In 2000 the Illinois Environmental Protection Agency (Illinois EPA) and the Illinois Department of Natural Resources (IDNR) cooperatively conducted an intensive survey of the Big Muddy River Basin. Stream conditions were evaluated by collection of water chemistry, sediment chemistry, instream habitat, macroinvertebrate community and fish community samples. Objectives of the Big Muddy River Basin Survey were to: (1) Determine aquatic life use support attainment in the Big Muddy River Basin and sources and factors causing or contributing to use impairment for reporting under section 305(b) of the Clean Water Act; (2) Document ambient water quality conditions and specific constituents contributing to water quality degradation; (3) Evaluate biotic integrity of the basin using fish community data and assign Biological Stream Characterization (BSC) ratings to stream segments assessed; (4) Determine biotic potential for each stream segment through assessment of available aquatic habitat; and (5) Determine the status of toxic substances in the basin by examination of surface water, sediment chemistry, and fish tissue samples.