CONCEPT FOR THE INTEGRATION OF WET WEATHER PROGRAMS

A substantial amount of water quality impairment is attributed to municipal wet weather sources of pollution, such as storm water, combined sewer overflows (CSOs), and sanitary sewer overflows (SSOs). These discharges contribute the same types of pollutants (e.g., suspended solids, BOD, pathogens), yet they can be extremely variable from one wet weather event to the next with respect to frequency, duration, volume and pollutant load. Indeed, wet weather discharges are intermittent, somewhat unpredictable, and not easily characterized. This unpredictability and variability makes it difficult for local environmental agencies to manage wet weather discharges. It also makes it difficult for National Pollutant Discharge Elimination System (NPDES) permitting authorities to draft permits to address wet weather discharges.Current regulatory and management approaches address these wet weather sources under at least three separate NPDES programs. Despite the fact that these programs all involve sewer pipes and other infrastructure that share capacity, infiltration, and inflow problems, the interconnectivity of municipal wet weather discharges is not considered. This may result in less progress in achieving water quality improvements than could be accomplished if these sources were considered collectively.EPA is developing a conceptual plan for an NPDES permitting framework to address storm water, CSO, SSO, and POTW (publicly owned treatment works) discharges in an integrated, comprehensive manner. EPA believes that integration across multiple wet weather programs will achieve the water quality goals of the Clean Water Act in a more efficient manner. This paper outlines an integrated wet weather NPDES permitting framework for storm water, CSO, SSO, and POTW discharges that is consistent with EPA's watershed-based permitting approach. EPA activities related to this framework will also be described.