Illicit discharges are those wastes and wastewaters from non-stormwater sources which cannot legally be discharged down storm drains to a Municipal Separate Storm Sewer System (MS4). Sources include:
The result of illicit discharges entering the storm drain is untreated discharges to receiving water, contributing high levels of pollutants including heavy metals, toxics, oil and grease, solvents, nutrients, viruses, and bacteria. Pollutant levels from these illicit discharges have been shown in EPA studies to be high enough to significantly degrade receiving water quality and threaten aquatic, wildlife and human health.
This fact sheet provides guidance on identification of potential illicit stormwater discharges and techniques to reduce the risk of illicit discharges.
Reduction of illicit discharges results in minimization of the discharge of pollutants down storm drains or water conduits and, ultimately to downstream lakes, streams and wetlands. Reducing discharge of pollutants improves water clarity, coloration and odor, as well as fish and wildlife habitat.
Programs designed to identify illicit discharges and reduce the risk of such discharges are dependant upon several factors including the MS4’s available resources, size of staff, and degree and character of its illicit discharges. Ultimately, effective source control is dependent upon applying a mixture of education, incentives and regulation.
The Center for Watershed Protection identifies some strategies for education and incentives: passive education, active training, provision of direct MS4 services, subsidies and discounts, home/business-owner recognition programs, stewardship group formation. Regulations might include: adoption of a local ordinance, notifications/signs /hotlines, restrictions or bans, enforcement, utility pricing. An effective program applies some combination of the above strategies, many of which are discussed below. For greater detail, see the Additional Resources section.
Awareness campaigns inform public employees, businesses, property owners, and elected officials of the ways to detect and eliminate illicit discharges and the hazards associated with illegal discharges and improper disposal of waste. Illicit discharge education actions may include programs to promote, publicize and facilitate public reporting of illicit connections or discharges, distribution of outreach materials and storm drain stenciling. Suggested educational methods include:
A program to detect and address illicit discharges is central to the ultimate elimination of illicit discharges. EPA recommends that the program include the following four components:
Initiate recycling programs for commonly dumped wastes, such as motor oil, antifreeze and pesticides. Provide sufficient public notification of any newly established programs or increase public awareness of existing programs. For more detailed information on ways to keep yard debris out of the street, see the Residential Waste Collection & Clean-up Programs fact sheet.
Recycling collection services may be provided in a recycling program (see Recycling Program above), but are not necessary if the public is properly notified of recycling drop-off locations and materials accepted. For maintenance associated with storm drain stenciling, see the Storm Drain Stenciling fact sheet.
The cost of detecting and reducing the risk of illicit discharges will vary depending on the intensity of the effort and the approach(es) chosen. Costs attributable to detection and correction of illicit discharges are based on the total staff involvement driven by the problem area identification methods employed and the number and extent of discharge incidences. Public education program costs are determined by the type of materials produced and the method of distribution selected. Volunteer efforts can reduce program costs, as determined by staff hours required for program implementation and leadership of volunteers. An important consideration is that prevention of illicit discharges is much less costly than detection and subsequent correction.