Solute Transport Modeling for the Preliminary Design of Shallow Aquifer Restoration Scenarios at the Grand Junction, Colorado UMTRA Project Site

Abstract

A widely accepted two-dimensional solute transport groundwater model was used to predict the effect of selected aquifer restoration methods on the concentration and distribution of dissolved uranium ions in a shallow alluvial aquifer in Grand Junction, Colorado. Transient flow was modeled for relatively complex simulations including (1) the use of a bentonite slurry wall around the perimeter of the contaminated soil and aquifer, (2) a dewatering trench downgradient of the contaminant source, and, (3) a major river adjacent to the contaminant source and slurry wall. Results indicated that either a well or trench system would accelerate the removal of uranium ions from the shallow aquifer. As a result, restoration of the alluvial aquifer was considered technically feasible, and preliminary designs for the selected restoration systems were made. Costs for construction and operation over a ten-year period were estimated to be between 600,000 and 3,000,000 (1987 U.S. dollars) depending upon if and/or how the contaminated water is treated after removal from the aquifer.