Case Summary: EPA Orders Mine Cleanup Work at Smith Lake and Mariano Lake Areas on the Navajo Nation

Under an August 27, 2014, Administrative Order on Consent (AOC) Homestake Mining Company of California  will assess contamination and address safety hazards at four abandoned uranium mines in the Mariano Lake and Smith Lake areas on the Navajo Nation. The U.S. Environmental Protection Agency (EPA) and Navajo Nation will oversee the work totaling about $500,000. Under the agreement, Homestake will also set aside funds for EPA’s oversight of future cleanup.

This work at the Mariano Lake and Smith Lake sites is part of a broader program to screen, assess, and clean up abandoned uranium mine sites throughout Navajo Nation. The lands of the Navajo Nation include 27,000 square miles spread over three states in the Four Corners area. In 2008, EPA, in partnership with the Department of Energy, Bureau of Indian Affairs, Indian Health Service and Nuclear Regulatory Commission, developed a five year plan to address the legacy of abandoned uranium mines on the Navajo Nation. A second five year plan was issued in 2014. For more information visit the Agency's Navajo Nations website Tronox Documents Web page. 

• Information about the Homestake Mining Company
• Information about the Sites
• Pollutants and Environmental Effects
• Summary of the Administrative Order on Consent
• Contact Information

“EPA has a polluter pays policy that seeks to make those responsible for environmental damage pay for the cleanup. This work, which will cost about $500,000, is another element in our partnership to deal with the toxic legacy of abandoned uranium mines."

Information about the Homestake Mining Company

Homestake Mining Company of California offers gold mining services and operates as a subsidiary of Barrick Gold Corporation. Homestake, in partnership with United Nuclear and their predecessors, operated the uranium mines.

Information about the Sites

The AOC covers four closed underground uranium mine sites: Black Jack Nos. 1 and 2 and Mac Nos. 1 and 2.

• Black Jack No. 1 mine area covers a mine lease surface area of approximately 24 acres and approximately 56 acres of underground workings. It is located in Section 12, Township 15 North, Range 13 West, about two miles northwest of Smith Lake on allotment land. Black Jack No. 1 operated from approximately 1959 through 1967 with additional deliveries from stockpiles of ore until approximately 1971.
• Black Jack No 2 mine area covers a mine lease surface area of approximately 14 acres and approximately 26 acres of underground workings. It is located in Section 18, Township 15 North, Range 13 West, about eight miles west of Smith Lake on allotment land. Black Jack No. 2 operated from approximately 1960 through 1964 with additional deliveries from stockpiles of ore until approximately 1970.
• Mac No. 1 covers a lease surface area of approximately 33 acres and 8 acres of underground workings. It is located in Section 12, Township 15 North, Range 14 east on allotment land. Mac No. 1 operated from approximately 1968 through 1971 with additional deliveries from stockpiles of ore until approximately 1980.
• Mac No. 2 covers a lease surface area of approximately 6 acres with approximately 10 acres of underground workings. It is located in Section 18, Township 15 North, Range 13 on allotment land. Mac No. 2 operated from approximately 1968 through 1970.

Additional information is available from the Agency’s Addressing Uranium Contamination on the Navajo Nation website.

Pollutants and Environmental Effects

The unique geology of the Navajo Nation lands makes them rich in uranium, a radioactive ore in high demand after the development of atomic power and weapons at the close of World War II in the 1940s. Preliminary screening of each of these mine areas show elevated readings of Radium-226. Radium-226 is a known human carcinogen, and exposure may be a precursor to bone, liver and breast cancers and other health conditions.

Summary of the Administrative Order on Consent

The AOC provides for Homestake to perform the following activities at each of the four mine sites as part of an interim removal action over the next several months. These activities include:

• determining background concentrations and gamma radiation levels of contaminants of potential concern;
• conducting a thorough investigation, including gamma scanning and soil sampling of the contamination on the mine sites and mine site-related contamination in the vicinity;
• preparing a removal site evaluation that documents the findings of the investigation; and
• posting hazard signs around the mine sites and identifying and addressing physical hazards at the mine sites.

This work is the first phase of cleaning up the uranium contamination at the four mine sites and is expected to be completed by fall 2015.

Contact Information

For more information contact

Rebekah Reynolds
Assistant Regional Counsel
Region 9
U.S. Environmental Protection Agency
75 Hawthorne Street (ORC-3)
San Francisco, CA 94105
415-972-3916
reynolds.rebekah@epa.gov