DEFINITION OF AN ILLICIT DISCHARGE The term “illicit discharge” is defined in the State’s Phase II Stormwater Quality Regulations as “any discharge to a municipal separate storm sewer (MS4) that is not composed entirely of stormwater, except discharges pursuant to the Colorado Discharge Permit System (CDPS) permit, and discharges resulting from fire-fighting activities.” Discharges from MS4s to a waterway can often include wastes and wastewater from non-stormwater sources. Illicit discharges can enter the MS4 through either direct connections (e.g., sanitary wastewater piping either mistakenly or deliberately connected to the storm drains) or indirect connections (e.g., infiltration into the MS4 from cracked sanitary systems, spills collected by storm drainage in street, inlets, and drain outlets, or paint or used oil dumped directly into a drain or into street inlets). The result is untreated discharges that contribute high levels of pollutants, including heavy metals, toxics, oil and grease, solvents, nutrients, viruses, and bacteria to waters of the state. Pollutant levels from these illicit discharges have been shown in EPA studies to be high enough to significantly degrade waterways and threaten aquatic, wildlife, and human health. PROHIBITED MS4 DISCHARGES
The following are considered to be illicit (illegal) discharges to the MS4 (this list is not considered all inclusive):
Sanitary wastewater sources such as:
Sanitary wastewater (usually untreated) from improper sewerage connections, exfiltration or leakage;
Effluent from improperly operating or improperly designed septic tanks; and
Overflows of sanitary sewerage systems.
Automobile maintenance and operation sources such as:
Commercial car wash wastewaters;
Radiator flushing wastewaters;
Engine degreasing wastes;
Improper oil, gasoline, and other automotive fluids disposal;
Leaky underground storage tanks; and
Leaking of oils, gasoline and other automotive fluids from automobiles.
In some cases, the above discharges may be allowed if properly treated to remove the pollutants prior to discharge into the stormwater system - such as utilizing a commercial oil/water separator that is routinely maintained). Landscape irrigation sources such as:
Direct spraying of fertilizers, pesticides or herbicides onto impervious surfaces; and
Over-application of fertilizers, pesticides or herbicides onto landscaping.
Other sources such as:
Non-contact cooling waters;
Metal plating baths;
Dewatering of construction sites;
Washing of concrete ready-mix trucks;
Contaminated sump pump discharges;
Improper disposal of household toxic wastes;
Spills from roadway and other accidents;
Chemicals, hazardous materials, garbage, and sanitary sludge landfills and disposal sites;
Commercial use of soaps and detergents; use in cleaning pavement, vehicles and equipment;
Sediment from lack of or improper maintenance of erosion and sedimentation controls;
Latex/oil-based paints & solvents;
Improper disposal of restaurant grease; and
Trash and debris: littering and dumping, household or construction waste.
ALLOWABLE DISCHARGESThe general rule is that ONLY STORMWATERis allowed in our storm sewer system; however, the State has recognized a few exceptions, as follows:
Allowable non-stormwater discharges (Exceptions to the “Only Stormwater” rule)
Diverted stream flows;
Rising groundwater, uncontaminated groundwater infiltration to separated strom sewers (as defined at 40 CFR 35.2005(20)), and uncontaminated pumped groundwater;
Discharges from potable water sources, foundation drains, air conditioning condensation, irrigation water, springs, water from crawl space pumps, footing drains, lawn watering, and individual residential car washing activities; and
Flows from riparian habitats and wetlands.
Allowable non-stormwater dishcarges that must comply with jurisdictional standards: Super-chlorinated water from water line flushing, etc.
Southeast Metro Stormwater Authority (SEMSWA) including Centennial, Inverness WSD, and East Cherry Creek Valley WSD.Arapahoe County.Littleton.Glendale.Greenwood Village.Cherry Hills Village.Columbine Valley.Arapahoe County Water and Wastewater Authority (ACWWA).E-470 Authority.Goldsmith Metro District.Colorado Department of Transportation