in footnote a of Table B-1 as an annual geometric mean. EPA is
finalizing the proposed frequency component as a no-more-than-one-in-
three-years excursion frequency for the annual geometric mean criteria
for streams. These duration and frequency components of the criteria
are consistent with the data set used to derive these criteria, which
applied distributional statistics to measures of annual geometric mean
values from multiple years of record. EPA has determined that this
frequency of excursions will not result in unacceptable effects on
aquatic life as it will allow the stream ecosystem enough time to
recover from occasionally elevated levels of nitrogen/phosphorus in the
stream.103 104 105 These selected duration and frequency
components recognize that hydrological variability (e.g., high and low
flows) will produce variability in nitrogen and phosphorus
concentrations, and that individual measurements may at times be
greater than the criteria magnitude concentrations without causing
unacceptable effects to aquatic organisms and their uses. Furthermore,
the frequency and duration components balance the representation of
underlying data and analyses based on the central tendency of many
years of data with the need to exercise some caution to ensure that
streams have sufficient time to process individual years of elevated
nitrogen and phosphorus levels and

avoid the possibility of cumulative and chronic effects (i.e., the no-
more-than-one-in-three-year component). More information on this
specific topic is provided in EPA's Final Rule TSD for Florida's Inland
Waters, Chapter 1: Methodology for Deriving U.S. EPA's Criteria for
Streams located in the record for this final rule.
---------------------------------------------------------------------------

    \103\ USEPA. 1985. Guidelines for Deriving Numeric National
Water Quality Criteria for the Protection of Aquatic Organisms and
Their Uses. EPA PB85-227049. U.S. Environmental Protection Agency,
Office of Research and Development, Environmental Research
Laboratories.
    \104\ Hutchens, J. J., K. Chung, and J. B. Wallace. 1998.
Temporal variability of stream macroinvertebrate abundance and
biomass following pesticide disturbance. Journal of the North
American Benthological Society 17:518-534.
    \105\ Wallace, J.B. D. S.Vogel, and T.F. Cuffney. 1986. Recovery
of a headwater stream from an insecticide induced community
disturbance. Journal of North American Benthological Society 5: 115-
l 26.
---------------------------------------------------------------------------

d. Reference Condition Approach
    In deriving the final criteria for streams, EPA has relied on a
reference condition approach, which has been well documented, peer
reviewed, and developed in a number of different
contexts.106 107 108 109 110 In the case of Florida, this
approach is supported by a substantial Florida-specific database of
high quality information, sound scientific analysis and extensive
technical evaluation.
---------------------------------------------------------------------------

    \106\ USEPA. 2000a. Nutrient Criteria Technical Guidance Manual:
Lakes and Reservoirs. EPA-822-B-00-001. U.S. Environmental
Protection Agency, Office of Water, Washington, DC.
    \107\ USEPA. 2000b. Nutrient Criteria Technical Guidance Manual:
Rivers and Streams. EPA-822-B-00-002. U.S. Environmental Protection
Agency, Office of Water, Washington, DC.
    \108\ Stoddard, J. L., D. P. Larsen, C. P. Hawkins, R. K.
Johnson, and R. H. Norris. 2006. Setting expectations for the
ecological condition of streams: the concept of reference condition.
Ecological Applications 16:1267-1276.
    \109\ Herlihy, A. T., S. G. Paulsen, J. Van Sickle, J. L.
Stoddard, C. P. Hawkins, L. L. Yuan. 2008. Striving for consistency
in a national assessment: the challenges of applying a reference-
condition approach at a continental scale. Journal of the North
American Benthological Society 27:860-877.
    \110\ U.S. EPA. 2001. Nutrient Criteria Technical Manual:
Estuarine and Coastal Marine Waters. Office of Water, Washington,
DC. EPA-822-B-01-003.
---------------------------------------------------------------------------

    EPA received comments regarding the scientific defensibility of the
reference condition approach, using either the benchmark sites or the
SCI sites. Many commenters observed that such approaches do not
mechanistically link biological effects to nitrogen/phosphorus levels
and therefore assert that EPA cannot scientifically justify numeric
criteria without an observed biological effect. EPA views the reference
condition approach as scientifically appropriate to derive the
necessary numeric criteria in Florida streams. Reference conditions
provide the appropriate benchmark against which to determine the
nitrogen and phosphorus concentrations present when the designated use
is being met. When the natural background concentrations of specific
parameters can be defined by identifying reference conditions at
anthropogenically-undisturbed sites, then the concentrations at these
sites can be considered as sufficient to support the aquatic life
expected to occur naturally at that site.\111\ Also, setting criteria
based on the conditions observed in reference condition sites reflects
both the stated goal of the Clean Water Act and EPA's National Nutrient
Strategy that calls for States, including Florida, to take protective
and preventative steps in managing nitrogen/phosphorus pollution to
maintain the chemical, physical and biological integrity of the
Nation's waters before adverse biological and/or ecological effects are
observed.\112\
---------------------------------------------------------------------------

    \111\ Davies, T.T., USEPA. 1997, November 5. Memorandum to Water
Management Division Directors, Regions 1-10, and State and Tribal
Water Quality Management Program Directors on Establishing Site
Specific Aquatic Life Criteria Equal to Natural Background.
    \112\ USEPA. 1998. National Strategy for the Development of
Regional Nutrient Criteria. EPA 822-R-98-002. U.S. Environmental
Protection Agency, Office of Water, Washington, DC; Grubbs, G.,
USEPA. 2001, November 14. Memorandum to Directors of State Water
Programs, Directors of Great Water Body Programs, Directors of
Authorized Tribal Water Quality Standards Programs and State and
Interstate Water Pollution Control Administrators on Development and
Adoption of Nutrient Criteria into Water Quality Standards.;
Grumbles, B.H., USEPA. 2007, May 25.Memorandum to Directors of State
Water Programs, Directors of Great Water Body Programs, Directors of
Authorized Tribal Water Quality Standards Programs and State and
Interstate Water Pollution Control Administrators on Nutrient
Pollution and Numeric Water Quality Standards.
---------------------------------------------------------------------------

    The effects of TN and TP on an aquatic ecosystem are well
understood and documented. There is a substantial and compelling
scientific basis for the conclusion that excess TN and TP will have
adverse effects on
streams113 114 115 116 117 118 119 120 121 122 123 124 125 126 127
. As discussed in Section II above, excess nitrogen/phosphorus in
streams, like other aquatic ecosystems, increase vegetative growth
(plants and algae), and change the assemblage of plant and algal
species present in the system. These changes can affect the organisms
that are consumers of algae and plants by altering the balance of food
resources available to different trophic levels. For example, excess
nitrogen/phosphorus promotes the growth of opportunistic and short-
lived plant species that die quickly leaving more dead vegetative
material available for consumption by lower tropic levels.
Additionally, excess nitrogen/phosphorus can promote the growth of less
palatable nuisance algae species that results in less food available
for filter feeders. These changes can also alter the habitat structure
by covering the stream or river bed with periphyton (attached algae)
rather than submerged aquatic plants, or clogging the water column with
phytoplankton (floating algae). In addition, excess nitrogen/phosphorus
can lead to the production of algal toxins that can be toxic to fish,
invertebrates, and humans. Chemical characteristics of the water, such
as pH and concentrations of dissolved oxygen (DO), can also be affected
by excess nitrogen/phosphorus leading to low DO conditions and hypoxia.
Each of these changes can, in turn, lead to other changes in the stream
community and, ultimately, to changes in the stream ecology that
supports the overall function of the linked aquatic ecosystem.
---------------------------------------------------------------------------

    \113\ Biggs, B.J.F. 2000. Eutrophication of streams and rivers:
dissolved nutrient-chlorophyll relationships for benthic algae.
Journal of the North American Benthological Society 19:17-31
    \114\ Bothwell, M.L. 1985. Phosphorus limitation of lotic
periphyton growth rates: an intersite comparison using continuous-
flow troughs (Thompson River system, British Columbia). Limnology
and Oceanography 30:527-542
    \115\ Bourassa, N., and A. Cattaneo. 1998. Control of periphyton
biomass in Laurentian streams (Quebec). Journal of the North
American Benthological Society 17:420-429
    \116\ Bowling, L.C., and P.D. Baker. 1996. Major cyanobacterial
bloom in the Barwon-Darling River, Australia, in 1991, and
underlying limnological conditions. Marine and Freshwater Research
47: 643-657
    \117\ Cross, W. F., J. B. Wallace, A. D. Rosemond, and S. L.
Eggert. 2006. Whole-system nutrient enrichment increases secondary
production in a detritus-based ecosystem. Ecology 87: 1556-1565
    \118\ Dodds, W.K., and D.A. Gudder. 1992. The ecology of
Cladophora. Journal of Phycology 28:415-427
    \119\ Elwood, J.W., J.D. Newbold, A.F. Trimble, and R.W. Stark.
1981. The limiting role of phosphorus in a woodland stream
ecosystem: effects of P enrichment on leaf decomposition and primary
producers. Ecology 62:146-158
    \120\ Francoeur, S.N. 2001. Meta-analysis of lotic nutrient
amendment experiments: detecting and quantifying subtle responses.
Journal of the North American Benthological Society 20: 358-368
    \121\ Moss, B., I. Hooker, H. Balls, and K. Manson. 1989.
Phytoplankton distribution in a temperate floodplain lake and river
system. I. Hydrology, nutrient sources and phytoplankton biomass.
Journal of Plankton Research 11: 813-835
    \122\ Mulholland, P.J. and J.R. Webster. 2010. Nutrient dynamics
in streams and the role of J-NABS. Journal of the North American
Benthological Society 29: 100-117
    \123\ Peterson, B.J., J.E. Hobbie, A.E. Hershey, M.A. Lock, T.E.
Ford, J.R. Vestal, V.L. McKinley, M.A.J. Hullar, M.C. Miller, R.M.
Ventullo, and G. S. Volk. 1985. Transformation of a tundra river
from heterotrophy to autotrophy by addition of phosphorus. Science
229:1383-1386
    \124\ Rosemond, A. D., P. J. Mulholland, and J. W. Elwood. 1993.
Top-down and bottom-up control of stream periphyton: Effects of
nutrients and herbivores. Ecology 74: 1264-1280
    \125\ Rosemond, A. D., C. M. Pringle, A. Ramirez, and M.J. Paul.
2001. A test of top-down and bottom-up control in a detritus-based
food web. Ecology 82: 2279-2293
    \126\ Rosemond, A. D., C. M. Pringle, A. Ramirez, M.J. Paul, and
J. L. Meyer. 2002. Landscape variation in phosphorus concentration
and effects on detritus-based tropical streams. Limnology and
Oceanography 47: 278-289.
    \127\ Slavik, K., B. J. Peterson, L. A. Deegan, W. B. Bowden, A.
E. Hershey, J. E. Hobbie. 2004. Long-term responses of the Kuparuk
River ecosystem to phosphorus fertilization. Ecology 85: 939-954.

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

C. Numeric Criteria for the State of Florida's Lakes

(1) Final Rule
    EPA is promulgating numeric criteria for chlorophyll a, TN and TP
in three classes of Florida's lakes, classified as Class I or III
waters under Florida law (Section 62-302.400, F.A.C.):

                              Table C-17--EPA's Numeric Criteria for Florida Lakes
----------------------------------------------------------------------------------------------------------------
                                                          Chl-a (mg/L) \b\
             Lake color \a\ and alkalinity                       *              TN (mg/L)          TP (mg/L)
----------------------------------------------------------------------------------------------------------------
Colored Lakes \c\......................................             0.020               1.27               0.05
                                                                                [1.27-2.23]        [0.05-0.16]
Clear Lakes, High Alkalinity \d\.......................             0.020               1.05               0.03
                                                                                [1.05-1.91]        [0.03-0.09]
Clear Lakes, Low Alkalinity \e\........................             0.006               0.51               0.01
                                                                                [0.51-0.93]        [0.01-0.03]
----------------------------------------------------------------------------------------------------------------
\a\ Platinum Cobalt Units (PCU) assessed as true color free from turbidity.
\b\ Chlorophyll a is defined as corrected chlorophyll, or the concentration of chlorophyll a remaining after the
  chlorophyll degradation product, phaeophytin a, has been subtracted from the uncorrected chlorophyll a
  measurement.
\c\ Long-term Color > 40 Platinum Cobalt Units (PCU).
\d\ Long-term Color <= 40 PCU and Alkalinity > 20 mg/L CaCO3.
\e\ Long-term Color <= 40 PCU and Alkalinity <= 20 mg/L CaCO3.
* For a given waterbody, the annual geometric mean of chlorophyll a, TN or TP concentrations shall not exceed
  the applicable criterion concentration more than once in a three-year period.

    For each class of water defined by color and alkalinity, the
applicable criteria are the values in bold for chlorophyll a, TN and
TP. The criteria framework provides flexibility for FDEP to derive
lake-specific, modified TN and TP criteria if the annual geometric mean
chlorophyll a concentration is less than the criterion for an
individual lake in each of the three immediately preceding years. In
such a case, the corresponding criteria for TN and/or TP may be
modified to reflect maintenance of ambient conditions within the range
specified in the parenthetical below each baseline TN and TP criteria
printed in bold in Table C-1 above. Modified criteria for TN and/or TP
must be based on data from at least the immediately preceding three
years \128\ in a particular lake. Modified TN and/or TP criteria may
not be greater than the higher value specified in the range. Modified
TN and/or TP criteria for a lake also may not be above criteria
applicable to streams to which a lake discharges in order to ensure the
attainment and maintenance of downstream water quality standards.
---------------------------------------------------------------------------

    \128\ The previous three years of data are required as a basis
for modifying TN and TP criteria and must meet FDEP's data quality
assurance objectives. Additional historical data may be used to
augment the three years of data characterizing the lake's annual and
inter-annual variability. Only historical data containing data for
all three parameters can be used and the data must meet FDEP's data
quality assurance objectives.
---------------------------------------------------------------------------

    Utilization of the range flexibility in the numeric lake criteria
in this final rule requires that the ambient calculation for modified
TN and TP criteria be based on: (1) The immediately preceding three-
year record of observation for each parameter,\129\ (2) representative
sampling during each year (at least one sample in May-September and at
least one sample in October-April), and (3) a minimum of 4 samples from
each year. Requiring at least three years of data accounts for year-to-
year hydrological variability, ensures longer-term stable conditions,
and appropriately accounts for anomalous conditions in any given year
that could lead to erroneous conclusions regarding the true
relationship between nitrogen/phosphorus and chlorophyll a levels in a
lake. Representative samples from each year minimize the effects of
seasonal variations in nitrogen/phosphorus and chlorophyll a
concentrations. Finally, the minimum sample size of 4 samples per year
allows estimates of reliable geometric means while still maintaining a
representative sample of lakes. The State shall notify EPA Region 4 and
provide the supporting record within 30 days of determination of
modified lake criteria.
---------------------------------------------------------------------------

    \129\ As noted above, if more than three years of data are
available for each parameter, then more data can be used.
---------------------------------------------------------------------------

    To ensure attainment of applicable downstream lake criteria, this
final rule provides a tiered approach for adjusting instream criteria
presented in section III.B.(1) above for those streams that flow into
lakes.\130\ Where site-specific data on lake characteristics are
available, the final rule provides a modeling approach for the
calculation of downstream lake protection values that relies upon the
use of the BATHTUB model.\131\ In circumstances where sufficient site-
specific lake data are readily available and either EPA or FDEP
determine that another scientifically defensible model is more
appropriate (e.g., the Water Quality Analysis Simulation Program, or
WASP), the modeling approach accommodates use of a scientifically
defensible alternative. In the absence of models, other approaches for
ensuring protection of downstream lakes are provided and described
further below.
---------------------------------------------------------------------------

    \130\ Approximately 30% of Florida lakes are fed by streams to
which this DPV analysis would apply (Schiffer, Donna M. 1998.
Hydrology of Central Florida Lakes--A Primer. U.S. Geological Survey
in cooperation with SJWMD and SFWMD: Circular 1137).
    \131\ Kennedy, R.H. 1995. Application of the BATHTUB model to
Selected Southeastern Reservoirs. Technical Report EL-95-14. U.S.
Army Engineer Waterways Experiment Station, Vicksburg, MS.; Walker,
W.W., 1985. Empirical Methods for Predicting Eutrophication in
Impoundments; Report 3, Phase II: Model Refinements. Technical
Report E-81-9. U.S. Army Engineer Waterways Experiment Station,
Vicksburg, MS.; Walker, W.W., 1987. Empirical Methods for Predicting
Eutrophication in Impoundments; Report 4, Phase III: Applications
Manual. Technical Report E-81-9. U.S. Army Engineer Waterways
Experiment Station, Vicksburg, MS.
---------------------------------------------------------------------------

(2) Background and Analysis
(a) Methodology for Lake Classification
    In the January 2010 proposal, EPA used color and alkalinity to
classify Florida's lakes based on substantial data demonstrating that
these characteristics influence the response of lakes to increased
nitrogen/phosphorus and the expected background chlorophyll a
concentration. Many of Florida's lakes contain dissolved organic matter
leached from surface vegetation that

colors the water. More color in a lake limits light penetration within
the water column, which in turn limits algal growth. Thus, in lakes
with colored water, higher levels of nitrogen/phosphorus may occur
without exceeding the chlorophyll a criteria concentrations. EPA
evaluated relationships among TN, TP, and chlorophyll a concentration
data, and found that lake color influenced these relationships. More
specifically, EPA found the correlations between nitrogen/phosphorus
and chlorophyll a concentrations to be stronger and less variable when
lakes were categorized into two distinct groups based on a color
threshold of 40 PCU, with clear lakes demonstrating more algal growth
with increased nitrogen/phosphorus, as would be predicted by the
increased light penetration. This threshold is consistent with the
distinction between clear and colored lakes long observed in
Florida.\132\
---------------------------------------------------------------------------

    \132\ Shannon, E.E., and P.L. Brezonik. 1972. Limnological
characteristics of north and central Florida lakes. Limnology and
Oceanography 17(1): 97-110.
---------------------------------------------------------------------------

    Within the clear lakes category, color is not the dominant
controlling factor in algal growth. For these clear lakes, EPA proposed
the use of alkalinity as an additional distinguishing characteristic.
Alkalinity and pH increase when water is in contact with carbonate
rocks, such as limestone, or limestone-derived soil in the State of
Florida. Limestone is also a natural source of phosphorus, and thus, in
Florida, lakes that are higher in alkalinity are often associated with
naturally elevated TP levels. The alkalinity (measured as
CaCO3 concentration) of Florida clear lakes ranges from zero
to over 200 mg/L. EPA proposed classifying clear Florida lakes into
acidic and alkaline classes based on an alkalinity threshold of 50 mg/L
CaCO3, and solicited comment on whether a 20 mg/L
CaCO3 threshold would be more appropriate. EPA received
comments noting that that the lower alkalinity classification threshold
would be more representative of naturally oligotrophic conditions by
creating a class of lakes with very low alkalinity and correspondingly
low chlorophyll a concentrations. After reviewing available lake data,
EPA found that clear lakes below 20 mg/L CaCO3 were more
similar to one another in terms of naturally expected chlorophyll a,
TN, and TP concentrations than clear lakes below 50 mg/L
CaCO3. Thus, EPA concluded that an alkalinity threshold of
20 mg/L CaCO3 was an appropriate threshold for classifying
clear lakes and EPA is finalizing the lower alkalinity threshold in
this rule. More information on this specific topic is provided in EPA's
Finals TSD for Florida's Inland Waters, Chapter 2: Methodology for
Deriving U.S. EPA's Criteria for Lakes located in the record for this
final rule.
    EPA also proposed the use of specific conductance as a surrogate
for alkalinity. EPA received comments that conductivity was not an
accurate surrogate measure for alkalinity. EPA evaluated the
association between specific conductivity and alkalinity and concluded
that alkalinity is a preferred parameter for lake classification
because it is a more direct measure of the presence of carbonate rocks,
such as limestone that are associated with natural elevated phosphorus
levels. Changes in specific conductivity can be attributed to changes
in alkalinity, but in many cases may be caused by increases in the
concentrations of other compounds that originate from human activities.
Thus, EPA has concluded that alkalinity is a more reliable indicator
for characterizing natural background conditions for Florida lakes.
    A number of comments suggested EPA consider a system that
delineates 47 lake regions and a system that classifies lakes as a
continuous function of both alkalinity and color. As discussed in more
detail in the TSD supporting this final rule, EPA evaluated each of
these alternative classification approaches, and found that they did
not improve the predictive accuracy of biological responses to
nitrogen/phosphorus over EPA's classification, nor result in a
practical system that can be implemented by FDEP. For example, in the
case of the 47 lake region approach, insufficient data are available to
derive numeric criteria across all of the 47 regions and in the case of
the continuous function approach there is a reliance on an assumption
that TN and TP are always co-limiting that is not always true.\133\
---------------------------------------------------------------------------

    \133\ Guildford, S. J. and R. E. Hecky. 2000. Total nitrogen,
total phosphorus, and nutrient limitation in lakes and oceans: Is
there a common relationship? Limnology and Oceanography 45: 1213-
1223.
---------------------------------------------------------------------------

    A number of commenters suggested that lake-specific criteria would
be more appropriate than the three broad classes that EPA proposed. The
substantial data available in the record for this final rule supports
the conclusion that many of Florida's lakes share similar physical,
chemical, and geological characteristics, which in turn justifies,
based on sound scientific evidence, broad classification of Florida
lakes. EPA concluded, based on the substantial data and associated
analysis explained above, that color and alkalinity are primary
distinguishing factors in Florida lakes with respect to nitrogen/
phosphorus dynamics and the associated biological response. With
respect to consideration of site-specific information that goes beyond
the detailed site-specific sampling and monitoring analysis already
discussed,\134\ the numeric lake criteria in this final rule are
established within a flexible regulatory framework that allows
adjustment of TN, TP, and/or chlorophyll a criteria based on additional
lake-specific data. This framework provides an opportunity to derive
lake-specific criteria similar to the manner suggested in public
comment, where lake-specific data and information are available, while
ensuring that numeric criteria are in place to protect all of Florida's
lakes. Further site-specific flexibility is provided in this final rule
through the derivation of alternative criteria by a Federal Site
Specific Adjusted Criteria (SSAC) process discussed in more detail
below in Section V.C.
---------------------------------------------------------------------------

    \134\ Technical Support Document for EPA's Final Rule for
Numeric Nutrient Criteria for Nitrogen/Phosphorus Pollution in
Florida's Inland Surface Fresh Waters.
---------------------------------------------------------------------------

    In this final rule, EPA is dividing Florida's lakes into three
classes: (1) Colored Lakes >40 Platinum Cobalt Units (PCU), (2) Clear,
High Alkalinity Lakes (<=40 PCU with alkalinity >20 mg/L calcium
carbonate (CaCO3)), and (3) Clear, Low Alkalinity Lakes
(<=40 PCU with alkalinity <=20 mg/L CaCO3). These two
parameters, color and alkalinity, both affect lake productivity and
plant biomass, as measured by chlorophyll a. For more information
regarding these classes, please refer to EPA's Final Rule TSD for
Florida's Inland Waters, Chapter 2: Methodology for Deriving U.S. EPA's
Criteria for Lakes.
(b) Methodology for Chlorophyll  a Criteria
    EPA proposed the use of chlorophyll a concentration as an indicator
of a healthy biological condition, supportive of natural balanced
populations of aquatic flora and fauna in each of the classes of
Florida's lakes. Excess algal growth is associated with degradation in
aquatic life, and chlorophyll a levels are a measure of algal growth.
To derive the proposed chlorophyll a concentrations that would be
protective of natural balanced populations of aquatic flora and fauna
in Florida's lakes, EPA utilized the expected trophic status of the
lake, based on internationally accepted lake use classifications.\135\
---------------------------------------------------------------------------

    \135\ OECD. 1982. Eutrophication of Waters. Monitoring,
Assessment and Control. Organisation for Economic Development and
Co-Operation, Paris, France.

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

    As discussed in more detail at proposal, lakes can be classified
into one of three trophic State categories (i.e., oligotrophic,
mesotrophic, eutrophic).\136\ EPA concluded at proposal that healthy
colored lakes and clear, high alkalinity lakes should maintain a
mesotrophic status, because they receive significant natural nitrogen/
phosphorus input and still support a healthy diversity of aquatic life
in warm, productive climates such as Florida. For these two categories
of lakes, EPA proposed a chlorophyll a criterion of 0.020 mg/L to
support balanced natural populations of aquatic life flora and fauna.
At concentrations above 0.020 mg/L chlorophyll a, the trophic status of
the lake is more likely to become eutrophic and the additional
chlorophyll a will reduce water clarity, negatively affecting native
submerged macrophytes, and the invertebrate and fish communities that
depend on them. Commenters suggested that this threshold is overly
protective of naturally eutrophic lakes in the State. For those lakes
that may currently be naturally eutrophic, this final rule contains a
formal SSAC process to revise these criteria for this unique type of
lake. For more information on the SSAC process, please refer to Section
V.C of this final rule.
---------------------------------------------------------------------------

    \136\ Trophic state describes the nitrogen/phosphorus levels and
algal state of an aquatic system: Oligotrophic (low nitrogen/
phosphorus and algal productivity), mesotrophic (moderate nitrogen/
phosphorus and algal productivity), and eutrophic (high nitrogen/
phosphorus and algal productivity).
---------------------------------------------------------------------------

    In contrast, clear, low alkalinity lakes in Florida do not receive
natural nitrogen/phosphorus input from underlying geological formations
in the watershed and thus, they support less algal growth and have
lower chlorophyll a levels than colored or clear, high alkalinity
lakes. EPA concluded at proposal that these lakes should maintain an
oligotrophic status to support balanced natural populations of aquatic
flora and fauna. EPA proposed a chlorophyll a criterion of 0.006 mg/L
in clear, low alkalinity lakes to support balanced natural populations
of aquatic life flora and fauna. At concentrations above 0.006 mg/L
chlorophyll a, the trophic status of the lake is more likely to become
mesotrophic and the additional chlorophyll a will reduce water clarity,
negatively affecting native submerged macrophytes, and the invertebrate
and fish communities that depend on them. Commenters suggested that
this chlorophyll a concentration may not be appropriate for clear lakes
with alkalinity less than 50 mg/L. As explained in more detail above,
in this final rule EPA concluded that 20 mg/L is an appropriate
threshold between low and high alkalinity lakes. Thus, lakes with
alkalinity greater than 20 mg/L will have a chlorophyll a criterion
that is applicable to clear, high alkalinity lakes. Based on the
revision of the alkalinity threshold to 20 mg/L, EPA reviewed the
available chlorophyll a data for clear, low alkalinity lakes and found
that the majority of lakes have chlorophyll a concentrations less than
0.006 mg/L reflective of oligotrophic conditions which leads EPA to
conclude that this chlorophyll a concentration will serve to maintain
the trophic status of these lakes.
    In this final rule, EPA is promulgating chlorophyll a criteria of
0.020 mg/L in colored lakes and clear, high alkalinity lakes and a
chlorophyll a criterion of 0.006 mg/L in clear, low alkalinity lakes as
an indicator of a healthy biological condition, supportive of natural
balanced populations of aquatic flora and fauna in these classes of
Florida's lakes. For more information regarding these chlorophyll a
criteria, please refer to EPA's Final Rule TSD for Florida's Inland
Waters, Chapter 2: Methodology for Deriving U.S. EPA's Criteria for
Lakes.
(c) Methodology for Total Nitrogen (TN) and Total Phosphorus (TP)
Criteria in Lakes
    EPA proposed TN and TP criteria for each of the classes of lakes
described in Section III.C(2)(a) based on the response of chlorophyll a
to increases in TN and TP for clear and colored lakes in Florida. These
responses were quantitatively estimated with linear regressions. Each
data point used in estimating the statistical relationships was the
geometric mean of samples taken over the course of a year in a
particular Florida lake. Statistical analyses of these relationships
showed that the chlorophyll a responses to changes in TN and TP
differed for colored versus clear lakes, as would be expected, because
color blocks light penetration in the water column and limits algal
growth. These analyses also showed that chlorophyll a responds to
changes in TN and TP in high and low alkalinity clear lakes similarly,
as would be expected, because alkalinity does not affect light
penetration. These relationships were used to derive TN and TP criteria
that would maintain chlorophyll a concentrations at desired levels
known to be supportive of balanced natural populations of aquatic flora
and fauna as discussed above. These analyses are explained in more
detail in EPA's Final Rule TSD for Florida's Inland Waters, Chapter 2:
Methodology for Deriving U.S. EPA's Criteria for Lakes included in the
record for this final rule.
    EPA proposed baseline TN and TP criteria based on the 75th
percentile of the predicted distribution of chlorophyll a
concentrations, given a TN or TP concentration. Commenters suggested
alternative approaches for deriving TN and TP criteria, including using
either the mean predicted chlorophyll a concentration, using the 25th
percentile of the predicted distribution of chlorophyll a
concentrations, and using an additional criterion based on a higher
percentile that is associated with a different exceedance frequency.
EPA considered these alternative approaches and concluded that
calculating the TN and TP criteria as a baseline concentration with an
associated concentration range was a more flexible approach than a
single value approach manifested as the TN and TP concentration
associated with a specific chlorophyll a concentration. Thus, the
approach included in this final rule takes into account the natural
variability observed in different classes of lakes (i.e., colored or
clear) in a way that a single value approach based on the regression
line or the lower value of the 50th percentile prediction interval does
not.
    In this final rule, the TN and TP criteria are based on linear
regressions (i.e., best-fit lines) predicting the annual geometric mean
chlorophyll a concentration as a function of the annual geometric mean
TN or TP. Baseline TN and TP criteria are calculated as the point at
which the 75th percentile of the predicted distribution of chlorophyll
a concentrations from the regression relationship is equivalent to the
chlorophyll a criterion for the appropriate lake class. The range of
values in the predicted distribution of chlorophyll a concentrations
arises from small differences in the nitrogen/phosphorus-chlorophyll a
relationships across different lakes and variability in these
relationships between years in the same lake. Hence, TN and TP criteria
are based on the 75th percentile that will be protective at the
majority of lakes and in the majority of years.
    The predicted distribution of chlorophyll a concentrations for
lakes differs inherently from the distribution of TN and TP
concentrations calculated from reference sites for criteria for Florida
streams (Section III.B(2)(b)). In the case of the criteria for Florida
streams for most NWRs, benchmark sites represent a population of least-

disturbed sites and the criteria based on the 90th percentile of
nitrogen and phosphorus concentrations from these sites are selected to
characterize the upper bound of nitrogen/phosphorus concentrations that
one would expect from such sites. Criteria for Florida lakes rely on a
predictive relationship between nitrogen/phosphorus and chlorophyll a
concentrations, and the 75th percentile is selected from the
distribution of chlorophyll a concentrations predicted for specific
concentrations of TN and TP. As discussed above, basing criteria on
this percentile provides a means of accounting for variability in
chlorophyll a concentrations predicted for a given TN and TP
concentration. In short, the percentile for the streams criteria is
selected to ensure that nitrogen/phosphorus concentrations in all
streams are at least as low as those observed in reference streams,
whereas the percentile for the lakes criteria is selected such that
concentrations appropriately account for variability in the
relationships between nitrogen/phosphorus and chlorophyll a
concentrations.
(d) Duration and Frequency
    Aquatic life water quality criteria include magnitude, duration,
and frequency components. For the chlorophyll a, TN, and TP criteria
for lakes, the criterion-magnitude values, expressed as a
concentration, are provided in Table C-1 in bold. The criterion-
duration of this magnitude is specified in a footnote to this Table as
an annual geometric mean. EPA is finalizing the criterion-frequency as
a no-more-than-once-in-three-years excursion frequency of the annual
geometric mean criteria for lakes. The duration component of the
criteria is based on annual geometric means to be consistent with the
data set used to derive these criteria, which applied stressor-response
relationships based on annual geometric means for individual years at
individual lakes. These selected duration and frequency components
recognize that hydrological variability (e.g., high and low flows) will
produce variability in nitrogen and phosphorus concentrations, and that
individual measurements may at times be greater than the criterion-
magnitude concentrations without causing unacceptable effects to
aquatic organisms and their uses. Furthermore, they balance the
representation of the central tendency of the predicted relationship
between TN or TP and chlorophyll a based from many years of data with
the need to exercise some caution to ensure that lakes have sufficient
time to process individual years of elevated nitrogen and phosphorus
concentrations and avoid the possibility of cumulative and chronic
effects (i.e., the no-more-than-one-in-three-year component).
Additionally, because nitrogen/phosphorus pollution is best managed on
a watershed basis, this is the same frequency and duration used in the
final streams criteria. More information on this specific topic is
provided in EPA's Final Rule TSD for Florida's Inland Waters, Chapter
2: Methodology for Deriving U.S. EPA's Criteria for Lakes located in
the record for this final rule.
(e) Application of Lake-Specific, Ambient Condition-Based Modified TN
and TP Criteria
    EPA proposed an accompanying approach that the State could use to
adjust TN and TP criteria for a particular lake within a certain range
where sufficient data on long-term ambient chlorophyll a, TN and TP
levels are available to demonstrate that protective chlorophyll a
criterion for a specific lake will still be maintained and a balance of
natural populations of aquatic flora and fauna will be supported. This
approach allows for readily available site-specific data to be taken
into account in the expression of TN and TP criteria, while still
ensuring support of balanced natural populations of aquatic flora and
fauna by maintaining the associated chlorophyll a level at or below the
chlorophyll a criterion level. The scientific premise for the lake-
specific ambient calculation provision for modified TN and/or TP
criteria is that if ambient lake data show that a lake's chlorophyll a
levels are at or below the established criteria (i.e., magnitude) for
at least the last three years and its TN and/or TP levels are within
the lower and upper bounds, then those ambient levels of TN and TP
represent conditions that will continue to support the specified
chlorophyll a response level. The lower bound of the range is based on
the TN/TP values that correspond to the 75th percentile of the
predicted chlorophyll a distribution and the upper bound of the range
is based on the TN/TP values that correspond to the 25th percentile of
the same predicted distribution. The use of the 25th and 75th
percentiles accounts for the majority of variability that may occur
around the central tendency of the predicted relationship between TN or
TP and chlorophyll a.
    This final rule provides that FDEP must establish and document
these modified criteria in a manner that clearly recognizes their
status as the applicable criteria for a particular lake. To this end,
FDEP must submit a letter to EPA Region 4 formally documenting the use
of modified criteria as the applicable criteria for particular lakes.
This final rule allows for a one-time adjustment without a requirement
that FDEP go through a formal SSAC process. EPA believes that such
modified TN and TP criteria do not need to go through the SSAC process
because the conditions under which they are applicable are clearly
stated in this final rule and data requirements are clearly laid out so
that the outcome is clear, consistent, transparent, and reproducible.
By providing a specific process for deriving modified criteria within
the WQS rule itself, each individual outcome of this process is an
effective WQS for CWA purposes and does not need separate adoption by
FDEP or approval by EPA. For more information on the SSAC process,
please refer to Section V.C of this final rule.
    Application of the ambient calculation provision has implications
for assessment and permitting because the outcome of applying this
provision is to establish alternate numeric TN and/or TP values as the
applicable lake criteria. For accountability and tracking purposes, the
State must document the result of the ambient calculation for any given
lake. Once modified criteria are established under this approach, they
remain the applicable criteria for the long-term for purposes of
implementing the State's water quality program until they are
subsequently modified either through the Federal SSAC process or State
revision to the applicable WQS, which has been approved by EPA pursuant
to CWA section 303(c).
    This site-specific lake criteria adjustment provision is subject to
the downstream protection requirements more broadly discussed below.
Thus in a comparable manner this final rule provides that calculated TN
and/or TP values in a lake that discharges to a stream may not exceed
criteria applicable to the stream to which a lake discharges.
(f) Downstream Protection of Lakes
    In developing the proposed stream criteria, EPA also evaluated
their effectiveness for assuring the protection of downstream lake
water quality standards pursuant to the provisions of 40 CFR 130.10(b),
which requires that WQS must provide for the attainment and maintenance
of the WQS of downstream waters.\137\ EPA's criteria for

lakes are, in some cases, more stringent than the final criteria for
streams that flow into the lakes, and thus the instream criteria may
not be stringent enough to ensure protection of WQS in certain
downstream lakes. As a result, EPA proposed application of the
Vollenweider equation to ensure that the TP criteria in streams are
protective of downstream lakes, and requested comment on alternative
approaches such as the BATHTUB model and whether there should be an
allowance for use of other models that are demonstrated to be
protective and scientifically defensible.
---------------------------------------------------------------------------

    \137\ EPA will assess the effectiveness of final stream criteria
for assuring the protection of downstream estuaries in a separate
rulemaking that focuses on estuarine and coastal waters to be
proposed by November 14, 2011 and finalized by August 15, 2012.
---------------------------------------------------------------------------

    The proposed use of the Vollenweider model equation to ensure the
protection of downstream lakes requires input of two lake-specific
characteristics: the fraction of inflow due to stream flow and the
hydraulic retention time. EPA provided alternative preset values for
percent contribution from stream flow and hydraulic retention time that
could be used in those instances where lake-specific input values are
not readily available. EPA's January 2010 proposed rule discussed the
flexibility for the State to use site-specific inputs to the
Vollenweider equation for these two parameters, as long as the State
determines that such inputs are appropriate and documents the site-
specific values. Some commenters stated that the Vollenweider equation
is overly simplistic and does not include the necessary factors to
account for physical, hydrologic, chemical, and biological processes
necessary to determine protective criteria. Several commenters also
suggested the need for TN values to protect downstream lakes that are
nitrogen-limited (such as many of the lakes in the phosphorus-rich
areas of the State). Comments included a recommendation to use models
that can better represent site-specific conditions, such as BATHTUB.
    EPA's August 2010 Supplemental Notice of Data Availability and
Request for Comment requested additional comment on using the BATHTUB
model in place of the Vollenweider equation for deriving both TP and TN
criteria to protect downstream lakes, allowing the use of alternative
models under certain circumstances, and providing for an alternative
approach to protect downstream lakes when limited data are available
that would use the lake criteria themselves as criteria for upstream
waters flowing into the lake.
    In the final rule, protection of downstream lakes is accomplished
through establishment of a downstream protection value (DPV). The
applicable criteria for streams that flow into downstream lakes include
both the instream criteria for TN and TP and the DPV, which is a
concentration or loading value at the point of entry into a lake that
results in attainment of the lake criteria. EPA selected the point of
entry into the lake, also referred to as the ``pour point,'' as the
location to measure water quality because the lake responds to the
input from the pour point and all contributions from the stream network
above this point in a watershed affect the water quality at the pour
point. When a DPV is exceeded at the pour point, the waters that
collectively comprise the network of streams in the watershed above
that pour point are considered to not attain the DPV for purposes of
section 303(d) of the Clean Water Act. The State may identify these
impaired waters as a group rather than individually.
    It is appropriate to express the DPV as either a load or
concentration (load divided by flow) because both are expressions of
the amount of TN and TP that are delivered to the downstream water. In
an expression of load, the amount is expressed directly as mass per
time (e.g., pounds per year), whereas a concentration expresses the
amount in terms of the mass contained in a particular volume of water
(e.g., milligrams per liter). Either expression may be used for
assessment and source control allocation purposes. Calculating a DPV as
a load will require modeling or other technical information, such as a
TMDL, that accounts for both the volume of the receiving water and the
flow contributed through the pour point. A DPV expressed as a
concentration may be based on a model or TMDL or may reflect a TN or TP
level that corresponds to a TN, TP, or chlorophyll a concentration that
protects the lake.
    Contributions of TN and/or TP from sources in stream tributaries
upstream of the point of entry are accountable to the DPV because the
water quality in the stream tributaries must result in attainment of
the DPV at the pour point into the lake. The spatial allocation of load
within the watershed is an important accounting step to ensure that the
DPV is achieved at the point of entry into the lake. How the watershed
load is allocated may differ based on watershed characteristics and
existing sources (e.g., areas that are more susceptible to physical
loss of nitrogen; location of towns, farms, and dischargers), so long
as the DPV is met at the point of entry into the downstream lake. Where
additional information is available, watershed modeling could be used
to develop allocations that reflect hydrologic variability and other
water quality considerations. For protection of the downstream lake,
what is important is an accounting for nutrient loadings on a watershed
scale that results in meeting the DPV at the point of entry into the
downstream lake.
    The final rule provides that additional DPVs may be established in
upstream locations to represent sub-allocations of the total allowable
loading or concentration. Such sub-allocations may be useful where
there are differences in hydrological conditions and/or sources of TN
and/or TP in different parts of the watershed. The rule specifies that
DPVs apply to stream tributaries up to the point of reaching a
waterbody that is not a stream as defined in the rule (e.g., up to
reaching another lake in a ``nested'' or chain of lakes situation). The
rule also includes an option, however, to establish a DPV to account
for a larger watershed area in a modeling context. Establishing DPVs
that apply to a larger watershed may be useful to address a situation
where the water that is furthest downstream in a watershed is also the
water that is most sensitive to nitrogen/phosphorus pollution. That
situation may require a more equitable distribution, across the larger
watershed, of the load that protects the most sensitive waterbody.
    Where multiple tributaries enter a lake, the total allowable
loading to the lake may be distributed among the tributaries for
purposes of DPV calculation in any manner that results in meeting the
total allowable loading for the lake, remembering that those
tributaries are also subject to the instream protection value
established for the tributaries.
    Where sufficient data and information are available, DPVs may be
established through application of the BATHTUB model. BATHTUB applies
empirical models to morphometrically complex lakes and reservoirs. The
model performs steady-state water and nutrient balance calculations,
uses spatially segmented hydraulic networks, and accounts for advective
and diffusive transport of nutrients. When properly calibrated and
applied, BATHTUB predicts nutrient-related water quality conditions
such as TP, TN, and chlorophyll a concentrations, transparency, and
hypolimnetic oxygen depletion rates. The model can apply to a variety
of lake sizes, shapes and transport characteristics. A high degree of
flexibility is available for specifying

model segments as well as multiple influent streams. Because water
quality conditions are calculated using relationships derived from data
specific to each lake, BATHTUB accounts for differences between lakes,
such as the rate of internal loading of phosphorus from bottom
sediments. The above descriptive information is summarized from
available technical references that also describe the model and its
applications in greater detail.138 139 140 EPA believes
BATHTUB is appropriate for DPV calculations because BATHTUB can
represent a number of site-specific variables that may influence
nutrient responses and can estimate both TN and TP concentrations at
the pour points to protect the receiving lake. BATHTUB has been
previously used for lake water quality management purposes, such as the
development of TMDLs in States, including Florida. This model was
selected because it does not have extensive data requirements, yet it
provides for the capability to be calibrated based on observed site-
specific lake data and it provides for reliable estimates that will
ensure the protection of downstream lakes.
---------------------------------------------------------------------------

    \138\ Walker, W.W., 1981. Empirical Methods for Predicting
Eutrophication in Impoundments; Report 1, Phase I: Data Base
Development. Technical Report E-81-9. U.S. Army Engineer Waterways
Experiment Station, Vicksburg, MS.
    \139\ Walker, W.W., 1982. Empirical Methods for Predicting
Eutrophication in Impoundments; Report 2, Phase II: Model Testing.
Technical Report E-81-9. U.S. Army Engineer Waterways Experiment
Station, Vicksburg, MS.
    \140\ Walker, W.W., 1999. Simplified Procedures for
Eutrophication Assessment and Prediction: User Manual; Instruction
Report W-96-2. U.S. Army Corps of Engineers Waterways Experiment
Station, Vicksburg, MS.
---------------------------------------------------------------------------

    EPA's final rule also specifically authorizes FDEP or EPA to use a
model other than BATHTUB when either FDEP or EPA determines that it
would be appropriate to use another scientifically defensible modeling
approach that results in the protection of downstream lakes. While
BATHTUB is a peer-reviewed and versatile model, there are other models
that, when appropriately calibrated and applied, can offer additional
capability to address complex situations with an even greater degree of
site-specificity. Adopted and approved TMDLs may contain sufficient
information to support derivation of a DPV when the TMDL is based on
relevant data, defensible science, and accurate analysis.
    As discussed in more detail in the Agency's August 2010
Supplemental Notice of Data Availability and Request for Comment on
this issue, one example of an alternative model that FDEP or EPA might
consider using for particularly complex site-specific conditions is the
Water Quality Analysis Simulation Program (WASP) model. This model
allows users to conduct detailed simulations of water quality responses
to natural and manmade pollutant inputs. WASP is a dynamic compartment-
modeling program for aquatic systems, including both the water column
and the underlying benthos. WASP allows the user to simulate systems in
1, 2, or 3 dimensions, and a variety of pollutant types. The model can
represent time varying processes of advection, dispersion, point and
diffuse mass loading, and boundary exchange. WASP also can be linked
with hydrodynamic and sediment transport models that can provide flows,
depths, velocities, temperature, salinity and sediment fluxes. The
above summary information as well as additional technical information
may be found at http://www.epa.gov/athens/wwqtsc/html/wasp.html. Like
BATHTUB, WASP has also been previously used for lake water quality
management purposes, such as TMDLs, nationally and in the State of
Florida. This model is different from BATHTUB because it does have
extensive data requirements that allow for the capability to be finely
calibrated based on observed site-specific lake data, but is similar to
BATHTUB in that it also provides for reliable estimates that will
ensure the protection of downstream lakes.
    EPA is finalizing a provision in this section of the rule for
situations where data are not readily available to derive TN and/or TP
DPVs using BATHTUB or another scientifically defensible model. In that
situation, the rule describes how DPVs are determined where the
downstream lake is attaining the lake criteria and where the downstream
lake is either not assessed or is impaired.
    Where sufficient information is not available to derive TN and/or
TP DPVs using BATHTUB or another scientifically defensible technical
model and the lake attains the applicable criteria, the DPVs would be
the associated ambient instream levels of TN and/or TP at the point of
entry into the lake. As long as the TN and TP concentrations necessary
to support a balanced natural population of aquatic flora and fauna in
the downstream lake are maintained in the inflow from streams, this
approach will provide adequate protection of downstream lakes and would
be used as the applicable DPVs in the absence of readily available data
to support derivation of TN and TP DPVs using BATHTUB or another
scientifically defensible technical model such as WASP.
    EPA's final rule provides that when the DPV is based on the ambient
condition associated with attainment of criteria in the downstream
lake, degradation in water quality from those established levels would
be considered impairment, unless the State or EPA revises the DPV using
a modeling approach or TMDL to show that higher levels of nutrient
contribution from the tributaries would still result in attainment of
applicable lake criteria. This provision is not intended to limit
growth and/or development in the watershed, nor intended to maintain
current conditions regardless of further analysis. Rather this
provision is intended to ensure that WQS are not only restored when
found to be impaired, but are in fact maintained when found to be
attained, consistent with the goals of the Clean Water Act. Higher
levels of TN and/or TP may be allowed in such watersheds where it is
demonstrated that such higher levels will fully protect the lake's WQS.
    Where sufficient information is not available to derive TN and/or
TP DPVs using BATHTUB or another scientifically defensible technical
model and the lake does not attain the applicable TN, TP, and/or
chlorophyll a criteria or is un-assessed, lake criteria values for TN
and/or TP are to be used as the DPVs. EPA believes that this approach
is protective because the TN and TP concentrations entering the lake
are unlikely to need to be lower than the criterion concentration
necessary to be protective of the lake itself.
(g) Stressor-Response Approach
    In deriving the final criteria for lakes, EPA has relied on a
stressor-response approach which has been well documented and developed
in a number of different contexts.141 142 143 Stressor-
response approaches estimate the relationship between nitrogen/
phosphorus concentrations and a response measure that is either
directly or indirectly related to the designated use (in this case,
chlorophyll a as a measure of attaining a balanced natural population
of aquatic flora and fauna). Then, concentrations that support the

designated use can be derived from the estimated relationship. In the
case of Florida, the use of this approach is supported by a substantial
Florida-specific database of high quality information, sound scientific
analysis and technical evaluation.
---------------------------------------------------------------------------

    \141\ USEPA. 2000a. Nutrient Criteria Technical Guidance Manual:
Lakes and Reservoirs. EPA-822-B-00-001. U.S. Environmental
Protection Agency, Office of Water, Washington, DC.
    \142\ USEPA. 2000b. Nutrient Criteria Technical Guidance Manual:
Rivers and Streams. EPA-822-B-00-002. U.S. Environmental Protection
Agency, Office of Water, Washington, DC.
    \143\ USEPA. 2008. Nutrient Criteria Technical Guidance Manual:
Wetlands. EPA-822-B-08-001. U.S. Environmental Protection Agency,
Office of Water, Washington, DC.
---------------------------------------------------------------------------

    The effects of nitrogen/phosphorus pollution are manifested in
lakes in a variety of ways and are well-
documented.144 145 146 147 A common effect of nitrogen/
phosphorus pollution in lakes is the over-stimulation of algal growth
resulting in algal blooms, which can cause changes in algal and animal
assemblages due to adverse changes in important water quality
parameters necessary to support aquatic life. Algal blooms can decrease
water clarity and aesthetics, which in turn can affect the suitability
of a lake for primary (e.g., swimming) and secondary (e.g., boating)
contact recreation. Algal blooms can adversely affect drinking water
supplies by releasing toxins, interfering with disinfection processes,
or requiring additional treatment. Algal blooms can adversely affect
biological process by decreasing light availability to submerged
aquatic vegetation (which serves as habitat for aquatic life),
degrading food quality and quantity for other aquatic life, and
increasing the rate of oxygen consumption.
---------------------------------------------------------------------------

    \144\ Lee, G.F., W. Rast, R.A. Jones. 1978. Eutrophication of
water bodies: Insights for an age-old problem. Environmental Science
and Technology 12: 900-908.
    \145\ Carlson R.E. 1977. A trophic state index for lakes.
Limnology and Oceanography 22:361-369.
    \146\ Smith, V.H., G.D. Tilman, and J.C. Nekola. 1999.
Eutrophication: impacts of excess nutrient inputs on freshwater,
marine, and terrestrial ecosystems. Environmental Pollution 100:
179-196.
    \147\ Smith, V.H., S.B. Joye, and R.W. Howarth. 2006.
Eutrophication of freshwater and marine ecosystems. Limnology and
Oceanography 51:351-355.
---------------------------------------------------------------------------

D. Numeric Criterion for the State of Florida's Springs

(1) Final Rule
    EPA defines ``spring'' as a site at which ground water flows
through a natural opening in the ground onto the land surface or into a
body of surface water. This definition is drawn from the U.S.
Geological Survey, Circular 1137.\148\ This definition is not intended
to include streams that flow in a defined channel that have some
groundwater baseflow component. EPA recognized that groundwater-surface
water interactions in Florida are complex and that FDEP will need to
make site-specific determinations about whether water is subject to the
stream criteria or the springs criterion. EPA is promulgating the
numeric criterion for nitrate+nitrite for Florida's springs classified
as Class I or III waters under Florida law (Section 62-302.400,
F.A.C.):
---------------------------------------------------------------------------

    \148\ Schiffer, Donna M. 1998. Hydrology of Central Florida
Lakes--A Primer. U.S. Geological Survey in cooperation with SJWMD
and SFWMD: Circular 1137.

The applicable nitrate (NO3-) + Nitrite
(NO2-) is 0.35 mg/L as an annual geometric mean,
not to be exceeded more than once in a three-year period
(2) Background and Analysis
(a) Derivation of Nitrate + Nitrite Criterion
    In its January proposal, EPA proposed a nitrate+nitrite criterion
of 0.35 mg/L for springs and clear streams that would support balanced
natural populations of aquatic flora and fauna in springs. EPA proposed
criteria for nitrate+nitrite because one of most significant factors
causing adverse changes in spring ecosystems is the pollution of
groundwater, principally with nitrate+nitrite, resulting from human
land use changes, cultural practices, and significant population
growth.149 150
---------------------------------------------------------------------------

    \149\ Katz, B.G., H.D. Hornsby, J.F. Bohlke and M.F. Mokray.
1999. Sources and chronology of nitrate contamination in spring
water, Suwannee River Basin, Florida. Water-Resources Investigations
Report 99-4252. U.S. Geological Survey, Tallahassee, FL. Available
electronically at: http://fl.water.usgs.gov/PDF_files/wri99_4252_katz.pdf.
    \150\ Brown M.T., K. Chinners Reiss, M.J. Cohen, J.M. Evans,
P.W. Inglett, K. Sharma Inglett, K. Ramesh Reddy, T.K. Fraze, C.A.
Jacoby, E.J. Phlips, R.L. Knight, S.K. Notestein, R.G. Hamann, and
K.A. McKee. 2008. Summary and Synthesis of the Available Literature
on the Effects of Nutrients on Spring Organisms and Systems.
University of Florida, Gainesville, Florida. Available
electronically at: http://www.dep.state.fl.us/springs/reports/files/UF_SpringsNutrients_Report.pdf. Accessed October 2010.
---------------------------------------------------------------------------

    EPA based its proposed criterion on multiple lines of stressor-
response evidence, which included controlled, laboratory-scale
experimental data and analysis of field-based data. EPA's first line of
evidence is stressor-response data from controlled laboratory
experiments, which studied the growth response of algae in springs to
different concentrations of nitrate+nitrite. EPA found in its review of
comprehensive surveys 151 152 and a study \153\ of 29
Florida springs at over 150 sampling sites, conducted on behalf of FDEP
over three years, that two nuisance algal taxa, the cyanobacterium
Lyngbya wollei and the macroalgae Vaucheria sp., were the most commonly
occurring taxa. The authors of the study conducted controlled
laboratory experiments, which tested the growth response of Lyngbya
wollei and Vaucheria sp. to different doses of nitrate+nitrite. They
found that Lyngbya wollei and Vaucheria sp. growth rates increased in
response to increased doses of nitrate+nitrite and that most of their
highest growth rates were reached at and above 0.23 mg/L
nitrate+nitrite. EPA interpreted the results from these studies as
strong empirical evidence of a stressor-response relationship between
nuisance algae and nitrate+nitrite and further indicated specific
concentrations above which undesirable growth of nuisance algal may be
likely to occur.
---------------------------------------------------------------------------

    \151\ Pinowska, A., R.J. Stevenson, J.O. Sickman, A. Albertin,
and M. Anderson. 2007a. Integrated interpretation of survey for
determining nutrient thresholds for macroalgae in Florida Springs:
Macroalgal relationships to water, sediment and macroalgae
nutrients, diatom indicators and land use. Florida Department of
Environmental Protection, Tallahassee, FL.
    \152\ Stevenson, R.J., A. Pinowska, and Y.K. Wang. 2004.
Ecological Condition of Algae and Nutrients in Florida Springs.
Florida Department of Environmental Protection, Tallahassee, FL.
    \153\ Pinowska, A., R.J. Stevenson, J.O. Sickman, A. Albertin,
and M. Anderson. 2007b. Integrated interpretation of survey and
experimental approaches for determining nutrient thresholds for
macroalgae in Florida Springs: Laboratory experiments and
disturbance study. Florida Department of Environmental Protection,
Tallahassee, FL.
---------------------------------------------------------------------------

    In addition to the laboratory-based experimental evidence, EPA
reviewed information compiled by FDEP in its assessment of limits to
restore springs and protect them from excess algal
growth.154 155 The second line of evidence was based on data
collected from in-situ algal monitoring and long-term field surveys in
rivers FDEP considered to exhibit similar aquatic conditions to springs
(e.g., algal communities, water clarity, and proportion of flow coming
from a spring). EPA found additional stressor-response evidence in an
analysis \156\ based on over 200 algal samples collected from 13
different algal monitoring stations along the Suwannee, Santa Fe, and
Withlacoochee Rivers from 1990 to 1998. The analysis examined algal
growth response over a range of nitrate+nitrite concentration. Results
indicated a sharp increase in

algal abundance and biomass above 0.4 mg/L nitrate + nitrite.
---------------------------------------------------------------------------

    \154\ Gao, X. 2008. Nutrient TMDLs for the Wekiva River (WBIDs
2956, 2956A, and 2956C) and Rock Springs Run (WBID 2967). Florida
Department of Environmental Protection, Division of Water Resource
Management, Tallahassee, FL.
    \155\ Hallas, J.F. and W. Magley. 2008. Nutrient and Dissolved
Oxygen TMDL for the Suwannee River, Santa Fe River, Manatee Springs
(3422R), Fanning Springs (3422S), Branford Spring (3422J), Ruth
Spring (3422L), Troy Spring (3422T), Royal Spring (3422U), and
Falmouth Spring (3422Z). Florida Department of Environmental
Protection, Bureau of Watershed Management, Tallahassee, FL.
    \156\ Niu, X.-F. 2007. Appendix B. Change Point Analysis of the
Suwannee River Algal Data. In Gao, X. 2008. Nutrient TMDLs for the
Wekiva River (WBIDs 2956, 2956A, and 2956C) and Rock Springs Run
(WBID 2967). Florida Department of Environmental Protection,
Division of Water Resource Management, Tallahassee, FL.
---------------------------------------------------------------------------

    EPA concluded the two different lines of stressor-response evidence
point to a nitrate+nitrite concentration of 0.35 mg/L that would
prevent excess algal growth and be supportive of balanced natural
populations of aquatic flora and fauna in Florida springs. This
concentration is higher than that observed in laboratory-scale
experiments that may not be closely representative of reference spring
sites in Florida, but lower than the concentration that was associated
with changes in the balance of natural populations of aquatic flora and
fauna observed in an analysis of field data. EPA believes a
nitrate+nitrite criterion set at 0.35 mg/L represents an appropriate
and reasonable balance of the scientific evidence.
    EPA received a number of comments regarding EPA's proposed
criterion for springs, including concerns that the biological responses
observed in the field were not representative of all springs in
Florida. EPA disagrees with these commenters who suggested that the
observed effects in the field are not sufficient evidence to support
numeric criteria derivation in springs. The algal taxa, Lyngbya sp. and
Vaucheria sp., are representative taxa found in Florida springs. In
fact, Lyngbya and Vaucheria are the most commonly observed macroalgae
in Florida springs.\157\ Thus, the Agency considers the biological
responses of these representative taxa observed in the field and in
laboratory experiments to be ecologically meaningful and indicative of
an adverse biological response to elevated nitrate+nitrite
concentrations above 0.35 mg/L.
---------------------------------------------------------------------------

    \157\ Stevenson, R.J., A. Pinowska, and Y.K. Wang. 2004.
Ecological Condition of Algae and Nutrients in Florida Springs.
Florida Department of Environmental Protection, Tallahassee, FL.
---------------------------------------------------------------------------

    EPA also received comment that the proposed nitrate+nitrite
criterion was inappropriately applied to all clear streams within the
State. After considering these comments, EPA concluded that clear
streams are more appropriately addressed as part of the regionalized
reference approach that is supported by a broader range of stream
monitoring data as discussed above. Therefore, EPA has decided not to
finalize the springs nitrate+nitrite criterion in clear streams because
EPA considers the numeric criteria it is finalizing in this rule for
streams in the five NWRs, which includes clear streams, to be
adequately protective and scientifically defensible. These systems will
also be protected from excess nitrogen from groundwater by the
nitrate+nitrite criteria applicable in the springs that flow into them;
thus, additional nitrate+nitrite criteria are not needed.
    In this final rule, EPA is finalizing nitrate+nitrite criterion for
springs with a magnitude of 0.35 mg/L. For more information regarding
the springs criterion, please refer to EPA's Final Rule TSD for
Florida's Inland Waters, Chapter 3: Methodology for Deriving U.S. EPA's
Criteria for Springs located in the record for this final rule.
(b) Duration and Frequency
    EPA proposed a nitrate+nitrite criterion duration as an annual
geometric mean with a criterion frequency of not to be exceeded more
than once in three years. EPA also took comment on alternative
durations, such as a monthly geometric mean, and alternative
frequencies, such as a not to be exceeded more than 10% of the time.
EPA considered that the timescales of the algal responses in the
laboratory experiments (i.e., 21 to 28 days) might support a shorter
duration over which biological response to nitrate+nitrite could occur.
However, EPA found in its review of springs data and information that
nitrate concentrations can be variable from month to month, and this
intra-annual variability was not necessarily associated with impairment
of the designated use. Therefore, to account for intra-annual
variability, EPA chose to express the nitrate+nitrite criterion for
springs on an annual basis. Comments included a suggestion to express
the frequency component of the criterion as ``not to be exceeded during
a three year period as a three year average.'' However, EPA is
concerned that cumulative effects of exposure may manifest themselves
in shorter periods of time than three years. This is because springs
tend to be clear which provides the opportunity for fast growing
nuisance algal species to quickly utilize the excess nitrogen. When
nuisance algae species grow prolifically, they outcompete and replace
native submerged aquatic vegetation. Thus, more frequent exceedances of
the criterion-magnitude will not support a balanced natural population
of aquatic flora and fauna in springs because submerged aquatic
vegetation can be lost quickly from the effects of nitrate+nitrite
pollution, but can take many years, if not decades, to recover.\158\
For these reasons, EPA is finalizing the proposed duration and
frequency of an annual geometric mean not to be exceeded more than once
in three years.
---------------------------------------------------------------------------

    \158\ Duarte, C.M. 1995. Submerged aquatic vegetation in
relation to different nutrient regimes. Ophelia: International
Journal of Marine Biology 41: 87-112.
---------------------------------------------------------------------------

E. Applicability of Criteria When Final

(1) Final Rule
    This final rule is effective 15 months after publication in the
Federal Register, except for the Federal site-specific alternative
criteria (SSAC) provision of section 131.43(e), which is effective 60
days after publication in the Federal Register. This rule will apply in
addition to any other existing CWA-effective criteria for Class I or
Class III waters already adopted and submitted to EPA by the State (and
for those adopted and submitted to EPA after May 30, 2000, approved by
EPA). FDEP establishes its designated uses through a system of classes
and Florida waters are designated into one of several different
classes. Class III waters provide for healthy aquatic life and safe
recreational use. Class I waters include all the protection of
designated uses provided for Class III waters, and also include
protection for designated uses related to drinking water supply. See
Section 62-302.400, F.A.C. Class I and III waters, together with Class
II waters that are designated for shellfish propagation or harvesting,
comprise the set of Florida waters that are assigned designated uses
that include the goals articulated in Section 101(a)(2) of the CWA
(i.e. protection and propagation of fish, shellfish, and wildlife and
recreation in and on the water).\159\ Class II waters will be covered
under EPA's forthcoming rulemaking efforts for estuarine and coastal
waters. EPA is promulgating numeric criteria for lakes and flowing
waters, consistent with the terms of the Agency's Consent Decree, that
Florida has designated as Class I or Class III.
---------------------------------------------------------------------------

    \159\ Because FL classifications are cumulative, Class I waters
include protections for aquatic life and recreation, in addition to
protecting drinking water supply use.
---------------------------------------------------------------------------

    In terms of final rule language, EPA has removed regulatory
provisions at 40 CFR 131.43(c)(2)(iii) and 131.43(c)(4)-(6) because
these criteria (criteria for protection of downstream estuarine waters,
flowing waters in the South Florida Region, and estuaries and coastal
waters) will be included with the Agency's 2011 proposed rulemaking for
estuarine and coastal waters. For water bodies designated as Class I
and Class III predominately fresh waters, EPA's final numeric criteria
will be applicable CWA water quality criteria for purposes of
implementing CWA programs, including permitting under the NPDES
program, as well as

monitoring, assessments, and listing of impaired waters based on
applicable CWA WQS and establishment of TMDLs.
    In this final rule, the Agency has also deleted proposed regulatory
provisions at 40 CFR 131.43(d)(2)(i)-(iii) on mixing zones, design
flow, and listing impaired waters. EPA notes that the final criteria in
this rule are subject to Florida's general rules of applicability in
the same way and to the same extent as are other State-adopted and/or
Federally-promulgated criteria for Florida waters. (See 40 CFR
131.43(d)(2)). States have discretion to adopt policies generally
affecting the application and implementation of WQS. (See 40 CFR
131.13). There are many applications of criteria in Florida's water
quality programs. Therefore, EPA believes that it is not necessary for
purposes of this final rule to enumerate each of them, nor is it
necessary to restate any otherwise applicable requirements. This broad
reference to general rules of applicability provides sufficient
coverage and has been used without further elaboration in EPA's most
recent criteria promulgation applicable to State waters.\160\ The
Agency is also concerned that addressing some applications in this
final regulations and not others may create unnecessary and unintended
questions, confusion, and uncertainty about the overall application of
Florida's general rules.
---------------------------------------------------------------------------

    \160\ See 40 CFR 131.41(d)(2).
---------------------------------------------------------------------------

(2) Summary of Major Comments
    Regarding application of criteria, several commenters asked EPA to
provide more detail on how waters would be monitored, whether EPA would
use the rotating basin approach that FDEP uses, how EPA would enforce
the criteria, and how specific entities would be affected. In response,
EPA points out that WQS generally, and EPA's rule specifically, do not
specify how to achieve those WQS. As discussed above, the State of
Florida will determine how best to meet these Federal numeric criteria
in a way that most effectively meets the needs of its citizens and
environment. FDEP is the primary agency responsible for implementing
CWA programs in the State of Florida. As such, EPA defers to FDEP in
administering applicable CWA programs consistent with the CWA and EPA's
implementing regulations. EPA has worked closely with the State to
address nitrogen/phosphorus pollution problems in Florida. EPA will
continue to collaborate with FDEP as the State implements EPA's
Federally-promulgated numeric criteria.
    Several commenters asserted that Florida would not be able to
implement EPA's Federally-promulgated numeric criteria without first
adopting the criteria into State law. EPA does not believe that, in
order to implement EPA's Federally-promulgated numeric criteria, FDEP
is required to adopt EPA's rule into State law. EPA's numeric criteria
for Florida's lakes and flowing waters will be effective for CWA
purposes 15 months after publication of the final criteria in the
Federal Register and will apply in addition to any other existing CWA-
effective criteria for Class I or Class III waters already adopted by
the State and submitted to EPA (and for those adopted after May 30,
2000, adopted and submitted by FDEP and approved by EPA). FDEP retains
the authority to move forward with its own rulemaking process at any
time to establish State numeric criteria and to submit such criteria to
EPA for review and approval under section 303(c) of the CWA. If FDEP
does not adopt State numeric criteria, the Department retains its
current authority to implement Federally promulgated criteria through
the State's narrative or ``free from'' criteria. FDEP's General Counsel
has confirmed, in a 2005 letter to EPA that the State's water quality
criteria regulations for surface waters, set out at Section 62-302.500,
F.A.C., provide authority for the Department to address and implement
EPA promulgated criteria in CWA programs.\161\
---------------------------------------------------------------------------

    \161\ FDEP. 2005, January 5. ``Petition to Withdraw Florida's
NPDES Authority of March 19, 2004 Response to EPA Letter of December
8, 2004.'' Letter from George Munson, General Counsel.
---------------------------------------------------------------------------

    Several commenters suggested that EPA incorporate water quality
targets from adopted and approved TMDLs as site-specific criteria
(SSAC) for specific waters in lieu of the more broadly applicable
criteria promulgated by EPA. These commenters asserted that the TMDL
values better reflect site-specific needs and were already serving as
the basis for many pollutant reduction actions, including Basin
Management Action Plans (BMAPs). Commenters expressed concern that
actions to implement the TMDLs would be curtailed or delayed because of
the uncertainty whether additional reductions might be required, and
that both the Federal SSAC process (described in Section V.C of this
notice) and use attainability analysis (UAA)/variance process would be
too burdensome and time-consuming to be effective alternatives.
Similarly, some commenters requested that specific restoration projects
be exempted from EPA's criteria or that EPA employ a process for
delaying application of the criteria where a water is under study.
    EPA's position is that EPA-established or approved TMDLs may
provide sufficient information to support a site-specific alternative
criterion, but that such a demonstration should be made after
considering and taking into account any new relevant information
available, including but not limited to the substantial analysis and
data considered and made a part of the record for this final rule. For
this reason, EPA considers the Federal SSAC procedure to be the
appropriate mechanism for determining whether any specific TMDL target
should be adopted as a SSAC. For restoration projects or waters under
study, a State-issued variance may also be an appropriate vehicle for
regulatory flexibility.
    Several commenters requested clarification regarding the effect of
EPA's Federally-promulgated numeric criteria on existing TMDLs. A TMDL
is established at levels necessary to attain and maintain ``applicable
narrative and numerical water quality standards.'' (See 40 CFR
130.7(c)(1)). A TMDL addressing a narrative WQS requires translating
the narrative WQC into a numeric water quality target (e.g., a
concentration). TMDLs are not implemented directly but through other
programs such as NPDES permitting and non-point source programs. For
example, a NPDES permitting authority must ensure at the time of permit
issuance that WQBELs are consistent with the assumptions and
requirements of any available wasteload allocation (WLA) for that
discharge contained in a TMDL, as well as derive from and comply with
all applicable WQS. (See 40 CFR 122.44(d)(1)(vii)(A) and (B)).
    Some existing TMDLs translate the same portion of Florida's
narrative criterion, Subsection 62-302.530(47)(b), F.A.C., as EPA has
translated to derive its numeric criteria, e.g. no imbalance in natural
populations of aquatic flora and fauna. The permitting authority must
ensure that any permit issuance or re-issuance include WQBELs that are
as stringent as necessary to meet the promulgated numeric criteria,
pursuant to CWA section 301(b)(1)(C) and 40 CFR 122.44(d)(1). These
existing TMDLs will likely include information that is relevant and
helpful in evaluating necessary discharge limitations, such as
consideration of other sources of the pollutant and hydrodynamics of
the waterbody. EPA recommends that existing TMDLs that are based on
translation of Subsection 62-302.520(47)(b), F.A.C. (``no imbalance in
natural population of aquatic flora and

fauna''), undergo a two-part evaluation. The first step is to assess
whether the waterbody is still, in fact, water quality-limited
(impaired) using the new numeric WQC. If the waterbody is still water
quality-limited, then a second evaluation should be conducted to
determine whether the existing TMDL based on the narrative is
sufficient to meet the new numeric criterion, and in turn, whether or
not it may be appropriate to revise the TMDL. The State may also wish
to pursue submitting the TMDL water quality target derived by
translating the narrative for determination as a Federal SSAC.
    Other existing TMDLs translate another part of Florida's narrative
nutrient criterion, Subsection 62-302.530(47)(a) F.A.C. This provision
provides that nitrogen/phosphorus pollution shall be limited so as to
prevent violation of another Florida WQS. Where a TMDL water quality
target was developed as a translation of this part of Florida's
narrative nutrient criterion (for example, that amount of nitrogen/
phosphorus that would not cause excursions of Florida's dissolved
oxygen WQS), the appropriate WQBEL is the more stringent result of
applying the TMDL WLA or the promulgated numeric criteria.
    It is important to keep in mind that no TMDL will be rescinded or
invalidated as a result of this final rule, nor does this final rule
have the effect of withdrawing any prior EPA approval of a TMDL in
Florida. Neither the CWA nor EPA regulations require TMDLs to be
completed or revised within any specific time period after a change in
water quality standards occurs. TMDLs are typically reviewed as part of
States' ongoing water quality assessment programs. Florida may review
TMDLs at its discretion based on the State's priorities, resources, and
most recent assessments. NPDES permits are subject to five-year permit
cycles, and in certain circumstances are administratively continued
beyond five years. In practice, States often prioritize their
administrative workload in permits. This prioritization could be
coordinated with TMDL review.
    EPA-established or approved TMDLs may provide sufficient
information to support a site-specific alternative criterion (SSAC).
The SSAC path is one that local governments or businesses may want to
pursue where they desire assurance that the TMDL will become the
applicable numeric criteria in advance of the State's review of the
TMDL or where substantial investments in pollution controls are
predicated on water quality based effluent limits, and local
governments or businesses need long-term planning certainty before
making these investments. The demonstrations supporting SSAC requests
for TMDLs should reflect any new relevant information that has become
available since the TMDL was developed, including but not limited to
the substantial analysis and data considered and made a part of the
record for this final rule. For this reason, EPA considers the Federal
SSAC procedure to be the appropriate mechanism for determining whether
any specific TMDL target should replace the otherwise applicable
numeric criteria in this final rule. EPA will work cooperatively with
entities requesting SSAC to expedite consideration of TMDL targets and
associated TN and/or TP levels as Federal SSAC for purposes of this
final rule. As explained in the preamble to the final rule, EPA has
delayed the effective date of its numeric criteria for 15 months. EPA
encourages any entity wishing to have EPA adopt a particular TMDL
target as a SSAC to submit such TMDL to EPA for consideration as a SSAC
as soon as possible during these 15 months. When submitting such
requests to EPA, such entity must copy FDEP so that FDEP may provide
any comments it has to EPA. EPA would then review the SSAC application
and prepare the SSAC for public notice once this final rule takes
effect. Following this process, the TMDL target, if scientifically and
technically justified, could replace the otherwise applicable numeric
criteria within a very short period of time after this final rule takes
effect. Following any such establishment of site-specific numeric
criteria, the State of Florida may review and/or revise the TMDL at its
discretion based on the changed criteria and the State's priorities,
resources, and most recent assessments. EPA is still required to
approve any changes to a previously approved TMDL.
    EPA is extending the effective date of this rule, with the
exception of the site-specific alternative criteria provision for
reasons discussed below, for 15 months to allow time for the Agency to
work with stakeholders and FDEP on important implementation issues and
to help the public and all affected parties better understand the final
criteria and the bases for those criteria. EPA solicited comment on the
rule's proposed effective date in the preamble to the proposed rule (75
FR 4216 (January 26, 2010)) and received many comments requesting that
EPA delay the effective date of the final criteria. A range of
commenters suggested delayed effective dates from several months to
several years, including linking the effective date of this rule with
the forthcoming estuaries and coastal waters rule to allow closer
coordination of the related parts of the two rulemakings. EPA does not
agree with some commenters that such an extensive delay is necessary.
However, EPA does believe, as discussed below, that these criteria
present a unique opportunity for substantial nitrogen and phosphorus
loadings reductions in the State that would be greatly facilitated and
expedited by strongly coordinated and well-informed stakeholder
engagement, planning, and support before a rule of this significance
and broad scope begins to take effect and be implemented through the
State's regulatory programs.
    EPA believes that it is critical, before the rule becomes
effective, to engage and support, in full partnership with FDEP, the
general public, stakeholders, local governments, and sectors of the
regulated community across the State in a process of public outreach,
education, discussion, and constructive planning. EPA solicited comment
on the proposed rule in January 2010 and has carefully considered those
comments, which numbered more than 22,000, in developing the final
rule. However, the nature of rule development has kept EPA from
publicly discussing the contents of the final rule until the rule
development process, itself, was complete. An investment in outreach,
information, coordination, technical assistance and planning following
this action may result in far more effective, expeditious, and
ultimately effective implementation of appropriate and badly needed
nutrient pollution reduction measures leading to public health and
environmental improvements, the goals of this rule. EPA recognizes that
in order for FDEP to effectively implement the final criteria for
nutrients, it needs to plan how to best address the criteria in State
programs such as the permits, waterbody assessment and listing, and
TMDL programs. The State may need to develop implementation plans and
guidance for affected State regulatory programs, train employees, and
educate the public and regulated communities. EPA will work with FDEP
as a partner over the next 15 months as FDEP takes the steps necessary
to implement the new standards in an orderly manner. Moreover, EPA
believes it would be useful and beneficial to have discussions with
State and local officials, organizations of interested parties, and
with the general public to explain the final rule, the bases for that

rule, and respond to implementation questions and concerns.
    Several stakeholder groups have provided comments about particular
implementation issues that will require time to address before
effective implementation of the final rule can be achieved. Florida has
a unique local government administration structure that includes
county, municipal, and special districts, all which have overlapping
authorities with respect to managing water resources. The special
districts provide water resource management oversight of flood control
and water supply services. These multiple layers of government
authorities will require time to coordinate responsibilities. An
additional concern for local governments is their budgeting process.
Most local governments operate on a fiscal year cycle of October to
September; thus they have recently begun a new fiscal year. These local
governments engage in multi-year budget planning and have already begun
laying the budget foundations for up to five successive years. EPA
recognizes that Florida's agricultural community has implemented a
variety of best management practices (BMPs) that are effective at
reducing nitrogen and phosphorus pollution from farms. However,
Florida's agriculture industry is composed of a large number of small
farms (about 17,000) that have average annual sales of less than
$10,000 each, and most do not receive any form of government
assistance.\162\ EPA anticipates that the Natural Resource Conservation
Service and the University of Florida/Institute of Food and
Agricultural Sciences Extension will need time to educate those not
currently enrolled in nutrient management and BMP programs to control
nutrient runoff.
---------------------------------------------------------------------------

    \162\ NASS. 2009a. 2007 Census of agriculture Florida State and
county data, Volume 1, Geographic Area Series, Part 9, AC-07-A-9,
Updated December 2009, National Agricultural Statistics Service,
U.S. Department of Agriculture, Washington, DC. http://www.agcensus.usda.gov/Publications/2007/Full_Report/Volume_1,_Chapter_1_State_Level/Florida/flv1.pdf (retrieved July 15, 2010).
    NASS. 2009. 2009 State agriculture overview--Florida. U.S.
Department of Agriculture, National Agricultural Statistics Service,
Washington, DC, http://www.nass.usda.gov/Statistics_by_State/Ag_Overview/AgOverview_FL.pdf (retrieved June 17, 2010).
---------------------------------------------------------------------------

    A delayed effective date of 15 months for the criteria will also
provide time for interested parties to pursue site-specific alternative
criteria (SSAC) for a given waterbody. EPA's final rule and associated
preamble describe the process by which any entity may seek a SSAC. A
decision to seek a SSAC could not be made, however, until interested
parties know what the applicable criteria would be. The Federal SSAC
portion of the rule, Sec.  131.43(e), goes into effect 60 days after
publication of this rule to allow this important work to proceed in
advance of the effective date for the remaining provisions of the rule.
During the 15 months before the criteria become effective, parties may
evaluate the final criteria, decide whether they want to seek a SSAC,
and, if so, submit their SSAC application materials to EPA, copying
FDEP. EPA could then review the application, and if complete, public
notice the application and technical support document pursuant to the
SSAC provision in the final rule. If, after reviewing public comment,
EPA believes that the SSAC application meets the requirements of this
rule, EPA could determine that such SSAC apply to the specific
waterbody in lieu of the criteria in the final rule, even before the
criteria in the final rule become effective due to the earlier
effective date of the SSAC provision.
    EPA believes that the 15-month period of time between publication
in the Federal Register and the effective date of the criteria will
ultimately result in attainment of the criteria in an overall shorter
period of time. As EPA frequently points out in its guidance and
training materials, criteria are not ``self-implementing'', that is, it
takes knowledgeable and experienced professionals to effectively and
properly employ the criteria in monitoring and assessment programs,
permit limit derivation and expression, nonpoint source (NPS) control
strategies, and other program applications. Without time to develop
procedures, there is the risk of ineffective implementation that will
not meet the underlying objective of this action--to restore and
protect Florida's waters from harm caused by nitrogen and phosphorus
pollution. Well designed and mapped out NPS control strategies, in
particular, will be critical to gain stakeholder trust and
participation.
    EPA wishes to actively engage in partnership with FDEP to support
FDEPs implementation of these new standards, for example by considering
applications for site-specific alternative criteria. After careful
consideration of time requirements for critical steps, along with
recognition of important planning and accounting mechanisms such as
fiscal years, and local and county meeting and planning cycles, EPA has
determined that a 15-month time period is both reasonable and will
allow time for important implementation activities to take place. This
15-month period will allow for a four-month education and outreach
rollout to cover the major interest sectors and geographic locations
throughout the State of Florida; a three-month period of training and
guidance concurrent with data synthesis and analysis to support
potential SSAC development; a two-month public comment and response
period to allow development of effective guidance, training and
possible workshops to run concurrent with SSAC submittals; a three-
month period for finalizing guidance materials along with development
of rollout strategies (e.g., for NPS control) concurrent with notice
and comment of SSAC; and finally a 3-month period for statewide
education and training on guidance and contingency planning. In short,
the 15 months before the criteria become effective will ensure
application of programs to achieve criteria in a manner that makes the
most efficient use of limited resources and gains the broadest possible
support for timely and effective action upon reaching the effective
date of the criteria.

IV. Under what conditions will Federal standards be withdrawn?

    Under the CWA, Congress gave States primary responsibility for
developing and adopting WQS for their navigable waters. (See CWA
section 303(a)-(c)). Although EPA is promulgating numeric criteria for
lakes and springs throughout Florida and flowing waters outside the
South Florida Region, Florida continues to have the option to adopt and
submit to EPA numeric criteria for the State's Class I and Class III
waters consistent with CWA section 303(c) and implementing regulations
at 40 CFR part 131.
    Pursuant to 40 CFR 131.21(c), EPA's promulgated WQS are applicable
WQS for purposes of the CWA until EPA withdraws those Federally-
promulgated WQS. Withdrawing the Federal standards for the State of
Florida would require rulemaking by EPA pursuant to the requirements of
the Administrative Procedure Act (5 U.S.C.551 et seq.). EPA would
undertake such a rulemaking to withdraw the Federal criteria if and
when Florida adopts and EPA approves numeric criteria that fully meet
the requirements of section 303(c) of the CWA and EPA's implementing
regulations at 40 CFR part 131.

V. Alternative Regulatory Approaches and Implementation Mechanisms

A. Designating Uses

(1) Background and Analysis
    Under CWA section 303(c), States shall adopt designated uses after
taking ``into consideration the use and value of water for public water
supplies, protection and propagation of fish, shellfish, and wildlife,
recreation in and on the water, agricultural, industrial and other
purposes including navigation.'' Designated uses ``shall be such as to
protect the public health or welfare, enhance the quality of water and
serve the purposes of [the CWA].'' (See CWA section 303(c)(2)(A)).
EPA's regulation at 40 CFR 131.3(f) defines ``designated uses'' as
``those uses specified in water quality standards for each waterbody or
segment whether or not they are being attained.'' A ``use'' is a
particular function of, or activity in, waters of the United States
that requires a specific level of water quality to support it. In other
words, designated uses are a State's concise statements of its
management objectives and expectations for each of the individual
surface waters under its jurisdiction.
    In the context of designating uses, States often work with
stakeholders to identify a collective goal for their waters that the
State intends to strive for as it manages water quality. States may
evaluate the attainability of these goals and expectations to ensure
they have designated appropriate uses. (See 40 CFR 131.10(g)).
Consistent with CWA sections 101(a)(2) and 303(c)(2)(A), EPA's
implementing regulations specify that States adopt designated uses that
provide water quality for the protection and propagation of fish,
shellfish, and wildlife and for recreation in and on the water,
wherever attainable. (See 40 CFR 131.10). Where States do not designate
those uses, or remove those uses, they must demonstrate that such uses
are not attainable consistent with the use attainability analysis (UAA)
provisions of 40 CFR 131.10, specifically 131.10(g). States may
determine, based on a UAA, that attaining a designated use is not
feasible and propose to EPA to change the use to something that is
attainable. This action to change a designated use must be completed in
accordance with EPA regulations. (See 40 CFR 131.10(g) and (h)). In
implementing these regulations, EPA allows grouping waters together in
a watershed in a single UAA, provided that there is site-specific
information to show how each individual water fits into the group in
the context of any single UAA and how each individual water meets the
applicable requirements of 40 CFR 131.10(g).
    EPA's final numeric criteria for lakes and flowing waters apply to
those waters designated by FDEP as Class I (Potable Water Supplies) or
Class III (Recreation, Propagation and Maintenance of a Healthy, Well-
Balanced Population of Fish and Wildlife). If Florida removes either
the Class I and/or Class III designated use for any particular
waterbody ultimately affected by this rule, and EPA finds that removal
to be consistent with CWA section 303(c) and regulations at 40 CFR part
131, then the Federally-promulgated numeric criteria would not apply to
that waterbody because it would no longer be designated Class I or III.
Instead, any criteria associated with the newly designated use would
apply to that waterbody.
(2) Summary of Major Comments
    Many commenters took the opportunity to emphasize the need to
adhere to the regulations governing the process of modifying or
removing a designated use. Some commenters suggested that the process
to change a designated use is extremely difficult. EPA's experience is
that UAAs may range from simple to complex, depending on a variety of
factors, such as the type of waterbody involved, the size of the
segment, the use being changed, the relative degree of change proposed
for the designated use, the presence of unique ecological habitats, and
the level of public interest/involvement in the designated use
decision. EPA agrees that, while a UAA is being conducted, the current
designated use and corresponding criteria remain in place. In the case
of Florida's Class I and Class III flowing waters and lakes, EPA's
promulgated numeric criteria will remain the applicable WQS for CWA
purposes, including assessments, listings, TMDL development and the
issuance of NPDES permits, unless and until the State adopts revised
designated uses (with different associated criteria) that are submitted
to and approved by EPA under CWA section 303(c).

B. Variances

(1) Final Rule
    For purposes of this rule, EPA is promulgating criteria that apply
to use designations that Florida has already established. EPA believes
that the State has sufficient authority to use its currently EPA-
approved variance procedures with respect to a temporary modification
of its Class I or Class III uses as it pertains to any Federally-
promulgated criteria. For this reason, EPA did not propose and is not
promulgating an alternative Federal variance procedure.
(2) Background and Analysis
    A variance is a temporary modification to the designated use and
associated water quality criteria that would otherwise apply to the
receiving water.\163\ Variances constitute new or revised WQS subject
to the substantive requirements applicable to removing a designated
use.\164\ Thus, a variance is based on the same factors, set out at 40
CFR 131.10(g), that are required to revise a designated use through a
UAA. Typically, variances are time-limited (e.g., three to five years),
but renewable. Temporarily modifying the designated use for a
particular waterbody through a variance process allows a State to limit
the applicability of a specific criterion to that water and to identify
an alternative designated use and associated criteria to be met during
the term of the variance. A variance should be used instead of removal
of a use where the State believes the standard can be attained at some
point in the future. By maintaining the designated use for all other
criteria and dischargers, and by specifying a point in the future when
the designated use will be fully applicable in all respects, the State
ensures that further progress will be made in improving water quality
and attaining the standard. A variance may be written to address a
specified geographic area, a specified pollutant or pollutants, and/or
a specified pollutant source. All other applicable WQS not specifically
modified by the variance would remain applicable (e.g., any other
criteria adopted to protect the designated use). State variance
procedures, as part of State WQS, must be consistent with the
substantive requirements of 40 CFR part 131. Each variance, as a
revised WQS, must be submitted to EPA for review pursuant to CWA
section 303(c). A variance allows, among other things, NPDES permits to
be written such that reasonable progress is made \165\ toward attaining
the underlying standards for affected waters without violating section
402(a)(l) of the Act, which requires that NPDES permits

must meet the applicable WQS. (See CWA section 301(b)(1)(C)).
---------------------------------------------------------------------------

    \163\ Water Quality Standards Regulation, 40 CFR part 131:
Advance notice of proposed rulemaking. USEPA FR 63:129 (July 7,
1998). p. 36741-36806.
    \164\ In re Bethlehem Steel Corporation, General Counsel Opinion
No. 58. March 29, 1977 (1977 WL 28245 (E.P.A. G.C.)).
    \165\ USEPA. 1994. Water Quality Standards Handbook: Second
Edition. EPA-823-B-94-005a. U.S. Environmental Protection Agency,
Office of Water, Washington, DC.
---------------------------------------------------------------------------

(3) Summary of Major Comments
    In response to comments, EPA agrees that variances could be adopted
on a multiple-discharger basis and can be renewed so long as the State
and EPA conclude that such variances are consistent with the CWA and
implementing regulations. In this regard, EPA allows grouping waters
together in a watershed in a single variance application, provided that
there is site-specific information to show how each individual water
fits into the group in the context of any single variance and how each
individual water meets the applicable requirements of 40 CFR 131.10(g).
EPA disagrees that Florida law, at 403.201(2), F.S., prohibits the
State from issuing variances for waters affected by the Federally-
promulgated numeric criteria. Florida law at 403.201(2), F.S., provides
that a variance may not be granted that would result in State
requirements that are less stringent than a comparable Federal
provision or requirement. As discussed above, a variance is a temporary
modification to the designated use and thus to the associated water
quality criteria that would otherwise apply to the receiving water.
EPA's Federal rule, however, does not promulgate or revise any Florida
designated uses. EPA's criteria are intended to protect the Class I and
Class III designated uses that Florida already has in place. EPA's
criteria do not apply where and when the use is something other than
Class I or Class III, as would be the case for a variance. Rather,
Florida would establish alternative criteria associated with the
variance. Any variance would constitute a new or revised WQS subject to
EPA review and approval pursuant to section 303(c) of the CWA.

C. Site-Specific Alternative Criteria

(1) Final Rule
    EPA believes that there is benefit in establishing a specific
procedure in the Federal rule for EPA adoption of Federal site-specific
alternative criteria (SSAC) for the numeric chlorophyll a, TN, TP, and
nitrate+nitrite criteria in this rule. In this rulemaking, EPA is
promulgating a procedure whereby the Regional Administrator, Region 4,
may establish a SSAC after providing for public comment on the proposed
SSAC and the supporting documentation. (See 40 CFR 131.43(e)). This
procedure allows any entity, including the State, to submit a proposed
Federal SSAC directly to EPA for the Agency's review and assessment as
to whether an adjustment to the applicable Federal numeric criteria is
appropriate and warranted. The Federal SSAC process is separate and
distinct from the State's SSAC processes in its WQS.
    The Federal SSAC procedure allows EPA to determine that a revised
site-specific chlorophyll a, TN, TP, or nitrate + nitrite numeric
criterion should apply in lieu of the generally applicable criteria
promulgated in this final rule where that SSAC is demonstrated to be
protective of the applicable designated use(s). The promulgated
procedure provides that EPA will solicit public comment on its
determination. Because EPA's rule establishes this procedure,
implementation of this procedure does not require withdrawal of
Federally-promulgated criteria for affected water bodies for the
Federal SSAC to be effective for purposes of the CWA. EPA has
promulgated similar procedures for EPA granting of variances and SSACs
in other Federally-promulgated WQS.\166\
---------------------------------------------------------------------------

    \166\ See 40 CFR 131.33(a)(3), 40 CFR 131.34(c), 40 CFR
131.36(c)(3)(iii), 40 CFR 131.38(c)(2)(v), 40 CFR 131.40(c).
---------------------------------------------------------------------------

    EPA is aware of concerns expressed by some commenters that a
waterbody may exceed the numeric criteria in this rule and still meet
Florida's designated uses related to recreation, public health, and the
propagation and maintenance of a healthy, well-balanced population of
fish and wildlife. EPA recognizes that there may be certain situations
where additional, new, or more specific data related to the local
conditions or biology of a particular waterbody may well support an
alternate site-specific numeric criteria which may appropriately be
more (or less) stringent than the criteria in this final rule in order
to ensure maintenance of instream designated uses and protection of
downstream waters. EPA believes that the SSAC process is an appropriate
mechanism to address such situations and is committed to acting on
Federal SSAC applications intended to address such situations as
expeditiously as possible.
    The process for obtaining a Federal SSAC includes the following
steps. First, an entity seeking a SSAC compiles the supporting data,
conducts the analyses, develops the expression of the criterion, and
prepares the supporting documentation demonstrating that alternative
numeric criteria are protective of the applicable designated use. The
``entity'' may be the State, a city or county, a municipal or
industrial discharger, a consulting firm acting on a behalf of a
client, or any other individual or organization. The entity requesting
the SSAC bears the burden of demonstrating that any proposed SSAC meets
the requirements of the CWA and EPA's implementing regulations,
specifically 40 CFR 131.11. Second, if the entity is not the State, the
entity must provide notice of the proposed SSAC to the State, including
all supporting documentation so that the State may provide comments on
the proposal to EPA. Third, the Regional Administrator will evaluate
the technical basis and protectiveness of the proposed SSAC and decide
whether to publish a public notice and take comment on the proposed
SSAC. The Regional Administrator may decide not to publish a public
notice and instead return the proposal to the entity submitting the
proposal, with an explanation as to why the proposed SSAC application
did not provide sufficient information for EPA to determine whether it
meets CWA requirements or not. If EPA solicits public comment on a
proposed SSAC, upon review of comments, the Regional Administrator may
determine that the Federal SSAC is appropriate to account for site-
specific conditions and make that determination publicly available
together with an explanation of the basis for the decision. The
Regional Administrator may also determine that the Federal SSAC is not
appropriate and make that determination publicly available together
with an explanation of the basis for the decision.
    To successfully develop a Federal SSAC for a given lake, stream, or
spring, a thorough analysis is necessary that indicates how designated
uses are being supported both in the waterbody itself and in downstream
water bodies at concentrations of either TN, TP, chlorophyll a, or
nitrate+nitrite that are either higher or lower than the Federally-
promulgated applicable criteria. This analysis should have supporting
documentation that consists of examining both indicators of longer-term
response to multiple stressors, such as benthic macroinvertebrate
health as determined by Florida's Stream Condition Index (SCI), and
indicators of shorter-term response specific to nitrogen/phosphorus
pollution, such as periphyton algal thickness or water column
chlorophyll a concentrations. To pursue a Federal SSAC on a watershed-
wide basis, the same types of procedures that EPA used to develop the
Federally promulgated applicable criteria can be used with further
refinements to the categorization of water bodies. For example, an
entity could derive alternative instream protective TP and/or TN values
using

EPA's approach by further sub-delineating the Nutrient Watershed
Regions and providing the corresponding data, analysis and
documentation to support derivation of an alternative criteria that is
protective of the designated use that applies both to the smaller
watershed regions as well as to downstream waters. This type of refined
reference condition approach is described in EPA guidance manuals \167\
and would be consistent with methods used to develop the Federally-
promulgated criteria for Florida. In developing either a site-specific
or watershed-wide Federal SSAC, it is necessary to ensure that values
allowed in an upstream segment as a result of a SSAC provide for the
attainment and maintenance of the WQS of downstream waters. It will be
important to examine a stream system on a broader basis to ensure that
a SSAC established for one segment does not result in adverse effects
in nearby segments or downstream waters, such as a downstream lake.
---------------------------------------------------------------------------

    \167\ USEPA. 2000b. Nutrient Criteria Technical Guidance Manual:
Rivers and Streams. EPA-822-B-00-002. U.S. Environmental Protection
Agency, Office of Water, Washington, DC.
---------------------------------------------------------------------------

    This rule specifically identifies four approaches for developing
SSAC. The first two approaches are replicating the approaches EPA used
to develop stream and lake criteria, respectively, and applying these
methods to a smaller subset of waters. The third approach for
developing SSAC is to conduct a biological, chemical, and physical
assessment of waterbody conditions. The fourth approach for developing
SSAC is a general provision for using another scientifically defensible
approach that is protective of the designated use. The first two
approaches for developing SSAC replicate EPA's methods in deriving the
stream and lake criteria set out in this final rule. To understand the
necessary steps in this analysis, interested parties should refer to
the complete documentation of these methods in the materials included
in the rule docket.
    The third approach for developing SSAC is to conduct a biological,
chemical, and physical assessment of waterbody conditions. This is a
more general approach than the replication approaches and would need
additional detail and description of supporting rationale in the
documentation submitted to EPA. The components of this approach could
include, but not be limited to, evaluation of benthic macroinvertebrate
health using the Stream Condition Index (SCI), presence or absence of
native flora and fauna, chlorophyll a concentrations or periphyton
density, average daily dissolved oxygen fluctuation, organic versus
inorganic components of total nitrogen, habitat assessment, and
hydrologic disturbance. This approach could apply to any waterbody
type, with specific components of analysis tailored for the situation.
The fourth approach for developing SSAC is a general provision for
using another scientifically defensible approach that is protective of
the designated use. This provision allows applicants to make a complete
demonstration to EPA using methods not otherwise described in the rule
or its statement of basis, consistent with 40 CFR 131.11(b)(1)(iii).
This approach could potentially include use of mechanistic models or
other data and information.
 (2) Background and Analysis
    A SSAC is an alternative value to criteria set forth in this final
rule that would be applied on a watershed, area-wide, or water-body
specific basis that meets the regulatory test of protecting the
instream designated use, having a basis in sound science, and ensuring
the protection and maintenance of downstream WQS. SSAC may be more or
less stringent than the otherwise applicable Federal numeric criteria.
In either case, because the SSAC must protect the same designated use
and must be based on sound science (i.e., meet the requirements of 40
CFR 131.11(a)), there is no need to modify the designated use or
conduct a UAA. A SSAC may be appropriate when further scientific data
and analyses can bring added precision or accuracy to express the
necessary level or concentration of chlorophyll a, TN, TP, and/or
nitrate+nitrite that protects the designated use for a particular
waterbody.
 (3) Summary of Major Comments
    Many commenters expressed support for the concept of EPA's proposed
SSAC procedure, although many also expressed concerns about the
viability, requirements, expense, and time associated with the process.
In EPA's proposed rule, the SSAC process was to be initiated by the
State submitting a request to EPA. Many commenters were confused about
the relationship between the Federal SSAC process and the State's Type
1 and Type 2 SSAC processes, and how the processes relate for purposes
of the Federal rule. The Federal SSAC process is separate and
independent from the State SSAC processes. A Federal SSAC is
established by the Regional Administrator of EPA Region 4 after due
notice and comment from the public. To resolve this confusion, and to
provide a more direct means for entities other than the State to
initiate the SSAC process, EPA's final rule provides that any entity
may submit a request for a SSAC directly to the Regional Administrator.
The final rule adds a requirement that entities submit proposed SSAC
and supporting materials to the State at the same time those materials
are submitted to EPA to ensure the State has the opportunity to submit
comments to EPA.
    As several commenters have pointed out, Florida WQS regulations
currently do not authorize the State to adopt a SSAC as State WQS
except where natural conditions are outside the limits of broadly
applicable criteria established by the State (Section 62-302.800,
F.A.C.). However, the State may choose to be the entity that submits a
SSAC request to EPA under the Federal process described above and set
forth at 40 CFR 131.43(e). There is no requirement that the State go
through its own State-level Type 1 or Type 2 SSAC process before
submitting a proposed SSAC to EPA for consideration under this rule.
    Commenters included suggestions for specific approaches for
developing SSAC as well as an ``expedited'' process for determination
as a Federal SSAC. EPA agrees that many of the suggested approaches
have merit for purposes of developing SSAC, and has adapted many of the
suggestions to provide more information on approaches that would meet
the general requirements for protective criteria. Many of the comments
regarding an ``expedited'' process suggested a process where SSAC
become effective automatically, without need for EPA review and
approval. With the exception of State adjustment of lake criteria
within a very specific and limited range accompanied by a specified
data set and calculation as discussed in Section III.C(2)(e) above, the
Agency does not agree with the view that criteria established in this
rule can be revised without documentation and public notice and comment
process as outlined above.\168\ Another commenter asked about the
potential to develop a SSAC on a ``watershed-scale.'' EPA does not see
any barrier to conducting such an analysis, where it can be
demonstrated that the watershed-scale SSAC is protective for all waters
in a particular grouping and meets the requirements of 40 CFR 131.11
and 40

CFR 131.10(b). Many commenters expressed the desire to defer the
applicability of promulgated criteria prior to developing a SSAC. The
Federal SSAC portion of the rule, Sec.  131.43(e), goes into effect 60
days after publication of this rule to allow this important work to
proceed in advance of the effective date of 15 months after publication
for the remaining provisions of the rule. The SSAC review process will
depend in substantial part on the nature of the SSAC proposal itself:
Its clarity, substance, documentation, and scientific rigor. Some
commenters stated that EPA's requirement that Federal SSAC be
scientifically defensible and protective of designated uses is too
vague; however, it is the same requirement for criteria in the Federal
WQS regulation. (See 40 CFR 131.11). EPA will consider the need for
further developing supporting technical guidance in the future if it
appears at that time that such guidance would help support the process.
---------------------------------------------------------------------------

    \168\ EPA's criteria allow for one-time site-specific
modifications to the promulgated lake criteria, without requiring
those modifications to be submitted as SSAC. See 40 CFR
131.43(c)(1)(ii) and Section III.C(2)(e).
---------------------------------------------------------------------------

D. Compliance Schedules

(1) Final Rule
    Florida has adopted a regulation authorizing compliance schedules.
That regulation, Subsection 62-620.620(6), F.A.C., is not affected by
this final rule. The complete text of the Florida rules concerning
compliance schedules is available at https://www.flrules.org/gateway/RuleNo.asp?ID=62-620.620. Florida is, therefore, authorized to grant
compliance schedules, as appropriate, under its rule for WQBELs based
on EPA's numeric criteria.
(2) Background and Analysis
    A compliance schedule, or schedule of compliance, refers to ``a
schedule of remedial measures included in a `permit,' including an
enforceable sequence of interim requirements * * * leading to
compliance with the CWA and regulations.'' (See 40 CFR 122.2, CWA
section 502(17)). In an NPDES permit, WQBELs are effluent limits based
on applicable WQS for a given pollutant in a specific receiving water
(See NPDES Permit Writers Manual, EPA-833-B-96-003, December, 1996).
EPA regulations provide that schedules of compliance may only be
included in permits if they are determined to be ``appropriate'' given
the circumstances of the discharge and are to require compliance ``as
soon as possible'' (See 40 CFR 122.47).\169\
---------------------------------------------------------------------------

    \169\ Hanlon, Jim, USEPA Office of Wastewater Management. 2007,
May 10. Memorandum to Alexis Stauss, Director of Water Division EPA
Region 9, on ``Compliance Schedules for Water Quality-Based Effluent
Limitations on NPDES Permits.''
---------------------------------------------------------------------------

(3) Summary of Major Comments
    EPA generally received favorable comment on its description of
compliance schedules. Some commenters asked EPA to consider
promulgating its own compliance schedule provisions as part of the
final rule. Florida's regulations, however, already include an
authorizing provision that allows NPDES permit writers to include
compliance schedules in permits, where appropriate. Florida's
regulations do not limit the criteria which may be subject to
compliance schedules. Therefore, Florida may choose to issue permit
compliance schedules for nitrogen/phosphorus pollution, as appropriate.
As a result, there is no need for EPA to provide an additional
compliance schedule authorizing provision in this final rule. EPA
disagrees with commenters who assert that Florida's regulation at
Subsection 62-620.620(6), F.A.C., authorizing compliance schedules
applies only to industrial and domestic wastewater facilities. Chapter
62-620, F.A.C., sets out permit procedures for wastewater facilities or
activities that discharge wastes into waters of the State or which will
reasonably be expected to be a source of water pollution. (See
Subsection 62-620.100(1), F.A.C.). Subsection 62-620.620(6), F.A.C.,
applies, therefore, more broadly than to just industrial and domestic
wastewater facilities. In addition, Chapter 62-4, F.A.C., which sets
out procedures on how to obtain a permit from FDEP, provides that
permits may include a reasonable time for compliance with new or
revised WQS. Subsection 62-4.160(10), F.A.C., does not limit the type
of permits that may include such compliance schedules.

E. Proposed Restoration Water Quality Standard

(1) Final Rule
    In EPA's January 2010 proposal, the Agency proposed a new WQS
regulatory tool for Florida, referred to as ``restoration WQS'' for
impaired waters. This provision was intended to allow Florida to retain