The U.S. Army Corps of Engineers issued a new environmental review of the $1-billion Central Maine Power New England Clean Energy Connect hydropower transmission corridor in Western Maine on Nov. 4 that its developer says will allow work to begin in December on what will be a 145-mile transmission link to Canadian hydroelectric sources.

The approval comes days after three opponent groups filed suit in US district ourt, claiming the Corps assessment is not thorough enough.

In an Oct. 27 lawsuit in U.S. district court, three environmental groups—the Appalachian Mountain Club, Natural Resources Council of Maine and Sierra Club of Maine—challenged the Corps for failing to strictly evaluate the environmental effects of the 53-mile corridor as it did for similar projects in New Hampshire and Vermont. The line will travel through the three states to move hydroelectric power from eastern Canada to the New England grid in Lewiston, Maine under a contract with Massachusetts Utilities.

The Corps assessment and “finding of no significant impact" was completed on July 7 but not made public and obtained only by the organizations through a Freedom of Information Act request.

The groups said the Corps, by choosing not to conduct a fuller Environmental Impact Statement as federally required, had “abdicated its responsibility to assess the full impacts" of the proposed line, particularly the segment through Maine’s Western Mountains region.

While the project will be funded by Massachusetts ratepayers, it is expected to benefit the region by reducing greenhouse gas emissions.

The project still needs a permit from the the U.S.Energy Dept. to cross the U.S-Canada border as well as approvals from some local municipalities

Avangrid, the parent company of Central Maine Power, said the favorable environmental review clears the way for construction to start on land "owned or controlled" by the power firm. The company already has announced more than $300 million of contracts to build the project and anticipates 1,600 workers employed, and says when completed in about 30 months, the line will be New England's largest source of renewable energy.

"The Army Corps’ decision is a slap in the face to all Mainers," said Nick Bennett, Natural Resources Council chapter staff scientist. "The evidence and testimony presented to the Army Corps made it clear that the CMP corridor is not in the public interest and is opposed by an overwhelming majority of Maine people."

Meanwhile, efforts to mount a new referendum aiming to stop the corridor project collected 23,000 signatures on Election Day to place the issue on 2021 state ballots, said Sandi Howard, director of Say No to NECEC, a grassroots non-profit in Maine in a Facebook post.

The group had collected more than 63,000 signatures in an earlier effort this year that got the initiative placed on 2020 ballots, but the Maine Supreme Judicial Court ruled that such a referendum could only be used to nullify legislative decisions, not regulatory ones.

The new referendum calls for legislative approval of transmission lines that exceed 50 miles and bans high-impact transmission lines in Maine's Upper Kennebec region.

CMP claims the initiative is written so broadly that it could hurt other projects in Maine and the state's push for more renewable energy,