On November 26, the U.S. Environmental Protection Agency (EPA) issued a new memorandum updating aspects of its November 2002 memorandum on the subject of “Establishing Total Maximum Daily Load (TMDL) Wasteload Allocations (WLAs) for Storm Water Sources and NPDES Permit Requirements Based on Those WLAs.” Perhaps most significantly, language regarding the use of flow as a surrogate has been removed. This may be in reaction to several recent court cases, including the Federal court ruling in Virginia Department of Transportation v. EPA where the court decided that EPA exceeded its authority in establishing a flow-based TMDL for Accotink Creek in Fairfax, Va. The flow-based TMDL used stormwater runoff as a surrogate for sediment loading in the stream. While this approach has been used in EPA Region 1, it was challenged in Region 3 and 7.
As a background, in Nov. 2010, EPA issued a memorandum updating and revising elements of the 2002 memorandum to better reflect current practices and trends in permits and WLAs for stormwater discharges. In March 2011, EPA sought public comment on the 2010 memorandum and, earlier this year, completed a nationwide review of current practices used in municipal separate storm sewer system (MS4) permits as well as industrial and construction stormwater discharge permits.
EPA seems to have taken heed of public comments, including those from the Water Environment Federation, which asked for specific examples on how to include water quality-based effluent limits (WQBELs) and WLAs in permits. The agency refers to the recently released MS4 compendium, which highlights examples of WLA integration into MS4 permits from across the country. Additionally, EPA greatly clarifies the application of WQBELs in MS4 permits. The memorandum now states that WQBELs can be expressed as “system-wide requirements rather than individual discharge location requirements such as effluent limitations on discharges from individual outfalls.”
As a result of comments received and informed by reviews of EPA and state-issued stormwater permits, the agency is updating aspects of the 2002 memorandum by including “clear, specific, and measurable permit requirements,” and, where feasible, adding numeric effluent limits to National Pollutant Discharge Elimination System permits for stormwater discharges. Further, the agency recommends disaggregating stormwater sources in a WLA to allow for integration into permits.