Superfund Information Systems: Site Profile

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The California Gulch site consists of about 18 square miles in Lake County, Colorado. The area includes the city of Leadville, parts of the Leadville Historic Mining District and a section of the Arkansas River from the confluence of California Gulch downstream to the confluence of Two-Bit Gulch. Former mining operations contributed to metals contamination in surface water, groundwater, soil and sediment. Cleanup is complete at several areas of the site. Operation and maintenance activities at these areas are ongoing. Cleanup of the remaining areas is ongoing.

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What Is Being Done to Clean Up the Site?

The site is being addressed through federal, state and PRP actions.

Since 1995, EPA and site PRPs have conducted removal and remedial activities to consolidate, contain and control more than 350,000 cubic yards of contaminated soils, sediments and mine-processing wastes. Cleanups by the PRPs included drainage controls to prevent acid mine runoff, consolidation and capping of mine piles, cleanup of residential properties, and reuse of slag.

EPA has conducted several five-year reviews at the site. These reviews ensure that the remedies put in place protect public health and the environment, and function as intended by site decision documents. The most recent review concluded that response actions at the site are in accordance with the remedy selected by EPA and that the remedy continues to be protective of human health and the environment in the short-term. Ongoing actions to ensure the long-term protectiveness of the remedy include review of institutional controls for OUs 1, 2, 4 and 10, implementation of institutional controls for OU5, possible additional investigations in OU3, and updates and implementation of operation and maintenance plans for OUs 5 and 7.

EPA placed the site on the NPL in September 1983 and has deleted OUs 1, 2, 3, 4, 5, 7, 8, 9 and 10 from the NPL.

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What Is the Current Site Status?

EPA divided the site into 12 areas, identified as operable units (OUs).

Map of operable units (PDF) (2 pp, 8.1 MB, About PDF)

OU1, Yak Tunnel: The Yak water treatment plant began operating in 1992. Water quality in the Arkansas River has substantially improved. The water treatment plant is now operated by Resurrection Mining Company, a potentially responsible party (PRP) under a Consent Decree settlement with EPA and the State of Colorado. Water treatment is ongoing.

OU2, Malta Gulch: OU2 encompasses the Malta Gulch drainage. After construction completion, the Malta Gulch Tailing Impoundment and Malta Tailing Impoundment remained. Lake County provides institutional controls for these impoundments, as the properties are zoned for industrial mining. EPA deleted OU2 from the Superfund program’s National Priorities List (NPL) in June 2001.

OU3, Denver and Rio Grande Railroad Slag Piles, Railroad Easement, Railroad Yard, and the Mineral Belt Trail: Union Pacific, a PRP, removed and consolidated the Harrison Street slag pile into the Arkansas Valley slag pile. Based on current land use, EPA determined that slag does not pose elevated health risks. Lake County adopted amendments to the Lake County Land Development Code in February 2009 that provide institutional controls. Operation and maintenance activities are ongoing.

OU4, Upper California Gulch: This OU encompasses the California Gulch watershed above the portal for the Yak Tunnel. Resurrection Mining Company, the PRP, has constructed water diversion channels and settling ponds to prevent heavy metals from flowing into surface water.

OU5, ASARCO Smelter/Colorado Zinc-Lead Mill Site: OU5 addresses contaminants associated with historic smelter sites around Leadville, and one mill site. Smelter waste, waste rock and tailings from the milling process were consolidated and capped with a soil cover on site. Field work finished at this OU and institutional controls still need to be implemented. EPA assumed lead responsibility for OU5 following a bankruptcy settlement with ASARCO.

OU6, Stray Horse Gulch: The long-term remedy included improving the clean water diversion systems along the Mahala, Pyrenees, Greenback, RAM, Old and New Mikado, and Adelaide-Ward waste rock piles, capping additional mine waste rock piles to decrease the volume of acid rock drainage (ARD) generated, enhancing the current ARD collection system and retention ponds, eliminating the use of the Leadville Mine Drainage Tunnel (LMDT) and reclamation treatment plant except in case of emergencies, shifting monitoring of groundwater and water levels in the LMDT to the OU12 sitewide surface and groundwater remedy, siting and constructing a sitewide repository in OU6, and implementing land use restrictions to protect engineered remedies and reduce exposure to contaminants that will remain in place. Design of the remedy is ongoing.

OU7, Apache Tailings: ASARCO consolidated and capped this tailings pile in 2002. EPA assumed lead responsibility for OU7 following a bankruptcy settlement with ASARCO.

OU8, Lower California Gulch: In 2002, Resurrection Mining Company removing tailings and non-residential soils and stabilized a channel in the 500-year floodplain. Lake County adopted amendments to the Lake County Land Development Code in February 2009, providing institutional controls for the OU. EPA deleted OU8 from the NPL in January 2010.

OU9, Populated Residential Areas: OU9 addresses lead contamination in the residential areas of Leadville and Lake County. In 1995, ASARCO launched “Kids First,” a program aimed at reducing young children's exposure to lead and to provide information about lead to the community. A 1999 Record of Decision outlined a similar program called the Lake County Community Health Program (LCCHP). Performance goals for the remedy were met in 2006. In the summer of 2009, EPA completed soil sampling and remediation for property owners that responded to a final call. EPA deleted OU9 from the NPL in September 2011.

OU10, Oregon Gulch: OU10 encompasses the lower portion of the Oregon Gulch drainage and includes the Oregon Gulch Tailing Impoundment owned by Resurrection Mining Company. Lake County provides institutional controls on this tailing impoundment, as the property is zoned for industrial mining. EPA deleted this OU from the NPL in April 2001.

OU11, Arkansas River Floodplain: EPA signed a Record of Decision in 2005 and field work finished in 2010. EPA will continue to monitor the revegetated areas and provide maintenance as needed until the reclaimed areas are determined to be mature and self-sustaining. Institutional controls still need to be implemented. EPA and the state assumed lead responsibility for OU11 following a bankruptcy settlement with ASARCO and a Consent Decree settlement with Resurrection Mining Company.

OU12, Sitewide Surface and Groundwater Quality: EPA and the state assumed lead responsibility for OU12 following a bankruptcy settlement with ASARCO and a Consent Decree settlement with Resurrection Mining Company. The long-term remedy included long-term monitoring, a technical impracticability waiver for specific action levels and institutional controls. Monitoring is ongoing.

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EPA’s Involvement at the Site

Mining, mineral processing and smelting activities at the site and nearby have produced gold, silver, lead and zinc for more than 130 years. Mining in the Leadville area began in 1859 when prospectors working in the channels of the Arkansas River tributaries discovered gold at the mouth of California Gulch. Wastes generated during the mining and ore processing activities contained metals such as arsenic and lead at levels posing a threat to human health and the environment. These wastes remained on the land surface and migrated through the environment by washing into streams and leaching contaminants into surface water and groundwater. Investigation of the site began in the mid-1980s.

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