COMPREHENSIVE STUDY OF THE MECHANISM FOR DISPLACEMENT OF GROUNDWATER CONTAMINANTS AT THE PAGELS'S PIT AND ACME SOLVENTS SUPERFUND SITES, NORTHCENTRAL ILLINOIS

The Pagel's Pit and Acme Solvents superfund sites outside Rockford, Illinois provide well-documented cases of environmental contamination and threats to human health. Past studies of the two adjacent sites have modeled the displacement of contaminents through an aquifer in predictable directions. The calculated groundwater flow directions were derived from data (potentiometric well-levels) based on piezometers placed in locations according to Federal EPA guidelines. The guidelines tend to generalize and examine groundwater flow around superfund sites without adequate regard for hydrogeological diversity. Conventional modeling utilizing Darcy's Law may predict water movement through any medium, but it is limited to cases of non-turbulent flow. From recent fieldwork, it has become clear that there is an extensive karstic fracture network constituting the primary aquifer underlying glacial till at the two sites. Joint patterns in the Galena-Platteville Dolomite are quite consistent, with near-vertical sets of N60W dominent and N30E a bit less well developed. Caves and "sink holes" also exist along the strike of joints. This strongly suggests a relatively unpredictable, flashy movement of water through fractures and cavities in erratic fashion. Previous research, based on conformity to Darcy flow therefore provides insufficient if not fully inaccurate conclusions about important contaminant dynamics. Advanced, properly constrained models are necessary to reflect the true hydrogeologic characteristics of the area. Comprehensive computer simulations and laboratory analogue models now integrate all available data within realistic parameters. This further investigation has enabled an improved map depiction of the aquifer conditions. It is hoped that the refined information will help the U.S. and Illinois EPAs to focus proper attention on the hazards posed by theses sources of significant pollution.