Center for Research in Water Resources
This module describes project efforts to implement map-based modeling for the development of site conceptual models. The site conceptual model approach includes integrating ArcView and Access to store and analyze data related to sources, transport mechanisms and exposure pathways. In addition resources are included that describe the development of exposure scenarios and an exercise that documents the use of Microsoft Excel to prepare a site conceptual model.
Figure 1. Environmental Risk Assessment Data Model
The site conceptual model is an important framework for the Environmental Risk Assessment Data Model illustrated in Figure 1. The process of identifying the sources, transport mechanism and receptors is fundamental to understanding the situation being studied and therefore for the analysis of sources of chemicals of concern in the environment. The potential for exposure must be evaluated for all credible exposure pathways from sources to human or ecological receptors. The site conceptual model is a method to characterize the situation being studied and a means to communicate that understanding. The Environmental Risk Assessment Data Model is discussed further in the Introduction to this CD.
The exposure pathways are developed for individual sources and chemicals of concern. The pathways are necessarily chemical-specific. The site conceptual model includes data about the representative concentrations of chemicals of concern at sources, the spatial location of the source and the environmental media that define the source area (i.e., the area of highest concentrations). Generally the source can be defined by as point coverages. These coverages may include individual points for releases (e.g., the location of an emissions stack) or the center point of a source area (e.g., the center of a defined area of soils containing chemicals of concern). The environmental representation of the site (e.g, geologic cross-sections, digital terrain models, and meteorological data) is important to the understanding of the transport of chemicals in the environment. The locations of receptors may also be defined by points (e.g., the location of a drinking water well) or areas (e.g., the residential neighborhood near a facility). These points and areas are stored within the GIS data layers for the site conceptual model.
EPA's National Center for Environmental Assessment
Lesley Hay Wilson
Center for Research in Water Resources
The University of Texas at Austin
Austin, TX 78712
E-mail: hay_wilson@mail.utexas.edu
