Only stormwater is allowed in the City of Columbia storm sewer system. An illicit discharge is defined as any discharge to the municipal separate storm sewer system that is not composed entirely of stormwater, except for discharges allowed under a National Pollutant Discharge Elimination System (NPDES) permit.

 

    Non-stormwater discharges to the storm sewer system occur most often through illegal connections to the storm sewer system, aging sanitary sewer lines running through the storm sewer system, or through illegal dumping activities. Because of these discharges, contaminated stormwater enters into storm drains or directly into local waters and therefore never receives treatment from a wastewater treatment plant. Illicit connections may be intentional or may be unknown to the business or homeowner.