Toxic Coal Ash in Colorado: 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. Colorado has 38 coal ash dumpsites.

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.

Coal ash remains one of our nation’s largest toxic industrial waste streams. U.S. coal plants continue to produce approximately 70 million tons every year.

Despite EPA’s 2015 Coal Ash Rule, which created the first-ever safeguards for coal ash disposal, many coal ash dumps remain 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. After years of litigation and grassroots activism, the EPA will extend clean up requirements to hundreds of old coal ash dumps across the country when it issues new regulations in the spring of 2024.

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

Smokestack of Valmont Power Station in Boulder, Colo., emits a plume of smoke into a hazy, darkened sky.
Valmont Power Station in Boulder, Colo., in 2011. (Josh Schutz / Getty Images)

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)

19 Regulated Coal Ash Disposal Sites in Colorado

Colorado utilities operate 19 federally regulated coal ash ponds and landfills containing more than 26 million cubic yards of toxic waste at eight power plants.

At every Colorado coal ash dumpsite that has been evaluated, coal ash has caused significant groundwater contamination.

Some of these dumps are contaminating water at more than 20-30 times the permitted levels of certain pollutants, and one of them — Comanche Generating Station — has been required to pay EPA penalties for improper disposal of coal ash waste.

Three Colorado plants are in the top 50 most-contaminated ash sites in the nation.

Despite the serious and widespread water contamination, no Colorado company to date has initiated a plant-wide cleanup to restore groundwater, despite the legal requirement to do so.

Cherokee Denver Xcel Energy 4 unlined ponds Boron (x2), Lithium (x3), Molybdenum (x1), Sulfate (x3)
Clear Spring Ranch Fountain Colorado Springs Utilities 1 landfill Boron (x2), Selenium (x4)
Comanche Pueblo Xcel Energy 1 unlined pond, 1 landfill Not evaluated
Hayden Hayden Xcel Energy 1 landfill Boron (x27), Cobalt (x1), Molybdenum (x34), Sulfate (x27)
Nucla Nucla Tri-State Generation and Transmission Assoc. 1 landfill Arsenic (x3), Fluoride (x1), Lithium (x83), Molybdenum (x1), Sulfate (x4)
Pawnee Brush Xcel Energy 2 lined ponds, 1 landfill Lithium (x4), Sulfate (x10)
Rawhide Wellington Platte River Power Authority 2 unlined ponds, 1 landfill Boron (x1), Cobalt (x2), Lithium (x14), Molybdenum (x1), Selenium (x2), Sulfate (x8), Thallium (x1)
Valmont Boulder Xcel Energy 3 unlined ponds, 1 landfill Arsenic (x2), Boron (x9), Cobalt (x4), Lead (x1), Lithium (x6), Mercury (x13), Molybdenum (x6), Selenium (x58), Sulfate (x11), Thallium (x2)

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 Alabama and throughout the U.S., see Mapping the Coal Ash Contamination.

19 Unregulated Coal Ash Legacy Ponds and Inactive Landfills in Colorado (ash dumps exempted from the 2015 Coal Ash Rule)

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, Colorado hosts at least 19 unregulated inactive coal ash landfills and legacy ponds that escape federal regulation. The exact number remains unknown because utilities are 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, a concern remains that the agency will not address coal ash that was dumped off site or used as fill.

Arapahoe Denver Public Service Co. of Colorado 6 0 Unknown
Cameo Palisade Xcel Energy 2 0 Unknown
Craig Craig Alaska Power and Telephone Co. 2 1 Unknown
Hayden Hayden Xcel Energy 0 1 Yes – Industry data
Martin Drake Colorado Springs City of Colorado Springs 4 1 Unknown
Rawhide Wellington Platte River Power Authority 0 1 Yes – Industry data
Valmont Boulder Xcel Energy 0 1 Yes – Industry data

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.

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

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.