[Federal Register Volume 75, Number 148 (Tuesday, August 3, 2010)]
[Proposed Rules]
[Pages 45579-45583]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2010-19140]
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ENVIRONMENTAL PROTECTION AGENCY
40 CFR Part 131
[EPA-HQ-OW-2009-0596; FRL-9185-2]
RIN 2040-AF11
Water Quality Standards for the State of Florida's Lakes and
Flowing Waters; Supplemental Notice of Data Availability and Request
for Comment
AGENCY: Environmental Protection Agency (EPA).
ACTION: Supplemental notice of data availability and request for
comment.
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SUMMARY: This action is a supplemental notice of data availability and
a request for comment related to EPA's January 26, 2010, notice of
proposed rulemaking (NPRM), proposing numeric nutrient water quality
criteria to protect aquatic life in lakes and flowing waters within the
State of Florida. In the January 2010 NPRM, EPA proposed to classify
Florida's streams into four regions (referred to in the proposed rule
as ``Nutrient Watershed Regions'') for application of total nitrogen
(TN) and total phosphorus (TP) criteria. Streams within each of these
regions (Panhandle, Bone Valley, Peninsula and North Central) reflect
similar geographical characteristics including phosphorus-rich soils,
nutrient concentrations and nutrient ratios. In this notice, EPA is
requesting comment on revised stream region boundaries based on
additional information about watershed delineations and phosphorus-rich
geological formations in Florida. Based on comments and additional
information, this revised regionalization approach would result in five
Nutrient Watershed Regions for Florida's streams and a clarification of
certain watershed boundaries for the Bone Valley and Peninsula regions.
EPA is also requesting comment on basing the TN and TP criteria for the
nutrient watershed regions on a combination of the 75th and 90th
percentile values (depending on regions) of the benchmark sites
outlined in the alternate approach at proposal. EPA is continuing to
consider the primary approach proposed in January 2010 to use the 75th
percentile of sites with healthy biological condition as measured by
the Stream Condition Index (SCI). The January 2010 proposal also
proposed application of the Vollenweider equation to ensure that
nutrient 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.
Today's notice also requests 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. EPA is seeking comment on alternative stream
regionalization approaches, use of the benchmark dataset to derive
criteria, and derivation of lake downstream protection values discussed
in more detail below, and will consider the comments received before
finalizing the proposed rule, ``Water Quality Standards for the State
of Florida's Lakes and Flowing Waters.'' This supplemental notice
focuses solely on the delineation of stream nutrient regions, resulting
criteria associated with two approaches (EPA's SCI-based approach and
the alternative benchmark distribution approach), and protection of
downstream lakes in Florida. EPA is not soliciting comment on any other
provisions of the January 2010 proposal.
DATES: Comments must be received on or before September 2, 2010.
ADDRESSES: Submit your comments, identified by Docket ID No. EPA-HQ-OW-
2009-0596, by one of the following methods:
1. http://www.regulations.gov: Follow the on-line instructions for
submitting comments.
2. E-mail: [email protected].
[[Page 45580]]
3. Mail to: Water Docket, U.S. Environmental Protection Agency,
Mail code: 2822T, 1200 Pennsylvania Avenue, NW., Washington, DC 20460,
Attention: Docket ID No. EPA-HQ-OW-2009-0596.
4. Hand Delivery: EPA Docket Center, EPA West Room 3334, 1301
Constitution Avenue, NW., Washington, DC 20004, Attention Docket ID No.
EPA-HQ-OW-2009-0596. Such deliveries are only accepted during the
Docket's normal hours of operation, and special arrangements should be
made for deliveries of boxed information.
Instructions: Direct your comments to Docket ID No. EPA-HQ-OW-2009-
0596. EPA's policy is that all comments received will be included in
the public docket without change and may be made available online at
http://www.regulations.gov, including any personal information
provided, unless the comment includes information claimed to be
Confidential Business Information (CBI) or other information whose
disclosure is restricted by statute. Do not submit information that you
consider to be CBI or otherwise protected through http://www.regulations.gov or e-mail. The http://www.regulations.gov Web site
is an ``anonymous access'' system, which means EPA will not know your
identity or contact information unless you provide it in the body of
your comment. If you send an e-mail comment directly to EPA without
going through http://www.regulations.gov your e-mail address will be
automatically captured and included as part of the comment that is
placed in the public docket and made available on the Internet. If you
submit an electronic comment, EPA recommends that you include your name
and other contact information in the body of your comment and with any
disk or CD-ROM you submit. If EPA cannot read your comment due to
technical difficulties and cannot contact you for clarification, EPA
may not be able to consider your comment. Electronic files should avoid
the use of special characters, any form of encryption, and be free of
any defects or viruses. For additional information about EPA's public
docket visit the EPA Docket Center homepage at http://www.epa.gov/epahome/dockets.htm.
Docket: All documents in the docket are listed in the http://www.regulations.gov index. Although listed in the index, some information
is not publicly available, e.g., CBI or other information whose
disclosure is restricted by statute. Certain other material, such as
copyrighted material, will be publicly available only in hard copy.
Publicly available docket materials are available either electronically
in http://www.regulations.gov or in hard copy at a docket facility.
The Office of Water (OW) Docket Center is open from 8:30 a.m. until
4:30 p.m., Monday through Friday, excluding legal holidays. The OW
Docket Center telephone number is (202) 566-2426, and the Docket
address is OW Docket, EPA West, Room 3334, 1301 Constitution Avenue,
NW., Washington, DC 20004. The Public Reading Room is open from 8:30
a.m. to 4:30 p.m., Monday through Friday, excluding legal holidays. The
telephone number for the Public Reading Room is (202) 566-1744.
FOR FURTHER INFORMATION CONTACT: Danielle Salvaterra, U.S. EPA
Headquarters, Office of Water, Mailcode: 4305T, 1200 Pennsylvania
Avenue, NW., Washington, DC 20460; telephone number: 202-564-1649; fax
number: 202-566-9981; e-mail address: [email protected].
SUPPLEMENTARY INFORMATION: This supplementary information section is
organized as follows:
Table of Contents
I. General Information
A. What should I consider as I prepare my comments for EPA?
B. How can I get copies of this document and other related
information?
II. Background
III. Supplemental Information on Numeric Nutrient Criteria for the
State of Florida's Lakes and Flowing Waters
A. Stream Regionalization and Alternative Approaches to Stream
Criteria Derivation
B. Downstream Protection of Lakes
I. General Information
A. What should I consider as I prepare my comments for EPA?
1. Submitting CBI. Do not submit this information to EPA through
http://www.regulations.gov or e-mail. Clearly mark the part or all of
the information that you claim to be CBI. For CBI information in a disk
or CD-ROM that you mail to EPA, mark the outside of the disk or CD-ROM
as CBI and then identify electronically within the disk or CD-ROM the
specific information that is claimed as CBI. In addition to one
complete version of the comment that includes information claimed as
CBI, a copy of the comment that does not contain the information
claimed as CBI must be submitted for inclusion in the public docket.
Information so marked will not be disclosed except in accordance with
procedures set forth in 40 CFR part 2.
2. Tips for Preparing Your Comments. When submitting comments,
remember to:
1. Identify the rulemaking by docket number and other identifying
information (subject heading, Federal Register date, and page number).
2. Follow directions--The agency may ask you to respond to specific
questions or to address a particular issue.
3. Explain why you agree or disagree; suggest alternatives and
substitute language for your requested changes.
4. Describe any assumptions and provide any technical information
and/or data that you used.
5. Provide specific examples to illustrate your concerns, and
suggest alternatives.
6. Make sure to submit your comments by the comment period deadline
identified.
B. How can I get copies of this document and other related information?
1. Docket. EPA has established an official public docket for this
action under Docket Id. No. EPA-HQ-OW-2009-0596. The official public
docket consists of the document specifically referenced in this action,
any public comments received, and other information related to this
action. Although a part of the official docket, the public docket does
not include CBI or other information whose disclosure is restricted by
statute. The official public docket is the collection of materials that
is available for public viewing at the OW Docket, EPA West, Room 3334,
1301 Constitution Ave., NW., Washington, DC 20004. This Docket Facility
is open from 8:30 a.m. to 4:30 p.m., Monday through Friday, excluding
legal holidays. The Docket telephone number is 202-566-1744. A
reasonable fee will be charged for copies.
2. Electronic Access. You may access this Federal Register document
electronically through the EPA Internet under the ``Federal Register''
listings at http://www.epa.gov/fedrgstr/.
An electronic version of the public docket is available through
EPA's electronic public docket and comment system, EPA Dockets. You may
use EPA Dockets at http://www.regulations.gov to view public comments,
access the index listing of the contents of the official public docket,
and to access those documents in the public docket that are available
electronically. For additional information about EPA's public docket,
visit the EPA Docket Center homepage at http://www.epa.gov/epahome/dockets.htm. Although not all docket materials may be available
electronically, you may still access any of the publicly available
docket materials through the Docket Facility identified in Section
I.B.1.
[[Page 45581]]
II. Background
On January 26, 2010, EPA proposed ``Water Quality Standards for the
State of Florida's Lakes and Flowing Waters'' (75 FR 4173). EPA
conducted 13 public hearing sessions in six cities in Florida and held
a 90-day public comment period as part of the proposed rule generating
over 22,000 public comments. EPA is reviewing and considering these
comments in preparation of the final rule, which is scheduled to be
signed by the EPA Administrator on October 15, 2010.
Today's notice reflects a review of comments and new information
received by the Agency as part of the public comment process, and
requests further comment on possible revisions, additional options, and
new information related to specific approaches and issues identified in
the January 26, 2010 proposal. EPA is only seeking comment on the items
presented in this supplemental notice. EPA is not soliciting comment on
any other provisions of the January 2010 proposed rule.
III. Supplemental Information on Numeric Nutrient Criteria for the
State of Florida's Lakes and Flowing Waters
A. Stream Regionalization and Alternative Approaches to Stream Criteria
Derivation
EPA proposed classification of Florida's streams north of Lake
Okeechobee by separating watersheds with substantially different stream
molar ratios of TN to TP into Nutrient Watershed Regions (NWR). The
resulting regions reflect the inherent differences in the natural
factors that contribute to nutrient concentrations in streams (e.g.,
geology, soil composition, and/or hydrology). Reliance on a watershed-
based classification approach reflects the understanding that upstream
water quality affects downstream water quality. EPA requested public
comment on the stream regionalization approach as well as factoring in
geological influences from phosphorus-rich soils when classifying
stream regions (75 FR 4195-96). EPA received public comments and
information that suggested refining the proposed stream regions to
account for natural variability in soil nitrogen and phosphorus as well
as clarifying the boundaries of the proposed stream regions.
Today, EPA is requesting comment on a revised approach to certain
stream regions suggested by FDEP and other commenters. More
specifically, EPA is considering additional information on the
influence of phosphorus-rich soils and geology in Florida (associated
with the Hawthorne Group) for areas in the northern Panhandle region.
Based on comments and information received, the Agency is also
considering further refinements to the regional boundaries separating
the Peninsula region from the West Central region (referred to in the
proposed rule as ``Bone Valley'').
Based on geological information,\1\ EPA is considering dividing the
proposed Panhandle region into a Panhandle West (less phosphorus-rich)
and Panhandle East (more phosphorus-rich) region. In drawing the
boundary between the two regions, EPA is continuing to rely on the
watershed approach described in the proposed rule and is considering
using the eastern boundary of the Apalachicola River watershed as the
dividing line between the two regions. EPA believes that dividing the
Panhandle region in this manner may more accurately represent the
natural influences on stream TP concentrations and provide finer
spatial resolution with respect to TP criteria; however, we request
comment on this conclusion.
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\1\ Scott, T.S., 1988, The lithostratigraphy of the Hawthorn
Group (Miocene) of Florida: Florida Geological Survey Bulletin No.
59; 148 p.; Scott, T.S., K.M. Campbell, F.R. Rupert, J.D. Arthur,
T.M. Missimer, J.M. Lloyd, J.W. Yon and J.G. Duncan, 2001, Geologic
map of the state of Florida: Florida Geological Survey Map Series
146; Scott, T.S., 2001, Text to accompany the geologic map of
Florida: Florida Geological Survey Open-File Report 80; 29 p.
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EPA is considering these adjustments in the Panhandle region to
account for natural geological influences on stream phosphorus
concentrations. EPA considered different approaches to classifying
Florida's streams for application of TN criteria, such as the four
Nutrient Watershed Regions discussed in the January 2010 proposal and
two regions as originally suggested by FDEP. However, differences in
the resulting TN criteria based on these stream classification schemes
were minor and the approaches were comparable. Therefore, to assure
consistency and clarity in applicability decisions and implementation,
EPA is also considering using the same revised Panhandle delineation
for stream TN criteria as well as the TP criteria. This consistency in
regionalization for TN and TP provides clarity to the public on which
stream criteria apply at any given location, which can help facilitate
the State's implementation of both stream TN and TP criteria.
EPA also reexamined the watershed delineations of the West Central
and Peninsula regions based on comments and information from FDEP and
others. As a result of this review, EPA has gained greater knowledge of
the watershed boundaries and is considering refining the boundary
delineations accordingly. The result for the West Central region would
be a modified western boundary that shifts from Florida's west coast
shoreline inland to the east as explained in more detail below. EPA
believes that these possible adjustments to the West Central and
Peninsula stream region boundaries more accurately reflect the
watershed boundaries; however, we request comment on this conclusion.
As a result of the new information and possible adjustments to the
proposed stream regionalization approach that are outlined above, EPA
is considering five Nutrient Watershed Regions for deriving TP and TN
criteria for streams. The five Nutrient Watershed Regions would include
a Panhandle West region encompassing Perdido Bay Watershed, Pensacola
Bay Watershed, Choctawhatchee Bay Watershed, St. Andrew Bay Watershed,
and Apalachicola Bay Watershed. It would also include a Panhandle East
region encompassing Apalachee Bay Watershed, and Econfina/Steinhatchee
Coastal Drainage Area. The West Central (Bone Valley) and Peninsula
regions would be revised slightly to more accurately reflect watershed
boundaries (e.g., the Sarasota Bay and Charlotte Harbor Watersheds
would move from the West Central (Bone Valley) to the Peninsula
region). The proposed North Central region encompassing the Suwannee
River Watershed would remain unchanged.
EPA is providing the following information in the docket to
illustrate and delineate the revised Nutrient Watershed Regions under
consideration: 1. Map of revised TN, TP regions, 2. Map of Hawthorne
group overlaid on revised Panhandle regions, 3. GIS shapefile of
revised TN, TP regions, 4. Florida geological information on the
Hawthorne group (see footnote 1).
EPA is also providing additional information in this notice and in
the docket on the TN and TP criteria that are based on the revised
Nutrient Watershed Regions under consideration. Using EPA's previously
proposed approach (75th percentile) and the revised stream regions
discussed in this notice, the TN and TP criteria would be: Panhandle
West--0.84 mg/L and 0.03 mg/L, respectively; Panhandle East--0.77 mg/L
and 0.10 mg/L, respectively; North Central--1.48 mg/L and 0.36 mg/L,
respectively; West Central--1.80 mg/L and 0.73 mg/L, respectively; and
Peninsula--1.20 mg/L and 0.10 mg/L, respectively. To illustrate the
derivation of stream criteria based on the revised regions, EPA has re-
organized the same
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nutrient dataset provided in the proposed rule and is making it
available to the public in the docket for this notice. These data were
organized on the basis of site averages to derive the proposed criteria
outlined above.
At proposal, EPA also requested comment on the benchmark
distribution approach. In response to comments, the Agency is
considering using a combination of the 75th and 90th percentile values
(depending on regions) based on benchmark sites, with additional data
quality screens applied, to establish criteria. EPA is considering the
90th percentile for all regions except the West Central, where the
Agency is considering the 75th percentile due to less data available.
Using the benchmark distribution approach and the revised stream
regions discussed in this notice, the TN and TP criteria would be:
Panhandle West--0.62 mg/L and 0.04 mg/L, respectively; Panhandle East--
0.97 mg/L and 0.11 mg/L, respectively; North Central--1.90 mg/L and
0.35 mg/L, respectively; West Central--1.30 mg/L and 0.35 mg/L,
respectively; and Peninsula--1.67 mg/L and 0.11 mg/L, respectively.
Included in the docket for today's notice is the benchmark dataset
presented at proposal with the additional quality assurance screens
applied, that was used to calculate these values. The stream criteria
using this approach are calculated on the basis of Waterbody
Identifiers (WBIDs) and the derivation is outlined in more detail in
the docket for today's notice. EPA requests comment on this approach.
EPA is soliciting comment on the refined regionalization approach
and criteria described in this supplemental notice. The Agency is
specifically requesting comment on revised stream criteria using EPA's
previously proposed approach (applied to the revised regions) as
outlined above as well as alternative stream criteria based on
utilization of the benchmark distribution approach applied to the
revised regions, also outlined above. EPA will evaluate all data and
information submitted by the close of the public comment period for
this supplemental notice with regard to regionalization and criteria
derivation for Florida's streams.
B. Downstream Protection of Lakes
In its January 2010 FRN, EPA proposed a phosphorus loading model
equation first developed by Vollenweider \2\ to relate a lake TP
concentration criterion to the concentration necessary in incoming
streams to support the lake criterion. EPA proposed to apply the
equation's resulting stream concentration as the applicable criterion
for all stream segments upstream of the lake if those concentrations
were more stringent than the otherwise applicable instream criteria for
the stream segments. EPA mathematically derived this equation, with
allowable input of lake-specific characteristics, to calculate values
intended to serve as protective criteria necessary to assure attainment
and maintenance of the lake numeric nutrient criteria also included in
the proposal (75 FR 4198).
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\2\ Vollenweider, R.A. 1975. Input-output models with special
reference to the phosphorus loading concept in limnology.
Schweizerische Zeitschrift fur Hydrologie. 37:53-84; Vollenweider,
R.A. 1976. Advances in differing critical loading levels for
phosphorus in lake eutrophication. Mem. Ist. Ital. Idrobid. 33:53-
83.
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The proposed Vollenweider model equation requires input of two
lake-specific characteristics: The fraction of inflow due to stream
flow and the hydraulic retention time. Because lake-specific input
values may not always be readily available, EPA provided alternative
preset values for percent contribution from stream flow and hydraulic
retention time that could be used in those instances. 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 they are appropriate and documents
the site-specific values.
EPA requested comment on several technical aspects of this equation
and its application. In addition, EPA requested comment on the
potential to develop a corollary approach for nitrogen. Several
commenters suggested the need for protective TN values to protect
downstream lakes that are nitrogen-limited (such as many of the lakes
in the phosphorus-rich areas of the State). EPA recognized that more
specific information may be readily available for individual lakes that
could allow the use of alternative approaches such as the BATHTUB model
\3\ and requested comment in the January 2010 proposal on the
availability and application of this model. EPA also requested comment
on whether there should be a specific allowance for use of alternative
lake-specific models where demonstrated to be protective and
scientifically defensible based upon current and readily available
data.
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\3\ 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.
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EPA received many comments on this proposed approach for protection
of lakes downstream of rivers and streams. Some felt that that the
Vollenweider equation was overly simplistic to represent all lakes in
Florida and that it does not include the necessary factors to account
for physical, hydrologic, chemical, and biological processes necessary
to determine protective criteria. Comments included a recommendation to
use models that can better represent site-specific conditions, such as
BATHTUB.
BATHTUB is designed to apply empirical eutrophication models to
morphometrically complex lakes and reservoirs. The program performs
steady-state water and nutrient balance calculations, uses spatially
segmented hydraulic networks, and accounts for advective and diffusive
transport of nutrients. BATHTUB predicts nutrient-related water quality
conditions such as total phosphorus, total nitrogen 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 empirically-derived
relationships, BATHTUB inherently accounts for internal loading of
phosphorus from bottom sediments. Additional technical references are
available that describe the model and its applications.\4\
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\4\ 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.; 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.; 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, M.S.
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For the provision of EPA's proposed rule for deriving criteria for
protection of downstream lakes (Sec. 131.43(c)(2)(ii)), EPA is
considering requiring the use of BATHTUB rather than a loading model
equation based on Vollenweider. The rule would therefore require that
the criteria for protection of downstream lakes would be the more
stringent of the instream TP and TN criteria value or the
[[Page 45583]]
concentration of TP and TN derived from application of BATHTUB. The
resulting criteria using BATHTUB could be either more or less stringent
than the criteria derived using Vollenweider, depending on site-
specific lake factors. EPA believes BATHTUB may be more appropriate for
downstream protection value calculations than Vollenweider because
BATHTUB has the capability to represent a greater number of site-
specific variables, which may influence nutrient responses. In
addition, BATHTUB can estimate TN concentrations. As noted above, a
number of commenters observed that a limitation in EPA's original
proposal was that it only addressed TP.
EPA is also considering additional rule language that would
specifically authorize FDEP or EPA to use a model other than BATHTUB
when either determines that it would be appropriate to use another
scientifically defensible technical model or approach that demonstrates
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 more
complex situations and address an even greater degree of site-
specificity.
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.
Additional technical information may be found at http://www.epa.gov/athens/wwqtsc/html/wasp.html.
EPA is considering recommending BATHTUB as the method for
calculating the TN and TP downstream protective values in streams that
flow into lakes because of its ability to incorporate site-specific
factors in estimates, its use of data that may be readily available,
and its ease of use and rapid processing time. BATHTUB has been used to
model nutrients in lakes and reservoirs throughout the United States.
BATHTUB allows for greater site-specificity than the Vollenweider
approach, and input of more local information to calculate
concentrations of both nitrogen and phosphorus in streams that assure
downstream protection of lakes. In certain circumstances, a more
complex model such as WASP may be appropriate, and EPA is considering
and requesting comment on adding specific provisions to allow either
the Agency or FDEP to use an alternative model such as WASP where
greater spatial or temporal detail in model output is called for, or
where water quality considerations that fall outside the scope of
BATHTUB are to be explicitly considered.
EPA is also requesting comment on including a provision in this
section of the rule that would provide that if data are not readily
available to derive a TN or TP downstream protection value using
BATHTUB or another scientifically defensible model, the lake criteria
values for TN and TP would be used as the downstream protection values
where they are more stringent than the instream values. EPA believes
that this approach is protective because the allowable concentration of
nutrients entering the lake would be equal to criteria that are
protective of the lake water itself; however, this approach may result
in the application of more stringent criteria in the streams entering
the lake than would be calculated using BATHTUB or another
scientifically defensible model if site-specific data were available.
EPA is soliciting comment on the approaches to protect downstream
lakes described in this supplemental notice. EPA will evaluate all data
and information submitted by the close of the public comment period for
this supplemental notice with regard to nutrient criteria to protect
downstream lakes in Florida.
Dated: July 29, 2010.
Peter S. Silva,
Assistant Administrator for Water.
[FR Doc. 2010-19140 Filed 7-30-10; 4:15 pm]
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