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Klau/Buena Vista Mine

The  Klau and Buena Vista Mine  is located in San Luis Obispo County, California, 12 miles west of Paso Robles, California (EPA 2006). This site contains two deserted mercury mine sites (Klau and Buena Vista) in the California coastal mountains that cover about 250 acres. The mines contribute a significant amount of contaminant called mercury to downstream waters. Mercury is a metal that is a significant concern to humans because of how harmful an impact it can have on our nervous system. In order to protect human health and the environment, site investigations and long-term cleanup action are continuing.

History
The Klau and Buena Vista Mines were operational in the years of 1868-1970, where roughly 6.4 million pounds of mercury were produced (Public Health Assessment 2010). The soil, sediment, and surface water at the Klau and Buena Vista mines detected high concentrations of mercury, manganese, arsenic, and thallium; so in 1971, both mines were shut down. In 1999, the California Central Coast Regional Quality Control Board (RWQCB) requested that the EPA Region 9 Emergency Response Office contribute in preventing the ongoing discharge of mercury-laden contaminants from the Klau/Buena Vista Mine site. The EPA took action and removed 120,000 cubic yards of contaminated material to avert critical human health and environmental threats (EPA 2006). This site has had substantial work done to stabilize the site and reduce the discharge into Las Tablas Creek, but there still remains an uncontained amount of mercury-laden contaminants on the site. In 2006, EPA removed and recycled over 100 pounds of free mercury and 900 tons of mercury-contaminated soils and building debris in the emergency removal action plan (Public Health Assessment 2010).

Contaminants and Risks
The Klau and Buena Vista Mines contain an abundant amount of mercury, which exposed to, can have severe environmental and human health risks. Mercury (Hg) is an element found in the earth’s crust. Mercury contamination at both sites is the outcome from years of mercury mining and ore processing. Cleanup action indicated that the exposure pathways that risk human health are from consuming or touching contaminants in the soil and groundwater. First mercury is deposited into the air but then settles in the water, where methylmercury is highly toxic to fish, shellfish, and the other animals that eat fish (EPA 2006). Furthermore, fisheries and recreational users of the Las Tablas watershed are the main targets of mercury contamination from the Klau and Buena Vista Mines. Lastly, the health effects of exposure to high levels of mercury are harmful to a human’s brain, heart, lung, kidneys, and immune system, which can lead to cancer (World Health Organization 2016).

Investigations and Cleanup
In September 1997, the Klau Buena Vista site was identified as a potential hazardous waste site and entered into the Comprehensive Environmental Response, Compensation, and Liability Act Information System (Ecology and Environment Inc., 2001). During the Federal Register that took place in September of 2004, the EPA proposed that the Klau Buena Vista Mines should be added in the National Superfund List. Following numerous investigations upon the EPA's proposal, the Klau and Buena Vista Mines were officially classified as Superfund sites on April 16th of 2006. The Klau/Buena Vista Mines have been identified as the primary source of mercury contamination in Lake Nacimiento sediment (Health Consultation, 2007). EPA remains devoted to prioritizing and addressing these sites in order to protect the environmental and public health. EPA co-operates with tribes as well as local, state, and federal agencies to assess, manage and cleanup sites that present a threat to local communities. To date, EPA has obligated over $75 million toward mercury related mine site cleanups in California (Informational Hearing on Mercury and Abandoned Mine Lands, 2014).

The site has been sub-categorized into three units: Operable Unit No.1 (OU1), Operable Unit No.2 (OU2) and Operable Unit No.3 (OU3) (EPA 2006).

OU1 is comprised of the Klau and Buena Vista mines property, OU2 is comprised by the Las Tablas Creek Watershed, and OU3 is comprised by the Lake Nacimiento.

Removal actions that have dealt with critical threats to human health and environment were conducted from 2000 to 2011. In 2000, EPA extracted 120,000 cubic yards of contaminated materials from the drainage and moved them to a secure onsite repository. In 2002, a new sinkhole and slope failure on site were stabilized. In 2006, the mercury processing building as well as a variety of mercury-laden soils were removed (EPA 2006).In 2007, the EPA conducted a Remedial Investigation in order to further characterize the nature and extent of mercury in the site’s soil and water. A Phase I sampling event was conducted from September to November 2007. Phase II was completed in April 2008 (EPA 2006). This investigation was undertaken to help determine long-term cleanup actions for the site. In 2008, EPA addressed the seepage of AMD that flowed from the Buena Vista Mine Tailings repository into the drainage system. AMD is a term that describes the liquids that flow from the waste piles of the Klau Buena Vista mines (Public Health Assessment, 2010). These liquids have a very acidic pH (2-3) and elevated metal concentrations. Once in contact with water, they lower water's pH and elevate its metal concentrations (Public Health Assessment, 2010). In addition to the seepage addressing, EPA filled an additional sinkhole at the Klau Mine portion of the site and performed general site maintenance. In 2009, seven monitoring wells were drilled to evaluate hydrogeology and water quality in the mines. Finally, one of the most important projects was completed in 2010. In November 2010, the Nacimiento Water Project was completed, delivering drinking water to 100,000 San Luis Obispo residents (EPA, 2006).