Water Quality Criteria; Notice of Availability; 1999 Update of Ambient Water Quality Criteria for Ammonia

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

[Federal Register: December 22, 1999 (Volume 64, Number 245)]
[Notices]
[Page 71973-71980]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr22de99-147]

[[Page 71973]]

_______________________________________________________________________

Part VI

Environmental Protection Agency

_______________________________________________________________________

Water Quality Criteria; Notice of Availability; 1999 Update of Ambient
Water Quality Criteria for Ammonia; Notice

[[Page 71974]]

ENVIRONMENTAL PROTECTION AGENCY

[FRL-6513-6]

Water Quality Criteria; Notice of Availability; 1999 Update of
Ambient Water Quality Criteria for Ammonia

AGENCY: Environmental Protection Agency (EPA).

ACTION: Notice of availability.

-----------------------------------------------------------------------

SUMMARY: Pursuant to Section 304(a)(1) of the Clean Water Act (CWA),
the Environmental Protection Agency (EPA) announces the publication and
availability of the 1999 Update of Ambient Water Quality Criteria for
Ammonia (1999 Update), containing 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. Water quality
standards form the basis for establishing enforceable, water quality-
based effluent limitations in CWA permits. These criteria constitute
the Agency's current recommended Section 304(a) criteria for ammonia,
and will continue to serve as such until EPA publishes a revision. In
August 1998, EPA published the 1998 Update of Ambient Water Criteria
for Ammonia and asked for public comment. The 1999 Update published
today incorporates revisions made in response to comment on the 1998
Update, and supercedes all previous freshwater ammonia criteria.

ADDRESSES: ``Obtaining the Document.'' A copy of the document, 1999
Update of Ambient Water Quality Criteria for Ammonia (EPA-822-R-99-014)
may be obtained from the U. S. Environmental Protection Agency, by
contacting: National Service Center for Environmental Publications
(NSCEP), P.O. Box 42419, Cincinnati, Ohio, USA 45242-2419, Phone: 1-
800/490-9198; International: 1/513-489-8190, E-mail:
ncepi.mail@epamail.epa.gov.
The document, and a fact sheet that provides an overview of the
criteria document, may be viewed on the Internet at http://www.epa.gov/
ost/standards/amonsub.html.
``Examining the Administrative Record.'' The Administrative Record
supporting EPA's recommended ammonia criteria for the protection of
freshwater aquatic life 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 Monday through Friday, excluding Federal
holidays, between 9:00 a.m. and 4:00 p.m. For access to docket
materials call (202) 260-3027 for an appointment. The record contains
material that EPA relied on to support the recommended criteria
contained in the 1999 update. A reasonable fee will be charged for
photocopies.

FOR FURTHER INFORMATION CONTACT: Brian Thompson, Standards and Applied
Science Division (4305), U.S. EPA, Office of Science and Technology,
401 M. Street, S.W., Washington, D.C. 20460; (202) 260-3809;
thompson.brian@epamail.epa.gov.

SUPPLEMENTARY INFORMATION:

Table of Contents

I. Background on Criteria Program
II. Background on Development of this Criteria Document
III. Response to Comments on 1998 Update
A. Ammonia pH Relationship
B. Ammonia Temperature Relationship
IV. Summary of the 1999 Ammonia Criteria
V. Implementation of the Final 1999 Ammonia Criteria
A. Design Flow and Averaging Period
B. Early Life Stage Absent (ELS-Absent) Provision
C. State and Tribal Adoption of Ammonia Criteria
VI. Threatened or Endangered Species

I. Background on Criteria Program

Section 304(a)(1) of the Clean Water Act (33 U.S.C. 1314(a)(1))
directs 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 adopting water quality
standards under Section 303(c) of the CWA that protect aquatic life
from acute and chronic effects of ammonia. Water quality standards
provide a basis for controlling discharges or releases of pollutants.
Under the CWA, States and Tribes are to establish water quality
criteria to protect designated uses. State and tribal decision makers
retain the discretion to adopt water quality criteria on a case-by-case
basis that differ from this guidance when appropriate and where
supported by local data. In this notice EPA is announcing the
publication and availability of the Agency's most recent calculation of
water quality criteria for freshwater ammonia.
Ambient water quality criteria developed under Section 304(a) are
based 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.

II. Background on Development of the Ammonia 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 primarily with pH and 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. As part of
this process, EPA undertook peer review of a draft criterion (June 5,
1997). The results of this peer review are included in Peer Review
Report for EPA's Addendum to Ambient Water Quality Criteria Document
for Ammonia, dated October 9, 1997. On August 18, 1998, EPA published
the 1998 Update of Ambient Water Quality Criteria for Ammonia and
solicited public comment. Today, EPA is publishing the 1999 Update of
Ambient Water Quality Criteria for Ammonia, which incorporates changes
made in response to public comment on the 1998 Update. The ammonia
criteria published today supersede all previous freshwater aquatic life
ammonia criteria.
The water quality criteria in the 1999 Update pertain only to fresh
waters. They do 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 (i.e., the duration used
in comparing ambient water concentration to water quality criteria),
and allowable excursion frequencies. The criteria published today are
based on a revised temperature dependency of the CCC (chronic
criterion), and modification of the 4-day criterion provision from 2.0
to 2.5 times the CCC. As a result, the acute criterion for ammonia
remains dependent on pH and fish species (i.e., salmonids versus non-
salmonids), and the chronic criterion for ammonia is now dependent on
pH and temperature. In addition, at lower temperatures the chronic
criterion is also dependent on

[[Page 71975]]

the presence or absence of early life stages of fish.

III. Response to Comments on 1998 Update

EPA considered all comments submitted on the 1998 Update. Responses
to comments are contained in the document Response to Comment on the
1998 Update of Ambient Water Quality Criteria for Ammonia. The two most
significant issues raised in the comments were the pH relationship and
the temperature relationship used for the chronic criterion (CCC); that
is, how the CCC changes as a function of pH and as a function of
temperature.

A. Ammonia pH Relationship

In the 1998 Update, the pH relationship of the CCC was different
than the pH relationship of the CMC. Notably, in the pH range from 8.0
to 6.5, the CCC increased less quickly with decreases in pH than did
the CMC. Some commentors expressed concern that because so much more
data are available to derive the acute relationship than the chronic
relationship, it would be better to apply the acute relationship to the
chronic criterion.
EPA does not agree that the chronic pH relationship should be the
same as that of the acute pH. The data for smallmouth bass and for
daphnia unequivocally demonstrate that the acute-chronic ratio changes
with pH, and therefore that the chronic relationship should not be the
same as the acute relationship. While there may be alternative ways of
accounting for this difference, EPA believes that the approach it has
taken, to derive the chronic relationship directly from the available
chronic data for smallmouth bass and daphnia, is scientifically
appropriate and reasonable. Thus, for the 1999 Update, EPA has not
changed the chronic pH relationship.

B. Ammonia Temperature Relationship

In the derivation of the 1998 Update, the data used by EPA
indicated that the sensitivity of fish does not change significantly
with temperature, either for acute or chronic exposure. However, some
commentors expressed concern that the 1998 chronic criterion would
change with temperature if invertebrates are considered.
In response to these comments, EPA re-examined the available data
for invertebrates, which were from a study by Arthur et al. (1987), as
referenced in the 1998 and 1999 Updates. The Arthur et al. data
suggested a temperature relationship for invertebrates but not for
fish. In the 1998 Update, EPA did not use the Arthur et al. data
because the authors were concerned that other variable factors in their
tests might have had a potential to confound their results. In re-
examining their data in response to comments, however, EPA found that
the fish data from Arthur et al. showed behavior quite similar to that
from numerous other investigators, that is, little relationship with
temperature. Consequently, EPA concluded that the potential confounding
factors were unlikely to have much effect on the results, and that the
Arthur et al. (1987) results could be used to define a temperature
relationship for invertebrates.
In contrast to the fish data, the invertebrate data from Arthur et
al. (1987) show a significant and consistent relationship of increasing
lethal concentration (decreasing toxicity) with decreasing temperature.
Because the two most sensitive species in the chronic data set are
invertebrates, a temperature dependency for the effect concentrations
for these species results in an overall temperature dependency for the
ammonia chronic criterion. Therefore, EPA's 1999 Update contains a
temperature dependent chronic criterion for ammonia. This temperature
dependency does not affect the acute criterion, because none of the
acutely sensitive species in the acute data set are invertebrates.

IV. Summary of the 1999 Ammonia Criterion

In natural waters ammonia exists in two forms, un-ionized
NH<INF>3</INF>, and ionized NH<SUP>+4</SUP>, 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.
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 acute criterion or CMC is unchanged from 1998. The values vary
as a continuous function of pH and are not dependent on temperature.
For example, as seen in Table 1 below, at pH=7 the values are 24.1 mg
N/L for salmonid fish (trout and salmon) present, and 36.1 mg N/L for
salmonids absent. Whereas at pH=8 the values are 5.62 mg N/L for
salmonids present, and 8.40 mg N/L for salmonids absent.

Table 1.--Ammonia CMC Values Based pH and Fish Species
------------------------------------------------------------------------
CMC mg N/L
---------------------------
pH Salmonids Salmonids
present absent
------------------------------------------------------------------------
7........................................... 24.1 36.1
8........................................... 5.62 8.40
------------------------------------------------------------------------

The chronic criterion or CCC varies as continuous functions of
temperature and pH. At lower temperatures, the values also depend on
whether early life stages of fish are present or absent. To illustrate
its general behavior, the table below (Table 2) shows example values of
the CCC under a few different temperature and pH conditions.

Table 2.--Ammonia CCC Values Based on Temperature, pH, and Early Life Stages of Fish
----------------------------------------------------------------------------------------------------------------
CCC mg N/L
------------------------------------------------------
Early life stages of fish Early life stages of fish
Temperature present absent
------------------------------------------------------
pH=7 pH=8 pH=7 pH=8
----------------------------------------------------------------------------------------------------------------
0 deg. C.............................................. 5.91 2.43 9.60 3.95
10 deg. C................................................ 5.91 2.43 7.91 3.26
20 deg. C................................................ 4.15 1.71 4.15 1.71
30 deg. C................................................ 2.18 0.897 2.18 0.897
----------------------------------------------------------------------------------------------------------------

[[Page 71976]]

V. Implementation of the Final 1999 Ammonia Criteria

A. Design Flow and Averaging Period

The use of aquatic life criteria for developing water quality based
permit limits and for designing waste treatment facilities requires the
selection of an appropriate waste load allocation model. Dynamic models
are preferred for the application of aquatic life criteria in order to
make best use of the specified concentrations, durations, and
frequencies. If dynamic models cannot be used, then an alternative is
steady-state modeling. Because steady-state modeling is based on
various simplifying assumptions, it is less complex, and might be less
realistic, than dynamic modeling. However, since steady-state models
are easier to apply, they are used more often than dynamic models.
An important step in the application of steady-state modeling to
streams is calculating the design flow. States and Tribes can refer to
Appendix D of the Technical Support Document for Water Quality-based
Toxics Control (TSD) for EPA's recommended design flow, as well as
EPA's basis for its design flow recommendations.
In the TSD, for aquatic life, EPA recommends design flows for both
the criterion maximum concentration (CMC, or acute criterion) and the
criterion continuous concentration (CCC, or chronic criterion). For the
CMC, EPA recommends the 1B3 (the lowest one-day flow based on a three-
year return interval when flow records are analyzed using EPA's 1986
DFLOW procedure) or the 1Q10 (the lowest one-day flow based on a ten-
year return interval when flow records are analyzed using extreme-value
statistics). For the CCC, EPA recommends the 4B3 (the lowest four-day
flow based on a three-year return interval when flow records are
analyzed using EPA's 1986 DFLOW procedure) or the 7Q10 (the lowest
seven-day flow based on a ten-year return interval when flow records
are analyzed using extreme-value statistics).
For ammonia, EPA continues to recommend the 1B3 or the 1Q10 as the
design flow for the CMC. Even though EPA's recommended design flow for
the CCC, as stated in the TSD, is based on a 4-day average, EPA's
design flow guidance can be applied to the 30-day averaging period of
ammonia. Therefore, for the CCC for ammonia, EPA recommends the 30B3
for the design flow, if flow records are analyzed using EPA's 1986
DFLOW procedure. In addition, EPA believes that the 30Q10 and the 30Q5
are at least as protective as the 30B3. Therefore, if flow records are
analyzed using extreme-value statistics, EPA also recommends the 30Q10
or the 30Q5 as the design flow for the CCC for ammonia. As explained in
the 1999 Update, within this 30-day period, no 4-day average
concentration should exceed 2.5 times the CCC. Consequently, the design
flow should also be protective of any 4-day average at 2.5 times the
CCC. EPA believes that in the vast majority of cases, the 30Q10 is
protective of both the CCC (which, for ammonia, is associated with a
30-day average) and any 4-day average at 2.5 times the CCC. If the
ammonia CCC is implemented using the 30Q10, no further conditions are
necessary. However, if a State or Tribe specifies the use of the 30Q5,
then the State or Tribe should demonstrate that a 7Q10 (the lowest
average 7-day once-in-ten-year flow using extreme-value statistics) is
protective of 2.5 times the CCC, to ensure that any short term (4-day)
flow variability within the 30-day averaging period does not lead to
shorter-term chronic toxicity. Since the 7Q10 approximates the 4B3 (the
lowest average 4-day once-in-three year flow using EPA's 1986 DFLOW
procedure), EPA recommends the 7Q10 be used to evaluate if any 4-day
average within the 30-day averaging period will exceed 2.5 times the
CCC. The comparison of the 30Q5 at one times the CCC to the 7Q10 at 2.5
times the CCC is stream-specific; a State or Tribe utilizing this
approach should adopt both the 30Q5 at one times the CCC and the 7Q10
at 2.5 times the CCC into its standards and specify that the more
stringent be used.
In adopting a freshwater aquatic life CCC for ammonia, based on the
30-day averaging period recommended in the 1999 Update, the procedures
for calculating NPDES permit limits should be modified from those
described in the TSD. The equations (and corresponding ``multiplier
tables'') presented in the TSD assume a 4-day averaging period and are
summarized below:
The acute long term average (LTA<INF>a</INF>) is determined from
the acute wasteload allocation (WLA<INF>a</INF>) using the equation:
[GRAPHIC] [TIFF OMITTED] TN22DE99.012

The chronic long term average (LTA<INF>c</INF>) is determined from the
chronic wasteload allocation (WLA<INF>c</INF>) using the equation:
[GRAPHIC] [TIFF OMITTED] TN22DE99.013

A comparison of the LTA<INF>a</INF> and LTA<INF>c</INF> is then
performed and the minimum value is selected (LTA<INF>MIN</INF>). The
maximum daily limit (MDL) is then calculated from the LTA<INF>MIN</INF>
using the equation:
[GRAPHIC] [TIFF OMITTED] TN22DE99.014

The average monthly limit (AML) is calculated from the
LTA<INF>MIN</INF> using the equation:
[GRAPHIC] [TIFF OMITTED] TN22DE99.015

The value of ``n'' in the calculation of the AML is based on an assumed
monthly effluent monitoring frequency for the permittee. In general,
the ``n'' value should be set equal to the actual monitoring frequency
that will be required of the permittee. However, if the AML is based on
the LTA<INF>c</INF> (i.e., LTA<INF>MIN</INF> = LTA<INF>c</INF>), the
TSD recommends that the value of ``n'' be set no lower than 4
(corresponding to the 4-day CCC) to ensure that the AML does not exceed
the WLA<INF>c</INF>.
Since the 1999 Update recommends a 30-day averaging period for
deriving the CCC, the equation for determining the LTA<INF>c</INF>
should be modified as follows:
[GRAPHIC] [TIFF OMITTED] TN22DE99.016

The comparison of the LTA<INF>a</INF> and LTA<INF>c</INF> is then
performed in the same manner and the MDL and AML are calculated from
the LTA<INF>MIN</INF>.
Consistent with the guidance regarding the calculation of an AML
using a 4-day CCC, the value of ``n'' (assumed monitoring frequency)
used in the AML calculation should not be less than the averaging
period upon which the criterion value is based. For a more detailed
discussion of the selection of an appropriate value for ``n'' in limit
development, refer to Section 5.5.3 of the TSD.
B. Early Life Stage Absent (ELS-Absent) Provision
EPA is establishing a provision in its ammonia criteria that allows
for a relaxation of the CCC when early life stages (ELS) of fish are
not present, since, at low ambient water temperatures, adult and
juvenile fish are less sensitive to ammonia toxicity than are early
life stages of fish. EPA has concluded that it would be appropriate to
relax the ammonia CCC, as ambient water temperature decreases, in
waterbodies where early life stages are not present. This provision,
based on ELS absent, applies only to the recommended aquatic life
chronic criterion for ammonia, and any new or

[[Page 71977]]

revised water quality standard incorporating such a provision is
subject to review and approval by EPA.
The 1999 Update constitutes EPA's scientific recommendations
regarding ambient concentrations of ammonia that protect freshwater
aquatic life. EPA will review, and approve and disapprove, State and
Tribal water quality standards for ammonia, pursuant to section 303(c)
of the CWA and the implementing regulations at 40 CFR 131.
EPA has identified the following list of issues regarding the
implementation of the ELS-absent provision. These issues have been
raised to EPA since the August 1998 update. EPA is posing the issues in
a question and answer format to provide clarification on implementing
the ELS-absent provision. In the event that States, territories, and
authorized Tribes need further clarification on implementing the ELS-
absent provision, they should consult with their local EPA Regional
office.
1. What is the early life stage-absent (ELS-absent) provision?
Under specific conditions, States and Tribes may adjust their water
quality standards to reflect the decrease in ammonia toxicity to adult
and juvenile fish as water temperature decreases. Because ammonia
toxicity to early life stages of fish does not appear to decrease as
water temperature decreases, the ELS-absent provision is not allowed at
times of the year when early life stages are present. This ELS-absent
provision applies only to the aquatic life chronic criterion for
ammonia, and the adoption of this provision, as is the case for any new
or revised standard, is subject to approval by EPA.
The magnitude of the ELS-absent adjustment is dependent on
temperature, and can be found in EPA's 1999 Update of Ambient Water
Qaulity Criteria (1999 Update). In the 1999 Update, the ammonia chronic
criterion is presented in two separate tables, one for periods when
fish early life stages are present and one for periods when fish early
life stages are absent. Therefore, when early life stages of fish are
present, States and Tribes should use the ELS-present table, and when
early life stages of fish are absent, States and Tribes may use the
ELS-absent table.
2. How does EPA envision States and Tribes implementing the ELS-absent
provision?
States and Tribes should clearly identify in their water quality
standards the applicable ammonia criteria for all State or Tribal
surface waters for all times of the year. The approach a State or Tribe
may choose will differ depending on how its water quality program is
structured.
Some factors to consider in implementing the ELS-absent provision
are the resources available for State and Tribal Agencies to administer
site-specific risk management decisions; the variety of watersheds and
eco-regions within a State or Tribe; the diversity of fisheries within
the State or Tribe; and the geographic location of the State or Tribe.
For example, a State or Tribe in the Pacific Northwest may choose not
to modify criteria for ammonia at all, based on the absence of early
life stages of fish, because the State or Tribe is dominated by
salmonid fisheries with different species spawning throughout the year.
Another State or Tribe may choose to make ELS-absent adjustments to the
ammonia criteria site-specifically, when data or information is
provided which justifies a different, more appropriate ammonia
criterion. Many States and Tribes already have provisions in their
water quality standards which authorize site-specific criteria
modifications when new information becomes available. States and Tribes
that have invested resources in mapping the distribution of different
species within the State or Tribe may choose to determine which
waterbodies warrant the ELS-absent provision and adopt seasonal ammonia
criteria just for those waters as appropriate.
EPA believes that tailoring the ammonia criteria to different
classes of waterbodies would be the most efficient means of
administering the ammonia criteria ELS-absent provision. State and
Tribal programs with refined, biologically-based designated use
classification systems are best structured for this approach. Refining
the designated use to reflect the presence or absence of sensitive life
stages may involve an upfront investment of resources but in the long
term, EPA believes it significantly reduces the administrative burden
of having to repeatedly revise the standards site-specifically.
Refined, biologically-based use classification systems enable States
and Tribes to efficiently tailor numerous criteria to waterbodies with
shared characteristics. Refined, biologically-based use classification
systems also more clearly communicate the intended water quality goals
of a waterbody to the public.
Any approach a State or Tribe chooses to implement the ammonia
criteria must be reflected in the State's or Tribe's water quality
standards and submitted to EPA for review and approval. In order for
EPA to determine the scientific defensibility of a State's or Tribe's
approach as part of the Clean Water Act section 303(c) review and
approval/disapproval process, EPA would want to review information
concerning the geographic areas and the times of the year the ELS-
absent provision applies, and would want the State or Tribe to provide
all of the data and information the State or Tribe relied on for its
rationale.
3. Is the ELS-absent provision considered a site-specific criterion or
could a State or Tribe establish an eco-regional ELS-absent provision?
Could a State adopt an ELS-absent provision state wide? If a State or
Tribe uses an eco-region approach, what factors should it consider in
determining the ELS-absent provision for its waterbodies?
The ELS-absent provision could be done on either a site-specific
basis, or it may be more efficient to provide the adjustment on a
watershed or eco-regional basis if sufficient information and data
exist. If a State or Reservation is sufficiently small or homogenous,
it could apply the same provision on the same schedule state or
reservation-wide.
When establishing an ELS-absent provision on an eco-region basis,
the objective should be that waters within each eco-region have similar
periods when there is an absence of early life stages of fish. There
are a number of factors that a State or Tribe could use to define its
eco-regions. For example, if the spawning period of a given species of
fish and the ambient water temperature vary with latitude, then a State
or Tribe could use latitude to define its eco-regions. Other factors
that a State or Tribe could use to define its eco-regions include
watershed, elevation, and stream order. For smaller States or
Reservations, geographic variations are likely to be less extreme, and
will have a smaller effect on ambient water temperature and spawning
periods. As the size of a State or Reservation increases, it becomes
increasingly important to consider the effects of geographic variation
on ambient water temperature and spawning periods, and it becomes more
difficult to generalize about the level of protection afforded to the
aquatic communities. The larger the area of consideration for the ELS-
absent provision, the greater is the need for data or conservatism in
its application.
4. Which stages of fish development are included in the term ``early
life stages?'
The early life stages include the pre-hatch embryonic period, the
post-hatch free embryo or yolk-sac fry, and the

[[Page 71978]]

larval period, during which the organism feeds. Juvenile fish, which
are anatomically rather similar to adults, are not considered an early
life stage.
The duration of the early life stages extends from the beginning of
spawning through the end of the early life stages. Since the duration
of early life stages can vary according to fish species, EPA recommends
that any ELS-absent provision reflect such variations. A good source
for determining the duration of early life stages is The American
Society for Testing and Materials (ASTM) Standard E-1241, ``Standard
Guide for Conducting Early Life-Stage Toxicity Tests with Fishes'',
which uses the following durations when testing for toxicity on early
life stages (Table 3).

Table 3.--Duration of Early Life Stage Development of Selected Fish
Species
------------------------------------------------------------------------
Taxon End of early life stage development
------------------------------------------------------------------------
Fathead minnow............... 34 days after spawning.
Channel catfish.............. 34 days after spawning.
Bluegill..................... 34 days after spawning.
White Sucker................. 34 days after spawning.
Northern pike................ 34 days after spawning.
Striped bass................. 46 days after spawning.
Trout, salmon, char.......... 30 days after swim-up (swim-up is the
stage when fry leave the nest and swim
up to the surface to catch food).
------------------------------------------------------------------------

For taxa not listed above, the period for early life stage
development should be based on taxonomic and life history similarity.
5. To allow the ELS-absent provision, should there be a complete
absence of sensitive life stages or is the presence of very low
densities acceptable, as long as there is no threat to the overall
population? What should a State's or Tribe's determination of absence
of fish sensitive life stages consist of? Is actual biological survey
data required, or can a finding be based on expert opinion from
fisheries biologists? Is EPA going to specify any minimum biological
data requirements?
To be most protective of aquatic life in a waterbody being
considered for the ELS-absent provision, knowing that there is a
``complete absence'', or ``very low densities'' of sensitive life
stages of fish, would provide a high level of confidence in allowing
for the adjustment. However, actually measuring the ``complete
absence'' of sensitive life stages of fish in a waterbody may be very
difficult, if not impossible, even with rigorous, scientifically
designed sampling efforts. Most field sampling methods are not designed
to sample for these sensitive life stages. In addition, ``very low
densities'' are difficult to accurately measure without extensive fish
population sampling at critical times of the year. Further, because the
conditions for implementing an ELS-absent provision apply to all fish
species rather than to only game fish species, there may be less field
data readily available for all fish species comprising the aquatic
community at any given site. Therefore, the objective should be to best
identify the timeframes during the year when sensitive life stages are
most likely not to be present in numbers that, if chronic toxicity did
occur, would affect the long-term success of the fish population.
To best determine when the ELS-absent provision should be applied,
all readily available information regarding the fish species
distributions, spawning periods, nursery periods and the duration of
sensitive life stages found in the waterbody should be considered.
Information on waterbody temperature might also be useful. Expert
opinions from fisheries biologists and other scientists should be
considered, and where it can be obtained, the consensus opinion from a
diverse body of experts may be heavily relied upon.
The determination of the timeframe during the year when sensitive
life stages are most likely not to be present in numbers that, if
chronic toxicity did occur, would affect the long-term success of the
fish populations, should include a record of information adequate to
withstand public scrutiny. EPA will use this record as the basis upon
which to approve or disapprove the standard. The record should clearly
explain all the factors and information considered in arriving at the
determination. EPA does not have minimum data requirements for these
determinations; however, States and Tribes should rely on the
preponderance of available information. Without adequate and reliable
information, EPA would make the judgment that sensitive life stages are
present and must be protected at all times of the year.
6. Is the evaluation of the presence or absence of early life stages of
fish limited to what exists in a water body currently, or should
historical data on aquatic communities be considered?
According to the Clean Water Act, States and Tribes are to protect
existing uses, and therefore should protect for the most sensitive uses
that have occurred in a given waterbody since November, 1975. 40 CFR
131.12(a)(1) and 40 CFR 131.3(e). Hence, States and Tribes should
consider both current and historical species that have used a waterbody
for spawning and rearing since November, 1975. Even where water quality
is protective of designated uses, the current species composition in a
waterbody may not reflect all species that have used the waterbody for
spawning or rearing since 1975. It is EPA's position that any ELS-
absent provision should not prevent the return of any species
associated with an existing or designated use. Therefore, States and
Tribes should evaluate both current and historical data back to
November, 1975, in determining a presence or absence of sensitive life
stages.
7. In specifying in its water quality standards when the ELS-absent
provision applies, can a State or Tribe rely on the same date every
year based on average annual ambient water temperatures, or should a
State or Tribe rely on ambient water temperature thresholds that would
trigger the ELS-absent provision?
EPA believes that the best way for a State or Tribe to implement
its ELS-absent provision is to establish in its water quality standards
a fall and a spring date based on historical spawning and early life
stage data. Alternatively, a State or Tribe may

[[Page 71979]]

specify ambient water temperature thresholds that would serve as
surrogates for expected spawning and expected absence of early life
stages of fish. Upon reaching the temperature thresholds in the fall
and spring, the ELS-absent provision would go into effect.
Either approach may be suitable, however, EPA recommends the
establishment of a fall and spring date in a State's or Tribe's water
quality standards, because such an approach is simpler to implement in
NPDES (National Pollutant Discharge Elimination System) permits.
Alternatively if a State or Tribe establishes an ambient water
temperature threshold approach, it may specify the fall and spring
temperature thresholds in its water quality standards. These thresholds
would subsequently be implemented through water quality control
measures (e.g., NPDES permitting, TMDLs). EPA, in its review and
approval/disapproval of State and Tribal water quality standards, may
request that States and Tribes submit detailed procedures addressing
the implementation of this alternate approach. If the dates are decided
at the time of permit issuance, then the ambient water temperature
record (or other condition record) for the site would be evaluated
(along with the pH and flow record) as part of the permit issuance
process. The final NPDES permit would include fixed dates specifying
the seasonally varying water quality-based effluent limit (WQBEL).
Regardless of the approach taken, States and Tribes should keep in
mind the following concepts in determining the beginning and end of the
ELS-absent period. In the spring, a State or Tribe should consider when
(or at what ambient water temperature) early spring spawning is likely
to occur, and set the spring cut-off date (or temperature threshold)
accordingly. Setting a fall start date (or temperature threshold) is
more complicated because in addition to considering when the late
summer and early fall spawners are likely to stop spawning, a State or
Tribe should also consider the duration of the early life stages of the
late summer/early fall spawners. For instance, if the temperature
threshold was triggered for the latest fall spawner on October 15, and
its early life stage is expected to last 30 days, then the ELS-absent
provision would begin as early as November 15. However, if in the same
waterbody, the temperature threshold for spawning was triggered for an
earlier spawner on October 1, and its early life stage lasted 60 days,
then the ELS-absent provision could begin no earlier than December 1.
Hence when using temperature thresholds a State or Tribe needs to
consider both expected spawning, as well as the expected duration of
early life stages of fish. Safety factors are also appropriate where a
State or Tribe is less confident in its data for a particular site or
where there might be late spawning populations.
8. Can a State or Tribe apply the ELS-absent provision to an underlying
site-specific ammonia criterion?
Applying the ELS-absent provision to a site-specific criterion
depends on the procedure used for determining the site-specific
criterion. At sites where the Water-Effect Ratio (WER) procedure is
used, the WER would apply to both ELS-absent and ELS-present criteria
values. (However, it has been EPA's experience that the WER procedure
has yielded ratios close to 1.0 for ammonia.) At sites where the
Recalculation or Resident Species procedure is used, a State or Tribe
should consider the effects of having eliminated species from the data
set before applying the ELS-absent provision. In many instances, site-
specific criteria are developed for small tributary streams and
headwater streams with lower species diversity and fewer game fish
species. States and Tribes considering the ELS-absent provision must
protect early life stages of all fish species, not just species
considered to be of value to a fishery. Because the Recalculation
Procedure involves a re-derivation of the criterion, and not merely a
factor adjustment of the criterion, a re-derivation of a ELS-absent
criteria table should follow procedures similar to those used in the
1999 Update.

C. State and Tribal Adoption of Ammonia Criteria

EPA recommends that States and Tribes adopt numeric ammonia
criteria applicable at all times of the year for all waters designated
for the protection of aquatic life or for waters whose existing uses
include aquatic life. Numeric criteria may be adopted based on EPA's
ambient water quality criteria for ammonia, such criteria modified to
reflect site-specific conditions, or other scientifically defensible
methods. 40 CFR 131.11(b)(1). States and Tribes should adopt narrative
criteria where numeric criteria cannot be established or to supplement
numeric criteria. 40 CFR 131.11(b)(2). Because EPA has issued section
304(a) criteria for ammonia, numeric criteria for ammonia can be
established. Ammonia is a pollutant that is routinely found in the
wastewater effluent of publicly-owned treatment works and landfill
leachate, as well as run-off from agricultural fields where commercial
fertilizers and animal manure are applied. Ammonia is frequently
identified as a pollutant causing or contributing to water quality
impairment when states assemble their lists of impaired surface waters
under section 303(d). Because ammonia has known toxic effects to
aquatic life, as is demonstrated in EPA's 1999 Update of Ambient Water
Quality Criteria for Ammonia, the Office of Water finds that control of
ammonia discharges is necessary to protect aquatic life uses of surface
water across the United States. Numeric criteria for ammonia are much
easier to implement in NPDES permits than are narrative criteria
because they form a concrete basis for calculating the need for and the
substance of any needed effluent limitations. In the TMDL program, such
criteria serve as a definitive benchmark for determining impairment of
waters for listing purposes and then as a concrete starting point for
establishing TMDL's, wasteload allocations for point sources and load
allocations for nonpoint sources. Further, because water quality
criteria are commonly implemented through regulatory mechanisms such as
TMDLs and NPDES permits, State and Tribal adoption of numeric criteria
does not have a direct impact on any given discharger. In the case of
NPDES permits, a water quality based effluent limit would apply to a
given discharger only if the discharge has the reasonable potential to
cause an exceedance of a water quality criterion. In addition under
section 303(d) of the CWA, waterbodies would be listed and TMDLs
established only where the ambient concentrations in the water exceed
the ammonia criteria.
The adoption of numeric criteria for ammonia will be a priority for
the triennial reviews of water quality standards that will occur in
FY2001-2003. Beginning with FY2001, EPA Headquarters and Regional
Offices will develop management agreements with the states and tribes
that will include commitments to have states and tribes adopt numeric
criteria for ammonia. Where a state does not amend its water quality
standards to include water quality criteria for ammonia that will
ensure protection of designated uses, EPA's Office of Water will
recommend to the Administrator that she act under Section 303(c) of the
Clean Water Act to promulgate numeric criteria with the goal of
assuring that protective criteria for ammonia apply in all states not
later than 2004.

[[Page 71980]]

VI. Threatened or Endangered Species

Because ambient 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 that
States and Tribes develop more stringent, site-specific modifications
of the criteria as necessary to protect threatened and endangered
species.
In adopting ammonia criteria for specific water bodies, States and
Tribes may need to develop more stringent, 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. More stringent, site-specific modifications may be calculated to
protect a listed endangered or threatened species by using the Species
Mean Acute Value (SMAC) and Species Mean Chronic Value (SMCV).
Resetting the CMC: 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.) Resetting the CCC: If the 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. If the Species Mean Chronic Value is not available, then the CCC
can be reset by dividing the Species Mean Acute Value by the Acute to
Chronic Ratio (ACR) in accord with EPA's ``Guidelines for Deriving
Numerical National Water Quality Criteria for the Protection of Aquatic
Organisms and their Uses (1985),'' for deriving a CCC for commercially
and recreationally important species; or,
2. More stringent, site-specific modifications may be calculated to
protect a listed endangered or threatened species by 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).

Dated: December 15, 1999.
Dana D. Minerva,
Acting Assistant Administrator for Water.
[FR Doc. 99-33152 Filed 12-21-99; 8:45 am]
BILLING CODE 6560-50-U

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