What constitutes a measurable rain event according to the general permit?

A measurable rain event, as defined by the general permit, is important in stormwater management as it helps to determine when certain actions, such as inspections and monitoring, are required. The benchmark of 0.25 inches or more serves as a clear threshold, ensuring that only significant rain events are considered for evaluating potential runoff and erosion impacts. This measurement takes into account typical precipitation patterns and their influence on stormwater discharges.

Rain events below this threshold often do not produce enough runoff to significantly affect water quality or quantity, making 0.25 inches a practical cut-off point for regulatory purposes. By establishing this standard, the permit helps ensure that inspections and interventions are focused on conditions that are likely to have meaningful environmental implications, allowing for efficient resource allocation and effective stormwater management practices.