Modeling contaminant propagation in a fractured and karstic aquifer

Modeling flow and transport of pollutants in fractured and karstic aquifers remains an open issue. In fact, a completely adequate model for them has not been developed. These aquifers are highly vulnerable to groundwater contamination. Karst conduit system permits a rapid transport of pollutants, often under turbulent conditions and traveling long distances. Moreover, the cavities filled by residual dissolution products delay the propagation of contamination principally by means of sorption processes. The classical equivalent porous model paradigm does not permit to take into account the discrete nature of these aquifers. In this context, the reconstruction of a detailed geological model is very important in order to extend the knowledge on fluid flow and solute transport phenomena. This permits, consequently, to choose a plausible conceptual model with state variables and boundary conditions more adequate than the classical equivalent porous approach. The present work studies the area of an ex Gasometer heavily contaminated by hydrocarbons. In this area, a pump & treat system has been designed approximating the nature of aquifer to a homogeneous isotropic porous medium. The work focuses on the importance of the realization of a detailed geological reconstruction to be implemented in a flow and transport model in order to interpret the dynamics of the flow field and the transport of contamination. The obtained results have proven to be coherent with previous studies in that they show that the flow field and the transport of contaminants depend primarily on karst network architecture. © by PSP.