ABSTRACT
With the twentieth anniversary of 'Earth Day' receiving much notoriety, many in the media took the opportunity to look back at the emphases placed on different aspects of 'our environment' over the past two decades. Following passage of the National Environmental Policy Act, early emphasis was placed on cleaning up the nation's air and surface water resources. Two basic elements affecting the transport and fate of contaminants in the subsurface are properties of the subsurface materials or the subsurface environment and physicochemical and biological properties of the contaminant. Hydrodynamic processes affect contaminant transport by impacting the flow of ground water (in terms of quantity of flow and flow paths followed) in the subsurface. The hydrodynamic process of dispersion (spreading of the contaminant about the mean ground water velocity) is attributed to the distribution of flow paths for the subsurface system and the diffusion of the contaminant.
