Illicit Connection Program

Discharges from MS4s often include wastes and pollutants from non-storm water sources. Studies conducted in various cities found that nearly one-half of the water discharged from MS4s is not directly attributable to precipitation (i.e., rainfall or snowmelt) runoff. A significant portion of these dry weather flows are from illicit connections or improper discharges to the stormwater sewer system.

Illicit discharges enter the system through either direct connections (e.g., sanitary sewer pipes either mistakenly or deliberately connected to storm drains) or indirect connections (e.g., infiltration from cracked sanitary systems, spills, or hazardous substances dumped directly into a drain). The result is untreated discharges that contribute high levels of pollutants, including heavy metals, toxics, organic compounds, oil and grease, solvents, nutrients, viruses, and bacteria to receiving water bodies. Studies by the USEPA have shown these pollutant levels to be sufficiently high to degrade receiving water bodies and threaten aquatic and human health.

Effective March 10, 2003, most small MS4 operators are required to submit an NPDES stormwater discharge permit application. The permit requires the operator to implement six components. Of the six, the Illicit Connection Detection and Elimination program may be the most labor-intensive and costly. The program must include the following items:

• Stormwater sewer system map showing outfalls and receiving water bodies
• Ordinance prohibiting non-stormwater discharges to the MS4
• Plan to detect and address non-stormwater discharges into the MS4
• Education of the public about the hazards and costs of illegal discharges
• Determination of appropriate BMPs and measurable goals for the program