Formosa Mine: Douglas County, Oregon | Region 10 | US EPA

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Formosa Mine: Douglas County, Oregon

The Formosa Mine Superfund Site is located on Silver Butte, about 10 miles south of the town of Riddle, in Douglas County,Oregon. The site was added to the National Priorities List (NPL) in 2007.

The acid rock drainage flowing from the mine and mine materials have severely degraded 13 miles of Middle Creek and the South Fork of Middle Creek, affecting macroinvertebrates, resident fish, coastal steelhead trout, and Oregon coastal coho salmon. EPA has completed a remedial investigation for Operable Unit 1 of the site. A feasibility study to evaluate cleanup alternatives will be available in 2013.

Final OU1 Feasibility Study Report (PDF) (451 pp, 12MB) - January 31, 2013
Final Remedial Investigation for Operable Unit 1 (PDF) (265 pp, 10MB)
Download appendices, tables, figures, etc. for the RI report from our FTP file repository: ftp://ftp.epa.gov/reg10ftp/sites/formosa

The final Formosa Mine Public Health Assessment has been released by Agency for Toxic Substances and Disease Registry (ATSDR) and the Oregon Department of Human Services Environmental Health Assessment Program.

The Data Summary Report (PDF) (413 pp. 15.25MB) summarizes existing information about the site. Note: This file is large and may take over thirty (30) minutes to download on a 56K modem connection.

The Sampling Plan (PDF) (318 pp. 18.3MB) documents the information that needs to be collected in order to complete this project. Note: This file is large and may take over thirty (30) minutes to download on a 56K modem connection.

The Community Involvement Plan (PDF) (6 pp. 72K) summarizes what we will do to make sure that we can hear and respond to your concerns and questions about the site and future proposed cleanup plans.

A diversion system at the site is being maintained cooperatively between EPA, the Oregon Department of Ecology, and the Bureau of Land Management to keep contaminated water away from the creek.

Photo Gallery


Acid Mine Drainage from the Formosa Mine has killed all life in the south fork of Middle Creek.

Officials from EPA, BLM, ODEQ and Douglas County reflect on what is needed to clean up the site.

A water diversion system has been attempted to keep some of the contamination from the south fork of Middle Creek
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