Toxic Coal Ash in Montana: Addressing Coal Plants’ Hazardous Legacy

For decades, utilities disposed of coal ash — the hazardous substance left after burning coal for energy — by dumping it in unlined ponds and landfills. Montana has 23 coal ash dumpsites.

After years of litigation and grassroots activism, on Apr. 25, 2024, the EPA issued a new rule that will force power plants to finally clean up their toxic coal ash. The EPA extended federal monitoring and cleanup requirements to hundreds of previously excluded older coal ash landfills and ponds that have been leaking toxic pollution into groundwater.

Note: Coal ash dumpsites referenced as “unregulated” throughout this page now are likely subject to federal regulation under the final rulemaking.

Coal ash contains hazardous pollutants including arsenic, boron, cobalt, chromium, lead, lithium, mercury, molybdenum, radium, selenium, and other heavy metals, which have been linked to cancer, heart and thyroid disease, reproductive failure, and neurological harm. In 2023, the EPA acknowledged that coal ash is even more dangerous than previously thought, with levels of arsenic and radiation that pose cancer risks.

Industry’s own data indicate that across the country 91% of coal plants are currently polluting groundwater above federal health standards with toxic pollutants.

Despite EPA’s 2015 Coal Ash Rule, which created the first-ever safeguards for coal ash disposal, many coal ash dumps remained unregulated due to sweeping exemptions for legacy coal ash ponds and inactive landfills. The exempted coal ash dumps are sited disproportionately in low-income communities and communities of color. The EPA extended clean up requirements to hundreds of old coal ash dumps across the country when it issued new regulations in the spring of 2024.

Aerial view of the Colstrip coal-fired power plant in Montana in 2004.
The Colstrip coal-fired power plant in Montana in 2004. (Larry Mayer / Getty Images)

Coal ash remains one of our nation’s largest toxic industrial waste streams. U.S. coal plants continue to produce approximately 75 million tons every year.

In 2023, the EPA acknowledged widespread noncompliance with existing coal ash regulations and ramped up enforcement after designating coal ash a national enforcement priority.

Action Needed

The magnitude of harm from recklessly dumped toxic coal ash requires decisive action from federal and state regulators.

  • Utilities must be required to comply with the law and immediately clean up their pollution.
  • EPA and states must act quickly to ensure that utilities leave communities with sites that benefit rather than harm their health, environment, and economic status.
  • EPA must take action to prohibit the use of coal ash as construction fill and make polluters clean up areas where ash was used as fill.
Coal ash dump sites across the United States. Use this map to understand where coal ash might be stored near you and how a given site may be impacted by EPA's expansion of the federal Coal Ash Rule. (Caroline Weinberg / Earthjustice)

16 Regulated Coal Ash Disposal Sites in Montana

Montana utilities operate 16 federally regulated coal ash ponds and landfills containing more than 14 million cubic yards of toxic waste at two power plants.

Coal ash has caused groundwater contamination at all of Montana’s regulated dumpsites. Some of these dumps are contaminating water at dozens of times the safe levels of certain pollutants.

One of them, the Colstrip Steam Electric Station, is the subject of a state enforcement action over groundwater contamination caused by leaking ponds.

Despite this widespread environmental harm, no Montana company, to date, has initiated a plant-wide cleanup to restore groundwater, despite the legal requirement to do so.

Colstrip Colstrip Talen Energy 12 unlined ponds, 1 lined pond Boron (x47), Cobalt (x13), Lithium (x28), Molybdenum (x8), Radium 226+228 (x2), Sulfate (x28), Thallium (x1)
Lewis & Clark Richland Montana-Dakota Utilities Co. 2 unlined ponds, 1 landfill Arsenic (x4), Boron (x13), Cobalt (x1), Lithium (x6), Molybdenum (x3), Selenium (x2), Sulfate (x12)

All data on groundwater contamination from coal ash derived from the utilities’ publicly accessible CCR Compliance Data and Information websites, and exceedances were calculated by Environmental Integrity Project.

For more information on regulated coal ash sites in Montana, see Mapping the Coal Ash Contamination.

Seven Coal Ash Legacy Ponds and Inactive Landfills in Montana

March 2024 Update: The table below underestimates the legacy units that may be regulated by EPA’s upcoming CCR Legacy Pond Rule. Additional legacy units at specific plants may be found in the national map, above.

In addition, Montana hosts at least seven inactive coal ash landfills and legacy ponds that escaped federal regulation. The exact number remains unknown because utilities were not required to report these sites.

These dumps are almost certainly contaminating water and threatening health and the environment; however, monitoring data are not currently available for most unregulated sites.

As we anticipate EPA’s proposed rule on legacy ponds and unregulated landfills in May 2023, concern remains that the agency will not address coal ash that was dumped off site or used as fill.

Colstrip Colstrip Colstrip Energy LP 0 2 Yes – EPA damage case
J.E. Corette Billings PPL Montana LLC 2 1 Unknown
Lewis & Clark Richland Montana-Dakota Utilities Co. 0 2 Yes – Industry data

Lewis & Clark's evidence of site contamination: Data on groundwater contamination from coal ash derived from the utilities’ publicly accessible CCR Compliance Data and Information websites, and exceedances were calculated by Environmental Integrity Project.

These data were developed by using EPA datasets relied upon in their 2007 and 2014 CCR risk assessments (Human and Ecological Risk Assessment of Coal Combustion Residuals) and comparing those datasets to the universe of regulated units.

“EPA damage case” denotes a site where US EPA has found documented groundwater contamination from coal ash.

Earthjustice fights in the courts for a long-term solution to the toxic menace of coal ash. And we act on behalf of dozens of clients and over 100 coalition partners to defeat legislative attempts to subvert federally enforceable safeguards of coal ash.

Earthjustice’s Clean Energy Program uses the power of the law and the strength of partnership to accelerate the transition to 100% clean energy.