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Developing Spatial Environmental Models for Risk-Based Decision MakingBy Julie Kim, M.S.E., Lesley Hay Wilson, M.S.E., and David R. Maidment ABSTRACT Models developed in a Geographic Information System framework serve as useful analytical tools for assessing environmental risk and making corrective action decisions. In this research, three site-specific models were developed for a petroleum facility in Marcus Hook, Pennsylvania, to better understand subsurface conditions, groundwater movement and its groundwater interaction with surface water. The first model is a contour map-based model that uses a procedure developed to analyze potential sources and source areas by overlaying maps of quantitative measurements of chemicals of concern with spatial features consisting of qualitative historical descriptions of environmental conditions. Despite limited underground pipeline information, the model identified the central region as a potential source area with various potential chemical sources. The second model is a conservative screening-level groundwater/ surface water interaction model that calculates a target groundwater level for each chemical of concern, so that its predicted surface water concentration meets state surface water quality standards. Benzene was the only chemical above its target groundwater concentration by a factor of forty. Since the interaction model depends on the accuracy of the groundwater flow model, the target level for each chemical changes for different groundwater flow values. The third model is a comprehensive groundwater flow model that uses the subsurface description developed in ArcView, GMS, and MODFLOW. Two groundwater models were created based on different complexities, assumptions, and inputs. Both incorporated important subsurface features previously not included in the original model. The new models provided a more probable groundwater flow distribution than originally estimated; about 75% of groundwater flows into the minor tributary in the case study site, while the remainder flows to the major tributary. The highlighted links that follow are connected to Adobe pdf files of the corresponding material. To view them you must have the Adobe Acrobat Reader 3.0. View the Report...(2.4MB)
These materials may be used for study, research, and education, but please credit the authors and the Center for Research in Water Resources, The University of Texas at Austin. All commercial rights reserved. Copyright 1997 Center for Research in Water Resources.
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