Dive Brief:

• The U.S. Environmental Protection Agency on Tuesday finalized its water pollution permits for the Merrimack coal-fired power plant, allowing the plant to continue operating without the cooling towers most plants of its size are required to operate with.

• Merrimack's permit has not been updated since 1992 and was originally scheduled to expire in 1997. In 2011, the EPA found the facility's method of discharging its cooling water into the nearby Merrimack River "contributed to the deterioration of fish populations" and recommended the plant be upgraded to a closed-cycle system, which would dramatically reduce the amount of hot water discharged.

• Environmental groups said the agency's proposal is "a complete 180" from the permit proposed in 2011. "As a result, Merrimack will continue harming aquatic life with its thermal pollution and hot and cold shocks," Zachary Fabish, senior attorney at the Sierra Club told Utility Dive in an email. "The EPA has allowed Merrimack to pollute under an expired permit for 23 years, and 23 years is a very long time to wait for such woefully inadequate protections."

Dive Insight:

Merrimack is the largest remaining coal plant in New England and the target of many environmental efforts in the region. The plant is guaranteed to stay open through at least June of 2024 as it cleared the New England Independent System Operator's capacity auction in February.

Power plants requiring cooling facilities in order to operate, but have a number of ways to cool their systems. The historically cheap and easy way was for the plant to bring in water from a nearby source, circulate it, and then discharge that water back into the local water source, according to the Union of Concerned Scientists. 

However, those systems tend to pose a risk to aquatic life within the water source — significant temperature swings in the river when the plant starts up and shuts down can disrupt fish and other creatures that have adapted to the environment, and warm waters in particular can provide a toehold for invasive species into local waterways, according to the Sierra Club.

That's why the group pushed for the Merrimack permit to update its system to instead use cooling towers, which circulates the water continuously through the system.

Merrimack's owner since 2017, Granite Shore Power, says because the coal facility operates at a lower capacity than it used to, the EPA's permit "reflect[s] the reality" of its current situation by not asking it to make major upgrades, such as a cooling tower.

"While we are continuing to review the details of this new Permit, it prioritizes environmental protection, providing specific thermal discharge limits that the EPA has determined are protective of the life cycles of fish and aquatic life in the Merrimack River," the company said in a statement. "At the same time, the Permit reflects the important role served by Merrimack Station as a reliable source of power while taking into account the facility's far lower utilization level."

EPA also acknowledges that its permit is reflective of the plant's lower operational life — the plant runs mostly as a peaker facility now, according to New Hampshire Public Radio.

"[I]n 2011, Merrimack Station was a baseload generator operating nearly all the time, but now only operates during periods of peak demand, primarily in the winter and summer, which means greatly reduced discharges of waste heat and withdrawals of cooling water," EPA spokesperson John Senn told Utility Dive in an email. "Reevaluating the permit limits in light of this major change was necessary.​" 

As a result, EPA set thermal limits that it says "will assure the protection and propagation of the balanced indigenous population of the shellfish, fish, and wildlife in the Merrimack River and that reflect Merrimack Station's current mode of operation," including keeping "specific in-stream temperatures" maintained.

But the Sierra Club maintains the new permit is a complete reversal of its original findings, and says the system will continue to harm local waterways.

"This permit is a complete 180 by the EPA. The 2011 proposed permit did the right thing by requiring cooling towers so that this enormous coal plant would stop dumping tens of millions of gallons of heated wastewater into the Merrimack River every day it operates, but the EPA has failed to follow through in this final permit," said Fabish.

EPA and the New Hampshire Department of Environmental Services' 2011 permit report found that the water temperature changes were harming local aquatic life.

"Data indicates that thermal discharges have contributed to the alteration and depletion of fish populations in the Pool over the last 20 to 30 years. Making matters worse, fish are also killed and injured by the facility's withdrawals of river water for its cooling needs," the EPA found. "The water taken from the river contains fish eggs and larvae and these tiny creatures are pulled through the facility's cooling system and killed by exposure to harsh physical impacts, extreme water temperatures and toxic chemicals."

In 2014, the agency issued a draft permit that found a cooling water intake structure was needed to mitigate these impacts. Then, under the Trump Administration in 2017, the agency reopened a comment period on the permitting process, saying "new data, information, and arguments pertinent to certain aspects of the permit – including data, information, and arguments related to new EPA regulations applicable to the permit – have emerged and appear to raise substantial new questions concerning the permit." 

Sierra Club sued the agency that same year, arguing that the agency had unreasonably delayed updating the permit. The U.S. Court of Appeals for the First Circuit declined to enforce the schedule, but urged the agency "to work diligently" to complete the permits.

EPA said its current proposal includes "wedge wire screens​" in order to minimize aquatic wildlife harm.

"For the final permit, EPA determined that using the wedge wire screens would minimize and prevent aquatic organisms from being harmed, satisfy the new regulations, and be more cost effective than cooling towers," said Senn. "The legal requirements for existing facilities like Merrimack Station call for site-specific, case-by-case decision-making applying the standards in the Clean Water Act and EPA regulations. As a result, some facilities use cooling towers and others do not."

Sierra Club says the permit is just another example of loosened environmental protections under President Donald Trump.

"The Trump Administration has failed New Hampshire. This new permit is woefully inadequate and retreats from the recommendations responsible officials at the EPA previously made," Catherine Corkery, New Hampshire Chapter Director and Senior Organizing Representative for the Sierra Club said in a statement.