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To: Members & Subscribers
From:National Office
Date:August 6, 1997
Re:RA 97-18

Wet Clarification Memorandum & Recent AMSA Transmittal

Attached is a recently issued July 21 policy memorandum from EPA Office of Science and Technology Director, Tudor Davies, and EPA Office of Wastewater Management Director, Michael Cook to Regional Water Management and Environmental Services Division Directors concerning additional clarifications for Whole Effluent Toxicity (WET) methods and implementation in permits. The memorandum specifies:

  1. The Agency has not established nationally applicable criteria for WET, for either acute or chronic toxicity under CWA 304(a).

  2. The Agency does not mandate which test methods NPDES permitting authorities must use, however, any method used must be approved.

  3. Permitting authorities should consider biological assessment, and other relevant data when available, in determining whether the discharge will cause, or have reasonable potential to cause or contribute to a violation of a State water quality standard.

  4. Permitting authorities may use different toxicity limitations for seasonal flow differences, however, emphasizes that increased monitoring frequencies are needed when permits contain seasonal limits.

  5. Emphasizes that permit decisions should utilize the most representative data in "reasonable potential" analyses, including data which shows lower levels of toxicity attributable to a discernable control action (resulting from a TIE/TRE) and which will be maintained.

Also for your information, is a recent AMSA transmittal to EPA summarizing the highlights of a June 23-24 stakeholder meeting on WET issues, and also urging EPA to eliminate enforceable WET tests as permit limits. If you have any questions, please contact Sam Hadeed, AMSA at 202/833-4655 or shadeed@amsa-cleanwater.org.

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