Field data show disparities between organic solute concentration in the aquifer and that in monitoring wells; an order of magnitude disparity has been recorded in some cases. Therefore, it is important to be able to relate concentrations between the two media for design of remediation systems. More significantly, to assess the impact of the leachate from a landfill on a downgradient drinking water well, it is important to correlate aquifer concentration with that in a drinking water well such that the true risk is not overly estimated. A three-dimensional finite difference flow and transport model applied to demonstrate the disparity between aquifer and well concentrations is indeed well founded and can be quantified. The modeling shows that the concentration in the well is a function of the initial vertical concentration profile in the aquifer, the amount of flux from below the partially penetrated well, the degree of penetration, the soil lithology, and the amount of purged water before sampling. Based on these parameters, an approximate analytical solution is developed that agrees well with numerical solutions.