This month, we expect Orsted to begin site investigation work for both projects, which will include geophysical surveys and geotechnical surveys.
The details
As part of due diligence and since Orsted must bury cables according to international best practices standards, we need to study the ocean floor using two methods of site investigation work – geophysical surveys and geotechnical surveys.
According to representatives, the geophysical surveys will be performed by two vessels operating echo sounder equipment that use sound waves to basically take a picture of the ocean floor. These surveys are non-intrusive and will not disturb the ocean floor. They are looking at the contours of the ocean floor while attempting to identify such things as large rocks, debris, and other potential obstacles. The geophysical survey vessels will work during the day and return to port at night.
Geotechnical surveys will be performed by two other vessels which will take borings of the ocean floor to check the composition of the soil for the purpose of gauging the burial depth of our cables. The vessels’ equipment will bore holes that are about 3-4 inches in diameter and about 18 feet deep. Each of these borings will be a little over a half mile (one kilometer) apart. Though the geotechnical vessels will anchor off shore at night, their surveys will only be done during the day.
During both the geophysical and geotechnical surveys, the only noise that should be heard would be the vessels’ engines.
Each of these vessels will travel at roughly 3 to 5 miles per hour (3 to 4 knots) while performing the surveys. Operating at this speed allows the vessels to operate safely around other watercraft and to keep noise levels to a minimum and avoid harming wildlife.
The survey work will occur in three distinct survey areas.
Within the first area, one geophysical vessel and one geotechnical vessel each will survey off Monmouth County in roughly a rectangular shape between 450 feet and three nautical miles off the coast.
In the second area, another geophysical vessel and another geotechnical vessel each will operate at least three nautical miles off the coast from Monmouth, Ocean, Atlantic, and Cape May Counties.
In addition, we will have a scout vessel in operation to assist with avoiding commercial fishing gear in the water.
In the third area, a geotechnical vessel will be in the Barnegat Bay along with an amphibious crawler (a machine specifically designed to minimize impact to vegetation and other sensitive seafloors.) This work will be done closer to shore between the mainland and Island Beach State Park and just offshore of the park.
Mariner’s Briefings are available for Mid Atlantic updates, please see the planned survey activity and the vessels performing the work.
