As construction of the new state prison in Warren begins, the town of Thomaston, long the home of the Maine State Prison, is staring down the pipe of a $100,000 revenue loss for its waste treatment plant. That’s how much the state pays the town to process 22 million gallons of sewage from the Maine State Prison each year. But the aging prison is soon to be replaced by a $68.4 million prison to be built in nearby Warren, on ground near the new Supermax.

In 1997, Thomaston opened a $6 million waste treatment plant, built in large part to comply with state mandates that towns stop dumping partially treated sewage into the state’s rivers, and in part to help handle the flow of waste from the 430-plus inmates at the prison. Without the Maine State Prison’s waste, town leaders claim, the 700 remaining customers on the line could face a doubling of their sewage bills.

That’s why Thomaston wants to build a waste pipeline from the new prison in Warren, back to Thomaston. Locals there claim doing so would prevent Thomaston from losing too much waste-treatment revenue. But there may be a better, certainly an easier, way.

Thomaston claims its system has produced a cleaner St. George River and led to the opening of clam flats and improved fisheries on the river. But Warren officials say their system can handle waste made by the new prison and already treats waste from the Supermax and Bolduc Farm detention centers that are located there.

Here’s a case where the state has to face, directly, the problems of noble policies creating significant conflict. Everyone wants clean rivers; and there’s no question that the new state prison is desperately needed. Someday, Warren will have to upgrade its sewage treatment to be as environmentally friendly as Thomaston’s; but how can it do so without the help of new user fees? And if those user fees go to Warren, what does that do to Thomaston, which acted in good faith to meet state needs on at least two levels?

If this were a question of a different utility — electricity rather than sewage, the answer proposed would be an exit fee, a charge paid by the departing user in recognition of the cost it alone generated on the system it is leaving. As suggested months ago, something similar might be appropriate here, with a third-party auditor assessing a fair share to be paid by the Department of Corrections to Thomaston.

An exit fee properly recognizes the state’s demand on Thomaston, allows residents there to afford the larger system and could well be cheaper than a pipe between communities.