Trona Mine Dewatering
Hydro
Geo Chem evaluated dewatering alternatives for a large, underground
trona mine in Wyoming.
Hydroelectric
Pump Back Project
High
groundwater inflows were encountered during tunnel construction
through fractured granitic rocks, requiring expensive dewatering
far in excess of that anticipated during project planning.
Evaluation
and Impact of Waste Water Handling Practices at a Trona Processing
Plant
Waste
water handling practices at a trona processing plant had created
a brine plume in a fractured bedrock aquifer that discharged into
a nearby river.
Reclamation
of Acid Mine Water Contamination
A
28-mile-long shoestring alluvial aquifer contains a 7-mile-long
plume of metals and acid resulting from seepage from historical
mining operations.
Investigation
and Design Assistance, Flue Gas Desulfurization Ponds
Several
holding ponds, including a 40-acre flue gas desulfurization (FGD)
pond, had leaked into aquifers underlying a coal-fired power plant.
Simulation
of Groundwater Flow through a Tertiary Fanglomerate Aquifer
Groundwater
resources in a tertiary fanglomerate aquifer were potentially affected
by remedial groundwater pumping.
Copper
Mine and Mill Tailings Characterization and Seepage Analysis
An
assessment of the potential groundwater quality impacts of drainage
from over 2 square miles of copper mine and mill tailings was required
for permitting mine operations.
Other
Mining-Related Projects
Chromium
Waste Site Evaluation and Cleanup, Arizona WQARF Site
HGC conducted the evaluation and partial cleanup of an Arizona WQARF
site. Core-drilling, sampling, and on-site analysis were used to
determine the vertical distribution of metals. Environmental tracers
were used to evaluate the potential for further contamination migration.
Potential migration was also evaluated by simulating the movement
of hexavalent chromium through unsaturated soils beneath an unlined
disposal pit. The modeling was accomplished using an in-house code
called EVUN, which solves the Richard’s equation for unsaturated
flow. The simulations were performed to determine any potential
impacts in groundwater beneath the site and to evaluate the effectiveness
of a cover and capillary barrier on subsurface chromium transport.
We conducted column tests on sample cores from the site, determining
the optimum method to chemically reduce the heavy metals to an immobile
form. Using these results, we devised and implemented a proprietary
in-situ treatment and monitoring program. Finallly, HGC designed
and installed a vegetated cover over the site.
Simulation
of Groundwater Seepage to a Limestone Quarry, Iowa
HGC preformed numerical simulations of groundwater flow to a limestone
quarry in Iowa. Seepage rates into the quarry at various stages
of excavation were estimated. In addition, the effect on seepage
rates of removing low permeability beds at the base if the quarry
were evaluated. Predictions were also made of the effects of dewatering
on the local groundwater system. These simulations were performed
using a three-dimensional intregrated finite-difference code developed
by out staff. Results from these simulations provide management
and development guidance for ongoing operations at this quarry.
Impacts
of Mining on the Water Resources of the Pueblo of Laguna, New Mexico
HGC evaluated the potential impacts of uranium mining on the water
resources of the Pueblo of Laguna. The project area included the
San Juan Basin (about one-fifth the area of the state), although
the study focused on the southern half of the Basin. The study included
preparation of a data collection and interpretation report, design
of a water quality monitoring program, and development and calibration
of a groundwater flow model of the Basin. Much of the study was
dedicated to describing the geology and hydrology of the area, including
quantification of the important re-charge, specified flux, and constant
head boundaries. Chemical and isotopic data were also used for verification.
Construction
and calibration of a numerical model of the Basin resulted in the
identification of a fracture-controlled recharge area for the aquifer
system. Transient simulations were conducted to determine dewatering
effects from different uranium mine development scenarios.
