What is the minimum frequency for visual monitoring of stormwater discharges, according to EPA regulations?

The minimum frequency for visual monitoring of stormwater discharges, according to EPA regulations, is once during each rain event that produces runoff. This requirement is established to ensure that operators can detect and address any potential water quality issues promptly. Monitoring during each qualifying rain event allows for the observation of actual discharge conditions, which can vary significantly based on rainfall intensity, duration, and site-specific factors such as the presence of pollutants. By conducting monitoring in this manner, operators can identify any noticeable changes in the appearance or quality of the stormwater, such as discoloration, turbidity, or floatable materials, which may indicate a problem that needs to be addressed. This proactive approach helps in meeting regulatory compliance and protecting water resources effectively.