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 environmental regulation standards for ground water quality and coupling this risk quantification with an analysis of abatement costs for attaining an acceptable risk level. The methodology accounts for the uncertainty that results from random spatial variability in the subsurface, and for sorption-desorption kinetics. Random spatial variability implies that, with a deterministic regulating framework, the risk (probability) of exceeding given water quality targets may remain high even after abatement measures have been taken. We show how this risk can be set in focus by use of a probabilistic regulating framework, which enables better risk management, Both the environmental risk and the associated abatement costs will depend on the actual combination of subsurface variability, the ground water sampling method, and sorption kinetics, through the underlying quantification of pollutant concentration statistics. Our results emphasize the importance of a relevant account of the kinetics of the sorption-desorption process, by illustrating that neglect, or equilibrium simplification of that process, may result in highly misleading risk and abatement cost estimates.