Sampling Purpose: The Illinois State Water Survey (ISWS) designed a project to characterize the conditions of selected backwater lakes in Illinois after the 1993 flood and to evaluate whether or not the flood affected the sediment deposition rate and pattern in the lakes. Sediment core or grab samples (also water samples) were collected from 5 backwater lakes (Swan, Stump, Meredosia - located on the Lower Illinois River; Qunicy Bay - located on the Mississippi River; Silver - located at the junction of the Mississippi and Illinois Rivers) and analyzed for particle size, metals, and herbicides. In addition, Microtox and Ceriodaphnia acute toxicity tests were conducted on the sediment (and water) samples. All sediment and water samples were analyzed at the Illinois Environmental Protection Agency-certified ISWS chemistry laboratories. Additional or split sediment samples were also analyzed at the Illinois State Geological Survey (ISGS) lab for the purpose of comparing results with previous ISGS studies on the Illinois and Mississippi Rivers. This data set pertains only to those data generated by the ISWS laboratories; see data set no. 41 for additional contaminant data generated by the ISGS. Sample coordinates were not provided with this study; however, coordinates were approximated in ArcView using detailed maps and descriptions of sampling sites.