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Central City/Clear Creek

This site is one of the "Superfund" hazardous waste sites in Colorado. A site qualifies for the National Priorities List (NPL or Superfund list) when the U.S. Environmental Protection Agency (EPA) determines there is a release or threatened release of hazardous substances that may endanger public health, welfare or the environment. In Colorado, the lead agency for Superfund remediation may be either the EPA or the Colorado Department of Public Health and Environment (the state health department).





The Central City/Clear Creek Superfund site is located in Clear Creek and Gilpin counties, approximately 30 miles west of Denver.  The Superfund study area covers the 400-square mile drainage basin of Clear Creek, which has been affected by a number of inactive precious metal mines.  The Superfund investigation has focused on mine drainage tunnels and mine tailings and waste rock piles.


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Gold was discovered near Idaho Springs in 1859, and in the BlackHawk/Central City area in 1860.  For the next 20 years, the Black Hawk/Central City area was the leading mining center in Colorado with the construction of mills to process the gold and silver found through placer and hard rock mining.  The decline of mining in the area began with the silver crash in the 1890's and the rise in mining in Leadville.  However, mining continued to be an important industry in Clear Creek and Gilpin counties from the turn of the century until appoximately 1950.  Since 1950, mining in the area has been limited wih only a handful of mines currently operating.


The site was placed on the list of Superfund sites in September 1983.  Since that time, the Department, EPA and the local community have worked to clean up heavy metal contamination resulting from decades of hard rock mining in the area.  The Department and EPA have developed cleanup plans to deal with the worst sources of contamination within the Clear Creek watershed.


In 1992, limited stakes gaming began in Central City and Black Hawk.  Introduction of gambling has led to some land use changes.  While these changes have the potential to increase the direct human exposure to mine wastes, many mine waste cleanup projects were implemented as property developed.

The most significant environmental impacts associated with the site are the impacts on the Clear Creek stream system that include a reduced fishery and significant impacts to other aquatic life and habitat.  Acidic mine water that drains from many mines contains various heavy metals, and mine wastes such as tailings and waste rock contribute to the non-point source impacts to the basin.  Clear Creek is a drinking water source for more than one-quarter million people living in the Denver area, and is a favored place for kayaking, rafting, fishing, wildlife watching and gold panning.  The human health hazard from this site involves potential exposure to heavy metals, primarily lead, arsenic and cadmium.  Soil from the tailings piles and waste rock contains heavy metals.

The clean up plans for the Central City/Clear Creek Superfund site call for treatment of contaminated water discharging from a number of different mines, capping of tailings and waste rock piles determined to be the largest sources of contamination, further investigation of ground water, and t plans to identify contaminated domestic wells and provide the owners with an alternate supply of drinking water.


The Argo Tunnel, in Idaho Springs, is the largest single source of metals contamination to Clear Creek. Construction of a 700 gallon per minute treatment facility was completed in 1998.  Full time operation of the treatment plant began in April 1998.  Approximately 1200 pounds of metals are prevented from entering Clear Creek each day due to treatment of the Argo Tunnel.  The removed metals are pressed into a solid waste and disposed of in a solid waste landfill.  The treated water is discharged into Clear Creek.


At the Burleigh Tunnel in Silver Plume, the Department constructed a pilot scale passive treatment system to test an alternative technology for treating acid mine discharge.  Although original results were promising, the technology was determined not to be appropriate for treating the contaminated water flowing from the Burleigh Tunnel and the pilot system was dismantled in 1999.  The Department and EPA contiue to monitor water quality in the vicintiy and are exploring other options for the Burleigh Tunnel.


Cleanup of priority waste piles began in 1993 and is on-going.  Since 1993, the Department and EPA have worked with a number of government entities, developers, individual property owners and community stakeholders to complete cleanup work at twelve priority waste pile locations.  Waste piles remediated in Clear Creek County include the Minnesota Mine near Empire, the McClelland Tailings near Dumont and the Black Eagle and Little Bear waste piles near Idaho Springs.  In the Black Hawk/Central City area, cleanup has been completed at the Millsite #11 and #12, Chase Gulch #1, Gregory Incline, Gregory #1, Gregory #2, National Tunnel, Clay County, North Clear Creek, Big Five and Boodle Mill waste piles. Additional mine waste pile cleanups are scheduled.


The Department and EPA are also taking steps to address groundwater contamination in select portions of the Superfund study area.  Virginia Canyon drains the mountain canyons north of Idaho Springs. Groundwater in the vicinity of Virginia Canyon is contaminated by the large concentration of abandoned mines in the area.  Groundwater flow is concentrated by the canyon and enters Clear Creek just upstream of the Argo Tunnel treatment facility.  The Department is evaluating the potential means and viability of extacting the contaminated groundwater with future plans to pump the groundwater to the Argo facility for treatment.


The agencies have also taken steps to protect individual homeowners who might be drinking contaminated water from domestic wells.  From 1994 through 1996, the Department operated a voluntary residential well testing program.  Under the program, owners of domestic wells were offered free well water sampling and analysis.  Owners whose well water contained levels of metals that exceeded drinking water standards were supplied with bottled water.   Only a small percentage of the wells tested required an alternate source of drinking water, and those homes have been receiving bottled water ever since.  The Department is in the process of selecting long term alternative drinking water sources for the homes affected by contaminated well water.


The Department and EPA will complete remediation work required by existing cleanup plans.  The agencies have also been working with local watershed stakeholders to identify significant sources of contamination not covered by existing plans.  The goal of this process is to complete work outlined in existing plans, identify and determine apporprate cleanup plans for significant contamination sources not included in existing work plans and over the long term, to complete the Superfund cleanup of the Clear Creek Watershed.  


Steve Laudeman, State Project Manager - Overall Coordination



Jim Lewis, State Project Manager - Operation and Maintenance of Waste Piles



Mary Boardman, State Project Manager - Argo Tunnel Treatment Plant, OU 4 Water Treatment]



Warren Smith, State Community Involvement Coordinator


(888) 569-1831 ext. 3373 toll-free outside 303/720 area code


Mike Holmes, EPA Remedial Project Manager



Peggy Linn, EPA Community Involvement Coordinator


(800) 227-8917 ext 6622 toll-free outside 303/720 area code



The State Highway 119 Mine Drainage Pipeline Project is now complete.  For questions or comments on the project, contact:


Steve Laudeman, State Project Manager - Overall Coordination


Warren Smith, State Community Involvement Manager
888-569-1831 Ext. 3373   toll-free outside the 303/720 area code




Abandoned mines and related waste piles in the Clear Creek watershed produce acidic, metal-rich water that drains into the creek. These contaminants include zinc, copper, manganese and cadmium which are harmful to fish and other aquatic life. US EPA placed the Central City / Clear Creek site on the National Priorities List in 1983. The Colorado Department of Public Health and Environment has the technical lead for the cleanup, which focuses on water quality goals rather than individual tasks.


Operable Unit (OU) 4 is on the North Fork of the Clear Creek watershed.  In 2010, EPA approved a Proposed Plan to Amend the Record of Decision for the active treatment of contaminated water from OU4, paving the way for design and construction of a new active water treatment plant. K.R. Swerdfeger Construction was hired in early 2011 to construct a pipeline to convey contaminated water to the site of the planned treatment plant south of Black Hawk. Construction began in May 2011 and was completed in May 2012. The Colorado Department of Transportation has an active highway-straightening project under way on State Highway 119 adjacent to the pipeline construction site.


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