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| KLAU/BUENA VISTA MINE | San Luis Obispo County, California | |
| San Luis Obispo County | 22nd Congressional District |
Site Location/Size:
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.
Site History:
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.
Site Contamination/Contaminants:
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 http://www.atsdr.cdc.gov/toxfaq.html or by telephone at 1-888-42-ATSDR or 1-888-422-8737.