The Denver Radium Site spans more than 65 properties along the South Platte River in Denver, Colorado. Radium processing in the 1900s left behind contaminated soil, groundwater, buildings, and debris across the area. EPA added the site to the National Priorities List (NPL) in 1983 and organized the cleanup into 11 operable units (OUs) to manage the work in pieces.
Radium is the most widespread contaminant, found in soil, solid waste, buildings, and groundwater at multiple locations. Other contaminants include arsenic, lead, uranium, molybdenum, selenium, radon, thorium-230, antimony, zinc, lindane, and volatile organic compounds (VOCs). These appear primarily in soil and groundwater, with the Shattuck property carrying the broadest range of contaminants. Gamma radiation and radon gas produced by radium decay are the main health concerns. Human exposure is currently under control across the entire site, meaning no unacceptable exposure pathways exist right now. Groundwater migration status, however, remains uncertain due to insufficient data, and monitoring continues to clarify whether contaminated groundwater movement is stable.
Cleanup actions included excavating and disposing of contaminated soils off-site, installing vapor barriers and concrete caps, and setting up groundwater monitoring. Construction was completed on September 27, 2006. Ten of the 11 operable units have been deleted from the NPL after EPA and the State of Colorado confirmed cleanup was complete. Only OU 8's groundwater remains on the NPL and is still actively monitored by the Colorado Department of Public Health and Environment (CDPHE) and EPA. Six operable units still have waste left in place under protective institutional controls, including land use restrictions, groundwater use prohibitions, excavation alerts, and indoor air monitoring. A five-year review completed on September 7, 2023 concluded that cleanup actions protect human health and the environment. The next review is estimated between September and November 2028.
Many cleaned-up properties have been put back to productive use. These include Ruby Hill Park, Evans Station Lofts with 224 apartments, a Home Depot retail store, and other commercial and community spaces. As of December 2024, the site supported 104 on-site businesses employing 1,242 people and generating roughly $232.95 million in annual sales revenue.
Community members can contact EPA's Community Involvement Coordinator or Remedial Project Manager. For state-related questions, contact CDPHE. Site documents are available through EPA's online system or by calling the Superfund Records Center at 303-312-7273.
