Knowledge Bank

This study investigated multiple plumes of chlorinated solvents in groundwater at Elkhart, Indiana in relation to the subsurface lithology, the geologic history of the area, and key factors controlling the migration of contaminants. The aim of this study was to understand seminal events promoting the development of these extensive contamination plumes within the study region. This was done through the analysis of literature surveys along with the examination and interpretation of a collection of gamma-ray logs available from Indiana Geological Survey. The logs covered much of the area affected by the variety of large contaminant plumes. The shallow geology proved to be a complex mosaic of glacial outwash and other interbedded glacial deposits. Across the study area, little to no distinct pattern of layering was indicated by the gamma-ray logs. The unconfined, permeable aquifer beneath Elkhart connected the near-surface chemical disposal sites and promoted the rapid infiltration of precipitation and the growth of contaminant plumes in the groundwater. The St. Joseph River close in proximity to the disposal sites contributed a steep hydraulic gradient, which propagated this rapid expansion. The porous, permeable, and varied subsurface setting, coupled with the previous lack in disposal regulations advanced the development of significant contaminant plumes. The most seriously contaminated sites are currently being remediated.