AUGUSTA, Maine -- Maine conservationists say four dams on the Kennebec River are the biggest threat to Atlantic salmon populations, and groups intend to sue to get them removed.

Brookfield Renewable Partners is an international energy company that owns four dams on the Kennebec River between Waterville and Skowhegan.

Nick Bennett, staff scientist for the Natural Resources Council of Maine, noted one of the best spawning habitats for Atlantic salmon is in the Sandy River, a tributary above Brookfield's dams. Atlantic salmon are known as "sea-run" fish, they spawn in fresh water but spend much of their lives in salt water.

He said the dams pose an often fatal hazard for the fishes' path to the ocean.

"They really need to be removed if we want to have any chance of restoring Atlantic salmon and the other species of sea-run fish that are necessary for them to be restored like river herring, shad and eels," Bennett asserted.

Groups claim the dams violate the Endangered Species Act (ESA).

The Conservation Law Foundation, Maine Rivers and the Natural Resources Council of Maine have given the required 60-day notice to sue companies under the ESA.

Bennett emphasized when it comes to restoring the species, groups are laser focused on the dams. He pointed out historically, the Kennebec River has been the largest Atlantic salmon run of any river in the U.S.

"These four dams block Atlantic salmon, both from getting up to the Sandy River to spawn, and from getting out of the Sandy River to head back to the ocean to grow into adults," Bennett explained.

Last July, the federal government rejected a Species Protection Plan proposed by Brookfield, and the Maine Department of Marine Resources and the National Marine Fisheries Service have recommended the removal of one of the dams.

The company shut down three of its four dams for salmon migration earlier this month, with operations set to resume May 31.

The Biden Administration is considering the future of Pacific Northwest salmon and the effect of dams in the region.

The White House Council on Environmental Quality held listening sessions this spring and is now asking for public comments on dams in the Columbia River basin.

They're especially focused on four dams on the lower Snake River that have been major barriers to the dwindling salmon populations that migrate upstream to Idaho.

Mitch Cutter is the salmon and steelhead associate with the Idaho Conservation League.

"What we've seen so far in both the listening session and in the public comments," said Cutter, "is an overwhelming majority of people saying they want to breach the lower Snake River dams - because it's essential for salmon and steelhead, and because there's other ways of doing the things that the dams provide."

Supporters of keeping the dams say they provide essential energy, irrigation and barging functions. But Cutter noted that during listening sessions, more than three-quarters of commenters were in favor of breaching the dams.

The Council on Environmental Quality public comment period is open through August 31.

Cutter said there is interest in removing the dams from a variety of people in the Northwest.

"We're seeing people from across the region," said Cutter, "come out of the woodwork and say, 'This issue matters to me, even if it didn't two, three, five, ten years ago. We'd like to have this problem solved.'"

During this year's legislative session, Washington state lawmakers approved $7.5 million for planning to replace the dam's services. The four Snake River dams are in southeast Washington.

Funding in Washington state's budget is pushing efforts forward to remove four lower Snake River dams in order to save salmon.

Lawmakers committed more than $7 million to begin the transition planning process for the four dams in southeast Washington. The dams have been a site of contention because of their effects on the dwindling population of salmon.

Tanya Riordan, policy and advocacy director for Save Our Wild Salmon, said past studies and reports have called for dam removal, and the federal government sees the new funding efforts as proof the state is ready to take action.

"Although the decision to remove the dams will be made by the federal government -- they're federal dams -- these measures do ensure that Washington state will be prepared to effectively replace the transportation, energy and irrigation infrastructure," Riordan explained.

Last year, Gov. Jay Inslee and Sen. Patty Murray, D-Wash., released a report on replacement of the four dams' services, including barging, hydropower and irrigation provided to nearby agriculture. Riordan believes the new funding measure follows through on their promise. Inslee signed the budget this week.

Erin Farris-Olsen, regional executive director for the National Wildlife Federation, said salmon are resilient and have come back to the Snake River, albeit in smaller numbers. She stressed quick action is necessary to save them.

"We're moving at the pace of our own readiness as humans more so than we're thinking about the ticking of the clock in terms of salmon extinction," Farris-Olsen contended.

Riordan noted more than $26 billion have been spent on mitigation efforts to recover salmon and keep the dams in place, but they have not worked, and she added there are a number of advantages to transitioning away from them.

"We upgrade and modernize our energy system and transportation and irrigation and the state is benefited and communities will be benefited significantly through this process," Riordan asserted. "We'll save salmon, and we will uphold our treaty responsibilities to tribal nations."

Four dams on the lower Snake River have been the sites of contention in the Northwest, and a recent report of an oil spill at one of the dams could be adding fuel to the fire.

The U.S. Army Corps of Engineers reported 300 to 600 gallons of oil leaked from the Little Goose Dam between August and October.

Mitch Cutter, salmon and steelhead associate for the Idaho Conservation League, said there have been similar incidences in recent years of leakage from the lower Snake dams.

"We're seeing the results of these dams being old, frankly," Cutter asserted. "They were started to be constructed in the '60s through the '70s, and I think we're seeing the result of infrastructure starting to outlive its useful life."

There has been a growing chorus of calls to breach the dams to allow for greater passage of endangered salmon and steelhead species in the region. However, there are also opponents of the plan. Rep. Dan Newhouse, R-Wash., recently said there is "no clean-energy future" for the Northwest without these dams.

Cutter is skeptical of Newhouse's analysis, arguing the cost of keeping the dams has become too high to make financial sense anymore.

"They don't provide valuable services to the Northwest system or to the western energy grid," Cutter contended. "They can be easily replaced with other resources that cannot just replace everything these dams do. They would actually improve on the services they provide to the region."

Cutter also stressed it is important to keep iconic species such as salmon and steelhead front and center when discussing this issue.

"There are real solutions for how to replace everything these dams provide, but there's no replacement for wild salmon and steelhead in Idaho or in the Snake River," Cutter added.