Mining Program - Region 5 Success Stories
Empire Mine State Historic Park, Red Dirt Pile, Nevada County
Empire Mine State Historic Park, Red Dirt Pile, Nevada County
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Photographs of Mine Site
The Empire Mine was a large underground gold mine located in Nevada County near Grass Valley. The mine opened in 1850 and operated until 1956. A subsidiary of Newmont Mining Corporation operated the Empire Mine from the late 1920s until it closed in 1956. The Empire Mine is now owned by California Department of Parks and Recreation.
Newmont and State Parks have voluntarily agreed to participate in cleanup of mining waste at the Empire Mine State Historic Park. The majority of the tailings material was removed to the McLaughlin Mine for further processing in the late 1980s. One of the remaining major water quality issues was the Red Dirt Pile, a remnant sulfide tailing material stockpile. This tailings material, and the soil underneath the tailings material stockpile area, generated acidic leachate. The Red Dirt Pile had high concentrations of heavy metals and arsenic that were being transported by storm water runoff into Little Wolf Creek.
Tests performed on the Red Dirt Pile found an average pH of 3.6. It also had concentrations of lead as high as 6,000 mg/Kg and concentrations of arsenic as high as 2,460 mg/Kg. Material from the Red Dirt Pile often discharged into Little Wolf Creek when storm water flowed across the Red Dirt Pile. This caused the creek to have levels of lead and arsenic that exceeded drinking water standards.
Several steps were taken to remediate this problem. The first step was the re-grading of the area. Next, a clay cover was installed to prevent the percolation of water into the Red Dirt Pile. Cover material was placed over the clay cover and hydro-seeded. Finally, diversion channels were constructed to divert water around the site in order to prevent erosion of the cover. A parking lot was also built over part of the site. These measures prevent water from eroding the Red Dirt Pile, which prevents harmful chemicals from entering surface water.
This is a success because of the cooperative work between State Parks, Newmont, DTSC, and Central Valley Water Board. The completion of the step-by-step process taken at this site has prevented the percolation of water through the Red Dirt Pile tailings and associated degraded soils that contain high levels of lead and arsenic. The completion of this project has prevented harmful metals from entering surface water thus improving the water quality in surrounding streams.
