A rapid screening-level method to optimize location of infiltration ponds |
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| Authors: | Fennemore G G Davis A Goss L Warrick A W |
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| Institution: | Geomega, 2995 Baseline RD., Ste. 202, Boulder, CO 80303, USA. george@geomega.com |
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| Abstract: | A rapid-screening technique was developed to identify lithologies that best disperse artificial recharge via surface infiltration and minimize effects on ground water chemistry. The technique prospectively evaluates basin infiltration rates and water chemistry influences by integrating geotechnical, hydraulic, and water quality data with column test data and numerical modeling. The technique was validated using field data collected from surface infiltration basins designed to recharge ground water pumped from the Pipeline pit gold mine in Nevada. Observed recharge rates at these infiltration sites correlated most significantly with depth to groundwater, with basins in coarse-grained lithologies performing better (0.45 to 0.85 m/day) than those with fine-grained layers (< 0.30 m/day). Observed water quality resulting from leaching of the previously unsaturated vadose zone showed a transitory (< six months) increase in solute concentrations followed by a decrease to baseline conditions, a phenomenon also observed in column tests that leached native soils with local ground water. Leaching of fine-grained soils with evaporites resulted in greater solute concentrations (TDS > 2000 mg/L) than coarse-grained soils (< 1200 mg/L). The results of HYDRUS_2D simulations using the accumulated data as input were in agreement with observed ground water chemistry downgradient of the infiltration basins for a variety of lithologies. Sites for infiltration basins can be rapidly screened to include areas with greatest depth to groundwater and in coarsest alluvial sediments, and impact to ground water chemistry can be reliably predicted using computer modeling and column test results. |
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