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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 over 90 percent of the site. Operation and maintenance activities at these areas are ongoing. Cleanup of the remaining areas is ongoing.

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What Has Been Done to Clean Up the Site?

EPA placed the site on the NPL in September 1983 and has partially deleted OUs 1, 2, 3, 4, 5, 7, 8, 9 and 10 from the NPL. Actions in OU6 and OU12 are being monitored for effectiveness. OU11 is in operations and maintenance.

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 EPA and 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 remedies selected by EPA and that the remedies continues to be protective of human health and the environment. A recommendation in the 2017 five-year review to ensure the long-term protectiveness of the OU11 remedy is to finalize an institutional control.

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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 – partially deleted from NPL: 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 Newmont Mining Company, parent to 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 – partially deleted from the NPL: 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. Operations and maintenance is conducted by the State of Colorado.

OU3, Denver and Rio Grande Railroad Slag Piles, Railroad Easement, Railroad Yard, and the Mineral Belt Trail – partially deleted from the NPL: EPA determined that fine slag poses elevated health risks if inhaled. In the late 1990s, the slag piles, including fine slag, at Poverty Flats and the Harrison Street property were relocated to the AV slag pile. Lake County adopted amendments to the Lake County Land Development Code in February 2009 that provide institutional controls, which requires State approval for building permits on OU3 properties. Poverty Flats (the Old Railyard) is currently being developed into a multi-use complex with 200+ residential, commercial, and recreational properties.

OU4, Upper California Gulch – partially deleted from the NPL: 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 – partially deleted from the NPL: 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. EPA assumed lead responsibility for OU5 following a bankruptcy settlement with ASARCO. Field work finished at this OU. Operations and maintenance is conducted by the State of Colorado.

OU6, Stray Horse Gulch – remedial design: The long-term remedy included a phased approach. Phase 1 is improving the clean water diversion systems along the Mahala, Pyrenees, Greenback, RAM, Old and New Mikado, and Adelaide-Ward waste rock piles. Phase 2, if needed, includes capping additional mine waste rock piles to decrease the volume of acid rock drainage (ARD) generated. Phase 3 is 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. Other components of the remedy are 1. shifting monitoring of groundwater and water levels in the LMDT to the OU12 sitewide surface and groundwater remedy, 2. siting and constructing a sitewide repository in OU6, and 3. implementing land use restrictions to protect engineered remedies and reduce exposure to contaminants that will remain in place. The sitewide repository was completed in 2012. The diversion ditch up-gradient of the Mikado, RAM and Pyreness waste rock piles was re-engineered in 2016 to better divert clean water into No Name Gulch and ultimately in California Gulch. The effectiveness of this diversion is being monitored. Design of the remaining remedy components is ongoing.

OU7, Apache Tailings – partially deleted from the NPL: ASARCO consolidated and capped this tailings pile in 2002. EPA assumed lead responsibility for OU7 following a bankruptcy settlement with ASARCO. Operations and maintenance is conducted by the State of Colorado.

OU8, Lower California Gulch – partially deleted from the NPL: In 2002, Resurrection Mining Company removed tailings, 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 – partially deleted from the NPL: 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. LCCHP Phase 2 program serves as the institutional control. The program provides education and outreach on the ways to prevent exposure to lead, free blood-lead testing, environmental investigation and remediation of lead services when a child has an elevated blood-lead.

OU10, Oregon Gulch – partially deleted from the NPL: 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 – operations and maintenance: EPA signed a Record of Decision in 2005 and field work finished in 2010. The State will continue to monitor the revegetated areas and provide maintenance as needed. 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. In 2014, the Colorado Parks and Wildlife Commission honored the site with a Gold Metal Trout Waters designation. The designation highlights the Upper Arkansas River's improved water quality and revitalized habitats for trout and other wildlife. Funded with Natural Resource Damage Settlement monies, Colorado Parks and Wildlife enhanced fish habitat in the Arkansas River in 2015 and 2016.

OU12, Sitewide Surface and Groundwater Quality – remedial action: 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 includes long-term water quality monitoring of groundwater and surface water including the Arkansas River, a technical impracticability waiver for metals in groundwater along California Gulch, and institutional controls. Water quality standards for zinc and cadmium in the Upper Arkansas River past the point of compliance (downstream of the confluence of California Gulch) are being met.

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