Sierra Zinc Mine

We are providing an opportunity for public review and comment on the periodic review conducted at the Sierra Zinc Mine site, located in Stevens County, about 24 miles north of Colville, Washington.

Based on this periodic review, Ecology found that no additional cleanup actions are required at this time.

We review sites about every five years after a cleanup action when institutional controls are used as part of the cleanup. The purpose of the periodic review is to evaluate current site conditions and to ensure continued protection of human health and the environment.

We will review comments received during the comment period and make recommendations for suggested changes. The periodic review will become final if no significant changes are made. We will hold an additional public comment period if we make significant changes.

Site Background

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.

Institutional controls can be fences, signs, or restrictions on how the property is used. For instance, an institutional control may prohibit installing drinking water wells or disturbing a protective cap that isolates contamination. These restrictions keep the contamination contained and keep people from being exposed to the contamination. The controls are usually listed in environmental covenants recorded with the county.