Parametric Study of Potential Contaminant Transport at the Proposed Delmarva Power and Light Company Plant Site, Vienna, Maryland

摘要

The potential leachate transport in the groundwater under the proposed site is studied. The study is done on an idealized geologic cross-section and it involves a parametric analysis of time-varying contaminant concentrations generated by a non-linear finite element model. Variable parameters include the waste pile deposition mode, the leachate entry mode, the rate of natural recharge, the leachate density, the hydraulic conductivity of the aquifer, and the dispersivity of the aquifer materials. Parameters are selected on the basis of field and laboratory data, except for dispersivity, which is estimated on the basis of values published in the literature. The waste pile is assumed to be open to precipitation. Rainwater is assumed to become chemically saturated in passing through the waste pile. Results indicate that a waste pile situated above the water table produces less contamination than one that is in contact with the water table. No significant density effect is found within the range of parameter values investigated. Concentrations within the leachate plume are found to stabilize progressively, the stable subregion appearing first under the source and expanding gradually downstream, while the tip of the plume continues to advance indefinitely. Maximum concentrations, when the waste pile is not in contact with the water table, are found to depend primarily on the rate of natural recharge and the size of the waste pile.