The City of Detroit Water and Sewerage Department is responsible for operation of 46 combined storm sewers, most of which have an overflow outlet to the Detroit River. In 1991, the Michigan Department of Natural Resources (MDNR) identified discharge from combined sewer overflows (CSOs) as a threat to the health of the Detroit River (Stage 1, Detroit River Remedial Action Plan (RAP), 1991). CSOs can result in the discharge of floatables, sediment, nutrients, organic material, oil and grease, metals, pathogens, and other pollutants in the receiving waters. Floatables and oil and grease cause short-term degradation of aesthetics, and elevated bacteria levels may cause the closing of beaches. Such impacts are typically of short duration and are the most likely to draw public attention. Longer-term impacts are related to the loads from one or many seasons of discharge, and include reductions in dissolved oxygen, sediment contamination, and eutrophication caused by nutrients, suspended solids, and biodegradable organic matter. Effects from heavy metals contamination may include long-term toxic effects.