EPA Superfund Site

LEVIATHAN MINE

CA | EPA ID CAD980673685

About this site’s exposure pathways: As of September 2023, the Leviathan Mine Superfund site is considered “Insufficient Data to make a Human Exposure evaluation” (HEID). The Leviathan Mine was finalized on the NPL on 5/11/2000, and there has not yet been an evaluation of the human health exposure risks.

EPA uses this Human Exposure status when there is insufficient data/evidence to determine whether actual or reasonably anticipated human exposures are occurring, and/or whether those exposures are above acceptable risk-based levels. The planned activities to collect sufficient information to make a human exposure evaluation are as follows: EPA is overseeing early response actions that address releases of mining-influenced water to a mountain stream system, but has not completed a risk assessment for the entire site to quantify any remaining exposure to humans. The Risk Assessment involves over nine miles of potentially contaminated riparian area downstream of the mine. The surface water is not used as drinking water. Quantification of human risk is also complicated by consideration of exposure patterns unique to the Washoe Tribe whose members use this watershed. The site's location at 7,000 feet in the Sierra Nevada allows only limited seasonal access. The data gathering for the formal risk assessment is underway with an Administrative Order issued on June 23, 2008. The Remedial Investigation/Feasibility Study (RI/FS) is expected to be completed over the next several years. EPA currently anticipates that there will be sufficient data to make a Human Exposure determination by 9/30/2025 because by then the evaluation of the RI and risk assessments will be completed.