The Colstrip Steam Electric Station consists of four generating facilities. Units 1 and 2 are 307 Megawatts each and Units 3 and 4 are 740 Megawatts each (Nameplate capacity is cited and is larger than actual generation of delivered electricity).
Construction of Units 1 and 2 began in 1972 and they came online in the mid 1970s. Unit 3 came online in 1983 and Unit 4 in 1985. All four units were certified by the Montana Board of Health and Environmental Sciences. The functions of the Board of Health and Environmental Sciences are now carried out by DEQ. Agreement to Comply Certificate for Units 3 and 4 Units 1 and 2 ceased operation and essentially closed in early January of 2020. More information on the closure is available through the Legislative Services Division.
The modern town of Colstrip in Rosebud County was established during the construction phases of the plants and remains as a community of workers and support businesses for the electric generation facilities. The town draws drinking water from the Yellowstone River by a system that also supplies the generation facilities.
The six utilities with ownership in the generation plant paid the town of Colstrip and Rosebud County more than $13 million in 2014 in the form of property taxes. The coal mine paid nearly $9 million in county taxes that year.
The plants are partially owned by Talen Energy of Pennsylvania, which is also the operator of the facility. Riverstone Holdings, a New York City-based investment company, completed its acquisition of Talen in December 2016. Coal for the facilities is mined from the nearby Rosebud Mine, which is owned by Western Energy company, a subsidiary of Westmoreland Coal of Colorado. The mine is permitted by the federal Office of Surface Mining or through the state by DEQ. Other partial owners of the generation plant include Puget Sound Energy, PacifiCorp, Portland General Electric, Avista, and NorthWestern Energy.
Regular operation of the generation facilities produces coal ash, which has historically been placed in ponds surrounding the plants. Some are used exclusively by Units 3 and 4 while others are used by all four units. By the 1990s, monitoring wells indicated significant leakage of the ponds into groundwater. DEQ and Talen Energy have an Administrative Order on Consent to address this seepage of toxic elements into groundwater. The 2016 Annual Plan and a Five-Year Plan for the AOC are on-file. View PDF
The Colstrip plants are also permitted by DEQ's Air Programs. Restrictions include visible emissions that affect opacity, particulate matter, and Sulfur Dioxide and Nitrous Oxide levels. The current permit also requires Talen Energy to install scrubbers and provide a plan to meet restrictions. View PDF
DEQ also permits the Rosebud Power Plant, also known as Colstrip Energy Limited Partnership (CELP), a small electric generating facility six miles north of Colstrip. Air Quality Permit