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.  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.