What is an illicit discharge?

An illicit discharge is defined as any discharge into the storm sewer system that is not composed entirely of stormwater. This definition is critical in understanding the scope of stormwater management and pollution prevention.

Stormwater systems are designed to manage and transport precipitation runoff, which is inherently clean. However, when additional substances or pollutants are introduced into the stormwater system that originate from sources such as industrial processes, improper disposal of waste, or even domestic activities, these discharges become illicit. Such occurrences can lead to significant environmental harm, including the contamination of local water bodies and disruption of aquatic ecosystems.

In contrast, treated wastewater (the option that refers to discharge of treated wastewater) is generally subject to specific regulatory standards designed to ensure its safety before being released. Likewise, rainwater collected from roofs and naturally occurring runoff do not introduce manmade pollutants and are thus part of normal hydrological processes that stormwater systems are intended to manage. Understanding what constitutes illicit discharges is essential for proper stormwater management and compliance with environmental regulations aimed at preserving water quality.