Mining Program - Region 5 Success Stories
The Jamestown Mine, Tailing Facility Closure, Tuolumne County

The Jamestown Mine, Tailing Facility Closure, Tuolumne County

  Photographs of Mine Site

The Jamestown Mine is a former gold mine located near Jamestown, Tuolomne County. The Sonora Mining Corporation owned and operated the mine while it was active, from 1986 to 1994. Presently, the land where the mine is located is owned by Tuolumne County and private owners. Settlement with the Sonora Mining Corporation and the owners created two trusts with funds to remediate and manage the mine.

Trust I funds were used to close the Tailings Management Facility (TIF) consisting of a tailings-filled lined depression surrounded by an embankment. A pond developed on the Tailings Management Facility which resulted in leachate (mine-influenced water or MIW) seeping through the embankment and through the leaky liner system. The leachate draining from the Tailings Management Facility had several constituents that exceeded one or more water quality criteria. It contained total dissolved solids concentrations around 2,700 mg/L, which exceeded agricultural beneficial use criteria. Sulfates were approximately 1,630 mg/L, exceeding the drinking water standard. The sodium levels were 250 mg/L, which is above the USEPA Health Advisory. It also had arsenic concentrations up to 0.028 mg/L, exceeding Federal drinking water standard. This leachate then seeped into ground water.

Remediation of the TIF began by draining the surface pond. Once the surface of tailings was sufficiently dry, it was graded to prevent future ponding. After the grading, a clay cap was installed, followed by placement of topsoil which was then seeded. A spillway was put in the embankment to prevent ponding of storm water on top of the unit. This is a success because the cover and further drainage of the tailing facility prevented leaching of harmful mine waste into the groundwater.

However, a mine site is rarely completely closed and free of maintenance and monitoring. Trust II funds are used for monitoring and maintenance of the site. Currently, the main challenge at the site is the rising water level in the Harvard Pit. The current water management strategy is the use of 11 evaporators in the pit. Other potential water management strategies are being considered.