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

Note: EPA no longer updates this information, but it may be useful as a reference or resource.

 [Federal Register: July 18, 2000 (Volume 65, Number 138)]
[Notices]
[Page 44528-44529]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr18jy00-87]

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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]
BILLING CODE 6560-50-P

 
 

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