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9. Hydrology and Soil

Introduction

9.1 This chapter of the ES considers the assessment of the potential impacts of the proposed

development on the surface water and groundwater environment both in terms of quality

and quantity, and provides an assessment of flood risk and likely changes to existing

flood risk. In addition, it also addresses the potential impact of the development

proposals on soil both on the site and its immediate surroundings.

9.2 The assessment considers potential impacts during the construction, operation and

decommissioning of the proposed Renewable Energy Plant and outlines mitigation

measures to control the predicted effects of the proposals. The scope of the assessmentwas to identify:

• Constraints on the development associated with the hydrology and soil, so that

the most sensitive areas can be avoided or protected;

• Potential risks associated with construction, operation and decommissioning

activities that can be controlled through best management practices;

• Mitigation measures to control and reduce other potential impacts of the

development on the water and soil environment; and

• The significance of residual effects.

9.3 The assessment is primarily concerned with the site and immediate surrounding area.

However, where a hydrological connection deems it necessary, the assessment

considered locations beyond this extent.

Assessment Methodology and Signif icance Cri ter ia

9.4 This section outlines the methodology adopted to assess the environmental impacts of

the proposal upon the local water and soil environment. The methodology is based upon

the collection of information from a wide variety of data sources including published

material and consultation with statutory bodies.

Consultation

9.5 Before undertaking the assessment, consultation with stakeholders with an interest in the

water environment, primarily flood risk, were contacted. The Environment Agency (EA)

provided response to a request for guidance on the approach to assessment of flood risk



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at the site. The approach adopted is in line with Planning Policy Statement 25:

Development and Flood Risk (PPS25) and is outlined in detail within a separate Flood

Risk Assessment report contained within Appendix 3.1.

Data Sources

9.6 The assessment is based upon the collection of information from a wide variety of data

sources including published material and consultation with statutory bodies. Table 9.1

details the data sources referred to throughout the text.

Table 9.1 Data Sources

Topic Source of data and information

Climate

Rainfall Flood Estimation Handbook (Centre of Ecology andHydrology, NERC, 1999); Environment Agency; CEHHydrometric Register

Topography

Elevation, relief Ordnance Survey Mapping Explorer 277 Manchester &Salford (1:25,000)

Ordnance Survey Mapping Landranger 109 Manchester (1:50,000)

Surface Water FloodingWater QualityRecreational waters andfisheries

Environment Agency (www.environment-agency.gov.uk)Consultation and published sources on their website

Groundwater

Aquifer properties Environment Agency (www.environment-agency.gov.uk)published sources on their website

British Geological Survey ‘Hydrogeological Map of Clwydand the Cheshire Basin’, 1989 (scale 1:100,000)

British Geological Survey ‘The Physical Properties of Major Aquifers in England and Wales’ (1997)

Geology

Solid and drift British Geological Survey Solid & Drift Geology Mapping,Map Sheet 85 (Scale 1:50,000)



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Topic Source of data and information

Soil

Soil type

Ground Conditions andcontamination

Soil Map of England and Wales (Scale 1:250,000), SoilMap 3, Soils of Midland and Western England

Phase 1 Engineering and Environmental Assessment,Proposed Biomass Fuelled Power Generation Plant Adjacent Barton Bridge Manchester, CoDa Structures,March 2010

Water resources

Abstractions andDischarges

Envirocheck Report, reference 30245393_1_1, dated 19Feb 2010

Legislative Context and Guidance

9.7 In addition to the planning policy framework relevant to this proposal as set out in the

Planning Statement which accompanies the planning application and this ES, this

assessment has been undertaken with regard to statutory and general guidance, and a

range of environmental legislation including the following:

Statutory and General Guidance

• Planning Policy Statement 25 (PPS25) – Development and Flood Risk (DCLG

2010);

• PPS25: Development and Flood Risk Practice Guide (DCLG, updated Dec

2009);

• Environment Agency Pollution Prevention Guidance Notes (PPG):

̶ PPG1 General Guide to the prevention of water pollution;

̶ PPG2 Above ground oil storage tanks;

̶ PPG3 Use and Design of Oil Separators in Surface Water Drainage

Systems;

̶ PPG5 Works in, near or liable to affect water courses;

̶ PPG6 Working at construction and demolition sites;

̶ PPG7 Refuelling facilities;

̶ PPG21 Pollution incident response planning; and,

̶ PPG23 Maintenance of structures over water;



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• CIRIA publications:

̶ C532 Control of water pollution from construction sites (2001);

̶ C649 Control of water pollution from linear construction sites; and

̶ C650 Environmental good practice on site (2005);

• Environment Agency, Groundwater protection: policy and practice (GP3)(2007);

• Environment Agency, Policy regarding culverts;

• DEFRA Code of Practice for the sustainable use of soils on construction sites

(2009); and,

• DEFRA Good practice guide for handling soils (MAFF 2000).

Legislation

• Environmental Protection Act 1990;

• Environment Act 1995;

• Water Resources Act 1991;

• EU Water Framework Directive (2000/60/EC);

• Groundwater (England and Wales) Regulations (2009);

• Private Water Supplies Regulations (2009)

• EC Freshwater Fish Directive (2006/44/EC);

• Land Drainage Act 1991; and

• Water Supply (Water Quality) Regulations 2007 (Amendment)

Significance Criteria

9.8 There are no published guidelines or criteria for assessing and evaluating effects on

hydrology, hydrogeology, geology or soil within the context of an ES. The assessment

will be based on a methodology derived from Institute of Environmental Management and

Assessment (IEMA) guidance. The evaluation will also be based on Environment Agency

guidance within their Pollution Prevention Guidance documentation (GP3, 2007). The

methodology sets a list of criteria for evaluating the environmental effects, as follows:



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• The type of effect (i.e. whether it is positive, negative, neutral or uncertain);

• The probability of the effect occurring based on the scale of certain, likely or

unlikely;

• The level of sensitivity of the receptor based on policy importance of the

resource under consideration in a geographical context, on a scale of sensitivity

(i.e. high, medium, low or negligible) as defined within Table 9.2; and

• The magnitude of the effect in relation to the resource that has been evaluated,

quantified using the scale high, medium, low or negligible, defined within Table

9.3.

Table 9.2 Level of Sensitiv ity

Importance andSensitivi ty Context

Water and Soil Definition

High Important on a National or International basis, e.g.Habitat Directive Sites, SSSI.

Public water supplies and principal aquifer

Medium Important in the context of the region; e.g. LocalNature Reserves, catchment scale issues.

Private water supplies, located within vicinity of mainswater supply. Private water supplies used only for agricultural purposes and not drinking water

Low Important in the context of the local district e.g.,secondary aquifer

Negligible Important within watersheds to which the site maydrain; within the site and immediate vicinity e.g., non-aquifer, minor watercourses.





BREP Environmental Statement – Volume 1 161

Impact Significance

9.9 Professional judgement is used to assess the findings in relation to each of these criteria to givean assessment as to significance (in EIA terms) for each effect. Effects are considered to be of

very high, high, moderate, low or negligible. As a guide, a table has been developed whereby

the combination of sensitivity and magnitude give the effect (Table 9.4). In some

circumstances, it is not possible to apply a simple sensitivity and magnitude level to an effect as

there may be many other variables that influence the effect. In such cases a full description of

the reasoning behind the evaluation is given. Where an effect is deemed to be very high, high

or moderate, this is deemed to be significant for the purpose of the Environmental Impact

Assessment. Where an effect is deemed low or negligible, this is deemed as not significant in

terms of the Environmental Impact Assessment.

Table 9.4 Signif icance Matrix

M A G N I T U D E

High Moderate High Very High Very High

Medium Low Moderate High Very High

Low Negligible Low Moderate High

Negligible Negligible Negligible Low Moderate

Negligible Low Medium High

SENSITIVITY

9.10 Once significant effects have been predicted from a project design, measures can be devised to

mitigate the probability or magnitude of those effects, resulting in the residual effects, which can

be predicted and assessed. The design process of the proposal is therefore iterative in that

effects are continually predicted and the design accordingly modified to maximise beneficial

effects and reduce detrimental ones, and the final design is the outcome of that process.

Baseline Conditions

9.11 This section describes the existing hydrological, hydro-geological and soils baseline conditions

at the proposed site and its immediate surroundings.

Site Visit

9.12 A hydrologist undertook a site walkover inspection on 14th

May 2010 to identify the following:




• local hydrological features and the condition of these features;

• extent and condition of Manchester Ship Canal;

• hydraulic controls affecting fluvial and overland flow;

• likely risk of flooding; and

• presence and nature of any existing drainage infrastructure or flood defences.

9.13 Key issues and features were identified, including surface water features, dominant soil types

and other land use characteristics likely to influence hydrological processes. Weather during the

site walkover was light precipitation following a period of predominantly dry conditions.

9.14 No formal outfalls to the Manchester Ship Canal were evident in the vicinity of the site. Flows

within the Canal were observed to be moderate and contained well within the banks of the

channel.

9.15 The site walkover inspection did not identify any evidence of recent or historical flooding within

the site, including land immediately adjacent to the Manchester Ship Canal. Some areas of

localised saturated ground and historic water-logging were noted across the site within

woodland areas.

Climate and Topography

9.16 The site comprises a plot of land, approximately 4.4 ha in plan area, covered by scrubland with

some open areas and informal tracks. The ground vegetation is generally minimal with denser

pockets of growth in open areas. The eastern boundary of the site is aligned with the M60

motorway flyover and generally comprises cleared ground.

9.17 Site survey investigations and Ordnance Survey spot height data show topography across the

site to be generally flat, with elevations ranging between approximately 22.0 m above Ordnance

Datum (AOD) at high points within the site boundary down to 21.0 m AOD at the top of the canal

embankment. The northern border of the site, along the canal embankment, shows a steep

slope from general site elevations down to the waterline which was recorded during the survey

at an average of 17.5 m AOD.

9.18 Average annual rainfall for the area is approximately 882 mm based on data obtained from the

FEH, indicating a relatively wet climate.




Surface Water Hydro logy

9.19 Historical mapping and the site walkover confirmed that no watercourses run through or lie in

the immediate vicinity of the site apart from the Manchester Ship Canal, which is located

adjacent the north western boundary of the site. The Canal effectively acts as the main drain for

the whole of the Greater Manchester region, receiving flows from the River Irwell, River Mersey,

Worsley Brook catchment and Glaze Brook catchment.

9.20 Flows and levels within the canal are managed by the Manchester Ship Canal Company in

‘reach’ sections, each with their own set of control structures and operational protocol. The

reach adjacent to the development site lies between Barton Locks, approximately 500 m

downstream of the site and Mode Wheel Locks, 5 km upstream. Upstream of Barton Locks the

water level in the canal is maintained at 17.37 m AOD and below the locks the water level is

maintained at 12.84 m AOD.

9.21 Other watercourses within the immediate vicinity include Salteye Brook, approximately 550 m to

the north west of the site, which discharges to the Manchester Ship Canal downstream of

Barton Locks, 650 m south west of the site. Salteye Brook forms the lower reach of Worsley

Brook catchment which drains Walkden, Worsley and Swinton.

9.22 Several un-named drains and watercourses are detailed on land to the south of the site, related

to Davyhulme Sewage Works. All flows within these drainage channels are contained and

managed by the works.

Site Drainage

9.23 No previous development of the site is evident from historical mapping and the site walkover

confirmed there to be no existing infrastructure or buildings located within the site boundary.

Surface water runoff currently infiltrates to ground across the majority of the site, or to the

Manchester Ship Canal by overland flow during extreme events. The site appeared to be

generally well drained during the site walkover.

9.24 Service plans from United Utilities detail two pumped rising mains crossing the site from east towest, passing foul water flow to Davyhulme Sewage Treatment Works.

Flood Risk

9.25 As part of the planning process a separate Flood Risk Assessment has been prepared to meet

the requirements set out in PPS25 and is included within Appendix 3.1. Reporting shows the

site to be located within Flood Zone 1, indicating a low risk of flooding. The main risk to the site

is considered to be from extreme rainfall events resulting in shallow overland flow towards the

Manchester Ship Canal. The site is not considered to be at risk from fluvial, tidal or




groundwater sources. Hydraulic modelling of flows within the Manchester Ship Canal has

recently been undertaken, confirming the risk to the site from partial failure of operational

infrastructure on the Canal to be negligible.

Soil

9.26 The soil map of England and Wales (map 3) indicate the site to is overlain by alluvium deposits

of the Alun association that may comprise sands and till over gravels. Mapping of the soil

environment has been supported by recent ground investigation works undertaken to the south

of the site by United Utilities (UU). The overlying soils are classified as having a high leaching

potential.

9.27 Phase 1 reporting for the site makes reference borehole logs obtained from the BGS fromground investigations undertaken on the site in relation to the widening of Barton Bridge. These

borehole logs reflect similar profiles and general characteristics as the UU investigations.

9.28 Findings of these previous site investigations indicate Made ground of an approximate thickness

of 3.5 m. The made ground comprises tarmac, ash, brick fragments, concrete and silty sandy

clay overlying Alluvium drift deposits.

Geology

9.29 Geology at the site has been interpreted from 1:50,000 British Geological Survey (BGS) map

sheet 85 and the result of the previous UU and Barton Bridge site investigations detailed above.

The site is shown to be over alluvium deposits that may comprise flood gravels, till, sand and

gravels, and/or boulder clay.

9.30 Underlying bedrock is Bunter Sandstone over Manchester Marls of the Permo-Triassic Age,

comprising a red/brown medium to coarse gravel, laminated, occasionally cross-bedded, slightly

micaceous sandstone with occasional mudstone and pebble beds. The bedrock is at

approximately 24.0 m below ground level.

Groundwater

9.31 The EA website shows the site to be underlain by a ‘Principal Aquifer’ associated with the

underlying Bunter Sandstone bedrock. Principal Aquifers are defined layers of rock or drift

deposits that have high intergranular and/or fracture permeability, providing a high level of water

storage. Principal Aquifers have the capability to support water supply and/or river base flow on

a strategic scale.

9.32 The EA classification also goes on to define a ‘Secondary A’ aquifer associated with the made

ground and alluvium deposits. An aquifer classed as Secondary A is defined as having




permeable layers capable of supporting water supplies at a local rather than strategic scale, and

in some cases forming an important source of base flow to rivers.

9.33 Previous ground investigation work recorded in the UU report, confirmed the presence of two

groundwater zones. An upper zone associated with the alluvium deposits and a lower zone in

the sandstone. The groundwater beneath the site is not covered by any EA source protection

zoning.

Water Quality

9.34 The quality of water contained in rivers, estuaries, coastal waters and groundwater within the

north west region is defined by a classification system which is in line with the Water Framework

Directive. Surface waters are defined by two separate classifications, ecological and chemical,with the overall classification being the lesser of the two results

9.35 Information from the EA’s website shows the reach of the Manchester Ship Canal adjacent to

the site to be Moderate for current ecological status and Fail for chemical status. Predicted

classification remains the same looking forward to 2015.

9.36 Groundwater is classified as Poor in terms of quantitative quality and Poor (deteriorating) in

terms of chemical quality. Predicted classification remains Poor for both quantitative and

chemical quality looking forward to 2015.

9.37 Visual observations made during the site visit noted good aesthetic water quality within the

Manchester Ship Canal, where flowing water appeared clear and free from litter or debris.

Licensed Abstractions and Discharge Consents

Envirocheck data details 60 no. discharge consents within 1000 m of the site. Of these, 15 no. areshown to be within 500 m of the site, including revoked or superseded consents. The 15 consentscorrespond to 4 actual discharge points, the details of which are summarised in




9.38 Table 9.5.




Table 9.5 Discharge Consents

Operator Discharge Type Status NGR

The TraffordCentre Ltd

Sewage Discharges -Pumping Station

New Consent 375750397050

United UtilitiesWater Plc

Sewage Discharges -Final/Treated Effluent

Consent Under Appeal 375610

397270

Manchester ShipCanal Co Ltd

Sewage Discharges -Final/Treated Effluent

Pre NRA Legislation whereissue date < 01/09/1989

374800

396600

United UtilitiesWater Plc

Sewage Discharges -Storm Tank Overflow

Consent Currently Under Appeal

374960

397150

9.39 There are 3 no. water abstraction licenses detailed within Envirocheck for locations within 1000m of the site. The details of these abstractions are summarised in Table 9.6.

Table 9.6 Abstraction Licenses

Operator Water use Rate Source NGR

Longland Ltd Industrial: CoalWashing

818 m3/day

40,914 m3/year

Surface – Salteye Brook

375750397050

Playgolf (TraffordCentre) Limited

Golf Courses:Spray Irrigation -

Direct

Not supplied Groundwater – Borehole at Old

Park Lane

376340

396630

The TraffordCentre Ltd

Retail: SprayIrrigation - Direct

273 m3/day

18,885 m3/year

Groundwater – Borehole at theTrafford Centre

376470

396680

Water Authority Assets

9.40 Asset plans sourced from United Utilities confirm the presence of two pumped rising mains

crossing the site from east to west, passing foul water flow to Davyhulme Sewage Treatment

Works.

Baseline Sensitivi ty

9.41 There are no watercourses evident within the site boundary, with the closest watercourse being

the Manchester Ship Canal, located adjacent the northern site boundary. The Canal acts as the

main drain for the Greater Manchester region, receiving flows from several upstream river

catchments. Water quality of the Canal is classified as Moderate for ecological status and Fail

for chemical status.




9.42 The site is underlain by Made Ground over alluvium deposits comprising sands and till over

gravels. The made ground comprises tarmac, ash, brick fragments, concrete and silty sandy

clay. The Made Ground and alluvium soils are considered to have a high leaching potential.

Bedrock geology comprises Bunter Sandstone over Manchester Marls of the Permo-Triassic

Age.

9.43 A ‘Principal Aquifer’ is designated beneath the site, associated with the underlying Bunter

Sandstone bedrock and a ‘Secondary A’ aquifer associated with the made ground and alluvium

deposits. Groundwater is classified as Poor in terms of quantitative quality and Poor

(deteriorating) in terms of chemical quality. Current site drainage is to ground infiltration,

passing to the upper groundwater zone, with excess surface water flows during extreme rainfall

conditions passing overland to the Manchester Ship Canal.

9.44 Indicative flood mapping provided by the EA shows the Application Boundary to be completely

within Flood Zone 1, indicating a low risk of flooding. The site is not considered to be at risk from

fluvial, tidal or groundwater sources. Recent hydraulic modelling of flows within the Manchester

Ship Canal has confirmed the risk to the site from failure of operational infrastructure on the

Canal to be low.

9.45 There are several consented discharges within 1000 m of the site, with four registered

discharge consents noted within 500 m of the site boundary. The discharge consents relate to

treated effluent, storm-water overflow or pump station overflow from sewage treatment

operations. Three licensed abstractions are noted within 1000 m of the site boundary, onesurface water and two groundwater, relating to industrial use and irrigation respectively.

Assessment of Impacts and Mi tigat ion Measures

9.46 This section describes the potential effects of the proposal based upon an assessment of the

activities which will occur during the construction, operational and decommissioning phases of

the proposal, prior to the inclusion of mitigation measures. The purpose of the following

assessment is to identify key areas of concern where specific mitigation and management

issues will be required.

9.47 Throughout construction, operation and decommissioning, there will be embedded mitigation

within the design processes and mitigation measures deemed necessary due to the

identification of a ‘significant’ effect upon the environment.

9.48 An assessment of these potential effects determines the requirement and scope of mitigation

measures to be either embedded within the design or to be incorporated owing to a significant

effect. These are discussed in detail below. This section, therefore, reflects the effects prior to

any mitigation being implemented. A post mitigation assessment outlines the resultant effects

following the implementation of all mitigation, referred to as ‘residual effects’.



BREP Environmental Statement – Volume 1

Table 9.7 Potential Impacts during the Construction and Decommiss ioning Phase

Activi ty Potential impact Sensit iv ity Magnitude Signi ficance NeeMit

Site clearanceand enablingworks

Mobilisation of contaminants or sediment laden runoff which couldenter the Manchester Ship Canal

Low Medium Moderate 9

Dewatering of excavations

Discharge of potentiallycontaminated groundwater or sediment laden runoff to theManchester Ship Canal followingdewatering or excavation


Disruption to upper groundwater zone (Secondary aquifer) due todewatering of excavations

Low Low Low 9

Construction of buildings,foundations,hardstandingand roads withinthe site

Spillages of concrete duringfoundation and hardstandingformation could enter Manchester Ship Canal


Changes in surface water runoff patterns which could result in aflooding risk

Low Negligible Negligible x

Generation of turbid runoff whichcould enter the Manchester ShipCanal





Activi ty Potential impact Sensit iv ity Magnitude Signi ficance NeeMit

Creation of preferential pathways for migration of contaminated materials

into the Alluvium and/or Bunter Sandstone during piling

High Low High 9

Trafficmovement:Creation of contaminated

fugitive dust

Exposure of construction workers tocontaminated dust.

Low Low Low 9

Damping downof dust

Generation of slurry impacting cleansoil and the Manchester Ship Canal

Low Low Low 9

Site activitiessuch as thestorage of fueland oil

Spillages and leakages of oil, fuel,and other potentially pollutingsubstances e.g. oil spills, could enter adjacent Canal or impactgroundwater





Table 9.8 Potential Impacts During the Operational Phase

Activi ty Potential Impact Sensit iv ity Magnitude Signi ficance NeeMit

Presence of buildings,hardstandingand roads withinthe site

Changes in surface water runoff patterns which could change floodingrisk


Reduction in infiltration ratesaffecting groundwater recharge


Uncontrolled discharges could resultin the input of sediments, litter andoils


Abstractionwater for theplant process

Reduced flow to surface water or groundwater supplies


Discharge of surface water

Increase in flood risk to the Canal Low Negligible Negligible x

Site activities Spillages and leakages of oil, fuel,and other potentially pollutingsubstances e.g. concrete, could enter adjacent watercourses or impactgroundwater





Mitigation Measures

9.49 This section outlines the proposed mitigation measures designed to address thepotential impacts detailed in Table 9.7 and Table 9.8. The mitigation measures

described below are divided into those relating to construction, operation and

decommissioning activities

Potential Preparation, Earthworks and Construction Phase

Site Preparation

9.50 A suitably targeted site investigation will determine the extent of any contamination

within the Made Ground and Alluvium. This will also include testing of the

groundwater table beneath the site and surface water sampling.

9.51 Depending on the findings of the site investigations, the groundwater and some of

the Made Ground and drift deposits may require treatment and/or removal as part

of the construction works. Risk assessments and a remediation strategy will

outline the required treatment, if any and re-use of materials. Detailed method

statements will be required from the Contractor on how materials are to be dealt

with. A Site Waste Management Plan (SWMP) will be formulated detailing how all

materials generated at the site both in ground and for the development, will be

dealt with.

Foundation Formation

9.52 It is likely that aspects of the proposal will require piled foundations. Dependent on

further site investigations, these foundations have the potential to extend down to

the sandstone bedrock and during any proposed piling works there is the potential

for contaminants to migrate to the underlying Principal aquifer and the upper

groundwater zone within the alluvium. Piling works will be undertaken with

reference to the EA’s guidance. A Foundation Works Risk Assessment will be

undertaken prior to any works in accordance with the foregoing EA guidance to

assess the piling method being undertaken; the likelihood of piling through

contaminated ground; and the overall risk to groundwater quality in the aquifers. If

risks are determined to be present, mitigation measures will be put in place as

appropriate.

9.53 Building foundations, plinths and hardstanding will be formed through the pouring

of concrete. Concrete is highly alkaline and corrosive and can have a detrimental




impact on watercourses. Without controls on this process, concrete spillages could

potentially result in pollutants coming into contact with surface water features. If

concrete is to be batched on site a designated laydown area will be identified. The

appropriate classification of concrete for the environmental conditions will be used

in order to avoid the potential for leaching.

Dewatering of excavations

9.54 It is likely that groundwater from the upper Secondary aquifer will be encountered

while forming foundation excavations and during site earthworks. If and when

groundwater is encountered, water will be pumped out, temporarily stored and

tested, before discharging via an agreed discharge consent.

Site activities

9.55 Site activities may result in spills and leaks of materials used in the construction

process, including fuel, oil and lubricants. A Construction Environmental

Management Plan (CEMP) will be developed in consultation with the EA and the

site contractor. This will include measures for avoiding the likelihood of spills and

leaks and an auditing programme which will verify environmental performance on

the site during construction.

9.56 Best working practices, based on EA PPG and CIRIA guidance, will be adopted

throughout the construction works to protect the water environment. The storage of

oil, fuel and other substances will be within the designated construction area. Oil

and fuel will be within impervious storage bunds with 110% capacity, so that any

spillages or leaks are contained.

9.57 Construction machinery will be checked regularly to prevent oil leakages. Any

maintenance required would occur over hard-standing or on a suitable

impermeable ground cover. Refuelling will be limited to a designated area, on an

impermeable surface, away from any drainage infrastructure. Spill kits will beavailable on site at all times. Any spills will be cleaned up as soon as possible,

according to the spill response plan in the CEMP.

9.58 A temporary wheel washing facility will be installed to prevent transfer of soil onto

public roads. All water within the wheel wash facility will be recycled, and no water

will be discharged off site, unless via some form of treatment and with EA

agreement.




Operational Phase

9.59 This section describes the mitigation measures that will be incorporated into the

development during the operational phase to reduce effects on the water

environment and soil. The proposal has the potential to affect the water and soil

environment throughout its operation; therefore, a long term strategy for

sustainable mitigation has been developed.

Surface Water Drainage

9.60 The site will be occupied by buildings, access roads, hard-standing and process

infrastructure. To minimise the impact of drainage, surface water runoff from the

site will be managed by a new site drainage system, which will seek to include theuse of Sustainable Drainage Systems (SUDS) and restrict peak site runoff to

greenfield runoff rates of 4.50 l/s/ha, subject to consent agreement with the

Manchester Ship Canal Company. SUDS will be achieved through the

incorporation of grassed swales at ground level to provide storage. The grassed

swale feature within the landscape buffer and is detailed within the flood risk

assessment (FRA) in Appendix 9.1.

9.61 The new drainage system will be designed to function without surcharge during

normal operations and to accommodate the on-site runoff from extreme rainfall

events. Detail design of the system will make allowance for an additional 20% on

peak rainfall intensity to simulate the effect of climate change in accordance with

Appendix B of PPS25.

Abstraction water for the process

9.62 The preferred mechanism for cooling the plant will be either an air cooled or hybrid

evaporative cooling system, subject to detailed design and procurement.

Assuming a hybrid evaporative cooling system is used, as this would place the

largest demand on the water environment, the system would be anticipated torequire 80 m

3/hr (22.2 l/s) of water from the Manchester Ship Canal. To provide a

factor of safety for the site and the potential technology the applicant will look to

secure consent for an evaporative cooling abstraction rate set at 30 l/s.

Process and Domestic Effluent

9.63 The hybrid evaporative cooling process, if adopted, will blow down a proportion of

water under normal operation. The estimated volume is approximately 15 m3/hr

(4.2 l/s). This blow down water will discharge to foul sewer on the site. To provide




a factor of safety for the site and the potential technology the applicant will look to

secure agreement for a discharge rate set at 7.5 l/s. In the event of a fire, fire-

fighting water would also be discharged.

9.64 Domestic sewage is to be discharged into the existing mains system maintained by

United Utilities, however due to the levels of the site and the associated invert

levels of the existing foul system in Trafford Way it will be necessary to provide a

foul water pumping station within the development with a rising main following the

route of the access road into the site. As with all foul pumping stations, an

emergency overflow must be provided should the systems and controlling

telemetry fail. Consent for this emergency overflow will be sought by the

developer.

Site Activities

9.65 All areas where potentially polluting substances will be stored and used, will be in

areas with appropriate bunding to industry standards. Bunds will provide 110% of

stored volume and will be made from impervious materials. In the rare event of an

oil spill into a bund the oil will be pumped out to a road tanker for re-use or

disposed of in an environmentally acceptable manner.

9.66 The site will be operated in accordance with best working practices and measures

to protect the water environment will be in accordance with those set out within EA

PPG notes.

Decommissioning Phase

9.67 Decommissioning of the proposal will be subject to a Decommissioning Method

Statement (DMS) which will be agreed with the Local Authority and EA prior to

decommissioning activity. Similar precautionary measures to those proposed for

the construction phase will be implemented as necessary, in accordance with best

practice at the time.

Site Activities

9.68 As with construction operations, site activities may result in a risk of spills and

leaks of polluting substances used during decommissioning, including fuels and

lubricants. A DMS will be developed in consultation with the EA and the site

contractor. This will include measures for avoiding the likelihood of spills and leaks

and an auditing programme which will verify environmental performance on the site

during construction and demolition. As site activities during the decommissioning




will be the same as those encountered during construction, mitigation measures

detailed above will cover such activities.

Monitoring and Follow Up

9.69 A CEMP for control and management of potential risks at the site will be developed

and implemented by the Principal Contractor for the preparatory and construction

phases of the development. The CEMP will incorporate the mitigation measures

recommended above to reduce the significance, and where possible, eliminate the

identified impacts.

9.70 The CEMP will be a live document setting out the management system to be

adopted on site. Detailed risk assessment for all operations from which a safesystem of work shall be developed. The Principal Contractor will be required to

monitor this process and develop assessments and working methods appropriate

to changes in work activities.

Identification of Residual Effects

9.71 This assessment describes the likely residual effects following the incorporation of

mitigation measures. Therefore, it describes the real predicted effects that could

occur as a result of the development.

Construction Phase

Effects on Surface Water

9.72 The recommended controls will prevent surface water runoff or entrained sediment

entering the Manchester Ship Canal and avoid any adverse impacts or effects.

Mitigation controls outlined for the pouring of concrete for forming foundations is

predicted to prevent the likelihood of there being effects on surface water.

9.73 Other activities on-site, such as the storage of oil and fuel and refuelling will also

be subject to controls based on best practice guidance. Whilst best practice

measures will be in place, there is inevitably the potential for accidental incidents to

occur. Response to such events will be managed through the CEMP, such that all

spills will be contained.




Effects on Groundwater

9.74 A method statement for piling works will control the potential to impact the

underlying aquifer. With these plans in place it is not expected that the underlying

aquifer would be at significant risk from the proposals.

9.75 Mitigation measures outlined for the control of site activities are also expected to

control any potential releases to groundwater, and potential risks to groundwater

during construction are considered to be low.

9.76 The EA document Piling and Penetrative Ground Improvement Methods on Land

Affected by contamination: Guidance on Pollution Prevention (2001) describes

potential risks associated with concrete migration into groundwater. This

document considers that migration of concrete during piling would only occur in

highly fractured and fast flowing groundwater environments. In addition, the

potential for migration of concrete in such groundwater conditions would only occur

for a couple of minutes until it begins to set. Such conditions are not anticipated

beneath the Renewable Energy Plant. Therefore, there are no predicted effects

from concrete in groundwater.

9.77 Any groundwater encountered during the excavation of foundations which could be

contaminated will be treated and discharged under a consent to discharge.

Therefore, no residual effect is predicted associated with contaminated shallow

groundwater.

9.78 As with surface water, there is the potential for accidental spills of oil or fuel which

could enter groundwater. Measures and protocols are in place to avoid the

likelihood of such events occurring. However, there will always be the potential for

accidental incidents. Spill response measures and the nature of the underlying

shallow strata will reduce the likelihood of pollutants becoming mobile within

groundwater.

Effects on Soils

9.79 There may be the need for some soil and made ground excavations for the

proposal during construction. These excavations will be carried out in accordance

with DEFRA guidelines to minimise the effects of the proposals.




Operational Phase


9.80 Very few residual effects are predicted once the mitigation outlined is in place. The

surface water drainage system will control and treat any spills. Surface water

runoff rates will not impact on flows within the Manchester Ship Canal and the

proposed drainage strategy will seek to sustainably manage surface water runoff.

All water discharges from the development will operate within consent to discharge

requirements and will be treated.

9.81 Surface water abstraction from the Manchester Ship Canal for process cooling will

be managed through a abstraction licence. This process will ensure that thevolume and rate of required abstraction is sustainable in terms of flow within the

canal.


9.82 No effects are predicted on groundwater during the operation of the Renewable

Energy Plant.

Effects on Soils

9.83 No effects are predicted on soil during the operation of the Renewable Energy

Plant.

Decommissioning Phase


9.84 Similar mitigation controls will be implemented to control effects on surface water

during decommissioning as previously described for the construction phase. The

drainage system may be retained on site following decommissioning dependent on

future land use.

9.85 The abstraction and discharge of the cooling water will cease resulting in a very

slight increase in flow returning to existing flow levels within the Canal.





9.86 Mitigation measures outlined for the control of site activities is expected to prevent

potential releases to groundwater.

Effects on Soils

9.87 No effects are predicted upon soils during the decommissioning of the Renewable

Energy Plant. Site drainage and any re-vegetation will be monitored where

applicable to ensure successful restoration.

Evaluation of Residual Effects

9.88 It is normal practice within environmental assessment to evaluate the significance

of residual risks on the water and soil environment. The evaluation is based on the

methodologies described earlier in this chapter. The results of the evaluation are

illustrated in Table 9.9.



BREP Environmental Statement - Volume 1

Table 9.9 Assessment of Residual Effects

Effect Type of Effect

Probabilityof Effect

Sensitivity of Impact

Magnitudeof Effect

Effect SignificanRanking Rati

Construction

Effects on surface water features

accidental spillages

-ve Unlikely Low Low Low The oil trmanthro

Effects on groundwater features

foundation formation andpiling

accidental spillages

-ve Unlikely Medium Low Moderate Bestauguguidimpl

The conftarg

Effects on soils -ve Certain Low Low Low Any in acguid

Besimplthe p

Operation

Effects on surface water and groundwater features

accidental spillages of fuel/lubricant or other polluting substance

-ve Unlikely Low Low Low Bestimpl



BREP Environmental Statement - Volume 1

EffectType of Effect

Probabilityof Effect

Sensitivity of Impact

Magnitudeof Effect

Effect Significan

Ranking Rati

Effects on soils -ve Unlikely Low Negligible Negligible Unddurin

Decommissioning

Effects on surface water and groundwater features

accidental spillages of fuel/lubricant or other polluting substance

-ve Unlikely Low Low Low Bestimpl

Effects on soils +ve Certain Low Low Low ResMad

outcconsOvesoil.

Key Type Probability Sensitivity Magnitude Significance

-ve =Negative

+ve =positive

Certain

Likely

Unlikely

High

Medium

Low

Negligible

High

Medium

Low

Negligible

Very High

High

Moderate

Low

Negligible




Cumulative Effects

9.89 Proposed mitigation and resulting residual risk will ensure that any impacts on thesoil and water environment will be small and will be localised to the site.

Information with respect to other committed development schemes in the vicinity of

the site has been sourced from Trafford and Salford City Council websites.

Several schemes have recently been approved and/or under construction which

are of a scale that requires consideration in terms of cumulative impact.

9.90 Davyhulme Sewage Treatment Works lies immediately to the south of the Site.

Two schemes have been recently approved for the open ground between the site

and the existing treatment works facilities, the first is for expansion of the existing

treatment works to include an advanced sludge treatment facility which is now

under construction (Trafford Council ref. H/70123) and the second is a smaller

development close to the Barton Bridge for exploration, testing and extraction of

coal bed methane (Trafford Council ref. 74681/FULL/2010)

9.91 Whilst it is understood that there is a risk of contamination to groundwater beneath

the site, the mitigation techniques outlined for the development, including

adherence to Environment Agency Pollution Prevention Guidance and guidance on

piling, will serve to minimise potential cumulative effects. No significant cumulative

impacts are anticipated from the proposed developments to the south of the site.

9.92 To the north of the site, within Salford City Council, there are currently two

approved applications relating to development of the City of Salford Stadium on the

opposite bank of the Manchester Ship Canal. One application relates to

remediation works for the Stadium development (Salford City Council ref.

09/46028/OUT) which is under construction and a subsequent application relates

to the Stadium development (Salford City Council ref. 10/58995/HYBEIA). In terms

of assessing for cumulative impacts from this development, the only effects to be

taken into consideration are potential effects on the Principal aquifer as the

Manchester Ship Canal prevents flow within the Secondary aquifer between theStadium site and the development. Mitigation measures outlined within this report

reflect the measures recommended for the Stadium development and require piling

to be undertaken in accordance with Environment Agency guidance to protect the

underlying aquifer. There is therefore no significant cumulative effect anticipated.

9.93 A further approved application relates to a new freight interchange occupying land

to the north of the site, between the Manchester Ship Canal and Liverpool Road

(Salford City Council ref. 03/47344/EIAHYB). It is considered that the construction

and operational activities associated with this facility may have the potential to




impact local surface water features only, with no impact anticipated on

groundwater features. No significant cumulative impact is anticipated relating to

this development.

Summary and Conclusions

9.94 This chapter describes the potential effects on surface water, groundwater and soil

from the construction, operation and decommissioning phases of the Renewable

Energy Plant.

9.95 The development is located alongside the Manchester Ship Canal, to the north of

Davyhulme Sewage Treatment Works. In accordance with PPS25 a flood risk

assessment has assessed the site to be within Flood Zone 1. The site is notconsidered to be at risk from fluvial, tidal or groundwater sources. A specifically

designed drainage system across the site will provide sustainable management of

runoff from the site into the Manchester Ship Canal.

9.96 The potential effects on surface water, groundwater and soil from the proposal are

considered as being insignificant with impacts being identified as being low and

negligible. A potential moderate impact has been identified in relation to risk

associated with the underlying Principal aquifer; however, appropriate working

methods based on best practice will be incorporated into a Construction

Environmental Management Plan which will ensure that risk to the aquifer is

minimised and no significant adverse residual effects to surface water through

sediment input or site activities.

9.97 The development will require a piled foundation solution, whereby piles are

anticipated to reach solid bedrock in the form of the underlying Bunter sandstone.

A foundation risk assessment and method statement will be needed to ensure that

both the Principal and Secondary aquifers identified beneath the site remain

protected. This strategy will be developed and agreed with the EA.

9.98 A suitably targeted site investigation will also be undertaken to establish fully the

site conditions and to assist the detail design of environmental protection

measures.



References

EQS - Environmental Quality Standard, as laid down in relevant EU Directives andnational legislation

DWS – Drinking Water Standards

FEH (Flood Estimation Handbook) CD-ROM produce by the CEH (Centre for Ecology

and Hydrology, 1999)

Preliminary soil and groundwater appraisal and qualitative risk assessment reporting

prepared for the proposed Advanced Sludge Treatment Plant

Phase 1 Engineering and Environmental Assessment, Proposed Biomass Fuelled Power

Generation Plant Adjacent Barton Bridge Manchester

76153-Environmental+Statement+Chapter+9.pdf

Documents