|Klau/Buena Vista Mine||San Luis Obispo County, California|
|San Luis Obispo County||22nd Congressional District|
The Klau/Buena Vista Mine is located in San Luis Obispo County, approximately 12 miles west of Paso Robles, California. The Klau/Buena Vista Mine consists of two abandoned mercury mine sites (Klau and Buena Vista) that are located on adjacent properties on a northwest southeast trending ridge of the Santa Lucia Range in the California coastal mountains. They share the same ownership, nature of operations and source types, target populations, aquifers, and water bodies.
Mercury mining and ore processing operations occurred at the Buena Vista Mine and adjacent Klau Mine between 1868 and 1970. Buena Vista Mines, Inc., has owned the Buena Vista Mine since at least 1957 and the Klau Mine since at least 1964. At the Buena Vista Mine, tailings were deposited in a drainage channel on the Buena Vista Mine property next to the North Fork of Las Tablas Creek. Other sources of contamination at the Buena Vista Mine include, but are not limited to, the Bureau of Land Management (BLM) Reservoir Dam; tunnels, drifts, stopes, and adits associated with the underground mine workings; an open pit; and the ore processing mill. At the Klau Mine, the main tailings pile is located on a hillside on the north side of the Klau Branch. The lower edge of the pile extends to Cypress Mountain Road and to within a few feet of the Klau Branch. Other sources of contamination at the Klau Mine include, but are not limited to, tailings and overburden piles; a pond covering approximately 2 acres (Klau Pond); a smaller pond (Western Klau Pond); and underground mine workings.
The most significant contaminant of concern is mercury, which has been detected in downgradient sediments at concentrations more than six times higher than background concentrations. Additionally, arsenic and thallium have been detected onsite in easily-eroded material at concentrations that exceed EPA's Preliminary Remediation Goals for industrial soils. Drainage from the mine has been reported as very acidic. The predominant hazardous substances in acid mine drainage from the site are iron and manganese, with aluminum, boron, mercury, nickel, selenium, thallium, and zinc also being reported at concentrations exceeding the California Central Coast Regional Water Quality Control Board (RWQCB) waste discharge requirements. Analytical data has shown that runoff water contains concentrations of mercury and thallium in excess of Maximum Contaminant Levels (MCLs).
Potential Impacts on Surrounding Community/Environment:
Mercury mining and ore processing has resulted in mercury contamination to nearby surface water bodies and significant bioaccumulation of mercury in several fish species. Several impacted surface water bodies are known to be used as major recreational areas and fisheries by local people and tourists. Additionally, the Nacimiento Reservoir is used as a direct source of drinking water by some lakeshore residents. Construction is set to begin in 2009 on a project to provide drinking water directly from Lake Nacimiento to approximately 110,000 residents in San Luis Obispo County.
Response Activities (to date):
In 1999, the RWQCB requested that the EPA Region 9 Emergency Response Office (ERO) assist in preventing the continued release of mercury-laden sediments from the site. In 2000, EPA removed 120,000 cubic yards of contaminated materials from the drainage channel and secured it in an onsite repository to prevent immediate threats to human health and the environment. Substantial site stabilization work was also conducted. These actions have reduced acid mine drainage and metals discharge into Las Tablas Creek, but uncontained contamination remains both on and off the site. In 2002-2003, EPA stabilized a sinkhole on site. In 2005, EPA stabilized a slope failure on site. Contaminated materials stored onsite are temporarily capped and will be addressed in the site's long-term cleanup.
[The description of the site (release) is based on information available at the time the site was evaluated with the HRS. The description may change as additional information is gathered on the sources and extent of contamination. See 56 FR 5600, February 11, 1991, or subsequent FR notices.]
For more information about the hazardous substances identified in this narrative summary, including general information regarding the effects of exposure to these substances on human health, please see the Agency for Toxic Substances and Disease Registry (ATSDR) ToxFAQs. ATSDR ToxFAQs can be found on the Internet at ATSDR - ToxFAQs (http://www.atsdr.cdc.gov/toxfaqs/index.asp) or by telephone at 1-888-42-ATSDR or 1-888-422-8737.