GROUNDWATER CONTAMINATION CAUSED BY SERENDIPITOUS EVENTS AT ELKHART, INDIANA

Unregulated disposal of industrial chemicals commonly results in groundwater contamination with the development of plumes of dissolved constituents. The extraordinary size of plumes is directly related to the geologic and hydrogeologic setting. This study sets out to describe multiple plumes of chlorinated solvents in groundwater at Elkhart, Indiana in relation to the subsurface lithology, and the geologic history of the area, as well as key factors controlling the migration of contaminants. The aim of this study is to understand rather serendipitous factors promoting the development of these plumes. The approach involved literature surveys along with the examination and interpretation of a suite of gamma-ray logs available from Indiana Geological Survey. The logs covered much of the contaminated groundwater system. Shallow subsurface deposits consist of a complex mosaic of glacial outwash and other interbedded glacial sediments. Across the study area, the gamma-ray logs indicated no distinct pattern of layering. Near-surface sites where chemical wastes were dumped connect directly to unconfined, permeable outwash deposits underlying Elkhart. The rapid infiltration of precipitation promoted active flow systems and spreading of contaminants in the groundwater. The nearby St. Joseph River creates a relatively steep topographic gradient and associated hydraulic gradient. Industrialization that began at the turn of the century, coupled with a unique outwash aquifer and inappropriate waste disposal at several sites created large-scale problems. Given the high risk for contamination, industries and members of the communities must be vigilant for future problems. The findings here will further enhance the understanding of contamination and prevent future problems in regions with similar hydrogeologic settings.