Construction work on the Sheringham Shoal Offshore Wind Farm site begins today (Tuesday, March 9), with the arrival of the 164m Nordnes vessel, which will position rocks at selected foundation locations in preparation for the start of the installation of the giant monopile structures next month.
Using a precision technique, the Nordnes will place 2-9" filter rocks in a 'donut' shape around the site of 77 of the 90 foundation locations to reduce the likelihood of scour and protect the cables when they are installed.
Scour protection is needed for wind turbine foundations, as well as other types of marine structures, due to changes in water flow patterns that may cause a lowering of the seabed immediately surrounding them.
Dutch company Van Oord has been contracted to carry out the filter layer work which will be the first stage of a two phase process. In the second phase, larger rocks will be placed in the same pattern to act as armour to the filter layer after all the foundations have been installed. The appointment of the contractor to undertake the armour layer works has yet to be decided.
Project Director Rune Rønvik said that the arrival of Nordnes on the site of the wind farm means construction work has officially started on site.
"This work will prepare the site for the arrival of the first foundation for installation at the end of next month. Each foundation is made to individual specifications and will be between 50 and 55 metres long, with a 4.2-5.2m diameter and weighing from 400 to 600 tonnes," he added.
The Nordnes will be on site at Sheringham Shoal, between 17 and 22km off the coast of North Norfolk, until March 18 when it will return to Norway to collect its second load of rock. It will arrive back in the Greater Wash on March 22, working until March 30. The final rock placement for the Filter Layer work will be completed around early June 2010.
The Sheringham Shoal Offshore Wind Farm is owned equally by Statoil and Statkraft through the joint venture company Scira Offshore Energy Limited. Statoil is the operator for the project during the development phase. Scira will be the operator of the wind farm.