Galloper Wind Farm Project - National Infrastructure Planning

2890_mitigation
15
August 2011
Galloper Wind Farm Substation
4.2. Proposals submitted with the Development Consent Order
The final proposals that will be submitted with the Development Consent Order are
presented on drawings 2890/07H and 2890/12 in Appendix 4.
The strategy draws on the principles set out in section 3.0. It relates to the treatment of
land outside the substation as the design of the substation itself will be carried out by
future competitive tender. The principles of the location, heights, colour etc. of
substation infrastructure are therefore not discussed further but will be addressed as
the design of the substation evolves, following the principles set out in section 3.0.
4.3. Profiled landform around substation
Many iterations of engineering and landform permutations have been undertaken by
Galloper Wind Farm Limited and it has been concluded that the substation platform
level can be reduced to a maximum level of 9mAOD. This would generate a significant
volume of material that would be used to create a gently profiled landform around the
north, west and east sides of the substation, where it adjoins open fields.
Existing levels: The existing ground within the area covered by the western part of the
substation (the Galloper compound) lies between approximately 11.1 and 12mAOD.
The eastern part of the proposed substation (the transmission compound) falls from
approximately 11.4 mAOD in the south-western corner to 7.2mAOD in the northeastern
corner.
Proposed levels: It is proposed that the entire substation will be consented with a
maximum platform level of 9mAOD, but with downward vertical deviation
permissible up to 1m (to 8mAOD) to address potential ground variability and to
achieve satisfactory drainage falls on the platform. Note that this document works on
the basis of impacts from a 9m platform level, this being the ‘worst case’.
The outside face of the profiled landform will be a 1:10 slope so that it does not appear
steep 0r artificial and so that it grades gradually into the existing ground profile. The
inside slope will be 1:3. This steeper slope will not be visible from the surrounding
landscape.
The landform will have a limit of deviation in terms of its height limited to -100mm to
+300mm. Effects have been assessed as -100mm within the LVIA as this is the 'worst
case scenario'.
The landform has been set back from existing trees in Sizewell Wents wood to avoid
the root protection area.
The landform will be created with rounded edges and gentle integration between
existing and proposed slopes.