WEST FORKS — Central Maine Power Co. plans to permanently conserve about 50,000 acres in northern Somerset County, a major step needed to comply with state demands and mitigate the environmental impact of its long-litigated transmission line through rural western Maine.

CMP plans to finish building the high-voltage transmission line, named the New England Clean Energy Connect, by the end of this year but needs approval from state regulators on this proposed conservation area before the line can begin operating.

The NECEC project would connect a Canadian hydroelectric plant to a converter station in Lewiston using an existing corridor that, until this proposal, only went as far north and west as The Forks.

The new stretch of transmission lines, called Segment 1, will wind a 53-mile path through a remote, wooded area — a prospect that several environmental groups immediately challenged when the project was proposed in 2017.

LONG ROAD TO POWER

The initial proposal from CMP’s parent company, Avangrid, called for transmitting 1,200 megawatts of power from Hydro-Québec’s dams through Maine to provide clean energy to Massachusetts customers. Massachusetts had passed a law in 2016 calling for its public utilities commission to seek out new clean energy sources, and Avangrid’s NECEC project won one of the bids.

Almost immediately, Maine-based environmental groups said the project would have serious impacts on habitats, scenery and natural resources. And after a 29-month permitting process through the Maine Department of Environmental Protection, state environmental regulators largely agreed, saying Avangrid needed to do much more to preserve the landscape and habitat.

As the project moved through the permitting process, residents and environmental groups called for a statewide referendum to kill the project by making such transmission lines subject to approval by the state Legislature. The referendum applied retroactively to 2020 to make sure it prohibited the NECEC project.

Combined, the sides spent more than $100 million during the campaign — setting a new spending record for a ballot question in Maine. Mainers voted decisively to kill the project in the November 2021 referendum.

Years of legal challenges ensued.

First, Avangrid challenged the referendum itself, arguing retroactive application was unconstitutional and violated the due process and vested rights of Avangrid. The Maine Supreme Court agreed and allowed the project to move forward.

Then, environmental groups challenged a lease of about a mile of public land for the project, saying it constituted a substantial change to the land and therefore required a two-thirds majority of the Legislature. The Maine Supreme Court again sided with Avangrid and allowed the lease.

Environmental groups also sued federal permitters over their environmental analysis of the transmission line. That challenge was finally rejected in April.

The DEP officially approved the transmission line project in 2020, but with dozens of conditions intended to mitigate “substantial impacts” from the line, including stipulations on the width of the corridor, tree heights and ensuring habitat connectivity.

“These conditions provide an unprecedented level of natural resource protection for transmission line construction in the State of Maine,” the DEP said in its 239-page permit for the project. “They are also fully supported by the evidence.”

Regulators also ruled the line would not be allowed to operate until CMP created a 40,000-acre conservation area nearby. After appeal from environmental groups, that acreage was increased to 50,000.

“This is a critically important condition within their permit application,” said Pete Didisheim, the advocacy director for the National Resources Council of Maine, a group that has challenged the project from the beginning. “They are required to meet a pretty high bar for this 50,000 acres.”

In the meantime, CMP will continue building the line. Spokesman Jonathan Breed said the company plans to finish construction by the end of the year.

WHAT NOW?

CMP plans to acquire the 50,000-acre conservation area from Weyerhaeuser Co. — a lumber company and one of the largest private landowners in the United States — for an unspecified fee.

The newly conserved land would be administered as a conservation easement by the Maine Bureau of Lands and Parks and connect directly to 400,000 permanently conserved acres, creating one of the largest contiguous conservation areas in the state.

Public access to the land will be guaranteed in perpetuity, Maine Department of Agriculture and Conservation and Forestry spokesperson Jim Britt said.

“Avangrid will also establish an endorsed legal defense and management fund for the conservation easement’s future use,” Breed said in an email. “The proposed conservation management plan will endure beyond the life of the NECEC transmission line project.”

CMP submitted its conservation plan for the area to the Department of Environmental Protection May 9, and the agency is taking public comment on the plan until June 13.

Regulators will then decide if the conservation plan meets the agency’s requirements. If it doesn’t, CMP could appeal or submit another plan — perhaps for a different 50,000-acre plot. Regardless, if the plan is shot down, CMP would likely not be able to begin operating the transmission line on the scheduled end of 2025 timeline.

The Natural Resources Council of Maine plans to submit its own analysis of the plan to the MDEP during the public comment period. Didisheim said the group has already reached out to the state’s preeminent forestry and environmental experts to evaluate the plan.

“Very high on people’s mind is the requirement that these these lands be managed for mature forest and habitat connectivity, and for wildlife conservation and wildlife habitat,” he said. “We’re looking very closely at their definition of what a mature forest is. We’re looking very closely at what their definition is of habitat type that is supportive of wildlife.”

Didisheim said he is especially concerned about the maturity of the forest, since from aerial imagery much of the lumber in the area appears to have been recently harvested. He said the ecological value of the conservation area could be substantially limited by that recent and potentially ongoing forestry work.

The Department of Environmental Protection required that the conservation area focus on preserving mature forest habitat, but did not provide a specific definition of what such a habitat would look like.

“It’s a working forest that has substantially diminished wildlife habitat (and) the range of species that can find mature forest stands,” Didisheim said. “It limits some of the ecological values on that landscape.”

CMP’s proposal estimates about 40% of the trees in the conservation area are taller than 35 feet and only 13% are taller than 50 feet. By 2065, the proposal says, about half of the trees in the zone would at least 50 feet tall.

“Achieving 50% in the 50-foot age class by 2065 and thereafter in perpetuity represents a substantial change in management practices, and a substantial improvement in wildlife habitat that will endure beyond the life of the NECEC Project,” the proposal says.

Until the state regulators reach a decision on the conservation area, the battle over the NECEC line continues. And even if the plan is denied, CMP could appeal to the Board of Environmental Protection or a district court.