U.S. EPA to begin soil cleanup at homes, roads near Sulphur Bank Mercury Mine Superfund Site

The U.S. Environmental Protection Agency will begin work next week to remove contaminated mine waste from areas along Sulphur Bank Mine Road and Ward Road and several residential properties located to the south and west of the Sulphur Bank Mercury Mine Superfund Site near Clearlake Oaks, Calif.

Without the removal action, the EPA is concerned that residents may be exposed to harmful levels of mercury and arsenic that are present in mine waste that was used as construction material in the residential area. People can be exposed to mercury and arsenic by breathing air with contaminated dust or mercury vapor, incidental ingestion of contaminated soil or ingestion of contaminated water and food.

The EPA will spend approximately $800,000 to remove the contaminated material to prevent hazardous substances from coming into direct contact with area residents and from reaching Clear Lake. Crews will work through March to excavate approximately 2,500 cubic yards of contaminated soil and transport it to the disposal site at the Sulphur Bank Mercury Mine.

“All too often, abandoned mines have left behind a toxic legacy that continues to threaten the health of the people and natural resources of the area,” said Keith Takata, the EPA’s Superfund director for the Pacific Southwest region. “Removing the contaminated soil will protect public health and allow safe continued access to these areas.”
The EPA sampled soil in roadways and around homes and discovered elevated levels of mercury and arsenic present at 13 locations. Because contaminated mine waste was used to gravel areas adjacent to homes and garages and to maintain roadways, the contaminated soil is shallow -- generally between 6 to 12 inches in depth. The EPA will remove the contaminated soil, and backfill excavated areas and roadways to restore previously existing conditions.

The Sulphur Bank Mercury Mine is located on the shores of Clear Lake and began operations in the mid-1800s to recover sulfur and mercury. The mine closed in 1957, leaving approximately 3.5 million cubic yards of production waste scattered in four major waste piles on the 220-acre mine property. Miners also left behind a 90-foot deep, flooded open pit mine known as Herman Impoundment. Contaminated water flows from Herman Impoundment through waste rock into Clear Lake contaminating the sediments and the Clear Lake ecosystem.

The EPA added the site to the National Priorities List in 1990, and has conducted extensive field investigations to determine the nature and extent of contamination at the site. The agency has conducted a number of cleanup actions at the mine property to prevent erosion of mine wastes into Clear Lake, to control discharges of contaminated surface water from the mine, and to seal several improperly abandoned geothermal wells on the property. The EPA recently completed an extensive cleanup to excavate and remove contaminated mine wastes from residential yards and roadways at the nearby Elem Indian Colony.