Risk-cost analysis in ground water contaminant transport: the role of random spatial variability and sorption kinetics

We outline a methodology for quantifying the risk (probability) to exceed e nvironmental regulation standards for ground water quality and coupling thi s risk quantification with an analysis of abatement costs for attaining an acceptable risk level. The methodology accounts for the uncertainty that re sults from random spatial variability in the subsurface, and for sorption-d esorption kinetics. Random spatial variability implies that, with a determi nistic regulating framework, the risk (probability) of exceeding given wate r quality targets may remain high even after abatement measures have been t aken. We show how this risk can be set in focus by use of a probabilistic r egulating framework, which enables better risk management, Both the environ mental risk and the associated abatement costs will depend on the actual co mbination of subsurface variability, the ground water sampling method, and sorption kinetics, through the underlying quantification of pollutant conce ntration statistics. Our results emphasize the importance of a relevant acc ount of the kinetics of the sorption-desorption process, by illustrating th at neglect, or equilibrium simplification of that process, may result in hi ghly misleading risk and abatement cost estimates.