Status of the WET Program

William TelliardDirector, Analytical Methods

USEPA Office of Science & Technology

Office of Water

Office of Water

What is WET?

Whole effluent toxicity (or WET) is defined as the combined toxic effect of an effluent measured directly by an aquatic toxicity test

WET is one of three components of EPA’s integrated approach to water quality-based toxics control

17 WET test procedures using plants, fish, and invertebrates are promulgated at 40 CFR Part 136

EPA's Water Quality-Based Toxics Control Strategy

WET Controls

Chemical Controls

Bioassess-ments

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Background

WET Methods Rule Promulgated - Whole effluent toxicity (WET) test methods were promulgated at 40 CFR Part 136 on 10/26/95 for use in monitoring water quality, controlling toxic discharges, and protecting aquatic life in receiving waters (60 FR 53529)

WET Methods Rule Challenged - 6 different litigants sued EPA in 5 different courts of appeal

Resulted in Settlement Agreements - Law suits were settled by 3 different settlement agreements

United Water Florida, City of Washington, City of San Bernadino

Lone Star Steel

Edison Electric Institute, Western Coalition of Arid States, et al. (EEI/WestCAS)

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Settlement Agreement Requirements

In a 7/24/98 settlement agreement with Edison Electric Institute, et al., EPA agreed to: Publish technical correction notice (completed 2/99) Publish analytical variability guidance (completed 6/00) Publish method guidance document (completed 7/00) Conduct WET Interlaboratory Variability Study (the WET Study)

(completed 4/00) Publish table of method variability measurements (CVs)

(completed 9/01) Propose method changes (proposed 9/01; final rule to be

completed by 11/08/02) Propose to ratify or withdraw methods (proposed 9/01; final rule

to be completed by 11/08/02)

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Technical Correction Notice

Errata for the Effluent and Receiving Water Toxicity Testing Manuals - EPA 600/R-98/182

Corrects technical errors and omissions in WET method manuals Available at:

http//www.epa.gov/waterscience/WET This errata will soon be unnecessary,

when EPA publishes new method

manual editions in November

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Guidance Documents

Method Guidance Document Method Guidance and Recommendations for Whole Effluent

Toxicity (WET) Testing (40 CFR Part 136) – EPA 821/B-00/004 Provides Guidance on:

Nominal error rates Confidence intervals Concentration-response relationships Dilution series selection Dilution waters

Available at: http//www.epa.gov/waterscience/WET

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Guidance Documents

Variability Guidance Document Understanding and Accounting for Method Variability in Whole

Effluent Toxicity Applications Under the National Pollutant Discharge Elimination System Program – EPA 833/R-00/003

Provides guidance to regulatory authorities,

permittees, and testing labs on how to

understand and account for measurement

variability in WET testing Available at:

http//www.epa.gov/waterscience/WET

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September 28, 2001 Proposed Rule

On September 28, 2001, EPA published a proposed rule to revise and ratify WET test methods

Proposed rule fulfills requirements of two WET settlement agreements

Summary of proposed rule Method revisions - incorporates revisions to address specific

stakeholder concerns Interlaboratory Variability Study - summarizes results from EPA’s

WET Interlaboratory Variability Study Ratification/withdrawal - ratifies or withdraws WET test methods

based on results from the WET Interlaboratory Variability Study

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Method Revisions

Correct minor technical errors Update methods with newly collected method precision data Address specific stakeholder concerns

blocking by known parentage pH drift concentration-response relationships dilution series dilution waters pathogen interference

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WET Interlaboratory Variability Study

Largest most comprehensive study of whole effluent toxicity test methods to date

Test methods -12 of the 17 approved WET test methods evaluated in the study

Laboratories - 56 different laboratories involved, each in an average of 3 methods

Samples - over 700 samples analyzed

Sample types - effluents, receiving waters, blanks, and reference toxicants

Study data summarized in proposed rule to support ratification of WET methods

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Ratification/Withdrawal

11 of 12 methods evaluated in the WET Study were proposed for ratification

Ratification means that EPA reaffirms its previous approval of these methods for use in National Pollutant Discharge Elimination System (NPDES) monitoring and compliance

1 method (Holmesimysis costata acute method) was proposed for withdrawal and reproposal

WET Study results revealed that this test procedure, which was designed for a related species (Mysidopsis bahia), is inadequate for the Holmesimysis costata test species

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Current Status

EPA received public comment on the proposed rule through January 11, 2002

EPA received 38 comment packages from the following groups:– Laboratories; POTWs; Regulatory authorities; Industries; Industry or

trade associations; Environmental companies representing POTWs or industry

EPA plans to take final action on the proposed rule by November 2002

New editions of each of the 3 WET method manuals are expected by November 2002