Forthbank Wind Energy Development - Partnerships for Renewables

Forthbank Wind Energy Development
Potential Construction Effects on Hydrogeology
13.4.24 The turbine foundations are expected to require the excavation of subsoil and landfill waste
material in the south-east, as well as potential made ground in the north-west of the site.
Excavation or penetration by deep (piled foundations) through any low permeability clay to
bedrock could result in preferential pathways being created, allowing leachate to enter bedrock
and impact on the bedrock aquifer. Additionally, excavations and/or deep piled foundations
are likely to disrupt any pore water, leachate and localised shallow groundwater in the
superficial deposits.
13.4.25 Dewatering may be required within the landfill and superficial deposits when turbine
foundations are being installed. Dewatering in the turbine foundations may impact any
leachate or groundwater levels by lowering the water table in the immediate vicinity of the
excavation. Leachate collected during any dewatering will need to be either passed through
the sewage treatment works or treated and disposed appropriately off-site.
13.4.26 It is noted that artesian conditions may be encountered in sand and gravel superficial deposits,
which may also require management to ensure that the groundwater does not come into
contact with leachate from the landfill.
13.4.27 There is also the potential to mobilise landfill leachate or leachate from any impacted potential
made ground in the north-west of the site and create a pathway to the underlying bedrock
during construction works. However it is understood that leachate is currently pumped to the
sewage works and confined within the site.
13.4.28 Should cast in-situ piles be required to be installed into the bedrock at the turbine locations, the
installation of the piles may come into contact with groundwater in the bedrock aquifer and
have localised impacts on the groundwater regime.
13.4.29 As the underlying bedrock aquifer is dominated by fracture flow, the leaching of hydrocarbons,
chemicals, transformer oils and fuel leaks from any spills during construction present a
potential source of contamination to the site. The low permeability superficial deposits
(Boulder Clay and Carse Clay) on the site is expected to provide some protection to the
groundwater in the bedrock, however the low permeability deposits are not continuous across
the site.
13.4.30 The magnitude of the above impacts on the groundwater environment is considered to be
moderate.
Private Water Supplies
13.4.31 There were no private water supplies identified by Clackmannanshire Council within 3km of the
site. Therefore the magnitude of the risk to private water supplies is negligible.
Public Water Supplies
13.4.32 There was no public water infrastructure identified by Scottish Water on the site. Therefore the
magnitude of the risk to public water supplies is negligible.
November 2010 Chapter 13 Page 24
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