Thornton Glen SWT

Nature Conservation Value and Conservation Status

191.           Thornton Glen SWT is approximately 6.50 ha in area and lies within 45 m of the footprint of the Proposed Development at its closest point as shown on Volume 2, Figure 7.3 The site is designated for its broadleaved, semi-natural woodland habitat. The SWT includes two areas of AWI. These AWI stands are defined as Ancient (of semi-natural origin) 1a and 2b. This indicates that this area of the woodland corridor has been continuously wooded since 1750 (1a) and 1860 (2b). The Thurston Burn Valley LNCS overlaps the SWT.

Construction Phase

Impact

192.           As the Thornton Glen SWT lies over 15 m from the footprint of the Proposed Development no direct impacts are anticipated (e.g. habitat loss). The Proposed Development bisects the wider Thornton Burn and Braidwood Burn corridor at the location of a proposed cable bridge crossing which is to be installed over the Braidwood Burn (as shown on Volume 2, Figure 7.3, Figure A7.4 and Figure A1). These works may impact up to 2000 m2 of the riparian woodland corridor as discussed under Dunglass Burn LNCS. As these works have been micro-sited to pass through a natural gap in the woodland corridor it is anticipated that loss of tree canopy will be minimal and therefore the works are unlikely to result in the fragmentation of the woodland corridor.

Magnitude of Impact

193.           The cable bridge crossing is proposed across Braidwood Burn that passes through an area of broadleaved, semi-natural woodland that connects to Thornton Glen SWT to the east. The footprint of the works areas for the cable bridge crossing within the Dunglass LNCS is approximately 675 m2 and the route has been micro-sited to minimise tree felling requirements. At the location of the cable bridge crossing there is a natural gap in woodland and the canopy is comprised of a scattered semi-mature, multi-stem, ash trees with no mature tree specimens recorded within the footprint of the works. The cable bridge crossing is 40 m in length and 10 m in width therefore the footprint of the permanent works is estimated to be 400 m2. The habitat under the permanent footprint of works is predominantly semi-improved neutral grassland and dense scrub. Assuming this could affect a zone of up to 15 m on either side of the footprint of works, up to 2,000 m2 of the Dunglass Burn LNCS may be susceptible to temporary disturbance, including 140 m2 of broadleaved, semi-natural woodland, this is approximately 0.13% of the total extent of this habitat within the ecology study area.   

194.           The impact is predicted to be of local spatial extent, short-term duration, intermittent and medium reversibility. It is predicted that the impact will affect the receptor indirectly. The magnitude is therefore considered to be low.

Sensitivity of the Receptor

195.           The Thornton Glen SWT is deemed to be of medium vulnerability, low recoverability and local value. The sensitivity of the receptor is therefore, considered to be low.

Significance of the Effect

196.           Given the above consideration of sensitivity and magnitude, the effect significance is considered to be negligible to minor adverse and not significant under the EIA Regulations.

 

Secondary Mitigation and Residual Effect

197.           No secondary mitigation is considered necessary because the likely effect in the absence of secondary mitigation is not significant in EIA terms.