What defines a major municipal separate storm sewer outfall?

A major municipal separate storm sewer outfall is defined by the size and capacity of the discharge pipe involved. Specifically, a single pipe with an inside diameter of 36 inches or more indicates a significant volume of water being channeled through it. This standard is critical for understanding the design and capacity of stormwater infrastructure, as larger pipes are indicative of the potential for substantial runoff management and associated risks such as flooding.

Larger outfalls are subject to different regulatory standards and requirements due to their capacity to impact water quality and the hydrology of the surrounding area. Such larger pipes are more likely to serve as focal points for managing stormwater, necessitating compliance with stricter environmental guidelines to mitigate pollution risks.

The other options do not meet the criteria for what constitutes a major outfall. Smaller pipes or discharges do not provide the same level of flow and therefore are less likely to be classified as major outfalls, nor do they carry the same implications for environmental compliance and regulation. Moreover, the location of pipes (private versus public property) does not inherently determine their classification as major or not; it is purely a matter of size and capacity.