[Federal Register Volume 64, Number 245 (Wednesday, December 22, 1999)]
[Notices]
[Pages 71974-71980]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 99-33152]



[[Page 71973]]

_______________________________________________________________________

Part VI





Environmental Protection Agency





_______________________________________________________________________



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

  Federal Register / Vol. 64, No. 245 / Wednesday, December 22, 1999 / 
Notices  

[[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: 
[email protected].
    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; 
[email protected].

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 
NH3, and ionized NH+4, 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 (LTAa) is determined from 
the acute wasteload allocation (WLAa) using the equation:
[GRAPHIC] [TIFF OMITTED] TN22DE99.012

The chronic long term average (LTAc) is determined from the 
chronic wasteload allocation (WLAc) using the equation:
[GRAPHIC] [TIFF OMITTED] TN22DE99.013

A comparison of the LTAa and LTAc is then 
performed and the minimum value is selected (LTAMIN). The 
maximum daily limit (MDL) is then calculated from the LTAMIN 
using the equation:
[GRAPHIC] [TIFF OMITTED] TN22DE99.014

The average monthly limit (AML) is calculated from the 
LTAMIN 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 LTAc (i.e., LTAMIN = LTAc), 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 WLAc.
    Since the 1999 Update recommends a 30-day averaging period for 
deriving the CCC, the equation for determining the LTAc 
should be modified as follows:
[GRAPHIC] [TIFF OMITTED] TN22DE99.016

    The comparison of the LTAa and LTAc is then 
performed in the same manner and the MDL and AML are calculated from 
the LTAMIN.
    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