Gardline Geosurvey carried out an ultra high resolution seismic survey for SCIRA-Norsk
Hydro on the Sheringham Shoal off the North coast of Norfolk, UK. The object was to
investigate the depth to the top of the Chalk and the stratigraphy of the Quaternary
sediments, and furthermore determine any hazards and/or constraints to the
emplacement of the 88 to 108 proposed wind turbines for the Scira Windfarm, using
single beam and multi-beam echo sounder, sidescan sonar, pinger, boomer and mini
airgun equipment. Positioning control for the survey was the Fugro Starfix and Subsea7
Veripos DGPS services.
The scope of work, as defined by the contract, called for seabed and geological
information with which to identify hazards and constraints to aid in the planning of a
geotechnical borehole campaign later in 2007; planning and engineering of piles for the
foundations of the turbines; and, finally, to aid the detailed design of the turbine grid and
positioning of support installations. Particular emphasis was placed on identifying the top
of the Chalk within the survey area.
The survey was conducted over a site that has a rhombic shape oriented with the outer
long side following the 12nm boundary. The long sides and the short sides are
approximately 7.65km and 6.47km respectively.
The Sheringham Shoal Windfarm Site is located approximately 17km to 23km offshore
from the North Norfolk coastal town of Sheringham and approximately 5km north of the
offshore sand bank known as Sheringham Shoal.
The survey line grid was completed as planned.
The following contractor and client representatives were present on board the survey
vessel.
Gardline Party Chief J Bulstrode
Norsk Hydro Representative R Lien, H Johansen, S Eidsvig
Fisheries Representative J Lingwood
This report describes the seafloor conditions and the geology around the Sheringham
Windfarm site. Potential installation hazards have been evaluated and special attention
has been given to the following:
• Presence and distribution of shallow gas
• Existence of boulders
• Seabed features, such as sand waves, cables, wrecks, items of debris, etc.
• Shallow stratigraphy and lithology
• Identification of the top of the weathered Chalk.