HELENA — The owners of the Colstrip power plant in southeastern Montana signed an agreement Thursday to stop pouring coal sludge and other liquid waste into storage ponds that leak enough contaminated water to nearly fill an Olympic-sized swimming pool every day.
The agreement between Talen Energy, which represents the six Colstrip owners, and three environmental groups is the latest development for the beleaguered Colstrip Steam Electric Station, the second-largest coal-fired plant west of the Mississippi River that has come under increasing market and regulatory pressure. Earlier this month, the plant’s owners agreed to shut down its two older units by 2022 in a proposed settlement filed in a separate lawsuit.
The new settlement calls for Colstrip’s two newer units to convert to a non-liquid disposal system for its bottom ash by 2018 and for its scrubber sludge by 2022.
Bottom ash is the coal that isn’t ignited during the plant’s power generation, and it’s sluiced with water and disposed of in the ash ponds outside the plant, said Jenny Harbine, an attorney for Earthjustice, which represented the three environmental groups.
The other type of liquid that goes in the ponds, scrubber sludge, is made up of the waste from the plant’s air pollution control devices that remove pollutants such as arsenic and mercury from the plant’s exhaust stream. Under the agreement, Talen Energy will have to figure out how to turn that liquid waste into dry waste by 2018 and 2022.
“It’s absolutely the first step to getting a handle on the groundwater problem,” Harbine said.
Talen spokesman Todd Martin said Colstrip’s owners already have invested millions of dollars to minimize the plant’s effects on the environment, and they are working on how to convert the waste from liquid to solid. “We believe we have identified the proper technology, but are continuing the process of researching the design and engineering,” Martin said.
The Montana Environmental Information Center, the Sierra Club and the National Wildlife Federation sued over the leaking ponds, which have contaminated the water tables surrounding the plant for decades. A 2012 agreement between Colstrip and the Montana Department of Environmental Quality was supposed to clean up the contamination, but that deal set few deadlines and called for years of study.
The case revealed that the ponds were leaking an estimated 380 gallons of contaminated water per minute, which is the equivalent of 547,200 gallons per day or 200 million gallons every year.
Earlier this month, Talen and Colstrip co-owners Puget Sound Energy, Portland General Electric and PacifiCorp agreed to shut down two of the plant’s four electricity-generating units by 2022. The settlement is part of a separate lawsuit over the plant’s emissions violations, and the deal has angered state officials and residents of the town who depend on one of the state’s largest employers.