8 Geology, Hydrology, Hydrogeology

Transcription

1 Camster II Wind Farm Scoping Report 50 8 Geology, Hydrology, Hydrogeology 8.1 Introduction The EIA will consider the potential issues arising from the construction, operation and decommissioning of the proposed development in relation to existing and future potential geological, hydrogeological and hydrological impacts. It will assess the potential effects on surface and ground waters, (including Ground Water Dependant Terrestrial Ecosystems (GWDTE) and Private Water Supplies) and ground conditions. The assessment will provide baseline information; discuss potential mitigation and management and assess the significance of residual impacts assuming the proposed mitigation is implemented. 8.2 The Existing Environment Surface Water Features There are a number of surface water features present within the site including various burns (streams) and drains. One standing water body has been identified within the site. The entire development area is part of the Wick River catchment and generally drains to the north east Flood Risk The Scottish Environment Protection Agency (SEPA) indicative flood map (for a 1 in 200 or greater chance of being flooded in any given year) shows that there is the potential for flooding locally adjacent to Achairn Burn which runs to the north east through the centre of the site. The flooding would likely be contained within the 50m watercourse buffer standoff that is being observed within the land available for development. The Achairn Burn discharges into Wick River, approximately 4.5km to the north east of the site. Information regarding potential flood risk is shown on Figure 8. Potential flood risk will be considered for any new or upgraded watercourse crossings and in a preliminary drainage assessment Water Resources There are several properties located to the north, east and south of the site boundary that may be reliant upon the catchment for potable water supply and other water requirements. These abstractions are likely to be either surface water or localised shallow groundwater through boreholes. Under The Private Water Supplies (Scotland) Regulations 2006, councils have a duty to compile a list of private water supplies in their area and monitor the quality of the supplies. The Highland Council will be contacted regarding the presence of private water supplies either within or close to the site Geology The underlying geology comprises extensive and likely deep, peat deposits (blanket bog) which are likely to be overlying glacial deposits (glacial till) locally present at or close to surface with alluvium along the path of the Achairn Burn. The principal bedrock type is indicated to comprise the Spital Flagstone Formation with the Mey Flagstone Formation present locally in the far east of the development area, with both formations consisting of interbedded siltstone, mudstone and sandstone. A single roughly east-west trending fault crosses the development site close to the path of the Achairn Burn.

2 Camster II Wind Farm Scoping Report Ground Contamination Given the historical use as a commercial forestry and absence of development, it is unlikely that the developable area is contaminated. However information regarding pollution incidents and previous uses will be collated Deforestation The proposed development would involve felling of trees to allow installation of new access roads and wind turbines, which has the potential to affect the surface water and groundwater environment. The potential effect of deforestation will be considered with any appropriate mitigation measures. 8.3 Methods Study Area The study area is limited to the land available for development, as shown on Figure 2. Potential impacts on the peat resource upslope and downslope from and outside of the associated development boundary will be considered Desk Based Studies It is recognised that a variety of data is available from third parties i.e. British Geological Survey, SEPA and FCS. It is therefore proposed that the following tasks will be undertaken to ensure the baseline data informs the impact assessment: Review of Ordnance Survey (OS) maps to identify surface water features; Review of the River Basin Management Plan; Identification of the locations and characteristics of catchments, surface water features and springs within; the development boundary, and in the study area from desk-based data; Identification of Water Framework Directive (WFD) classifications and objectives, obtained from the SEPA website for watercourses within the study area; Collation of data and location of abstractions and discharges consents within the study area; Collation of information on climate, surface hydrology, water quality and flood risk; Identification of hydrogeological conditions and groundwater resources; Review of solid and drift geology maps; The James Hutton Institute for soil coverage (Macaulay soil maps); Review of historic maps; and Review of aerial photography. The data review will include a search for nationally protected geological Sites of Special Scientific Interest (SSSI) or Regionally Important Geological Sites (RIGS) or protected geo-morphological features within the vicinity of the proposed development. There are no records of coal mine workings in the vicinity of the proposed development or other mineral workings beyond small temporary quarries for forest access roads and quarries for the adjacent Camster Wind Farm Peat Risk Assessment

3 Camster II Wind Farm Scoping Report 52 AECOM s approach will be guided by relevant legislation (including waste management legislation) and the following best practice guidance documents: Developments on Peatland: Guidance on the assessment of peat volumes, reuse of excavated peat and the minimisation of waste, Scottish Renewables and SEPA, Version 1 (2012); Developments on Peatland: Site Surveys and Best Practice, Scottish Natural Heritage, SEPA, Scottish Government and The James Hutton Institute (2011); Good practice during windfarm construction, Scottish Renewables, Scottish Natural Heritage, SEPA and Forestry Commission Scotland, Version 1 (October 2010); Floating roads on peat, Forestry Civil Engineering and Scottish Natural Heritage (2010); and Regulatory position statement Developments on peat, SEPA (2010). Peat stability will be assessed in accordance with Natural Scotland s (Scottish Executive) publication Peat Landscape Hazard and Risk Assessments: Best Practice Guide for Proposed Electricity Generation Developments (December 2006) Phase 1 Peat Investigation The Phase 1 peat investigation will be undertaken on the land available for development as per the Developments on Peatland guidance. The majority of the developable area comprises existing forested land containing an irregular pattern of forest breaks with the remaining area comprising open moorland called the Flows of Leanas in the north-west of the developable area. Areas of relatively recent felling should be able to be traversed, as will open moorland excepting areas where the upper bog surface is considered incapable of providing safe support for crossing on foot. As such peat probing is recommended to be carried out along fire breaks and forest roads within forested areas these are generally present at intervals of between 200m. Initially, this probing interval is recommended to be extended to other areas (recently felled and open moorland). A hand-held GPS unit will be used for locating predetermined peat probe locations and probing will be carried out at the location or as near as practically possible with secondary probes carried out to check variability of the peat depth over short distances. A plan showing peat depths encountered across the development area will be prepared. Other peat features will also be noted and annotated onto the map, including eroded areas, areas of instability, gullies, sub-surface drainage etc. A preliminary assessment of peat slide hazard potential will be carried out in accordance with the Natural Scotland (Scottish Executive) 2006 guidance document Phase 2 Peat Investigation Further to the detailed and fixed design of the proposed development layout, Phase 2 peat probing will be carried out as follows, as per the Developments on Peatland guidance: One No. probe at 50m centres along proposed access track routes; Five No. probes at each proposed turbine; and Probing at other development infrastructure locations, including the proposed construction compound and sub-station (number of probes to be determined). The peat probing will inform both the estimates of the proposed peat volume for excavation and reuse and development of a peat management plan.

4 Camster II Wind Farm Scoping Report Carbon Calculation AECOM will undertake a carbon calculation in line with the Scottish Government Technical Note, Calculating Potential Carbon Losses & Savings from Wind Farms on Scottish Peatlands (version 2.0.1, dated 27th October 2012) and the latest version of the carbon balance calculator (version 2.7.0, dated 1st June 2012). This will be to determine potential carbon losses and savings associated with development on peat land taking into account any requirements for peat removal, habitat improvement and restoration. Values for the carbon content of peat will be taken from data provided by SEPA Walkover Survey A site walkover was undertaken on Wednesday 13th June 2012 following a desk-based review, the key findings of the walkover were: Topography comprises generally low rolling relief with ground level rising from the Achairn Burn to the south and north up to the summit of Tannach Hill in the south east and the Hill of Oliclett in the south west of the and Flows of Leanas in the north west of the development area. Approx average slope angles are of the order of 1:40 in the vicinity of Achairn Burn increasing to 1 in 10 to 1:20 along the slopes of Tannach Hill and Hill of Oliclett. Forest access roads are well constructed with limited rutting evident. Safe access was possible along fire breaks, although some were blocked by windblown trees with navigation around windblown trees possible. Forested areas ranged from some reasonably accessible plantation to impenetrable stands through which progress was not possible safely. From exposures the underlying geology comprises sandstone overlain by till and peat with potential for extensive deposits of blanket peat. Anecdotal evidence of the adjacent Camster wind farm management suggest that peat thickness is variable over short distances. This appears to be a result of the saw tooth nature of the moderately dipping strata and the way in which it has been eroded by glacial action (rock plucking glacial /geomorphological processes). A quarry is located at approximate NGR which has recently been worked as part of the Camster wind farm construction site, but currently appears to be non operational Hydrology & Hydrogeology Assessment A qualitative assessment will be undertaken using a combination of professional judgment, legislation and other statutory policy and guidance. Key acts of legislation, policy and guidance which will be considered in the preparation of this assessment include: Water Framework Directive (2000/60/EC); Water Environment and Water Services (Scotland) Act 2003; The Water Environment (Register of Protected Areas) (Scotland) Regulations 2004; Water Environment (Controlled Activities) (Scotland) Regulations 2005; Scottish Natural Heritage et al (2010) Good practice during wind farm construction; SEPA (2008) Engineering in the Water Environment Good Practice Guide Bank Protection; SEPA (2008) Engineering in the Water Environment Good Practice Guide - Construction of River Crossings; SEPA (2010) Engineering in the Water Environment Good Practice Guide Sediment Management; CIRIA Report C502: Environmental Good Practice on Site;

5 Camster II Wind Farm Scoping Report 54 CIRIA Report C532: Control of Water Pollution from Construction Sites; Scottish Planning Policy; SEPA Position Statement 06 Culverting of Watercourses; and SEPA Pollution Prevention Guidelines (PPGs). The assessment will identify potential effects mainly due to construction and decommissioning of the access tracks, watercourse crossings, turbine foundations, cable trenches, compound and storage areas etc. Some of the activities have the potential to continue having an effect during the operational stage. The potential effects identified include the following: Increased run-off on exposed ground causing pollution or leading to increased flood risk; Disturbance or erosion of bed and banks of watercourses and land drains; Increased run-off from hardstanding areas causing pollution or leading to increased flood risk; Dewatering of groundwater and peat during foundation construction; Pollution from accidental spillages; Cutting off natural surface and groundwater pathways; and Leaching of concrete into groundwater and peat. Practical mitigation measures will be proposed to remove, reduce or offset predicted negative impacts and these will feed into the scheme layout and design detail Assessment Methods and Guidance In assessing the significance of potential effects of the proposed wind farm, three key factors have been taken into account: The likelihood of that impact occurring based on a scale of certain, likely or unlikely; The sensitivity and/or importance of the receiving environment; and The potential magnitude of the impact Defining Significance The assessment of the significance of individual impacts on the receiving environment will be based on criteria for the sensitivity or importance of the resource and the magnitude of the impact, as defined in the following tables.

6 Camster II Wind Farm Scoping Report 55 Table 8.1: Sensitivity Definition Importance Criteria Description Very High The receptor has little or no capacity to absorb change without fundamentally altering its present character, is of very high environmental value, or of international The area occupied by the proposed development is protected by International EU legislation (World Heritage Sites, Geopark). Feature of international importance, for example a Special Area of Conservation (SAC). Critical social or economic uses such as for water supply, navigation or mineral extraction. Groundwater is a valuable resource because of its high quality and yield, or is known to be extensively exploited for water supply. Alternatively, groundwater is critical to designated sites of nature conservation High The receptor has low capacity to absorb change without fundamentally altering its present character, is of high environmental value, or of national Feature of national importance, for example a Special Area of Conservation (SSSI). High classification for water quality (i.e. A1 Excellent or A2 Good) or Sensitive habitats of national Groundwater is a locally valuable resource because of its moderate quality and/or yield, or is known to be locally exploited for water supply. Medium The receptor has moderate capacity to absorb change without significantly altering its present character, has some environmental value, or is of regional Site of local geological importance (Local Geological Site previously Regionally Important Geological Site). Moderate water quality (i.e. B Moderate). Groundwater of limited value because its quality does not allow potable or other quality sensitive uses. Exploitation of local groundwater is not extensive and/or local areas of nature conservation known to be sensitive to groundwater impacts.

7 Camster II Wind Farm Scoping Report 56 Table 8.1: Sensitivity Definition Importance Criteria Description Sensitive habitats of regional Low The receptor is tolerant of change without detriment to its character, is low environmental value, or local Sites with local geology / soils interest Heavily modified with poor water quality (i.e. C Poor). Poor groundwater quality and/or very low permeability make exploitation unfeasible. Changes to groundwater not expected to impact on local ecology. Limited economic or social uses. Negligible The receptor is resistant to change and is of little environmental value. Sites with little or no local geology / soils interest Very poor groundwater quality (i.e. D Seriously Polluted) and/or very low permeability make exploitation of groundwater unfeasible. Minimal economic or social uses. The impact magnitude considers the scale of the predicted change to baseline conditions resulting from a given potential effect and takes into account the duration of an effect i.e. temporary or permanent and whether it is direct or indirect. The magnitude of an impact is independent of the importance / sensitivity of a receptor. Definitions are described in Table 8.2. Table 8.2: Effect Magnitude Definition Magnitude High Medium Low Criteria Total loss or major alternation to key elements/features of the baseline conditions (designated geological site, peat, water quality or water body) such that post development character/composition of baseline condition will be fundamentally changed. Loss or alteration to one or more key elements/features of the baseline conditions such that post development character/composition of the baseline condition will be materially changed. Minor shift away from baseline conditions. Changes arising from the alteration will be detectable but not material; the underlying character/composition of the baseline condition will be similar to the pre-development situation.

8 Camster II Wind Farm Scoping Report 57 Table 8.2: Effect Magnitude Definition Magnitude Negligible Criteria Very little change from baseline conditions. Change is barely distinguishable, approximating to a no change situation. The significance of effect will then be determined using the matrix presented in Table 8.3. The significance of a given impact or effect is based on a combination of the sensitivity or importance of the receptor and the magnitude of a given potential impact. Impacts can be beneficial, adverse or negligible and their significance major, moderate/major, moderate, minor/moderate, minor or negligible. Table 8.3: Approach to Assessment of Effects Magnitude Sensitivity Very High High Medium Low Negligible High Major Major Moderate Moderate Minor Medium Major Moderate Moderate Minor Negligible Low Moderate Moderate Minor Negligible Negligible Negligible Minor Minor Negligible Negligible Negligible Impacts which are shaded are considered to be Significant impacts. Those that are not are considered to be not Significant Mitigation The EIA will consider appropriate mitigation measures to reduce the impact of any of the potential effects. The mitigation measures will be based on current environmental best practice guidance 8.4 Aspects to be Scoped Out Contaminated Land Assessment It is not proposed to undertake a contaminated land assessment due to the limited land use history of commercial forestry and absence of other potentially contaminative development. Therefore the likelihood of encountering contamination is low. However information regarding pollution incidents and previous uses will be collated and assessed Peat Testing / Sampling It is not proposed to undertake any sampling or testing of the peat material. Values for the carbon content of peat will be taken from published literature.

9 Camster II Wind Farm Scoping Report Conclusions and Summary The EIA will assess the geological, hydrogeological and hydrological impacts of the proposed development including the potential effects on aquifers, surface waters, water dependant habitats (including GWDTE) and human use of water resources. A peat slide hazard risk assessment will also be undertaken if required. Consultation with SEPA will be undertaken to ascertain the level of flood risk assessment that will be required. The effects of the proposed development will be assessed for the construction, operational and decommissioning phases. The EIA will also include a ground conditions review and a review of historic uses to confirm the assumption that the probability of encountering any contaminated land is low. 8.6 References British Geological Survey Sheet 110 Latheron 1:50,000 Combined, 1913 British Geological Survey Sheet 110 Latheron 1:50,000 Solid, 1985 British Geological Survey Sheet 116 Wick 1:50,000 Drift, 1913 British Geological Survey Sheet 116E Wick 1:50,000 Solid, 1986 British Geological Survey Sheet 116W Thurso 1:50,000 Solid, 1985 Calculating Potential Carbon Losses & Savings from Wind Farms on Scottish Peatlands (version version 2.7.0, 1st June 2012) CIRIA Report C502: Environmental Good Practice on Site CIRIA Report C532: Control of Water Pollution from Construction Sites Developments on Peatland: Guidance on the assessment of peat volumes, reuse of excavated peat and the minimisation of waste, Scottish Renewables and SEPA, Version 1 (2012) Developments on Peatland: Site Surveys and Best Practice, Scottish Natural Heritage, SEPA, Scottish Government and The James Hutton Institute (2011) Floating roads on peat, Forestry Civil Engineering and Scottish Natural Heritage (2010) Good practice during windfarm construction, Scottish Renewables, Scottish Natural Heritage, SEPA and Forestry Commission Scotland, Version 1 (October 2010) Peat stability will be assessed in accordance with Natural Scotland s (Scottish Executive) publication Peat Landscape Hazard and Risk Assessments: Best Practice Guide for Proposed Electricity Generation Developments (December 2006) Regulatory position statement Developments on peat, SEPA (2010) Scottish Natural Heritage et al (2010) Good practice during wind farm construction SEPA (2008) Engineering in the Water Environment Good Practice Guide Bank Protection SEPA (2008) Engineering in the Water Environment Good Practice Guide - Construction of River Crossings SEPA (2010) Engineering in the Water Environment Good Practice Guide Sediment Management SEPA Flood Map SEPA Position Statement 06 Culverting of Watercourses SEPA Pollution Prevention Guidelines (PPGs) The Private Water Supplies (Scotland) Regulations 2006 Water Framework Directive (2000/60/EC) Water Environment and Water Services (Scotland) Act 2003 The Water Environment (Register of Protected Areas) (Scotland) Regulations 2004 Water Environment (Controlled Activities) (Scotland) Regulations 2005