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On Dec. 21, EPA issued a draft policy, NPDES Requirements for Municipal Wastewater Treatment During Wet Weather Flows, to clarify both existing rules and the flexibility that permit writers have when addressing peak flows in wastewater treatment facilities.
The draft policy reflects earlier EPA statements about proper implementation of the bypass and secondary treatment regulations and focuses on three areas of concern:
* emergency overflow structures,
* peak excess flow treatment facilities (PEFTFs), and
* blending/recombining peak flows.
For the most part, the draft policy accurately reflects EPA's past practices in addressing emergency discharges and blending of peak wet weather flows at wastewater treatment facilities. However, with respect to PEFTF permitting, the draft policy interprets the secondary treatment rule more restrictively, which probably will limit municipalities' ability to use satellite treatment systems. Such a limit could be costly for communities where transporting wet weather flows to downstream facilities is infeasible or impractical.
What the Draft Policy Says
Emergency overflow structures. For decades, collection system designs have included emergency outfalls to prevent wastewater backup into homes and protest critical system components, such as pump stations. The draft policy states that National Pollutant Discharge Elimination System (NPDES) rules require communities to identify all outfalls that discharge to surface waters...