What kind of marine wildlife is attracted to electromagnetic fields that emanate from the 30 megawatt undersea cable connecting Block Island to the mainland? The issue came up last week when the Coastal Resources Management Council directed National Grid to study an 80-foot section of the undersea cable that is not buried to the proper depth, and which may attract certain kinds of marine life due to its electromagnetic field.
According to Dave Beutel, the Aquaculture and Fisheries Coordinator for the Coastal Resources Management Council, some marine life native to the Atlantic Ocean “electromagnetic-navigate,” to some degree, as their means of traveling and communication. While this biological impulse is not replicated by an electromagnetic field created by the cable, such marine life as sharks, rays and skates are still attracted to the cable’s EMF.
These cartilaginous fish are known as “demersals,” or fish that live close to the floor of the sea. Studies indicate “that they are [not] strongly attracted to EMF,” said Beutel.
One of the issues that Beutel wanted to clear up right away had to do with sharks suddenly being attracted to Block Island because of the cable.
“One of my concerns is having read some of this stuff and people think of great white sharks. What will attract great white sharks is the seal population,” he said. “The idea that this cable is going to attract great white sharks is just not the case.”
National Grid’s undersea cable carries an “alternating current,” which means that its electrons can travel in either direction. Beutel said that an AC cable “has a smaller EMF field than a DC” – or direct current – “cable. We have an AC cable and the deeper the cable is buried the smaller the magnetic field is.” He said the primary reason for making sure the cable is buried to the proper depth is to better protect the cable. He also said the cable is “only 30 megawatts” and would not emit a very strong EMF.
The 80-foot section of the cable is buried about two feet below the seabed, rather than the prescribed six feet. (The cable is about 20 miles long.) The CRMC has asked National Grid to test this section to see how the EMF can be mitigated. The CRMC said last week that National Grid, as part of the permitting process, was going to have to test the cable anyway but that the process was sped up to address the cable depth and the EMF.
But the primary issue is safety, he said, and protection of the cable. “We want it to be buried to the correct depth and protect it so that it is not exposed in bad weather,” he said.
Beutel said that the East Coast has “AC cables all over the place: Martha’s Vineyard, Nantucket, Vinalhaven (Maine), Newport to Jamestown, and we have not observed any major effects from those cables.”
He did say that wind farms with far more turbines than the Block Island Wind Farm has will require DC cables, which do emit stronger EMFs.
“This issue becomes much more important when a much bigger wind farm project is built,” Beutel said. “They’ll need a DC cable.”
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