2011, PLA Hydrographic Service, Gunfleet Sands 1 and 2, Export Cable and Wind Turbine Inspection Surveys (Summer 2011)

Description

The Port of London Authority (PLA) Hydrographic Service was commissioned by DONG Energy to undertake repeat Multibeam Echosounder (MBES) and Side Scan Sonar (SSS) surveys at the Gunfleet Sands Offshore Windfarm in the Thames Estuary. The previous survey having been undertaken during March 2011 – PLA Reference 113-500-142 Contract Q15/10. The surveys are required for the FEPA Licence Numbers: Gunfleet Sands 1 31919/09/0 and Gunfleet Sands 2 33723/09/0. The scope of work was as undertaken in 2010 which included: 1. MBES and SSS survey of 100m wide corridor along Export Cable Route between the windfarm substation and landfall site, to the east of Clacton-on- Sea. 2. MBES survey the seabed of an area 2400m x 100m around and between six adjacent turbines, namely A6 to F6. 3. For 2011, a requirement for additional works and analysis identified by DONG Energy, namely:- Volume calculations at each of the six turbine sites, difference surface charts at each turbine site, difference surface along export line, and comments on wider area geomorphology and bathymetric changes. 4. For August 2011 the scour around the substation was assessed and compared against previous surveys. This series covers survey elements which were undertaken on the 30th and 31st August 2011 around turbines A6-F6, and along the Export Cable Route. The survey work was carried out using the PLA survey vessel ‘Yantlet’, with bathymetric data being collected using a hull-mounted Reson SeaBat 8125h MBES and SSS extracted from the bathymetric data in the form of snippets and backscatter.