Blue Ledge Mine Clean-up

 

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The US Forest Service successfully completed a $15 million non-time-critical removal action at the abandoned Blue Ledge Mine superfund site situated on patented land in remote, rugged mountains just south of the Oregon-California border in the fall of 2011.

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With over two miles of underground workings on ten levels, it was one of the largest mines in mineral-rich SW Oregon and northern California from 1902 through the 1920s, with intermittent development continuing through the 1940s. The mine is a massive sulfides deposit that was primarily developed for copper and zinc, but also yielded gold, silver, and lead. (left) Aerial view of Blue Ledge Mine in Oregon during waste removal.


For over 100 years the run-off destroyed virtually all aquatic life in the four miles of Joe Creek that passes directly below the waste rock piles. Miners dumped over 150,000 tons of sulfides-rich waste rock on the extremely steep mountain slopes located below 13 adits. Four distinct waste rock piles covered more than 12 acres. The waste rock piles became the source of highly toxic metal-rich acid mine drainage that discharged 500,000 gallons per day into drainages at peak flow during spring runoff. (right) Spider Backhoe moving soil on upper waste pile 1.

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 The two-season long removal action excavated over 66,500 cubic yards of waste rock from the steep slopes and hauled it to a sealed repository. The repository was constructed about 1.5 miles from the mine.
Poor access, steep cliffs, rock fall, and extremely hazardous conditions presented substantial challenges to the contractor. (left) Spider Backhoe working in waste pile 1 below shaft. 

Cleanup standards required waste rock removal down to background metals concentrations in the soil, or within ½” of bedrock, whichever came first. (right) Workers from Engineering/Remediation Resource Group, Inc. below bench on waste pile 2.

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The contractor chose to use up to three spider excavators to climb up the 380-450 waste rock piles to remove the waste rock from the top down, until the pile could be reached by conventional excavators and dozers. As many as 23 laborers in rock climbing gear and ropes followed closely behind the spider excavators. Laborers used picks, shovels and brooms to clear waste rock down to bedrock. (left) Where no clean soil was encountered under the waste pile, removal crew cleaned the site down to within 1/2" of bedrock.

Handheld X- ray fluorescence equipment was used to field verify cleanup success, followed by laboratory confirmation. Five off-highway 35-ton articulated dump trucks hauled over 5,000 loads of waste rock down steep access roads, with some constructed at 30% grades. Helicopters ferried a mini excavator, 30,000 lbs of reclamation materials, and 20,000 pounds of steel for 10 bat gates custom constructed at the adit portals. (right) Cleaning waste rock out of the old channel on waste pile.

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Reclamation included placing clean topsoil on the more gentle slopes, planting 10,000 native shrubs and trees grown for the project, riprap lining 1,800’ of drainage channel banks, installing 600 square yards of slope stabilization mesh, and placing native grass seed and mulch on about 20 acres of disturbed ground. (left) Mulching around plants to help reduce grass competition and better retain soil moisture.

Approximately 1,300’ of log wattles and 2,600’ of straw wattles were installed on the steep slopes where clean soil remained following waste rock removal. All disturbed soils were covered with straw, hydromulch, bark mulch, slash, or riprap. (right) The re-vegetation crew planted 10,000 locally grown native conifers, hardwoods, shrubs representing 18 different species.

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The successful public lands cleanup was funded with $12.5 million from the American Recovery and Reinvestment Act, and $2.5 million from a CERCLA cost-recovery claim negotiated between the Department of Justice and ASARCO. URS from Portland, Oregon provided the removal design. The general contractor was Engineering/Remediation Resources Group located in Martinez, California. The earthworks subcontractor was Granite Construction from Sacramento, California.