When Phase II of the National Pollutant Discharge Elimination System (NPDES) went into effect in 2003, the municipal separate storm sewer systems (MS4s) it covered were supposed to have five years—the first full permit term—to develop and implement a stormwater plan. The general wisdom has been that the EPA would mainly provide guidance during that first term as the fledgling programs got going and then would shift its focus to enforcement.

For most of the MS4s who met the March 2003 deadline for permit coverage, that term is coming to an end. And, right on schedule, the EPA recently issued a compliance monitoring strategy for the NPDES program, both Phases I and II, with an emphasis on wet-weather discharges. Among other things, the strategy sets goals for Phase I and Phase II MS4 audits and inspections the EPA and the states should conduct: how many, how often, and for what reasons.

What does this mean for your Phase II program?

About 5,000 Phase II MS4s exist, so it will be necessary to prioritize them. The strategy allows EPA regions and states some leeway in determining how to do this, but it calls for “an appropriate combination of audits and inspections” within the next seven years to determine whether each program is in compliance. MS4s in priority watersheds—those contributing to a state’s 303(d) list of impaired waters, for example—will move higher up on the list. In addition, once an inspection or audit takes place, its outcome—good or bad—helps determine the frequency of future audits; MS4s with violations requiring an enforcement order will receive a follow-up within the year, and those with no violations, or only minor ones, will get a follow-up within five years. Other potential signs of trouble, such as citizen complaints, can also trigger an audit or inspection.

Phase I MS4s have slightly different criteria; there are about 1,000 Phase I MS4s nationally, covered under just 280 permits since many are co-permittees, but, being larger, they have the potential to do more harm if they’re not in compliance. Each one should be audited within the next five years, and, again, the outcome will determine the date of the next audit—one year for serious problems, or within five years for minor or no problems. Inspections will be conducted “as needed.”

It’s useful to know what constitutes an audit as opposed to an inspection. According to the EPA’s definitions, an audit evaluates all aspects of a stormwater program and looks for problems the local government has in implementing it. It covers structural and source control measures, detection and removal of illicit discharges, monitoring and control of pollutants in runoff, use and maintenance of structural and nonstructural BMPs, and various oversight measures. An inspection involves a subset of the MS4’s permit elements—either an in-depth review of a single aspect of the program or a review of a few specific elements of it—or a single site within the MS4.

This new compliance monitoring strategy isn’t just for MS4s; it also deals with “core” activities regulated under NPDES, such as discharges from publicly owned treatment plants and industrial facilities, as well as with combined sewer systems, sanitary sewer systems, animal feeding operations, and construction sites. You can find the memo that outlines the strategy for all of these online at http://www.epa.gov/compliance/resources/policies/monitoring/cwa/npdescms.pdf.

SW January/February 2008