Key facts
- Xcel Energy's plan to clean up groundwater contamination from coal ash at the Valmont Power Station is under review by Colorado regulators.
- The proposed system will pump contaminated groundwater for treatment and disposal.
- Critics argue that a second, older landfill at the site may also be contributing to pollution and has not yet been addressed.
- Decades of coal burning at the Valmont Station produced 1.6 million cubic yards of coal ash stored in landfills.
- Contaminants found in the coal ash include arsenic, lead, and chromium, with elevated levels of lithium and selenium detected in monitoring wells.
Colorado regulators are currently reviewing Xcel Energy's final plan to address groundwater contamination stemming from decades of coal ash disposal at the Valmont Power Station. The proposed project, which could commence construction by late summer, aims to mitigate pollution that has migrated beyond the company's property and has been detected in at least one nearby residential well.
The plan involves a system designed to pump contaminated groundwater from beneath the site for off-site treatment and disposal. This approach is described as a first-of-its-kind in Colorado. However, environmental advocates have raised concerns that the cleanup may not be fully effective if a second, older coal ash landfill located near the power plant is also a source of the contamination.
Nearly a century of coal combustion at the Valmont Station resulted in approximately 1.6 million cubic yards of coal ash being stored in landfills east of Boulder. This waste material contains hazardous substances such as arsenic, lead, and chromium. An investigation revealed that a landfill built in 1993 has been contaminating groundwater since at least 2017, with Xcel's own monitoring data showing coal ash in contact with groundwater and elevated levels of lithium and selenium in monitoring wells. This contamination plume has been observed moving towards nearby residential areas, with lithium levels exceeding safe limits in at least one homeowner's well.
Erin Dodge, a water quality program coordinator with Boulder County Public Health, emphasized the critical need for a well-designed groundwater treatment system to prevent further spread of contamination. State and federal regulations mandate that Xcel address both the source of the pollution—the coal ash—and the resulting groundwater contamination. The extraction system is part of a larger cleanup effort that is expected to include the removal of coal ash from the 1993 landfill over approximately a decade.
Concerns have also been voiced regarding potential air quality impacts during the excavation and processing of coal ash. Xcel spokesperson Sydney Isenberg stated that the company anticipates state approval for the final design of the extraction system and expects installation to begin in late summer.
The second coal ash landfill, situated northeast of the power plant, was initially exempt from federal regulations enacted in 2015 because it was no longer operational. However, expanded EPA rules in 2024 now cover these 'legacy landfills,' though they do not set firm cleanup deadlines. Xcel has not yet submitted a remediation plan for this site, and its role in the contamination remains unclear, as stated in a 2024 work plan. Legacy landfills are often more prone to leaks due to the lack of liners and monitoring systems.
Abel Russ, a lawyer with the Environmental Integrity Project, criticized the approach, suggesting that ignoring the legacy landfill could lead to a continuous pumping and treating process that fails to achieve full remediation. Lisa Evans of Earthjustice noted that if federal requirements are rolled back, the responsibility for addressing the second landfill would fall to state regulators or Xcel itself.
Xcel's cleanup design documents indicate that contamination has spread into two distinct groundwater plumes, one with elevated selenium and lithium, and another primarily with lithium. The proposed system aims to intercept these plumes using extraction wells and collection trenches.