What is the primary purpose of a stormwater outfall?

The primary purpose of a stormwater outfall is to discharge treated stormwater into a waterbody or drainage system. This function is crucial because it ensures that stormwater, which can carry various pollutants from urban and developed areas, is directed away from infrastructure and populated areas and into designated drainage systems or natural water bodies.

In many cases, before stormwater is released through the outfall, it undergoes treatment to reduce harmful pollutants, thereby protecting the quality of receiving waters and complying with environmental regulations. This process is part of broader stormwater management practices aimed at minimizing the adverse impacts of stormwater runoff on the environment.

The other options describe functions that are not the primary intent of an outfall. While guiding rainfall into drains is part of a stormwater management system, it does not specifically relate to the role of the outfall itself. Collecting and storing stormwater is related to practices like rainwater harvesting or detention basins rather than the immediate function of discharging water. Filtering pollutants, while often a part of stormwater management practices, typically occurs earlier in the management chain, before water reaches the outfall, rather than being the primary role of the outfall itself.