LEWISTON — Whether Central Maine Power should get permission to construct its proposed 145-mile electrical transmission line between Quebec and Lewiston drew sharp comments Wednesday during a session sponsored by the Sierra Club at City Hall.

The $950 million project would deliver power generated by Hydro-Québec to users in Massachusetts if it wins approval from regulators in Maine, Massachusetts and Washington.

Though critics said the power-line corridor through the Maine woods would harm the state’s natural environment and crimp sight-lines in one of the most scenic areas of New England, proponents said it’s a necessary step toward a carbon-free future.

The Sierra Club, which opposes the project, pulled together CMP officials with some foes of its plans to explore the ins and outs of the controversial plan that has stirred up environmentalists but secured solid support in Lewiston, which stands to gain about $5.5 million in extra property tax revenue annually if the line is built.

Carl Sheline, chairman-elect of the Lewiston Auburn Metropolitan Chamber of Commerce, said people have to understand there are trade-offs to everything. Overall, he said, the project would be a benefit.

The project calls for “cutting down a minimal swath of land” to construct a line that would bring more electricity to a region that struggles with supply on the coldest and hottest days — and help move New England toward a future that does not rely on oil and natural gas, Sheline said.

Dot Kelly, a Sierra Club official in Maine, said she would rather see more emphasis on solar, wind and battery-storage technology.

She said the proposed power line is “not a horrible project, but it has been done maximizing profit,” instead of minimizing the negative impacts.

Jeremy Payne, executive director of the Maine Renewable Energy Association, said it is has “pretty significant concerns” about whether the plan will stymie the growth of new green power producers in Maine by tying up transmission capacity.

Critics complained about plans to have the power line cut across the Kennebec River at its forks, just past its spectacular gorge. They also questioned the need to have the line slice through wilderness through the western Maine mountains.

The project “is going to bisect Maine,” said Sue Ely, a lawyer for the Natural Resources Council of Maine, adding 53 miles of lines with towers marring the view of the north woods and likely harming wildlife.

David Publicover, senior staff scientist for the Appalachian Mountain Club, said that much of the new corridor eyed by CMP through the mountains could be underground, including the portion set to cross above the Kennebec River in an area he called “a truly special place.”

The impetus behind the project is an effort by Massachusetts to shift more of its power use to green sources to combat climate change, said Thorn Dickinson, vice president of business development for Avangrid, CMP’s corporate parent.

The region has already committed to reach carbon neutrality by midcentury, a goal that is extremely ambitious, said Bruce Phillips, director of the Massachusetts-based consulting firm The Northridge Group.

Phillips said that solar and wind — the two best-known sources of carbon-free power — provided only a little more than 3 percent of New England’s power in 2017.

Even pushing ahead on every front toward increasing that number, he said, the likelihood of reaching the target in a few decades is iffy. But throw in CMP’s project and a few other initiatives and the odds increase from 59 percent to 95 percent, Phillips said.

No matter what, he said, “it’s going to take an enormous build-out” to replace the existing system in such a short period.

But climate experts insist that time is running out to cease dumping millions of tons of carbon dioxide into the atmosphere each year, a long-running problem that is heating up the planet and beginning to have serious consequences that include flooding and the extinction of species.

“There is only one opportunity to get this right,” Phillips said, and the CMP project is part of a necessary push to cope with the threat.

Lincoln Jeffers, Lewiston’s director of economic and community development, said the project offers “enormous money” to the city’s coffers because it includes a $250 million converter station that will draw in direct current from Hydro-Québec that’s traveled down the line from Canada and convert it to the alternating current used in the United States.

Even without that, he said, the project is “a good, strong step” toward dealing with the dangers of climate change and ensuring a reliable supply of electricity in the future.

It’s important to recognize, Jeffers said, that “we like to flip the light switch and have the power come on.”

Ely said there are better ways to draw the Quebec power into New England that do not require tearing up part of Maine’s wilderness.

Thorn said CMP agrees there are alternatives and pointed out that his company proposed half a dozen of them in its other submissions to Massachusetts in its bid to get a contract. There were “all sorts of creative ideas,” he said.

Massachusetts regulators who considered all of them wound up picking the new line through Maine that was one of CMP’s proposals, he said. So it is the one that is moving forward.

If regulators give it a green light, construction could begin in late 2019 and finish in 2022.

scollins@sunjournal.com.