Water Environment Federation (WEF)

Alternatives for Finding Illicit Discharges to Stormwater Systems



Provisions of the National Pollutant Discharge Elimination System (NPDES) permits for stormwater discharges require that permits for municipal separate storm sewers systems (MS4s) shall include a requirement to effectively prohibit problematic non-storm water discharges into storm sewers. Emphasis is placed on the elimination of inappropriate
connections to urban storm drains. Using a watershed-based permit approach, the Rouge River National Wet Weather Demonstration Project analyzed alternative techniques for detecting and eliminating illicit discharges. Examined alternatives included inventories and sampling of point source outfalls, complaint hot line reporting, on-site disposal system (OSDS) inspections, dye testing and the use of receiving water quality sampling to prioritize investigations and measure effectiveness. The analysis considered technical, cost, and regulatory issues. It was concluded that all the examined alternatives have applicability, and that the most effective programs offer flexibility to employ a
combination of techniques in a collaborative phased approach to prioritizing and eliminating illicit discharge problems. Ultimately each watershed partner has to evaluate the various approaches and select the approach that is best suited to their specific needs and capabilities.


Municipal Separate Storm Sewer Systems, Illicit Discharge Elimination Plan, Illicit Discharge Detection, Storm Water Permit.

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