Offshore wind projects deploy walls of bubbles to protect whales
Dec. 30—GROTON — The sounds generated by industrial pile drivers used to pummel offshore wind foundations into place typically exceed 170 decibels, louder than a gunshot or jet plane accelerating off a runway.
And while the crew members handling the steel-driving equipment are insulated from the work by safety gear and ear protection, the marine mammals in the work areas have no such option.
In an effort to address that discrepancy, offshore wind overseers are embracing the power of bubbles.
On a recent Tuesday morning, the Odyssea Courage, a 70-meter-long offshore supply vessel with a very specific mission, sat docked in Montville's Gateway Terminal, its deck laden with stacks of air compressors and an industrial-sized coil of steel-banded hose.
The ship had just returned from the Vineyard Wind project under construction 15 miles off the coast of Massachusetts where crews were in the process of pounding enormous micropiles into the seabed floor.
Those cylindrical bases will be slotted with wind turbines — 64 in all — expected to eventually generate enough electricity to power more than 400,000 New England homes.
The process of banging each micropile into place doesn't take long, just a couple blows over the course of about 90 minutes from what's essentially a huge, weighted hammer.
But it is violent.
"It's extraordinarily loud across the entire frequency spectrum," said Richard June Hine, president of offshore energy for the Groton-based ThayerMahan company. "And that noise is happening in an environment where marine life can be disturbed."
And that's where the Odyssea Courage and its load of hoses and compressors comes in.
ThayerMahan has exclusive rights to use proprietary "big bubble curtain" technology developed years ago by the German Hydrotechnik-Luebreck company to mitigate the effect of noise generated during offshore wind farm construction.
"The concept is simple," Hine said during an interview this month. "Sound travels through water very rapidly — much more effectively than air — but when a soundwave hits something like a bubble curtain, it basically bounces off and the decibel level drops."
To create that dampening barrier, crews drop two rings of weighted, rubber hose down 150 feet around a micropile site about an hour before pile-driving begins. Once the concentric rings of hoses are placed, an array of 20 air compressors on the ship send air through the perforated tubes just before the steel turbine foundations are slammed into place.
The compressed air leaves the hoses as bubbles that expand as they rise to the surface, creating a "wall of air" that Hine said absorbs 90% of the pile-driving noise.
Protecting marine life
The waters surrounding New England offshore wind sites, including Vineyard Wind and the South Fork Wind project off Montauk Point, are regular migration routes for schools of endangered North Atlantic right whales which travel through New England waters and further north to feed and mate.
The mammals are one of the most endangered large whale species, with fewer than 360 remaining, according to the National Oceanic and Atmospheric Administration Fisheries, the federal agency tasked with the stewardship of U.S. marine resources.
Major threats to the population include fishing gear entanglements, vessel strikes, climate change and ocean noise.
"Ocean noise from human activities such as shipping, boating, construction, and energy exploration and development has increased in the Northwest Atlantic," NOAA states on its webpage. "Noise from these activities can interrupt the normal behavior of right whales and interfere with their communication."
Those sounds may also reduce the whales' ability to detect and avoid predators, and human hazards and interfere with the mammals' ability to navigate, identify physical surroundings, find food and mates.
The agency noted the presence of wind turbine foundations may change oceanographic and atmospheric conditions to the point of altering the formation of the dense patches of plankton on which the whales feed.
An unsettling number of recent whale deaths
In an October 2022 report released by NOAA and the U.S. Department of the Interior's Bureau of Ocean Energy Management, or BOEM, on the intersection of offshore wind and North Atlantic right whales, the agencies raised concerns that ocean noise could reduce the mammal's calving rates and lead to a jump in disease and predation.
The report found 230 right whales have died since their population peaked at 481 in 2011.
"Human-caused mortality is so high that no adult (right whale) has been confirmed to have died from natural causes in several decades," the report stated, noting most of those deaths were attributed to vessel strikes and entanglements.
The report noted the whales' habitats overlap with offshore wind projects in the Northeast and listed four "primary stressors" to whales, including exposure to noise and/or pressure; entanglements related to changes in fishing activities; increased risk of vessel strikes; and changes in habitat.
The groups specifically mention the benefits of "quieting the oceans," during offshore wind project construction.
"For example, when activities such as pile-driving cannot be avoided, pile-driving quieting-technology should be used," the report concludes.
Enter ThayerMahan.
"Two ex-submariners"
When the company was founded in 2016, it's primary mission was to provide monitoring services to the defense industry, a field its two founders, Hine and Chairman and CEO Mike Connor, were very familiar with.
"We're two old ex-submariners who formed a company initially to assist the Navy with autonomous sonar system work," Hine said.
Hines said the Hydrotechnik-Luebreck firm, creator of the noise-dampening technology used in the European offshore wind projects, reached out to his people with a proposal to allow ThayerMahan to become the "exclusive provider" of the system in the U.S.
"It's a dream scenario," Hine said. "We sent our people to Germany to train and our people come back and train union members in the work. Right now, two-thirds of the (bubble curtain) work at Vineyard Vines is done by unions members with others being our supervisors. And all our work is centered in Connecticut."
In addition to the bubble curtain system, which the company hopes to use during construction of the upcoming Revolution Wind project, the company also deploys its monitoring gear to locate, track and classify the whales swimming near the offshore wind sites.
"If we hear a whale, we assume it's a right whale and construction is shut down," he said. "But we're able to be very precise and cut down on the false positive alerts. It turns out we can hear whales as good as we can Russian subs."
