PMC: a successful rehabilitation in Wyoming

A subsidiary of AREVA, Pathfinder Mines Corporation (PMC) mined large uranium deposits in the state of Wyoming.

Mining activities ceased in the early 1990s, and the company proceeded with full rehabilitation of both closed mines. The company now plans to transfer ownership of the storage site for ore treatment residues to the Department of Energy (DOE).

The rehabilitation works were carried out under the regulatory framework of  3 different agencies:

• The US Nuclear Regulatory Commission (NRC) , which regulates and approves rehabilitation plans for residue storage plants and basins
•  The US Environmental Protection Agency (EPA), which regulates air and water quality
•  The Wyoming Department of Environmental Quality (WDEQ), which regulates and approves rehabilitation plans for mining sites (excluding storage plants and basins) and regulates the air and water quality at these sites

Two sites redeveloped and transferred to the safety authorities

The Lucky Mc deposit

This deposit was subjected to underground and open-pit mining between 1957 and 1988. The total production was calculated at 18,000 metric tons, with an average uranium content of 1.71%.

Rehabilitation of the Lucky site began in 1991.

• The areas mined using the open-pit method have been levelled and replanted.
• The uranium processing plant was demolished in 1993.
• The storage basins for ore treatment residue were first restored to their proper levels and then covered with a layer of clay (between 0.3 meters and 1 meter), providing protection against radon emissions.
• The clay itself is covered with a rock layer in order to prevent any erosion for 1,00 years. After an observation period,  the basins will become the property of the American Department of Energy (DOE), which ensures its maintenance and long-term monitoring.

The Shirley Basin deposit

This deposit was used for underground, open-pit and ISL (In Situ Lixivation) mining from 1959 to 1992. A total of 10,000 metric tons were produced, with an average uranium content of 1.29%. 235 million cubic meters were extracted.

Rehabilitation of the site began in 1992.

• The open-pit mines have been levelled and replanted.
• A decontamination plan for the storage of waste from the ore treatment plant was approved by the Nuclear Regulatory Commission (NRC) in 1999. The works consist of:
  • extracting the water from the waste to consolidate the ore treatment residue,
  • cleaning up underground waterways affected by the waste infiltration – once the compaction process is finished, a layer of anti-radon clay then a rock layer is put in place to prevent erosion.   

The land affected by the open-pit mines were levelled and replanted.

These works, begun in 2004, have been completed. A slot is now open in the storage basins for ore treatment residue to place affected products from the dismantling and rehabilitation of legacy mining sites, with the authorization of regulatory bodies. The transfer of ownership of these basins to the DOE will only happen once the residual slot has been closed.

Contact

PATHFINDER Mines Corporation (PMC)
P.O. Box 730935 Pendell Boulevard
82644 Mills, Wyoming, USA
Tel.: +1 307-234-5019 
Fax: +1 307-473-7306