Montpelier — Lawmakers will soon get a report on whether Vermont should purchase a series of hydroelectric dams along the Connecticut and Deerfield rivers. In the meantime, they’re discovering that the next owners of the dams will be under heavy pressure to address a range of environmental concerns.

Power produced by large-scale hydroelectric dams is considered renewable energy, according to Vermont law. But that doesn’t necessarily mean it’s good for the environment. Connecticut River Watershed Council Executive Director Andrew Fisk told lawmakers last week that if the state of Vermont wants to purchase the dams, then it better be ready to take on the environmental responsibilities that will come with them.

“Our interest is in, whoever owns those facilities is going to operate those in such a way that the ecological footprint is as small as possible,” Fisk said.

Five of the 13 dams put up for sale by international energy giant TransCanada are up for state and federal re-licensure in the next few years. Fisk said prospective buyers need to understand that getting those licenses will require some changes to the business model.

“If you are looking at this, I would say with a very high certainty, that they will be required to operate very differently,” Fisk said.

Fisk said efforts to maximize profit have seen the dam owners unleash the torrents when market prices are up, then stanching the flow when they go down.

“We have for decades suffered, both Vermont and New Hampshire … significant impacts from that stage height or water-level fluctuation, which causes erosion,” Fisk said.

He expects the re-licensing process to demand more ecologically responsible river flows. He said he also expects the new owners to retrofit the dams in ways that allow migratory fish species like shad, lamprey and eel to navigate the impoundments.

Fisk’s message to lawmakers? Running the dams responsibly is going to eat into profits. And that’s exactly why some environmentalists are so keen on the state buying them.

Jon Groveman, policy and water program director for the Vermont Natural Resources Council, told lawmakers it’d be good to have an owner that wasn’t “a purely for-profit private entity.”

“You have an opportunity to be in control of renewable, base load power, and have the public overseeing and responsible for the licensing and the operating and the management of these facilities,” Groveman said.

Groveman said it’s also a challenge, since the state, were it to purchase the dams, might find its environmental and economic missions at cross-purposes. Groveman said he thinks that tension can be resolved with the proper oversight structure.

Last week, top elected officials appointed a seven-person working group to vet the purchase of the dams.