Environmental Statement South Kyle Wind Farm August Appendix 12.9: The Habitat Loss and Disturbance Calculations

Transcription

1 Appendix 12.9: The Habitat and Disturbance Calculations 1.1 Introduction 1 This appendix details the approach, assumptions and results of the process adopted to quantify habitat loss and degradation as a result of the construction of the proposed wind farm for the ecological impact assessment presented in Chapter 12. Habitat loss, disturbance and potential degradation has been estimated using the Phase 1 habitat survey results and the scheme layout design as released in December Where there is uncertainty various assumptions have been made regarding the construction methodology to arrive at a realistic worst case estimates. 2 This rest of this appendix is structured into the following sections: Calculating Direct Habitat Calculating the Extent of Habitat and Disturbance The Calculations The Results 1.2 Estimating Habitat / Potential Change 3 Direct habitat loss will occur as a result of the construction of the permanent elements of the wind farm infrastructure such as the wind turbine bases, crane pads, control building, access roads, passing places and turning points. 4 There are three main types of access road proposed: Upgrade to existing forestry tracks; New 'cut' roads constructed on hard ground, on less than one metre depth of peat, or on steeper gradients (greater than 1:10); and New 'floated' roads constructed on softer ground of typically greater than 1 m peat depth. 5 Cut roads can have a greater impact on terrestrial habitats because of the associated earthworks, in particular where the track runs across a slope requiring a cutting and embankment to be created. Cut tracks also normally require drainage ditches. The extent of floated track construction is not known at this time. Therefore, for the purposes of the habitat loss estimates it has been assumed that only cut roads will be used at South Kyle, even though a number of the new roads will pass over peat exceeding 1 m depth and would therefore be floated. 6 The dimensions assumed for the estimates of direct habitat loss for each of the built elements of the proposed wind farm are provided in Table below Zone of Construction Disturbance 7 Further to direct habitat losses there will be an area of ground surrounding the finished structure which will be subject to physical disturbance (that is plant trafficking and excavations). For the purposes of the habitat disturbance estimates it has been assumed that drainage ditches, cable trenches, banked Page 1 of 8

2 cut faces/batters around the turbine bases, associated compounds, crane pads and access roads, would be within 5 m of the finished structure. Therefore, an additional 5 m wide zone around the footprint of the structure has been included in the estimations of habitat loss / disturbance Zone of Hydrological Change 8 Some habitats adjacent to the zone of physical construction disturbance, particularly those sensitive to changes in surface hydrology such as blanket bog, will be indirectly affected due to hydrological changes associated with excavations for turbine foundations, borrow pits and access roads etc. At South Kyle, the most sensitive habitats to hydrological changes are blanket bog, modified bog, wet heath and acid/neutral flushes. 9 Hydrological changes may over time alter the plant species cover and composition in sensitive habitat types. If this were the case, the original type of habitat may change. An example of this is when blanket bog has new drainage ditches created adjacent to it causing a lowering in the water level and losses of bog specialist plant species being replaced by species that can tolerate drier conditions. This change over time is regarded as an indirect loss or degradation of habitat. 10 Areas of such blanket bog, modified bog and wet heath habitats within the proposed survey area are confined to small areas, typically along forestry rides, although there is a significant extent of blanket bog between turbines 7 and 10. Plants which are characteristic of these habitats are adapted to low nutrient, acidic and wet conditions, and therefore the maintenance of a high water table is critical to the long-term maintenance of these species. Artificial drainage of peat can cause the loss of such species; particularly bog mosses (Sphagnum spp.). In extreme cases this may result in enough loss of vegetation cover and structure to cause the eventual erosion of exposed peat. 11 In order to assess the full potential impact of construction works in sensitive habitats, it is therefore necessary to assume a potential zone of influence over the adjacent vegetation within the habitat change estimates so that longer-term changes to natural hydrology can be assessed. 12 Rani Nayak et al. (2008) provide examples from a literature review of measured zones of hydrological influence in blanket bogs and provided a regression equation to enable estimates of the extent of drainage effects around an area of disturbance. In order to use this equation is it necessary to have estimates of the hydraulic conductivity of the peat at the site that is being considered, taking into consideration broad patterns of variation in peat condition. Detailed information on hydraulic conductivity is not available for the South Kyle wind farm site. However, based on the case examples and information on peat hydrology impacts provided in Rani Nayak et al. (2008) a conservative potential zone of hydrological disturbance as a result of the proposed construction works in the relevant habitats has been assumed to be a 10 m wide strip beyond the zone of construction disturbance. 13 Calculations regarding the dimensions of each wind turbine site are based on an indicative hardstanding layout provided on 15 October The hardstanding layout described the location of the hardstanding and crane pads in relation to the turbine base. The 5 m construction disturbance zone and 10 m hydrological disturbance zone were therefore applied around a Page 2 of 8

3 single indicative hardstanding layout which includes 'turbine base + hardstanding + 2 crane pads'. 14 Calculations for the 5 m construction zone and 10 m hydrological disturbance zone around the site roads were considered separately to the indicative hardstanding layout. 15 However, as each site road would run adjacent to each of these 'turbine base + hardstanding +2 crane pads' areas, the disturbance areas are likely to be overestimated because they are, in effect, double-counted where the road is contiguous with the 'turbine base + hardstanding +2 crane pads ' areas. 16 The construction zone and hydrological disturbance zone estimations are therefore a worst-case scenario. 17 A revised turbine layout, including site roads, for the wind farm design was issued in early December This relocated turbine 49 and turbine 50. However, there was no new release of the indicative hardstanding layout; therefore, the indicative hardstanding layout was edited by MBEC to ensure that the turbine 49 and turbine 50 indicative hardstanding layouts were placed adjacent to the new road design. 1.3 The Calculations 18 The dimensions and extents of the various infrastructure elements for the proposed South Kyle wind farm are provided in Table below. Page 3 of 8

4 TABLE The Dimensions and Extents of the South Kyle Wind Farm Infrastructure As Provided in Chapter 4 Infrastructure Number or Length (km) Maximum Dimensions assumed (m) Total footprint area Turbine foundations, hardstandings, and crane pads Permanent wind monitoring masts 50 For each wind turbine: Hardstanding area = 45 m x 25 m = 1125 m 2 Foundations = 17 m diameter = 226 m 2 Each crane pad = 15 m x 10 m = 150 m 2 ; therefore two crane pads = 300 m 2 6 For each met mast (exact footprint not provided): Reinforced concrete foundation = 7 m x 7 m = 49 m m depth anchor points required for guy wires need concrete foundations (negligible area) Crane hardstanding adjacent to each mast = 15 m x 10 m = 150 m Temporary storage areas Temporary compounds Permanent welfare facility compound (part of a temporary compound) Electrical substation Windfarm connection compound m x 100 m m x 50 m m x 15 m No dimensions provided m x 35 m 0.12 Upgrading of existing site roads 25.9 km Existing roads would be widened by 2 m on average (from approximately 3 m to 5 m width) Approx New site roads 30.8 km 5 m running surface Approx Passing places and turning points 50 Approximately 40 m x 5 m (The exact location not provided so it is assumed they are equally spaced along the tracks, i.e. there is passing place on 3.6% of track.) Approx 1.00 Borrow pits 8 The original data provided in a shapefile from November 2012 are used. (There was a revised borrow pit footprint of ha provided in December 2012 but this has not been used, as requested by Vattenfall. This means that the impact from the borrow pits uses the worst-case scenario.) Total area Page 4 of 8

5 19 The total footprint (that is the area subject to permanent habitat loss and which could not be restored for at least the lifetime of the wind farm) has therefore been estimated at approximately 57 ha. 1.4 The Results Direct Habitat 20 Table at the end of this appendix shows how the total estimated direct habitat loss from the construction of the proposed wind farm divided across different habitat types without considering any indirect impacts and excluding the meteorological masts The Total Extent of Habitat and Change 21 Table at the end of this appendix provides the cumulative total estimates for direct loss and potential indirect change to hydrologicallysensitive habitats for each element of wind farm infrastructure. These losses and potential changes have been are fully considered within the ecological impact assessment reported in Chapter 12 (see Section ). 1.5 References Nayak D.R., Miller, D., Nolan, A., Smith P. & Smith J. (2008). Calculating Carbon Savings From Wind Farms On Scottish Peat Lands- A New Approach. The Scottish Government website. Page 5 of 8

6 TABLE Estimates of the Area of Phase 1 Habitats Lost (permanent and long term) based on Survey Area Estimates given in Table 12.7 of the Ecology Chapter. The percentage of the total area refers to the 2012 ecological survey area (Figure12.1). (If the habitat is not shown, there is no impact.) Description Met mast foundations Met mast crane hardstanding 1 New access tracks 2 Existing access tracks improvements (3m to 5m width) 2 Passing places 3 Turbine hardstanding 4 Turbine foundation Turbine crane pads Borrow pits Temporary compounds Temporary storage area Permanent welfare facility 5 Windfarm Connection Compound Sustation Total Area % of Total Footprint Area as a % of habitat within the 2012 ecological survey area Coniferous plantation woodland Dense/continuous scrub Coniferous recently-felled woodland Unimproved acid grassland Semi-improved acid grassland Marsh/marshy grassland Acid dry dwarf shrub heath Wet dwarf shrub heath Dry heath/acid grassland mosaic Wet heath/acid grassland mosaic Page 6 of 8

7 Blanket bog Wet modified bog Acid/neutral flush Standing water Other (borrow pit) Total Exact met mast foundation and crane hardstanding footprints have not been provided so the worst case scenario locations (centred on the point locations provided) are used as described in Table Access track footprint areas (particularly for new access tracks) vary from Table This is because GIS data has been used for Table and so is corrected for curving tracks and overlapping areas at junctions etc. 3 It is assumed that the footprint for passing places is 3.6% of the footprint for the tracks, as described in Table Turbine infrastructure footprint provided in December 2012 has been used as no footprint has been provided with the dimensions provided in July 2013 (Table ). The December 2012 footprint dimensions vary slightly from those shown in Table : Hardstanding area = 45 m x 28 m, Foundations = 242 m 2, Crane pads = 180 m 2 x 2, thus slightly overestimating the habitat area. 5 The permanent welfare cabin will remain during the lifetime of the wind farm. This will be within the temporary compound/storage area which will be removed at the end of the construction phase. There is therefore some over accounting for this 0.04 ha cabin area. Page 7 of 8

8 TABLE Combined Direct and Potential Indirect of Phase 1 Habitat Types to Each Type of Infrastructure Associated with Proposed South Kyle Wind Farm for the Most Sensitive Habitats Likely to be Affected by Changes to Hydrology Description Met Mast Infrastructure New access tracks Existing Access Tracks Improvements Passing places Turbine Foundation, Hardstanding & Crane Pads Borrow pits Temporary compounds/ temporary storage areas 1 Windfarm connection compound Substations Total area as % of habitat within 2012 ecological survey area Marsh/marshy grassland Wet dwarf shrub heath Blanket bog Wet modified bog Acid/neutral flush Total The permanent welfare facility is accounted for in the dimensions of the temporary compound/temporary storage area. Page 8 of 8