Geophysical surveys establish sea floor bathymetry, sea bed features, water depth and soil stratigraphy, as well as identifying hazardous areas on the seafloor and human-made risks such as unexploded ordnance (UXO).

What it costs

About £1.1 million for a 450 MW floating offshore wind farm.

Who supplies them

Acteon, Argeo, Fugro, Gardline, G-tec, Horizon Geosciences, Magseis Fairfield, MMT, PanGeo Subsea, TGS and Sulmara.

Key facts

Geophysical surveys are non-intrusive and include remote sensing techniques such as seismic methods, echo sounding and magnetometry.

The techniques used consist of bathymetry (water depth) mapping with conventional single or multibeam echo soundings or swathe bathymetry, sea floor mapping with side scan sonar, magnetometer for UXO, acoustic seismic profiling methods and high-resolution digital surveys.

Surveys run along transects across zones within the proposed floating offshore wind farm site and cable routes.

Information from geophysical surveys is used to aid the design and implementation of the benthic and geotechnical surveys, so they are often undertaken near the beginning of the development process.

Data from geophysical surveys are also used to produce charts, models, and maps for GIS systems, which are then used for site layout design.

Geophysical surveys can be used to identify UXO on or below the sea bed. Geophysical surveys may also consider marine archaeology that may be present in the floating offshore wind farm site. This is typically dealt with by specialist archaeological survey companies and is offered as a service in conjunction with geophysical surveys.

Guide to a Floating Offshore Wind Farm