The Monte Cristo Mining Area (MCMA) includes abandoned
gold mines, processing facilities and haulage ways that
primarily operated from about 1893 to 1907 in a remote
area of the northern Cascade Range in Washington.
Lands in the MCMA are a patchwork of Forest Service administered
lands, patented claims, Inventoried Roadless
Areas (IRA), and the Henry M. Jackson (HMJ) Wilderness.
Abandoned mines and processing operations resulted in
elevated concentrations of metal contaminants, primarily
arsenic and lead, along a 9.5-mile stretch of the South
Fork Sauk River and tributaries.
A Removal Action (RA) was
conducted by Cascade Earth Sciences in 2015 to address
physical and chemical hazards associated with a mill,
assay shack, mines, ore collection terminals, and haulage
ways. Removal of approximately 2,000 yards of waste
rock from the Pride of the Woods Mine (located within the
HMJ Wilderness) necessitated the use of a Vertol 107-II
heavy-lift helicopter to both transport excavators to the
remote location, and to transfer material to the repository.
This project is a 2017 American Council of Engineering Companies of Oregon (ACEC) Engineering Excellence Award recipient. In conjunction with the U.S. Forest Service, the CES team successfully implemented removal action for the Monte Cristo Mining Area (MCMA).
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The Azurite Mine is an abandoned gold mine in a remote area in the North Cascades of Washington State. Since 2004, CES has been working for Region 6 of the Forest Service on this CERCLA project, including the Site Inspection, Reprocessing Study, Removal Design, and Removal Action implementation. The Removal Action began in July 2011 under a design-build contract structure with CES, and was completed at the end of September 2011. The repository was constructed on a 2.5:1 slope, and the liner consisted of a traditional HDPE liner and other geomembranes, along with a geogrid and a talus rock cover to blend in with the surrounding area. All borrow material was generated onsite because hauling material to the site was impractical. There will also be ongoing semi-annual inspections to monitor the constructed repository, revegetation, and to collect aquatic samples to assess the success of the Removal Action.