The calibrated model simulations indicate that young, potentially contaminated water in the unconfined aquifer can move downward into the confined aquifers of the ground-water system where public-supply wells are screened. Water chemistry results and results of ground-water transport age and tracer simulations indicate that wells screened through multiple aquifers can introduce flow through the well bores, thus providing a rapid path from the unconfined aquifer to the upper confined aquifer. Simulations indicate that CFC-11 concentrations in the upper confined aquifer originate at wells screened through multiple aquifers and are drawn toward other pumping wells. This mechanism for movement of younger water with concentrations of CFC-11 through the well bores of wells screened through multiple aquifers is thought to be the primary process accounting for the presence of contaminants in the confined aquifers and is consistent with independent geochemical data.