The property was discovered in 1872 and worked intermittently until about 1961. Total production is estimated at 3000 flasks of mercury. Mine development on the southeast side of the property is reported to comprise 7000 feet of adits and tunnels on several levels. According to land status maps and a recent survey conducted by the BLM in 1997, BLM holdings are limited to a stream reach north of the mill site and a few hundred feet along Pozo Creek (see photo and map above). Both of these areas contain mine waste and tailings which are the focus of the BLM environmental investigation. The mill site is on both private ground and Forest Service land. Most, if not all, of the underground workings are under Forest Service land.

CERCLA Actions

The CERCLA cleanup was preformed at the Rinconada mercury mine site during FY2004-5, under an EPA emergency response CERCLA action in cooperation with the US Forest Service and BLM (see EPA press release). During early 2004, preliminary sampling for mercury was completed, a temporary fence was erected to restrict entry and the two main access portals were closed using a combination of polyurethane foam and boulders. During 2004-5 approximately 9,000 tons of mercury tailings and mill waste was excavated and shipped off site to several designated hazardous waste repositories in the San Joaquin Valley. In addition, two small historic mercury retort furnaces on BLM land were removed and the elevated concentration mercury wastes were shipped off site. Post remediation monitoring (water, sediment, and biota) will occur during FY2006-9. CERCLA remediation cost expenditures are estimated at $2.3 Million.