EPA Memo Clarifies "Phased TMDL" Terminology

Benita Best-Wong, Director of EPA's Assessment and Watershed Protection Division, has issued a memo clarifying the Guidance for Water Quality-Based Decisions: The TMDL Process, issued in 1991. She explains EPA's interpretation of the term "phased TMDL" as used in EPA guidance, and the distinction between "phased TMDLs," "staged implementation," and "adaptive implementation".

WASHINGTON, DC, Aug. 11, 2006 -- Benita Best-Wong, Director of EPA's Assessment and Watershed Protection Division, has issued a memo clarifying the Guidance for Water Quality-Based Decisions: The TMDL Process, issued in 1991.

She explains EPA's interpretation of the term "phased TMDL" as used in EPA guidance, and the distinction between "phased TMDLs," "staged implementation," and "adaptive implementation".

Phased TMDLs are a matter of TMDL development while staged implementation and adaptive implementation are post-development implementation concepts. Greater attention to these distinctions has emerged since EPA issued the 1991 Guidance and promulgated the Water Quality Guidance for the Great Lakes system in 1995, thus warranting the additional clarification, she wrote.

"Current EPA guidance for developing TMDLs speaks of a 'phased approach to developing TMDLs,' frequently referred to as 'phased TMDLs'. This concept has sometimes been misinterpreted and resulted in TMDLs that are not calculated to meet applicable water quality standards." Best-Wong wrote. "This misinterpretation is not consistent with EPA's interpretation of 40 CFR Part 130.7. The regulations require all TMDLs to be calculated to achieve applicable water quality standards."

The complete memorandum has been posted on the EPA's website at: http://www.epa.gov/owow/tmdl/tmdl_clarification_letter.html.

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