Pacific Southwest, Region 9: Superfund
Serving Arizona, California, Hawaii, Nevada, the Pacific Islands, and Tribal Nations
Klau Buena Vista Mine
EPA #: CA1141190578
County: San Luis Obispo
City: Paso Robles
Congressional District: 20
Other Names: Buena Vista Klau Mine
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Description and History
NPL Listing History
NPL Status: Final
Proposed Date: 09/23/04
Final Date: 04/19/06
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 ridge of the Santa Lucia Range in the California coastal mountains. 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 at least since 1957 and the Klau Mine since at least 1964. The most significant contaminant of concern is mercury, a metal that can be harmful to the human nervous system. In 1999, the California Central Coast Regional Water Quality Control Board (RWQCB) requested that the EPA Region 9 Emergency Response Office assist in preventing the continued release of mercury-laden sediments and other contaminants from the site. Substantial site stabilization work was conducted. These actions have reduced the discharge of acid mine drainage (AMD) and discharge into Las Tablas Creek, but uncontained contamination remains on the site. The remedial investigation began in 2007. Phase I sampling for the remedial investigation was completed in November 2007. Soil, sediment, surface water and biota were sampled. Phase II sampling of surface water and biota was completed in April 2008. Concurrent with the remedial investigation activities, EPA Emergency Response staff returned to the site in Summer 2008 to address seepage of acid mine drainage from the Buena Vista Mine Tailings repository, fill in a new sinkhole at the Klau Mine portion of the site, and perform general site maintenance.A data summary of the Phase I and II sampling was released in October 2008 and work was begun on both the human health risk assessment and screening level ecological risk assessment. Additional sampling of a second stormwater event and the installation of groundwater monitoring wells was conducted in mid-2009. The final Remedial Investigation Report, which will incorporate the risk assessments, was available in October 2012. The Feasibility Study was completed in January 2014 and as a result of data gaps, a two year bioreactor treatability study is planned and a Feasibility Study addendum will be prepared documenting the results.
Contaminants and Risks
- Surface Water
- Soil and Sludges
The main concern for this site is the effect of mercury contamination from the mining operations on targets such as fisheries and recreational users of the Las Tablas watershed.
Mercury may exist in mine waste from source areas on the site. Some source areas are seeps from the mine site, which contain AMD. Predominant hazardous substances in the AMD from the site are iron, manganese, aluminum, boron, mercury, nickel, selenium, thallium, and zinc.
These metals also pose concern since their concentrations exceed the RWQCB waste discharge requirements. Data indicated that runoff water contains concentrations of mercury and thallium in excess of Maximum Contaminant Levels (MCLs are enforceable regulatory standards under the Safe Drinking Water Act). Other source areas of contamination are mine tailings that remain on the property; the Bureau of Land Management (BLM) Reservoir Dam; tunnels, drifts, stopes, and adits associated with the underground mine workings; and an open pit.
The Klau/Buena Vista Mines Superfund Site was placed on the National Priority List April 16, 2006. The Site has been subdivided into three operable units; Operable Unit No. 1 (OU1) consisting of the Klau and Buena Vista Mines property, which is owned by the Buena Vista Mines, Inc. (BVMI), which has owned the Buena Vista Mine since at least 1957 and the Klau Mine since at least 1964; Operable Unit No. 2 (OU2), consisting of the Las Tablas Creek Watershed starting at the confluence of the North and South Forks of Las Tablas Creek and extending northward to the Las Tablas Creek arm of Lake Nacimiento, stopping at the boundary between the Harcourt Reservoir and Las Tablas Creek Arm of Lake Nacimiento Reservoir; and Operable Unit No. 3 consisting of Lake Nacimiento.
Mercury loading, methylation, and biological uptake are occurring downstream from the mine site in Lake Nacimiento reservoir, which has public health advisories concerning the consumption of game fish. One of the goals of this RI/FS will be to better understand the relationship between mercury contamination in the mining areas and in Las Tablas Creek Watershed with the mercury contamination in Lake Nacimiento reservoir.
The Buena Vista/Klau Mine Site consists of three Operable Units:
Operable Unit No. 1 consists of the two adjacent abandoned mine sites which encompass approximately 317 acres, and include five miles of underground workings, a two acre mine pit, and slopes comprised of approximately 300,000 tons of mine tailings, overburden and waste rock. The area around the Site is characterized by steep topography, with elevations ranging from 1,050 feet to more than 1,600 feet.
The properties, known as the Buena Vista Mine (BVM) and the Klau Mine (KM), are owned by BVMI and are located approximately 12 miles west of Paso Robles, San Luis Obispo County on a northwest- southeast trending ridge of the Santa Lucia Range in central California. Mineral extraction in the vicinity of the site began in the late 1860's and continued until 1970. During mining operations, mining waste, including waste rock, tailings and mercury extraction wastes were dumped in drainage channels situated downstream from the mines.
Operable Unit No. 2 consists of Las Tablas Creek Watershed and is characterized by land used primarily for rangeland, agricultural farming, vineyards, and recreation. The climate is Mediterranean with cool wet winters and warm dry summers. There is typically little or no rainfall from May to November. The average rainfall varies dramatically in the watershed due to orographic effects within the Santa Lucia Range. Rainfall in Paso Robles to the east can range from 10 to 15 inches while in the area of the Klau/Buena Mines has been estimated as high as 30 to 40 inches per year.
Operable Unit No. 3 consists of Lake Nacimiento, which is located on the Nacimiento River about 18 miles northwest of Paso Robles in San Luis Obispo County. It was created by the construction of Nacimiento Dam in 1957. The lake’s irregular shoreline comprises about 165 miles. The reservoir’s maximum capacity is 377,900 acre feet with a surface elevation of 800 feet and surface area of 5,400 acres. The maximum depth of the lake is 175 feet, with annual fluctuations usually ranging from 30 to 70 feet. The reservoir’s location in the rugged Santa Lucia Mountains results in rapid runoff due to it’s geologic features and, thus, fills rapidly. The Nacimiento Dam is an earth-fill dam with a height of 215 feet above the streambed and a crest length of 1,650 feet. The crest elevation is 825’ above mean sea level (msl) with a spillway elevation of 800 feet msl and capacity of 70,000 cfs. The dam has two outlets, the high level outlet works located under the center of the spillway at an elevation of 755’, and the Low Level Outlet Works on the south side of the dam at an elevation of 670’, resulting in the bottom 60 feet of the reservoir acting as a dead pool.
In 1959, San Luis Obispo County obtained an entitlement to 17,500 acre-feet of water from the Nacimiento Reservoir, which is being currently developed . The Nacimiento Water Project is designed to convey drinking water to approximately 100,000 San Luis Obispo residents and is estimated to cost $150 million. The project involves the construction of a 45 mile pipeline, three tanks and multi-level intake facility at the dam. The project was completed in November 2010.
The final cleanup approach will be determined once the nature and extent of contamination has been identified. Phase I sampling for the remedial investigation was completed in November 2007. Soil, sediment, surface water and biota were sampled. Phase II sampling was completed in April 2008. A followup data gaps sampling of surface water and groundwater was conducted in mid-2009. In September/October 2009, seven monitoring wells were installed to evaluate site hydrogeology. In November 2009, an RI of sediments in Las Tablas Creek (OU2) was initiated, to evaluate past releases from the site. A draft OU2 remedial investigation report was completed in 2012. In August 2010, an RI of Lake Nacimiento (OU3) was started. A draft OU3 Remedial Investigation Report is estimated to be complete in 2015. In addition, in late 2011, a site stabilization emergency response was attempted to address recent landslides on the site. However, it was not successful. This issue will be addressed as part of the Site Remedy.
Removal actions to address immediate threats to human health and the environment were conducted in 2000, 2002, 2006, 2008, 2010, and 2011. 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. In 2002, EPA stabilized a sinkhole on site and also stabilized a slope failure on site. In 2006, EPA removed the mercury processing building (retort) and some mercury-laden soils. Contaminated materials stored onsite are temporarily capped and will be addressed in the site’s long-term cleanup. Concurrent with the remedial investigation activities, EPA Emergency Response staff returned to the site in Summer 2008 to address seepage of acid mine drainage from the Buena Vista Mine Tailings repository, fill in a new sinkhole at the Klau Mine portion of the site, and perform general site maintenance.
Cleanup Results to Date
Short-term removal work involved site stabilization, which reduced the discharge of acid mine drainage (AMD) and discharge into Las Tablas Creek. 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. In 2002, EPA stabilized a sinkhole on site and also stabilized a slope failure on site. In 2006, EPA removed the mercury processing building (retort) and some mercury-laden soils. Contaminated materials stored onsite are temporarily capped and will be addressed in the site’s long-term cleanup.
A Remedial Investigation (RI) to further assess the nature and extent of mercury in soil and water at the site commenced in 2007. A Phase I sampling event was conducted from September to November 2007. Phase II was completed in April 2008. The remedial investigation will help EPA determine long-term cleanup actions for the site. In the meantime, state and local authorities have numerous health advisories in place, warning anglers of the hazards of eating mercury-contaminated fish. EPA conducted community interviews and developed a Community Involvement Plan (CIP). A Community Advisory Group was also formed. Community Advisory Group meetings have been held in March and November 2008, November 2011 and November 2012. Further community activities will be scheduled as events unfold.
Potentially Responsible Parties
Potentially responsible parties (PRPs) refers to companies that are potentially responsible for generating, transporting, or disposing of the hazardous waste found at the site.
Buena Vista Mines, Inc.
Documents and Reports
Public Meetings: A number of public meetings and a formal comment period will occur as more site information becomes available. Typically, these events occur when the remedial investigation is released and the choice of the preferred cleanup method is announced. These meetings and comment periods will be announced through fact sheets and public notices advertised in the Paso Robles Press and the San Luis Obispo Tribune. EPA Community Involvement Coordinator, Sarah Cafasso, is assigned to work with the community on the Klau/Buena Vista Mine site. She is available to answer questions, maintain the mailing list and coordinate community involvement activities, including the Technical Assistant Grant (TAG) program.
A Community Involvement Plan (CIP) was developed to provide information to the affected community and gather community concerns, issues and questions so they may be considered when a cleanup remedy is chosen. The CIP includes interviews and comments from local residents, elected officials and other interested parties.
April 2007 - Community Involvement Plan -
Public Information Repositories
The public information repositories for the site are at the following locations:
Paso Robles Public Library
1000 Spring Street, Paso Robles, CA 93446
Mon-Fri 10 am to 8 pm
Sat 10 am to 5 pm
EPA Site Manager
Mail Code SFD
75 Hawthorne Street
San Francisco, CA 94105
EPA Community Involvement Coordinator
Mail Code SFD
75 Hawthorne Street
San Francisco, CA 94105
EPA Public Information Center
8800 Cal Center Drive
Sacramento, Ca 95862-3200
Bureau of Land Management
3801 Pegasus Drive
Bakersfield, Ca 93308
After Hours (Emergency Response)