UC Santa Barbara

The U.S. Geological Survey's two-dimensional solute-transport and dispersion model (the method of characteristics, or MOC, model) accurately reproduces the chloride-concentration distribution observed in a buried-valley aquifer contaminated by a solid-waste landfill in Butler County, Ohio. The predictive capacity of the calibrated model has utility in water resources planning in regions of ground-water discharge downgradient of the landfill. Calibration of the ground-water-flow model to an observed steady-state head field indicates a ratio of hydraulic conductivity to diffuse recharge of 8.8 × 10-4. Mass transport calibration was achieved with a longitudinal dispersivity of 53 m, a transverse dispersivity of 5.3 m, and a chloride concentration of 320 ppm at injection wells used in simulating the contaminant source. The model was calibrated to a contaminant distribution observed 16.7 years after initial landfill operations; 10 and 50 year contaminant-distribution predictions indicate that the plume will reach a steady-state equilibrium with the ambient ground-water flow system after 10 years. The attainment of such a condition could significantly decrease the possibility of future contamination of downgradient domestic supply wells.