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Our
Expertise . . . |
Mine Reclamation Projects
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Glenn Springs Holdings, Inc., Ducktown, Tennessee, USA
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Golder Associates, Inc./Dynamac Corporation/Bureau of
Land Management, Vernal, Utah, USA
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Homestake Mining Company, Colorado, USA
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Mesa County, Department of Public Works, Mesa County,
Colorado, USA
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U.S. Borax, Inc., Lila C. Mine Closure, Death Valley
Junction, California, USA
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U.S. Borax, Inc., Old Borate Mine Closure, Mojave
Desert, California, USA
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West Ridge Resources, Inc., Price, Utah, USA
Glenn Springs Holdings, Inc., Boyd Mine Subsidence Evaluation, Ducktown,
Tennessee, USA
An evaluation of
subsidence was performed at the inactive Boyd copper mine to identify
potential for future surface collapse. In 1971, a purported failure of
a 50-ft-wide pillar separating two large, unsupported stopes occurred at the
600-ft level, which initiated collapse of the crown pillar. The size
of the stopes, approximately 1250 ft on strike and up to 300-ft high,
sustained caving upward along the dipping ore vein until forming a
200-ft-diameter sinkhole at the surface. At the time of the study, the
sinkhold measured nominally 500 ft in diameter and was flooded to within 250
ft on the surface. AAI conducted a site visit and reviewed archival
information to develop a digital map of the mine workings which incorporated
plan and longitudinal sections of the stopes. Stope plan maps by level
were combined with surface imagery to identify and rank future subsidence
hazard areas. Available technology for monitoring ground response and
warning of potential collapse was investigated, including aerial
photogrammetric surveying, time domain reflectometry, microseismic
monitoring, ground penetrating radar, seismic tomography, and other
geophysical methods.
Golder Associates, Inc./Dynamac Corporation/Bureau of Land Management, White
River Oil Shale Mine Closure, Vernal, Utah, USA
The goal of the project
was to provide design recommendations for permanent closure of three deep
shafts and an adit in an explosive environment. The mine was classified as
gassy, and had experienced two methane explosions in the 30-ft-diameter
service shaft. AAI evaluated shaft and mine construction, existing shaft
conditions, and conducted a hydrogeological evaluation in support of the
reclamation design. AAI selected backfill by mine waste rock as the
preferred alternative for closure. A plan was devised to cast backfill
material into the shafts without sparking an explosion, using inert gases.
Estimated costs of the native material backfill plan will result in
significant savings compared to conventional cast-in-place concrete shaft
plugs.
Homestake Mining Company, Pitch Reclamation Project,
Colorado, USA
An evaluation of pit-wide slope stability was conducted for a
700-ft-deep, inactive, uranium mine pit. The evaluation was conducted in
support of reclamation activities by Homestake. Numerical simulation of
complex slope displacement, that was inadequately reproduced by limit
equilibrium methods, was conducted using the discrete element code, UDEC.
Limit equilibrium analyses were conducted for slopes exhibiting more
conventional modes of failure. The models were extended to predict future
slope performance in response to worst-case historic piezometric conditions.
Mesa County, Department of Public Works, Slope Stability Evaluation of a
Reclaimed Slope, Durant Pit—Mesa County, Colorado, USA
Mesa County had reclaimed a sand and gravel pit highwall by grading
to a 2H:1V slope, contour furrowing, and successfully seeding the slope.
Unfortunately, the reclamation plan stipulated a 3H:1V slope or flatter. The
Colorado Division of Minerals and Geology requested that stability analyses
be conducted to demonstrate stability of the model. AAI collected soil
samples, designed a comprehensive laboratory testing program, analyzed
laboratory data, and conducted slope stability analyses. The evaluation
revealed that the existing slope is expected to be stable.
U.S. Borax, Inc., Lila C.
Mine Closure, Death Valley Junction, California, USA
AAI was challenged by U.S. Borax to develop a closure method for
the 80-year-old Lila C. borate mine that was environmentally sound, used
native materials to the extent possible, and provided permanent closure of
the mine openings. AAI developed an innovative approach that met these
requirements at a cost well below conventional closure methods. AAI
provided engineering design, cost estimating, and construction management to
complete the project.
U.S. Borax, Inc., Old Borate Mine Closure,
Mojave Desert, California, USA
AAI has recently provided engineering support to U.S. Borax for the
first phase of mine closure at the historic Old Borate Mining District.
During Phase I, 120 mine openings were closed. The remaining mine
openings are scheduled for closure within a three-year period. AAI
provided design recommendations for closure of the mine openings and
assisted U.S. Borax in bid document preparation, contract development, and
construction management. Creative solutions using native materials
resulted in very cost-effective permanent mine closure.
West Ridge Resources, Inc.,
Reclaimed Slope Stability Evaluation, Price, Utah, USA
AAI designed a
relatively steep (40 degree) backfill slope to be constructed during
reclamation of the West Ridge Mine. Key components of the slope design
include a geogrid-reinforced uncompacted plant rooting zone at the slope
face, geocomposite drains, a rockfill toe drain, compacted backfill
material, and at least 70% eventual revegetation. Mt. Nebo Scientific,
of Springville, Utah teamed with AAI and designed the revegetation plan.
AAI has represented West Ridge Resources at regulatory agency meetings.
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ASSOCIATES, INC.