Overview of Current Lava Cap Mine Superfund Site Investigation and Remediation

Dr. G. Fred Lee

US EPA Technical Assistance Grant Advisor to SYRCL

July 28, 2002

During the past year the US EPA Region 9, through its contractor, CH2M Hill, has completed several reports as part of the Lava Cap Mine Superfund Site Remedial Investigation (RI)/Feasibility Study (FS). These reports have provided considerable information on the degree of contamination of the surface soils in the mine site area, along Little Clipper Creek, Clipper Creek, at the Deposition Area just upstream of Lost Lake, at Lost Lake, and downstream of Lost Lake. Also, some information has been provided on the contamination of groundwaters from natural sources and mine tailings waste-derived arsenic. Additional studies are underway by the US EPA to fill information gaps on the degree and extent of the contamination of the area impacted by the Lava Cap Mine. Of particular concern in these followup studies is the potential for dust, which contains tailings-arsenic, to be a health threat. Additional information on groundwater contamination by mine tailings-derived arsenic and natural sources and to better define the degree of contamination of surface soils downstream of Lost Lake is also under investigation. A report covering these supplemental investigations will be released by the US EPA.

It has been found that arsenic, derived from the tailings and from groundwater seeps from the mine, as well as arsenic associated with tailings present at the mine site and downstream along Little Clipper Creek, Clipper Creek, in the tailings Deposition area just upstream of Lost Lake, at Lost Lake, and downstream of Lost Lake, is present at sufficient concentrations to be a public health threat to those who come in contact over an extended period of time with the arsenic-contaminated water and/or tailings present in the area. In addition, the concentrations of several heavy metals, such as antimony, cadmium, copper, lead, mercury, silver and zinc and the non-heavy metal cyanide are present at sufficient concentrations in some of the tailings-impacted areas to be a threat to wildlife. Many of the tailings-impacted areas will require remediation/cleanup to reduce/eliminate the threat to human health and wildlife.

This past winter, the US EPA released a preliminary draft Feasibility Study which provides an overview discussion of the potential approaches that the Agency is considering for remediation of the Lava Cap Mine tailings-arsenic-contaminated areas. Some preliminary cost estimates were developed by the US EPA contractor, which indicated that the costs for remediation involving excavation of the contaminated tailings areas with disposal on-site (near the area) in a new landfill would be on the order of $34 million. Excavation and off-site disposal in an out-of-the-area landfill costs would be about $100 million. These costs do not include the true long-term monitoring and maintenance cost of landfilling to ensure that tailings and arsenic-contaminated soils deposited in the landfills would not, at some time in the future, be released to the environment again. It is expected that the US EPA will release an updated Feasibility Study report, which provides additional information on potential remediation approaches. The public in the area will be asked to provide their comments on the various approaches that are being considered for remediation as part of developing a Record of Decision (ROD) for remediation of the Lava Cap Mine Superfund Site.

Dr. G. Fred Lee has recently completed an overview paper “Occurrence of Public Health and Environmental Hazards and Potential Remediation of Arsenic-Containing Soils, Sediments, Surface Water and Groundwater at the Lava Cap Mine Superfund Site in Nevada County, California.” This paper was presented at the “Fifth International Conference on Arsenic Exposure and Health Effects” that was held in San Diego, July 14 to 18, 2002. The paper will be published in the proceedings of this conference, would should appear in the next year. Pre-prints of this paper are available from Dr. Lee via email, gfredlee@aol.com. It will also soon be posted on Dr. Lee’s website in the Lava Cap Mine Superfund Site section, www.gfredlee.com. In addition, Dr. Lee’s reports to SYRCL on the RI/FS are available from this website.