Thursday, December 4, 2008

Incorporating Stormwater into TMDL – Recent EPA Guidance

Stormwater discharges can contribute to the impairments to lakes and rivers. Once a waterbody is listed as impaired (i.e., identified in State 304(d) list), States are required to develop a Total Maximum Daily Load analysis (“TDML study”) to determine the maximum load of the pollutant to the waterbody which will still result in the water body meeting it water quality standards. Nonpoint pollution sources, such as stormwater discharges, are one element of this analysis. The point sources, which are primarily NPDES permitted discharges of wastewater are the second element of this analysis.

Stormwater sources which are regulated under NPDES permits require special consideration. Although generally considered part of the nonpoint pollution source category, they are also subject to the requirements of an NPDES permit.

On November 17, 2008, US EPA made available a DRAFT guidance document “TMDLs to Stormwater Permits”. EPA developed this handbook to address challenges that are unique to TMDL development and implementation involving permitted stormwater discharges from municipal separate storm sewer systems (MS4s), industrial facilities, and construction activities. The 211-page handbook is intended for federal and state TMDL writers and NPDES stormwater permit writers responsible for addressing waterbodies impaired by discharges from stormwater sources.

The draft handbook provides:

  • General regulatory information on stormwater NPDES permits and TMDLs
  • Discussion of opportunities to coordinate TMDLs and stormwater permits
  • Guidance on evaluating stormwater contributions to impairments
  • Guidance on development of TMDLs with significant stormwater sources
  • Guidance on implementing coordinated TDML and stormwater permit programs

The handbook also includes excerpts from regulatory programs from ten different States that relate to the coordination between TMDL and stormwater permitting programs.

The draft handbook was released for public review and comments. Interested parties can submit comments on the handbook until February 17, 2009.

For further information contact Caltha LLP at
Caltha LLP Website

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