An application for renewal of an NPDES permit must be submitted how many days before the previous permit expires?

To maintain compliance with the National Pollutant Discharge Elimination System (NPDES) regulations, it is important to submit a renewal application for a permit well in advance of its expiration. The correct requirement dictates that an application for renewal must be submitted at least 180 days before the previous permit expires. This timeframe allows the regulatory agency sufficient time to review the application, process any necessary changes, and ensure that there is no lapse in coverage for the discharging entity, thus helping to maintain environmental protection standards.

The requirement for a 180-day submission period emphasizes the importance of planning and preparedness in environmental compliance, ensuring that facilities do not experience disruptions in their permitted activities while awaiting permit renewal. This allows for continuity in regulatory compliance and provides adequate time for consideration of any environmental impacts associated with the discharge.