Site Narrative
This mine was active from 1853 up to the 1950´s the entire mine consisted of surface benches, 5 adits, 4 shafts with a total of 1600´ of underground workings. Historic photographs of the mine showed that several structures were erected to house the workers and during the clean_up excavation historic whiskey, beer containers were found along with other historic debris, such as bathtubs and kitchen implements. The site also contained an improved water source for the mine along with two large metal water tanks. The furnace which was used to retort the ore was previously taken off location so little or no above ground structures were left.
The retorted calcines and furnace soot ranged in mercury concentration from 20_1,120 parts per million. The clean_up objective was developed based on the native bedrock (non_mercury ore) which has a background concentration of only 0.2 parts per million.
Reclamation/Recommendations
In the summer of 2000, restoration activities began with the removal of 8,000 cubic yards of mercury retort waste rock (calcines) and placement into a repository located adjacent to the site. All unearthed mining debris was also placed into the repository. The disturbed areas were recontoured and capped with two to three feet of non-mercury native soil. Native plant seeds from the adjacent vegetated areas were collected and then spread out under several inches of weed-free rice straw. To control erosion and stormwater runoff, rice straw hay bales were staked in the ground along the slope contours to help slow down the water and allow for the germination of the native plants. Total cost for restoration was $324,000.
During the winter of 2000/2001, two severe storms dumped over 4" of rain in the watershed above the restored site. The ephemeral drainage, which was recontoured through the site, overflowed and cut into the cap material causing extreme erosion. Creek reconstruction/stabilization will be initiated in the summer of 2002 or fall of 2003.
Risks: Water quality, Hg contamination
AMLIS #: CA021900001
Location: N
Field Office: Hollister
Congressional Distri: 17
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