Hidden Hazard: Boulder’s Million-Ton Coal Ash Problem Has No Local Watchdog

More than 90 years of burning coal for electricity at Xcel Energy's Valmont Power Station left a little-known legacy of chemical waste at Boulder’s edge. The powdery residue of burned coal—known as coal ash—was removed over decades from inside smokestacks and boilers and transferred into several nearby landfills and storage ponds on site. 

Today, most of the dry ash lies underground in an unlined landfill owned by Xcel just east of Boulder city limits. The dump sprawls nearly 15 acres between Valmont Butte and Leggett Reservoir, largely out of public sight and mind. Yet hidden behind a grassy hill is 1.6 million tons of coal ash waste that could fill almost 500 Olympic-sized swimming pools or pave more than 2,000 miles of road. Xcel has admitted in public documents that the ash—which contains a blend of minerals such as quartz and clay, as well as toxic heavy metals—is in direct contact with groundwater, but the company has yet to implement a cleanup plan. Xcel’s own public models raise concern that the contamination is spreading toward residential areas. 

In 2015, the U.S. Environmental Protection Agency approved the first regulation governing storage and monitoring of waste at more than a thousand coal ash dumps nationwide. Under the rule, Xcel is required to test groundwater for dangerous contaminants at Valmont and make its data public. It has done this since 2017. 

For six consecutive years Xcel has reported groundwater contaminants at unsafe levels. These results have barely registered among Boulder area elected officials, raising questions about who is responsible for protecting the health of nearby residents.

For months, graduate students at the University of Colorado Boulder, along with Boulder Reporting Lab and the Center for Environmental Journalism, examined the extent of contamination from the coal ash site to understand potential impacts to human health and Xcel’s plans for cleanup. What’s happening at the Valmont Power Station is important not only for Boulder residents, but also for the six other communities in Colorado where Xcel has coal ash stored, and for the 42 other states where landfills exist—landfills that are often loosely regulated with little local oversight.