8 GEOLOGY, HYDROLOGY AND HYDROGEOLOGYBest Practice Guide for Proposed Electricity Generation Developments’ (2006). There is no relevant English guidance for peat survey, assessment

Gorpley Wind Farm Chapter 8 Environmental Statement Geology, Hydrology and Hydrogeology

Kelda Water Services Arcus Renewable Energy Consulting Ltd October 2012 Page 8-1

8 GEOLOGY, HYDROLOGY AND HYDROGEOLOGY 8.1 INTRODUCTION

This Chapter of the Environmental Statement (ES) assesses the hydrological and hydrogeological effects of the Development during construction, operation and decommissioning. Reference is made to Chapter 6: Ecology of this ES where appropriate.

This Chapter contains the following sections:

• Assessment Methodology and Significance Criteria – a description of the methods used in baseline surveys and in the assessment of the significance of effects;

• Baseline Description - a description of the hydrology and hydrogeology of the Development based on the results of surveys, desk information and consultations, and a summary of any information required for the assessment that could not be obtained;

• Assessment of Potential Effects - identifying the ways in which hydrological and hydrogeological resources could be affected by the Development, including a summary of the measures taken during design of the Development to minimise hydrological and hydrogeological effects;

• Mitigation measures - a description of measures recommended to off-set potential negative effects;

• Residual effects - a summary of the significance of the effects of the Development, after mitigation measures have been implemented;

• Cumulative effects – identifying the potential for effects of the Development to combine with those from other developments to affect hydrological and hydrogeological resources; and

• Statement of Significance.

This Chapter is supported by the following Figures (Volume II: Figures of this ES) and Technical Appendices (Volume III: Technical Appendices of this ES):

• Figure 8.1, Surface Watercourses and Catchments; • Figure 8.2, Solid Geology; • Figure 8.3, Superficial Geology; • Technical Appendix A8.1, Flood Risk Assessment; • Technical Appendix A8.2, Draft Water, Construction and Environmental

Management Plan (WCEMP); and • Technical Appendix A8.3, Peat Slide Risk Assessment (SLR Consulting Ltd).

8.2 ASSESSMENT METHODOLOGY AND SIGNIFICANCE CRITERIA

8.2.1 Assessment Methodology This assessment has involved the following elements, further details of which are provided in the following sections:

• Consultation with relevant statutory and non-statutory bodies; • Desk study, including review of available maps and published information; • Site walkover; • Evaluation of potential effects; • Evaluation of the significance of these effects; and • Identification of measures to avoid and mitigate potential effects.

8.2.2 Guidance The assessment has been undertaken in line with the following policy and guidance:

Chapter 8 Gorpley Wind Farm Geology, Hydrology and Hydrogeology Environmental Statement

Arcus Renewable Energy Consulting Ltd Kelda Water Services Page 8-2 October 2012

• Water Framework Directive (2000/60/EC)1

• National Planning Policy Framework (NPPF), paragraphs 100 to 108

. The Water Framework Directive (WFD) establishes a framework for the protection, improvement and sustainable use of all water environments;

2

• ‘Investigating the impacts of wind farm development on peatlands in England (NECR032)’ (2010)

. This states that for development comprising one hectare or above, the vulnerability to flooding, or the potential to add to flooding elsewhere should be assessed in a Flood Risk Assessment (FRA);

3

• The Scottish Government Guidance: ‘Peat Landslide Hazard and Risk Assessments – Best Practice Guide for Proposed Electricity Generation Developments’ (2006). There is no relevant English guidance for peat survey, assessment or wind farm development on peat lands. Scottish guidance is not necessarily required in England, however it represents a tried and tested methodology for assessing peat slide risk;

. Natural England commissioned this study to develop a set of assessment criteria against which a development proposal can be tested to determine the scale of impact and enable an appropriate response to the EIA.

• The Construction Industry Research and Information Association (CIRIA) Environmental Good Practice on Site (C692) (2010)4

• CIRIA Control of Water Pollution from Construction Sites (C532) (2001)

. C692 provides guidance on how to avoid causing environmental damage when on a construction site; and

5

8.2.3 Consultation

. C532 provides guidance on how to plan and manage construction projects to control water pollution.

Information has been provided by a range of organisations during the assessment, and this is summarised in Table 8.1.

Table 8.1 Consultation Responses Consultee Key Points in Response Action Taken

National River Flow Archive

Information provided on meteorological conditions and regional climatic averages.

The information was used to inform this assessment.

Environment Agency (EA)

Provided information relating flooding records. Scoping response: • As the site area is over 1 hectare (ha)

in size any planning application for this development will require a Flood Risk Assessment (FRA).

• The prior written consent of the Environment Agency is required for any proposed works or structures in, under, over or within 8 metres of the top of the bank of a 'Main River', or within 8 metres of any flood defence.

A Flood Risk Assessment (FRA) is provided as Technical Appendix A8.1. No turbines are within 8 m of watercourses or hydrological resources.

1 European Parliament (2000). “Directive 2000/60/EC of the European Parliament and of the Council establishing a framework for the Community action in the field of water policy” (“The Water Framework Directive”). [online] Available at: http://ec.europa.eu/environment/water/water-framework/index_en.html [Accessed 11/09/2012]. 2 Department for Communities and Local Government (DCLG) (2012). “National Planning Policy Framework - 10. Meeting the challenge of climate change, flooding and coastal change” [online] Available at: http://www.communities.gov.uk/documents/planningandbuilding/pdf/2116950.pdf [Accessed 04/04/2012]. 3 Natural England Investigating the impacts of windfarm development on peatlands in England (NECR032)’ (2010) [online] Available at: http://publications.naturalengland.org.uk/publication/43010 [Accessed 10/10/2012]. 4 CIRIA (2010). “Environmental Good Practice On Site”. C692. [online] Available at: http://www.ciria.org/acatalog/c650.pdf [Accessed 11/06/2012]. 5 CIRIA (2001). “Control of Water Pollution from Construction Sites”. [online] Available at: http://www.ciria.org [Accessed 11/06/2012].



Consultee Key Points in Response Action Taken

• There should be no increase in surface water runoff from the new development.

SuDS measures, proposed as part of the FRA, will ensure that surface water run-off will be managed.

Yorkshire Water Provided information on waters supply pipes on the Development site and requested a 3 m stand-off from such pipes.


Natural England The ES should thoroughly assess the impact of the proposals on non-statutory sites, for example Local Wildlife Sites (LoWS), Local Nature Reserves (LNR) and Regionally Important Geological and Geomorphological Sites (RIGS).

RIGS data was requested from the West Yorkshire Geology Trust. The information was used to inform this assessment.

Calderdale Metropolitan Borough Council (CMBC)

We would ask that within the EIA that risks of impact to private water supplies in Calderdale are fully assessed. Provided information on private water supplies.

Private water supplies are considered within Section 8.4 of this Chapter. The information was used to inform this assessment.

The British Geological Survey

Provided details on solid and drift geology, borehole logs and groundwater.


8.2.4 Desk Study The desk study collated existing data to form an understanding of the hydrology and hydrogeology of the Development.

The desk study included:

• Identification of catchments, watercourses, springs and water features; • Collation of data provided through consultations; • Collation of flood plain information and water quality data; and • Compilation of soils, geological and hydrogeological information.

Reference was made to the following sources of information:

• The British Geological Survey (BGS) Digital Mapping; • Hydrogeological Map of England and Wales 1:625,000, 1977; • The Ordnance Survey (OS) 1:50,000 Landranger Map (Sheet 103); and • OS 1:10,000 digital mapping.

The Hydrology core study area (the area within the Development Site Boundary) and wider study area of 2 kilometres (km) from the proposed turbine locations is shown in Figure 8.1.

8.2.5 Site Walkover A site walkover was conducted on the 10th July 2012 to verify the findings of the desk study and to obtain an understanding of the local topography and hydrological regime. Weather conditions during the site walkover were characterised by persistent and heavy rainfall, whilst the preceding week had persistent rainfall.

8.2.6 Significance Criteria The significance of the potential effects of the Development have been classified by taking into account the sensitivity of receptors and the magnitude of the potential effect on them, combined with the likelihood of an event occurring as defined in Table 8.2.



Table 8.2 Significance Criteria Sensitivity

Magnitude

Low Moderate High

Negligible Negligible Negligible Negligible

Minor Negligible Minor Moderate

Moderate Minor Moderate Moderate / Major

Major Minor Moderate / Major Major

An effect is considered to be significant if assessed as moderate or major in accordance with The Town and Country Planning (Environmental Impact Assessment) Regulations (2011) (the ‘EIA Regulations’)6

The sensitivity of the receptor is defined as its ability to absorb an effect without perceptible change and can be classified as either none (if the receptor is not present within the study area), low, moderate or high. These classifications are dependent on factors such as the quality of the subsurface water within the receptor, its purpose (e.g., whether used for drinking, fisheries, etc.) and existing influences, such as land use.

.

The magnitude of any potential effect is determined by the timing, scale, size and duration of the potential effect resulting from the Development. The magnitude of potential effects is classified as negligible, minor, moderate or major.

These classifications of sensitivity and magnitude are outlined in the following sections.

8.2.6.1 High Sensitivity A ‘high sensitivity’ receptor is classified as either:

• A large, medium or small water body with an Environment Agency (EA) Current Ecological Quality classification of “High” or “Good” and / or a Current Chemical Quality classification of “Good”;

• The hydrological receptor and downstream environment will struggle to attenuate natural fluctuations in hydrochemistry and cannot absorb further changes without fundamentally altering its baseline characteristics / natural processes;

• The hydrological receptor is of high environmental importance or is designated as having national or international importance, such as Special Areas of Conservation (SACs) and Sites of Special Scientific Interest (SSSIs);

• The hydrological receptor is designated for supporting ecological interest; • The hydrological receptor acts as an active floodplain or other flood defence; • The hydrological receptor will support abstractions for public water supply or private

water abstractions for more than 25 people; • Areas containing geological or geomorphological features considered to be of

national importance (e.g., SSSIs); and / or • Local groundwater constitutes a valuable resource because of its high quality and

yield, e.g. Aquifer(s) of local or regional value, statutorily designated nature conservation sites (e.g., SACs and SSSIs) dependent on groundwater.

8.2.6.2 Moderate Sensitivity A ‘moderate sensitivity’ receptor is classified as either:

A large, medium or small water body with an EA Current Ecological Quality classification of “Moderate”;

6 The Town and Country Planning (Environmental Impact Assessment) Regulations (2011).



• The hydrological receptor and downstream environment will have some capacity to attenuate natural fluctuations in hydrochemistry but cannot absorb some changes without fundamentally altering its baseline characteristics / natural processes;

• The hydrological receptor is of regional environmental importance; • The hydrological receptor supports public water supply or private water abstractions

for less than 25 people; • Areas containing geological features of designated regional importance including

Regionally Important Geological Sites (RIGS), considered worthy of protection for their historic or aesthetic importance; and / or

• Aquifer(s) of limited value (less than local importance) as water quality does not allow potable or other quality sensitive uses, e.g. exploitation of local groundwater is not far-reaching or local areas of nature conservation known to be sensitive to groundwater impacts.

8.2.6.3 Low Sensitivity A ‘low sensitivity’ receptor is classified as either:

• A large, medium or small water body with a EA Current Ecological Quality classification of “Poor” or “Bad” and / or a Current Chemical Quality classification of “Fail”;

• The hydrological receptor and downstream environment will have the capacity to attenuate natural fluctuations in hydrochemistry but can absorb some changes without fundamentally altering its baseline characteristics / natural processes;

• The groundwater is of poor quality and / or very low permeability making exploitation of groundwater unfeasible; changes to groundwater are not expected to affect local ecology; or

• Other hydrological receptors not included in the definitions of High or Moderate sensitivity.

8.2.6.4 Major Magnitude A “major” magnitude of change is defined as:

• A short or long term major shift in hydrochemistry or hydrological conditions sufficient to negatively change the ecology of the receptor. This change would equate to a downgrading of an EA Current Ecological Quality classification by two classes e.g., from “High” to “Moderate”;

• A sufficient material increase in the probability of flooding onsite and offsite, adding to the area of land which requires protection by flood prevention measures or affecting the ability of the functional flood plain to attenuate the effects of flooding by storing flood water (in accordance with NPPF paragraphs 100 to 108);

• A major (greater than 50 %) or total loss of a geological receptor or peat habitat site, or where there would be complete severance of a site such as to fundamentally affect the integrity of the site (e.g., blocking hydrological connectivity);

• Major permanent or long term negative change (i.e., degradation of quality) to groundwater quality or a reduction in the available yield;

• Major permanent or long term negative change to geological receptor; and / or • Changes to quality or water table level will cause harm local ecology or will lead to

flooding issue.

8.2.6.5 Moderate Magnitude A “moderate” magnitude of change is defined as:

• A short or long term non-fundamental change to the hydrochemistry or hydrological environment, resulting in a change in ecological status. This change would equate to a downgrading of an EA Current Ecological Quality classification by one class e.g., from “Good” to “Moderate”;

• A moderate increase in the probability of flooding onsite and offsite, adding to the area of land which requires protection by flood prevention measures or affecting



the ability of the functional flood plain to attenuate the effects of flooding by storing flood water (in accordance with NPPF paragraphs 100 to 108);

• A loss of part (approximately 15 % to 50 %) of a geological receptor or peat habitat site, major severance, major effects to its integrity as a feature, or disturbance such that the value of the site would be affected, but could still function;

• Changes to the local groundwater regime may slightly affect the use of the receptor;

• The yield of existing supplies may be reduced or quality slightly deteriorated; and / or

• Fundamental degradation of local habitats may occur, resulting in impaired functionality.

8.2.6.6 Minor Magnitude A “minor” magnitude of change is defined as;

• A detectable non-detrimental change to the baseline hydrochemistry or hydrological environment. This change would not reduce the EA Current Ecological Quality classification;

• A marginal increase in the probability of flooding onsite and offsite, adding to the area of land which requires protection by flood prevention measures or affecting the ability of the functional flood plain to attenuate the effects of flooding by storing flood water (in accordance with NPPF paragraphs 100 to 108);

• A detectable but non-material effect on the receptor (up to 15 %) or a moderate effect on its integrity as a feature or where there would be a minor severance or disturbance such that the functionality of the receptor would not be affected; and / or

• Changes to groundwater quality, levels or yields that do not represent a risk to existing baseline conditions or ecology.

8.2.6.7 Negligible Magnitude A “negligible” magnitude of change is defined as;

• No perceptible changes to the baseline hydrochemistry or hydrological environment; • No change to the EA water quality classification; • No increase in the probability of flooding onsite and offsite; and / or • A slight or negligible change from baseline condition of geological resources;

change hardly discernible, approximating to a situation of ‘no change’ in geological condition.

8.2.7 Methodology for Assessment of Significance of Effects Embedded mitigation measures are set out in Section 8.4.1: Development Design Mitigation of this Chapter and within the Draft WCEMP (provided as Technical Appendix A8.2). They comprise good practice methods and works that are established and effective measures to which the Developer will be committed through the development consent. There is sufficient confidence in the effectiveness of the measures set out in the Draft WCEMP for them to be treated as part of the Development for the purposes of this assessment. Accordingly, the assessment of significance of effects of the Development is considered following implementation of the measures in the Draft WCEMP.

The measures discussed in the WCEMP are inherently part of the wind farm development design and should be treated as embedded mitigation. The Arcus hydrology team has provided services for a large number of onshore wind farm developments and have worked closely with statutory agencies such as the Scottish Environmental Protection Agency, the EA and Scottish Natural Heritage to develop appropriate survey and assessment methods.



This approach has withstood legal review on all hydrology EIA work undertaken by Arcus since 2009 and has received positive comments7

Conclusions, therefore, state whether the residual significance will be major, moderate, minor or negligible, once appropriate mitigation (beyond that specified in the Draft WCEMP) has been implemented. This assessment relies on professional judgment to ensure that the effects are appropriately assessed. Residual effects of moderate or major significance are considered significant in terms of the EIA Regulations.

from consultees for proposing appropriate embedded mitigation on a project specific basis.

8.2.8 Methodology for the Assessment of Cumulative Effects A cumulative effect is considered to be an additional effect on hydrological resources arising from the Development in combination with other proposed developments (either under construction, consented but not built or at application stage) likely to affect the hydrological environment. At distances greater than 10 kilometres (km), or in different hydrological and hydrogeological catchments, as defined by GIS mapping or the EA Groundwater Protection Zone Maps, it is considered that schemes are unlikely to contribute to a cumulative hydrological effect due to attenuation and dilution over distance of potentially polluting chemicals.

8.3 BASELINE DESCRIPTION

8.3.1 Topography and Land-use The hydrology core study area (within the Development Site Boundary shown on Figure 8.1) is located on land east of the consented Reaps Moss Wind Farm, approximately 3.2 km southwest of Todmorden, West Yorkshire, to the west of Gorpley Reservoir. The layout of the Development components is shown in Figure 1.2 of this ES.

The 1:50,000 Ordnance Survey Landranger Map (Sheet 103) shows the hydrology core study area to lie on land rising from north/east to south/west from elevations of approximately 250 metres (m) Above Ordnance Datum (AOD; approximately sea level) to over 400 m AOD. Hydrological features, such as Gorpley Reservoir and minor watercourses are present within the core study area. The majority of the land is used for pastoral farming. Habitats are described in detail in Chapter 6: Ecology of this ES.

The wider study area comprises roads, woodland, reservoirs and the village of Walsden, as well as numerous isolated farmsteads.

8.3.2 Hydrology All turbines, crane pads and the construction compound at the Development site lie within the primary catchment of Midgelden Brook, which lies approximately 1 km north of the nearest turbine (T2). Midgelden Brook flows from west to east within the overall catchment of the Rochdale Canal. Midgelden Brook and Rochdale Canal confluence at National Grid Reference (NGR) SD 92900 23025, approximately 3 km downstream of the point which watercourses at the Development site discharge into Midgelden Brook.

Digital terrain modelling shows that Midgelden Brook drains a catchment area of approximately 760 ha, before discharging into the Rochdale Canal.

Both Midgelden Brook and Rochdale Canal have a Current Ecological Quality class of ‘Moderate’ and are not assessed for chemical quality under the EA online “Water Framework Directive - River Basin Management Plans”8

7 SEPA response to Auchencairn wind farm [online] Available at: http://eaccess.dumgal.gov.uk/online-applications/files/AC7616AEB298E20EE2BCF6945F667EB1/11_P_3_0397-SEPA-208651.doc [Accessed 27/08/2012].

. It is acknowledged, however, that Midgelden Brook has historically suffered from the effects of acid mine drainage

8 EA - Water Framework Directive - River Basin Management Plans [online] Available at: http://maps.environment-agency.gov.uk/wiyby/wiybyController?topic=wfd_rivers&layerGroups=default&lang=_e&ep=map&scale=9&x=389500&y=424500#x=390558&y=424500&lg=1,7,8,9,&scale=8 [Accessed 05/10/2012].



(AMD), as the headwaters of the watercourse originate in proximity to Cough Foot and Black Edge on Todmorden Moor. These areas have been exploited for coal extraction and other industrial processes. AMD can occur when spoil heaps and mineral deposits in the underlying geology contain Iron Pyrite and Sulphides which are then exposed to air and water. This leads to oxidation of these minerals and the formation of Iron and acid. The red or ochre colour seen on the river bed of Midgelden Brook is Iron from the reaction described previously.

Observations from the site walkover confirmed the absence of ochre colour within Weather Hill Gulf and the unnamed watercourses within the Development site, suggesting that acid mine water is not present within the near-surface and sub-subsurface water (groundwater) underlying the Development site.

The central and western sections of the Development site are located within the catchment of Weather Hill Gulf, which issues in proximity to Inchfield Moor before draining into Howroyd Clough.

The headwaters of Howroyd Clough issue in proximity to Limers Gate and Counting Hill, in the western section of the Development site. Howroyd Clough discharges into Gorpley Reservoir at 390745, 422850.

No statutory watercourse designations exist within 5 km downstream of the Development.

Plates 8.1 to 8.2 within the WCEMP (in Technical Appendix A8.2) show unnamed tributaries of Midgelden Brook and Weather Hill Gulf.

8.3.3 Site Drainage Several incised watercourses exist across the Development site due to the low hydraulic conductivity soils. The incised watercourses drain from south to north on relatively steep slopes, leading to fast flowing water during heavy precipitation events. Water within agricultural ditches was either stagnant and vegetated or very slow flowing during the site walkover. Several watercourses and incised ditches are observed across the Development site during the site walkover but are not displayed on OS mapping, suggesting a highly modified hydrological regime, which is typical of upland, rectangular drainage networks.

New Development infrastructure is located within the surface and sub-surface water catchments of watercourses which drain into Gorpley Reservoir, which in turn discharges to Midgelden Brook.

The northern construction compound, also to be used during the construction of Reaps Moss wind farm, is located adjacent to the headwaters of Midgelden Brook. The access track to the consented Reaps Moss wind farm, also to be used for the Development, is located within the catchment of Howroyd Clough.

Drainage sub-catchments are shown on Figure 8.1.

8.3.4 Solid Geology The British Geological Survey 1:625,000 and 1:50,000 solid geology data shows the Development site to be underlain by rocks of the Langsettian age Pennine Lower Coal Measures (PLCM). This comprises a sequence of interbedded grey mudstone, siltstone and pale grey sandstone, with marine bands (mudstones containing marine fossils) and coal seams.

The BGS Digital Mapping shows that turbines 1, 4 and 5 are underlain by mudstone, siltstone and sandstone of the Pennine Lower Coal Measures Formation. Turbines 2 and 3 are underlain by a band of sandstone Pennine Lower Coal Measures Formation. The BGS map records indicate a single inferred normal fault crosses the site to the north-east of the proposed turbine locations (striking north-west to south-east with down-throw towards the south-west). The BGS data does not include details on the dip of



the fault and the rock exposure in the area is poor therefore it is not possible to confirm the faults presence or extent below the site area. However, no geological faulting exists within 100 m of a turbine location.

An illustration of solid geology is shown in Figure 8.2.

8.3.5 Superficial Geology BGS Digital Mapping shows that superficial deposits are absent across the majority of the Development, suggesting bedrock is close to the surface. Upland, peaty soils with low hydraulic conductivity were observed in the central section of the Development site during the site walkover. However, diamicton (till – poorly sorted sediment) is likely to be present to variable depths.

An illustration of superficial deposits is shown on Figure 8.3.

Technical Appendix A8.3 (Peat Slide Risk Assessment) sets out the baseline peat environment in more detail. The access track to the consented Reaps Moss wind farm, which has not yet been built but that is proposed for use as part of the Development, is not considered within the peat slide risk assessment in Technical Appendix A8.3. The peat depth along this track is low: for c. 400 m south of the site access junction with Bacup Road (A681), there is no peat. For the remaining distance (c. 1.3 km), the average peat depth is 0.3 m. Further information on this section of track is provided by a report submitted in support of the Reaps Moss Wind Farm application9

“The access to Reaps Moss from the A681 will follow the Limers Track before bearing westwards to reach the proposed site. Excavated track will form the early sections of track until peat is encountered. As the peat becomes deeper and wetter the contractor will evaluate the point at which floating track becomes appropriate, but a floating track will be used in any case where the peat depth is greater than 1m. The transition between excavated track and floating track will be gradual.

. This states that:

The access track is located upon the watershed boundary of the surface water catchment of the main peat body of Reaps Moss. Therefore, no significant movement of water is expected along the track alignment and no material changes are predicted to occur to the main peatland body. However, the provision for drainage through the track will be provided.”

8.3.6 Hydrogeology The Hydrogeological Map of England and Wales (1:625,000 scale) (1977), shows the study area to be underlain by rocks classified as “Yordale Series and Coal Measures... Rhythmic sequences of shales, sandstones, coals and limestones. Some minor fissure flow in sandstones. Mine waters, from Coal Measures, tend to be ferruginous and acid...”

The sandstones and coal measures comprise varying thickness that form an aquifer of variable groundwater potential identified by the EA as “Millstone Grit / Coal Measures”.

The EA Groundwater Vulnerability map10

The EA classifies minor aquifers as groundwater bodies that have low permeability. This largely correlates with site observations and BGS mapping.

defines groundwater underlying the Development as a ‘minor aquifer’ with low vulnerability to pollution. The EA RBMP map shows that the groundwater underlying the Development has a current chemical quality class of “Poor”.

9 Sinclair Knight Mertz (2008). Lancashire Wind Farms: Peat Assessment and Management. 10 EA Groundwater Vulnerability Maps. [online] Available at: http://maps.environment-agency.gov.uk/wiyby/wiybyController?topic=groundwater&layerGroups=default&lang=_e&ep=map&scale=9&x=389764.5833333333&y=423441.66666666674#x=390294&y=423442&lg=2,&scale=7 [Accessed29/09/2012].



Aquifer characteristics of peat and peaty soils are that significant volumes of water are retained in this material. Groundwater may be present in sand and gravel horizons within the diamicton and also in fractures or fault zones of the bedrock deposits. It is also probable that there will be limited groundwater storage and movement at the weathered interface of the diamicton and bedrock.

Shallow groundwater may be present in the river valleys where deposits of sand and gravel will store and allow movement of groundwater. This groundwater is likely to be in hydraulic continuity with the watercourses around the Development site.

Groundwater flow in upland areas typical of much of the application site tends to follow specific flow paths from high ground to adjacent valleys. Springs and seepages occur wherever water-bearing conduits intersect the surface, but their exact location may be hidden by standing or flowing surface water or by peat or other superficial deposits. Several specific flow paths were observed on the northern edge of the semi metalled track along the watershed between Weather Hill Gulf and Hoyle Hey Clough, to the west of the Development site.

8.3.7 Contaminated Land The EA online interactive mapping11

• Former Pipeworks Landfill, directly adjacent to the construction compound for Reaps Moss wind farm. Received inert wastes, such as glass, concrete, bricks, tiles, soil and stones, which remains largely unaltered once buried;

confirms that there is one active landfill site within 1 km of the Development. Holden Gate landfill, approximately 285 m south east of the consented construction compound for Reaps Moss wind farm, is not noted as receiving any specific class of waste. Four historic landfill sites exist within 1 km of the Development:

• Clough Head Quarry Landfill, approximately 205 m north of the site entrance. Received unknown waste and the EA has no records of waste received at the landfill site;

• Slate Pit Hill Landfill, approximately 235 m north of the site entrance. Received inert wastes, such as glass, concrete, bricks, tiles, soil and stones in addition to household waste from dwellings of various types; and

• Saunderclough Works Landfill, approximately 795 m north east of the construction compound for Reaps Moss wind farm. Received inert wastes, such as glass, concrete, bricks, tiles, soil and stones, which remains largely unaltered once buried.

CMBC holds no records of contaminated land within the Development site on its contaminated land register12

8.3.8 Climate

. Given the undeveloped, upland nature of the Development site, it is unlikely that any unknown contaminated land will exist within the turbine envelope or the footprint of the new access track and is not considered further within this Chapter.

The Hydrogeological Map of England and Wales (1:625,000 scale) (1977) shows the Average Annual Rainfall (AAR) to be between 1,015 mm and 1,523 mm. The National River Flow Archive13

11 EA Waste and Landfill Map [online] Available at: http://maps.environment-agency.gov.uk/wiyby/wiybyController?x=389500.0&y=424500.0&topic=waste&ep=map&scale=9&location=Todmorden Moor, Calderdale&lang=_e&layerGroups=default&distance=&textonly=off#x=389765&y=423441&lg=1,2,&scale=9 [Accessed 10/04/2012].

reports regional AAR for Ding Brook at Naden Reservoir

12 Calderdale MBC – contaminated land register [online] Available at: http://www.calderdale.gov.uk/business/pollution/contaminated-land/contaminatedland-register.html [Accessed 10/10/2012]. 13The National River Flow Archive [online] Available at: http://www.ceh.ac.uk/data/nrfa/data/spatialdata.html?69042 [Accessed 26/6/2012].



(approximately 8.5 km southwest of the Development and the closest record to site) as 1,489mm (1961 to 1990).

8.3.9 Hydrological Regime As observed during the site walkover, intact peat and peaty soil deposits tend to have a ‘flashy’ water discharge regime characterised by ‘peaky’ storm responses, large differences between low and high flows and a rapid rise in the hydrograph during storm events.

8.3.10 Designated Hydrological Receptors Two designations which could be influenced by hydrological effects exist within a 5 km radius of the Development site:

• South Pennine Moors SSSI, SAC and SPA, approximately 2.6 km east of turbine 5, is designated for supporting bogs, marshes, water fringed vegetation and fens; and

• Lee Quarry SSSI, approximately 2.8 km southwest of the access track leading to the meteorological mast, is designated for displaying exposures in the Upper Carboniferous Haslingden Flags Formation, a unique development within the Millstone Grit Formation (geological designation).

Both designations are considered to be hydrologically disconnected from the Development as all proposed infrastructure is located on a different geological slope and within separate surface and sub-surface water catchments. Beyond 5 km designations are considered to be hydrologically disconnected from the Development (in terms of surface water effects, as development is proposed in areas that are outside surface water sub-catchments) or are of sufficient distance to remain unaffected by the Development and are not considered further within this Chapter.

8.3.11 Fisheries The desk study indicated that there are no active fisheries within the wider study and Gorpley Reservoir is not a stocked fishery.

No other standing water bodies are within the same catchment as the Development.

As such, fisheries are not considered further within this Chapter.

8.3.12 Water Supplies CMBC has stated that there are five active potable private water supply abstractions within 1 km of the proposed turbine locations:

• Shackleton Farm, approximately 850 m south of turbine 1 – stream abstraction; • Higher Ditches, approximately 775 southeast of turbine 5 – stream and near surface

abstraction from slopes north of the property; • The Bungalow, approximately 775 southeast of turbine 5 - stream and near surface

abstraction from slopes north of the property; • Lower Ditches, approximately 950 southeast of turbine 5 – stream and near surface

abstraction from slopes north of the property; and • Gorpley Bungalow / Keepers Lodge, approximately 800 m northeast of Inchfield

Moor (where the mid-site construction compound is located) – unknown source. Yorkshire Water has confirmed that service pipes lead to this property, suggesting the private water supply is not the primary source of potable water.

Additionally, there is one borehole within 1.5 km which requires assessment: • South Grain Farm, approximately 1.35 km north northwest of the meteorological

mast – borehole abstraction.

Section 8.4 considers the potential effect on the above private water supplies.

Gorpley Reservoir, located approximately 440 m north of the turbine 2, is not used for the abstraction of water for public supply. Gorpley Reservoir has historically been used for the abstraction of water for public supply, but is now used as for storing increased



surface water run-off during times of heavy and prolonged rainfall and to supplement Midgelden Brook and Rochdale Canal during times of low river flow. As such, Gorpley Reservoir is not classed as a potable water supply receptor in this assessment.

Yorkshire Water has confirmed that there are no potable water supply pipes within 250 m of infrastructure at the Development site. There are no reported sewage pipes within the Development site.

8.3.13 Flooding The proposed infrastructure is located at an upland, elevated, sloping site that is not liable to flood. The EA has no records of flooding at the site and the EA Flood Map14

Additionally, the Development infrastructure is outside areas classed as at risk of flooding from reservoirs

shows the Development footprint to be located in an area described as Flood Zone 1 in NPPF. This zone is categorised as being the lowest flood risk and comprises land assessed as having a less than 1 in 1000 (0.1 %) annual probability of river or sea flooding in any year. A Flood Risk Assessment for the Development is provided in Technical Appendix A8.1 and it identifies that on-site and off-site flood risk will not increase as a result of the Development.

15

8.3.14 Information gaps

.

All data considered necessary to identify and assess the potential significant effects resulting from the Development were available and used in the assessment reported in this Chapter, and as such there were not considered to be any information gaps.

8.4 ASSESSMENT OF POTENTIAL EFFECTS The effect of the Development on hydrological receptors has been considered for the construction, operation and decommissioning phases of the Development.

Table 8.3 Sensitivity of Hydrological Receptors to Potential Effects Receptor Potential Effects

considered Sensitivity Comment

Watercourses / drainage ditches

Increased water run-off, erosion and sedimentation, stream flow impediments and pollution as a result of track construction and chemical handling / storage.

Moderate Considered moderate sensitivity as the receptor (overall receiving watercourse –Rochdale Canal via Midgelden Brook) has an EA Current Ecological Quality class of ‘Moderate’ and does not require assessment for Current Chemical Quality. Additionally, no watercourses within 2 km of the Development are designated for supporting freshwater ecological interest. Streams within the Development site do not support abstractions for public water supply.

14 EA Flood Map (Rivers and Sea) [online] http://maps.environment-agency.gov.uk/wiyby/wiybyController?topic=floodmap&layerGroups=default&lang=_e&ep=map&scale=9&x=390293.75&y=423441.66666666674 [Accessed 22/03/2012]. 15 EA Flood Map (Reservoirs) [online] Available at: http://maps.environment-agency.gov.uk/wiyby/wiybyController?topic=reservoir&layerGroups=default&lang=_e&ep=map&scale=7&x=390293.75&y=423441.66666666674#x=390294&y=423442&lg=1,&scale=9 [Accessed 22/03/2012].



Receptor Potential Effects considered

Sensitivity Comment

Groundwater and sub-surface water

Pollution as a result of erosion and sedimentation from construction activities and uncontained spills from chemical handling / storage. Diversion of subsurface flows as a result of track construction and the installation of turbine foundations / hardstanding.

Moderate Considered moderate sensitivity as groundwater in the area is not used as a potable supply for public use, although it does have private water supplies to the north of the Development. The Development is not located within a groundwater Protection Zone. However, hydrocarbon pollution in bedrock fissures has a lengthy attenuation period.

Soils (except peat)

Pollution as a result of track construction and chemical handling / storage.

Low Considered low sensitivity as the receptor (where present at the Development site) has some capacity to filter, breakdown and attenuate most potentially polluting chemicals and sediment over time. Additionally, the receptor is not used for agricultural purposes.

Peat Pollution as a result of track construction and uncontained spills from chemical handling / storage. Drying out or destabilisation of peat as a result of construction activities.

High Considered high sensitivity as the function of the receptor could potentially be permanently altered by construction activities or by chemical impacts. However, the receptor has some capacity to filter and attenuate most potentially polluting chemicals and sediment over time. Reinstatement / re-wetting of this receptor is possible.

Mire Plant Communities

Pollution as a result of track construction and uncontained spills from chemical handling / storage. Drying out or destabilisation of peat as a result of construction activities.

Moderate Considered moderate sensitivity as the function of the receptors has been altered by anthropogenic influences, such as access track use and mining. The receptor has some capacity to filter and attenuate most potentially polluting chemicals and sediment. Reinstatement / re-wetting of this receptor is possible, if required.

Bedrock Losses of strata as a result of turbine excavations.

Low Considered low sensitivity as the function of the receptor would not be affected by the Development.

8.4.1 Development Design Mitigation Locating turbines within 50 m of the watercourses on the site has been avoided. If there is a requirement to micro-site turbines within the requested 20 m radius, turbines would not be micro-sited to within 50 m of watercourses.

A buffer zone target distance of 50 m has been established for ancillary structures / infrastructure around the minor watercourses (natural) at the Development. Due to geotechnical constraints on-site, one crane pad is proposed within 50 m of a watercourse in the catchment of Weather Hill Gulf. Given the minimal encroachment on



this buffer zone by only one crane pad, it is considered that the distance is adequate to avoid potential effects on on-site watercourses.

The Draft WCEMP (provided as Technical Appendix A8.2) describes water management measures to control water run-off and drain hardstandings and other structures during the construction and operation of the Development. This will form part of a Pollution Prevention Plan (PPP) to be implemented for the Development prior to and during construction.

The requirement for access tracks crossing watercourses was minimised, where possible, during the design stage. Further description of this is provided in Chapter 3: Project Description of this ES.

Concrete batching will not take place onsite. This decision was made in order to reduce the potential for the release chemical pollutants onsite.

The 50 m buffer zone for turbine foundations, in conjunction with measures set out in the WCEMP, is expected to be sufficient to avoid potential effects on on-site watercourses.

8.4.2 Good Practice Good practice will be followed in all aspects of construction, operation and decommissioning, specifically through a Pollution Prevention Plan (PPP).

The PPP will set out measures to be employed to avoid or mitigate potential effects for all phases of the Development, and will also include an Incident Plan to be followed should a pollution event occur. This plan will be produced prior to construction following consultation and agreement with the EA, CMBC and Yorkshire Water, and all appropriate personnel working on the site will be trained in its use. The Construction Project Manager will have specific responsibility for implementation of the PPP.

Method statements will also be applied for specific elements of the construction process, which will follow the principles laid out in relevant EA Pollution Prevention Guidelines.

8.4.3 Potential Construction Effects This section identifies and assesses the types of effects that could result from the construction activities outlined in Chapter 3: Project Description of this ES, taking into account the control measures set out in the Draft WCEMP.

8.4.3.1 Chemical Pollution

8.4.3.1.1 Surface Water Potential risks include the spillage or leakage of chemicals (e.g., lubricants, detergents, etc.), fresh concrete, foul water, fuel or oil, during use or storage on site. In the case of a spill or leak, these pollutants have the potential to adversely affect surface water quality.

Measures such as absorbent spill pads, impermeable geosynthetic membranes, drip trays, and designated refuelling areas and other measures highlighted within the Draft WCEMP will contain any point releases of chemicals associated with spills and other incidents, which would be dealt with according to the agreed Emergency Response Plan. This would effectively limit the release of chemicals to minor fugitive releases. These would be minimised through best practice construction methods such as vehicle speed limits and regular vehicle and machine maintenance, as set out in the Draft WCEMP.

Therefore, effects on watercourses of moderate sensitivity will be of negligible magnitude and (in accordance with Table 8.2) of negligible significance.



8.4.3.1.2 Sub-surface Water (including Groundwater) Potential risks include the spillage or leakage of chemicals (e.g., lubricants, detergents, etc.), fresh concrete, foul water, fuel or oil, during use or storage on site. In the case of a spill or leak, these pollutants have the potential to adversely affect sub-surface water quality and groundwater. Pollutants coming into contact with bedrock also have the potential to indirectly alter the pH value of the groundwater resource. pH and chemical alterations to bedrock are difficult to rectify due to the fractured nature of the rock and the lengthy attenuation and dispersal of chemicals.

Measures such as spill pads, impermeable geotextile membranes and measures described within the WCEMP will effectively limit the uncontained release of chemicals to minor fugitive releases. Therefore, effects on bedrock (low sensitivity) and groundwater (moderate sensitivity) will be of negligible magnitude and, therefore, (in accordance with Table 8.2) of negligible significance.

8.4.3.2 Erosion and Sedimentation Erosion and sedimentation can occur from excavations, de-watering, ground disturbance and overburden stockpiling. Sediment entering groundwater has the potential to affect water quality, ecology and flood storage capacity.

Measures, including silt traps, lined settlement lagoons, swales and interception bunds, which are described within the Draft WCEMP, will effectively prevent sediment entering groundwater and off-site surface water and hence the magnitude of this potential effect will be negligible.

The moderate sensitivity of groundwater and negligible magnitude of effect result in the effects on groundwater associated with erosion and sedimentation being assessed as being of negligible significance.

Given the vegetated nature of the drainage ditches onsite, sediment is likely to drop out of suspension even without the presence of good practice measures. Therefore, effects on surface drainage ditches and offsite watercourses of moderate sensitivity will be of negligible magnitude and (in accordance with Table 8.2) of negligible significance.

8.4.3.3 Change to Soil and Peat Interflow Patterns Some turbine base excavations may need temporary sub-surface water controls, such as physical cut-offs or de-watering. These temporarily divert flows away from the excavation, and temporarily lower the local water table and sub-surface water levels in peat. Localised temporary changes to soil and peat interflow patterns may therefore arise. Turbine foundations and crane hardstandings also have the potential to change sub-surface water flow by creating physical barriers within naturally occurring drainage macropores in soil or peat.

The drying out of peat can result from alterations to the natural drainage regime. Measures set out in the Draft WCEMP, such as the rewetting of peat through controlled irrigation techniques, are considered sufficient, and sufficiently reliable, to avoid substantial alterations to the natural drainage regime. As a result, peat is not expected to dry out, beyond what would be the case in the baseline scenario. No substantial impediments to near-surface water flow will be created as the detailed site drainage design will take into account any severance of saturated areas to ensure hydrological connectivity is maintained. Consequently, effects on peat (high sensitivity receptor) are considered to be of negligible magnitude and therefore negligible significance.

8.4.3.4 Compaction of Soils Construction of access tracks and movement of construction traffic, in the absence of construction good practice, can lead to compaction of the soil. This can reduce soil permeability, potentially leading to increased run-off and increased erosion. The superficial geology underlying the Development is generally of low permeability, so the effects of compaction would not result in a significant increase in runoff from existing conditions. Access tracks for the Development have been designed to avoid impinging



on areas of heavily saturated ground. In order to maintain the current level or improve the drainage, it is necessary to ensure that construction methods do not seriously disrupt the established drainage and that no areas are surcharged, either by water discharge or spoil. As set out in Technical Appendix 8.2 of this ES, floating roads are proposed where peat depth is greater than 1 m, which maintains hydrological connectivity. Maintenance of existing drainage is critical to avoid compaction of soils, therefore all existing drainage network channels will be maintained and where necessary, channelled below the proposed road construction, as described in the Draft WCEMP. Drainage ditches on the upslope of the road will be required on side-long ground; the ditches should be constructed with small dams and cross drains where necessary in order for water can to below the road at regular intervals and that concentrated discharges to soil / peat on the down slope side of the road are avoided.

Existing access tracks have been used in the design where practicable, further reducing the potential for soil compaction.

Furthermore, the percentage of the hydrology study area proposed for new infrastructure is small (approximately 0.23 %16

8.4.4 Effects on the Hydrological Function of Bog Communities

). For these reasons, the magnitude of this effect will be negligible. Given the moderate sensitivity of soils and the high sensitivity of peat and negligible magnitude of effect, the effects associated with the compaction of soils are considered to be of negligible significance.

Figure 6.2 in Volume II: Figures of this ES identifies National Vegetation Classification (NVC) community species. The effects on the hydrological function of peat bog communities is assessed in this Chapter, however, potential effects on peat bog communities themselves are discussed in Chapter 6: Ecology of this ES.

Two NVC communities, which are included within Natural England’s ‘Assessing Impacts of Wind Farm Development on Blanket Peatland in England Project Report and Guidance’, have been identified within the Development site. These communities are M6 and M20. The guidance encourages peat bog communities to be identified in relation to distance from infrastructure, (which is outlined in the following paragraphs) and potential effects on the hydrological function of peat bog to be assessed.

The three potential NVC communities which have been identified within and adjacent to the Development site include:

• M6: species-poor acid flush and marshy grassland habitat which is located in three distinct areas in the central section of the Development. Approximately 0.46 ha of access track will cross this habitat between turbine 1 and turbine 2. This will lead to a direct loss of 0.46 ha of acid flush, while marshy grassland will not be directly or indirectly affected by the Development, as it is separated from construction activities by approximately 300 m and lacks any strong hydrological links with construction areas; and

• M20: dry and wet modified bog is located in the south-eastern section of the Development. Approximately 0.85 ha of access track and crane hardstanding will be located in this habitat. This will lead to a direct loss of 0.85 ha of M20.

Indirect effects may occur through localised changes in hydrology as a result of the construction process. This may result in localised drying or wetting of existing vegetation near to construction areas. However, measures outlined in the Draft WCEMP and a programme of post-construction habitat restoration will be implemented in locations to minimise the long term habitat loss.

Good practice design and construction (outlined in Section 8.4.1 of this Chapter) and measures outlined in Technical Appendix A8.2 will minimise potential effects of the Development on species M6 and M20.

16 Approximately 1.81 ha of new infrastructure in a 760 ha Midgelden Brook catchment area.



Site infrastructure has been designed to minimise the loss of, and disturbance to, these habitats, for example by designing (as far as possible) tracks to avoid following contours and avoiding construction in upslope areas, thereby reducing hydrological disturbance.

Prior to access track construction, site operatives will identify flush areas, depressions or zones which may concentrate water flow. These sections will be spanned with plastic pipes or drainage matting to ensure hydraulic conductivity under the road, and reduce water flow over the road surface during heavy precipitation. In accordance with Table 8.3, peat bog communities are defined as moderate sensitivity (see Table 8.3). Given the limited extent, localised nature and limited change in hydrology of soils in the vicinity of these communities, the magnitude of effect on the hydrological function served by these communities is considered to be minor. Given the moderate sensitivity of these communities, the predicted effects on the hydrological function of M6 and M20 will be of minor significance. This is not significant in terms of the EIA Regulations.

8.4.4.1 Impediment to Watercourse Flow The access tracks will require the installation of 4 new crossings of minor upland streams and the upgrade of 2 existing crossings. The two upgraded crossings will be undertaken as part of the road to Reaps Moss windfarm.

The minimisation of the number of proposed crossings and the re-use of the existing drainage ditch crossings reduces one of the main activities that could give rise to impediment of flows. Additionally, measures described in the WCEMP, such as the use of wide bottomless-arched culverts (where appropriate), will be effective in preventing impediments to flow being created. The crossings will be designed in consultation with the EA and the landowner.

Therefore, the effects on watercourse flows, of moderate sensitivity, are considered to be of negligible magnitude and therefore (in accordance with Table 8.2) of negligible significance.

8.4.4.2 Migration of Pollutants from Contaminated Land Desk studies have not identified any areas of contaminated land where new Development infrastructure is proposed (as part of Gorpley wind farm) and no effects are anticipated. The northern construction compound, to be installed as part of Reaps Moss wind farm and subsequently used for the Development, is located on inert waste as part of the historic Former Pipeworks Landfill. Given the inert nature of the waste (bricks, soil, glass etc.), no effects from contaminants are anticipated. However, should potentially contaminated land be encountered during excavations, this would be tested and appropriate action taken in accordance with The Environmental Protection Act 199017

8.4.4.3 Increase in Water Run-Off and Flood R isk

. Effects associated with contaminated land are therefore considered to be of negligible magnitude and, therefore (in accordance with Table 8.2) of negligible significance.

Increased water run-off has the potential to have a range of indirect effects discussed in this section (sedimentation, chemical pollution, soil flow changes, etc.). The increase in hardstanding areas could increase the volume and rate of localised surface water run-off. The relatively impermeable nature of the superficial geology, however, means there will be low natural infiltration and thus low natural run-off rates within the Development, with surface water flowing to distinct incised natural drainage channels. For this reason, the introduction of a limited amount of hardstanding into an area of low permeability is unlikely to contribute to substantial levels of additional run-off compared to the baseline situation. As such the magnitude of this effect is considered

17 The Environmental Protection Act 1990 [online] Available at: http://www.legislation.gov.uk/ukpga/1990/43/contents [Accessed 22/09/2012].



to be negligible. Given the moderate sensitivity of watercourses and the negligible magnitude of effect, the significance will be negligible, in accordance with Table 8.2.

There are no active floodplains on the Development site, and the EA has no records of flooding at the Development site. Although the potential magnitude of increased flood risk from the Development is assessed as minor, the likelihood of this occurring is considered to be unlikely and therefore the overall effect is considered to be negligible and therefore of negligible significance. A Flood Risk Assessment is provided in Technical Appendix A8.1.

8.4.4.4 Effects on Public Water Supplies Yorkshire Water identified no water supply infrastructure within 250 m of infrastructure within the Development site.

Gorpley Reservoir, approximately 400 m to the north east of turbine 2, is no longer used as a potable public supply.

As such, no effects on public water quality or quantity are anticipated during all phases of the Development.

8.4.4.5 Effects on Private Water Supplies CMBC identified five surface or near-surface water abstractions within approximately 1 km of the Development site and one borehole abstraction within 1.5 km of the Development site.

The supplies at Higher Ditches, The Bungalow, Lower Ditches, Gorpley Bungalow and Shackleton Farm are located within different surface water and near surface water catchments to the Development on separate geological slopes. Additionally, groundwater and near-surface water at the Development flows in a north-easterly direction and is largely separated from the sub catchment in which South Grain Farm draws water from by changes in topography (Figure 8.1 shows the sub-catchments).

All supplies are also of such a distance from the Development infrastructure (all beyond 770 m) that, in the unlikely event of the low level release of any pollutant and in the highly unlikely event of the pollutants migrating across or up-slope towards the private water supplies, there would be sufficient distance across which to dissipate and / or dilute before reaching the supply, and hence no effects on water quality are anticipated during all phases of the Development.

Some turbine base excavations may need temporary sub-surface water controls, such as physical cut-offs or de-watering. These temporarily divert flows away from the excavation, and temporarily lower the local water table and sub-surface water levels in superficial deposits. Localised temporary changes to soil interflow patterns may therefore arise.

Turbine foundations and crane hardstandings also have the potential to change sub-surface water flow by creating physical barriers within naturally occurring drainage macropores in soil.

Given the distance between South Grain Farm and the nearest Development infrastructure which will require major excavation and / or dewatering techniques (1.35 km), such localised changes in the water table and sub-surface water levels will not lead to a change in the baseline condition of groundwater at South Grain Farm. Additionally, good practice construction measures, such as installing silt fencing and silt traps (outlined within Section 5.3 of the WCEMP) on the downslope of access tracks will ensure that any loose material from the use of access tracks will be prevented from entering the hydrological system and migrating to sub-surface water utilised by the borehole at South Grain Farm.

Potential effects on private water supplies are therefore considered to be negligible, and not significant in terms of the EIA Regulations.



8.4.4.6 Peat Destabil isation Peat instability is generally the result of a combination of causative factors. Several construction activities have the potential to increase the likelihood of peat slides or bog bursts in areas where peat is present at a sufficient depth where gradients are sufficiently steep to result in a peat slide event. Further detail on the factors relating to peat slide risk is presented in Technical Appendix A8.3.

Construction activities that have the potential to increase the likelihood of peat slides or bog bursts include placing infrastructure or turbines on the break of a slope, infrastructure altering naturally occurring drainage channels, the removal of surface vegetation in areas of peat and peat excavation at the base of a slope.

The results of the peat probing exercises indicate that much of the area on which the Development is located has minimal deposits of peat.

The Peat Slide Risk Assessment, provided as Technical Appendix A8.3, details the assessment of peat stability at the Development site and for the proposed infrastructure.

The Peat Slide Risk Assessment has shown the peat stability at the proposed infrastructure across the survey area to be of generally negligible or low stability risk rating, with only turbine 1 recorded as presenting a medium stability risk (corresponding to moderate significance). In this case the peat is not extensively developed around the turbine location, and the gradient is the main component of risk.

No areas of high stability risk were recorded within the survey area. Drawing 5 of Technical Appendix A8.3 shows the Development overlaid on the peat stability risk zonation plan.

Of the 239 probe locations the following stability risk rating has been established:

• No peat was recorded at 54 locations, hence no risk; • Negligible risk at 66 individual probe locations; • Low risk at 100 individual probe locations; • Medium risk at 71 individual probe locations; and • High risk at 2 locations.

There are no high risk areas of peat instability located at any turbine locations or along the proposed track layout. Of the medium risk probe locations, 5 areas were considered to have either a potential impact on the Development infrastructure or could have an impact on the local watercourses. These areas are considered further and shown on Drawing No. 5 within Technical Appendix A8.3.

For these areas, the magnitude of potential effects without mitigation is considered to be moderate, which, combined with the moderate sensitivity of potential receptors (watercourses and groundwater), leads to an effect of moderate significance, which, in accordance with Table 8.2, is significant in terms of the EIA Regulations.

The access track to the consented Reaps Moss wind farm, which has not yet been built but that is proposed for use as part of the Development, is not considered within the peat slide risk assessment in Technical Appendix A8.3. The baseline peat environment for this section of track is set out in Section 8.3.5 of this Chapter. An assessment of issues relating to peat on this track was made in support of the Reaps Moss Wind Farm18

8.4.5 Potential Operational Effects

, and the conclusions identify no significant effects.

Potential medium and long-term effects associated with Development infrastructure such as access tracks, turbine bases and hardstandings could potentially include:

• Increased water run-off rates and volume;

18 Sinclair Knight Mertz (2008). Lancashire Wind Farms: Peat Assessment and Management.



• Increased levels of erosion and sedimentation; • Alterations to natural flow pathways; and • The risk of a pollution event.

These effects have been discussed earlier in relation to the construction phase. During the operational phase there would be substantially less activity and there is unlikely to be any ground disturbance, therefore the magnitude of these effects would be substantially reduced during the operational phase. Alterations to natural flow pathways would not be introduced during operation, but any changes occurring during construction would remain through operation, as the permanent infrastructure would remain in place. These potential effects will be further reduced through adopting best practice design and construction, as set out in the Draft WCEMP (Technical Appendix A8.2), such as cross drainage, use of shallow drainage ditches, prevention of blockages, and adherence to a PPP, as discussed earlier. As a result, the magnitude and significance of all potential residual effects associated with operation of the Development are assessed as being negligible.

8.4.6 Potential Decommissioning Effects Potential effects of decommissioning the Development are similar in nature to those that could occur during construction, as some ground-work would be required to remove turbine foundations and hardstandings to a depth of 1 m below ground level. However these effects would be of substantially lesser magnitude than during construction, and would be controlled by a PPP, as discussed in the previous sections. Where infrastructure would be left in place, drainage features would also be left in place, where this is compatible with the PPP. As a result, the magnitude and significance of all effects associated with decommissioning are assessed as being negligible.

8.5 MITIGATION MEASURES Mitigation measures are proposed relating to peat stability only. All other potential effects have been assessed as being of negligible or minor significance.

Mitigation measures to reduce peat slide risk are set out in the Peat Slide Risk Assessment (Technical Appendix A8.3). These are divided into general measures to reduce peat slide risk in all areas, whether the risk has been assessed as significant or not, and specific measures that will be implemented at particular locations identified as having the potential for significant effects.

General measures include:

• Construction will be supervised by qualified and experienced personnel; • All existing drainage features within the access track corridors will be identified and

marked; these drainage features should be maintained (not enhanced) during the construction and operational phases of the Development;

• Install cross drains at regular intervals to maintain interstitial groundwater flow through the peat mass below the tracks where road settlement could reduce the natural permeability;

• Install additional drainage in areas up-slope to any access track to prevent ponding and possible instability;

• Install small weirs at regular intervals along the track side drains to prevent significant water velocities in the side drains causing deep erosion in the peat;

• Where construction is required over peat areas in excess of 1m deep, this should be undertaken with a floating track construction, where the integrity of the peat allows;

• Longitudinal gradients to be consistent with limitations of the heavy lift and large transport vehicles, probably no steeper than 1V:8H;

• Crossfalls on the track surface to shed water to the up-slope drainage ditches; • Cut and fill should be avoided in peat greater than 1.5 m deep if possible; if not,

the following requirements on side long ground should be adopted:



• Excavate to a sound stratum; • Construction surface to be essentially horizontal with a slight fall to aid drainage; • Where the depth of cut is deemed unstable, employ a stepped or benched surface

with the intention of minimising the exposed surface of the up-slope cut face; • Protect all exposed peat surfaces from erosion and desiccation, by ensuring the

integrity and moisture content of the peat is maintained; and • The top of cut slopes should be provided with a small bund to retain the peat to

prevent desiccation and maintain the local stability of the peat.

The following are preventative measures to reduce potential effects on peat stability at areas identified at the location of Turbine 1. These are in addition to those set out in the WCEMP, which will be adopted by the Construction Contractor, unless other measures providing equal or better mitigation are developed.

Risk reduction can best be achieved by minimising the effect of any construction works and an appropriate construction method statement is believed to be an integral element in ensuring that all parties understand and acknowledge the potential consequences of a peat slide.

The preferred foundation solution for areas of thick peat will be a gravity pad foundation bearing on a sound stratum. The side slopes of the excavation in the peat should be maintained in a stable condition throughout the construction process; consideration should be given to constructing a rock retaining bund (rock doughnut) prior to excavation of the peat.

More detailed ground investigations will be required to facilitate the geotechnical design of the various foundations and access road, particularly the vertical and horizontal alignment and the design of the river / stream crossings. These will be incorporated into the Construction Method Statement which will be submitted to the EA, NE and CMBC for approval as part of the condition compliance prior to any site works commencing.

8.6 RESIDUAL EFFECTS The mitigation measures set out above in relation to peat slide risk are considered to be effective in reducing the magnitude of potential effects to negligible. Combined with the high sensitivity, potential effects have a negligible significance, in accordance with Table 8.2, which is not significant in terms of the EIA Regulations.

Residual significance for all potential effects is assessed as being negligible, except soil compaction which is assessed as being minor, and not significant in terms of the EIA Regulations. Therefore there are no significant residual hydrological effects predicted during the construction, operation or decommissioning phases of the Development.

8.7 CUMULATIVE EFFECT ASSESSMENT A cumulative effect is considered to be an additional effect on hydrological resources arising from the Development in combination with other proposed developments likely to affect the hydrological environment. At distances greater than 10 kilometres (km) or outside the catchment in which the Development is located, it is considered that schemes are unlikely to contribute to a cumulative hydrological effect due to attenuation and dilution over distance of potentially polluting chemicals. Therefore, for the purposes of the assessment of potential cumulative effects on the immediate catchment and hydrological regime, only proposed developments, which require large scale construction / excavation, within approximately 10 km of the Development have been considered.

The potential for a cumulative impact to arise as a result of peat instability can only occur when another development is located on the same geomorphological zone as the proposed windfarm. There are no other proposed developments located on the same geomorphological zone as the Development. Therefore, stability effects on peat are not considered within this section.



The following wind farm developments have been omitted from this assessment as their construction phases will not overlap with the construction phase of the Development:

• Coal Clough Wind Farm – 5.25 km north - operational; and • Scout Moor Wind Farm – 6.6 km south west – operational.

The following developments have been scoped out of the assessment as they lie within a separate hydrological catchment to the Development:

• Scar End Farm - 3 km north west – River Irwell catchment.

It is likely that the Development construction phase (due to start in 2014 and lasting between 9 and 12 months) could coincide with the construction phase of the following wind farms:

• Reaps Moss Wind Farm – approximately 0.75 km west – consented – access track in Midgelden Brook / Rochdale Canal catchment;

• Crook Hill – approximately 1.5 km south – consented – partly within Rochdale Canal catchment;

• Todmorden Moor -2 km north – consented – Midgelden Brook / Rochdale Canal catchment; and

• Coal Clough Repowering - 5.25 km north – in planning – Calder / Rochdale Canal catchment.

At these distances, the primary cumulative hydrological effect is likely to be an increase in surface water runoff during the construction phase. As noted within the Section 8.4.4.3 of this Chapter, these potential effects are considered to be of negligible magnitude for the Development. Water management measures will be implemented at the developments above similar to those described in the WCEMP (in line with normal practice and as would be required by the EA). As such, the magnitude of combined effects will be negligible and, therefore, of negligible significance. It is worth noting, in addition, that the contribution of the Development to these combined effects will also be negligible.

The electrical connection from the Development control building to the off-site substation is expected to be made via underground cables to be routed along road-side verges, where possible, and this is anticipated as being the most likely scenario. In combination with the Development, this is unlikely to lead to any cumulative hydrological effects of more than negligible magnitude, and hence the Development is considered very unlikely to have cumulative effects with the proposed grid connection.

8.8 STATEMENT OF SIGNIFICANCE This Chapter has assessed the significance of potential effects of the Development on the hydrology and hydrogeology resource. Gorpley Wind Farm has been assessed as having the potential to result in effects of a minor significance or lower.

Given that only effects of moderate significance or greater are considered “significant” in terms of the EIA Regulations, the potential effects of the Development on hydrology and hydrogeology resources are considered to be not significant.

Documents

8 GEOLOGY, HYDROLOGY AND HYDROGEOLOGYBest Practice Guide for Proposed Electricity Generation Developments’ (2006). There is no relevant English guidance for peat survey, assessment