Merrimack Station coal-fired power plant, which sits on the shore of the Merrimack River, whose waters can be seen in the foreground.
Merrimack Station, located along the Merrimack River, is soon to be the last coal-fired plant in New England. Credit: PSNH / Creative Commons

New England’s soon-to-be last remaining coal plant is facing pressure from environmental groups to step up protections in a nearby waterway.

The Sierra Club and Conservation Law Foundation are pushing the U.S. Environmental Protection Agency to reconsider a water permit it issued last year to the owner of the Merrimack Station coal power plant in New Hampshire.

They want the EPA to revise the permit to require the owner, Granite Shore Power, to install water cooling towers at the plant. Without these towers, which are a common feature of coal plants, Merrimack Station runs the risk of hurting the local fish population, the Sierra Club and Conservation Law Foundation say.

While water permits are supposed to be updated once every five years, the EPA issued the Merrimack plant’s new water permit more than 25 years after the last one. The agency’s decision not to require water cooling towers was an abrupt reversal from its previous stance in discussions on the permit, when the agency suggested the towers should be required.

The Sierra Club and Conservation Law Foundation appealed the decision to the EPA’s appeals board. Granite Shore Power also appealed the decision, which, instead of the cooling towers, included requirements for alternative protections meant to keep fish from getting sucked into the intake system.

The appeals board could decide the outcome of the final permit, or the EPA could voluntarily decide to reconsider it.

After the Biden administration took control of the agency, the EPA requested the appeals board issue a stay on the cases from the environmental groups and Granite Shore Power. That stay is set to expire Monday, April 19, although the agency on Wednesday requested an extension until June.

Granite State did not respond to a request for comment this week. Even if it does end up having to install a new cooling system, this wouldn’t necessarily push it out of operation. The plant, which runs during times of peak demand, receives monthly capacity payments from the regional grid operator, ISO-NE. Since ISO-NE has so far deemed the plant necessary for reliability in the region, it has a stronger case to stay open.

Still, the debate carries symbolic significance beyond the immediate impact on the river. Many clean energy advocates would like to see the plant close, especially as New England turns toward new sources of energy such as offshore wind and solar.

“I suspect the real issue is not the cooling tower itself,” said Ashley Brown, executive director of the Harvard Electricity Policy Group. “I suspect the real issue is what do we do with the last remaining coal plant in New England.”

The EPA in 2011 estimated a water cooling system at Merrimack Station would cost about $112 million, including installation and year-round operation over a 20-year period. Brown couldn’t speak about the Merrimack plant specifically, but he said that in general, cooling towers don’t significantly set back coal plant operators financially. But it makes sense that environmental advocates would want to do what they can to drive up costs for the plant, he said.

Environmental advocates in the current case say that the outcome of the permit is important for the future of the river.

Fossil fuel generators are able to compete with clean power by avoiding paying for their environmental impact, said Zachary Fabish, staff attorney at the Sierra Club. “The only reason coal-fired power plants like Merrimack exist is because they’re foisting their environmental costs” onto the public, he said.

Merrimack Station can take in nearly 300 million gallons of water a day when running. That water, called “cooling water,” is used to absorb the waste heat from the steam the plant uses to generate electricity. The heated water is then discharged back into the river. This is different from New England’s other power plants, which use cooling towers or alternative methods to avoid distributing hot water into the river.

The roughly 6-mile stretch of the 117-mile river that the water is discharged into is “particularly vulnerable to the effects of Merrimack Station’s thermal discharge,” the EPA said in 2011. The water is discharged at temperatures up to 104 degrees, as much as 23.8 degrees warmer than the ambient water temperature, the agency said.

The increased heat and the sudden fluctuations in temperature have the potential to kill fish, lead species to go extinct and invite new ones in — dramatically altering the river’s ecosystem, the environmental groups say. According to the EPA in 2011, data showed that fish abundance in that stretch of the river, known as the Hooksett Pool, “had substantially declined since the plant’s second power generating unit came online in 1968.” Additionally, the agency said, the area was now dominated by fish species favoring warmer water.

An EPA spokesperson last year said the agency no longer deemed cooling towers necessary because the agency has new regulations and because the plant operates far less now than it did in 2011.

The Biden administration has much different environmental standpoints than the Trump administration did, so the change in leadership could change the agency’s perspective. “I wouldn’t be surprised if they reverse the decision,” Brown said.

If the EPA’s request for an extension on the stay is granted, officials will have more time to decide how to proceed. Eventually, the agency will have to decide whether to move forward with the appeals process — indicating its intent to keep the permit as is — or to rescind the permit and reconsider requiring the cooling system.

Environmental advocates say that if this permit isn’t well-crafted, the plant could damage the fish population until the next permit update comes around. Given how long the current process took to get underway, it’s unclear when a new one might begin.

“In a perfect world — in a world that complies with the Clean Water Act,” Fabish said, “this permit would be updated every five years.” That hasn’t been the case so far though, and based on what he’s seen here and in other parts of the country, it may not be the case going forward. “If the EPA doesn’t get it right here … who knows when they’re next going to improve this permit?”

David has written on health, science and the environment for various outlets, including World Wildlife Fund and the Chicago newspaper Windy City Times. He has reported on topics including the city’s opioid epidemic, bird research at the Field Museum, and LGBT youth in foster care, and was a Chicago correspondent for the Energy News Network. Now based in New York, David covers northern New England.