GROUND-WATER FLOW MODELING AS A TOOL FOR THE PROSPECTOR SQUARE AND SILVER MAPLE CLAIMS TAILINGS SITES REMEDIATION STRATEGIES, PARK CITY, UTAH

The upper Silver Creek watershed, including the community of Park City, Utah, comprises a former silver mining area with a legacy of environmental problems. Initially, a series of site-specific investigations were compiled, a hierarchical analysis that characterized the hydrologic system of the watershed was performed, conceptual models for the hydrologic system were developed, and uncertainties about the hydrologic system and likelihood of possible contaminant migration pathways were identified. This subsequent site-specific study focused on two tailings sites, Prospector Square and Silver Maple Claims, which are environmentally significant to the watershed and located in the middle of the Park City community.

Four steps with significant results were then accomplished: 1) A steady-state numerical model was calibrated to show that the Park City Formation hydrologic input into the alluvial system is significant and affects the remediation process; 2) Sensitivity analysis was conducted to show variations of alluvial hydraulic conductivity for all model layers, variation of Silver Creek stream-bed conductance along the Prospector Square and Silver Maple Claims, variation of the Pace-Homer irrigation ditch-bed conductance, variation of the engineered Prospector drain pipe conductance, and variation of recharge rates for the upper model layer; 3) Potential contaminant pathways in the hydrologic system were evaluated using particle transport functions; and 4) The impact of remedial measures on the contaminant pathways was evaluated including: lining of Silver Creek in the Prospector Square area; lining of the Pace-Homer ditch; and discontinuing the engineered Prospector Square drain function. The results of this study, to be used to aid decision-makers in selecting and implementing multiple remedial actions, demonstrate the importance of evaluating engineering solutions simultaneously with a systems approach.