
The site is located inland and beyond the effects of tidal flooding. Therefore,
the site is not considered to be at risk from tidal flooding.
Flooding from Rivers (Fluvial)
7.4
Fluvial flooding is caused by high flows in rivers or streams exceeding the
capacity of the river channel and spilling into the floodplain, or in some cases none
designated flood plain which can occur after a period of heavy rainfall.
7.5
EA Flood Zones cover all watercourses with an upstream catchment area of
3km2 or greater.
7.6
Flood Mapping obtained from the EA website indicates the extents of the site
to be within Flood Zone 1, low probability (≤0.1%) of flooding. A copy of the EA’s
flood map is presented as part of Appendix C.
Groundwater Flooding
7.7
Groundwater flooding is caused by the emergence of water originating from
sub-surface permeable strata. A groundwater flood event results from a rise in the
groundwater level sufficient for the water table to intersect the ground surface and
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inundate low lying land. Periods of prolonged rainfall may also be a cause of
groundwater flooding with aquifers and soil becoming saturated.
7.8
EHDC’s SFRA mapping indicates that the proposed development lies within
an area that has not been affected by groundwater flooding in the past. Extracts
from the EHDC’s SFRA are presented as Appendix D.
7.9
Groundwater monitoring should be conducted as part of further intrusive
ground investigations.
Reservoir Flooding
7.10
The EA’s reservoir flood mapping indicates that there are no reservoirs within
the vicinity of the site. Therefore, the site is considered to be at low risk from
reservoir flooding.
Surface Water Flooding/Overland Flows (Pluvial)
7.11
Surface water flooding is caused by rainfall levels exceeding the natural
infiltration properties of the surrounding soils. It occurs where there is a lack of a
formalised drainage system, as a result of poorly designed or maintained sewer
systems or due to no natural method of drainage such as watercourses, ditches, or
where soil infiltration rates are low. It often results in ponding of water at low points
or backing up behind obstructions.
7.12
The EA’s Surface Water Flood Maps indicates the potential for Surface
Water flooding at the north east corner of the site for the 1 in 30 year and 1 in 200
year storm events. It should be noted that the EA’s surface water mapping is based
on a very coarse level of modelling and only provides a general indication on broad
areas that may be at risk from surface water modelling. Furthermore the surface
water flood modelling does not account for existing drainage systems nor sewer
networks. A copy of the EA’s surface water flooding maps for the 30yr and 100yr
events can be found in Appendix C.
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7.13
A detailed review of level information provided by the topographic survey
(Appendix B) indicates a low point within the Anstey Road, on the opposite side of
the existing entrance to the site. There is a road gully at this low point to
accommodate surface water run-off from the highway. As such the north eastern
part of the site will not be susceptible to surface water flooding from the adjacent
public highway.
7.14
The proposed on-site surface water drainage strategy will be designed to
accommodate surface water run-off, from within the site, for storm events of up to
and including 1 in 100 year plus 30% climate change thereby mitigating the future
risk of surface water flooding at localised area in the north eastern part of the site.
7.15
Overland flood routes can be accommodated within the masterplan layout to
direct any possible overland flood flows that occur from outside the development,
and within the development, away from the proposed housing within the site.
Sewer Infrastructure Flooding
7.16
Flooding can occur due to the failure of existing foul or surface water
drainage infrastructure. If flows within the drainage system exceed the designed
capacity or foreign matter causes blockages, overflow to the surface can occur
leading to flooding.
7.17
EHDC’s SFRA mapping and the associated table indicate that no sewer flood
events have been recorded within the vicinity of the site. EHDC’s SFRA mapping
are presented as Appendix D.
(19)
13-193-01
December 2013
________________________________________________________________________
8.0
FLOOD RISK MITIGATION MEASURES
Mitigation against Flood Risk from the Proposed Development
8.1
To mitigate against the risk from localised overland flooding from the
proposed development, a SuDS management train will provide surface water source
control, treatment and attenuation in the form of permeable paving and soakaways.
8.2
As the development will alter the drainage regime of the site by increasing
the impermeable surface area and therefore increasing the rate, volume and
potential contamination of surface run-off, it is necessary to provide mitigation
measures to offset the potential impacts. Therefore, surface water run-off will be
managed using a number of different methods across the site. All roads, driveways
and parking areas across the site will be formed of permeable paving which will
infiltrate to the ground. Surface water run-off from roof areas will infiltrate to the
ground through soakaways, where there is sufficient clearance from foundations.
Surface water run-off from roof areas of properties with unsuitable garden space for
soakaways (i.e. 5m from building foundations) will be conveyed to the permeable
paving across the site. Utilising permeable paving and soakaways will help cleanse
any surface water of heavy metals, hydrocarbons, rubber dust, silts and other
detritus by settlement prior to entering into the ground.
8.3
The proposed on-site surface water gravity sewer will be designed to cater
for the 1 in 30 year storm. Attenuation systems will store surface water run-off onsite arising from flood events up to and including the 1 in 100 year plus 30% climate
change storm.
8.4
To deal with the residual risk of blockage to all on-site drainage features, the
developer, lead local flood risk authority and SuDS Approving Body and/or adopting
Water Company will ensure maintenance of their respective drainage system in line
with the manufacturers’ recommendations by the production of a Maintenance
Management Plan. This will ensure that over the lifetime of the proposed
development the drainage system will be properly maintained to ensure continued
functionality.
(20)
13-193-01
December 2013
________________________________________________________________________
Mitigation against Flood Risk to the Development
Fluvial and Pluvial Flooding
8.5
Information provided by the EA indicates that the proposed development
should not be at risk of fluvial flooding from the 1 in 100 year storm event.
8.6
To mitigate surface water flow, a formalised surface water drainage system
will be installed. The drainage system will be designed with attenuation at source
before infiltration to the ground beneath the site. The surface water drainage system
will be designed to accommodate storm water run-off from the 1 in 100 year event
plus 30% climate change.
8.7
At the detailed design stage, further mitigation against the potential risk of
surface water flooding to the proposed development will be provided by the
manipulation of site levels to ensure that overland flows during extreme flood events
will be diverted away from buildings.
Contamination from Construction
8.8
The construction works must be undertaken in a manner to prevent pollution
to the River Wey and any groundwater which may lie beneath the site. Contractors
are to make reference to current legislation and EA guidelines in respect of
construction pollution prevention.
8.9
The contractor will be advised on the removal of any hotspots of
contaminated ground established through an intrusive soil investigation or during
excavation works.
8.10
All stocks of materials, oils and fuels are to be stored in a manor preventing
spillage and seepage to ground. Wastewater will not be freely discharged to the
ground or watercourses. All hydrocarbons and chemical spillages will be thoroughly
cleaned by excavation of the polluted ground and disposed of to a licensed waste
depot.
(21)
13-193-01
December 2013
________________________________________________________________________
8.11
The list of guidelines below are initial recommendations and not exhaustive.
It will be the responsibility of the contractor to ensure they obtain and understand
the latest legislation and guidelines:

The Groundwater Directive 80/68/EEC. Office Journal of the European
Communities 1980.

Protection of Groundwater Against Pollution and Deterioration. Office
Journal of the European Union 2006.

Environmental Permitting (England and Wales) Regulations. Draft
Statutory Instruments 2010.

Waste Management – The Duty of Care: A Code of Practice. The
Stationary Office 1996.

Control of Water Pollution from Construction Sites: Guidance for
Consultants and Contractors. CIRIA Report 532. 2001.

Waste Minimisation and Recycling in Construction – A Site Handbook.
CIRIA 1999.

Managing Materials and Components on Site. CIRIA 1998.

Safe Storage and Disposal of Used Oils: PPG8 Environmental Alliance
2004.

Underground, Under Threat. The State of Groundwater in England and
Wales. Environment Agency 2006.

Groundwater
Protection:
Policy
Environment Agency 2006.
(22)
and
Practice
Document
GP3.
13-193-01
December 2013
________________________________________________________________________
9.0
APPRAISAL OF RESIDUAL FLOOD RISK
9.1
When undertaking a FRA it is essential to put into perspective any theoretical
analysis with the reality of the physical system in place. It is impossible (both
practically and economically) to design a system which will never fail. However,
good design, controlled construction and regular maintenance can reduce the
likelihood of failure during its design life.
9.2
The Flood Mechanism has shown that the site offers low risk to users of the
proposed residential development based on the following:

The proposed development will utilise SuDS techniques where possible
to provide treatment and attenuation of surface water run-off, up to and
including run-off arising from the 1 in 100 year plus 30% climate change
storm.

There are no historic flood events of any flood form recorded within the
site.

The proposals for a residential development in Flood Zone 1 are deemed
appropriate as per the recommendations of the NPPF.

The foul drainage system will be designed in accordance with best
practice and connect to the public sewer system.

The site is shown to be at low risk from groundwater flooding and surface
water flooding according to mapping published in EHDC’s SFRA.
9.3
All flood advice given is based on literature, mapping and historic records
produced by the EA, EHDC and HCC.
Contact has been made with the EA
requesting pre-application advice on this scheme. This correspondence is presented
as Appendix G.
(23)
13-193-01
December 2013
________________________________________________________________________
10.0
SURFACE WATER DRAINAGE STRATEGY
Sustainable Drainage Systems
10.1
The NPPF and EA guidance requires developments to employ SuDS
techniques where feasible in the management of site run-off and surface water
drainage on all new developments. Careful design of SuDS features can ensure that
the proposed surface water regime closely reflects the natural hydrology and
hydrogeology of the site. A copy of the Preliminary Surface Water Drainage Strategy
drawing 13-193-001 is provided in Appendix H.
10.2
The key benefits of the proposed SuDS on site are as follows:

Improving water quality over a conventional piped system by allowing the
settlement of pollutants.

Improving amenity through the provision of open green space and wildlife
habitat.

Enabling a natural drainage system which maintains the existing surface
water flow regime.
10.3
Source Control is a key element of SuDS and is now identified in Part H of the
Building Regulations 2002 as taking preference over conventional drainage systems.
Part H now states:
“Rainwater from a system provided pursuant to sub-paragraphs (1) or (2)
shall discharge to one of the following, listed in order of priority:
(a)
an adequate soakaway or some other adequate infiltration system;
or where that is not reasonably practicable,
(b)
a watercourse; or where that is not reasonably practicable,
(c)
a sewer.”
(24)
13-193-01
December 2013
________________________________________________________________________
10.4
Source control systems treat water close to the point of collection, in features
such as soakaways, permeable pavements and dry swales.
As source control
measures generally rely upon the infiltration of surface water to the ground, it is a
prerequisite that the ground conditions are appropriate. BGS mapping advises the
site is underlain by the Zig Zag Chalk Formation which is predominantly Chalk.
10.5
The soakage potential of this strata is acceptable according to intrusive ground
investigations, extracts of which are presented as Appendix F. The average
infiltration rate across this site has been taken as 1.4x10-5m/s for the purpose of the
initial design of the permeable pavement and soakaways.
10.6
SuDS enable surface water run-off to mimic the natural surface water regime
throughout the site. Surface water run-off will be managed using multiple techniques
across the site.

The internal roads, drives and parking bays will be drained using permeable
paving with full infiltration to the sub-strata;

The roof drainage from the apartments will be conveyed to a cellular crate
soakaway located in the car parking courts;

Surface water run-off from the individual houses will be conveyed to a ring
soakaway to be located in the rear garden of each plot, subject to a minimum
5m clearance from any proposed/existing foundations and public roads.
10.7
The FWMA has amended Section 106 of the Water Industry Act to remove the
automatic right to connect surface water without prior consideration to SuDS.
10.8
SuDS will attenuate and treat surface water run-off at source (source control) in
line with the NPPF with its associated documents and the EA’s policies.
10.9
As part of the requirement of the Code for Sustainable Homes, SuDS will also
benefit the assessment of residential homes in the Code for Sustainable Homes rating
criteria.
(25)
13-193-01
December 2013
________________________________________________________________________
Proposed Surface Water Discharge
10.10 The current drainage strategy seeks to discharge all surface water run-off on
site via infiltration techniques up to and including the 1 in 100 year plus 30% climate
change.
Proposed Design Criteria
10.11 Any design and assessment of the requirements for storm drainage will be
based on the following criteria:
Return Period
1 in 30
Flood Protection
1 in 100 year
Sensitivity Check
Climate Change to 30%
M5-60
20mm
Ratio R
0.35
Minimum Cover to Adoptable Pipes
1.2m
Minimum Velocity (Full Bore)
1m / Sec
Pipe Ks Value
0.6mm
10.12 Based upon the planning layout for the proposed development the impervious
surfacing consists of proposed roofs, roads, driveways and parking areas. The total
impermeable area has been estimated as approximately 1.1ha.
10.13 Micro Drainage calculations have been prepared for the proposed catchment to
determine the total volume of storage and extent of permeable paving required on site
to accommodate the 100 year event plus 30% climate change in accordance with the
requirements of the NPPF. MicroDrainage surface water storage calculations are
provided in Appendix I.
10.14 An assessment of the typical section of permeable pavement indicates a
require minimum depth of permeable sub base of 450mm assuming a carriageway
gradient of no greater than 1 in 90.
(26)
13-193-01
December 2013
________________________________________________________________________
10.15 The soakaways proposed to serve each individual house are proposed as
1200mm diameter ring soakaways with depths extending from 2.0m to 2.5m below
ground subject to the house type.
10.16 The run off from the roof of the apartment block is proposed to discharge to a
10m x 1.5m x 0.8m cellular crate soakaway assuming an invert level of 2.0m below
ground level.
(27)
13-193-01
December 2013
________________________________________________________________________
11.0
FOUL DRAINAGE STRATEGY
11.1
TWUL are the governing water authority for the area.
Any proposed
connections or changes to the existing discharge rates must be approved by TWUL
prior to commencement of any construction works.
11.2
Foul flows generated by these proposals will be conveyed through the
development via gravity drains to the existing sewer located in the south of the site.
The new foul network will be designed to TWUL standards. Any connection to the
public sewer will have to be agreed with TWUL.
11.3
The hydraulic design for the discharge rate for the foul wastewater design has
been calculated in accordance with Sewers for Adoption 7th Edition which states
design flow rates for dwellings should be 4000l/day. Therefore the discharge rate for
the proposed development of up to 85 units equates to a foul discharge rate of 3.94l/s.
Details of the indicative proposed foul water drainage layout can be found on drawing
13-193-001 in Appendix H.
(28)
13-193-01
December 2013
________________________________________________________________________
12.0
IMPACT ON OTHER LAND
12.1
The development proposals will seek to mimic the pre-development runoff
regime and will accommodate and discharge all surface water run-off within the site
via infiltration techniques for storm events up to and including the 1 in 100 year plus
30% climate change.
12.2
As the proposals utilise infiltration where possible and there is no record of the
site flooding, the development should not cause any adverse effects to the existing
off-site flood risk downstream or on adjacent land.
(29)
13-193-01
December 2013
________________________________________________________________________
13.0
CONCLUSIONS
13.1
Information provided by the EA indicates the site is located within
Flood Zone 1, at low risk of flooding.
13.2
The proposed surface water drainage strategy includes permeable paving and
soakaways which will attenuate flows prior to discharging to the ground.
13.3
Any on-site surface water sewers will be designed to accommodate flows from
the 1 in 30 year storm event, and all surface water attenuation systems will be
designed to accommodate the 1 in 100 year plus 30% climate change storm.
13.4
The development proposals pose no increase to off-site flood risk for flood
events up to and including the 1 in 100 year plus 30% climate change flood event.
13.5
The proposed foul water drainage scheme includes a network built to adoptable
standards across the site which will connect into the existing foul sewer crossing the
south of the site. The existing sewer crossing the site should not require diversionary
works as part of this development. TWUL approval will need to be obtained prior to
any new connections or alterations in drainage flows to the public sewers.
13.6
The proposed development will provide means to conveying overland flow
during extreme flood events away from buildings along the road network and new
gardens by way of level design.
13.7
The site satisfies the requirements of NPPF with regard to flood risk, surface
water run-off management and the Sequential Test.
(30)
FIGURE 1
Site Location Plan
Burgess Hill
SITE
Reproduced from Ordnance Survey with the permission
of the Controller of Her Majesty's Stationery Office, Crown
Copyright Reserved.
Odyssey
Markides
Tuscany House
White Hart Lane
Basingstoke
Hampshire
RG21 4AF
Job Title
ANSTEY ROAD,
ALTON
Client
1:25000 @A4
Drawn
Drawing Title
Telephone: 01256 331144
Fax: 01256 331134
e-mail: [email protected]
web: www.odysseymarkides.com
Site Location Plan
Date
Scale
Job No
MS
13-193
DEC 13
Checked
Figure No
TS
Designed
Approved
FIGURE 1
MS
BAC
Rev
-
APPENDIX A
Proposed Masterplan
APPENDIX B
Topographical Survey
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16-10-13
DESCRIPTION
DRAWING MOVE AND SCALED TO ORIGINAL DRAWING
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SITE VISION SURVEYS LIMITED
W
S
W
E
E
UTILITY
TOPOGRAPHICAL
MAPPING
T: 01788 575036 W: SVSLTD.NET
E
SHAW COLGATE LTD
SITE LOCATION:
E
E
W
E
E
W
E
CLIENT:
W
41
0.
SPORTS GROUND
ANSTEY ROAD
ALTON GU34 2RL
W
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d
E
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DRAWING TITLE:
E
W
E
FULL UTILITY
DISCLAIMER: The location of under ground services shown on this drawing has been determined using electro-magnetic (and/or ground probing radar, where requested) techniques and visual observations. the limitations of this drawing
should be realised and no guarantee can be given that all services have been identified. This drawing may not include the location of all public services that may cross the site and therefore the relevant service drawings should be
obtained from the appropriate utility company and used in conjunction with this drawing. Additional services, structures or other below ground obstructions not indicated on this drawing may be present on site. reference should be
made to historical plans and as built drawings. Excavations in the vicinity of services should be carried out with due diligence ref: HSG47 document "avoiding dangers from underground services". Location accuracy is determined by
refering to manufacturers guidelines for the systems deployed. Reference should be made to the latest version of SVS Ltd site procedures document for utility location surveys.
SURVEYED BY:
DF - JRB
DRAWN BY:
DRAWING NO:
EB
1:200 @A1
pc
SURVEY DATE:
1013-SCL-7008
SCALE:
APPROVED BY:
07-10-13
SHEET NO:
1 OF 3
REV:
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IL
LP
MH
MKR
MTR
MW
OH
BT
E
BT BT
E
E
W
W
W
E
E
W
BT BT
E
0
E
BT BT
E
E
E
E
E
G
W
W
BT
E
E
E
OS
A
BT
E
BT
W
AS
E
BT
W
E
d
43
0.
NO
TR
BT
E
E
GA E
S
G
AS
W
BT
E
E
E
EOT
BT
A/
R
E
E
E
E
E
BT
BT
E
AS
G
EOT
BT
E
BT
d
0.
74
SA
BT
E
O
PE
E
E
E
REV
DATE
1
16-10-13
DESCRIPTION
E
E
E
0.
33
d
E
SURVEYS
E
E
S
UTILITY
TOPOGRAPHICAL
MAPPING
T: 01788 575036 W: SVSLTD.NET
E
E
CLIENT:
SHAW COLGATE LTD
E
E
E
SITE LOCATION:
SPORTS GROUND
ANSTEY ROAD
ALTON GU34 2RL
E
PE WATER
NO TRACE
E
E
E
O
0
O SA
SA
SA
d
O
E
E
E
E
BT
d
SA
01
1.
TOPOGRAPHICAL NOTES
E
O
BT
W
W
SA
O
SA
E
O
E
W
AS
G
SA
O
E
BT
4
.6
BT
E
0.
90
d
BT
d
46
0.
W
G
45
AS
0
W
BT
E
G
AS
BT
E
W
BT
E
30
G
0
AS
BT
W
E
BT
E
E
AS
G
BT
BT
W
E
E
G
AS
BT
E
AS
BT
GA
S
AC
BT
W
A/
R
E
BT
E
W
GA
S
BT
W
AS
G
E
E
G
AS
G
E
E
SV
SV
FH
BT
GA
S
E
E
GA
S
G
MH
CL 105.64
IL 103.21
BT
E
G
AS
W
45
0
BT
E BT
AS
G
AS
UTILITY NOTES
BT
E
OFF SURVEY AREA
PIPE RISER
POST & RAIL FENCE
RETAINING WALL
RODDING EYE
ROAD SIGN
RAIN WATER PIPE
SOAK AWAY
SAPLING
SOUND CONNECTED
SECURITY FENCE
SPOT LIGHT
SOIL PIPE
STOP TAP
STOP VALVE
SOIL VENT PIPE
TAKEN FROM RECORDS
THRESHOLD LEVEL
TRAFFIC LIGHT
TELEGRAPH POLE
UNABLE TO LOCATE
UNABLE TO RAISE
UNABLE TO SURVEY
UNABLE TO TRACE
VAPOUR RECOVERY
VENT PIPE
WATER METER
WASTE PIPE
UNDERSIDE
DIAMETER
S
G
E
OSA
OSBM
PR
P&R FENCE
RET WALL
RE
RS
RWP
S/A
SAP
S/C
SEC FENCE
SL
SP
ST
STN
SV
SVP
TBM
TFR
THL
TL
TP
UTL
UTR
UTS
UTT
VR
VP
WM
WFC
WP
U/S
GA
W
W
E
W
0
O .45d
SA
BT
W
W
E
E
E
G
G
AS
BT
GA
S
X2
X2
GV
ASSUMED ROUTE
BOLLARD
ILLUMINOUS BOLLARD
BOREHOLE
CONTROL BOX
CLOSEBOARD FENCE
CABLE RISER
CABLE TV
CATCHPIT
CONCRETE
COVER LEVEL
DEPTH / DEEP
DRAINAGE CHANNEL
DOWN PIPE
ELECTRICITY COVER
EARTH ROD
ELECTRICITY POLE
END OF TRACE
FLOWER BED
FIRE HYDRANT
FIRE SWITCH
GAS VALVE
GULLY
GULLY RUN
HEIGHT
INSPECTION COVER
INVERT LEVEL
LAMP POST
MANHOLE
MARKER
METER
MONITORING WELL
OVERHEAD
E
AS
S
BT
E
BT
GA
X2
E
T
PUMP ISLAND
E
BT
W
S
GA
BT
*
E
BT
W
E
W
d
BT
E
W
22
BT
SA
E
F=Foam
P=Product
Trial Pit Location
C=Concrete
Borehole / SVS
BT
O
BT T
B
T
FO
U
E
E
BT
BT
T
W
E
W
5
G
AS
0
45
W
E
W
E
BT T
B
W
0
30
BT
AS
BT
E
AS
G
T
FO
U
W
AS
G
A
d
W
0
G
1d
.7
79
0.
TSCAR
30
AS
OS
E
42
BT
STANTION
SV
BT
V
F
VR
E
E
0.
BTE
W
G
AS
V
F
W
BT
E
BT
A
O
PIPE
W
AS
G
BT
BT
W
AS
BT
W
R
AS
G
BT
A
O
E
CA
G
d
BT
W
E
TS
E
85
0.
BT
E
W
AS
G
W
AS
W
W
W
AS
G
G
BT
E
HV
CATV
CCTV
0
45
MH
CL 105.49
IL 102.79
E
HV
W
AS
AS
G
AS
BT
E
5
0
G
BT
W
G
Foul Drainage
Surface Drainage
Combined Drainage
Electricity
Gas
Water
Cable Television
Communication
British Telecom
Compressed Air
Offset Fill-Line
Oil Pipe
Pipe
Ventilation
Fuel Line
Vapour Recovery
Gauge Line
Telemetry
Fibre Optics
Unknown
Historical by Layer
End Of Trace
GAS
0.
22
15
BT
W
MH
CL 105.50
IL 103.30
E
A
BT
W
G
OS
d
E
G
0.
AS
MH
CL 105.58
IL 102.95
BT
BT
E
22
5
AS
d
83
80
0.
E
E
W
G
OS
A
BT
LEGEND
W
AS
E
BT
E
W
AS
E
d
40
0.
BT
W
W
W
AS
G
MH
CL 105.48
IL 102.96
3
E
45
0
G
E
DRAWING TITLE:
FULL UTILITY
E
SURVEYED BY:
DF - JRB
DRAWN BY:
DRAWING NO:
EB
1:200 @A1
pc
SURVEY DATE:
1013-SCL-7008
SCALE:
APPROVED BY:
07-10-13
SHEET NO:
2 OF 3
REV:
E
E
E
SHEET LAYOUT
1
3
E
E
E
2
LEGEND
E
Foul Drainage
Surface Drainage
Combined Drainage
Electricity
Gas
Water
Cable Television
Communication
British Telecom
Compressed Air
Offset Fill-Line
Oil Pipe
Pipe
Ventilation
Fuel Line
Vapour Recovery
Gauge Line
Telemetry
Fibre Optics
Unknown
Historical by Layer
End Of Trace
E
E
HV
E
HV
GAS
E
W
W
CATV
CCTV
BT
A
O
BT
A
O
PIPE
E
V
F
V
F
E
VR
T
T
FO
U
E
T
FO
U
F=Foam
P=Product
Trial Pit Location
C=Concrete
E
Borehole / SVS
T
PUMP ISLAND
0.
47
d
E
STANTION
*
E
E
E
E
E
LEGEND
E
E
E
E
A/R
E
E
A/R
BOLL
ILLU BOLL
BH
BTIC
C/BOX
C/B FENCE
CR
CTV
CP
CONC
CL
D
D/CHAN
DP
EIC
ER
EP
EOT
F/BED
FH
FS
GV
G
G-RUN
HT
IC
IL
LP
MH
MKR
MTR
MW
OH
ASSUMED ROUTE
BOLLARD
ILLUMINOUS BOLLARD
BOREHOLE
CONTROL BOX
CLOSEBOARD FENCE
CABLE RISER
CABLE TV
CATCHPIT
CONCRETE
COVER LEVEL
DEPTH / DEEP
DRAINAGE CHANNEL
DOWN PIPE
ELECTRICITY COVER
EARTH ROD
ELECTRICITY POLE
END OF TRACE
FLOWER BED
FIRE HYDRANT
FIRE SWITCH
GAS VALVE
GULLY
GULLY RUN
HEIGHT
INSPECTION COVER
INVERT LEVEL
LAMP POST
MANHOLE
MARKER
METER
MONITORING WELL
OVERHEAD
OSA
OSBM
PR
P&R FENCE
RET WALL
RE
RS
RWP
S/A
SAP
S/C
SEC FENCE
SL
SP
ST
STN
SV
SVP
TBM
TFR
THL
TL
TP
UTL
UTR
UTS
UTT
VR
VP
WM
WFC
WP
U/S
OFF SURVEY AREA
PIPE RISER
POST & RAIL FENCE
RETAINING WALL
RODDING EYE
ROAD SIGN
RAIN WATER PIPE
SOAK AWAY
SAPLING
SOUND CONNECTED
SECURITY FENCE
SPOT LIGHT
SOIL PIPE
STOP TAP
STOP VALVE
SOIL VENT PIPE
TAKEN FROM RECORDS
THRESHOLD LEVEL
TRAFFIC LIGHT
TELEGRAPH POLE
UNABLE TO LOCATE
UNABLE TO RAISE
UNABLE TO SURVEY
UNABLE TO TRACE
VAPOUR RECOVERY
VENT PIPE
WATER METER
WASTE PIPE
UNDERSIDE
DIAMETER
E
E
E
R
A/
E
E
UTILITY NOTES
E
E
EOT
E
E
E
E
E
d
31 E
0.
E
E
E
E
E
E
E
d
E
36
0.
E
E
E
E
E
E
TOPOGRAPHICAL NOTES
E
E
E
E
E
E
E
E
E
0.
E
56
d
d
E
39
0.
E
REV
DATE
1
16-10-13
DESCRIPTION
E
E
E
E
E
E
E
E
0.50
d
E
PE WATER
NO TRACE
E
T
EO
E
SURVEYS
E
S
E
E
UTILITY
TOPOGRAPHICAL
MAPPING
T: 01788 575036 W: SVSLTD.NET
CLIENT:
E
SHAW COLGATE LTD
E
5d
E
2
0.
EOT
NO ACCESS
E
E
E
E
E
SITE LOCATION:
SPORTS GROUND
ANSTEY ROAD
ALTON GU34 2RL
E
EOT
A/R
E
E
E
E
E
NO TRACE ON PE WATER
NO MANHOLES FOUND IN AREA
DRAWING TITLE:
FULL UTILITY
SURVEYED BY:
DF - JRB
DRAWN BY:
DRAWING NO:
EB
1:200 @A1
pc
SURVEY DATE:
1013-SCL-7008
SCALE:
APPROVED BY:
07-10-13
SHEET NO:
3 OF 3
REV:
APPENDIX C
Groundwater and Flood Mapping – Environment Agency
Site Geology
´
NEW PIT CHALK FORMATION
HOLYWELL NODULAR CHALK FORMATION
WEST MELBURY MARLY CHALK FORMATION
_
^
RIVER TERRACE DEPOSITS, 2
ZIG ZAG CHALK FORMATION
ALLUVIUM
HEAD
© British Geological Survey © Crown Copyright. All rights reserved. Environment Agency. 100026380, 2012
0
75
150
300
450
Meters
600
Flood Map centred on GU34 2RL - created on 14 October 2013 (WT/11595)
Scale 1:10,001
Legend
Flood Map Areas (assuming no defences)
Flood Zone 3 shows the area that could be
affected by flooding:
- from the sea with a 1 in 200 or greater
chance of happening each year
- or from a river with a 1 in 100 or greater
chance of happening each year.
Flood Zone 2 shows the extent of an extreme
flood from rivers or the sea with up to a 1 in
1000 chance of occurring each year.
© Environment Agency copyright and / or database rights 2013. All rights reserved. © Crown Copyright and database right 2013. Ordnance
Survey licence number 100024198.
Contact Us: National Customer Contact Centre, PO Box 544, Rotherham, S60 1BY. Tel: 03708 506 506 (Mon-Fri 8-6). Email: [email protected]
Flood Map for Surface Water 1 in 30 Chance
Note - this map provides a general
indication of the broad areas that may be
at risk of surface water flooding. It is taken
from a national assessment which takes
broad account of drainage and typical
storms which are likely to cause flooding,
but these will vary locally and are
therefore not appropriate everywhere.
Important
This information may be useful to
help inform emergency & spatial
planning and general awareness of
surface water flood risk.
It is not suitable for use at an
individual property scale due to the
method used.
The information should not be
interpreted as stating that the location
you are interested in will or won't
actually flood, but simply that it is in or
not in an area shown at risk on the
maps.
As there are various sources of surface
water information available, you should
contact your local authority to ask them
what surface water information best
represents local conditions.
Flood depths from rainfall
with a 1 in 30 chance
of occuring in any given
year
> 0.1m
> 0.3m
1:10,000
Data produced 2010.
This map is reproduced from Ordnance Survey material with the permission of Ordnance Survey on behalf of the Controller of Her Majesty's Stationery Office © Crown copyright.
Unauthorised reproduction infringes Crown copyright and may lead to prosecution or civil proceedings. Environment Agency, 100026380, (2010).
Use subject to the terms and conditions of the copyright statement and disclaimer.
Flood Map for Surface Water - 1 in 200 Chance
Note - this map provides a general
indication of the broad areas that may be
at risk of surface water flooding. It is taken
from a national assessment which takes
broad account of drainage and typical
storms which are likely to cause flooding,
but these will vary locally and are
therefore not appropriate everywhere.
Important
This information may be useful to
help inform emergency & spatial
planning and general awareness of
surface water flood risk.
It is not suitable for use at an
individual property scale due to the
method used.
The information should not be
interpreted as stating that the location
you are interested in will or won't
actually flood, but simply that it is in or
not in an area shown at risk on the
maps.
As there are various sources of surface
water information available, you should
contact your local authority to ask them
what surface water information best
represents local conditions.
Flood depths from rainfall
with a 1 in 200 chance
of occuring in any given
year
> 0.1m
> 0.3m
1:10,000
Data produced 2010.
This map is reproduced from Ordnance Survey material with the permission of Ordnance Survey on behalf of the Controller of Her Majesty's Stationery Office © Crown copyright.
Unauthorised reproduction infringes Crown copyright and may lead to prosecution or civil proceedings. Environment Agency, 100026380, (2010).
Use subject to the terms and conditions of the copyright statement and disclaimer.
APPENDIX D
Strategic Flood Risk Assessment Extracts – East Hampshire District Council
Extract of Tile A of the Flood Maps from the East Hampshire District Council
Strategic Flood Risk Assessment
APPENDIX E
Sewer Record Extracts – Thames Water Utilities Limited
=
!
22
5
0
30
=
40
43
%
4110
!=
5
37
4116
1
SE
O
113
%
7
89
22
5
5
3
% 00
CL
Y
0 E
30IPL 0
5
SH % 1
4114
%
!
4115
!
15%
0
50
%4
5103
=% !
!
6101
!
7
!
Cl
ub
22
5
=
!
!
FF
06
=
%
4107
%
4108
97
b
69
%
1m
5.
0
1
%
4109
79
5102
=
32
91
5101
5204
8
83 1
30=
0
AN
ST
EY
5202
%
93
RO
AD
!
22
a
97
10
5203
SU7240SE
60
0
%
Asset Location Search Sewer Map - ALS/ALS Standard/2013_2576589
45
=
0
EY
ST
N
A
Bowling
5104
Green
!
0
15
%
22
5
!=
5105
4117
LL
MI
E
OS
L
C
6102
Stand
%
0
45
5
22
!
m
91
0.
4101
!
%
5
22
4002
٨
٨
16
Eg
ga
r' s
٨
٨
11
٨
Jo
hn
٨
%
٨
5
22
٨
Sq
ua
re
to
٨
1
5
٨
7001
!
13
=
Sports Ground
4
10 2
% 5
3
0
30
4003
0
45
RH
Tennis
Court
%
105.7m
٨
0
30
٨
%
٨
٨
٨
5001
19
! EG
CL GA
O RS
SE
7
8
5
5
9
%
!
7901
%
30
0
0
10
6903
!
6905
!
1
!
The width
of the displayed area is 296m and the centre of the map is located at OS coordinates 472604,140083
?
Pl
Ar ay
ea
!
IN
DI
C
?
1
% 50
!
5902
I
AT
R
VE
OU
?
5903
!
5905
=
TE
?
!
5901
!
4902
E ! %
AN
7902AN L %
WM
7903
NE ! =
%
?
!
4
13
7904
18
20591C
!
5904
El Sub Sta
19
CL
O
SE
?
%
591B
!
S
0
30
?
AR
5
22
591A
!
17
Pavilion
?
EG
G
Brendon Care Home
Factory
14
%
2
4
12
26
6001
Works
16
The position of the apparatus shown on this plan is given without obligation and warranty, and the accuracy cannot be guaranteed. Service pipes are not sho wn but their presence should be anticipated. No liability of
any kind whatsoever is accepted by Thames Water for any error or omission. The actual position of mains and services must be verified and established on site before any works are undertaken.
Based on the Ordnance Survey Map with the Sanction of the controller of H.M. Stationery Office, License no. 100019345 Crown Copyright Reserved.
Page 7 of 10
NB. Levels quoted in metres Ordnance Newlyn Datum. The value -9999.00 indicates that no survey information is available
Manhole Reference
6903
7901
7902
7903
7904
6001
5903
61AG
61AF
61AE
6102
7001
4002
4106
4114
4107
4115
4108
4109
4116
4101
4110
4003
4117
5105
5104
5103
5203
5202
5204
5102
5101
6101
61AH
5902
5905
5901
5904
591C
591B
591A
5001
Manhole Cover Level
102.31
97.31
97.1
97.09
96.92
103.9
102.84
n/a
n/a
n/a
104.29
103.93
105.65
106.14
106.14
106.06
105.93
n/a
n/a
105.55
105.6
105.55
n/a
n/a
n/a
105.49
105.32
105.74
105.36
105.27
105.07
104.98
104.6
n/a
104.19
n/a
104.26
103.4
n/a
n/a
n/a
104.76
Manhole Invert Level
101.15
95.76
95.79
95.73
95.51
101.3
101.58
n/a
n/a
n/a
102.49
101.76
103.23
103.74
103.77
103.5
103.36
n/a
n/a
103.18
102.83
103.19
n/a
n/a
103.22
103.01
103.1
104.02
103.09
102.88
102.5
103.35
102.94
n/a
100.95
n/a
101
101.35
n/a
n/a
n/a
102.33
The p osition of the a pparatus shown on t his plan is gi ven without obliga tion a nd warranty, a nd the ac curacy c annot be gua ranteed. Ser vice pipe s are not
shown but their presence should be anticipated. No liability of any kind whatsoever is accepted by Thames Water for any error or omission. The actual position
of mains and services must be verified and established on site before any works are undertaken.
Page 8 of 10
ALS Sewer Map Key
Public Sewer Types (Operated & Maintained by Thames Water)
Foul: A sewer designed to convey waste water from domestic and
industrial sources to a treatment works.
Sewer Fittings
Other Symbols
A feature in a sewer that does not affect the flow in the pipe. Example: a vent
is a fitting as the function of a vent is to release excess gas.
Symbols used on maps which do not fall under other general categories
/
Public/Private Pumping Station
Air Valve
Change of characteristic indicator (C.O.C.I.)
Surface Water: A sewer designed to convey surface water (e.g. rain
water from roofs, yards and car parks) to rivers or watercourses.
Dam Chase
Invert Level
Combined: A sewer designed to convey both waste water and surface
water from domestic and industrial sources to a treatment works.
M
Fitting
Summit
Meter
Areas
Vent Column
Lines denoting areas of underground surveys, etc.
Trunk Surface Water
Storm Relief
Trunk Foul
Operational Controls
Agreement
A feature in a sewer that changes or diverts the flow in the sewer. Example:
A hydrobrake limits the flow passing downstream.
Operational Site
Trunk Combined
Control Valve
P
P
Bio-solids (Sludge)
Vent Pipe
Chamber
Drop Pipe
Tunnel
Ancillary
Proposed Thames Surface
Water Sewer
Proposed Thames Water
Foul Sewer
Gallery
Foul Rising Main
End Items
Combined Rising Main
End symbols appear at the start or end of a sewer pipe. Examples: an
Undefined End at the start of a sewer indicates that Thames Water has no
knowledge of the position of the sewer upstream of that symbol, Outfall on a
surface water sewer indicates that the pipe discharges into a stream or river.
Surface
Main
Water
Rising
Sludge Rising Main
Proposed Thames Water
Rising Main
Conduit Bridge
Weir
Other Sewer Types (Not Operated or Maintained by Thames Water)
3) Arrows (on gravity fed sewers) or flecks (on rising mains) indicate direction of
flow.
Gulley
Culverted Watercourse
Proposed
Abandoned Sewer
Notes:
2) All measurements on the plans are metric.
Combined Sewer
Undefined End
Inlet
1) All levels associated with the plans are to Ordnance Datum Newlyn.
Surface Water Sewer
Outfall
W
Vacuum
Foul Sewer
6) The text appearing alongside a sewer line indicates the internal diameter of
the pipe in milimetres. Text next to a manhole indicates the manhole
reference number and should not be taken as a measurement. If you are
unsure about any text or symbology present on the plan, please contact a
member of Property Insight on 0845 070 9148.
4) Most private pipes are not shown on our plans, as in the past, this information has
not been recorded.
5) ‘na’ or ‘0’ on a manhole level indicates that data is unavailable.
Page 9 of 10
APPENDIX F
Ground Investigation Extracts
HP1
HP2
HP3
Project:
Anstey Road Sports Ground
Title
Exploratory Hole Location Plan
Client:
BNP Paribas
Ref No:
GE9613
Revision: 0
28 Crescent Road, Brighton, BN2 3RP
Drawn:
GR
Date:
23/10/2013
T: 01273 699 399 F: 01273 699 388
Figure:
2
Scale:
Not To Scale
E: [email protected] W: www.gesl.net
Geo-Environmental Services Ltd
STRATA
SAMPLING & TESTING
STRATA DESCRIPTION
Legend
Brown slightly clayey fine sandy silt with regular fine to medium
sub-angular flint gravel and abundant roots (less than 1mm)
(TOPSOIL).
0.20
0.50
D(1)
D(2)
Brown slightly clayey silt with occasional medium to coarse
sub-angular flint gravel and occasional roots (less than 1mm) rare
charcoal and brick fragments (MADE GROUND).
mOD
mBGL
-0.10
0.10
Water
S/Pipe
(0.30)
0.40
-0.40
Light brown slightly clayey sandy well graded sub-angular flint
GRAVEL (RIVER TERRACE DEPOSITS)
(0.40)
SAMPLES: D=disturbed B=bulk U=undisturbed TESTS: MAC=macintosh IVAN=vane HPEN=penetrometer SPT=split-spoon CPT=cone WATER:
Stability:
Stable
Type:
Groundwater:
No Groundwater Encountered
Method:
Hand Excavated Trial Pit
Project:
Remarks:
Backfilled with arisings
=strike
=rest OTHERS: (2.00)=strata
Ref:
Client:
Start:
Filled:
Eng:
Drawn:
BNP Paribas
Position:
GE9613
Finish:
Plant:
0.80
-0.80
End of Trial Pit at 0.80 m
Ckd:
15/10/2013
15/10/2013
15/10/2013
AB
AB
AB
HP1
Scale: 1:25
Size:
Depth:
Level:
Figure:
Sheet:
.32m x .30m
0.80mBGL
0.000mOD
FIG
Sheet 1 of 1
STRATA
SAMPLING & TESTING
STRATA DESCRIPTION
Legend
mOD
mBGL
Brown slightly clayey fine sandy silt with regular medium to fine
(TOPSOIL).
0.20
S/Pipe
(0.30)
D(1)
0.30
-0.30
Brown slightly clayey sandy well graded sub-angular flint GRAVEL
(RIVER TERRACE DEPOSITS)
0.50
Water
D(2)
(0.46)
-0.76
Stability:
Stable
Type:
Groundwater:
Method:
Project:
Remarks:
Ref:
Client:
Start:
Filled:
Eng:
Drawn:
BNP Paribas
Position:
GE9613
Finish:
Plant:
=strike
0.76
Ckd:
15/10/2013
15/10/2013
15/10/2013
AB
AB
AB
HP2
Scale: 1:25
Size:
Depth:
Level:
Figure:
Sheet:
.40m x .33m
0.76mBGL
0.000mOD
FIG
Sheet 1 of 1
STRATA
SAMPLING & TESTING
STRATA DESCRIPTION
Legend
mOD
mBGL
Brown slightly clayey fine sandy silt with regular fine to medium
(TOPSOIL).
0.20
0.50
D(1)
D(2)
(0.23)
Project:
Remarks:
=strike
Ref:
Client:
Start:
Filled:
Eng:
Drawn:
BNP Paribas
Position:
GE9613
Finish:
Plant:
0.73
-0.73
Method:
0.50
-0.50
Groundwater:
0.20
(0.30)
Brown slightly clayey sandy well graded sub-angular flint GRAVEL
(RIVER TERRACE DEPOSITS)
Type:
S/Pipe
(0.20)
-0.20
Brown slightly clayey silt with occasional medium to coarse
sub-angular flint gravel and occasional roots (less than 1mm) rare
charcoal and brick fragments (MADE GROUND).
Stability:
Stable
Water
Ckd:
15/10/2013
15/10/2013
15/10/2013
AB
AB
AB
HP3
Scale: 1:25
Size:
Depth:
Level:
Figure:
Sheet:
.39m x .30m
0.73mBGL
0.000mOD
FIG
Sheet 1 of 1
28 Crescent Road, Brighton,
East Sussex, BN2 3RP
Tel : 01273 699 399
Fax : 01273 699 388
Soakaway Test Results (after BRE Digest 365)
Project Name : Antsey Raod Sports Ground
Client : BNP Paribas
Pit reference
Pit depth (m)
Pit width (m)
Pit length (m)
Depth to standing water (m)
Test 1
Time (min)
0.0
1.0
2.0
3.0
4.0
5.0
10.0
40.0
Job No. :
GE9613
Date :
15/10/2013
HP1
0.80
0.30
0.32
Test 2
Time (min)
0.0
1.0
2.0
3.0
4.0
5.0
12.0
18.0
41.0
93.0
Depth (m)
0.33
0.37
0.39
0.43
0.45
0.47
0.54
0.70
Test 3
Time (min)
Depth (m)
0.35
0.38
0.39
0.39
0.39
0.40
0.46
0.50
0.57
0.70
Depth (m)
0.00
0.10
0.20
Depth (m)
0.30
0.40
0.50
0.60
0.70
0.80
0.90
1.00
0
30
60
90
120
150
180
Time (mins)
Test 1
Max. depth (m)
Test 2
Test 3
0.80
0.80
0.80
0.47
0.45
0.57
0.68
4.00
19.00
36.00
0.45
0.46
0.58
0.69
12.00
45.00
90.00
0.80
0.20
0.40
0.60
Vp 75-25
ap 50
tp 75-25
0.02
0.3874
32.00
0.02
0.375
78.00
0.04
0.592
0.00
Soil infiltration rate (m/s)
3.0E-05
1.2E-05
#DIV/0!
1.09E+02
4.43E+01
#DIV/0!
Effective depth (m)
75% effective depth (m)
t75 (min)
t50 (min)
t25 (min)
Soil infiltration rate (mm/hr)
Tel : 01273 699 399
Fax : 01273 699 388
Pit reference
Pit depth (m)
Pit width (m)
Pit length (m)
Test 1
Time (min)
0.0
1.0
2.0
3.0
4.0
5.0
Job No. :
GE9613
Date :
15/10/2013
HP2
0.76
0.33
0.40
Test 2
Time (min)
0.0
1.0
2.0
3.0
4.0
5.0
8.0
9.0
Depth (m)
0.51
0.57
0.60
0.63
0.67
0.70
Test 3
Time (min)
Depth (m)
0.45
0.52
0.56
0.57
0.60
0.61
0.67
0.68
Depth (m)
0.00
0.10
0.20
Depth (m)
0.30
0.40
0.50
0.60
0.70
0.80
0.90
1.00
0
5
10
15
20
25
30
Time (mins)
Test 1
Test 2
Test 3
Max. depth (m)
0.76
0.76
Effective depth (m)
t75 (min)
t50 (min)
t25 (min)
0.25
0.57
0.64
0.70
1.00
4.00
5.00
0.31
0.53
0.61
0.68
1.50
5.00
9.00
Vp 75-25
ap 50
tp 75-25
0.02
0.3145
4.00
0.02
0.3583
7.50
2.2E-04
1.3E-04
#DIV/0!
7.87E+02
4.57E+02
#DIV/0!
0.76
0.19
0.38
0.57
0.05
0.132
0.00
Tel : 01273 699 399
Fax : 01273 699 388
Pit reference
Pit depth (m)
Pit width (m)
Pit length (m)
Test 1
Time (min)
0.0
1.0
2.0
3.0
4.0
5.0
10.0
23.0
37.0
Job No. :
GE9613
Date :
15/10/2013
HP3
0.73
0.30
0.32
Test 2
Time (min)
0.0
1.0
2.0
3.0
4.0
5.0
10.0
21.0
26.0
28.0
38.0
47.0
Depth (m)
0.34
0.38
0.42
0.45
0.47
0.47
0.54
0.60
0.65
Test 3
Time (min)
Depth (m)
0.28
0.31
0.33
0.35
0.37
0.38
0.45
0.55
0.56
0.57
0.60
0.62
Depth (m)
0.00
0.10
0.20
Depth (m)
0.30
0.40
0.50
0.60
0.70
0.80
0.90
1.00
0
10
20
30
40
50
60
Time (mins)
Test 1
Max. depth (m)
Test 2
Test 3
0.73
0.73
0.73
0.39
0.44
0.54
0.63
2.50
10.00
30.00
0.45
0.39
0.51
0.62
4.00
17.00
47.00
0.73
0.18
0.37
0.55
Vp 75-25
ap 50
tp 75-25
0.02
0.3378
27.50
0.02
0.375
43.00
0.04
0.5486
0.00
3.4E-05
2.2E-05
#DIV/0!
1.21E+02
8.04E+01
#DIV/0!
Effective depth (m)
t75 (min)
t50 (min)
t25 (min)
APPENDIX G
Environment Agency Correspondence
Ms Stephanie Wood
Odyssey Consulting Engineers Ltd
Tuscany House White Hart Lane
BASINGSTOKE
Hampshire
RG21 4AF
Our ref:
Your ref:
HA/2013/114785/01-L01
13-193
Date:
24 September 2013
Dear Ms Wood,
PRE-APP ENQUIRY FOR 110-120 RESIDENTIAL UNITS PROPOSED FOR SITE
WHICH IS CURRENTLY GREENFIELD LAND.
MOLSON COORS SPORTS GROUND, ANSTEY ROAD, ALTON
Thank you for your pre-app enquiry on the above development proposal.
The proposed development site has a low environmental risk within the remit of the
Environment Agency.
Although the site falls within flood zone 1 with a low risk of flooding, the proposed
development exceeds 1HA and will need to be accompanied by a Flood Risk
Assessment (FRA). Surface water concerns should be addressed within the FRA. In all
cases, the first option for managing surface water should be according to sustainable
drainage system (SUDS) principles. Any FRA submitted will be expected to
demonstrate how SUDS principles have been taken into account in managing surface
water run-off.
For further information and guidance on the use of SuDS please see the flood risk
standing advice from the Environment Agency:
http://www.environment-agency.gov.uk/research/planning/93498.aspx
For further information on planning a new development please visit the link to our
‘developers guide’:
http://www.environment-agency.gov.uk/research/planning/147852.aspx
Due to the nature of the development and low environmental risk no detailed comments
will be provided at the application stage. The Local Authority will be able to provide
further guidance.
Yours sincerely,
Miss Julie Paine
Planning Advisor, Environment Agency
Direct dial 01903 703989
Direct e-mail [email protected]
Environment Agency
Guildbourne House Chatsworth Road, Worthing, West Sussex, BN11 1LD.
Customer services line: 03708 506 506
www.environment-agency.gov.uk
End
APPENDIX H
Preliminary Surface Water Drainage Strategy (Drawing no. 13-193-001)
APPENDIX I
Micro Drainage Surface Water Storage Calculations
Tuscany House
White Hart Lane
Basingstoke RG21 4AF
Date 20/12/2013 11:41
File Typical extent o...
Micro Drainage
Page 1
Anstey Road
Typical permeable paving
section
Designed by TS
Checked by
Source Control 2013.1.1
Summary of Results for 100 year Return Period (+30%)
Half Drain Time : 786 minutes.
Storm
Event
15
30
60
120
180
240
360
480
600
720
960
1440
2160
2880
4320
5760
7200
8640
10080
15
30
60
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
Max
Max
Max
Max
Level Depth Infiltration Volume
(m)
(m)
(l/s)
(m³)
Summer 60.411
Summer 60.483
Summer 60.556
Summer 60.626
Summer 60.661
Summer 60.680
Summer 60.705
Summer 60.715
Summer 60.718
Summer 60.720
Summer 60.720
Summer 60.709
Summer 60.682
Summer 60.655
Summer 60.605
Summer 60.562
Summer 60.526
Summer 60.496
Summer 60.470
Winter 60.438
Winter 60.517
Winter 60.599
Storm
Event
15
30
60
120
180
240
360
480
600
720
960
1440
2160
2880
4320
5760
7200
8640
10080
15
30
60
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
Status
0.411
0.3
11.4
0.483
0.3
15.7
0.556
0.4
20.2
0.626
0.4
24.5
0.661
0.4
26.7
0.680
0.4
27.9
0.705
0.4
29.3 Flood
0.715
0.4
29.9 Flood
0.718
0.4
30.1 Flood
0.720
0.4
30.2 Flood
0.720
0.4
30.1 Flood
0.709
0.4
29.5 Flood
0.682
0.4
28.0
0.655
0.4
26.3
0.605
0.4
23.2
0.562
0.4
20.6
0.526
0.3
18.4
0.496
0.3
16.5
0.470
0.3
14.9
0.438
0.3
13.0
0.517
0.3
17.8
0.599
0.4
22.9
Rain
Flooded Time-Peak
(mm/hr) Volume
(mins)
(m³)
Summer 122.433
Summer 82.239
Summer 52.662
Summer 32.503
Summer 24.118
Summer 19.386
Summer 14.268
Summer 11.460
Summer
9.659
Summer
8.396
Summer
6.724
Summer
4.907
Summer
3.573
Summer
2.849
Summer
2.067
Summer
1.644
Summer
1.377
Summer
1.193
Summer
1.056
Winter 122.433
Winter 82.239
Winter 52.662
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
19
34
64
122
182
242
360
480
536
594
720
982
1388
1792
2596
3392
4112
4920
5648
19
33
62
©1982-2013 Micro Drainage Ltd
O K
O K
O K
O K
O K
O K
Risk
Risk
Risk
Risk
Risk
Risk
O K
O K
O K
O K
O K
O K
O K
O K
O K
O K
Tuscany House
White Hart Lane
Date 20/12/2013 11:41
Micro Drainage
Page 2
Anstey Road
section
Designed by TS
Checked by
Max
Max
Max
Max
(m)
(m)
(l/s)
(m³)
Storm
Event
120
180
240
360
480
600
720
960
1440
2160
2880
4320
5760
7200
8640
10080
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
Winter 60.679
Winter 60.722
Winter 60.751
Winter 60.789
Winter 60.809
Winter 60.818
Winter 60.819
Winter 60.811
Winter 60.788
Winter 60.737
Winter 60.688
Winter 60.615
Winter 60.557
Winter 60.509
Winter 60.470
Winter 60.438
Storm
Event
120
180
240
360
480
600
720
960
1440
2160
2880
4320
5760
7200
8640
10080
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
Status
0.679
0.4
27.8
0.722
0.4
30.3 Flood
0.751
0.4
31.8 Flood
0.789
0.4
33.6 Flood
0.809
0.4
34.5 Flood
0.818
0.4
34.8 Flood
0.819
0.4
34.9 Flood
0.811
0.4
34.5 Flood
0.788
0.4
33.5 Flood
0.737
0.4
31.0 Flood
0.688
0.4
28.3
0.615
0.4
23.9
0.557
0.4
20.2
0.509
0.3
17.3
0.470
0.3
14.9
0.438
0.3
12.9
Rain
Flooded Time-Peak
(mm/hr) Volume
(mins)
(m³)
Winter
Winter
Winter
Winter
Winter
Winter
Winter
Winter
Winter
Winter
Winter
Winter
Winter
Winter
Winter
Winter
32.503
24.118
19.386
14.268
11.460
9.659
8.396
6.724
4.907
3.573
2.849
2.067
1.644
1.377
1.193
1.056
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
120
180
238
352
464
572
678
770
1068
1516
1932
2764
3568
4328
5104
5848
O K
Risk
Risk
Risk
Risk
Risk
Risk
Risk
Risk
Risk
O K
O K
O K
O K
O K
O K
Tuscany House
White Hart Lane
Date 20/12/2013 11:41
Micro Drainage
Page 3
Anstey Road
section
Designed by TS
Checked by
Rainfall Details
FSR
Winter Storms
Yes
Rainfall Model
Return Period (years)
100
Cv (Summer) 0.750
Region England and Wales
Cv (Winter) 0.840
M5-60 (mm)
20.000 Shortest Storm (mins)
15
Ratio R
0.350 Longest Storm (mins) 10080
Summer Storms
Yes
Climate Change %
+30
Time Area Diagram
Total Area (ha) 0.057
Time (mins) Area
From:
To:
(ha)
0
4 0.057
Tuscany House
White Hart Lane
Date 20/12/2013 11:41
Micro Drainage
Page 4
Anstey Road
section
Designed by TS
Checked by
Model Details
Storage is Online Cover Level (m) 61.000
Porous Car Park Structure
Width (m)
5.0
Infiltration Coefficient Base (m/hr) 0.05040
Membrane Percolation (mm/hr)
1000
Length (m) 60.0
Max Percolation (l/s)
83.3
Slope (1:X) 90.0
Safety Factor
10.0 Depression Storage (mm)
5
Porosity
0.30
Evaporation (mm/day)
3
Invert Level (m) 60.000
Cap Volume Depth (m) 0.450
Tuscany House
White Hart Lane
Date 20/12/2013 11:40
File Typical Cellular...
Micro Drainage
Page 1
Anstey Road
Typical soakaway
for apartments
Designed by TS
Checked by
15
30
60
120
180
240
360
480
600
720
960
1440
2160
2880
4320
5760
7200
8640
10080
15
30
60
Storm
Event
Max
Max
Max
Max
Status
(m)
(m)
(l/s)
(m³)
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
0.351
0.2
4.9
0.463
0.2
6.5
0.577
0.2
8.2
0.680
0.2
9.6
0.723
0.2
10.2
0.742
0.2
10.5
0.752
0.2
10.6
0.751
0.2
10.6
0.745
0.2
10.5
0.737
0.2
10.4
0.717
0.2
10.1
0.671
0.2
9.5
0.606
0.2
8.6
0.548
0.2
7.7
0.447
0.2
6.3
0.365
0.2
5.1
0.298
0.2
4.2
0.243
0.1
3.4
0.197
0.1
2.7
0.393
0.2
5.5
0.520
0.2
7.3
0.650
0.2
9.2
Rain
Flooded Time-Peak
(mm/hr) Volume
(mins)
(m³)
Summer 60.351
Summer 60.463
Summer 60.577
Summer 60.680
Summer 60.723
Summer 60.742
Summer 60.752
Summer 60.751
Summer 60.745
Summer 60.737
Summer 60.717
Summer 60.671
Summer 60.606
Summer 60.548
Summer 60.447
Summer 60.365
Summer 60.298
Summer 60.243
Summer 60.197
Winter 60.393
Winter 60.520
Winter 60.650
Storm
Event
15
30
60
120
180
240
360
480
600
720
960
1440
2160
2880
4320
5760
7200
8640
10080
15
30
60
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
Summer 122.433
Summer 82.239
Summer 52.662
Summer 32.503
Summer 24.118
Summer 19.386
Summer 14.268
Summer 11.460
Summer
9.659
Summer
8.396
Summer
6.724
Summer
4.907
Summer
3.573
Summer
2.849
Summer
2.067
Summer
1.644
Summer
1.377
Summer
1.193
Summer
1.056
Winter 122.433
Winter 82.239
Winter 52.662
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
19
33
64
122
182
240
344
398
462
524
662
938
1344
1756
2548
3288
4032
4752
5448
19
33
62
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
K
K
K
K
K
K
K
K
K
K
K
K
K
K
K
K
K
K
K
K
K
K
Tuscany House
White Hart Lane
Date 20/12/2013 11:40
Micro Drainage
Page 2
Anstey Road
Typical soakaway
for apartments
Designed by TS
Checked by
120
180
240
360
480
600
720
960
1440
2160
2880
4320
5760
7200
8640
10080
Storm
Event
Max
Max
Max
Max
Status
(m)
(m)
(l/s)
(m³)
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
0.768
0.2
10.9
1.026
0.2
11.6
1.384
0.2
12.0
1.694
0.2
12.3
1.667
0.2
12.3
1.524
0.2
12.1
1.384
0.2
12.0
0.984
0.2
11.6
0.752
0.2
10.6
0.656
0.2
9.3
0.571
0.2
8.1
0.430
0.2
6.1
0.320
0.2
4.5
0.234
0.1
3.3
0.166
0.1
2.3
0.113
0.1
1.5
Rain
Flooded Time-Peak
(mm/hr) Volume
(mins)
(m³)
Winter 60.768
Winter 61.026
Winter 61.384
Winter 61.694
Winter 61.667
Winter 61.524
Winter 61.384
Winter 60.984
Winter 60.752
Winter 60.656
Winter 60.571
Winter 60.430
Winter 60.320
Winter 60.234
Winter 60.166
Winter 60.113
Storm
Event
120
180
240
360
480
600
720
960
1440
2160
2880
4320
5760
7200
8640
10080
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
Winter
Winter
Winter
Winter
Winter
Winter
Winter
Winter
Winter
Winter
Winter
Winter
Winter
Winter
Winter
Winter
32.503
24.118
19.386
14.268
11.460
9.659
8.396
6.724
4.907
3.573
2.849
2.067
1.644
1.377
1.193
1.056
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
120
178
234
346
450
486
558
712
1012
1452
1872
2680
3456
4184
4928
5552
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
K
K
K
K
K
K
K
K
K
K
K
K
K
K
K
K
Tuscany House
White Hart Lane
Date 20/12/2013 11:40
Micro Drainage
Page 3
Anstey Road
Typical soakaway
for apartments
Designed by TS
Checked by
Rainfall Details
FSR
Winter Storms
Yes
Rainfall Model
100
Cv (Summer) 0.750
Cv (Winter) 0.840
M5-60 (mm)
15
Ratio R
Summer Storms
Yes
Climate Change %
+30
Time Area Diagram
Time (mins) Area
From:
To:
(ha)
0
4 0.022
Tuscany House
White Hart Lane
Date 20/12/2013 11:40
Micro Drainage
Page 4
Anstey Road
Typical soakaway
for apartments
Designed by TS
Checked by
Model Details
Trench Soakaway Structure
Trench Width (m)
1.5
Infiltration Coefficient Side (m/hr) 0.05040
Trench Length (m)
10.0
Safety Factor
2.0
Slope (1:X) 1000.0
Porosity
0.95
Invert Level (m) 60.000 Cap Infiltration Depth (m) 0.800
Tuscany House
White Hart Lane
Date 20/12/2013 11:38
File TYPICAL CELLULAR...
Micro Drainage
Page 1
Anstey Road
Typicalmanhole soakaway
for large houses
Designed by TS
Checked by
15
30
60
120
180
240
360
480
600
720
960
1440
2160
2880
4320
5760
7200
8640
10080
15
30
60
Storm
Event
Max
Max
Max
Max
Status
(m)
(m)
(l/s)
(m³)
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
0.351
0.2
4.9
0.463
0.2
6.5
0.577
0.2
8.2
0.680
0.2
9.6
0.723
0.2
10.2
0.742
0.2
10.5
0.752
0.2
10.6
0.751
0.2
10.6
0.745
0.2
10.5
0.737
0.2
10.4
0.717
0.2
10.1
0.671
0.2
9.5
0.606
0.2
8.6
0.548
0.2
7.7
0.447
0.2
6.3
0.365
0.2
5.1
0.298
0.2
4.2
0.243
0.1
3.4
0.197
0.1
2.7
0.393
0.2
5.5
0.520
0.2
7.3
0.650
0.2
9.2
Rain
Flooded Time-Peak
(mm/hr) Volume
(mins)
(m³)
Summer 60.351
Summer 60.463
Summer 60.577
Summer 60.680
Summer 60.723
Summer 60.742
Summer 60.752
Summer 60.751
Summer 60.745
Summer 60.737
Summer 60.717
Summer 60.671
Summer 60.606
Summer 60.548
Summer 60.447
Summer 60.365
Summer 60.298
Summer 60.243
Summer 60.197
Winter 60.393
Winter 60.520
Winter 60.650
Storm
Event
15
30
60
120
180
240
360
480
600
720
960
1440
2160
2880
4320
5760
7200
8640
10080
15
30
60
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
Summer 122.433
Summer 82.239
Summer 52.662
Summer 32.503
Summer 24.118
Summer 19.386
Summer 14.268
Summer 11.460
Summer
9.659
Summer
8.396
Summer
6.724
Summer
4.907
Summer
3.573
Summer
2.849
Summer
2.067
Summer
1.644
Summer
1.377
Summer
1.193
Summer
1.056
Winter 122.433
Winter 82.239
Winter 52.662
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
19
33
64
122
182
240
344
398
462
524
662
938
1344
1756
2548
3288
4032
4752
5448
19
33
62
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
K
K
K
K
K
K
K
K
K
K
K
K
K
K
K
K
K
K
K
K
K
K
Tuscany House
White Hart Lane
Date 20/12/2013 11:38
Micro Drainage
Page 2
Anstey Road
for large houses
Designed by TS
Checked by
120
180
240
360
480
600
720
960
1440
2160
2880
4320
5760
7200
8640
10080
Storm
Event
Max
Max
Max
Max
Status
(m)
(m)
(l/s)
(m³)
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
0.768
0.2
10.9
1.026
0.2
11.6
1.384
0.2
12.0
1.694
0.2
12.3
1.667
0.2
12.3
1.524
0.2
12.1
1.384
0.2
12.0
0.984
0.2
11.6
0.752
0.2
10.6
0.656
0.2
9.3
0.571
0.2
8.1
0.430
0.2
6.1
0.320
0.2
4.5
0.234
0.1
3.3
0.166
0.1
2.3
0.113
0.1
1.5
Rain
Flooded Time-Peak
(mm/hr) Volume
(mins)
(m³)
Winter 60.768
Winter 61.026
Winter 61.384
Winter 61.694
Winter 61.667
Winter 61.524
Winter 61.384
Winter 60.984
Winter 60.752
Winter 60.656
Winter 60.571
Winter 60.430
Winter 60.320
Winter 60.234
Winter 60.166
Winter 60.113
Storm
Event
120
180
240
360
480
600
720
960
1440
2160
2880
4320
5760
7200
8640
10080
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
Winter
Winter
Winter
Winter
Winter
Winter
Winter
Winter
Winter
Winter
Winter
Winter
Winter
Winter
Winter
Winter
32.503
24.118
19.386
14.268
11.460
9.659
8.396
6.724
4.907
3.573
2.849
2.067
1.644
1.377
1.193
1.056
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
120
178
234
346
450
486
558
712
1012
1452
1872
2680
3456
4184
4928
5552
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
K
K
K
K
K
K
K
K
K
K
K
K
K
K
K
K
Tuscany House
White Hart Lane
Date 20/12/2013 11:38
Micro Drainage
Page 3
Anstey Road
for large houses
Designed by TS
Checked by
Rainfall Details
FSR
Winter Storms
Yes
Rainfall Model
100
Cv (Summer) 0.750
Cv (Winter) 0.840
M5-60 (mm)
15
Ratio R
Summer Storms
Yes
Climate Change %
+30
Time Area Diagram
Time (mins) Area
From:
To:
(ha)
0
4 0.022
Tuscany House
White Hart Lane
Date 20/12/2013 11:38
Micro Drainage
Page 4
Anstey Road
for large houses
Designed by TS
Checked by
Model Details
Trench Soakaway Structure
Trench Width (m)
1.5
Trench Length (m)
10.0
Safety Factor
2.0
Slope (1:X) 1000.0
Porosity
0.95
Tuscany House
White Hart Lane
Date 20/12/2013 11:43
File Typical ring soa...
Micro Drainage
Page 1
Anstey Road
Typical manhole soakaway
for house
Designed by TS
Checked by
15
30
60
120
180
240
360
480
600
720
960
1440
2160
2880
4320
5760
7200
8640
10080
15
30
60
Storm
Event
Max
Max
Max
Max
Status
(m)
(m)
(l/s)
(m³)
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
0.756
0.1
1.3
0.998
0.1
1.8
1.231
0.1
2.2
1.415
0.1
2.5
1.470
0.1
2.6
1.482
0.1
2.6
1.491
0.1
2.6
1.482
0.1
2.6
1.462
0.1
2.6
1.436
0.1
2.5
1.375
0.1
2.4
1.252
0.1
2.2
1.097
0.1
1.9
0.971
0.1
1.7
0.777
0.1
1.4
0.634
0.1
1.1
0.526
0.0
0.9
0.439
0.0
0.8
0.370
0.0
0.7
0.849
0.1
1.5
1.121
0.1
2.0
1.387
0.1
2.4
Rain
Flooded Time-Peak
(mm/hr) Volume
(mins)
(m³)
Summer 60.756
Summer 60.998
Summer 61.231
Summer 61.415
Summer 61.470
Summer 61.482
Summer 61.491
Summer 61.482
Summer 61.462
Summer 61.436
Summer 61.375
Summer 61.252
Summer 61.097
Summer 60.971
Summer 60.777
Summer 60.634
Summer 60.526
Summer 60.439
Summer 60.370
Winter 60.849
Winter 61.121
Winter 61.387
Storm
Event
15
30
60
120
180
240
360
480
600
720
960
1440
2160
2880
4320
5760
7200
8640
10080
15
30
60
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
Summer 122.433
Summer 82.239
Summer 52.662
Summer 32.503
Summer 24.118
Summer 19.386
Summer 14.268
Summer 11.460
Summer
9.659
Summer
8.396
Summer
6.724
Summer
4.907
Summer
3.573
Summer
2.849
Summer
2.067
Summer
1.644
Summer
1.377
Summer
1.193
Summer
1.056
Winter 122.433
Winter 82.239
Winter 52.662
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
19
33
62
122
180
206
268
336
404
474
614
882
1280
1672
2420
3168
3896
4592
5344
18
33
62
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
K
K
K
K
K
K
K
K
K
K
K
K
K
K
K
K
K
K
K
K
K
K
Tuscany House
White Hart Lane
Date 20/12/2013 11:43
Micro Drainage
Page 2
Anstey Road
for house
Designed by TS
Checked by
Max
Max
Max
Max
(m)
(m)
(l/s)
(m³)
Storm
Event
120
180
240
360
480
600
720
960
1440
2160
2880
4320
5760
7200
8640
10080
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
Winter 61.687
Winter 61.827
Winter 61.864
Winter 61.860
Winter 61.827
Winter 61.764
Winter 61.686
Winter 61.513
Winter 61.330
Winter 61.111
Winter 60.942
Winter 60.697
Winter 60.527
Winter 60.404
Winter 60.311
Winter 60.237
Storm
Event
120
180
240
360
480
600
720
960
1440
2160
2880
4320
5760
7200
8640
10080
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
min
Status
1.687
0.1
2.8
1.827
0.1
3.0 Flood
1.864
0.1
3.0 Flood
1.860
0.1
3.0 Flood
1.827
0.1
3.0 Flood
1.764
0.1
2.9 Flood
1.686
0.1
2.8
1.513
0.1
2.7
1.330
0.1
2.3
1.111
0.1
2.0
0.942
0.1
1.7
0.697
0.1
1.2
0.527
0.0
0.9
0.404
0.0
0.7
0.311
0.0
0.5
0.237
0.0
0.4
Rain
Flooded Time-Peak
(mm/hr) Volume
(mins)
(m³)
Winter
Winter
Winter
Winter
Winter
Winter
Winter
Winter
Winter
Winter
Winter
Winter
Winter
Winter
Winter
Winter
32.503
24.118
19.386
14.268
11.460
9.659
8.396
6.724
4.907
3.573
2.849
2.067
1.644
1.377
1.193
1.056
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
118
174
228
288
364
440
514
656
940
1360
1756
2508
3280
4032
4752
5448
O K
Risk
Risk
Risk
Risk
Risk
O K
O K
O K
O K
O K
O K
O K
O K
O K
O K
Tuscany House
White Hart Lane
Date 20/12/2013 11:43
Micro Drainage
Page 3
Anstey Road
for house
Designed by TS
Checked by
Rainfall Details
FSR
Winter Storms
Yes
Rainfall Model
100
Cv (Summer) 0.750
Cv (Winter) 0.840
M5-60 (mm)
15
Ratio R
Summer Storms
Yes
Climate Change %
+30
Time Area Diagram
Time (mins) Area
From:
To:
(ha)
0
4 0.006
Tuscany House
White Hart Lane
Date 20/12/2013 11:43
Micro Drainage
Page 4
Anstey Road
for house
Designed by TS
Checked by
Model Details
Lined Soakaway Structure
Ring Diameter (m) 1.20
Pit Multiplier
1.5
Safety Factor
2.0
Number Required
1
Porosity
0.30

Flood Map for Surface Water

Transcription

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