After stormwater reaches a storm drain, it can encounter additional pollutants - illicit discharges - intentionally or accidentally introduced directly into the drain. Municipal storm sewer systems are not designed to handle these wastes. Illicit discharges can include sanitary wastewater systems illegally connected to the storm drain system; effluent from septic tanks; car wash, laundry, and other industrial wastewaters; auto and household toxics such as used motor oil and pesticides that are dumped illegally; and spills from roadways. These discharges contribute high levels of heavy metals, toxic substances, oil and grease, nutrients, viruses, and bacteria to our creeks and lakes.

Water pollution threatens the drinking water supply, but it also affects recreation. Illicit wastewater discharges and pet waste can introduce viruses, bacteria, and other disease - causing agents and create a health threat for swimmers.