Lava Cap Mine

Overview

Lava Cap Mine is a 33-acre former gold and silver mining site in the Sierra Foothills near Nevada City, California. EPA added it to the National Priorities List in January 1999. The site has been divided into four operable units covering mine tailings and surface water, groundwater, the Lost Lake area downstream, and former mine residences. Cleanup work began in 2005 and is still underway across several of those areas.

The main contaminant is arsenic, found in mine tailings, mine discharge water, Little Clipper Creek, Lost Lake, shallow groundwater under the tailings, and nearby drinking water wells. A long list of heavy metals, including lead, mercury, cadmium, copper, and zinc, also contaminate soil, sediment, and surface water in the mine area. Cyanide has been detected in soil, sediment, and surface water as well. Human exposure is not yet fully under control. EPA advises residents to avoid contact with tailings, rinse shoes and pets after walking near the area, and limit consumption of water and fish from Little Clipper Creek and Lost Lake. Catch-and-release fishing is currently recommended at Lost Lake.

Key cleanup actions already completed include fencing and cleaning mine buildings in 2006, capping the tailings pile, removing hazardous waste, demolishing mine residences and removing contaminated soil by April 2007, and completing a drinking water pipeline in 2014 so nearby residents could connect to municipal water. The groundwater remedial action finished in May 2016. A second remedial action phase for the tailings and surface water area started in 2024 and is estimated to wrap up between September and November 2027. EPA is designing a gravity-fed wetlands treatment system for contaminated mine drainage water, with construction expected in 2026. Solar panels are planned to reduce energy costs for that system. For the Lost Lake area, EPA is still studying how contaminants move through the ecosystem, and a revised feasibility study is expected in 2028.

Institutional controls restrict the mine area to non-residential uses. The most recent five-year review was completed in September 2021. EPA is conducting the next five-year review in 2026, with the report due by September 30, 2026. The site has not yet reached construction completion and remains on the National Priorities List.

Community members can read the September 2025 fact sheet on cleanup progress, available in English and Spanish. The fact sheet and other site records are available at the Grass Valley Public Library at 207 Mill Street and the Nevada City Public Library at 980 Helling Way. For questions, contact EPA's Community Involvement Coordinator Jackie Lane or Remedial Project Manager Brian Milton.