Consider a gasoline floating on a groundwater table containing 3 mole percent benzene. Assume the gasoline is effectively immobile and is 10 m x 10 m in area. The near surface groundwater aquifer is approximately 20 m thick and underlain by a low permeability strata. The groundwater Darcy velocity is 50 m/year. The soil in the groundwater aquifer is 0.1% organic carbon and has a porosity of 40%. Estimate the benzene concentration versus time at drinking water well 1 km away assuming a. The release into the groundwater is via diffusion/dispersion from the bottom of the floating layer of gasoline b. The entire zone beneath the source area stays saturated (in equilibrium) with the floating gasoline pool primarily due to the rising and lowering of the water table.

Note that there is lateral and/or vertical dispersion between the source and the well.