Vineyard Wind, the company that plans to build a massive offshore wind farm south of the Vineyard, won approval from the Martha’s Vineyard Commission Thursday night for its undersea cables that will transmit electricity to mainland.

The commission was reviewing the project as a development of regional impact (DRI) because part of the cable will through Vineyard waters off the eastern shore of Chappaquiddick. A public hearing opened in February.

The approval comes with two conditions: the company must return to the commission if it decides to decommission the wind farm, and the commission reserves the right to require a modification if there are unforeseen environmental impacts.

Out the outset of deliberations Thursday night, MVC executive director Adam Turner urged continued oversight of the cables, which will be buried five to eight feet deep about 1.2 miles from the Edgartown shoreline. He said he supports Vineyard Wind, but he expressed doubts that federal agencies including the Bureau of Ocean Energy Management (BOEM) could be trusted to adequately protect the ocean and its wildlife.

“[BOEM] consistently puts the natural environment and sea animals way behind the economic development of energy,” Mr. Turner said. “We are the ones responsible to protect this place, whether BOEM protects it or not.”

Commissioners agreed.

“It may be that evidence comes back that is inconsistent with what their proposal and their testimony said,” said commissioner Joan Malkin of information provided by the company. “If it turns out there are impacts, that would constitute a change.”

Responding to concerns raised during the hearings, Vineyard Wind has promised to share approvals from federal and state agencies with the commission, including a copy of BOEM’s federal environmental impact statement. The company also committed to modifying the cable installation process to protect the North Atlantic Right Whale. In a final offer Thursday night, Vineyard Wind committed to continued monitoring of the benthic habitat to document potential disturbances and recovery.

Based in New Bedford, the company was formed through a partnership between Avangrid Renewables and the Danish company Copenhagen Infrastructure Partners.

The Cape Cod Commission also approved underground cables Thursday in Barnstable. The regional decisions marked a milestone for the proposal, but by no means conclude the permitting process. The project still awaits a sign-off from the Edgartown conservation commission among other local authorities. And multiple state and federal regulatory agencies, most prominently BOEM, still need to grant approvals before the project can begin. In the end, the vote to approve the project was 14-0-1. Clarence A. (Trip) Barnes 3rd abstained, citing concern for wildlife.

Chairman Douglas Sederholm acknowledged Mr. Barnes’s concerns, but said the conditions are designed to monitor unforeseen impacts.

“I think a lot of this is, we don’t know, but we’re going to keep our hook in.” Mr. Sederholm said.

In other business, Mr. Turner updated the commission on the unexpected partial demolition of a historic home in Vineyard Haven. Known as the Mill House, the home is located on the harborfront near the Vineyard Haven Library. Parts of the house date to 1750 and its history intersects with the Revolutionary War. It was owned by playwright Lillian Hellman from 1955 to 1961.

“It’s definitely sort of iconic,” Mr. Turner said. He said he was called two weeks ago about the possible demolition, and builders were unsure whether the house, which had multiple modifications, still qualified as historic.

“I instructed the building official to not let them do anything and to bring the demolition to the commission,” Mr. Turner said. “Sometime in that period, the building was demolished.”

Mr. Turner said he had since ordered workers to cease and desist, but much of the historic building has already been destroyed. The signature mill tower remains, but it’s condition is unknown.

“This is a major deal. This is a historic house,” Mr. Turner said. “Somebody went around our regulations.”