Colstrip Steam Electric Station has 609 groundwater monitoring wells, 596 of which have been polluted above federal advisory levels based on samples collected between February 03, 2010 and May 20, 2015. Groundwater at this site contains unsafe levels of sulfate, boron, selenium, nitrate, fluoride and manganese.Site description
The Colstrip power plant is made up of four coal-fired units and operates a network of nine coal ash impoundments. It is the second largest coal-fired plant in the Western US. In 2003 a lawsuit was filed by residents of the town of Colstrip alleging groundwater pollution from the operations of Colstrip's impoundments and waste ponds. In May 2008 the five utility companies that jointly owned and operated the Colstrip power plant finalized a $25 million settlement with the 57 plaintiffs who blame the utilities for contaminating their groundwater and causing structural damage to some properties.
In August 2012, the operators of the facility entered into an "Administrative Order on Consent" with the Montana Department of Environmental Quality to study the effectiveness of potential remediation strategies. Another legal settlement in 2016 requires the closure of Colstrip's two older units by 2022.
The Environmental Protection Agency has identified Colstrip as a location where coal ash disposal activities have been proven to contaminate ground and surface water.