After a summer plagued by pollution problems, a major Montana coal plant is back on line and providing power for Puget Sound Energy

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A Montana coal-fired power plant that provides electricity for Puget Sound Energy is once again operating at full strength after a summer complicated by pollution problems.

The Colstrip power plant in southeast Montana has four generating units. The two largest, units 3 and 4, were forced offline in June after failing to comply with a particulate matter limit established by the federal Mercury and Air Toxics Standard.

Earlier this month, the plant was able to demonstrate compliance with that standard to regulators, according to a statement released by Talen Energy, the plant’s operators.

Currently, all four units are “fully operational and will run as electric system conditions dictate,” according to the statement.

PSE, Washington’s largest private energy utility, relies on coal to provide 37 percent of its electricity and is a part owner of Colstrip.

While Colstrip units 3 & 4 were shut down, PSE bought power on regional markets and drew more electricity from its own gas, wind and hydroelectricity facilities.

PSE also was able to tap into electricity produced from Colstrip’s two older units, 1 & 2, which went down for maintenance during the spring but came back online in mid-June, according to a PSE spokesman.

The long-term fate of the Colstrip plant is the subject of intense regional debate, with PSE and other owners planning to shut down the first two units by July 2022. PSE, the largest Colstrip owner, has forecast that it will stop drawing power from the other two units by the early 2030s, and hinted in planning documents that it could happen sooner.