[Federal Register Volume 63, Number 159 (Tuesday, August 18, 1998)]
[Notices]
[Pages 44256-44258]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-22202]



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ENVIRONMENTAL PROTECTION AGENCY

[OW-FRL-6147-1 ]

Water Quality Criteria


Notice of Ambient Water Quality Criteria

AGENCY: Environmental Protection Agency (EPA).

ACTION: Notice of updated recommended aquatic life criteria for ammonia 
in freshwater, and request for comments.

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SUMMARY: Pursuant to Section 304(a)(1) of the Clean Water Act, the 
Environmental Protection Agency (EPA) announces the publication and 
availability of a document 1998 Update of Ambient Water Criteria for 
Ammonia, and requests comment on this document. The document contains 
EPA's recommended ammonia criteria for the protection of freshwater 
aquatic life. These criteria are EPA's recommendations for States, 
Territories, and authorized Tribes to use as guidance in adopting water 
quality standards. Such standards may form the basis for establishing 
enforceable, water quality-based controls. These water quality criteria 
are not regulations, and do not impose legally-binding requirements on 
EPA, States, Territories, Tribes or the public. States, Territories and 
authorized Tribes on a case-by-case basis retain the discretion to 
adopt water quality standards that differ from these recommendations 
where appropriate. Although EPA is requesting comment on this document, 
these criteria constitute the Agency's current recommended Section 
304(a)(1) criteria, and will continue to serve as such until EPA 
publishes a revision. Based on its assessment of public comments and 
other available information, EPA will either publish a revision to the 
guidance or will publish a notice indicating its decision not to 
revise.

OBTAINING THE DOCUMENT: Copies of the complete document, titled 1998 
Update of Ambient Water Quality Criteria for Ammonia, may be obtained 
from EPA's Water Resource Center by phone at 202-260-7786, or by e-mail 
to [email protected], or by web browser at www.epa.gov/
ostwater/rescnter.html, or by conventional mail to EPA Water Resource 
Center, RC-4100, 401 M Street SW, Washington, DC 20460. Alternatively, 
consult www.epa.gov/OST/pubs for download availability.

EXAMINING THE ADMINISTRATIVE RECORD: The Administrative Record 
supporting this guidance document is available under docket number W-
98-20 at the Water Docket, Room EB-57, Environmental Protection Agency, 
401 M Street SW, Washington, DC 20460 on work days between 9 a.m. and 4 
p.m. For access to docket materials call (202) 260-3027 to schedule an 
appointment. The record contains complementary material on current 
related work not included in the update document, as well as 
supplementary historical materials. A reasonable fee will be charged 
for photocopies.

SUBMITTING COMMENTS: An original and two copies of written comments 
should be submitted by October 2, 1998, and addressed to W-98-20, 
Ammonia Criteria Comment Clerk; Water Docket (MC-4101), U.S. EPA, 401 M 
Street SW, Washington, DC 20460. Comments may be submitted 
electronically in ASCII or Word Perfect 5.1, 5.2, or 6.1 formats to OW-
D[email protected].

SUPPLEMENTARY INFORMATION:

Background on Program

    Section 304(a)(1) of the Clean Water Act (33 U.S.C. 1314(a)(1)) 
authorizes EPA to publish and periodically update ambient water quality 
criteria. These criteria are to reflect the latest scientific knowledge 
on the identifiable effects of pollutants on public health and welfare, 
aquatic life, and recreation. These criteria serve as guidance to 
States, Territories, and authorized Tribes in developing water quality 
standards under Section 303(c) of the CWA, and ultimately provide a 
basis for controlling discharges or releases of pollutants. In this 
notice EPA is announcing the publication and availability of the 
Agency's most recent calculation of water quality criteria for ammonia.
    Ambient water quality criteria developed under Section 304(a) are 
based solely on data and scientific judgments on the relationship 
between pollutant concentrations and effects on aquatic life, human 
health, and the environment. Section 304(a) criteria do not reflect 
consideration of economic impacts or the technological feasibility of 
meeting the chemical concentrations in ambient water.

Background on Development of this Criteria Document

    In 1985, EPA published Ambient Water Quality Criteria for Ammonia--
1984, which contained criteria concentrations for protection of 
freshwater aquatic life. The Criterion Maximum Concentration or CMC, 
which applied to short (acute) exposure, and the Criterion Continuous 
Concentration or CCC, which applied to longer (chronic) exposure, 
varied with temperature, pH, and with the type of fishery involved. On 
July 30, 1992, EPA revised its recommended value for the CCC through a 
memorandum ``Revised Tables for . . . Freshwater Ammonia 
Concentrations.''
    In late 1996 EPA undertook a review and revision of the CCC for 
ammonia, in response to public interest in the criterion. EPA produced 
a draft on June 5, 1997. EPA obtained a peer review, Peer Review Report 
for EPA's Addendum to Ambient Water Quality Criteria Document for 
Ammonia, dated October 9, 1997. After considering and responding to the 
peer review comments, EPA is in this notice publishing revised criteria 
recommendations, superseding all previous freshwater ammonia criteria. 
EPA will consider public comments on the material of this notice in 
determining the need for further revisions.
    The document announced in this notice pertains only to fresh 
waters. It does not change or supersede the EPA criterion for ammonia 
in salt water, published in Ambient Water Quality Criteria for Ammonia 
(Saltwater)--1989.
    EPA aquatic life criteria consist of acute and chronic criteria 
concentrations, applicable averaging periods, and allowable excursion 
frequencies. The document announced in this notice revises (a) the pH 
and temperature relationship of the CMC (acute criterion) based on re-
evaluation of the data in the 1984/1985 criteria document, (b) the CCC 
(chronic criterion), including its pH and temperature relationship, 
based on new data in addition to what was available for the 1984/1985 
document, and (c) the averaging period applicable to the CCC. The 
revisions do not address, and are not intended to modify (d) the 
averaging period applicable to the CMC, or (e) the recommended 
frequencies for excursions of the CMC or CCC.

Ammonia Criteria Concentrations

    In natural waters ammonia exists in two forms, un-ionized NH3, and 
ionized NH4+, with equilibrium controlled by 
temperature and pH. Whereas the 1984/1985 criteria were derived based 
on un-ionized ammonia, which required a relationship with temperature, 
the criteria published today are expressed only as total (un-ionized 
plus ionized) ammonia, the toxicity of which does not appear 
empirically to vary with temperature. Consequently, while the criteria 
published today vary with pH, they do not vary with temperature.

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    Based on differences in species acute sensitivity, different CMC 
values were derived for waters where salmonids (e.g., trout and salmon) 
are present and waters where salmonids are not present. Such 
distinctions in species chronic sensitivity were not apparent, however. 
Consequently the CCC does not vary with the type of fish present. The 
criteria concentrations are shown in Table 1. For brevity, only a few 
example pH values are shown here. Refer to the criteria document for 
the computational formula and for other example pH values between 6.5 
and 9.0.

       Table 1.--CMC and CCC (mg N/L) at a few Example pH Values.       
------------------------------------------------------------------------
                                        CMC          CMC                
                pH                   (salmonids   (salmonids      CCC   
                                      present)     absent)              
------------------------------------------------------------------------
6.5...............................        32.5         48.8         3.48
7.0...............................        24.0         36.1         3.08
7.5...............................        13.3         19.9         2.28
8.0...............................         5.60         8.40        1.27
8.5...............................         2.13         3.20        0.57
9.0...............................         0.88         1.32        0.25
------------------------------------------------------------------------

    Whereas the 1984/1985 and 1992 total ammonia criteria were 
expressed in milligrams ammonia per liter (ammonia molecular weight 
17.0306 daltons), the currently proposed criteria are expressed in 
milligrams ammonia nitrogen per liter (nitrogen molecular weight 
14.0067 daltons). This change was suggested by criteria users. To 
compare the 1984/1985 and 1992 criteria to the currently proposed 
criteria, multiply the 1984/1985 or 1992 total ammonia values by 0.822.

Averaging Period

    The ambient concentration, averaged over a period of 30 days, 
should not exceed the CCC. The ambient concentration, averaged over 
four days, should not exceed a concentration two times greater than the 
CCC.
    The averaging period applicable to the CMC, one hour, was not 
addressed in this criteria update effort, and thus remains unchanged 
from 1984/1985.

Cold-Season Application

    Because the costs of biological treatment of ammonia increase 
substantially as the water temperature drops, establishing the cold-
season ammonia concentrations necessary for protecting aquatic life 
uses is of particular importance. Two factors affect the 
appropriateness of the above CCC during cold seasons. First, with 
respect to chronic toxicity of ammonia to fish, the most sensitive life 
stages are early life stages, which in many, but not all water bodies, 
do not occur in during the cold season. Second, for the most sensitive 
invertebrates, the toxicity of ammonia appears to decrease with 
decreasing temperature. For this reason, EPA has concluded that under 
some circumstances the cold-season CCC could be relaxed somewhat, 
although setting the appropriate criteria value involves uncertainties.
    In light of the evidence available, EPA recommends the following 
risk management policies with regard to cold-season ammonia criteria:
     While the cold-season ammonia criterion may in some cases 
be different than the criterion applicable to other seasons, all 
periods of the year should be covered by some ammonia criterion.
     If a state, territory, or authorized Tribe can make a 
finding, for a site or ecoregion, that identifies a time of year when 
no sensitive life stages of any fish species are ordinarily present in 
numbers affecting the sustainability of populations, the criterion 
applicable to that time of year may be set up to 3-fold higher than the 
criterion applicable to the remainder of the year. Baseline and 
subsequent biological monitoring in accordance with currently available 
EPA guidance should be conducted to assure that the integrity of the 
aquatic community being protected is maintained when these higher cold-
season concentrations are allowed.
     Alternatively, if a state, territory, or authorized Tribe 
can demonstrate, based on rigorous baseline and subsequent instream 
biological monitoring, that particular eco-regions can fully support 
beneficial fisheries uses, defined by appropriate biological measures, 
under the cold-season concentration regimes occurring at monitored 
sites in the eco-region, then the cold-season criterion may be set more 
than 3-fold higher than the applicable criterion to accord with the 
results of such analysis. In judging the adequacy of the instream 
biological monitoring, EPA would rely on its May 1996 guidance 
``Biological Criteria, Technical Guidance for Streams and Small 
Rivers'' (EPA 822-B-96-001) or later updates when they become 
available.

Endangered or Threatened Species

    Because the criteria are generally designed to protect 95 percent 
of all fish and aquatic invertebrate taxa, there remains a small 
possibility that the criteria will not protect all listed endangered or 
threatened species. Consequently, EPA recommends the following:

    In adopting ammonia criteria for specific water bodies, States 
and Tribes may need to develop site-specific modifications of the 
criteria to protect listed endangered or threatened species, where 
sufficient data exist indicating that endangered or threatened 
species are more sensitive to a pollutant than the species upon 
which the criteria are based. Such modifications may be accomplished 
using either of the following two procedures: (1) If the CMC is 
greater than 0.5 times the Species Mean Acute Value for a listed 
threatened or endangered species, or a surrogate for such species, 
obtained from flow-through, measured-concentration tests, then the 
CMC should be reset equal to 0.5 times that Species Mean Acute 
Value. (The empirical factor 0.5 converts from a 50 percent 
lethality concentration to a minimal-lethality concentration.) If 
CCC is greater than the Species Mean Chronic Value of a listed 
threatened or endangered species or surrogate, then the CCC should 
be reset to that Species Mean Chronic Value. (2) The site-specific 
criteria may be calculated using the recalculation procedure for 
site-specific modifications described in Chapter 3 of the U.S. EPA 
Water Quality Standards Handbook, Second Edition--Revised (1994).

Issues for Public Comment

    Because the ammonia CCC is so much lower than the CMC, the CCC is 
expected to be the basis for water quality-based controls much more 
often than is the ammonia CMC. EPA is therefore particularly interested 
in public comment addressing the scientific basis for the CCC. For 
comments addressing the CMC or its associated averaging period, EPA 
would find it helpful if the commenter would explain how the comment 
issue would affect water quality-based controls.
    While welcoming all comments, EPA especially solicits additional 
data on the

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chronic toxicity of ammonia to aquatic life, comments on the 
interpretation of data on ammonia-sensitive species such as fingernail 
clam, rainbow trout, bluegill, and Hyalella, field data relevant to 
effects and effect concentrations of ammonia under summer and winter 
conditions, and comments on the cold-season policy presented above.
    Based on public comments and any other new information available, 
EPA will decide whether revision of the criteria is necessary. EPA will 
subsequently publish a notice indicating either its revised criteria 
recommendations, or its decision not to revise.

    Dated: August 3, 1998.
J. Charles Fox,
Acting Assistant Administrator for Water.
[FR Doc. 98-22202 Filed 8-17-98; 8:45 am]
BILLING CODE 6560-50-P