The Black Butte Mine (BBM) is located in southern Lane County, in the Coast Fork Willamette River basin, approximately ten miles south of Cottage Grove, Oregon. The BBM is located on the northwest flank of Black Butte.
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The BBM is a former mercury mine. From 1927 to 1940, BBM was one of Oregon’s largest producers of mercury.
The primary features of the Site include a former mill structure containing a rotary kiln, mercury condenser, and ore storage/crushing equipment (New Furnace Area), another mill and furnace area (Old Ore Furnace), several old dilapidated buildings, a system of unimproved roads, mine adits, and piles of waste rock and mill tailings.
The pile of waste rock and mill tailings located in a relatively flat area below the New Furnace Area is referred to as the Main Tailings Pile. It is bordered on the northeast by Dennis Creek. Tailings on the northeast edge of the Main Tailings Pile dip steeply to the northeast toward Dennis Creek.
Potential human health and environmental impacts from historic mine wastes present at the BBM Site include public health and safety risks, increased metal concentrations in surface water, and increased sediment load to surface water. Elevated mercury levels in fish found in the Cottage Grove Reservoir pose health risks when eaten.
The BBM was identified in recent Total Maximum Daily Load (TMDL) investigations as a significant contributor of mercury to sediment and fish tissue in Cottage Grove Reservoir, located approximately six miles downstream of BBM. Cottage Grove Reservoir and the main stem of the Willamette River, is the nation’s thirteenth largest watershed. The Oregon Department of Human Services has issued health advisories to limit consumption of fish harvested from the Cottage Grove Reservoir due to elevated mercury concentrations in fish tissue.
The proposed action consists of excavation of mine tailings and contaminated soils consolidated beneath a soil capped repository constructed on-site. The identification of mine waste contaminated materials will be accomplished by removing the visible mine tailings, and with confirmation by systematic field screening of surface soils with a field portable X-ray fluorescence (FPXRF) instrument using ODEQ soil cleanup guidelines for mercury. The following excavation work is proposed:
•30,000 cubic yards tailings excavated from the Main Tailings Pile.
•3,000 cubic yards excavated from the Old Ore Furnace and Furnace Creek areas.
•2,000 cubic yards excavated from the New Furnace Area.
The cleanup goal for mercury in the Main Tailings Pile is 8 to 10 mg/kg (background levels). Cleanup in other highly contaminated areas identified above will be excavation, to the extent practicable, to less than EPA region 9 PRG of 115 mg/kg (adjusted for mercury sulfide).
Site work is expected to commence August 2007.