The towers Central Maine Power said it is proposing for its New England Clean Energy Connect hydropower line from Canada to Lewiston. This image, looking northwest from Wilson Hill Road in West Forks Plantation toward the proposed transmission line, also contains a photosimulation of five years of vegetation growth that is 10 feet or less in height. Credit: Courtesy of Central Maine Power

Three environmental groups filed a federal lawsuit Tuesday claiming that the Army Corps of Engineers did not fully assess the effects of a controversial $1 billion hydropower corridor and that it coordinated closely with the proposed project’s sponsor, Central Maine Power.

The Appalachian Mountain Club, the Natural Resources Council of Maine and the Sierra Club Maine filed the lawsuit after obtaining a copy of the Army Corps’ environmental assessment, which was completed on July 7 but not released to the public. The report, obtained through a Freedom of Information Act request, found the corridor would have no significant environmental impacts, the groups said.

The project, known as the New England Clean Energy Connect, already has several key permits, including from the Maine Public Utilities Commission, but still is awaiting permits from the Army Corps and others. The 145-mile corridor would take hydropower from the Canadian border through western Maine to the regional power grid. But it passes through 53 miles of largely undeveloped areas that remain a key point of conflict.

The three groups are asking the court to dismiss what they say is a less rigorous July report and require the Army Corps to conduct an environmental impact statement that fully assesses the transmission line’s impact on the environment and communities of western Maine and evaluate CMP’s claims of climate benefits from the power corridor.

“The CMP corridor would permanently fragment valuable wildlife habitat and remove riparian forest cover from hundreds of streams in the last stronghold for native brook trout in the country,” Susan Arnold, vice president for conservation of the Appalachian Mountain Club, said.

She said the Army Corps’ lack of a full environmental assessment is “legally unsupportable.” This level of review was provided to competing projects in Vermont and New Hampshire, she said. The U.S. Environmental Protection Agency had written a letter to the Army Corps in April 2019 asking it to conduct a complete analysis of alternative routes the corridor might take.

Sandra Howard, director of Say No to NECEC, a group that opposes the CMP corridor, said the full scope of this project’s environmental impacts has not been revealed by the Army Corps’ review process.

Army Corps spokesman Bryan Purtell said the Corps has no comment at this time.

John Breed, executive director of the pro-corridor group Clean Energy Matters, characterized the lawsuit as an effort to derail the project.

“After two years, millions of dollars and more than a dozen attempts to use legal action to derail the clean energy corridor, the [Natural Resources Council of Maine] and its allies have yet to succeed,” he said.

The argument of the trio of environmental groups revolves around whether the proposed project would “significantly affect the quality of the human environment.” If it would not have a significant impact, the current Army Corps assessment would be adequate, the groups said.

But if there is a significant impact, as they allege, the fuller assessment is required. The fuller study would include more public input and a deeper analysis of whether alternative routes should have been pursued, along with direct and indirect environmental impacts of the project.

The Army Corps’ analysis in July found that the project did not significantly affect the quality of the human environment. It said it looked at impacts including conservation, aesthetics, wetlands, fish and wildlife values, water supply and conservation and the needs and welfare of the people. It recommended that the Army Corps issue its permit.

Correction: An earlier version of this story misstated the day the lawsuit was filed.