Colorado health officials denied Xcel Energy’s initial proposal to clean up coal ash contamination at the Valmont Power Station just outside Boulder, saying it failed to meet state standards for protecting health and the environment.
Coal ash, a toxic byproduct of burning coal, has contaminated groundwater at the site and is migrating toward nearby neighborhoods, a Boulder Reporting Lab investigation found. The pollution is largely hidden underground but represents a significant and long-lasting source of contamination. After nearly a century of coal burning at Valmont, Xcel retired the facility’s last coal unit in 2017 and converted it to natural gas.
Both state and federal rules require Xcel to remove more than a million tons of coal ash and restore groundwater to safe levels. But disturbing and hauling away the buried ash could also release toxic dust into the air. Xcel says the cleanup — including groundwater treatment and ash removal — is set to begin in early 2026 and take at least a decade. The site isn’t expected to be largely restored until the mid-2030s. The project is estimated to cost $60 million to $70 million, with the state Public Utilities Commission deciding how much of that bill falls to Xcel’s Colorado customers.
The state’s preliminary decision reflects how responsibility for oversight is falling more heavily on state and local governments. Federal coal ash oversight lagged under President Biden and has further weakened under President Trump, environmental advocates say.
“The EPA has been largely missing in action on enforcing federal coal ash law. It’s regulatory state agencies that are pushing the progress,” said Lisa Evans, senior counsel for EarthJustice, which advocates for coal ash cleanup nationwide. “This is all in the backdrop of the entire utility industry ignoring coal ash threats and continuing to dispose of their ash recklessly and dangerously in unlined landfills and surface impoundments. It’s created this huge nationwide problem.”
Still, Evans said, “I am heartened by Colorado’s involvement and concern.”
State cites health risks
Xcel’s initial January plan proposed processing most of the ash into cement on-site at Valmont and selling it locally. But in July, the Colorado Department of Public Health and Environment (CDPHE) denied the plan. The letter cited vague waste-disposal methods, weak protections against air, water and soil contamination, and failure to respond to public concerns after multiple rounds of comment.
Officials also warned that disturbing the ash could release dust beyond the site, potentially exposing the public to arsenic, lead and mercury, among other heavy metals linked to cancer, cardiovascular problems, nervous system damage and infertility.
“We’re making sure that we have the right requirements and procedures to protect the community,” Jerry Henderson, who leads the state health department’s solid waste permitting division, told Boulder Reporting Lab. Because this is Colorado’s first coal ash cleanup of this scale and duration, he said, its requirements could set a precedent.
“We want to make sure we get it right the first time.”
Valmont is also among the first coal ash sites in the country slated for full remediation, giving the project national implications.
In its filings, Xcel argued that disposing of coal ash posed fewer “nuisance situations” than municipal waste because it doesn’t rot or decompose, and is “non-flammable” and “odorless.” State officials rejected the comparison and ordered the language removed.
Xcel spokesperson Michelle Aguayo told Boulder Reporting Lab the company will follow all regulatory requirements but said that “real-time air quality monitoring during the landfill excavation is not mandated.” She said Xcel will use “robust controls and protocols explicitly designed to minimize fugitive dust emissions.” These include water sprays, daily covering of exposed ash and limiting the active work, she said.
Some residents remain unconvinced. Cindy Warren, a retired pathologist who lives nearby, said the lack of air quality monitoring leaves her worried about exposure.
“Without monitoring, we won’t be aware this is occurring, and no corrective actions will take place,” she said.
What Xcel proposed — and what the state questioned
Xcel proposed processing 85% of the ash for “beneficial reuse.” The rest would be stored in landfills and capped to prevent leakage.
Evans said substituting coal ash for Portland cement, the main ingredient in concrete and highly energy-intensive to make, can cut greenhouse gas emissions from cement production. But she and others argue that full removal is safer. “Eventually, all landfills leak, no matter how well they’re lined,” she said.
CDPHE officials flagged numerous gaps. They directed Xcel to show how it would keep coal ash from blowing off-site or spilling during transport, and to prepare a backup plan if groundwater contamination worsens. They also faulted the company for proposing to leave 10 acres of landfill uncovered and for weak wind-safety measures, halting work only after an hour of 45 mph winds, more than double the state’s 20 mph limit. Regulators also rejected its reliance on visual checks alone for dust monitoring.
The plan “lacked operational controls to ensure that coal ash didn’t become airborne and impact the nearby community,” Henderson said.
Xcel, in response, pledged to follow whatever plan the state ultimately approves. “The excavation and on-site transport of coal ash will be conducted in a careful and controlled manner designed to minimize any potential risk of exposure to the public,” Aguayo told Boulder Reporting Lab.
Federal oversight falters
Groundwater contamination at Valmont has been documented since 2017, when Xcel was required under the EPA’s Coal Combustion Residuals rule to begin testing and publicly reporting results. Those reports have consistently shown unsafe levels of contaminants.
Valmont’s main landfill is regulated under the EPA CCR rule, and a second, older landfill — once exempt — is now covered under an expanded version. Boulder Reporting Lab’s investigation found that this newly regulated landfill may also be leaking contaminants.
While the Biden administration elevated coal ash as a priority, enforcement has been inconsistent, and the Trump administration has granted utilities broad extensions on cleanup deadlines. Aguayo said those extensions will not affect Valmont. Henderson said the state holds quarterly meetings with Xcel and the EPA to keep the project on track.
Evans said that only a handful of sites nationwide have made meaningful progress. “You could probably count on one hand the cleanups that either have been completed or are in process, and there are hundreds of contaminated sites throughout the United States,” she said.
At Valmont, progress is being driven by a 2024 state compliance order that cited Xcel for violating Colorado’s groundwater protection standards. It requires the company to submit, revise and implement remediation plans on a fixed schedule.
Henderson said Xcel has filed a revised cleanup plan ahead of schedule. If approved, the company must then secure permits from different agencies, including an air permit from the state health department and a stormwater permit from Boulder County to protect water quality during construction.
Because the site lies outside city limits, the City of Boulder has no formal authority over the cleanup, but councilmembers have voiced concern about potential air pollution in nearby neighborhoods.
Although, this article is unclear as to whether the ash will be trucked off-site for use in concrete, it makes more sense to build a concrete plant on-site and as close as possible to the ash deposits. I would assume that by giving a “Ready Mix” company control of the site, they would see the ash as a valuable component of their final product, and treat it as such. Not as Xcel sees it as a liability. I would also assume that the concrete company would be more motivated to capture every last gram of the ash to use in their product, and create processes minimizing fugitive emissions.
The article states: “Xcel’s initial January plan proposed processing most of the ash into cement on-site at Valmont and selling it locally. But in July, the Colorado Department of Public Health and Environment (CDPHE) denied the plan. The letter cited vague waste-disposal methods, weak protections against air, water and soil contamination, and failure to respond to public concerns after multiple rounds of comment.”
Is the contaminated ground water connected to the local drinking water source? If so, is it known which neighborhoods are likely to be affected? Thank you for the detailed reporting on this and other topics.
I’d highly recommend reading our original investigation to get a better sense of the issue, and how urgent (or not) it is. We worked with some of the nation’s foremost experts in analyzing Xcel’s coal ash contamination data to characterize the problem. The “plume” of contamination is moving slowly underground, which is one reason it’s not considered an urgent threat to most people. That said, as you’ll read, contamination has been found in the water of nearby residents, with lithium detected in at least one well. https://boulderreportinglab.org/2023/12/11/hidden-hazard-boulders-million-ton-coal-ash-problem-has-no-local-watchdog/
As someone that is directly downstream of the ash pit I’m alarmed at the slow pace this process is taking. Xcel tests our water multiple times a year to understand if anything is changing (not yet, I’m glad to say). I’m more concerned that the arsenic and lithium are going to eventually get loose before they are allowed to clean it up. Let me add on that should that happen all of Walden Ponds and Sawhill ponds will be instantly effected. My ground water below the green is 18″ deep right now. The test wells are 10′ and 23′ respectively–won’t take much to spread everywhere.
There are 2 ready mix plants within 1/2 mile of the site.