Offshore site investigations

Just as you would survey the land and soil before building a home, offshore wind developers survey the seabed and geology in lease areas and along proposed cable routes, before building an offshore wind farm.

Prior to construction, offshore surveys use a variety of small nearshore and larger offshore vessels to acquire information for permits, applications and to help inform project design. We map the underwater habitat to minimize any impact the project might have on marine life and archaeological resources.

Two of the most common types of pre-construction survey activities are geophysical and geotechnical surveys. Both surveys require a permit and approval from related agencies. While conducting offshore survey operations, we take the following protective measures:

Vessel speeds

To reduce the risk of interaction with marine mammals and protected species, our survey vessels operate under a 6-knot speed restriction during transit and operations.

Types of offshore survey work
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Offshore geophysical surveys
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We conduct high-resolution geophysical (HRG) surveys to map the seafloor and the geology beneath it, and to identify archaeological resources and debris left by other ocean users.

Equipment used during these surveys includes both acoustic equipment using varying frequencies of sound and passive sensors that do not emit sound. The sensors are either hull-mounted or towed above the seafloor behind the vessel. During HRG survey operations, vessels typically move at a low speed, between 2-4 knots (3-5 mph) transiting along straight survey lines.

The sources used in offshore wind that are detectable produce much lower energy and travel far shorter distances from the vessel than those used by the oil and gas industry for exploration miles below the seafloor.

Offshore Geotechnical Site Investigations

Geotechnical Site Investigations (GTSIs) collect data from below the seafloor to assess the mechanical behavior of soil and rock. We take measurements of soil properties, along with physical soil and rock samples, which we send for laboratory testing onshore. GTSIs do not produce any significant acoustic noise and therefore don’t pose a risk to marine mammals .While undertaking GTSIs, the vessel remains stationary on-site.