The town of Edgartown moved this week to formally join the fight against Cape Wind, both out of specific concern about the impact of the project and a broader concern about the erosion of the powers of local government.

On Monday the selectmen authorized town counsel Ronald H. Rappaport to file a motion to intervene in the proceedings before the Energy Facilities Siting Board in support of the Cape Cod Commission and the towns of Yarmouth and Barnstable, which oppose Cape Wind.

The argument centers on whether or not the siting board — a state agency which is charged with ensuring a reliable energy supply — has the power to bundle and grant all the state and local permits needed to build its huge wind farm in Nantucket Sound.

The proponents of the wind farm want the siting board to do just that, as a way of making an end run around local agencies which are holding up the development.

Last fall the Cape Cod Commission denied the land transmission portion of the Cape Wind project, which is planned to come ashore in West Yarmouth. The commission has the power to review that portion of the project as a development of regional impact. When the commission found Cape Wind’s application needed more information, the developers refused to reply. In the end the DRI was denied for procedural reasons, i.e. an incomplete application. Cape Wind then appealed to the Energy Facilities Siting Board.

At issue in the dispute is who trumps whom, since both the commission and the siting board are state agencies.

A similar case was argued a few years ago in a dispute over whether the state affordable housing law, Chapter 40B, was exempt from review by the Martha’s Vineyard Commission.

The commission prevailed in the case.

In their motion on Monday, the Edgartown selectmen cited concerns about the effect of the wind farm on fisheries, commercial fishermen and commercial navigation.

The selectmen also expressed concern that the Cape Wind case could undermine the local review powers of the Cape Cod Commission, Yarmouth and Barnstable and establish a precedent which served to undermine its own powers.

The Martha’s Vineyard Commission also is seeking to intervene, although sources yesterday said the petition still was being drafted.

Both the petitions from the town and the MVC are belated; the deadline for intervention has passed.

The Edgartown petition, however, says there is good cause for this: that many of the potential negative effects of the Cape Wind project did not become clear until March 13, when they were enumerated at a public hearing on the Island.

That hearing, held by the lead federal permitting agency, the Minerals Management Service to get responses to its draft environmental impact statement, saw a large number of objectors, particularly local fishermen who claimed the EIS had grossly underestimated the effect on local fisheries.

The petition from the MVC is expected to address the broader principle of the erosion of the role of commissions like itself and the Cape Cod Commission. Both commissions were created by an act of the state legislature that grants them unique powers to regulate development. The Cape Cod Commission was modeled after the Vineyard commission, which was conceived in 1974.

“The town asserts that the Energy Facilities Siting Board lacks the power to supersede the CCC’s regulatory authority,” the petition says, citing the previous land court decision.

“In the event that the this board concludes that it may circumvent and override the CCC,

The town claims that a decision allowing the siting board to trump the Cape Cod Commission would undermine the authority of the MVC and would be detrimental to the town’s interests.

“The CCC’s mission, as articulated by the Massachusetts legislature and reaffirmed by numerous court decisions — is an express mandate to protect and preserve Cape Cod, and that mandate supersedes and trumps the more limited powers that the legislature delegated to the board,” the petition says.

“Any diminution in the powers of these towns over inherently local decisions would undermine the powers of Edgartown to protect its own environmental resources,” it also says.

And as Edgartown stakes out its opposition to one alternative energy project, it received a double dose of good news this week on another one which it is actively supporting: a plan to generate power from tidal flows in Muskeget Channel between the Vineyard and Nantucket.

On Monday, the federal Energy Regulatory Commission granted 36 months exclusive access to the area to allow initial testing of the financial and technical practicability and environmental feasibility of putting “tide engines” into the channel, to harvest energy from the strong tidal flows there.

The application of a private developer, which had sought exclusive access to the same area, was denied.

Coincidentally the Advanced Technology and Manufacturing Center at the University of Massachusetts at Dartmouth, which is partnering with Edgartown and Nantucket in the project, received word that it had secured $250,000 in grant money toward the work.

“It was a good day,” said Kitt Johnson, chairman of the Edgartown energy advisory committee.

“ We now have our preliminary permit, and the request of the private developer has been denied. We have some money. That’s a tremendous step forward for Martha’s Vineyard and Nantucket,” he said, adding:

“This gives us a period of three years’ exclusive right to do work and be first in line to get a license to operate generating facilities.

“The technology is about 20 years behind wind at this point,” he admitted, “but the aim is to catch up.”

“We have a long journey ahead, but there wouldn’t be any journey at all if we hadn’t won this award.”

The next step is to provide the federal agency with a detailed work plan and a timeline for further work. That must be submitted with 45 days.

One cautionary note. The ruling from the Energy Regulatory Commission sought comments from other agencies, and noted that the federal Department of the Interior had expressed concern the tide engine idea could have significant adverse impacts on fish and other aquatic resources.