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identified, it will be recorded during a site audit and appropriate remedial actions will be implemented.


8 8.1 87


Ground Conditions Land Shrinkage


A complex pattern of ground conditions is present along the proposed onshore cable route. At a simplistic level the surface deposits range from Alluvial, comprising soft clays, silt and sand to the south east of the route adjacent to the River Deben, to Glacial sand and gravel to the north and Glacial Till to the north east.


88


Cohesive soils (clays) are susceptible to shrinkage/swelling due to changes in moisture content, whereas granular soils (sands and gravels) are not. The magnitude of shrinkage of cohesive soils will depend on the degree to which their moisture content is modified and their specific mineral composition. In general the more clay mineral present, the more shrinkable the clay.


89


By adopting appropriate construction methods that will facilitate continuity of land drainage at all times both during and after construction, the risk of affecting current drainage patterns and therefore shrinkage/swelling of soils , will be avoided. This will prevent significant change in soil moisture content developing. Such measures are to:


ensure that drainage patterns are only interrupted for the shortest possible duration construction


open cut through drains and watercourses as quickly as possible to minimise interference with drainage authority activities


ensure complete and effective restoration of drains and ditches. 90 91


These methods will be developed and agreed with the relevant local drainage authorities.


Construction works will be completed in line with details provided in the Project Description chapter of the ES. Wet or dry construction techniques will be adopted (further details provided in Section 11.5 and 11.6), but in either case the flow of water will be maintained throughout the construction. This will ensure that there is minimal change to surface water flow or to any associated groundwater drainage patterns during and after construction.


92 Wherever possible, the cable trench will be backfilled with arisings, in the order they were originally present. This will ensure that there are no significant changes to the


Outline Code of Construction Practice. Version 3. Page 27


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