The U.S. Geological Survey, in cooperation with the U.S. Environmental Protection Agency and Environmental Operations, Inc., assisted in the characterization of the geology, hydrology, and water quality at a Brownfield redevelopment site in Canton, Illinois. The investigation was designed to determine if metals and organic compounds historically used in industrial operations at the site resulted in a threat to the water resources in the area. The hydraulic units of concern in the study area are the upper semiconfining unit, the sand aquifer, and the lower semiconfining unit. The upper semiconfining unit ranges from about 1 to 19 feet in thickness and is composed of silt-and clay deposits with a geometric mean vertical hydraulic conductivity of 7.1 ? 10-3 feet per day. The sand aquifer is composed of a 1 to 5.5 foot thick sand deposit and is considered the primary pathway for ground-water flow and contaminant migration from beneath the study area. The geometric mean of the horizontal hydraulic conductivity of the sand aquifer was calculated to be 1.8 feet per day. The direction of flow in the sand aquifer is to the east, south, and west, away from a ground-water ridge that underlies the center of the site. Ground-water velocity through the sand aquifer ranges from 7.3 ? 10-2 to 2.7 ? 10-1 feet per day. The lower semiconfining unit is composed of sandy silt-and-clay deposits with a geometric mean vertical hydraulic conductivity of 1.1 ? 10-3 feet per day. Volatile organic compounds were detected in ground water beneath the study area. Pesticide compounds were detected in ground water in the western part of the study area. Partial or complete degradation of some of the volatile organic and pesticide compounds is occurring in the soils and ground water beneath the study area. Concentrations of most of the metals and major cations in the ground water show some variation within the study area and may be affected by the presence of a source area, pH, oxidation-reduction potential, precipitation-dissolution reactions, and ion exchange reactions. Antimony, thallium, and 1,1-dichloroethane were detected in water samples from one well each at concentrations above their respective U.S. Environmental Protection Agency maximum contaminant levels.