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TMDLs addressing the states' general water quality standards and benthic impairment typically employ wasteload allocations for “Whole Effluent Toxicity” (WET) parameters. This is because the states' narrative “no toxics in toxic amounts” water quality standards
are notoriously difficult to implement. EPA's traditional three tiers of water quality indicators – chemical-specific water quality standards, whole effluent toxicity-based standards, and bioassessments and other direct measures of instream impact - are not equally susceptible to identification
and measurement. When TMDLs must be developed to address the latter two, point source wasteload allocations (WLA) have generally been developed based on WET parameters. In 1995, EPA for the first time promulgated in 40 Code of Federal Regulations Part 136 acute and chronic Whole Effluent
Toxicity test procedures. Those procedures were immediately challenged in the U.S. Court of Appeals for the District of Columbia Circuit. Following provisional settlement and a lengthy reexamination and repromulgation process, EPA again in November 2002 promulgated acute and chronic WET procedures,
reaffirming its earlier promulgation of most procedures (some with modifications), and deleting from the approved list certain other procedures. A diverse group of Petitioners, including our clients, again immediately challenged EPA's promulgation in U.S. Circuit Court. In that challenge the
Petitioners asserted that the chronic test procedures nonlethal endpoints (generally growth and reproduction) are inaccurate, fail to meet standards for accuracy and correctness required by the Clean Water Act, fail to meet evidentiary standards sufficient for the NPDES program purposes for
which these and other analytical test procedures are used, and generally are not adequately representative of instream impacts. The challenge to some of the chronic Whole Effluent Toxicity test procedures was fully briefed by the Petitioners and EPA, and the Court heard oral arguments on
October 15, 2004. The Court's decision of December 10, 2004 upheld the challenged WET methods, but it will nonetheless have profound effects on the manner in which TMDLs addressing benthic impairment and more generally addressing narrative water quality standards will be implemented and enforced.
As this paper is finalized, the Court is considering a Petition for Rehearing by some of the Petitioners and spirited arguments thereon by both sides. Although WET procedures have been used for NPDES purposes for nearly 30 years, much of the historical use has been for strict analytical
purposes as opposed to use as numeric NPDES permit limitations. Where numeric WET limitations have been imposed, enforcement has been cautious because of the legal status of the underlying test procedures. The case will contribute to a determination of how WET procedures will be used in the
future and in particular how they will be used to form, implement, and enforce TMDLs addressing narrative water quality standards. Because the court upheld the chronic, non-lethal WET endpoints, the use of these test procedures for TMDL purposes is likely to expand. We will address new
ways the methods may be used as well as uses accommodating, notwithstanding the Court's rejection of the appeal, the Petitioners' concerns about the chronic, non-lethal endpoints. Also, the Court provided valuable guidance on the challenged WET test procedures and we address the continued
use in TMDLs of the WET methods. We also address possible efforts to correct those chronic, non-lethal endpoint test procedures and their possible continued use in the interim in TMDLs.
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