A bill from Sen. Brownie Carson, D-Harpswell, that would study the emissions impact of the proposed Central Maine Power corridor is scheduled for a Tuesday vote in the House.

AUGUSTA, Maine — A bill that would complicate state permitting of a $1 billion Central Maine Power hydropower transmission corridor through western Maine handily won support from the Senate on Thursday.

The bill from Sen. Brownie Carson, D-Harpswell, would mandate an independent net carbon emissions impact study of the proposed 145-mile transmission line to send Hydro-Quebec power from Canada to Massachusetts. It earned more than two-thirds majority from senators, who endorsed it 30-4. Two Democrats — Sens. Bill Diamond of Windham and Senate Majority Leader Nate Libby of Lewiston — joined Republican Sens. James Hamper of Oxford and Kim Rosen of Bucksport in voting against it.

“This project has stirred up strong opposition from citizens and communities statewide,” Carson said Thursday on the Senate floor. “Many believe this project must be questioned … [they] want to know if the claims about the project being good for the climate are real.”

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The bill has become a flashpoint for Democratic and Republican lawmakers who oppose the corridor and are skeptical that it would reduce carbon emissions — a perspective at odds with Gov. Janet Mills, who threw her support behind the project after CMP offered a 40-year, $250 million benefits package. Last month, Mills said the project will bring “well-documented and substantial reduction of carbon emissions.”

Mills spokesman Scott Ogden said Mills is “interested in working with lawmakers on both sides of the issue on productive legislation” related to the project, but he said the governor “has concerns” about Carson’s bill “that she will share with lawmakers as the Legislature continues to consider it.”

A report last year found the corridor would reduce greenhouse emissions at a rate equal to removing 767,000 cars from roads across New England, but a study completed by project opponents said the contract doesn’t necessarily prevent hydropower from being replaced with electricity from more emission-heavy sources.

Carson’s bill calls for the study, conducted by a non-government agency, to be completed by Aug. 15. Meeting that tight deadline is further challenged by the fact that funding for the study remains in question.

[ How CMP’s $1 billion hydro project could affect habitat in a wild corner of Maine ]

Libby was the only senator to speak against the measure on the floor before Thursday’s vote. He said that the Department of Environmental Protection is not equipped to oversee the study on such short notice and that its potential to disrupt the project’s construction timeline could negatively affect his constituents in Lewiston.

As an emergency bill, passage is contingent on receiving two-thirds majority support in both chambers. It now moves to the House for a vote there, most likely next week.

Though Mills has expressed doubt about the need for Carson’s bill, it is unclear if she would veto the measure should it reach her desk.

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