9. hydrology and water resources -...

Nuthall Nottingham LLP Environmental Statement: Temple Park, Nuthall

April 2013 I gva.co.uk 123

9. Hydrology and Water Resources

Potential/Predicted Significant Environmental Effects

Site Preparation and Construction Phase

• Potential increase in physical contamination (i.e. sedimentation) to surface

water bodies and drainage features; and

• Increase in risk of surface water and drainage flooding on construction workers

and construction activities.

Operational Phase

• Potential increase in physical contamination (i.e. sedimentation) to surface

water bodies and drainage features;

• Increase in, or change in patterns of, surface water drainage and associated

flood risk on future populations and third parties; and

• Increase in foul drainage and associated demand on sewage treatment

works.

Introduction

9.1 This Chapter evaluates the likely effects of the Proposed Development on Drainage,

Flooding and Water Resources. In particular, it considers the potential effects on

surface water features and foul drainage systems and associated flood risk on-site, in

the vicinity of and downstream of the Site during the site preparation and

construction phase and the operational phase of the Proposed Development.

9.2 Where appropriate, mitigation measures to enhance, prevent, minimise or control the

effects are presented and residual effects, following the adoption of those measures,

are assessed.

9.3 Potentially significant effects to groundwater and degradation to surface water

quality due to chemical contamination are addressed within Chapter 13 – Ground

Conditions, Hydrogeology and Contamination.

9.4 This Chapter is supported by a Flood Risk Assessment (FRA) undertaken by WSP

(Planning Reference TP/OPA/DOC/10).



9.5 This Chapter (and its associated Figures and Appendices) is not intended to be read

as a stand alone assessment and reference should be made to the front end of this ES

(Chapters 1 – 5), as well as Chapter 18 Cumulative Effects and Interaction of Factors.

Methodology

Potential Effects

9.6 An EIA Scoping Report dated October 2012 was issued by GVA to Broxtowe Borough

Council (BBC). The following lists the relevant potential effects highlighted within the

EIA Scoping Report that are considered within this Chapter:


• Potential increase in physical contamination (i.e. sedimentation) to surface water

bodies and drainage features; and



Operational Phase


bodies and drainage features;

• Increase in, or change in patterns of, surface water drainage and associated

flood risk on future populations and third parties; and

• Increase in foul drainage and associated demand on sewage treatment works.

9.7 The following were scoped out within the EIA Scoping Report:

• Increase in potable water demand; and

• Risk of flooding from sources other than surface water runoff and drainage (i.e.

groundwater, fluvial and artificial sources).

Method of Baseline Data Collation

9.8 The scope of this Chapter includes a review of the available baseline information on

the Site setting with specific regards to current drainage and flooding conditions.



9.9 A Desk Study and Terrain Assessment has previously been prepared for the Site by

WSP (Appendix 13.1). This has been reviewed for information pertaining to the

environment setting and ground conditions.

9.10 A Flood Risk Assessment (FRA), including a conceptual drainage strategy completed

by WSP (Planning Reference TP/OPA/DOC/10) has been reviewed for information

pertaining to flooding at the Site.

Extent of the Study Area

9.11 The study area for drainage, flooding and water resources encompasses the Site and

receptors within the influence of the Site including off site surface water bodies and

drainage.

9.12 The study area for the Geoenvironmental Desk Study and Terrain Assessment

(Appendix 13.1) is up to 1km from the planning application boundary. A Site location

plan is presented as Figure 1.2 within Appendix 13.1.

Significance Criteria

Assessment

9.13 The assessment of potential effects as a result of the Proposed Development has

taken into account the site preparation and construction phase and the operational

phase. The significance level attributed to each effect has been assessed based on

the magnitude of change due to the Proposed Development and the sensitivity of

the affected receptor/receiving environment to change, as well as a number of other

factors that are outlined in more detail in Chapter 2 – Methodology. Magnitude of

change is assessed as negligible, minor, moderate or major and the sensitivity of the

affected receptor/receiving environment are assessed on a scale of high, medium,

low and negligible (as shown in Chapter 2 – Methodology).

Impact Significance

9.14 The following terms have been used to define the significance of the effects

identified:

• Major Effect: where the Proposed Development could be expected to have a

very significant effect (either positive or negative) on drainage, flooding and

associated sensitive receptors;



• Moderate Effect: where the Proposed Development could be expected to have a

noticeable effect (either positive or negative) on drainage, flooding and

associated sensitive receptors;

• Minor Effect: where the Proposed Development could be expected to result in a

small, barely noticeable effect (either positive or negative) on drainage, flooding

and associated sensitive receptors; and

• Negligible: where no discernible effect is expected as a result of the Proposed

Development on drainage, flooding and associated sensitive receptors.

Legislation / Policy Framework

Legislative Framework

9.15 The applicable legislative framework is summarised as follows:

• Environmental Protection Act (EPA) 1990 (Ref. 9.2) – Part IIA of the Environmental

Protection Act 1990 describes a regulatory role for Local Authorities in dealing with

contaminated land;

• Water Industry Act, 1991 (Ref. 9.3) – consolidates enactments relating to the supply

of water and the provision of sewerage services;

• The Water Resources Act 1991 (Ref. 9.4) – sets out the regulatory controls and

restrictions that provide protection to the water environment through controls on

abstraction, impounding and discharges as well as identifying water quality and

drought provisions;

• Land Drainage Act 1991 (Ref. 9.5) – consolidates enactments relating to internal

drainage boards and the functions of these boards and of local authorities in

relation to land drainage. Internal Drainage Boards (IDB) exercise a general

supervision over all matters relating to the drainage of land within their district and

they have powers to perform duties imposed on them within the Act;

• Land Drainage Act 1994 (Ref. 9.6) – adds new environmental duties to the Land

Drainage Act 1991. It places a duty on the IDB and local authorities to further the

conservation and enhancement of natural beauty and the conservation of flora,

fauna and geological or physiographical features of special interest; and to take

into account any effect which the proposals would have on the beauty or

amenity of any rural or urban area or on any such flora, fauna or features;



• The Environment Act 1995 (Ref. 9.7) – sets out the responsibilities of the Environment

Agency (EA) in relation to water pollution, resource management, flood defence

and fisheries;

• The Water Framework Directive (2000/60/EC) (WFD) (Ref. 9.8) – transposed into UK

law in 2003 (The Water Environment (Water Framework Directive) (England and

Wales) Regulations 2003), and is designed to improve and integrate the way

water bodies are managed throughout Europe. The WFD requires all inland and

coastal waters to reach "good” chemical and ecological status in inland and

coastal waters by 2015; and

• Water Act 2003 (Ref. 9.9) – amends the Water Resources Act 1991 and the Water

Industry Act 1991 to formalise the Government’s commitment to the sustainable

management and use of water resources.

Planning Policy

9.16 Planning policy at the national, regional, county and local level and its relevance to

environmental design and assessment is discussed in Chapter 5 – Assessment of

Relevant Policies.

National Planning Policy Framework (NPPF), 2012 (Ref. 9.10)

9.17 This is new national policy (in England) and replaces all previous Planning Policy

Statements (PPS) and Policy Planning Guidance (PPG) notes. In relation to ground

condition, the NPPF Paragraph 109 states that The planning system should contribute

to and enhance the natural and local environment by:

“- Preventing both new and existing development from contributing to or being put at

unacceptable risk from, or being adversely affected by unacceptable levels of soil,

air, water and noise pollution or land instability.”

9.18 The NPPF Paragraph 120 states that:

“To prevent unacceptable risks from pollution and land instability, planning policies

and decisions should ensure that new development is appropriate for its location. The

effects (including cumulative effects) of pollution on health, the natural environment

or general amenity, and the potential sensitivity of the area or proposed

development to adverse effects from pollution, should be taken into account. Where

a site is affected by contamination or land stability issues, responsibility for securing a

safe development rests with the developer and/or landowner.”




“Planning policies and decisions should also ensure that:

- the site is suitable for its new use taking account of ground conditions and land

instability, including from natural hazards or former activities such as mining, pollution

arising from previous uses and any proposals for mitigation including land remediation

or impacts on the natural environment arising from that remediation;

- adequate site investigation information, prepared by a competent person, is

presented.”


“Local planning authorities should adopt proactive strategies to mitigate and adapt

to climate change, taking full account of flood risk, coastal change and water supply

and demand considerations.”

Broxtowe Local Plan

9.21 Relevant local policies wihtin Broxtowe Local Plan, 2004 (Ref. 9.11 include the

folllowing;

• E1: Planning permission will not be granted for development which does not

include the following criteria where relevant:

• J- Sustainable techniques to minimise the impact of surface water discharges.

• E26: Pollution: Planning permission will not be granted for development which

would result in a significant deterioration in air quality, significant loss of health or

amenity to the occupants of nearby premises due to pollution, or contamination

of either surface waters or the site of the development or other land nearby

Guidance

9.22 The following Pollution Prevention Guidelines (PPG) issued by the EA are considered to

be relevant to this assessment:

• EA, pre 2007. PPG1 ‘General Guidance to the Prevention of Pollution’ (Ref. 9.12);

• EA, October 2007. PPG5 ‘Works or Maintenance in or Near Water’ (Ref. 9.13);

• EA, pre 2007. PPG6 ‘Working at Construction and Demolition Sites’ (Ref. 9.14); and

• EA, March 2009. PPG21 ‘Incident Response Planning’ (Ref. 9.15).



9.23 Other guidance documents considered to be relevant to this assessment include the

following:

• Construction Industry Research and Information Association (CIRIA), 2007. CIRIA

697: The SuDS Manual (Ref. 9.16);

• CIRIA, 2001. Guidance ‘C532 – Control of Pollution from Construction Sites’ (Ref.

9.17); and

• EA, 2009. Flood Risk Standing Advice for England (Ref. 9.18) - This advice reflects

the policy contained in PPS25 and provides standard information on whether a

development is suitable with regards to flood risk.

Existing Baseline Conditions

9.24 The baseline conditions of the Site are set out below. Further information on the

geoenvironmental ground conditions are set out in Chapter 13 – Ground Conditions

and Hydrogeology and Contamination .

Topography and Surface Cover

9.25 The site topography generally falls from southwest to the northeast, with an overall

level difference of approximatey 32.5m. Surface cover predominantly comprises

open grassland and agricultural land (including bare soil). An area of woodland is

also present within the southwest.

Geology and Hydrogeology

9.26 Preliminary ground investigation undertaken within the Geoenvironmental Desk Study

and Terrain Assessment (Appendix 13.1) indicates that the Site is underlain by

localised Made Ground and Alluvium, underlain by the Cadeby Formation

(encountered as weathered sandstone and limestone). Geological mapping

indicates that this will be underlain by Middle Coal Measures.

9.27 Groundwater was not encountered during the preliminary ground investigation.

Groundwater is anticipated to be present at depth in the Cadeby Formation.

9.28 Soakaway test results from 3 no. trial pits performed in one area of the site indicate

infiltration rates of 1.6 x 10-5 m/s in the Alluvium stratum and 2.1-2.9 x10-5 m/s in the

weathered sandstone.



Surface Water Features

9.29 No surface water features have been identified on the Site. The following surface

water features have been identified in proximity to the Site:

Table 9.1: Surface Water Features in Proximity to the Site

9.30 The unnamed drain originates from ‘Issues’ within Chilwell Dam Plantation located

adjacent to the A6002 Woodhouse Way to the south-east of the Site. The drain flows

east then north-east through Broxtowe Country Park, before entering a culvert and

into Hempshill Brook approximately 1.7km to the east of the Site.

River Basin Management Plan Classification

Surface water course

Direction and distance from Site

Details

Chemical Ecological

Unnamed drain 100m south-east Flows East then

North East

Discharging to

Hempshill Brook

NA NA

Hempshill vale

also called ‘the

lake’

215m north-

west

Associated with

Hempshill Brook

NA NA

Hempshill Brook 441m north-east Flows from west

to east

Discharging to

River Leen

Good Moderate

River Leen 2.5km east Flows from

North to south

Does Not

Require

Assessment

Moderate

River Erewash 3.5km south-

west

Flows in a south

easterly

direction

Fail Moderate



9.31 Hempshill Brook flows west to east and is culverted prior to its confluence with the

unnamed drain. The brook also appears to be culverted until its confluence with the

River Leen some 3.7km to the east of the Site.

Drainage and Sewerage

9.32 As the Site is greenfield it is anticipated that there are no private drainage systems

within the Site boundary. There does not appear to be any existing surface water

outfall in any direction from the Site.

9.33 It is understood that Severn Trent Water (STW) currently supply the surface water

drainage and foul drainage in proximity to the Site and would be the suppliers for the

Proposed Development.

9.34 STW sewer records show that there are separate public surface, foul and combined

water sewers within the road network for the existing residential development to the

east of the A6002 Woodhouse Way. The foul and public sewers are predominantly

small diameter (mainly 150mm and 225mm).

9.35 The foul sewers are predominantly low diameter; however, there is spare capacity of

between 10 and 20 l/sec. Subject to confirmation of the proposed new flows, STW

consider that the additional flow could be accommodated (Letter Ref. WT25409 /

8058844 dated 22nd September 2011 included within the FRA dated December 2011).

9.36 Highway drains and combined sewers are located to the north. BBC, who maintains

the drainage in the A6002 Woodhouse Way and the A610, as agents for Nottingham

County Council, confirmed that surface water sewers and drains in proximity of the

Site flow by gravity towards the Hempshill Brook and Hempshill Vale pond on the

northern side of the A610.

Flood Risk

9.37 The Site is within Fluvial Flood Zone 1: Low Probability. This zone comprises land

assessed as having a less than a 1 in 1000 annual probability of river or sea flooding in

any year (<0.1%).

9.38 The Flood Risk Assessment (Planning Reference TP/OPA/DOC/10) concluded that

there is a low risk of flooding from all assessed sources of flooding (i.e. groundwater,

surface water, fluvial, tidal and artificial sources).



9.39 There are no formal records of historical flooding at the Site.

Future Baseline

9.40 Should the Proposed Development not proceed it is considered that the future

baseline conditions in relation to drainage, flooding and water resources would

remain relatively unchanged.

9.41 In the longer term, the risk of flooding at the Site may increase with the effects of

climate change due to increased frequency of extreme rainfall events.

Predicted Effects


9.42 Potential significant effects considered in the site preparation and construction phase

include:


bodies and drainage features; and



Potential increase in physical contamination (i.e. sedimentation) to surface water

bodies and drainage features

9.43 The closest surface water course is an unnamed drain 100m to the south-east of the

Site, ultimately discharging to the river Leen. Potential surface water receptors are

identified in Table 9.1. Current chemical water quality in Hempshill Brook (441m to the

north-east of the Site) and the River Leen (2.4km to the east) is classifed under the EA

River Basin Management Plan as ‘Good’.

9.44 Surface cover is currently predominantly soft cover. As such a high proportion of

surface water is currently likley to infiltrate to groundwater.

9.45 There is no current formal drainage system on Site.

9.46 During the site preparation and construction phase of the Proposed Development

there will be a number of activities which could reduce surface water quality with

respect to physical contaminants. These include:



• Soft strip;

• Movement and use of static and mobile plant/construction vehicles such as

excavators, dumper trucks, haulage trucks and screening equipment;

• Materials handling, storage, stockpiling, spillage and disposal;

• Bulk earthworks to ground formation levels;

• Tree protection works;

• Installation of infrastructure and roads and haul routes associated with this phase;

• Excavation and foundation construction;

• Construction of proposed buildings;

• Construction of drainage runs and utilities ducts;

• Construction of strategic infrastructure such as works to public highways; and

• Landscaping.

9.47 The site preparation and construction phase may lead to the disturbance and

mobilisation of physical contaminants (i.e. dust, sediments, and muds). In particular

during periods of heavy rainfall, vehicle movements resulting in damage to soil

structure may generate increased sedimentation within surface run-off. In addition,

during periods of dry, windy weather wind-blown dusts generated by excavation of

soils have the potential to directly reduce the quality of surface water features.

9.48 These activities may result in sediments directly (e.g. wind-blown) or indirectly (e.g. via

surface water runoff) entering surface water features, impacting on the physical

quality of the surface water receptors in the surrounding area.

9.49 This has the potential to also subsequently impact the chemical and biological quality

of surface water receptors. The chemical water quality is discussed in Chapter 13 –

Ground Conditions, Hydrogeology and Contamination. The biological quality could

be impacted indirectly through sediment smothering feeding and breeding grounds

and physically altering the habitat.

9.50 Sediment accumulation in the drainage system (off site) may also reduce its capacity

and therefore increase potential flood risk.

9.51 Due to the distance of surface water features from the Site the sensitivity of the

receptors to physical contaminants is considered to be medium and, the magnitude

of change, prior to mitigation, is minor. Therefore, there is likely to be a direct,



temporary, medium-term effect on surface water receptors of minor negative

significance prior to the implementation of mitigation measures.

Increase in risk of surface water and drainage flooding on construction workers and

construction activities.

9.52 The Site is located within EA Flood Zone 1. The current risk of surface water and

drainage flooding is low. Surface water drainage is currently predominantly

anticipated to be by infiltration as the Site is undeveloped with soft cover across the

majority of Site.

9.53 Any overland flow that did flow into or out of the Site would currently follow the line of

least resistance and follow natural topography; however, the topography is likely to

change to some extent during the site preparation and construction phase.

9.54 Surface water and drainage flooding, especially after extreme rainfall events, has the

potential to harm earthworks workers on-site if it is received in large volumes,

particularly if they are working in excavations which have the potential to fill with

water.

9.55 Surface cover at the Site is currently predominantly permeable materials. During the

site preparation and construction phase the extent of hardcover will increase which is

likely to result in decreased volumes of rainfall infiltration and increased volumes of

surface water run-off.

9.56 Any flows resulting from surcharging of the drainage or sewer system in close proximity

to the Site during extreme rainfall events would be short-term, relatively shallow in

depth and would pass through the Site following the natural topography.

9.57 The sensitivity of site preparation and construction workers and activities to surface

water and drainage flooding at the Site is high and the magnitude of change should

this occur, prior to mitigation, is minor. Therefore, there is likely to be a direct,

temporary, medium-term effect on site prepartation and construction workers and

activities of minor negative significance prior to the implementation of mitigation

measures.

Operational Phase

9.58 Potential significant effects considered in the operational phase include:




bodies and drainage features;

• Increase in, or change in patterns of, surface water and drainage flooding and

associated flood risk on future populations and third parties;

• Increase in foul drainage and associated demand on sewage treatment works;

and


bodies and drainage features.

9.59 The closest surface water course is an unnamed drain 100m to the south-east of the

Site, ultimately discharging to the river Leen. Potential surface water receptors are

identified in Paragraph 9.29 of this Chapter. Current chemical water quality in

Hempshill Brook (441m to the north-east of the Site) and the River Leen (2.4km to the

east) is classifed under the EA River Basin Management Plan as ‘Good’.

9.60 Surface cover is currently predominantly soft cover. As such a high proportion of

surface water is currently likley to infiltrate to groundwater. The proportion of bare soil

area and permeable surfaces will be reduced from current in the Construction Phase.

Therefore the volume of surface water runoff will increase.

9.61 During the operational phase of the Proposed Development there will be a number of

activities and land uses which could influence surface water quality with respect to

physical contaminants. These include:

• Bare ground landscaping such as garden areas;

• Increased hardcover;

• Use of a drainage system (providing a pathway to surface watercourses); and

• Use of roads and access routes.

9.62 Physical contamination mitigation measures are proposed as part of the Proposed

Development including silt traps and settlement ponds. These measures will reduce

the effects of physical contamination on surface water courses.

9.63 The operational activities may lead to the mobilisation of dusts and sediments. In

particular, periods of heavy rainfall, may generate increased sedimentation within

surface run-off from gardens and bare soil areas. Conversley, during periods of dry,

windy weather wind-blown dusts generated by soils have the potential to directly

reduce the quality of surface water features.



9.64 These activities may result in sediments directly (e.g. wind-blown) or indirectly (e.g. via

surface water runoff) entering surface water and drainage features, impacting on the

physical quality of the surface water receptors in the surrounding area.

9.65 This has the potential to also subsequently impact the chemical and biological quality

of surface water receptors. The chemical water quality is discussed in Chapter 13 –

Ground Conditions, Hydrogeology and Contamination. The biological quality could

be impacted indirectly through sediment smothering feeding and breeding grounds

and physically altering the habitat.

9.66 During the operational phase the potential for sediment entrainment in surface water

run-off is anticipated to decrease from that anticipated in the site preparation and

construction phase. As it will be a controlled development area, there is anticipated

to be a low volume of physical contaminants (sediment) which could potentially be

entrained in surface water run-off over hard standing and landscaping areas and

discharged to surface water receptors, reducing the physical, chemical and

biological quality.

9.67 A Surface water and foul drainage network (as outlined in the drainage strategy, Ref.

9.19) will be in place. Additionally, the Proposed Development includes swales on the

down gradient boundary of carparking areas and open space areas and two

balancing basins for extreme rainfall events, furthermore, the updated FRA (Planning

Reference TP/OPA/DOC/10), highlights the potential need for off site outfall suring

such events. The site master plan shows trapped gullies will be utilised within the

highway to minimise the risk of silts entering the soakaways or swales and reducing the

capacity. This will also help to reduce flood risk from drains overtopping.

9.68 Due to the distance of the surface water features from the Site the sensitivity of the

receptors to physical contaminants is considered to be medium and, also due to the

distance, the magnitude of change, prior to mitigation, is minor. Therefore, there is

likely to be a direct, permanent, long-term effect on surface water receptors of minor

negative significance prior to the implementation of mitigation measures.

Increase in, or change in patterns of, surface water and drainage flooding and

associated flood risk on future populations and third parties

9.69 The Site is located within EA Flood Zone 1 and no records of flood events at the Site

have been identified. The current risk of surface water and drainage flooding is low.



9.70 The Site currently consists of open grass land and arable farmland, thus is classified as

a Greenfield site. There does not appear to be an existing surface water outfall in any

direction. The Proposed Development will increase the proportion of impermeable

surfacing and therefore will increase the surface water run-off volumes. Unmitigated

this would have the potential to increase surface water and drainage flood risk.

9.71 The FRA (Planning Reference TP/OPA/DOC/10), section 5.2.1 states that the EA

recommend that: “surface water run-off should be controlled as near to it source as

possible through a sustainable drainage approach to surface water

management…This approach can also offer other benefits in terms of promoting

groundwater recharge, water quality improvement and amenity enhancements.”

Approved Document Part H of the Building Regulations 2000 (Ref 9.20) sets out a

hierarchy for surface water disposal which encourages a SuDS approach.

9.72 A conceptual drainage strategy was designed as part of WSP 2013 FRA (Planning

Reference TP/OPA/DOC/10), following the SuDS hierarchy. This will be confirmed at

the detailed design stage.

9.73 The surface water drainage strategy proposes to attenuate the surface water on Site

as close to its source as possible. It recommends a combination of a balancing

basin/treatment reed bed, linked shallow swales, a ditch on the eastern Site

boundary, soakaways and a positive sewer system.

9.74 The balancing basin will be located in the north-east corner of the Site to follow the

natural fall of the ground.

9.75 The ditch on the eastern boundary will also act as a storage facility and will control

surface water flow.

9.76 Drainage strategies for new developments must allow for an increase in rainfall

intensities of 30% due to climate change in line with recommendation in the NPPF

which states that Local Plans should take account of climate change over the longer

term, including factors such as flood risk, coastal change, water supply and changes

to biodiversity and landscape. The EA aspires to reduce the rate of surface water

discharge from new developments for any given storm event and specifies that the

drainage system should be designed to control runoff for up to the 1 in 100 year

rainfall event.

9.77 The Site will be classified by STW as a Greenfield site, therefore the peak storm flows

(for 30 year design storm) have been estimated based on an assumed limited



discharge rate of 5 litres/second/hectare. Greenfield run-off rates are likely to be

requested by STW and the EA with a recommendation of 5l/s/ha. This is applied to the

gross area of the Site and would be subject to confirmation at the detailed design

stage.

9.78 Based on the total site area of 32.5 Ha, the exisiting Greenfield discharge rate equates

to approximatley 160 l/s. Allowable discharge rates will be confirmed by liaision with

STW and EA.

9.79 The drainage strategy (Ref. 9.19) considered an impermeable area of 50% of the total

Site. The calculated attenuation volume required on Site for a 1 in 100 year storm

event plus 30% climate change, is approximately 7,500-10,350 cubic metres.

9.80 A positive sewer system, potentially with the use of oversized pipes depending on the

limiting discharge rate, will collect the surface water drainage and direct it to the

SuDS facilities.

9.81 It is anticipated that the ditch on the eastern Site boundary and proposed swales will

collect surface water from the highway thus attenuating and treating run-off prior to

outfall.

9.82 Shallow swales and permeable paving are proposed throughout the Site and along

the southern and eastern boundaries. These will allow infiltration of water on Site

controlling potential surface water run-off close to source. Soak aways will be used

where ground conditions allow. Preliminary soakaway test data is presented in WSP

Environmental’s Geoenvironmental Desk Study and Terrain Assessment, dated

December 2011 (Appendix 13.2) infilltration rates varyied from 1.6x10-5 m/s to 2.9x10-5

m/s. Additional testing will be required across the remainder of the Site to confirm the

suitability of drainage conditions.

9.83 The proposed Drainage Strategy is presented in WSP Drawing No. 1066/D/001 Rev B of

the FRA (Planning Reference TP/OPA/DOC/10). Indicative soakaway locations are

presented on this drawing.

9.84 Balancing basins will be used to overcome excess surface water during heavy rain

events, prior to infiltration via soakaways. These will be designed to allow for a 1 in 100

year storn plus 30% climate change allowance.



9.85 The balancing basins would form attenuation pond storage areas prior to potential

connection points to the north-east at the culverted watercourse and south-east at

the unnamed brook adjacent to the A6002 Woodhouse Way.

9.86 As part of the design, the highway network will drain to a series of soakaways and/or

swales adjacent to the highway. Trapped gullies will be utilised within the highway to

minimise the risk of silts entering the soakaways or swales and reducing the capacity.

This will also help to reduce flood risk from drains overtopping.

9.87 The design of the Proposed Development has ensured that substantial and sufficient

storage capacity is available on Site to mitigate the effects of extreme storm events

and climate change, thereby reducing the associated flood risk.

9.88 The sensitivity of future populations and third parties to surface water and drainage

flooding at the Site is high and the magnitude of change should this occur, prior to

mitigation, is minor. Therefore, there is likely to be a direct, temporary, long-term effect

of minor negative significance on future populations and third parties prior to the

implementation of mitigation measures.

Increase in foul drainage and associated demand in the sewage treatment works

9.89 The Site is currently open field so no foul water drainage system is present on the Site.

9.90 The foul flow from the Proposed Development will connect within the Mornington

Crescent road, located to the east of the Site off the A6002 Woodhouse Way, at

manhole no. 5001 (150mm diameter) and manhole no. 7402 (225mm diameter).

9.91 Consultation with the service provider STW (included within the FRA (Planning

Reference TP/OPA/DOC/10) has confirmed that the estimated spare capacity to be

approximately 10l/s at 5001 and 15-20l/s at 7402, subject to approval of a formal

Section 106 Agreement.

9.92 Due to receipt of capacity confirmation from STW, the sensitivity of the foul drainage

network to increases in foul drainage at the Site is low and the magnitude of change,

prior to mitigation, is minor. Therefore, there is likely to be a direct, permanent, long-

term effect on the foul drainage network of negligible significance prior to the

implementation of mitigation measures



Mitigation and Enhancement Measures




9.93 Prior to the commencement of the site preparation and construction phase, Site run-

off will be controlled to mitigate both flood risks and sediment loading. It is assumed

that a phased temporary drainage network will be implemented to prevent sediment

laden surface run-off from leaving the Site or entering surface water off site. The

proposed temporary drainage strategy for this phase of the Proposed Development

has not yet been developed. It is understood that this will be addressed during the

detailed design stage.

9.94 A variety of good environmental site practices will be implemented to avoid or

minimise effects at the source. Such measures will be provided in the Construction

Environmental Management Plan and shall include, but are not limited to, the

following:

• Working areas shall be clearly defined to ensure the disturbance of soils is

minimised, where possible;

• Haul routes and accesses shall be clearly defined to minimise the risk of accidents;

• The cleaning of vehicle wheels prior to leaving Site;

• Controlled and covered waste storage areas;

• Dust suppression (i.e. damping down);

• Provision of environmental awareness training for site workers; and

• Installation of systems such as silt traps and swales designed to trap silty water

including adequate maintenance and monitoring of these to ensure

effectiveness, particularly after adverse weather conditions.

9.95 The position and extent of working areas should reflect the sensitivity of surrounding

areas and works being carried out. The contractor should appraise the suitability of

such working areas in this respect as part of working method statements.

9.96 Where necessary, all site works should be undertaken in accordance with the EA’s

Pollution Prevention Guidelines, in particular:



• PPG1 ‘General Guide to the Prevention of Water Pollution’ (Ref 9.13);

• PPG6 ‘Working at Construction and Demolition Sites’ (Ref 9.15); and

• PPG21 ‘Incident Response Planning’ (Ref 9.16).

9.97 Earthworks and construction activities should also be undertaken in accordance with

CIRIA guidance ‘C532 – Control of Pollution from Construction Sites’ (Ref 9.17).

9.98 All site works and ground works should be undertaken in accordance with the

Considerate Contractors Scheme to help ensure a well-managed operation which

minimises environmental risks.

9.99 Best practice recommendations for the prevention of contamination will be outlined

in more detail in a Construction Environment Management Plan (CEMP) or equivalent,

which will be developed and agreed with the appropriate regulators, prior to site

preparation and construction activities commencing.

9.100 The CEMP will include the following pertinent items:

• Programme and phasing details of works;

• A broad plan of construction works, highlighting the various stages and their

context within the project, including a schedule of materials and manpower

resources and plant and equipment schedules;

• Detailed site layout arrangements (including requirements for temporary works),

plans for storage, accommodation, vehicular movements, delivery and access;

• Prohibited or restricted operations (locations, hours, etc.);

• Details of plant used; and

• Details of operations that are likely to result in disturbance, with an indication of

the expected duration of each phase and key dates.


construction activities

9.101 Workers on-site will be made aware of risks and how to mitigate them during the site

preparation and construction phase.

9.102 Prior to the commencement of the construction phase, site surface run-off will be

controlled to mitigate flood risks as discussed in the sediment loading section above.

At this time, the proposed drainage strategy for the site preparation and construction



stage of the Proposed Development has not been developed in detail. It is

understood that this will be addressed during the detailed design stage.

9.103 Consideration of the design of site levels during construction should also mitigate

against the risk of surface water and drainage flooding.

Operational Phase

Potential increase in physical contamination (i.e. sedimentation) to surface waters


9.104 The detailed surface water drainage system has not been finalised and this will be

addressed during the detailed design stage in collaboration with the appropriate

regulators.

9.105 A drainage network will be implemented with features designed to prevent sediment

laden surface run-off from leaving the Site via surface water runoff or the drainage

system.

9.106 Although the proposed drainage strategy has not yet been finalised, it is anticipated

that proposed pollution control measures will include trapped road and car park

gullies and oil interceptors which will attenuate physical contaminants before

discharge. These facilities will be subject to routine maintenance.

9.107 Discharge rates, consent, capacity available and sewer requisitions would be agreed

with STW, the EA, and BBC with supporting hydraulic modelling if required, prior to

finalisation of the detailed design.



9.108 The current drainage proposals include soak aways, swales and balancing basins

however, the detailed surface water drainage system has not been finalised and this

will be addressed during the detailed design stage in collaboration with the

appropriate regulators.

9.109 Further ground investigation and infiltration testing will be undertaken prior to detailed

design of the SuDS features. Soakaways will be used where possible to reduce surface

runoff volumes. Filtration trenches and swales to both attenuate and store runoff as

well as provide water quality improvements, ecological and amenity value.



9.110 Surface water discharge from the Site will be reduced by a minimum of 20% over the

existing calculated rates for the existing 1 in 100 year rainfall event. In addition, on-site

SUDS will be designed to accommodate the 1 in 100 year event plus climate change

(30%) rainfall event with no additional increase in flows. These measures are in line

with EA requirements.

9.111 Once infiltartion tests are complete, the capability of the use of infiltration SuDS on Site

can be assessed and changes made to the strategy where appropriate.

9.112 Finished site levels, where possible, will be engineered to provide positive drainage

and prevent ponding. Gradients of external areas will be designed to fall away from

buildings, such that any overland flow resulting from extreme events will follow the line

of least resistance, follow natural topography and be channelled away from the

entrances. The accumulation of standing water will therefore not occur and thus not

pose a risk, and extreme event storms will not result in buildings flooding or access to

buildings being prevented.


9.113 Although STW have confirmed capacities based on preliminary calculations, the

detailed foul drainage system for the Site has not been finalised to date and this will

be addressed during the detailed design stage in collaboration with STW. This will

include measures for minimising foul drainage in combination with measures for

minimising water use.

Residual Effects




9.114 The sensitivity of surface water receptors to physical contaminants is medium and the

magnitude of change, following mitigation, is negligible. Therefore, there is likely to be

a direct, temporary, medium-term effect of negligible significance on surface water

receptors following the implementation of mitigation measures.




construction activities.

9.115 The sensitivity of construction workers and activities to surface water and drainage

and flooding at the Site is high and the magnitude of change should this occur,

following mitigation, is negligible. Therefore, there is likely to be a direct, temporary,

medium-term effect of negligible significance to construction workers and activities

following the implementation of mitigation measures

Operational Phase



9.116 The sensitivity of surface water receptors to physical contaminants is medium and the

magnitude of change, following mitigation, is negligible. Therefore, there is likely to be

a direct, permanent, long-term effect of negligible significance on surface water

receptors (rivers) following the implementation of mitigation measures.



9.117 It is considered that the Proposed Development can be undertaken in a sustainable

manner to maintain the low level flood risk at the Site by utilising SuDS techniques (e.g.

soakaways and storage basins)and engineering site levels.

9.118 The sensitivity of future populations and third parties to surface water flooding at the

Site is high and the magnitude of change should this occur, following mitigation, is

negligible. Therefore, there is likely to be a direct, temporary, long-term effect of

negligible significance on future populations and third parties following the



9.119 The sensitivity of the foul drainage network is low and the magnitude of change,

following mitigation, is negligible. Therefore, there is likely to be a direct, permanent,

long-term effect of negligible significance on the foul drainage network following the




Cumulative Effects and/or Predicted Interaction of Factors

Effect Interactions

9.120 The effects on surface water receptors from physical contaminants will be allied with

effects from chemical contaminants which are discussed in Chapter 13 – Ground

Conditions and Hydrogeology and Contamination. Although these two types of

contaminants will cumulatively reduce the water quality of any receiving water body,

the effects will be mitigated by implementing similar measures including the use of

good environmental site practices.

In Combination Effects

9.121 There are four commited developments in proximity to the Site. It is likely that these

developments will experience similar drainage, flooding and water resources effects

which will be managed in a similar manner to the Proposed Development.

9.122 An FRA prepared (Ref 9.1) for Oxylane Village (the land south west of M1 at Junction

26), states that this committed development is also at a low risk of flooding and it

would also be feasible to use infiltration techniques for soakaway design, ponds and

swales in the lower reaches of the Site. Flood management is likely to be similar at

both sites and it is not considered that the surface water flood risk will be cumulative

due to the proposed surface water drainage strategies.

9.123 Although the risk of physical contamination at other sites remains outside the

Applicant’s control, it is assumed that the committed developments will adhere to

similar mitigation measures as required and enforced by planning conditions and

legal agreements which will minimise the risk. Therefore the cumulative effect will not

be of greater significance.

Limitations

9.124 Outline designs for the surface water drainage strategy during the site preparation

and construction phase and the operational phase have been utilised in the above

assessment. This Chapter supports an outline application with no confirmed detailed

surface water drainage design that seeks to establish the principle of the scheme.

Assumptions have been made in the assessment sections above on drainage design

and capacity. Following the detailed design phases, should the design details vary in

a manner that compromises the assessments, further assessment will be required.



9.125 It is assumed that the mitigation measures presented in this Chapter will be

undertaken by the appointed construction contractors (e.g. preparation and

adherence to the CEMP).

9.126 FRAs for two of the four commited devlopments were not available for review.

Summary and Statement of Significance

• The Site is currently greenfield. Surface water receptors in proximity of the Site

include, an unnamed drain (100m south east); Hempsvale pond (225m north

west), Hempshill Brook (441m north east) and River Leen (2.5km east). Hempshill

brook and River Leen have a river basins management plan chemical

classification of Good and no assessment required respectively. No drainage

infrastructure is currently present at the Site, and surface cover is

predominantly permeable.

• Based on the available baseline data, it is considered that the following

significant risks may be associated with the Site: increase in physical

contamination (i.e. sedimentation) to surface water bodies; increase in, or

change in patterns of, surface water and drainage flooding and associated

flood risk on future populations and third parties; and, increase in foul drainage

demand on sewage treatment works.

• During the site preparation and construction phase a temporary drainage

system will be in place, contractors environmental management plan will be

prepared and EA guidance will be adopted to ensure that construction

activities will not have a significant negative effect on water quality and flood

risk will be minimised.

• The proportion of impermeable cover will increase in the operational phase

mitigated with surface water drainage via a combination of SuDS techniques

including swales, soak aways and balance basins. Further infiltration tests will

be carried out at detailed design stage.

• Finished floor levels and external gradients will be designed to avoid the

accumulation of surface water and balancing basins will be provided on-site

to manage the 100-yr return period in line with climate change. STW has

confirmed capacity of their foul drainage system.

• These mitigation measures provide protection of the water environment in line

with national, regional and local policies; NPPF, Regional Spatial Strategy for



the East Midlands, 2000 and local policies within Broxtowe Local Plan, 2004 E1,

E26 and E28 and in accordance with legislation including the Water

Environment Regulations (2003) and the Water Act (2003).

• Following incorporation of the mitigation measures in accordance with current

best practice and the relevant guidance, it is considered that the residual

impacts in relation to water quality and flooding for the site preparation,

construction chase and in relation to water quality, flooding and foul drainage

capacity for the operational phase are all likely to be negligible.



References

• Ref 9.1 – Oxylane Village Flood Risk Assessment

• Ref. 9.2 Environmental Protection Act (EPA) 1990

• Ref. 9.3 Water Industry Act, 1991

• Ref 9.4 The Water Resources Act 1991

• Ref. 9.5 Land Drainage Act 1991

• Ref. 9.6 Land Drainage Act 1994

• Ref. 9.7 The Environment Act 1995

• Ref. 9.8 The Water Framework Directive (2000/60/EC) (WFD)

• Ref. 9.9 Water Act 2003

• Ref. 9.10 National Planning Policy Framework (NPPF), 2012

• Ref. 9.11 Broxtowe Loal Plan, 2004

• Ref. 9.12 EA, pre 2007. PPG1 ‘General Guidance to the Prevention of Pollution’

• Ref. 9.13 EA, pre 2007. PPG5 ‘Works or Maintenance in or Near Water’

• Ref. 9.14 EA, pre 2007. PPG6 ‘Working at Construction and Demolition Sites’

• Ref 9.15 EA, March 2009. PPG21 ‘Incident Response Planning’

• Ref. 9.16 Construction Industry Research and Information Association (CIRIA),

2007. CIRIA 697: The SuDS Manual

• Ref. 9.17 CIRIA, 2001. Guidance ‘C532 – Control of Pollution from Construction

Sites’

• Ref. 9.18 -EA, 2009. Flood Risk Standing Advice for England

• Ref. 9.19 – Drainage Strategy, WSP, December 2011

• Ref. 9.20 - Building Regulations 2000

9. hydrology and water resources -...

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