A desk study is the cheapest part of a ground investigation and often the most useful. Before a vessel is booked, it gathers what is already known about the site and turns it into a plan for the field work.
What it usually covers
- Existing surveys: earlier bathymetry, geophysics and borehole logs from the area, including data from neighbouring projects where it can be used.
- Geology: published maps and papers that describe the expected layers, such as soft clays, sands, gravels or rock at shallow depth.
- Hazards: known wrecks, cables, pipelines, unexploded ordnance risk, boulder fields and areas of mobile sand.
- Conditions: water depths, tides, currents, waves and the season when work at sea is most likely.
- Constraints: permits, protected areas, shipping lanes and fishing activity.
The result is a first ground model with its gaps marked, and a proposed survey that targets those gaps. It is also the moment to agree which questions the investigation has to answer for the designers.
Bring the survey team in while the layout can still move. A turbine or quay that shifts a few hundred metres to avoid a buried channel costs nothing on paper.