Using WiscLEACH to Estimate Groundwater Impacts from Fly Ash Stabilized Layers in Roadways

This paper presents a modeling study to evaluate the impacts of leaching on groundwater from fly ash stabilized layers in roadways. The computer program, WiscLEACH, based on two analytical solutions for the advection-dispersion-reaction process in the subsurface was used. The analytical method was compared to predictions made with IWEM roadway module, which was developed for assessing the potential for groundwater impacts caused by leaching from industrial material resources used as pavement materials in roadway construction. Predictions made with WiscLEACH and IWEM were compared to field data from a highway test section where the subgrade was stabilized with coal fly ash. Comparison with the field data showed that 90th percentile exposure level predicted by IWEM and concentrations predicted by WiscLEACH at a monitoring well were higher than measured data, which suggests that the predictions are conservative. Factors related to lower predicted concentrations of IWEM than WiscLEACH were discussed.