Hydrogeological Characterization of Contaminated Glacial Sediments in South Central Wisconsin
Unconsolidated sediments often overlie significant bedrock aquifers within North America and are important to characterize for groundwater and contaminant studies. However, the dynamic nature of ice margins results in heterogeneous sediments that are difficult to characterize geologically and hydraulically. In this study, a detailed investigation of the unconsolidated sediment was completed to determine how best to characterize the hydrogeology by integrating multiple independent and high-resolution data sets including: stratigraphic logs, grain size analysis, surface geophysics, hydraulic head profiles, and volatile organic compound concentrations. The unconsolidated sediments were found to be highly heterogeneous geologically but with low vertical hydraulic contrasts. Where found, vertical hydraulic contrasts were typically a result of four geologic features: top of rock, sand-diamict contact, interbedded diamict, and mud beds. High contaminant concentrations are consistent with hydraulic contrasts indicated by the geology and hydraulic testing. Detailed contaminant profiles also help identify subtle geologic heterogeneities important for contaminant migration.