The Dudgeon Offshore Wind Farm is a 402MW facility being constructed 20 miles off the coast of the seaside town of Cromer in North Norfolk. Power from the 67 turbines is being routed via buried cable being installed across 47 km of North Norfolk to a new substation at Necton. Although construction consents for the wind farm have been in place since late 2012, concerns about the impact of the cable connection on agricultural land result in the imposition of a planning condition requiring a detailed soil management plan for the route.
Royal Haskoning DHV, acting for the Norwegian energy companies Statoil and Statkraft, retained LRA to undertake a detailed soil survey along the route and produce a soil management plan designed to guide the programming of cable installation and minimise erosion and damage to agricultural soils. Having authored the Construction Code of Practice for the Sustainable Use of Soils on Construction Sites for Defra, LRA was well qualified to undertake the commission.
Survey work was carried out over winter 2013/2014, involving detailed investigation of topsoil, subsoil and substrate characteristics at 100 m intervals along the whole route. In situ thermal conductivity measurements were also made every 200 m at 1.1 m depth and were interpreted to assess the risk of cable-induced soil warming changing the distribution of moisture in the subsoil or influencing the rooting depth of agricultural crops.
The soil management plan, finalised in spring 2014, included maps indicating land access restrictions on different sections of the corridor to avoid soil damage due to traffic and groundwork during wet conditions, recommendations on measures to avoid soil erosion, and recommendations for soil stripping, handling, storage, reinstatement and aftercare methods, including a compliance monitoring regime.
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