As Xcel Energy prepares to dig up and process more than 1 million cubic yards of toxic coal ash at the Valmont Station on Boulder’s east edge, residents and local officials say the company’s proposed air quality monitoring plan falls short. They are working to build their own.
At the site, Xcel is required to clean up a 1.6-million-cubic-yard coal ash landfill that operated for nearly a century and has been leaching contaminants into groundwater. The company has agreed to monitor the air around the perimeter during the cleanup, but details such as how many monitors will be used, where they will be placed and how the data will be released remain unknown. State rules, which could determine whether any of that monitoring is mandatory, have also not been finalized.
That uncertainty has prompted members of the resident-led Valmont Community Commission and Boulder County Public Health air quality coordinator Bill Hayes to pursue a monitoring system independent of Xcel in partnership with Boulder AIR, a Front Range air quality service with research-grade instruments.
“When you remove such a massive landfill with coal ash, it’s really hard to foresee what the releases are,” said Boulder AIR CEO Detlev Helmig, whose stations in Erie and Broomfield routinely measure pollutants in far greater detail than state systems.
He said he is drafting funding proposals for a Valmont station, though money is uncertain as federal research funding has been cut and state grants are competitive. The final cost of a monitoring station has not yet been determined.
A decade-long cleanup and a denied plan
Xcel plans a two-part cleanup to meet U.S. EPA requirements to remediate the Valmont site to its condition before coal ash contamination: pumping and treating contaminated groundwater, and excavating the coal ash. The ash would be processed on-site into Portland cement and sold locally. The full operation is expected to take 10 years.
Read: Hidden hazard: Boulder’s million-ton coal ash problem has no local watchdog
But in July 2025, the state health department denied Xcel’s first cleanup plan, saying it failed to meet health standards and did not adequately address community concerns, including calls for stronger monitoring.
Why ash dust matters
Coal ash contains concentrated heavy metals such as arsenic, cadmium, lead and mercury, and can carry radioactive elements due to radium. When released into the air, smaller particles, known as PM2.5, can lodge deep in the lungs and enter the bloodstream.
Peer-reviewed research shows that coal ash exposure can be harmful. Studies have linked exposure to coal ash and related airborne particles to learning and behavioral impacts in children, higher rates of heart and lung disease, lung cancer, nervous system disorders, lower birth weights and shorter lifespans.
What scientists have not nailed down is a clear “safe” level of exposure, especially for long-term, low-level exposure in real-world conditions. The on-site ash will be processed in gas-fired kilns, according to Hayes, who expects necessary emission controls to be in place. Because research has not established clear safety thresholds for airborne coal ash, Hayes said, health agencies tend to default to stricter standards.
“We don’t have good laboratory data on the health impacts and at what level those impacts occur, so you have to be very conservative,” Hayes said.
A glimpse of a worst-case scenario for coal ash exposure came in the years following the 2008 Kingston spill, where workers who cleaned it up were covered in coal ash for months with little to no respiratory protection, while also bringing the ash home. By 2020, dozens of the cleanup workers had died and hundreds remained sick, with The Guardian reporting severe lung disease, low testosterone and energy levels, weekly blackout spells, failing eyesight, low kidney function and skin cancer. Family members have also faced health problems, including premature birth and respiratory illness.
Any potential risks would fall first on Valmont station’s immediate proximity: East Boulder, home to several manufactured home communities and other industrial operations. The area is already grappling with environmental concerns, including lead contamination worries from Boulder Municipal Airport and ongoing efforts to secure drinkable water at the San Lazaro mobile home park.
“This is where we see a lot more industrial type economic activity,” said Valmont Community Commission member and CU Boulder Climate Justice Program coordinator Alejandro Murillo. “This is also where we’ve sort of relegated a lot of our waste.”
The Valmont Community Commission is a group of residents working to spread the word about Xcel’s plans at Valmont, keep the community engaged and ensure opportunities for public comment.
Hayes said the Valmont coal ash project received the most public comment the Colorado health department has ever seen, with that input directly influencing Xcel’s commitment to monitoring.
A push for high-quality, publicly accessible data
Hayes said PSCo, Xcel’s Colorado subsidiary, agreed at a Dec. 2 meeting to conduct fenceline air monitoring, which measures air pollution at the boundary of a facility. Xcel spokesperson Sydney Isenberg confirmed the commitment to Boulder Reporting Lab.
“The details of the program are under development,” Isenberg said in an email.
Hayes expects sensors to count PM10 and PM2.5 along the edge of the property to track how much dust leaves the site. But he considers that the “bare minimum,” because simple particle counts don’t show what the particles are made of.
Previously, Xcel spokesperson Michelle Aguayo said the company will comply with all state air quality requirements.
Helmig and county officials say a more protective system would use research-grade instruments that continuously measure not just particle size, but black carbon, hydrocarbons and other contaminants, along with wind direction and speed to show where pollution is moving. That level of detail, they argue, is essential for understanding real exposure and identifying when Xcel’s operations might be causing problems.
The difference in data quality can be dramatic. At Boulder Reservoir, for example, Boulder AIR recorded more than 8,500 annual data points for methane. The state recorded 60.
Helmig said that, if the project is funded, the data would be presented in an accessible format for non-experts through a dedicated Valmont page on the Boulder AIR website.
“Collecting data is one point, but then interpreting the data is another,” Helmig said.
Residents say Xcel should not be the sole keeper of the information. “We wouldn’t feel like that was sufficient for our peace of mind,” Murillo said, citing past difficulties accessing coal ash data. Boulder Reporting Lab had to hire expert consultants during its 2023 investigation to interpret Xcel’s reporting of groundwater contaminant data.
Accountability and enforcement limits
Once cleanup begins, county health officials will only be able to cite Xcel if they can show that dust has left the property. Hayes said the county’s enforcement ability is limited, though it can escalate complaints to the state, which can issue penalties. He noted the challenge of investigating dust complaints at the Cemex plant near Lyons, where conditions often changed before county staff arrived.
“What will be the situation with Valmont coal ash removal is we will monitor, we will respond to complaints. If we see an exceedance, then we will report that to the state and hope that they will take enforcement action,” Hayes said.
State review of Xcel’s revised cleanup plans, resubmitted in September, is ongoing. A separate groundwater treatment plan, filed in November, is expected to be approved early this year.