AUGUSTA, Maine — The administration of Gov. Janet Mills revised a lease at the center of Central Maine Power’s corridor proposal on the same day a lawsuit was filed raising questions about the state’s ability to unilaterally allow changes to public lands.

CMP will now have to pay $65,000 a year to use a 300-foot wide, one-mile stretch of land in the West Forks Plantation area that the power line will pass through, according to a June 23 lease between the Maine Bureau of Parks and Lands and the utility. That is up from just under $4,000 under a 25-year lease finalized in 2014 under former Gov. Paul LePage.

A lawsuit filed on the same day by opponents of the project over the earlier lease is one of several affecting the $1 billion project as it faces a referendum in November that could serve as a rebuke of the powerline. The corridor looks to be widely unpopular but is backed by politicians — including Mills and LePage — who have defended it from legislative challenges.

While the ballot challenge could be unconstitutional, the lease lawsuit could provide opponents with a way to doom the project. It focuses on a part of the Maine Constitution requiring a two-thirds vote from both legislative chambers to “reduce” or “substantially alter” public lands.

The revision from the Mills administration at least partially acknowledges concerns over the lease raised by opponents. The issue was aired publicly in February, when a state planner told a legislative panel he did not know what the land would be used for when working on the lease under the LePage administration and did not consult the law, according to Maine Public.

Mills, a Democrat, may face the same question over legislative approval. Spokespeople for her administration did not answer questions about that on Tuesday. The new lease was first reported by Maine Public.

Jim Britt, a spokesman for the Maine Department of Agriculture, Conservation and Forestry, said the state “inherited an undervalued lease agreement” finalized under LePage, a Republican. The new lease “is in line with the fair market value of nearby properties” and “represents a substantial improvement for the people of Maine,” he said in an email.

The state’s effort to address some of the problems with the project at least partially makes opponents’ case for them, said former Maine Senate President Rick Bennett, R-Oxford, who is running for a return to the chamber in 2020 and is a plaintiff in the lawsuit against the lease led by the Natural Resources Council of Maine.

“This is an attempt to cure some of the statutory problems, but it really underscores the main issue, which is that this is a substantial altering of the lands, which requires a two-thirds vote,” he said. “It weakens their position rather than strengthens.”

The original 25-year lease in 2014 included an annual payment of $1,400, which was revised to $3,680 the following year, according to the lawsuit. Plaintiffs allege the company was not paying a fair market rate for the land under the old lease.

The new lease will last the same length of time and requires CMP to get the land appraised within a year, something that never happened with the first lease, according to the lawsuit. If the appraisal comes in higher, the lease will be amended to reflect the new cost. The annual payment will be adjusted each year according to changes in the Consumer Price Index.

BDN writer Michael Shepherd contributed to this report.