Responding to a partial remand the U.S. Court of Appeals for the 9th Circuit issued in 2003, the EPA is proposing two substantial changes to its general permitting regulations for Phase II small municipal separate storm sewer systems (MS4s).
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The proposal would ensure that the permitting authority—either a state or the EPA and not the MS4—determines the adequacy of best management practices (BMPs) to reduce discharges of pollutants to the maximum extent practicable (MEP). Also under the proposal, the public would be given the opportunity to review, submit comments on, and request a public hearing on the requirements MS4s must meet.
A “municipal separate storm sewer” is a conveyance or system of conveyances (including roads with drainage systems, municipal streets, catch basins, curbs, gutters, ditches, man-made channels, or storm drains) for collecting or conveying stormwater. The EPA issued the MS4 Phase II rule in 1999 to cover MS4s that were not addressed in the 1990 Phase I rule, which covered medium and large systems and some small systems.