Sierra Zinc Mine

The site is the location of former lead and zinc mining and milling operations. Remnants of ore milling operations include a 25-acre tailings impoundment containing about 88,000 cubic yards of contaminated soils and mine waste.

Mining operations began at the site in 1889 and continued sporadically through the mid- to late 1970s. Lead and zinc ore deposits were mined at the site using underground mining techniques.  The mill was first built in 1941 and was expanded in 1949 to process as much as 500 tons of ore per day. The mill operated sporadically through the 1960s, however, little information is known about production totals.

Site investigations were conducted by the United States Environmental Protection Agency (EPA), Washington State Department of Natural Resources (DNR), and Resource and Environmental Management Consultants, Inc. (RMC) on behalf of The Goldfield Corporation.

Based on findings from the site investigations, removal actions were completed at the site between 2014 and 2016 that included excavating contaminated soils, tailings, and waste rock and disposing materials in the on-site tailings impoundment area. The demolition of the mill and administrative building was included as part of the removal action. The tailings impoundment was then covered with a 9-inch eco-barrier consisting of gravel, 18 inches of cover soil, and 6 inches of topsoil.

Following the removal action, institutional controls in the form of an environmental covenant was recorded with Stevens County to restrict certain activities and uses that interfere with the cleanup.

Ecology conducts periodic reviews every 5 years at sites that have institutional controls. The review is intended to examine the effectiveness of cleanup activities and to assure the continued protection of human health and the environment.

Periodic review results

• The cleanup actions completed at the site are protective of human health and the environment.
• Soil cleanup levels have not been met at the site; however, the cleanup action is determined to comply with cleanup standards under WAC 173-340-740(6)(f), since the long-term integrity of the containment system is ensured and the requirements for containment technologies have been met.
• The environmental covenant for the site is in place and will be effective in protecting public health and the environment from exposure to hazardous substances and protecting the integrity of the cleanup action.

Based on this five-year review, Ecology has determined that the requirements of the environmental covenant are being followed. No additional remedial actions are required by the property owner. It is the property owner’s responsibility to continue to inspect the site to assure that the integrity of the cap is maintained.