[Federal Register Volume 65, Number 138 (Tuesday, July 18, 2000)]
[Notices]
[Pages 44528-44529]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 00-18102]


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ENVIRONMENTAL PROTECTION AGENCY

[FRL-6838-6]


Notice of Availability, ``Understanding and Accounting for Method 
Variability in WET Applications Under the NPDES Program''

AGENCY: Environmental Protection Agency (EPA).

ACTION: Notice of availability of document.

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SUMMARY: On June 30, 2000, EPA issued the final document, entitled 
``Understanding and Accounting for Method Variability in Whole Effluent 
Toxicity (WET) Applications Under the NPDES Program'' in response to 
questions on WET test method variability. WET applications are 
implemented under the National Pollutant Discharge Elimination System 
(NPDES) Program.

DATES: Final document issued June 30, 2000.

ADDRESSES: A copy of the final document and supporting documents 
including the public comments received by EPA on the July 26, 1999 
draft document are available for review at the EPA's Water Docket, Room 
EB57, 401 M Street, S.W., Washington, D.C. 20460. For access the Docket 
materials, call (202) 260-3027 between 9 a.m. and 3:30 p.m. Eastern 
Time for an appointment.
    The complete text of this Federal Register notice and 
``Understanding and Accounting for Method Variability in Whole Effluent 
Toxicity (WET) Applications Under the NPDES Program'' may be viewed or 
downloaded on the Internet at http://www.epa.gov/owm/npdes.htm.

FOR FURTHER INFORMATION CONTACT: For technical questions on this 
document, contact Debra Denton, (415-744-1919) or Laura Phillips (202-
260-9522), Water Permits Division, (4203), USEPA, Office of Wastewater 
Management, 1200 Pennsylvania Avenue, N.W., Washington, D.C. 20460. 
Copies of the document may be requested from the Office of Water's 
Resource Center at (202-260-1827) or by contacting the National Center 
for Environmental Publications and Information (NCEPI) at (513-489-
8190).

SUPPLEMENTARY INFORMATION:

Background

    The Whole Effluent Toxicity (WET) approach to protection of water 
quality is the focus of this document. In 1989, EPA defined whole 
effluent toxicity as ``the aggregate toxic effect of an effluent 
measured directly by an aquatic toxicity test.'' At the same time, EPA 
promulgated regulations requiring NPDES permit limitations for WET 
under certain circumstances. [54 FR 23868 at 23895, June 2, 1989]. 
Aquatic toxicity tests are laboratory experiments that measure the 
biological effect (e.g., growth, survival, and reproduction) of 
effluents or receiving waters on aquatic organisms. In aquatic toxicity 
tests, groups of organisms of a particular species are held in test 
chambers and exposed to different concentrations of an aqueous test 
sample, for example, a reference toxicant, an effluent, or a receiving 
water. Observations are made at predetermined exposure periods. At the 
end of the test, the responses of test organisms are used to estimate 
the effects of the toxicant or effluent. In the early 1980s, EPA 
published methods (USEPA 1985, 1988, 1989) for estimating the short-
term acute and chronic toxicity of effluents and receiving waters to 
freshwater and marine organisms.

Effect of This Document

    EPA is providing this document to clarify several issues regarding 
WET variability and reaffirm EPA's earlier guidance and recommendations 
published in the Technical Support Document for Water Quality-Based 
Toxics Control (TSD, USEPA 1991). Today's document is intended to 
provide NPDES regulatory authorities and all stakeholders, including 
permittees, with guidance and recommendations on how to understand and 
account for measurement variability in WET testing.

Three Goals of Today's Document

    Today's document describes three goals EPA has defined to address 
issues surrounding WET variability. In addition, the document is 
intended to satisfy the requirements of a settlement agreement to 
resolve litigation over rulemaking to standardize WET testing 
procedures. These three goals are:
    1. To quantify the variability of the promulgated test methods and 
report a coefficient of variation (CV) as a measure of test method 
variability.
    2. To evaluate the statistical methods described in the Technical 
Support Document for Water Quality-Based Toxics Control (TSD) for 
determining the need for and deriving WET permit conditions.
    3. To suggest guidance for regulatory authorities on approaches to 
address and to minimize test method variability. In addition, the 
document is intended to provide guidance to regulatory authorities, 
permittees, and WET testing laboratories on conducting the biological 
and statistical methods and evaluating test effect concentrations.

Principal Conclusions

    The principal conclusions of this document in response to the three 
document goals follow.

Evaluation of Test Method Variability

     Comparisons of WET method precision with method precision 
for analytes commonly limited in NPDES permits demonstrate that the 
variability of the promulgated WET methods is within the range of 
variability experienced in other types of analyses. Several researchers 
also noted that method performance improves when prescribed methods are 
followed closely by experienced analysts.
     The document provides interim CVs for promulgated WET 
methods in Appendix A of the final document pending completion of 
between-laboratory studies, which may affect these interim CV 
estimates.

Evaluation of Approach To Incorporate Test Method Variability

     EPA's Technical Support Document for Water Quality-based 
Toxics Control (TSD) presents guidance for developing effluent limits 
that appropriately protect water quality, regarding both effluent 
variability and analytical variability, provided that the WET criteria 
and waste load allocation (WLA) are derived correctly.
     EPA's analysis of data gathered in the development of 
today's document indicates that the TSD approach appropriately accounts 
for both effluent variability and method variability. EPA does not 
accept that a reasonable alternative approach is available to determine 
a factor that would discount the effects of method variability in TSD 
procedures based on CVs because the approach would not assure adequate 
protection of water quality.

Development of Guidance to Regulatory Authorities

     EPA recommends that NPDES permitting authorities implement 
the statistical approach as described in the

[[Page 44529]]

TSD to evaluate effluent and to derive WET limits or monitoring 
triggers.
     EPA recommends that NPDES permitting authorities calculate 
the facility-specific CVs using point estimate techniques to determine 
the need for and to derive a permit limit for WET, even if self-
monitoring data are to be determined using hypothesis testing 
techniques, for example, to determine a ``no effect concentration 
(NOEC)''. The document describes such facility-specific calculation 
procedures.

Additional Recommendations and Guidance

    This document also provides recommendations and guidance on 
minimizing variability in three specific areas in order to generate 
sound WET test results: (1) Obtaining a representative effluent sample; 
(2) conducting the toxicity tests properly to generate the biological 
endpoints; and (3) conducting the appropriate statistical analysis to 
determine the effect concentrations (IC25, NOEC). If these 
recommendations are addressed, the reliability of the test endpoint 
values should improve.
     Permitting authorities should design a sampling program 
that collects representative effluent samples to fully characterize 
effluent variability for a specific facility over time.
     Permitting authorities should ensure proper application of 
WET statistical procedures and test methods.
     EPA recommends that NPDES permitting authorities 
incorporate both the upper and lower bounds using the percent minimum 
significant difference (PMSD) to control and to minimize within-test 
method variability and increase test sensitivity. To achieve the PMSD 
upper bound, either the replication should increase or within-test 
method variability should decrease, or both.
     EPA recommends that WET testing laboratories maintain 
control charts for PMSD and the control mean and report the PMSD with 
all WET test results.
     NPDES permitting authorities should develop a quality 
control checklist to assist in evaluating and interpreting toxicity 
test results.
     EPA recommends that permitting authorities and 
laboratories participate in the National Environment Laboratory 
Accreditation Program and conduct routine performance audit inspections 
to evaluate laboratory performance.

    Dated: July 12, 2000.
Michael B. Cook,
Director, Office of Wastewater Management.
[FR Doc. 00-18102 Filed 7-17-00; 8:45 am]
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