Central City, Clear Creek is a Superfund site covering a 400-square-mile watershed in Gilpin and Clear Creek counties, Colorado. Historic mining and milling from 1859 through the mid-20th century left the area contaminated with heavy metals. EPA placed the site on the National Priorities List in September 1983, and cleanup work has been ongoing since the early 1980s.
The main contaminants are arsenic, cadmium, chromium, copper, lead, manganese, mercury, nickel, silver, and zinc. Aluminum, fluoride, iron, and chromium(VI) are also present. These chemicals have been found in groundwater, surface water, sediment, and solid waste. People can be exposed by drinking contaminated groundwater, ingesting mine tailings or waste rock, or inhaling airborne dust. Aquatic life in the watershed is also at risk.
Cleanup is organized into five operable units (OUs). OU1 addressed acid mine drainage but was later amended by OU3 after passive treatment proved infeasible. OU2 remedial actions are mostly complete except for the Quartz Hill tailings impoundment, which moved to OU4. OU3 involves passive and chemical treatment of tunnel discharges, and construction of a flow control structure at the Argo Tunnel is underway. OU4 work continues, with re-grading and vegetative capping of the Quartz Hill tailings pile planned soon. OU5, added in 2022, is investigating heavy metals in mine waste piles in residential areas. Two water treatment plants currently operate on site, and several mine waste piles have already been cleaned up.
Human exposure at the site is not currently under control, and contaminated groundwater migration is not stabilized. Physical construction is incomplete, and the site is not ready for its anticipated use. EPA's most recent five-year review, completed in May 2024, found the remedy remains protective of human health and the environment. However, EPA is also evaluating lead risks in soils and yards under an updated October 2025 Lead Directive, particularly for children under 7 and pregnant or nursing women. Residents with young children near the site are encouraged to test their children for lead annually if soil has not been replaced at their property.
Community members can stay informed by signing up for site updates through EPA. For questions about cleanup or redevelopment, residents can contact the EPA Community Involvement Coordinator, the Remedial Project Manager, or the Colorado Department of Public Health and Environment.
