California Gulch/Yak Tunnel Superfund Site

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 (CDPHE).

Site Summary	Site Remediation
Environmental Concerns	Related Web Sites
Site Map	Superfund Site List

Proposed Modification to Operable Unit 6 - Stray Horse Gulch

California Gulch Virtual Forum - the Public's site for information and input

Upper Arkansas River Basin Natural Resource Assessment - Preliminary Estimate of Damages - December 2006

Doug Jamison
State Project Manager
(303) 692-3404
(888) 569-1831 ext 3404 toll-free

Warren Smith
State Community Involvement Coordinator
(303) 692-3373
(888) 569-1831 ext 3373 toll-free

Site Summary

Location

The 15 square mile California Gulch site is comprised of the town of Leadville (population 3,300), the adjacent mining district in Lake County, and the watershed of California Gulch which flows westward through Leadville to the Arkansas River. Along the 7.25 mile length of California Gulch are many slag piles, tailings piles, waste rock piles, and abandoned mine structures. The 4 mile long Yak Tunnel drains numerous underground mines before discharging into California Gulch.

History

Mining in the Leadville area began in 1859 with the discovery of placer gold in California Gulch followed by silver and lead finds in the 1870's. Area mines produced significant quantities of zinc, lead, and copper through World War II, but mining activity has since virtually ceased. However, over 120 years of mining, ore processing and smelting have resulted in approximately 2,000 waste piles at the California Gulch site.

The site was placed on the list of Superfund sites in September 1983 and was divided into 12 geographically-based areas, also called operable units or OUs, in 1994. Operable Units 2 and 10 were deleted from the National Priorities list in 2001. Subunits A and B, residential waste rock piles and parks and playgrounds located within Operable Unit 9 were deleted in 2002.

Environmental Concerns

Chemicals

The primary health concern is exposure to lead in soils by children age six or younger. Also, elevated metals concentrations in the Arkansas River have impacted aquatic life.

Exposure

Young children may be exposed to lead from ingestion of contaminated soil, household dust and water. More than 60% of the residential surface soils sampled in 1986 had lead levels greater than 1,000 parts per million (ppm). A 1991 study funded by ASARCO found that, overall, 8% of the children less than or equal to 6 years of age tested had blood lead levels greater than 10 ug/dL. In two areas of town, 25% and 21% of the children had blood lead levels greater than or equal to 10 ug/dL. In 1999, 11.5% of the new children tested by the county had blood lead levels greater than or equal to 10 ug/dL.

Cadmium and arsenic levels in soil are also elevated in some areas of the site. Cadmium does not pose a significant health risk. Arsenic will be addressed under a site-wide Institutional Control Overlay (ICO) District program.

Several shallow groundwater wells in California Gulch and some private wells have samples exceeding EPA drinking water standards for cadmium and zinc. In addition, some surface water samples contain high levels of zinc, cadmium and other metals. The municipal drinking water source for Leadville, which comes from Evans Gulch, does not contain elevated metals.

Site Remediation

In 1986, EPA extended public water supply system lines to residences using private wells. Remediation began in 1988 to minimize the flow of acidic water from the Yak Tunnel. Cleanup consists of a surge pond, water treatment plant and a groundwater monitoring network. The water treatment plant began operation in Spring 1992. EPA has designated additional Operable Units (OUs), and environmental sampling has been done to address remediation of Leadville residential areas, surface and groundwater and the affected terrestrial and aquatic environment. Children's exposure to lead is being addressed on an interim basis by the voluntary "Kids First" program, funded by ASARCO. This program addresses potential exposure to lead from various media including: soils, lead paint, household dust and tap water. EPA has recently selected the Lake County Community Health Program as the final remedy for the residential area of the Site. In many respects, the community health program will function as a continuation of the interim "Kids First" program. "Source area" cleanup activities are also underway at localities in California, Stray Horse and Oregon Gulches that have been identified as contamination sources to surface and groundwater. Settlement of Natural Resource Damages (NRDs) has begun pursuant to a Memorandum of Understanding (MOU) process that was agreed to by all of the involved parties in the spring of 1999.

Hazardous Materials and Waste Management Division California Gulch/Yak Tunnel