Center for Research in Water Resources
This CD-ROM is an updated version of the first GIS Enviro98 CD. The 1999 version is intended to illuminate the utilization of GIS in Environmental Risk Assessment, as developed in the research and teaching programs of the Environmental and Water Resources Engineering program of the University of Texas at Austin. These activities include a graduate course on environmental risk assessment which I presented jointly with Dr Richard L. Corsi during the Spring Semester, 1998. Also included are results of a research project on the use of GIS in environmental risk assessment for a refinery formerly owned by BP Exploration & Oil Inc. This research effort is led by Lesley Hay Wilson and has been supported by Andrew Romanek and Julie Kim. It is due mainly to efforts of Julie and Lesley that this CD has been assembled. The structure of this CD-ROM is similar to that used in a parallel CD-ROM series relating GIS to Hydrology for which three CD's have been prepared, GIS Hydro '97, GIS Hydro '98 and GIS Hydro '99. We also wish to record our appreciation to Jennifer Benaman of Quantitative Environmental Analysis, Montvale, NJ, who has contributed material on the linkage of GIS and water quality modeling in the Water Quality module of GIS Enviro99.
What is Environmental Risk Assessment?
The goal of Environmental Risk Assessment is to protect human health
and the environment by limiting the risks posed by chemical releases and
other waste discharges to the environment. The process of environmental
risk assessment involves identifying potential sources of chemicals to
the environment, the pathways by which they can be transported to a point
of exposure, and the potential human or ecological receptors which might
be impacted at that location. The combination of all of these elements
is known as an environmental exposure pathway. These pathways can
be divided into cross media segments, e.g., transfer of chemicals
between soil and groundwater and geographic components, e.g., transport
of chemical from one location to another within groundwater flow. The receptors
can be either human or ecological and are identified as those individuals
or systems near and surrounding the sources that could potentially be affected
by the release. Understanding all of the potential exposure pathways is
fundamental to the development of site
conceptual models for environmental risk assessment.
Figure 1. Environmental Risk Assessment Data Model
Figure 1 also illustrates the fundamental relationship between the concentration at the source and the concentration at the location of the point of exposure. The ratio of the source concentration to the exposure concentration is referred to as the Attenuation Factor. While this factor is conceptually easy to define, in practice it often requires a significant computational effort.
The concept of employing risk assessment in environmental management is rooted in the idea that instead of imposing uniform concentration-based limits on sources, these sources should be individually assessed, so as to ascertain whether the source constitutes a significant environmental risk. This paradigm shift from fixed concentration limits to risk-based limits recognizes that it is not possible to maintain the earth in a pristine state and that resources for pollution control need to be invested in such a way as to minimize the overall risk to human health and the environment. This risk-based approach to decision making results in a call on GIS as a supporting technology because quantifying risks to human health and the environment means being able to describe the linkages between sources of releases and the populations they impact. Risk assessment and decision making thus have a strong spatial component, which GIS is well-suited to address. GIS Enviro99 shows some aspects of how environmental risk assessment can be approached from a GIS-based perspective.
Site vs. Regional Environmental Risk Assessment
A fairly important distinction exists between a site environmental risk assessment performed for a particular property, such as an industrial facility which contains soils and groundwater impacted by chemicals of concern, or has stacks that are sources of chemicals of concern to the atmosphere, and a regional environmental risk assessment, such as might be performed by a regulatory agency or a city government concerned about the overall impact of all potential sources of chemicals of concern on the health of the citizens and the environment in a region. Regional risk assessment can also be focused on a particular body of water, such as the Corpus Christi Bay system, where we have recently completed a project on total loadings and expected concentration levels in the water body. The main focus of this CD is on site level risk assessment.
The work presented on this CD represents the combined efforts of many individuals. In addition to the people mentioned above, I would like to thank the Environmental Remediation Management section of British Petroleum for their support of our research program in this area and in particular, Susan Sharp of BP Amoco and Jim Rocco of Sage Risk Solutions LLC for their tremendous contributions to the case study of the Marcus Hook refinery. Participating in this case study has contributed significantly to our understanding of how GIS can be used in Environmental Risk Assessment. An integral part of the BP research is a project led by Dr. Robert Gilbert and Lizan Koerner of the geotechnical engineering program here at UT. Bob and Lizan are developing a Decision Framework for the corrective action program at the former BP facility. As a basis for that work they have developed a relational database for the site conceptual model.
Student projects from the Environmental Risk Assessment class and from the GIS in Water Resources class are presented here as example applications to support the overall process. We thank them for their contributions to this work. The students are: Sarah Benedict, Chun-Yi Chiang, Aubrey Dugger, Cindy How, Brad Hudgens, Aiza Jose, Julie Kim, Michael Landrum, Sarah Lindsay, Kris Martinez, Patrice Melancon, Shiva Niazi, Carolyn Nobel, Christine Otto, Matt Russell, Michelle Simpson, and Scot Weaver.
We hope you find the materials on this CD helpful in your work and for self-study. If you have questions about particular modules, please direct them to the individual identified in the module, or send general questions to me at the address given below.
David R. Maidment
Ashley H. Priddy Centennial Professor of Engineering
Director, Center for Research
in Water Resources
The University of Texas at Austin
maidment@mail.utexas.edu
http://www.ce.utexas.edu/prof/maidment
