permeable layers which have the capability to support water supplies at a local rather than strategic scale and provide an important source of base flow to rivers.
60.
The Till and Clay formations within the region are defined as unproductive strata. These are deposits with low permeability, and have a negligible significance for water supply or base flow to rivers.
61.
The dominant bedrock beneath all areas of site, albeit at depth in most places, is the Cretaceous Chalk which is defined by the Environment Agency as a Principal Aquifer. This rock has secondary permeability (fracture flow), can provide a high level of water storage and supports water supply and base flow to rivers. Its vulnerability to pollution is reduced where it is protected in most areas by the overlying (unproductive) London Clay Formation or Lowestoft Formation. In river valley areas where down cutting has removed the overlying strata and has replaced it with more permeable alluvial deposits, the vulnerability of the aquifer to pollution is increased and is greatest where the Chalk outcrops (with no superficial deposits overlying) especially in the area around Claydon.
62. A summary of the aquifer designations for each stratum is presented in Table 19.13 below.
Table 19.13 Summary of Environment Agency Aquifer Designations Stratum
Description Alluvium
Marine and Coastal Zone Deposits: Mud
Head Drift
River Terrace Deposits (undifferentiated)
Glaciofluvial Deposits Lowestoft Formation
Kesgrave Catchment Subgroup
Red Crag Formation Solid Coralline Crag
Preliminary Environmental Information May 2014
Calcrenite (sand)
Variably sandy, silty Clay
Mud
Stony sandy clay and clayey sand
Sand and gravel
Sand and gravel Stony, sandy clay
Sand and gravel Sand Aquifer Designations Secondary A Aquifer Unproductive Strata Secondary A Aquifer Secondary A Aquifer
Secondary A Aquifer Unproductive Strata
Secondary A Aquifer
Secondary A Aquifer Secondary A Aquifer
East Anglia THREE Offshore Windfarm
Chapter 19 Soils, Geology and Ground Condition Page 27
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