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California Gulch

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Site Description

The California Gulch Site is comprised of approximately 16.5 square miles of mountainous terrain in Lake County, Colorado, approximately 100 miles southwest of Denver. The Site is divided into 12 Operable Units. Operable Unit No. 6 (OU6) covers approximately 3.4 square miles in the northeastern quadrant of the Site and includes the Stray Horse Gulch watershed and the upper and lower portions of the Evans Gulch watershed. Historic mining activities resulted in the placement of mine wastes on the land surface. OU6 is designated Industrial Mining, with a small portion zoned residential. Stray Horse Gulch flows into residential areas of Leadville before flowing to California Gulch and the Arkansas River.

Current Site Status and Cleanup Actions to Date

  • Two operating water treatment plants treat acid mine drainage at a cost of approximately $1.5 million/year.
  • From 1994 through 2001, EPA and the Potentially Responsible Parties (PRPs) conducted removal and capping activities at large mill tailing piles and the removal or closure of several large tailing ponds. The current residential soil cleanup began in the mid-1990's and is anticipated to continue for at least three more years.
  • Removal Actions were conducted at OU6 to consolidate and cap five mine waste piles, close six mine shafts, control surface water drainage around eight acid generating mine wastes piles, rehabilitate Stray Horse Gulch drainage and remove sediments from the surface water drainages within OU6. The Record of Decision (ROD) for OU6 was signed in September of 2003. Cleanup remedy design work is currently underway.

Current Funding Status

  • Cleanup projects had not completed the design phase in Fiscal Year 2004; therefore, construction funding was not needed.
  • Projects that will need construction funding in the future involve plugging the LMDT, completing a dewatering well and constructing a pipeline to convey acidic metal laden water to the LMDT plant for treatment.
  • Region 8 plans to request construction funding for OU6 in Fiscal Year 2006.

For more information on the projects at this site, please read the California Gulch Fact Sheet on the Region 8 Superfund Web site.

Key Accomplishments

  • All construction involving waste rock piles in project Operable Unit No. 6 (OU6) is complete.
  • In 2000, contaminated surface water was diverted to the US Bureau of Reclamation's Leadville Mine Drainage Tunnel (LMDT) water treatment plant as part of EPA's water management Removal Action. A permanent arrangement for treatment of OU6 surface water and stabilization/plugging of the tunnel remain to complete the final remedy.
  • Two components of the remedy were completed during the summer of 2004.
    • The Emet mine crib wall was replaced. This was done to prevent continued leaching of metals and acid mine drainage to Stray Horse Gulch and the Arkansas River.
    • The Ponsderine waste rock pile was removed to prevent acidic metal laden water from re-contaminating residential soils.


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