Post on 14-Apr-2018
transcript
7/27/2019 76153-Environmental+Statement+Chapter+9.pdf
http://slidepdf.com/reader/full/76153-environmentalstatementchapter9pdf 1/30
155
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
7/27/2019 76153-Environmental+Statement+Chapter+9.pdf
http://slidepdf.com/reader/full/76153-environmentalstatementchapter9pdf 2/30
156
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)
7/27/2019 76153-Environmental+Statement+Chapter+9.pdf
http://slidepdf.com/reader/full/76153-environmentalstatementchapter9pdf 3/30
157
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;
7/27/2019 76153-Environmental+Statement+Chapter+9.pdf
http://slidepdf.com/reader/full/76153-environmentalstatementchapter9pdf 4/30
158
• 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:
7/27/2019 76153-Environmental+Statement+Chapter+9.pdf
http://slidepdf.com/reader/full/76153-environmentalstatementchapter9pdf 5/30
159
• 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.
7/27/2019 76153-Environmental+Statement+Chapter+9.pdf
http://slidepdf.com/reader/full/76153-environmentalstatementchapter9pdf 6/30
7/27/2019 76153-Environmental+Statement+Chapter+9.pdf
http://slidepdf.com/reader/full/76153-environmentalstatementchapter9pdf 7/30
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:
7/27/2019 76153-Environmental+Statement+Chapter+9.pdf
http://slidepdf.com/reader/full/76153-environmentalstatementchapter9pdf 8/30
BREP Environmental Statement – Volume 1 162
• 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.
7/27/2019 76153-Environmental+Statement+Chapter+9.pdf
http://slidepdf.com/reader/full/76153-environmentalstatementchapter9pdf 9/30
BREP Environmental Statement – Volume 1 163
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
7/27/2019 76153-Environmental+Statement+Chapter+9.pdf
http://slidepdf.com/reader/full/76153-environmentalstatementchapter9pdf 10/30
BREP Environmental Statement – Volume 1 164
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
7/27/2019 76153-Environmental+Statement+Chapter+9.pdf
http://slidepdf.com/reader/full/76153-environmentalstatementchapter9pdf 11/30
BREP Environmental Statement – Volume 1 165
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
7/27/2019 76153-Environmental+Statement+Chapter+9.pdf
http://slidepdf.com/reader/full/76153-environmentalstatementchapter9pdf 12/30
BREP Environmental Statement – Volume 1 166
9.38 Table 9.5.
7/27/2019 76153-Environmental+Statement+Chapter+9.pdf
http://slidepdf.com/reader/full/76153-environmentalstatementchapter9pdf 13/30
BREP Environmental Statement – Volume 1 167
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.
7/27/2019 76153-Environmental+Statement+Chapter+9.pdf
http://slidepdf.com/reader/full/76153-environmentalstatementchapter9pdf 14/30
BREP Environmental Statement – Volume 1 168
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’.
7/27/2019 76153-Environmental+Statement+Chapter+9.pdf
http://slidepdf.com/reader/full/76153-environmentalstatementchapter9pdf 15/30
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
Low Medium Moderate 9
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
Low Medium Moderate 9
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
Low Medium Moderate 9
7/27/2019 76153-Environmental+Statement+Chapter+9.pdf
http://slidepdf.com/reader/full/76153-environmentalstatementchapter9pdf 16/30
BREP Environmental Statement – Volume 1
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
Low Medium Moderate 9
7/27/2019 76153-Environmental+Statement+Chapter+9.pdf
http://slidepdf.com/reader/full/76153-environmentalstatementchapter9pdf 17/30
BREP Environmental Statement – Volume 1
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
Low Negligible Negligible x
Reduction in infiltration ratesaffecting groundwater recharge
Low Medium Moderate 9
Uncontrolled discharges could resultin the input of sediments, litter andoils
Low Medium Moderate 9
Abstractionwater for theplant process
Reduced flow to surface water or groundwater supplies
Low Negligible Negligible x
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
Low Medium Moderate 9
7/27/2019 76153-Environmental+Statement+Chapter+9.pdf
http://slidepdf.com/reader/full/76153-environmentalstatementchapter9pdf 18/30
BREP Environmental Statement – Volume 1 172
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
7/27/2019 76153-Environmental+Statement+Chapter+9.pdf
http://slidepdf.com/reader/full/76153-environmentalstatementchapter9pdf 19/30
BREP Environmental Statement – Volume 1 173
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.
7/27/2019 76153-Environmental+Statement+Chapter+9.pdf
http://slidepdf.com/reader/full/76153-environmentalstatementchapter9pdf 20/30
BREP Environmental Statement – Volume 1 174
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
7/27/2019 76153-Environmental+Statement+Chapter+9.pdf
http://slidepdf.com/reader/full/76153-environmentalstatementchapter9pdf 21/30
BREP Environmental Statement – Volume 1 175
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
7/27/2019 76153-Environmental+Statement+Chapter+9.pdf
http://slidepdf.com/reader/full/76153-environmentalstatementchapter9pdf 22/30
BREP Environmental Statement – Volume 1 176
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.
7/27/2019 76153-Environmental+Statement+Chapter+9.pdf
http://slidepdf.com/reader/full/76153-environmentalstatementchapter9pdf 23/30
BREP Environmental Statement – Volume 1 177
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.
7/27/2019 76153-Environmental+Statement+Chapter+9.pdf
http://slidepdf.com/reader/full/76153-environmentalstatementchapter9pdf 24/30
BREP Environmental Statement – Volume 1 178
Operational Phase
Effects on Surface Water
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.
Effects on Groundwater
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
Effects on Surface Water
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.
7/27/2019 76153-Environmental+Statement+Chapter+9.pdf
http://slidepdf.com/reader/full/76153-environmentalstatementchapter9pdf 25/30
BREP Environmental Statement – Volume 1 179
Effects on Groundwater
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.
7/27/2019 76153-Environmental+Statement+Chapter+9.pdf
http://slidepdf.com/reader/full/76153-environmentalstatementchapter9pdf 26/30
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
7/27/2019 76153-Environmental+Statement+Chapter+9.pdf
http://slidepdf.com/reader/full/76153-environmentalstatementchapter9pdf 27/30
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
7/27/2019 76153-Environmental+Statement+Chapter+9.pdf
http://slidepdf.com/reader/full/76153-environmentalstatementchapter9pdf 28/30
BREP Environmental Statement – Volume 1 180
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
7/27/2019 76153-Environmental+Statement+Chapter+9.pdf
http://slidepdf.com/reader/full/76153-environmentalstatementchapter9pdf 29/30
BREP Environmental Statement – Volume 1 181
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.
7/27/2019 76153-Environmental+Statement+Chapter+9.pdf
http://slidepdf.com/reader/full/76153-environmentalstatementchapter9pdf 30/30
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