141. Two statutory designated sites, the Deben Estuary Ramsar, SPA and SSSI and Suffolk Coast and Heaths AONB, are crossed by the onshore electrical transmission works and are likely to be affected directly or indirectly by the construction activities. Under both scenarios, the Deben Estuary, Martlesham Creek and wetland areas of the AONB will be crossed using HDD techniques which will avoid direct impact upon the designated areas prior to cable installation therefore there will be no impact.
142. Only one non-statutory designated site lies within the study area but due to its distance from the onshore electrical transmission works, no impact is anticipated from the construction activities.
143. The dominant geology at landfall is the Red Crag Formation which is classed as a Secondary A Aquifer. No SPZs are present at the landfall nor are there any licensed private groundwater abstractions. Confirmation is being sought by the Suffolk County District Council as to the location of any unlicensed private water supply abstractions with the landfall area. This information will update the impact assessment as part of the final ES.
144. There will be no dewatering required as part of the HDD works, the magnitude of impact to groundwater levels is considered to be negligible and therefore potential impact to the groundwater resources is considered to be negligible. The geology beneath the onshore electrical transmission works from landfall to Great Bealings predominantly comprises granular sand and gravel type material within the Kesgrave Catchment Subgroup, Alluvium or Red Crag. The sensitivity of the groundwater from Great Bealings westward is considered to be high.
145. From Great Bealings to the converter station, the level of magnitude of potential impact from the construction works is considered to be medium, given that there is the potential to have a slight impact on resource use (based on an impact to groundwater quality). There is increased risk, especially in the areas of the Gipping Valley, where there are exposed chalk outcrops, and areas where the onshore electrical transmission works are within the SPZs. Therefore the significance of the impact is considered to be a moderate adverse impact.
146. The release of leachates from landfills or other potentially contaminative materials into either a Secondary A or Principal Aquifer is considered of high magnitude. The significance is therefore considered to be major or moderate adverse. Additional mitigation to reduce the impact significance has been described in Table 21.14.
147. Crossing points and crossing methodologies (e.g. HDD at main rivers) have been selected to minimise impacts and preserve valuable features as far as possible. HDD
Preliminary Environmental Information May 2014
East Anglia THREE Offshore Windfarm
Chapter 21 Water Resource and Flood Risk Page 49
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