INTRODUCTION OF CONTAMINATED GROUND WATER AND SEDIMENT :
The interaction between surface water and ground water bodies traditionally has been idealized as a simple unidirectional transport process. More recent detailed examination has shown that flow systems can be complicated. Complicated flow and mixing patterns can have significant implications for physical, biogeochemical, and biological processes within the system and for contaminant transport. Ultimately, the effects of these complex processes on the risk to human health and the environment must be assessed.
This panel examined the technical complexities of surface water and ground water interaction on a spatial and temporal scale. The regulatory framework of mixing zones was reviewed, and the policy implications of mixing zones on ground water and surface water interaction were discussed. The panel focused on mathematical modeling of these processes and reviewed the state-of-the-art technology in aqueous mixing simulation models. Advantages and disadvantages of different modeling approaches, time and spatial resolution disparities, and aggregationñdisaggregation of data were also discussed.CONTAMINATED GROUND WATER AND SEDIMENT
The U.S. Environmental Protection Agency (USEPA, 1998b) considers the primary exchange processes between the sediment and the overlying surface water to occur within the upper 2 in. of sediment deposits. Important elements in estimating the ground water contribution are distinguishing and characterizing the various inputs to the surface
waterñsediment system, which, in some cases, can be contaminated sediment. The specific role of modeling in managing contaminated sediments is reviewed in Chapter 2.CONTAMINATED GROUND WATER AND SEDIMENT
Until recently, methods for quantifying the local extent and quality of contaminated ground water discharges and their pollutant load to surface waters consisted primarily of hydrologic and physicochemical techniques (USEPA, 1998a). Promising new research is focusing on the use of biological indicators (organisms that spend all or part of their life cycle in contact with ground water) to characterize zones of ground waterñsurface water interaction, reviewed later in this chapter.CONTAMINATED GROUND WATER AND SEDIMENT