There may be a breakthrough in the long-running dispute over reopening the Presumpscot River to sea-run fish.

Sappi Fine Paper, which owns the former S.D. Warren Paper Mill in Westbrook and six dams along the river, had been fighting against state the installation of fish passage at its dams, saying the expense would put jobs and the mill in jeopardy.

The company even went to the Supreme Court last year to argue, unsuccessfully, that states have no regulatory authority over hydroelectric dams. The company has since been facing a possible state order to install fish passage at Cumberland Mills Dam, the lowest dam on the river and one that wasn’t part of the Supreme Court case. Providing fish passage at Cumberland Mills would trigger deadlines to install fishways at its dams upriver.

Now it seems there is a deal that could resolve the dispute. Sappi sent out a press release this week to say it will hold a news conference Tuesday and make a “major announcement on the future of the Presumpscot River.” Among the other groups participating in the announcement is the Friends of the Presumpscot River, the group that has been leading the fight to restore fish runs.

Neither a Sappi spokeswoman nor the president of the Friends of the Presumpscot would discuss the announcement, except to say there is some agreement that involves fish passage at Cumberland Mills Dam. The news conference is schedule for 11 a.m. Tuesday at the Riverbank Park in Westbrook.

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