[Federal Register Volume 75, Number 16 (Tuesday, January 26, 2010)]
[Proposed Rules]
[Pages 4174-4226]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2010-1220]



[[Page 4173]]

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

Part III





Environmental Protection Agency





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



40 CFR Part 131



Water Quality Standards for the State of Florida's Lakes and Flowing 
Waters; Proposed Rule

Federal Register / Vol. 75 , No. 16 / Tuesday, January 26, 2010 / 
Proposed Rules

[[Page 4174]]


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

ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 131

[EPA-HQ-OW-2009-0596; FRL-9105-1]
RIN 2040-AF11


Water Quality Standards for the State of Florida's Lakes and 
Flowing Waters

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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

SUMMARY: The Environmental Protection Agency (EPA) is proposing numeric 
nutrient water quality criteria to protect aquatic life in lakes and 
flowing waters, including canals, within the State of Florida and 
proposing regulations to establish a framework for Florida to develop 
``restoration standards'' for impaired waters. On January 14, 2009, EPA 
made a determination under section 303(c)(4)(B) of the Clean Water Act 
(``CWA'' or ``the Act'') that numeric nutrient water quality criteria 
for lakes and flowing waters and for estuaries and coastal waters are 
necessary for the State of Florida to meet the requirements of CWA 
section 303(c). Section 303(c)(4) of the CWA requires the Administrator 
to promptly prepare and publish proposed regulations setting forth new 
or revised water quality standards (``WQS'' or ``standards'') when the 
Administrator, or an authorized delegate of the Administrator, 
determines that such new or revised WQS are necessary to meet 
requirements of the Act. This proposed rule fulfills EPA's obligation 
under section 303(c)(4) of the CWA to promptly propose criteria for 
Florida's lakes and flowing waters.

DATES: Comments must be received on or before March 29, 2010.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-HQ-OW-
2009-0596, by one of the following methods:
    1. www.regulations.gov: Follow the online instructions for 
submitting comments.
    2. E-mail: <a href="/cdn-cgi/l/email-protection#620d154f060d01090716220712034c050d14"><span class="__cf_email__" data-cfemail="2d425a0049424e4648596d485d4c034a425b">[email protected]</span></a>.
    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 
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 www.regulations.gov or e-mail. 
The 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 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 
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 www.regulations.gov or in hard copy at a docket facility. The Office 
of Water (OW) Docket Center is open from 8:30 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.
    Public hearings will be held in the following cities in Florida: 
Tallahassee, Orlando, and West Palm Beach. The public hearing in 
Tallahassee is scheduled for Tuesday, February 16, 2010 and will be 
held from 1 p.m. to 5 p.m. and 7 p.m. to 10 p.m. at the Holiday Inn 
Capitol East, 1355 Apalachee Parkway, Tallahassee, FL 32301. The public 
hearing in Orlando is scheduled for Wednesday, February 17, 2010 and 
will be held from 1 p.m. to 5 p.m. and 7 p.m. to 10 p.m. at the Crowne 
Plaza Orlando Universal, 7800 Universal Boulevard, Orlando, FL 32819. 
The public hearing in West Palm Beach is scheduled for Thursday, 
February 18, 2010 and will be held from 1 p.m. to 5 p.m. and 7 p.m. to 
10 p.m. at the Holiday Inn Palm Beach Airport, 1301 Belvedere Road, 
West Palm Beach, FL 33405. If you need a sign language interpreter at 
any of these hearings, you should contact Sharon Frey at 202-566-1480 
or <a href="/cdn-cgi/l/email-protection#bed8ccdbc790cdd6dfccd1d0fedbcedf90d9d1c8"><span class="__cf_email__" data-cfemail="96f0e4f3efb8e5fef7e4f9f8d6f3e6f7b8f1f9e0">[email protected]</span></a> at least ten business days prior to the meetings 
so that appropriate arrangements can be made. For further information, 
including registration information, please refer to the following Web 
site: http://www.epa.gov/waterscience/standards/rules/florida/.

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: <a href="/cdn-cgi/l/email-protection#3f4c5e53495e4b5a4d4d5e115b5e51565a53535a7f5a4f5e11585049"><span class="__cf_email__" data-cfemail="b1c2d0ddc7d0c5d4c3c3d09fd5d0dfd8d4ddddd4f1d4c1d09fd6dec7">[email protected]</span></a>.

SUPPLEMENTARY INFORMATION: This supplementary information section is 
organized as follows:

Table of Contents

I. General Information
    A. Executive Summary
    B. What Entities May Be Affected by This Rule?
    C. What Should I Consider as I Prepare My Comments for EPA?
    D. How Can I Get Copies of This Document and Other Related 
Information?
II. Background
    A. Nutrient Pollution
    B. Statutory and Regulatory Background
    C. Water Quality Criteria
    D. Agency Determination Regarding Florida
III. Proposed Numeric Nutrient Criteria for the State of Florida's 
Lakes and Flowing Waters
    A. General Information
    B. Proposed Numeric Nutrient Criteria for the State of Florida's 
Lakes
    C. Proposed Numeric Nutrient Criteria for the State of Florida's 
Rivers and Streams

[[Page 4175]]

    D. Proposed Numeric Nutrient Criteria for the State of Florida's 
Springs and Clear Streams
    E. Proposed Numeric Nutrient Criteria for South Florida Canals
    F. Comparison Between EPA's and Florida DEP's Proposed Numeric 
Nutrient Criteria for Florida's Lakes and Flowing Waters
    G. Applicability of Criteria When Final
IV. Under What Conditions Will Federal Standards Be Either Not 
Finalized or Withdrawn?
V. Alternative Regulatory Approaches and Implementation Mechanisms
    A. Designating Uses
    B. Variances
    C. Site-Specific Criteria
    D. Compliance Schedules
VI. Proposed Restoration Water Quality Standards (WQS) Provision
VII. Statutory and Executive Order Reviews
    A. Executive Order 12866: Regulatory Planning and Review
    B. Paperwork Reduction Act
    C. Regulatory Flexibility Act
    D. Unfunded Mandates Reform Act
    E. Executive Order 13132 (Federalism)
    F. Executive Order 13175 (Consultation and Coordination With 
Indian Tribal Governments)
    G. Executive Order 13045 (Protection of Children From 
Environmental Health and Safety Risks)
    H. Executive Order 13211 (Actions That Significantly Affect 
Energy Supply, Distribution, or Use)
    I. National Technology Transfer Advancement Act of 1995
    J. Executive Order 12898 (Federal Actions To Address 
Environmental Justice in Minority Populations and Low-Income 
Populations)

I. General Information

A. Executive Summary

    Excess loadings of nitrogen and phosphorus, commonly referred to as 
nutrient pollution, are one of the most prevalent causes of water 
quality impairment in the United States. Anthropogenic nitrogen and 
phosphorus over-enrichment in many of the Nation's waters is a 
widespread, persistent, and growing problem. Nutrient pollution can 
significantly impact aquatic life and long-term ecosystem health, 
diversity, and balance. More specifically, high nitrogen and phosphorus 
loadings, or nutrient pollution, result in harmful algal blooms (HABs), 
reduced spawning grounds and nursery habitats, fish kills, and oxygen-
starved hypoxic or ``dead'' zones. Public health concerns related to 
nutrient pollution include impaired drinking water sources, increased 
exposure to toxic microbes such as cyanobacteria, and possible 
formation of disinfection byproducts in drinking water, some of which 
have been associated with serious human illnesses such as bladder 
cancer. Nutrient problems can exhibit themselves locally or much 
further downstream leading to degraded lakes, reservoirs, and 
estuaries, and to hypoxic zones where fish and aquatic life can no 
longer survive.
    In the State of Florida, nutrient pollution has contributed to 
severe water quality degradation. Based upon waters assessed and 
reported in the 2008 Integrated Water Quality Assessment for Florida, 
approximately 1,000 miles of rivers and streams, 350,000 acres of 
lakes, and 900 square miles of estuaries are known to be impaired for 
nutrients by the State.\1\ The actual number of stream miles, lake 
acres, and estuarine square miles of waters impaired for nutrients in 
Florida may be higher, as many waters currently are classified as 
``unassessed.''
---------------------------------------------------------------------------

    \1\ Florida Department of Environmental Protection. 2008. 
Integrated Water Quality Assessment for Florida: 2008 305(b) Report 
and 303(d) List Update, p. 67.
---------------------------------------------------------------------------

    The challenge of nutrient pollution has been a top priority for 
Florida's Department of Environmental Protection (FDEP). Over the past 
decade or more, FDEP has spent over 20 million dollars collecting and 
analyzing data on the relationship between phosphorus, nitrogen, and 
nitrite-nitrate concentrations and the biological health of aquatic 
systems. Moreover, Florida is one of the few states that has in place a 
comprehensive framework of accountability that applies to both point 
and nonpoint sources and provides the enforceable authority to address 
nutrient reductions in impaired waters based upon the establishment of 
site-specific total maximum daily loads (TMDLs).
    Despite FDEP's intensive efforts to diagnose and control nutrient 
pollution, substantial water quality degradation from nutrient over-
enrichment remains a significant problem. On January 14, 2009, EPA 
determined under CWA section 303(c)(4)(B) that new or revised WQS in 
the form of numeric nutrient water quality criteria are necessary to 
meet the requirements of the CWA in the State of Florida. The Agency 
considered (1) the State's documented unique and threatened ecosystems, 
(2) the high number of impaired waters due to existing nutrient 
pollution, and (3) the challenge associated with growing nutrient 
pollution resulting from expanding urbanization, continued agricultural 
development, and a significantly increasing population that is expected 
to grow 75% between 2000 to 2030.\2\ EPA also reviewed the State's 
regulatory nutrient accountability system, which represents an 
impressive synthesis of technology-based standards, point source 
control authority, and authority to establish enforceable controls for 
nonpoint source activities. However, the significant challenge faced by 
the water quality components of this system is its dependence upon an 
approach involving resource-intensive and time-consuming site-specific 
data collection and analysis to interpret non-numeric narrative 
nutrient criteria. EPA determined that Florida's reliance on a case-by-
case interpretation of its narrative nutrient criterion in implementing 
an otherwise comprehensive water quality framework of enforceable 
accountability was insufficient to ensure protection of applicable 
designated uses. As part of the Agency's determination, EPA indicated 
that it expected to propose numeric nutrient criteria for lakes and 
flowing waters within 12 months, and for estuarine and coastal waters 
within 24 months, of the January 14, 2009 determination.
---------------------------------------------------------------------------

    \2\ http://www.census.gov/population/projections/SummaryTabA1.pdf.
---------------------------------------------------------------------------

    On August 19, 2009, EPA entered into a phased Consent Decree with 
Florida Wildlife Federation, Sierra Club, Conservancy of Southwest 
Florida, Environmental Confederation of Southwest Florida, and St. 
Johns Riverkeeper, committing to sign a proposed rule setting forth 
numeric nutrient criteria for lakes and flowing waters in Florida by 
January 14, 2010, and for Florida's estuarine and coastal waters by 
January 14, 2011, unless Florida submits and EPA approves State numeric 
nutrient criteria before EPA's proposal. The phased Consent Decree also 
provides that EPA issue a final rule by October 15, 2010 for lakes and 
flowing water, and by October 15, 2011 for estuarine and coastal 
waters, unless Florida submits and EPA approves State numeric nutrient 
criteria before a final EPA action.
    Accordingly, this proposal is part of a phased rulemaking process 
in which EPA will propose and take final action in 2010 on numeric 
nutrient criteria for lakes and flowing waters and for estuarine and 
coastal waters in 2011. The two phases of this rulemaking are linked 
because nutrient pollution in Florida's rivers and streams affects not 
only instream aquatic conditions but also downstream estuarine and 
coastal waters ecosystem conditions. The Agency could have waited to 
propose estuarine and coastal downstream protection criteria values for 
rivers and streams as part of the second phase of this rulemaking 
process. However, the substantial data, peer-reviewed methodologies, 
and extensive scientific

[[Page 4176]]

analyses available to and conducted by the Agency to date indicate that 
numeric nutrient water quality criteria for estuarine and coastal 
waters, when proposed and finalized in 2011, may result in the need for 
more stringent rivers and streams criteria to ensure protection of 
downstream water quality, particularly for the nitrogen component of 
nutrient pollution. Therefore, considering the numerous requests for 
the Agency to share its analysis and scientific and technical 
conclusions at the earliest possible opportunity to allow for full 
review and comment, EPA is including downstream protection values for 
total nitrogen (TN) as proposed criteria for rivers and streams to 
protect the State's estuaries and coastal waters in this notice.
    As described in more detail below and in the technical support 
document accompanying this notice, these proposed nitrogen downstream 
protection values are based on substantial data, thorough scientific 
analysis, and extensive technical evaluation. However, EPA recognizes 
that additional data and analysis may be available, including data for 
particular estuaries, to help inform what numeric nutrient criteria are 
necessary to protect Florida's waters, including downstream lakes and 
estuaries. EPA also recognizes that substantial site-specific work has 
been completed for a number of these estuaries. This notice and the 
proposed downstream protection values are not intended to address or be 
interpreted as calling into question the utility and protectiveness of 
these site-specific analyses. Rather, the proposed values represent the 
output of a systematic and scientific approach that was developed to be 
generally applicable to all flowing waters in Florida that terminate in 
estuaries for the purpose of ensuring the protection of downstream 
estuaries. EPA is interested in obtaining feedback at this time on this 
systematic and scientific approach. EPA is also interested in feedback 
regarding site-specific analyses for particular estuaries that should 
be used instead of this general approach for establishing final values. 
The Agency further recognizes that the proposed values in this notice 
will need to be considered in the context of the Agency's numeric 
nutrient criteria for estuarine and coastal waters scheduled for 
proposal in January of 2011.
    Regarding the criteria for flowing waters for protection of 
downstream lakes and estuaries, at this time, EPA intends to take final 
action on the criteria for protection of downstream lakes as part of 
the first phase of this rulemaking (by October 15, 2010) and to 
finalize downstream protection values in flowing waters as part of the 
second phase of this rulemaking process (by October 15, 2011) in 
coordination with the proposal and finalization of numeric nutrient 
criteria for estuarine and coastal waters in 2011. However, if 
comments, data and analyses submitted as a result of this proposal 
support finalizing these values sooner, by October 2010, EPA may choose 
to proceed in this manner. To facilitate this process, EPA requests 
comments and welcomes thorough evaluation on the technical and 
scientific basis of these proposed downstream protection values, as 
well as information on estuaries where site-specific analyses should be 
used, as part of the broader comment and evaluation process that this 
proposal initiates.
    In accordance with the terms of EPA's January 14, 2009 
determination and the Consent Decree, EPA is proposing numeric nutrient 
criteria for Florida's lakes and flowing waters which include the 
following four water body types: Lakes, streams, springs and clear 
streams, and canals in south Florida. In developing this proposal, EPA 
worked closely with FDEP staff to review and analyze the State's 
extensive dataset of nutrient-related measurements as well as its 
analysis of stressor-response relationships and benchmark or modified-
reference conditions. EPA also conducted further analyses and modeling, 
in addition to requesting an independent external peer review of the 
core methodologies and approaches that support this proposal.
    For lakes, EPA is proposing a classification scheme using color and 
alkalinity based upon substantial data that show that lake color and 
alkalinity play an important role in the degree to which TN and total 
phosphorus (TP) concentrations result in a biological response such as 
elevated chlorophyll a levels. EPA found that correlations between 
nutrients and biological response parameters in the different types of 
lakes in Florida were sufficiently robust, combined with additional 
lines of evidence, to support stressor-response criteria development 
for Florida's lakes. The Agency is also proposing an accompanying 
supplementary analytical approach that the State can use to adjust TN 
and TP criteria for a particular lake within a certain range where 
sufficient data on long-term ambient TN and TP levels are available to 
demonstrate that protective chlorophyll a criteria for a specific lake 
will still be maintained and attainment of the designated use will be 
assured. This information is presented in more detail in Section III.B 
below.
    Regarding numeric nutrient criteria for streams and rivers, EPA 
considered the extensive work of FDEP to analyze the relationship 
between TN and TP levels and biological response in streams and rivers. 
EPA found that relationships between nutrients and biological response 
parameters in rivers and streams were affected by many factors that 
made derivation of a quantitative relationship between chlorophyll a 
levels and nutrients in streams and rivers difficult to establish in 
the same manner as EPA did for lakes (i.e., stressor-response 
relationship). EPA considered an alternative methodology that evaluated 
a combination of biological information and data on the distribution of 
nutrients in a substantial number of healthy stream systems. Based upon 
a technical evaluation of the significant available data on Florida 
streams and related scientific analysis, the Agency concluded that 
reliance on a statistical distribution methodology was a stronger and a 
more sound approach for deriving TN and TP criteria in streams and 
rivers. This information is presented in more detail in Section III.C 
below.
    In developing these proposed numeric nutrient criteria for rivers 
and streams, EPA also evaluated their effectiveness for assuring the 
protection of downstream lake and estuary designated uses 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. For rivers and streams in Florida, EPA must ensure, to the 
extent that available science allows, that its nutrient criteria take 
into account the impact of near-field nutrient loads on aquatic life in 
downstream lakes and estuaries. EPA currently has evaluated the 
protectiveness of its rivers and streams TP criteria for lake 
protection and also the protectiveness of its rivers and streams TN 
criteria for 16 out of 26 of Florida's downstream estuaries using 
scientifically sound approaches for both estimating protective loads 
and deriving concentration-based upstream values. Of the ten downstream 
estuaries not completely evaluated to date, seven are in south Florida 
and receive TN loads from highly managed canals and waterways and three 
are in low lying areas of central Florida.
    As noted above, EPA used best available science and data related to 
downstream waters and found that there are cases where the nutrient 
criteria EPA is proposing to protect instream aquatic life may not be 
stringent enough to ensure protection of aquatic life in certain 
downstream lakes and estuaries. Accordingly, EPA is also proposing an

[[Page 4177]]

equation that would be used to adjust stream and river TP criteria to 
protect downstream lakes and a different methodology to adjust TN 
criteria for streams and rivers to ensure protection of downstream 
estuaries. These approaches as reflected in these proposed regulations 
and the revised criteria that would result from adjusting TN criteria 
for streams and rivers to ensure protection of downstream estuaries, 
based on certain assumptions, are detailed in Section III.C(6)(b) 
below. The Agency specifically requests comment on the available 
information, analysis, and modeling used to support the approaches EPA 
is proposing for addressing downstream impacts of TN and TP. EPA also 
invites additional stakeholder comment, data, and analysis on 
alternative technically-based approaches that would support the 
development of numeric nutrient WQS, or some other scientifically 
defensible approach, for protection of downstream waters. To the degree 
that substantial data and analyses are submitted that support a 
significant revision to downstream protection values for TN outlined in 
Section III.C(6)(b) below, EPA would intend to issue a supplemental 
Federal Register Notice of Data Availability (NODA) to present the 
additional data and supplemental analyses and solicit further comment 
and input. EPA anticipates obtaining the necessary data and information 
to compute downstream protection values for TP loads for many estuarine 
water bodies in Florida in 2010 and will also make this additional 
information available by issuing a supplemental Federal Register NODA.
    Regarding numeric nutrient criteria for springs and clear streams, 
EPA is proposing a nitrate-nitrite criterion for springs and clear 
streams based on experimental laboratory data and field evaluations 
that document the response of nuisance algae and periphyton to nitrate-
nitrite concentrations. This criterion is explained in more detail in 
Section III.D below.
    For canals in south Florida, EPA is proposing a statistical 
distribution approach similar to its approach for rivers and streams, 
and based on sites meeting designated uses with respect to nutrients 
identified in four canal regions to best represent the necessary 
criteria to protect these highly managed water bodies. This approach is 
presented in more detail in Section III.E below. The Agency has also 
considered several alternative approaches to developing numeric 
nutrient criteria for canals and these are described, as well, for 
public comment and response.
    Stakeholders have expressed concerns that numeric nutrient criteria 
must be scientifically sound. Under the Clean Water Act and EPA's 
implementing regulations, numeric nutrient standards must protect the 
designated use of a water (as well as ensure protection of downstream 
uses) and must be based on sound scientific rationale. In the case of 
Florida, EPA and FDEP scientists completed a substantial body of 
scientific work; EPA believes that these proposed criteria clearly meet 
the regulatory standards of protection and that they are clearly based 
on a sound scientific rationale.
    Separate from and in addition to proposing numeric nutrient 
criteria, EPA is also proposing a new WQS regulatory tool for Florida, 
referred to as ``restoration WQS'' for impaired waters. This tool will 
enable Florida to set incremental water quality targets (uses and 
criteria) for specific pollutant parameters while at the same time 
retaining protective criteria for all other parameters to meet the full 
aquatic life use. The goal is to provide a challenging but realistic 
incremental framework in which to establish appropriate control 
measures. This provision will allow Florida to retain full aquatic life 
protection (uses and criteria) for its water bodies while establishing 
a transparent phased WQS process that would result in planned 
implementation of enforceable measures and requirements to improve 
water quality over a specified time period to ultimately meet the long-
term designated aquatic life use. The phased numeric standards would be 
included in Florida's water quality regulations during the restoration 
period. This proposed regulatory tool is discussed in more detail in 
Section VI below.
    Finally, EPA is including in this notice a proposed approach for 
deriving Federal site-specific alternative criteria (SSAC) based upon 
State submissions of scientifically defensible recalculations that meet 
the requirements of CWA section 303(c). TMDL targets submitted to EPA 
by the State for consideration as new or revised WQS could be reviewed 
under this SSAC process. This proposed approach is discussed in more 
detail in Section V.C below.
    Overall, EPA is soliciting comments and data regarding EPA's 
proposed criteria for lakes and flowing waters, the derivation of these 
criteria, the protectiveness of the streams and rivers criteria for 
downstream waters, and all associated alternative options and 
methodologies discussed in this proposed rulemaking.

B. What Entities May Be Affected by This Rule?

    Citizens concerned with water quality in Florida may be interested 
in this rulemaking. Entities discharging nitrogen or phosphorus to 
lakes and flowing waters of Florida could be indirectly affected by 
this rulemaking because WQS are used in determining National Pollutant 
Discharge Elimination System (``NPDES'') permit limits. Stakeholders in 
Florida facing obstacles in immediately achieving full aquatic life 
protection in impaired waters may be interested in the restoration 
standards concept outlined in this rulemaking. Categories and entities 
that may ultimately be affected include:

------------------------------------------------------------------------
                                             Examples of potentially
                Category                        affected entities
------------------------------------------------------------------------
Industry...............................  Industries discharging
                                          pollutants to lakes and
                                          flowing waters in the State of
                                          Florida.
Municipalities.........................  Publicly-owned treatment works
                                          discharging pollutants to
                                          lakes and flowing waters in
                                          the State of Florida.
Stormwater Management Districts........  Entities responsible for
                                          managing stormwater runoff in
                                          Florida.
------------------------------------------------------------------------

    This table is not intended to be exhaustive, but rather provides a 
guide for entities that may be directly or indirectly affected by this 
action. This table lists the types of entities of which EPA is now 
aware that potentially could be affected by this action. Other types of 
entities not listed in the table could also be affected, such as 
nonpoint source contributors to nutrient pollution in Florida's waters. 
Any parties or entities conducting activities within watersheds of the 
Florida waters covered by this rule, or who rely on, depend upon, 
influence, or contribute to the water quality of the lakes and flowing 
waters of Florida, might be affected by this rule. To determine whether 
your facility or activities may be affected by this action, you should 
examine this proposed rule. If you have questions regarding the 
applicability of this action to a particular entity, consult the person 
listed in the preceding FOR FURTHER INFORMATION CONTACT section.

C. 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

[[Page 4178]]

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 organize comments by referencing a Code of Federal 
Regulations (CFR) part or section number.
    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. If you estimate potential costs or burdens, explain how you 
arrived at your estimate in sufficient detail to allow for it to be 
reproduced.
    6. Provide specific examples to illustrate your concerns, and 
suggest alternatives.
    7. Make sure to submit your comments by the comment period deadline 
identified.

D. 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.D(1).

II. Background

A. Nutrient Pollution

1. What Is Nutrient Pollution?
    Excess anthropogenic concentrations of nitrogen (typically in 
oxidized, inorganic forms, such as nitrate) \3\ and phosphorus 
(typically as phosphate), commonly referred to as nutrient pollution, 
in surface waters can result in excessive algal and aquatic plant 
growth, referred to as eutrophication.\4\ One impact associated with 
eutrophication is low dissolved oxygen, due to decomposition of the 
aquatic plants and algae when these plants and algae die. As noted 
above, high nitrogen and phosphorus loadings also result in HABs, 
reduced spawning grounds and nursery habitats for aquatic life, and 
fish kills. Public health concerns related to eutrophication include 
impaired drinking water sources, increased exposure to toxic microbes 
such as cyanobacteria, and possible formation of disinfection 
byproducts in drinking water, some of which have been associated with 
serious human illnesses such as bladder cancer.<SUP>5 6</SUP> Nutrient 
problems can manifest locally or much further downstream in lakes, 
reservoirs, and estuaries.
---------------------------------------------------------------------------

    \3\ To be used by living organisms, nitrogen gas must be fixed 
into its reactive forms; for plants, either nitrate or ammonia.
    \4\ Eutrophication is defined as an increase in organic carbon 
to an aquatic ecosystem caused by primary productivity stimulated by 
excess nutrients--typically compounds containing nitrogen or 
phosphorus. Eutrophication can adversely affect aquatic life, 
recreation, and human health uses of waters.
    \5\ Villanueva, C.M. et al., 2006. Bladder Cancer and Exposure 
to Water Disinfection By-Products through Ingestion, Bathing, 
Showering, and Swimming in Pools. American Journal of Epidemiology, 
165(2):148-156.
    \6\ U.S. EPA. 2009. What Is in Our Drinking Water. United States 
Environmental Protection Agency, Office of Research and Development. 
http://www.epa.gov/extrmurl/research/process/drinkingwater.html. 
Accessed December 2009.
---------------------------------------------------------------------------

    Excess nutrients in water bodies come from many sources, which can 
be grouped into five major categories: (1) Sources associated with 
urban land use and development, (2) municipal and industrial waste 
water discharge, (3) row crop agriculture, (4) animal husbandry, and 
(5) atmospheric deposition that may be increased by production of 
nitrogen oxides in electric power generation and internal combustion 
engines. These sources contribute significant loadings of nitrogen and 
phosphorus to surface waters causing major impacts to aquatic 
ecosystems and significant imbalances in the natural populations of 
flora and fauna.\7\
---------------------------------------------------------------------------

    \7\ National Research Council, 2000. Clean Coastal Waters: 
Understanding and Reducing the Effects of Nutrient Pollution. Report 
prepared by the Ocean Study Board and Water Science and Technology 
Board, Commission on Geosciences, Environment and Resources, 
National Resource Council. National Academy Press, Washington, DC; 
Howarth, R.W., A. Sharpley, and D. Walker. 2002. Sources of nutrient 
pollution to coastal waters in the United States: Implications for 
achieving coastal water quality goals. Estuaries. 25(4b):656-676; 
Smith, V.H. 2003. Eutrophication of freshwater and coastal marine 
ecosystems. Environ. Sci. and Poll. Res. 10(2):126-139; Dodds, W.K., 
W.W. Bouska, J.L. Eitzmann, T.J. Pilger, K.L. Pitts, A.J. Riley, 
J.T. Schloesser, and D.J. Thornbrugh. 2009. Eutrophication of U.S. 
freshwaters: Analysis of potential economic damages. Environ. Sci. 
Tech.. 43(1):12-19.
---------------------------------------------------------------------------

2. Adverse Impacts of Nutrient Pollution on Aquatic Life, Human Health, 
and the Economy
    To protect aquatic life, EPA regulates pollutants that have adverse 
effects on aquatic life. For most pollutants, these effects are 
typically negative impacts on growth, reproduction, and survival. As 
previously noted, excess nutrients can lead to increases in algal and 
other aquatic plant growth, including toxic algae that can result in 
HABs. Increases in algal and aquatic plant growth provide excess 
organic matter in a water body and can contribute to subsequent 
degradation of aquatic communities, human health impacts, and 
ultimately economic impacts.
    Fish, shellfish, and wildlife require clean water for survival. 
Changes in the environment resulting from elevated nutrient levels 
(such as algal blooms, toxins from HABs, and hypoxia/anoxia) can cause 
a variety of effects. When excessive nutrient loads change a water 
body's algae and plant species, the change in habitat and available 
food resources can induce changes affecting an entire food chain. Algal 
blooms block

[[Page 4179]]

sunlight that submerged grasses need to grow, leading to a decline of 
seagrass beds and decreased habitat for juvenile organisms. Algal 
blooms can also increase turbidity and impair the ability of fish and 
other aquatic life to find food.\8\ Algae can also damage or clog the 
gills of fish and invertebrates.\9\
---------------------------------------------------------------------------

    \8\ Hauxwell, J. C. Jacoby, T. Frazer, and J. Stevely. 2001. 
Nutrients and Florida's Coastal Waters. Florida Sea Grant.
    \9\ NOAA. 2009. Harmful Algal Blooms: Current Programs Overview. 
National Oceanic and Atmospheric Administration. http://www.cop.noaa.gov/stressors/extremeevents/hab/welcome.html. Accessed 
December 2009.
---------------------------------------------------------------------------

    HABs can form toxins that cause illness or death for some animals. 
Some of the more commonly affected animals include sea lions, turtles, 
seabirds, dolphins, and manatees.\10\ More than 50% of unusual marine 
mortality events may be associated with HABs.\11\ Lower level 
consumers, such as small fish or shellfish, may not be harmed by algal 
toxins, but they bioaccumulate toxins, causing higher exposures for 
higher level consumers (such as larger predator fish), resulting in 
health impairments and possibly death.<SUP>12 13</SUP>
---------------------------------------------------------------------------

    \10\ NOAA. 2009. Harmful Algal Blooms: Current Programs 
Overview. National Oceanic and Atmospheric Administration. http://www.cop.noaa.gov/stressors/extremeevents/hab/welcome.html. Accessed 
December 2009.
    \11\ WHOI. 2008. HAB Impacts on Wildlife. Woods Hole 
Oceanographic Institution. http://www.whoi.edu/redtide/page.do?pid=9682. Accessed December 2009.
    \12\ WHOI. 2008. Marine Mammals. Woods Hole Oceanographic 
Institution. http://www.whoi.edu/redtide/page.do?pid=14215. Accessed 
December 2009.
    \13\ WHOI. 2008. HAB Impacts on Wildlife. Woods Hole 
Oceanographic Institution. http://www.whoi.edu/redtide/page.do?pid=9682. Accessed December 2009.
---------------------------------------------------------------------------

    There are many examples of HAB toxins significantly affecting 
marine animals. For example, between March and April 2003, 107 
bottlenose dolphins (Tursiops truncatus) died, along with hundreds of 
fish and marine invertebrates, along the Florida Panhandle.\14\ High 
levels of brevetoxin (a neurotoxin), produced by a harmful species of 
dinoflagellate (a type of algae), were measured in all of the stranded 
dolphins examined, as well as in their fish prey.\15\
---------------------------------------------------------------------------

    \14\ WHOI. 2008. Marine Mammals. Woods Hole Oceanographic 
Institution. http://www.whoi.edu/redtide/page.do?pid=14215. Accessed 
December 2009.
    \15\ WHOI. 2008. Marine Mammals. Woods Hole Oceanographic 
Institution. http://www.whoi.edu/redtide/page.do?pid=14215. Accessed 
December 2009.
---------------------------------------------------------------------------

    In freshwater, cyanobacteria can produce toxins that have been 
implicated as the cause of a large number of fish and bird mortalities. 
These toxins have also been tied to the death of pets and livestock 
that may be exposed through drinking contaminated water or grooming 
themselves after bodily exposure.\16\ A recent study showed that at 
least one type of cyanobacteria has been linked to cancer and tumor 
growth in animals.\17\
---------------------------------------------------------------------------

    \16\ WHOI. 2008. HAB Impacts on Wildlife. Woods Hole 
Oceanographic Institution. http://www.whoi.edu/redtide/page.do?pid=9682. Accessed December 2009.
    \17\ Falconer, I.R., A.R. Humpage. 2005. Health Risk Assessment 
of Cyanobacterial (Blue-green Algal) Toxins in Drinking Water. Int. 
J. Environ. Res. Public Health. 2(1): 43-50.
---------------------------------------------------------------------------

    Excessive algal growth contributes to increased oxygen consumption 
associated with decomposition, potentially reducing oxygen to levels 
below that needed for aquatic life to survive and 
flourish.<SUP>18 19</SUP> Low oxygen, or hypoxia, often occurs in 
episodic ``events,'' which sometimes develop overnight. Mobile species, 
such as adult fish, can sometimes survive by moving to areas with more 
oxygen. However, migration to avoid hypoxia depends on species 
mobility, availability of suitable habitat, and adequate environmental 
cues for migration. Less mobile or immobile species, such as oysters 
and mussels, cannot move to avoid low oxygen and are often killed 
during hypoxic events.\20\ While certain mature aquatic animals can 
tolerate a range of dissolved oxygen levels that occur in the water, 
younger life stages of species like fish and shellfish often require 
higher levels of oxygen to survive.\21\ Sustained low levels of 
dissolved oxygen cause a severe decrease in the amount of aquatic life 
in hypoxic zones and affect the ability of aquatic organisms to find 
necessary food and habitat. In extreme cases, anoxic conditions occur 
when there is a complete lack of oxygen. Very few organisms can live 
without oxygen (for example some microbes), hence these areas are 
sometimes referred to as dead zones.\22\
---------------------------------------------------------------------------

    \18\ NOAA. 2009. Harmful Algal Blooms: Current Programs 
Overview. National Oceanic and Atmospheric Administration. http://www.cop.noaa.gov/stressors/extremeevents/hab/welcome.html. Accessed 
December 2009.
    \19\ USGS. 2009. Hypoxia. U.S. Geological Survey. http://toxics.usgs.gov/definitions/hypoxia.html. Accessed December 2009.
    \20\ ESA. 2009. Hypoxia. Ecological Society of America. http://www.esa.org/education_diversity/pdfDocs/hypoxia.pdf. Accessed 
December 2009.
    \21\ USEPA. 2000. Ambient Aquatic Life Water Quality Criteria 
for Dissolved Oxygen (Saltwater): Cape Cod to Cape Hattaras. 
Environmental Protection Agency, Office of Water, Washington DC PA-
822-R-00-012.
    \22\ Ecological Society of America. 2009. Hypoxia. Ecological 
Society of America, Washington, DC. http://www.esa.org/education/edupdfs/hypoxia.pdf. Accessed December 2009.
---------------------------------------------------------------------------

    Primary impacts to humans result directly from elevated nutrient 
pollution levels and indirectly from the subsequent water body changes 
that occur from increased nutrients (such as algal blooms and toxins). 
Direct impacts include effects on human health through drinking water 
or consuming toxic shellfish. Indirect impacts include restrictions on 
recreation (such as boating, swimming, and kayaking). Algal blooms can 
prevent opportunities to swim and engage in other types of recreation. 
In areas where recreation is determined to be unsafe because of algal 
blooms, warning signs are often posted to discourage human use of the 
waters.
    Highly elevated nitrogen levels, in the form of nitrate, in 
drinking water supplies and private wells can cause methemoglobinemia 
(blue baby syndrome, which refers to high levels of nitrate in a baby's 
blood that reduce the blood's ability to deliver oxygen to the skin and 
organs resulting in a bluish tinge to the skin; in severe cases 
methemoglobinemia can lead to coma and death).\23\ Monitoring of 
Florida Public Water Supplies from 2004-2007 indicates that violations 
of nitrate maximum contaminant levels (MCL) ranged from 34-40 
violations annually.\24\ In addition, in the predominantly agricultural 
regions of Florida, of 3,949 drinking water wells analyzed for nitrate 
by the Florida Department of Agriculture and Consumer Services, (FDACS) 
and the FDEP, 2,483 (63%) contained detectable nitrate and 584 wells 
(15%) contained nitrate above the U.S. EPA MCL. Of the 584 wells 
statewide that exceeded the MCL, 519 were located in the Central 
Florida Ridge citrus growing region, encompassed primarily by Lake, 
Polk and Highland Counties.\25\ Human health can also be impacted by 
disinfection byproducts formed when disinfectants (such as chlorine) 
used to treat drinking water react with organic carbon (from the algae 
in source waters). Some disinfection byproducts have been linked to 
rectal, bladder, and colon cancers; reproductive health risks; and 
liver, kidney, and central nervous

[[Page 4180]]

system problems.<SUP>26 27</SUP> Humans can also be impacted by 
accidentally ingesting toxins, resulting from toxic algal blooms in 
water, while recreating or by consuming drinking water that still 
contains toxins despite treatment. For example, cyanobacteria toxins 
can sometimes pass through the normal water treatment process.\28\ 
After consuming seafood tainted by toxic HABs, humans can develop 
gastrointestinal distress, memory loss, disorientation, confusion, and 
even coma and death in extreme cases. Some toxins only require a small 
dose to cause illness or death.\29\ EPA expects that by addressing 
protection of aquatic life uses through the application of the proposed 
numeric nutrient criteria in this rulemaking, risks to human health 
will also be alleviated, as nutrient levels that represent a balance of 
natural populations of flora and fauna will not produce HABs nor result 
in highly elevated nitrate levels.
---------------------------------------------------------------------------

    \23\ USEPA. 2007. Nitrates and Nitrites. U.S. Environmental 
Protection Agency. http://www.epa.gov/teach/chem_summ/Nitrates_summary.pdf. Accessed December 2009.
    \24\ FDEP 2009. Chemical Data for 2004, 2005, 2006, 2007 and 
2008. Florida Department of Environmental Protection. http://www.dep.state.fl.us/water/drinkingwater/chemdata.htm. Accessed 
January 2010.
    \25\ Southern Regional Water Program. 2010. Drinking Water and 
Human Health in Florida. Southern Regional Water Program, http://srwqis.tamu.edu/florida/program-information/florida-target-themes/drinking-water-and-human-health.aspx. Accessed January 2010.
    \26\ USEPA. 2009. Drinking Water Contaminants. U.S. 
Environmental Protection Agency. Accessed http://www.epa.gov/safewater/hfacts.html. December 2009.
    \27\ CFR. 2006. 40 CFR parts 9, 141, and 142: National Primary 
Drinking Water Regulations: Stage 2 Disinfectants and Disinfection 
Byproducts Rule. Code of Federal Regulations, Washington, DC. http://www.epa.gov/fedrgstr/EPA-WATER/2006/January/Day-04/w03.htm. 
Accessed December 2009.
    \28\ Carmichael, W.W. 2000. Assessment of Blue-Green Algal 
Toxins in Raw and Finished Drinking Water. AWWA Research Foundation, 
Denver, CO.
    \29\ NOAA. 2009. Marine Biotoxins. National Oceanic and 
Atmospheric Administration. http://www.nwfsc.noaa.gov/hab/habs_toxins/marine_biotoxins/index.html. Accessed December 2009.
---------------------------------------------------------------------------

    Nutrient pollution and eutrophication can also impact the economy 
through additional reactive costs, such as medical treatment for humans 
who ingest HAB toxins, treating drinking water supplies to remove algae 
and organic matter, and monitoring water for shellfish and other 
affected resources.
    Economic losses from algal blooms and HABs can include reduced 
property values for lakefront areas, commercial fishery losses, and 
lost revenue from recreational fishing and boating trips, as well as 
other tourism-related businesses. Commercial fishery losses occur 
because of a decline in the amount of fish available for harvest due to 
habitat and oxygen declines. Some HAB toxins can make seafood unsafe 
for human consumption, and can reduce the amount of fish bought because 
people might question if eating fish is safe after learning of the 
presence of the algal bloom.\30\ To put the issue into perspective, 
consider the following estimates: For freshwater lakes, losses in 
fishing and boating trip-related revenues nationwide due to 
eutrophication are estimated to range from $370 million to almost $1.2 
billion dollars and loss of lake property values from excessive algal 
growth are estimated to range from $300 million to $2.8 billion 
annually on a national level.\31\
---------------------------------------------------------------------------

    \30\ WHOI. 2008. Hearing on 'Harmful Algal Blooms: The 
Challenges on the Nation's Coastlines.' Woods Hole Oceanographic 
Institution. http://www.whoi.edu/page.do?pid=8916&tid=282&cid=46007. Accessed December 2009.
    \31\ Dodds, W.K., W.W. Bouska, J.L. Eitzmann, T.J. Pilger, K.L. 
Pitts, A.J. Riley, J.T. Schloesser, and D.J. Thornbrugh. 2009. 
Eutrophication of U.S. freshwaters: analysis of potential economic 
damages. Environ.l Sci. Tech.y. 43(1):12-19.
---------------------------------------------------------------------------

3. Nutrient Pollution in Florida
    Water quality degradation resulting from excess nitrogen and 
phosphorus loadings is a documented and significant environmental issue 
in Florida. According to Florida's 2008 Integrated Report,\32\ 
approximately 1,000 miles of rivers and streams, 350,000 acres of 
lakes, and 900 square miles of estuaries are impaired for nutrients in 
the State. To put this in context, these values represent approximately 
5% of the assessed river and stream miles, 23% of the assessed lake 
acres, and 24% of the assessed square miles of estuaries that Florida 
has listed as impaired in the 2008 Integrated Report.\33\ Nutrients are 
ranked as the fourth major source of impairment for rivers and streams 
in the State (after dissolved oxygen, mercury in fish, and fecal 
coliforms). For lakes and estuaries, nutrients are ranked first and 
second, respectively. As discussed above, impairments due to nutrient 
pollution result in significant impacts to aquatic life and ecosystem 
health. Nutrient pollution also represents, as mentioned above, an 
increased human health risk in terms of contaminated drinking water 
supplies and private wells.
---------------------------------------------------------------------------

    \32\ Florida Department of Environmental Protection. 2008. 
Integrated Water Quality Assessment for Florida: 2008 305(b) Report 
and 303(d) List Update.
    \33\ Florida Department of Environmental Protection. 2008. 
Integrated Water Quality Assessment for Florida: 2008 305(b) Report 
and 303(d) List Update.
---------------------------------------------------------------------------

    Florida is particularly vulnerable to nutrient pollution. 
Historically, the State has experienced a rapidly expanding population, 
which is a strong predictor of nutrient loading and associated effects, 
and which combined with climate and other natural factors, make Florida 
waters sensitive to nutrient effects. Florida is currently the fourth 
most populous state in the nation, with an estimated 18 million 
people.\34\ Population is expected to continue to grow, resulting in an 
expected increase in urban development, home landscapes, and 
wastewater. Florida's flat topography causes water to move slowly over 
the landscape, allowing ample opportunity for eutrophication responses 
to develop. Similarly, small tides in many of Florida's estuaries 
(especially on the Gulf coast) also allow for well-developed 
eutrophication responses in tidal waters. Florida's warm and wet, yet 
sunny, climate further contributes to increased run-off and subsequent 
eutrophication responses.\35\ Exchanges of surface water and ground 
water contribute to complex relationships between nutrient sources and 
the location and timing of eventual impacts.\36\
---------------------------------------------------------------------------

    \34\ U.S. Census Bureau. 2009. 2008 Population Estimates Ranked 
by State. http://factfinder.census.gov.
    \35\ Perry, W.B. 2008. Everglades restoration and water quality 
challenges in south Florida. Ecotoxicology 17:569-578.
    \36\ USGS. 2009. Florida Waters: A Water Resources Manual. 
http://sofia.usgs.gov/publications/reports/floridawaters/. Accessed 
June 9, 2009.
---------------------------------------------------------------------------

    In addition, extensive agricultural development and associated 
hydrologic modifications (e.g., canals and ditches) amplify the State's 
susceptibility to nutrient pollution. Many of Florida's inland areas 
have extensive tracts of agricultural lands. Much of the intensive 
agriculture and associated fertilizer usage takes place in locations 
dominated by poorly drained sandy soils and with high annual rainfall 
amounts, two conditions favoring nutrient-rich runoff. These factors, 
along with population increase, have contributed to a significant 
upward trend in nutrient inputs to Florida's waters.\37\ High 
historical water quality and the human and aquatic life uses of many 
waterways in Florida often means that very low nutrients, low 
productivity, and high water clarity are needed and expected to 
maintain uses.
---------------------------------------------------------------------------

    \37\ Florida Department of Environmental Protection. 2008. 
Integrated Water Quality Assessment for Florida: 2008 305(b) Report 
and 303(d) List Update.
---------------------------------------------------------------------------

B. Statutory and Regulatory Background

    Section 303(c) (33 U.S.C. 1313(c)) of the CWA directs states to 
adopt WQS for their navigable waters. Section 303(c)(2)(A) and EPA's 
implementing regulations at 40 CFR part 131 require, among other 
provisions, that state WQS include the designated use or uses to be 
made of the waters and criteria that protect those uses. EPA 
regulations at 40 CFR 131.11(a)(1) provide that states shall ``adopt 
those water quality criteria

[[Page 4181]]

that protect the designated use'' and that such criteria ``must be 
based on sound scientific rationale and must contain sufficient 
parameters or constituents to protect the designated use.'' As noted 
above, 40 CFR 130.10(b) provides that ``In designating uses of a water 
body and the appropriate criteria for those uses, the state shall take 
into consideration the water quality standards of downstream waters and 
ensure that its water quality standards provide for the attainment and 
maintenance of the water quality standards of downstream waters.''
    States are also required to review their WQS at least once every 
three years and, if appropriate, revise or adopt new standards (CWA 
section 303(c)(1)). States are required to submit these new or revised 
WQS for EPA review and approval or disapproval (CWA section 
303(c)(2)(A)). Finally, CWA section 303(c)(4)(B) authorizes the 
Administrator to determine, even in the absence of a state submission, 
that a new or revised standard is needed to meet CWA requirements. The 
criteria proposed in this rulemaking apply to lakes and flowing waters 
of the State of Florida. EPA's proposal defines ``lakes and flowing 
waters'' to mean inland surface waters that have been classified by 
Florida as Class I (Potable Water Supplies Use) or Class III 
(Recreation, Propagation and Maintenance of a Healthy, Well-Balanced 
Population of Fish and Wildlife Use) water bodies pursuant to Florida 
Administrative Code (F.A.C.) Rule 62-302.400, excluding wetlands, and 
which are predominantly fresh waters.

C. Water Quality Criteria

    EPA has issued guidance for use by states when developing criteria. 
Under CWA section 304(a), EPA periodically publishes criteria 
recommendations (guidance) for use by states in setting water quality 
criteria for particular parameters to protect recreational and aquatic 
life uses of waters. When EPA has published recommended criteria, 
states have the option of adopting water quality criteria based on 
EPA's CWA section 304(a) criteria guidance, section 304(a) criteria 
guidance modified to reflect site-specific conditions, or other 
scientifically defensible methods. 40 CFR 131.11(b)(1).
    For nutrients, EPA has published under CWA section 304(a) a series 
of peer-reviewed, national technical approaches and methods regarding 
the development of numeric nutrient criteria for lakes and 
reservoirs,\38\ rivers and streams,\39\ and estuaries and coastal 
marine waters.\40\ Basic analytical approaches for nutrient criteria 
derivation include, but are not limited to: (1) Stressor-response 
analysis, (2) the reference condition approach, and (3) mechanistic 
modeling. The stressor-response, or effects-based, approach relates a 
water body's response to nutrients and identifies adverse effect 
levels. This is done by selecting a protective value based on the 
relationships of nitrogen and phosphorus field measures with indicators 
of biological response. This approach is empirical, and directly 
relates to the designated uses. The reference condition approach 
derives candidate criteria from distributions of nutrient 
concentrations and biological responses in a group of waters. 
Measurements are made of causal and response variables and a protective 
value is selected from the distribution. The mechanistic modeling 
approach predicts a cause-effect relationship using site-specific input 
to equations that represent ecological processes. Mechanistic models 
require calibration and validation. Each approach has peer review 
support by the broader scientific community, and would provide adequate 
means for any state to develop scientifically defensible numeric 
nutrient criteria.
---------------------------------------------------------------------------

    \38\ U.S. EPA. 2000a. Nutrient Criteria Technical Guidance 
Manual: Lakes and Reservoirs. Office of Water, Washington, DC. EPA-
822-B-00-001.
    \39\ U.S. EPA. 2000b. Nutrient Criteria Technical Guidance 
Manual: Rivers and Streams. Office of Water, Washington, DC. EPA-
822-B-00-002.
    \40\ U.S. EPA. 2001. Nutrient Criteria Technical Manual: 
Estuarine and Coastal Marine Waters. Office of Water, Washington, 
DC. EPA-822-B-01-003, and wetlands (U.S. EPA, 2007).
---------------------------------------------------------------------------

    In cases where scientifically defensible numeric criteria cannot be 
derived, EPA regulations provide that narrative criteria should be 
adopted. 40 CFR 131.11(b)(2). Narrative criteria are descriptions of 
conditions necessary for the water body to attain its designated use. 
Often expressed as requirements that waters remain ``free from'' 
certain characteristics, narrative criteria can be the basis for 
controlling nuisance conditions such as floating debris or 
objectionable deposits. States often establish narrative criteria, such 
as ``no toxics in toxic amounts,'' in order to limit toxic pollutants 
in waters where the state has yet to adopt an EPA-recommended numeric 
criterion and or where EPA has yet to derive a recommended numeric 
criterion. For nutrients, in the absence of numeric nutrient criteria, 
states have often established narrative criteria such as ``no nuisance 
algae.'' Reliance on a narrative criterion to derive NPDES permit 
limits, assess water bodies for listing purposes, and establish TMDL 
targets can often be a difficult, resource-intensive, and time-
consuming process that entails conducting case-by-case analyses to 
determine the appropriate numeric target value based on a site-specific 
translation of the narrative criterion. Narrative criteria are most 
effective when they are supported by procedures to translate them into 
quantitative expressions of the conditions necessary to protect the 
designated use.

D. Agency Determination Regarding Florida

    On January 14, 2009, EPA determined under CWA section 303(c)(4)(B) 
that new or revised WQS in the form of numeric nutrient water quality 
criteria are necessary to meet the requirements of the CWA in the State 
of Florida. Florida's currently applicable narrative nutrient criterion 
provides, in part, that ``in no case shall nutrient concentrations of a 
body of water be altered so as to cause an imbalance in natural 
populations of aquatic flora or fauna.'' Florida Administrative Code 
(F.A.C.) 62-302-530(47)(b). EPA determined that Florida's narrative 
nutrient criterion alone was insufficient to ensure protection of 
applicable designated uses. The determination recognized that Florida 
has a proactive and innovative program to address nutrient pollution 
through a strategy of comprehensive National Pollutant Discharge 
Elimination System (NPDES) permit regulations, Basin Management Action 
Plans (BMAPs) for implementation of TMDLs which include controls on 
nonpoint sources, municipal wastewater treatment technology-based 
requirements under the 1990 Grizzle-Figg Act, and rules to limit 
nutrient pollution in geographically specific areas like the Indian 
River Lagoon System, the Everglades Protection Area, and Wekiva 
Springs. However, the determination noted that despite Florida's 
intensive efforts to diagnose and control nutrient pollution, 
substantial water quality degradation from nutrient over-enrichment 
remains a significant challenge in the State and one that is likely to 
worsen with continued population growth and land-use changes.
    Florida's implementation of its narrative water quality criterion 
for nutrients is based on site-specific detailed biological assessments 
and analyses, together with site-by-site outreach and stakeholder 
engagement in the context of specific CWA-related

[[Page 4182]]

actions, specifically NPDES permits, TMDLs required for both permitting 
and BMAP activities, and assessment and listing decisions. When 
deriving NPDES water quality-based permit limits, Florida initially 
conducts a site-specific analysis to determine whether a proposed 
discharge has the reasonable potential to cause or contribute to an 
exceedance of its narrative nutrient water quality criterion. The State 
then determines what levels of nutrients would ``cause an imbalance in 
natural populations of aquatic flora or fauna'' and translates those 
levels into numeric ``targets'' for the receiving water and any other 
affected waters. Determining on a water-by-water basis for thousands of 
State waters the levels of nutrients that would ``cause an imbalance in 
natural populations of aquatic flora or fauna'' is a difficult, 
lengthy, and data-intensive undertaking. This work involves performing 
detailed site-specific analyses of the receiving water and any other 
affected waters. If the State has not already completed this analysis 
for a particular water, it can be very difficult to accurately 
determine in the context and timeframe of the NPDES permitting process. 
For example, in some cases, adequate data may take several years to 
collect and therefore, may not be available for a particular water at 
the time of permitting issuance or re-issuance.
    When developing TMDLs, as it does when determining reasonable 
potential and deriving limits in the permitting context, Florida 
translates the narrative nutrient criterion into a numeric target that 
the State determines is necessary to meet its narrative criterion and 
protect applicable designated uses. This process also involves a site-
specific analysis to determine the nutrient levels that would ``cause 
an imbalance in natural populations of aquatic flora or fauna'' in a 
particular water. Each time a site-specific analysis is conducted to 
determine what the narrative criterion means for a particular water 
body in developing a TMDL, the State takes site-specific considerations 
into account and devises a method that works with the available data 
and information.
    In adopting the Impaired Waters Rule (IWR), Florida took important 
steps toward improving implementation of its narrative nutrient 
criterion by establishing and publishing an assessment methodology to 
identify waters impaired for nutrients. This methodology includes 
numeric nutrient impairment ``thresholds'' above which waters are 
automatically deemed impaired. Even when a listing is made, however, 
development of a TMDL is then generally required to support issuance of 
a permit or development of a BMAP.
    Based on the considerations outlined above, EPA concluded that 
numeric criteria for nutrients will enable the State to take necessary 
actions to protect the designated uses, in a timelier manner. The 
resource intensive efforts to interpret the State's narrative criterion 
contribute to delays in implementing the criterion and therefore, 
affect the State's ability to provide the needed protections for 
applicable designated uses. EPA, therefore, determined that numeric 
nutrient criteria are necessary for the State of Florida to meet the 
CWA requirement to have criteria that protect applicable designated 
uses.
    The combined impacts of urban and agricultural activities, along 
with Florida's physical features and important and unique aquatic 
ecosystems, made it clear that the current use of the narrative 
nutrient criterion alone and the resulting delays that it entails do 
not ensure protection of applicable designated uses for the many State 
waters that are either unimpaired and need protection or have been 
listed as impaired and require loadings reductions. EPA determined that 
numeric nutrient water quality criteria would strengthen the foundation 
for identifying impaired waters, establishing TMDLs, and deriving water 
quality-based effluent limits in NPDES permits, thus providing the 
necessary protection for the State's designated uses in its waters. In 
addition, numeric nutrient criteria will support the State's ability to 
effectively partner with point and nonpoint sources to control 
nutrients, thus further providing the necessary protection for the 
designated uses of the State's water bodies. EPA's determination is 
available at the following Web site: http://www.epa.gov/waterscience/standards/rules/fl-determination.htm.
    The January 14, 2009 determination stated EPA's intent to propose 
numeric nutrient criteria for lakes and flowing waters in Florida 
within twelve months of the January 14, 2009 determination, and for 
estuarine and coastal waters within 24 months of the determination. EPA 
has also entered into a Consent Decree with Florida Wildlife 
Federation, Sierra Club, Conservancy of Southwest Florida, 
Environmental Confederation of Southwest Florida, and St. Johns 
Riverkeeper, committing to the schedule stated in EPA's January 14, 
2009 determination to propose numeric nutrient criteria for lakes and 
flowing waters in Florida by January 14, 2010, and for Florida's 
estuarine and coastal waters by January 14, 2011. The Consent Decree 
also requires that final rules be issued by October 15, 2010 for lakes 
and flowing waters, and by October 15, 2011 for estuarine and coastal 
waters.
    In accordance with the determination and EPA's Consent Decree, EPA 
is proposing numeric nutrient criteria for Florida's lakes and flowing 
waters with this proposed rule. As envisioned in EPA's determination, 
this time frame has allowed EPA to utilize the large data set collected 
by Florida as part of a detailed analysis of nutrient-impaired waters. 
In a separate rulemaking, EPA intends to develop and propose numeric 
nutrient criteria for Florida's estuarine and coastal waters by January 
14, 2011. EPA's determination did not apply to Florida's wetlands, and 
as a result, Florida's wetlands will not be addressed in this 
rulemaking or in EPA's forthcoming rulemaking involving estuarine and 
coastal waters.

III. Proposed Numeric Nutrient Criteria for the State of Florida's 
Lakes and Flowing Waters

A. General Information

(1) Which Water Bodies Are Affected by This Proposed Rule?
    The criteria proposed in this rulemaking apply to lakes and flowing 
waters of the State of Florida. EPA's proposal defines ``lakes and 
flowing waters'' to mean inland surface waters that have been 
classified as Class I (Potable Water Supplies) or Class III 
(Recreation, Propagation and Maintenance of a Healthy, Well-Balanced 
Population of Fish and Wildlife) water bodies pursuant to Rule 62-
302.400, F.A.C., excluding wetlands, and which are predominantly fresh 
waters. Pursuant to Rule 62-302.200, F.A.C., EPA's proposal defines 
``predominantly fresh waters'' to mean surface waters in which the 
chloride concentration at the surface is less than 1,500 milligrams per 
liter (mg/L) and ``surface water'' means water upon the surface of the 
Earth, whether contained in bounds created naturally, artificially, or 
diffused. Waters from natural springs shall be classified as surface 
water when it exits from the spring onto the Earth's surface.
    In this rulemaking, EPA is proposing numeric nutrient criteria for 
the following four water body types: Lakes, streams, springs and clear 
streams, and canals in south Florida. EPA's proposal also includes 
definitions for each of these waters. ``Lake'' means a freshwater water 
body that is not a stream or other watercourse with some open 
contiguous water free from emergent vegetation. ``Stream'' means a 
free-flowing, predominantly fresh surface water in a

[[Page 4183]]

defined channel, and includes rivers, creeks, branches, canals (outside 
south Florida), freshwater sloughs, and other similar water bodies. 
``Spring'' means the point where underground water emerges onto the 
Earth's surface, including its spring run. ``Spring run'' means a free-
flowing water that originates from a spring or spring group whose 
primary (>50%) source of water is from a spring or spring group. 
Downstream waters from a spring that receive 50% or more of their flow 
from surface water tributaries are not considered spring runs. ``Clear 
stream'' means a free-flowing water whose color is less than 40 
platinum cobalt units (PCU, which is assessed as true color free from 
turbidity). Classification of a stream as clear or colored is based on 
the instantaneous color of the sample. Consistent with Rule 62-312.020, 
F.A.C., ``canal'' means a trench, the bottom of which is normally 
covered by water with the upper edges of its two sides normally above 
water. Consistent with Rule 62-302.200, F.A.C., all secondary and 
tertiary canals wholly within Florida's agricultural areas are 
classified as Class IV waters, not Class III, and therefore, are not 
subject to this proposed rulemaking. The classes of waters, as 
specified in this paragraph and as subject to this proposed rulemaking, 
are hereinafter referred to as ``lakes and flowing waters'' in this 
proposed rule.
    The CWA requires adoption of WQS for ``navigable waters.'' CWA 
section 303(c)(2)(A). The CWA defines ``navigable waters'' to mean 
``the waters of the United States, including the territorial seas.'' 
CWA section 502(7). Whether a particular water body is a water of the 
United States is a water body-specific determination. Every water body 
that is a water of the United States requires protection under the CWA. 
EPA is not aware of any waters of the United States in Florida that are 
currently exempted from the State's WQS. For any privately owned water 
in Florida that is a water of the United States, the applicable numeric 
nutrient criteria for those types of waters would apply. This rule does 
not apply to waters for which the Miccosukee Tribe of Indians or 
Seminole Tribe of Indians has obtained Treatment as a State for Section 
303 of the CWA, pursuant to Section 518 of the CWA.
(2) Background on EPA's Derivation of Proposed Numeric Nutrient 
Criteria for the State of Florida's Lakes and Flowing Waters
    In proposing numeric nutrient criteria for Florida's lakes and 
flowing waters, EPA developed numeric nutrient criteria to support a 
balanced natural population of flora and fauna in Florida lakes and 
flowing waters, and to ensure, to the extent that the best available 
science allows, the attainment and maintenance of the WQS of downstream 
waters. Where numeric nutrient criteria do not yet exist, in proposed 
or final form, for a water body type that is downstream from a lake or 
flowing water (e.g., estuaries) in Florida, EPA has interpreted the 
currently applicable State narrative criterion, ``in no case shall 
nutrient concentrations of a body of water be altered so as to cause an 
imbalance in natural populations of aquatic flora or fauna,'' to ensure 
that the numeric criteria EPA is proposing would not result in nutrient 
concentrations that would ``cause an imbalance in natural populations 
of aquatic flora or fauna'' in such downstream water bodies. EPA's 
actions are consistent with and support existing Florida WQS 
regulations. EPA used the best available science to estimate protective 
loads to downstream estuaries, and then used these estimates (and 
assumptions about the distribution of the load throughout the 
watershed), along with mathematical models, to calculate concentrations 
in upstream flowing waters that would have to be met to ensure the 
attainment and maintenance of the State's narrative criterion 
applicable to downstream estuaries.
    EPA relied on an extensive amount of Florida-specific data, 
collected and analyzed, in large part, by FDEP and then reviewed by 
EPA. EPA worked extensively with FDEP on data interpretation and 
technical analyses for developing scientifically sound numeric nutrient 
criteria for this proposed rulemaking. Because EPA is committed to 
ensuring the use of the best available science, the Agency submitted 
its criteria derivation methodologies, developed by EPA in close 
collaboration with FDEP experts and scientists, to an independent, 
external, scientific peer review in July 2009.
    To support derivation of EPA's proposed lakes criteria, EPA 
searched extensively for relevant and useable lake data. In this case 
the effort resulted in 33,622 samples from 4,417 sites distributed 
among 1,599 lakes statewide.
    Regarding the derivation of EPA's proposed streams criteria, EPA 
evaluated water chemistry data from 11,761 samples from 6,342 sites 
statewide in the ``all streams'' dataset. EPA also used data collected 
for linking nutrients to specific biological responses that consisted 
of 2,023 sample records from more than 1,100 streams.
    For EPA's proposed springs and clear streams criteria, EPA 
evaluated data gathered and synthesized by FDEP using approximately 50 
studies including historical accounts, laboratory nutrient amendment 
bioassays, field surveys, and TMDL reports that document increasing 
patterns of nitrate-nitrite levels and corresponding ecosystem level 
responses observed within the last 50 years. At least a dozen of these 
studies were used to develop and support the proposed nitrate-nitrite 
criterion for spring ecosystems.
    For EPA's proposed criteria for canals for south Florida, EPA 
started with more than 1,900,000 observations from more than 3,400 
canal sites. These were filtered for data relevant to nutrient criteria 
development and resulted in observations at more than 500 sites for 
variables (nutrient parameter data and chlorophyll a data). Reliance on 
these extensive sets of data has enabled EPA to use the best available 
information and science to derive robust, scientifically sound criteria 
applicable to Florida's lakes and flowing waters.
    Section III describes EPA's proposed numeric nutrient criteria for 
Florida's lakes, streams, springs and clear streams, and canals and the 
associated methodologies EPA employed to derive them. These criteria 
are based on sound scientific rationale and will protect applicable 
designated uses in Florida's lakes and flowing waters. EPA solicits 
public comment on these criteria and their derivation. This preamble 
also includes discussions of alternative approaches that EPA considered 
but did not select as the preferred option to derive the proposed 
criteria. EPA invites public comment on the alternative approaches as 
well. In addition, EPA requests public comment on whether the proposed 
numeric nutrient criteria are consistent with Florida's narrative 
criterion with respect to nutrients at Rule 62-302.530(47)(a), F.A.C., 
specifying that the discharge of nutrients shall be limited as needed 
to prevent violations of other standards. EPA seeks scientific data and 
information on whether, for example, nutrient criteria should be more 
stringent to prevent exceedances of dissolved oxygen criteria.
    EPA has created a technical support document that provides detailed 
information regarding all methodologies discussed herein and the 
derivation of the proposed criteria. This document is entitled 
``Technical Support Document for EPA's Proposed Rule For Numeric 
Nutrient Criteria for Florida's Inland Surface Fresh Waters'' 
(hereafter, EPA TSD for Florida's Inland Waters) and is

[[Page 4184]]

located at www.regulations.gov, Docket ID No. EPA-HQ-OW-2009-0596.

B. Proposed Numeric Nutrient Criteria for the State of Florida's Lakes

    Florida's 2008 Integrated Water Quality Assessment Report \41\ 
indicates that Florida lakes provide important habitats for plant and 
animal species and are a valuable resource for human activities and 
enjoyment. The State has more than 7,700 lakes, which occupy close to 
6% of its surface area. The largest lake, Lake Okeechobee (covering 
435,840 acres), is the ninth largest lake in surface area in the United 
States and the second largest freshwater lake wholly within the 
coterminous United States.\42\ Most of the State's lakes are shallow, 
averaging seven to 20 feet deep, although many sinkhole lakes and parts 
of other lakes are much deeper.
---------------------------------------------------------------------------

    \41\ FDEP. 2008. Integrated Water Quality Assessment for 
Florida: 2008 305(b) Report and 303(d) List Update. Florida 
Department of Environmental Protection.
    \42\ Fernald, E.A. and E.D. Purdum. 1998. Water Resources Atlas 
of Florida. Tallahassee: Institute of Science and Public Affairs, 
Florida State University.
---------------------------------------------------------------------------

    Florida's lakes are physically, chemically, and biologically 
diverse. Many lakes are spring-fed, others are seepage lakes fed by 
ground water, and still others (about 20%) are depression lakes fed by 
surface water sources. For purposes of developing numeric nutrient 
criteria, EPA identified two classifications of lakes, colored lakes 
and clear lakes, which respond differently to inputs of TN and TP, as 
discussed in detail below. EPA further classified the clear lakes into 
clear alkaline lakes (relatively high alkalinity) and clear acidic 
lakes (relatively low alkalinity), which have different baseline 
expectations for the level of nutrients present.
(1) Proposed Numeric Nutrient Criteria for Lakes
    EPA is proposing the following numeric nutrient criteria and 
geochemical classifications for Florida's lakes classified as Class I 
or III waters under Florida law (Rule 62-302.400, F.A.C.):

----------------------------------------------------------------------------------------------------------------
                                                       Baseline criteria \b\        Modified criteria  (within
Long-term average lake color and   Chlorophyll a --------------------------------        these bounds) \c\
           alkalinity              \f\ ([mu]g/L)                                 -------------------------------
                                        \a\        TP (mg/L) \a\   TN (mg/L) \a\   TP (mg/L) \a\   TN (mg/L) \a\
----------------------------------------------------------------------------------------------------------------
A                                              B               C               D               E               F
----------------------------------------------------------------------------------------------------------------
Colored Lakes > 40 PCU..........              20           0.050            1.23     0.050-0.157       1.23-2.25
Clear Lakes, Alkaline <= 40 PCU               20           0.030            1.00     0.030-0.087       1.00-1.81
 \d\ and > 50 mg/L CaCO3 \e\....
Clear Lakes, Acidic <= 40 PCU                  6           0.010           0.500     0.010-0.030     0.500-0.900
 \d\ and <= 50 mg/L CaCO3 \e\...
----------------------------------------------------------------------------------------------------------------
\a\ Concentration values are based on annual geometric mean not to be surpassed more than once in a three-year
  period. In addition, the long-term average of annual geometric mean values shall not surpass the listed
  concentration values. (Duration = annual; Frequency = not to be surpassed more than once in a three-year
  period or as a long-term average).
\b\ Baseline criteria apply unless data are readily available to calculate and apply lake-specific, modified
  criteria as described below in footnote c and the Florida Department of Environmental Protection issues a
  determination that a lake-specific modified criterion is the applicable criterion for an individual lake. Any
  such determination must be made consistent with the provisions in footnote c below. Such determination must
  also be documented in an easily accessible and publicly available location, such as an official State Web
  site.
\c\ If chlorophyll a is below the criterion in column B and there are representative data to calculate ambient-
  based, lake-specific, modified TP and TN criteria, then FDEP may calculate such criteria within these bounds
  from ambient measurements to determine lake-specific, modified criteria pursuant to CWA section 303(c).
  Modified TN and TP criteria must be based on at least three years of ambient monitoring data with (a) at least
  four measurements per year and (b) at least one measurement between May and September and one measurement
  between October and April each year. These same data requirements apply to chlorophyll a when determining
  whether the chlorophyll a criterion is met for purposes of developing modified TN and TP criteria. If the
  calculated TN and/or TP value is below the lower value, then the lower value is the lake-specific, modified
  criterion. If the calculated TN and TP value is above the upper value, then the upper value is the lake-
  specific, modified criterion. Modified TP and TN criteria may not exceed criteria applicable to streams to
  which a lake discharges. If chlorophyll a is below the criterion in column B and representative data to
  calculate modified TN and TP criteria are not available, then the baseline TN and TP criteria apply. Once
  established, modified criteria are in place as the applicable WQS for all CWA purposes.
\d\ Platinum Cobalt Units (PCU) assessed as true color free from turbidity. Long-term average color based on a
  rolling average of up to seven years using all available lake color data.
\e\ If alkalinity data are unavailable, a specific conductance of 250 micromhos/cm may be substituted.
\f\ 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.

    The following section describes the methodologies EPA used to 
develop its proposed numeric nutrient criteria for lakes. EPA is 
soliciting comments and scientific data regarding the proposed criteria 
for lakes and their derivation. Section III.B(4) describes one 
alternative approach and two supplementary modifications considered by 
the Agency in developing this lakes proposal. EPA solicits comments and 
data on that approach and those modifications.
(2) Methodologies for Deriving EPA's Proposed Criteria for Lakes
    The process used to develop proposed numeric nutrient criteria for 
a range of diverse waters begins with grouping those waters into 
categories that generally have a common response to elevated levels of 
the stressor pollutants, in this case TN and TP. The following sections 
provide a discussion of (1) the lake classification approach for this 
proposal, (2) identification of an appropriate response variable and 
the levels of that variable that indicate or represent healthy aquatic 
conditions associated with each water body classification, and (3) the 
concentrations of TN and TP that correspond to protective levels of the 
response variable, in this case, chlorophyll a.
    EPA has recommended that nutrient criteria include both causal 
(e.g., TN and TP) and response variables (e.g., chlorophyll a and some 
measure of clarity) when establishing numeric nutrient criteria for 
water bodies.\43\ EPA

[[Page 4185]]

recommends causal variables, in part, to have the means to develop 
source control targets and, in part, to have the means to assess water 
body conditions with knowledge that responses can be variable, 
suppressed, delayed, or expressed at different locations. EPA 
recommends response variables, in part, to have a means to assess water 
body conditions that synthesize the effect of causal variables over 
time, recognizing the daily, seasonal, and annual variability in 
measured nutrient levels.\44\ The ability to establish protective 
criteria for both causal and response variables depends on available 
data and scientific approaches to evaluate these data. For its lake 
criteria, EPA is proposing causal variables for TN and TP and a 
response variable for chlorophyll a. For water clarity, Florida has 
criteria for transparency and turbidity, applicable to all Class I and 
III waters, expressed in terms of a measurable deviation from natural 
background (Rules 32-302.530(67) and (69), F.A.C.). For further 
information on this topic, refer to EPA's TSD for Florida's Inland 
Waters.
---------------------------------------------------------------------------

    \43\ U.S. EPA. 1998. National Strategy for the Development of 
Regional Nutrient Criteria. Office of Water, Washington, DC. EPA 
822-R-98-002; Grubbs, G. 2001. U.S. EPA. (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. November 14, 2001); Grumbles, B.H. 2007. U.S. EPA. 
(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. May 25, 2007).
    \44\ U.S. EPA. 2000. Nutrient Criteria Technical Guidance 
Manual: Rivers and Streams. Office of Water, Washington, DC. EPA-
822-B-00-002.
---------------------------------------------------------------------------

    Interested readers should consult EPA TSD for Florida's Inland 
Waters, Chapter 1: Methodology for Deriving U.S. EPA's Proposed 
Criteria for Lakes, for more detailed information, data, and graphs 
supporting the development of the proposed lake criteria.
(a) Methodology for Proposed Lake Classification
    Based on analyses of geochemical influences in Florida's lakes, EPA 
proposes the following classification scheme for Florida lakes: (1) 
Colored Lakes > 40 Platinum Cobalt Units (PCU), (2) Clear Lakes <= 40 
PCU with alkalinity > 50 mg/L calcium carbonate (CaCO<INF>3</INF>), and 
(3) Clear Lakes <= 40 PCU with alkalinity <= 50 mg/L CaCO<INF>3</INF>.
    Following original work conducted by FDEP, EPA considered several 
key characteristics to categorize Florida's lakes and tailor numeric 
nutrient criteria, recognizing that different types of lakes in Florida 
may respond differently to nutrients. 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 nutrients may occur without exceeding 
desired algal levels. EPA evaluated the relationships between nutrients 
and algal responses for these waters (as measured by chlorophyll a 
concentration), which indicated that water color influences algal 
responses to nutrients. Based on this analysis, EPA found color to be a 
significant factor for categorizing lakes. More specifically, EPA found 
the correlations between nutrients and chlorophyll a concentrations to 
be stronger and less variable when lakes were categorized into two 
distinct groups based on a threshold of 40 PCU. This threshold is 
consistent with the distinction between clear and colored lakes long 
observed in Florida.\45\ Different relationships between nutrients and 
chlorophyll a emerged when lakes were characterized by color, with 
clear lakes demonstrating greater sensitivity to nutrients as would be 
predicted by the increased light penetration, which promotes algal 
growth.
---------------------------------------------------------------------------

    \45\ Shannon, E.E. and P.L. Brezonik. 1972. Limnological 
characteristics of north and central Florida lakes. Limnol. 
Oceanogr. 17(1): 97-110.
---------------------------------------------------------------------------

    Within the clear lakes category, where color is not generally the 
controlling factor in algal growth, EPA evaluated alkalinity as an 
additional distinguishing characteristic. Calcium carbonate 
(CaCO<INF>3</INF>), dissolved from limestone formations and calcareous 
soils, affects the alkalinity and pH of groundwater that feeds into 
lakes. Alkalinity and pH increase when water is in contact with 
limestone or limestone-derived soil. Limestone is also a source of TP, 
and lakes that are higher in alkalinity in Florida are often associated 
with naturally elevated TP levels. These types of lakes are often in 
areas of the State where the underlying geology includes limestone. The 
alkalinity (measured as CaCO<INF>3</INF>) of Florida clear lakes ranges 
from zero to well over 200 mg/L. FDEP's Nutrient Criteria Technical 
Advisory Committee (TAC) evaluated available data from Florida lakes 
and concluded that 50 mg/L alkalinity as CaCO<INF>3</INF> is an 
appropriate threshold above which associated nutrient levels would be 
expected to be significantly elevated among clear lakes. EPA concluded 
that FDEP's proposed approach of using 50 mg/L alkalinity as 
CaCO<INF>3</INF> is an appropriate distinguishing characteristic in 
clear lakes in Florida because lakes with alkalinity <=50 
CaCO<INF>3</INF> represent a comprehensive group of lakes that may be 
naturally oligotrophic. Thus, EPA proposes to classify Florida clear 
lakes as either acidic (<=50 mg/L alkalinity as CaCO<INF>3</INF>) or 
alkaline (>50 mg/L alkalinity as CaCO<INF>3</INF>).
    EPA recognizes that in certain cases FDEP may not have historic 
alkalinity data on record to classify a particular clear lake as either 
alkaline or acidic. When alkalinity data are unavailable, EPA proposes 
a specific conductivity threshold of 250 microSiemens per centimeter 
([mu]S/cm) as a substitute for the threshold of 50 mg/L alkalinity as 
CaCO<INF>3</INF>. Specific conductivity is a measure of the ionic 
activity in water and a data analysis performed by FDEP and re-examined 
by EPA found that a specific conductivity threshold value of 250 [mu]S/
cm is sufficiently correlated with alkalinity to serve as a surrogate 
measure. Of these two measures, alkalinity is the preferred parameter 
to measure because it is less variable and therefore, a more reliable 
indicator, and also because it is a more direct measure of the presence 
of underlying geology associated with elevated nutrient levels.
    EPA solicits comment on the proposed categorization scheme and 
associated thresholds used to classify Florida's lakes. Please see 
Section III.B(4)(b) below in which EPA invites comment on alternative 
lake categorization approaches that EPA considered, in particular, 
those approaches with respect to alkalinity classification and lakes 
occurring in sandhills of northwestern and central Florida.
(b) Methodology for Proposed Chlorophyll a Criteria
    Because excess algal growth is associated with degradation in 
aquatic life and because chlorophyll a levels are a measure of algal 
growth, EPA is using chlorophyll a levels as indicators of healthy 
biological conditions, supportive of aquatic life in each of the 
categories of Florida's lakes described above. EPA found multiple lines 
of evidence supporting chlorophyll a criteria as an effective indicator 
of ambient conditions that would be protective of Florida's aquatic 
life use in lakes. These lines of evidence included trophic state of 
lakes, historical reference conditions in Florida lakes, and model 
results.
    As a primary line of evidence, EPA reviewed and evaluated the 
Trophic State Index (TSI) information in deriving chlorophyll a 
criteria that are protective of designated aquatic life uses in 
Florida's lakes. The TSI quantifies the degree of eutrophication 
(oligotrophic, mesotrophic, eutrophic) \46\ in a water body based on 
observed measurements of nutrients and chlorophyll a. These types of 
boundaries are commonly used in scientific literature and represent an

[[Page 4186]]

established, scientific classification system to describe current 
status and natural expectations for lake conditions with respect to 
nutrients and algal productivity.\47\ EPA's review of TSI studies 
\48\<SUP> </SUP>\49\ indicated that in warm-water lakes such as those 
in Florida, TSI values of 50, 60, and 70 are associated with 
chlorophyll a concentrations of 10, 20, and 40 micrograms per liter 
([mu]g/L), respectively. Studies indicated that mesotrophic lakes in 
Florida have TSI values ranging from 50 to 60 and eutrophic lakes have 
TSI values ranging from 60 to 70. Thus a TSI value of 60 (chlorophyll a 
concentration of 20 [mu]g/L) represents the boundary between mesotrophy 
and eutrophy. EPA concluded that mesotrophic status is the appropriate 
expectation for colored and clear alkaline lakes because they receive 
significant natural nutrient input and support a healthy diversity of 
aquatic life in warm, productive climates such as Florida, and 
mesotrophy represents a lake maintaining a healthy balance between 
benthic macrophytes (i.e., plants growing on the lake bottom) and algae 
in such climates under such conditions. However, clear acidic lakes in 
Florida do not receive comparable natural nutrient input to be 
classified as mesotrophic, and for those lakes, EPA has developed 
criteria that correspond to an oligotrophic status. Oligotrophic lakes 
support less algal growth and have lower chlorophyll a levels. Studies 
indicate that a TSI value of 45 reflects an approximate boundary 
between oligotrophy and mesotrophy (corresponding to chlorophyll a at 
about 7 [mu]g/L). EPA requests comment on these conclusions regarding 
oligotrophic and mesotrophic status expectations for these categories 
of Florida lakes.
---------------------------------------------------------------------------

    \46\ Trophic state describes the nutrient and algal state of an 
aquatic system: Oligotrophic (low nutrients and algal productivity), 
mesotrophic (moderate nutrients and algal productivity), and 
eutrophic (high nutrients and algal productivity).
    \47\ Carlson, R.E. 1977. A trophic state index for lakes. 
Limnol. Oceanogr. 22:361-369.
    \48\ Carlson, R.E. 1977. A trophic state index for lakes. 
Limnol. Oceanogr. 22:361-369.
    \49\ Salas and Martino. 1991. A simplified phosphorus trophic 
state index for warm water tropical lakes. Wat. Res. 25:341-350.
---------------------------------------------------------------------------

    Another line of evidence that supports EPA's proposed chlorophyll a 
criteria is historical reference conditions. Diatoms are a very common 
type of free-floating algae (i.e., phytoplankton) that have shells or 
``frustules'' made of silica that are preserved in the fossil record. 
Diatoms preserved in lake sediments can be used to infer chlorophyll a 
levels in lakes prior to any human disturbance. Paleolimnological 
studies \50\ that examined preserved diatom frustules in Florida lake 
sediments indicate that historical levels of chlorophyll a are 
consistent with mesotrophic expectations derived from the TSI studies 
described above, with chlorophyll a levels falling just below the 
selected criterion for mesotrophic lakes. (These studies did not 
evaluate lakes expected to be naturally oligotrophic so there is no 
comparable information for those lakes).
---------------------------------------------------------------------------

    \50\ Whitmore and Brenner. 2002. Paleologic characterization of 
pre-disturbance water quality conditions in EPA defined Florida lake 
regions. Univ. Florida Dept. Fisheries and Aquatic Sciences. 30 pp.
---------------------------------------------------------------------------

    In addition to this evidence, EPA used information from the 
application of a Morphoedaphic Index (MEI) model \51\ that predicts 
nutrient and chlorophyll a concentrations for any lake given its depth, 
alkalinity, and color to support the proposed chlorophyll a criteria. 
Scientists from the St. John's Water Management District presented 
modeling results for various Florida lakes in each colored and clear 
category at the August 5, 2009 meeting of the Nutrient Criteria TAC in 
Tallahassee. In addition to predicting natural or reference conditions, 
these scientists used the model to predict chlorophyll a and TP 
concentrations associated with a 10% reduction in water transparency 
for a set of lakes with varying color levels and alkalinities. Because 
submerged aquatic vegetation is dependent on light, maintaining a 
lake's historic balance between algae and submerged aquatic plants 
requires maintaining overall water transparency. The risk of disrupting 
the balance between algae and submerged aquatic plants increases when 
reductions in transparency exceed 10%. The MEI predictions corroborated 
the results from lake TSI studies and investigations of 
paleolimnological reference conditions because natural or reference 
predictions (i.e., a ``no effect'' level) were generally below selected 
criteria levels and 10% transparency loss predictions (i.e., a 
``threshold effect'' level) were at or slightly above selected criteria 
levels. EPA considered these lines of evidence to develop the proposed 
chlorophyll a criteria, discussed below by lake class:
---------------------------------------------------------------------------

    \51\ Vighi and Chiaudani. 1985. A simple method to estimate lake 
phosphorus concentrations resulting from natural background 
loadings. Wat. Res.19:987-991.
---------------------------------------------------------------------------

    (i) Colored Lakes: EPA proposes a chlorophyll a criterion of 20 
[mu]g/L in colored lakes to protect Florida's designated aquatic life 
uses. As indicated by the warm-water TSI studies discussed above, 
chlorophyll a concentrations of 20 [mu]g/L represent the boundary 
between mesotrophy and eutrophy. Because mesotrophy maintains a healthy 
balance of plant and algae populations in these types of lakes, 
limiting chlorophyll a concentrations to 20 [mu]g/L would, therefore, 
protect colored lakes in Florida from the adverse impacts of 
eutrophication. Paleolimnological studies of six colored lakes in 
Florida demonstrated natural (i.e., before human disturbance) 
chlorophyll a levels in the range of 14-20 [mu]g/L and the MEI model 
predicted reference chlorophyll a concentrations of 1-25 [mu]g/L for a 
set of colored lakes in Florida. The model also predicted that 
concentrations of chlorophyll a ranging from 15-36 [mu]g/L in 
individual lakes would result in a 10% loss of transparency (all but 
two lakes were above 20 [mu]g/L). Because of natural variability, it is 
typical for ranges of natural or reference conditions to overlap with 
ranges of where adverse effects may begin occurring (such as the 10% 
transparency loss endpoint) for any sample population of lakes. In 
addition, these modeling results, as with any line of evidence, have 
uncertainty associated with any individual lake prediction. Given these 
considerations, EPA found that because the clear majority (eight of 
eleven) of lakes had predicted natural or referenced conditions below 
20 [mu]g/L chlorophyll a and the clear majority (nine of eleven) of 
lakes had predicted 10% transparency loss above 20 [mu]g/L chlorophyll 
a, these results supported the TSI-based proposed chlorophyll a 
criterion.
    (ii) Clear, Alkaline Lakes: EPA proposes a chlorophyll a 
concentration of 20 [mu]g/L in clear, alkaline lakes to protect 
Florida's designated aquatic life uses. As noted in Section 
III.B(2)(a), alkalinity and TP are often co-occurring inputs to Florida 
lakes because of the presence of TP in limestone, which is often a 
feature of the geology in Florida. Clear, alkaline lakes, therefore, 
are likely to be naturally mesotrophic. EPA's analysis determined that 
aquatic life in clear, alkaline lakes is protected at similar 
chlorophyll a levels as colored lakes (at the TSI boundary between 
mesotrophy and eutrophy). The MEI model predicted reference chlorophyll 
a concentrations of 12-24 [mu]g/L for a set of clear, alkaline lakes in 
Florida, and predicted a 10% loss of transparency when chlorophyll a 
concentrations ranged from 19-33 [mu]g/L. Similar to the results for 
colored lakes, half of the clear, alkaline lakes had predicted natural 
or referenced conditions at or below 20 [mu]g/L chlorophyll a and all 
but one clear,

[[Page 4187]]

alkaline lake had predicted 10% transparency loss above 20 [mu]g/L 
chlorophyll a. Thus, EPA found this evidence to be supportive of the 
proposed chlorophyll a criterion. EPA solicits comment on this 
chlorophyll a criterion and the evidence EPA used to support the 
criterion.
    (iii) Clear, Acidic Lakes: EPA proposes a chlorophyll a 
concentration of 6 [mu]g/L in clear, acidic lakes to ensure balanced 
natural populations of flora and fauna (i.e., aquatic life) in these 
lakes. In contrast to colored lakes and clear, alkaline lakes, this 
category of lakes does not receive significant natural nutrient inputs 
from groundwater or other surface water sources. EPA has thus based the 
proposed criteria on an expectation that these lakes should be 
oligotrophic in order to support balanced natural populations of flora 
and fauna. Some of Florida's clear, acidic lakes, in the sandhills in 
northwestern and central Florida, have been identified as extremely 
oligotrophic \52\ with chlorophyll a levels of less than 2 [mu]g/L. As 
discussed above, warm water TSI studies suggest a chlorophyll a level 
of approximately 7 [mu]g/L at the oligotrophic-mesotrophic boundary.
---------------------------------------------------------------------------

    \52\ Canfield, D.E., Jr., M.J. Maceina, L.M. Hodgson, and K.A. 
Langeland. 1983. Limnological features of some northwestern Florida 
lakes. J. Freshw. Ecol. 2:67-79; Griffith, G.E., D.E. Canfield, Jr., 
C.A. Horsburgh, J.M. Omernik, and S.H. Azevedo. 1997. Lake regions 
of Florida. Map prepared by U.S. EPA, Corvallis, OR; available at 
http://www.epa.gov/wed/pages/ecoregions/fl_eco.htm (accessed 10/09/
2009).
---------------------------------------------------------------------------

    In July 2009, FDEP proposed a chlorophyll a criterion for clear, 
acidic lakes of 9 [mu]g/L.\53\ In comments sent to EPA via e-mail in 
October 2009,\54\ FDEP reported that the Nutrient TAC suggested in June 
2009 that maintaining chlorophyll a below 10 [mu]g/L in clear, acidic 
lakes would be protective of the designated use, because a value of < 
10 [mu]g/L would still be categorized as oligotrophic. However, EPA's 
review of the TSI categorization based on the work of Salas and Martino 
(1991) on warm water lakes indicates that a chlorophyll a of 10 [mu]g/L 
(TSI of 50) would better represent the central tendency of the 
mesotrophic category rather than the oligotrophic-mesotrophic boundary. 
In the October 2009 comments, FDEP also presented an analysis of lake 
data that showed lack of correlation between an index of benthic 
macroinvertebrate health and chlorophyll a levels in the range of 5-10 
[mu]g/L as supporting evidence for a chlorophyll a criterion of 9 
[mu]g/L in clear acidic lakes. However, within this small range of 
chlorophyll a, it is not surprising that a correlation with an 
indicator responsive to numerous aspects of natural conditions and 
stressors such as benthic macroinvertebrate health would not exhibit a 
clear statistical relationship. Importantly, there was some evidence of 
meaningful distinctions within the range of 5-10 [mu]g/L chlorophyll a 
based on endpoints more directly responsive to nutrients. In this case, 
the MEI model predicted reference chlorophyll a concentrations within 
the range of 1.4-7.0 [mu]g/L (with seven of the eight values below 5 
[mu]g/L) for a set of clear, acidic lakes in Florida, and predicted a 
10% loss of transparency when chlorophyll a concentrations ranged from 
5.6-11.8 [mu]g/L (with five of the eight values below 7 [mu]g/L). All 
but one of the clear, acid lakes had predicted natural or reference 
conditions below 6 [mu]g/L chlorophyll a and the majority (six of 
eight) of clear, alkaline lakes had predicted 10% transparency loss 
above 6 [mu]g/L chlorophyll a. Given available information on reference 
condition and predicted effect levels, EPA adjusted the approximate 
oligotrophic-mesotrophic boundary value of 7 [mu]g/L slightly downward 
to 6 [mu]g/L as the proposed chlorophyll a criterion. For determining 
the proposed chlorophyll a criterion in the three lake categories, only 
in this case for clear, acid lakes did EPA use reference condition 
information and predicted effect levels for more than just support of 
the value coming from the TSI-based line of evidence, and in this case 
EPA deviated from that value by only 1 [mu]g/L.
---------------------------------------------------------------------------

    \53\ More information on this issue is available on FDEP's Web 
site at http://www.dep.state.fl.us/water/wqssp/nutrients/docs/dep_responses_100909.pdf and included in the ``External Peer Review of 
EPA's `Proposed Methods and Approaches for Developing Numeric 
Nutrient Criteria for Florida's Inland Waters' '' and EPA's TSD for 
Florida's Inland Waters located in the docket ID No. EPA-HQ-OW-2009-
0596.
    \54\ FDEP document titled, ``DEP's Responses to EPA's 9/16 
Comment Letter.'' October 9, 2009. Located in the docket ID EPA-HQ-
OW-2009-0596.
---------------------------------------------------------------------------

    EPA specifically solicits comment on the chlorophyll a criterion of 
6 ug/L and the evidence EPA used to support the criterion. EPA also 
solicits comment on whether a higher criterion of 9 ug/L, as proposed 
by Florida in its July 2009 proposed nutrient WQS, would be fully 
protective of clear acidic lakes, and the scientific basis for such a 
conclusion.
(c) Methodology for Proposed Total Phosphorus (TP) and Total Nitrogen 
(TN) Criteria in Lakes
    EPA proposes TP and TN criteria for each of the classes of lakes 
described in Section III.B(2)(a). The proposed TP and TN criteria are 
based principally on independent statistical correlations between TN 
and chlorophyll a, and TP and chlorophyll a for clear and colored lakes 
in Florida. Each data point used in the statistical correlations 
represents a geometric mean of samples taken over the course of a year 
in a particular Florida lake. After establishing the protective levels 
of chlorophyll a as 20 [mu]g/L for colored lakes and clear alkaline 
lakes and 6 [mu]g/L for clear acidic lakes, EPA evaluated the data on 
TN and TP concentrations associated with these chlorophyll a levels and 
the statistical analyses performed by FDEP in support of the State's 
efforts to develop numeric nutrient criteria.
    These analyses showed that the response dynamics of TN and TP with 
chlorophyll a were different 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 the 
correlation relationships for TN and TP compared with chlorophyll a in 
acidic and alkaline clear lakes were comparable, as would be expected 
because alkalinity does not affect light penetration. These analyses 
are available in EPA's TSD for Florida's Inland Waters, Chapter 1: 
Methodology for Deriving U.S. EPA's Proposed Criteria for Lakes.
    The difference between clear, acidic and clear, alkaline lakes is 
that clear, alkaline lakes naturally receive more nutrients and, 
therefore, have an expected trophic status of mesotrophic to maintain a 
healthy overall production and balance of plants and algae. On the 
other hand, clear, acidic lakes naturally receive much lower nutrients 
and, therefore, have an expected trophic status of oligotrophic to 
maintain a healthy, but lower than mesotrophic, level of plant and 
algae aquatic life. Because of the different expectations for trophic 
condition, different chlorophyll a criteria are appropriate (as 
mentioned earlier, chlorophyll a is a measure of algal production). 
Although clear, alkaline lakes and colored lakes have the same proposed 
chlorophyll a criterion, they will have different TP and TN criteria 
because of the effect of color on light penetration and algal growth.
    The TN and TP values EPA is proposing are based on the lower and 
upper TN and TP values derived from the 50th percentile prediction 
interval of the regression (i.e., best-fit line) through the 
chlorophyll a and corresponding TN or TP values plotted on a 
logarithmic scale. In other words, the prediction interval displays the 
range of TN and TP values typically associated with a given chlorophyll 
a concentration. At any given chlorophyll a concentration, there will 
be a lower

[[Page 4188]]

TN or TP value and an upper TN or TP value corresponding to this 
prediction interval. EPA agrees with the FDEP approach that uses the 
50th percentile prediction interval because it effectively separates 
the data into three distinct groups. This analysis of the substantial 
lake data collected by Florida indicates that the vast majority of 
monitored lakes with nutrient levels below the lower TN or TP value 
have associated chlorophyll a values below the protective chlorophyll a 
threshold level. Similarly, the vast majority of monitored lakes with 
measured nutrient levels above the upper TN or TP value have associated 
measured chlorophyll a values above the protective chlorophyll a 
threshold level. Between these TN and TP bounds, however, this analysis 
indicates that monitored lakes are equally likely to be above or below 
the protective chlorophyll a threshold level. Setting TN and TP 
criteria based on the bounds of the 50th percentile prediction 
interval, in conjunction with lake-specific knowledge of whether the 
lake chlorophyll a threshold is met, accounts for the naturally 
variable behavior of TN and TP while ensuring protection of aquatic 
life.
    EPA's proposed criteria framework sets a protective chlorophyll a 
threshold and TN and TP criteria at the lower values of the range 
defined by the 50th percentile prediction interval for the three 
different categories of lakes as ``baseline'' criteria. The criteria 
framework also provides flexibility for FDEP to derive lake-specific, 
modified TN and TP criteria within the bounds of the upper and lower 
values based on at least three years of ambient measurements where a 
chlorophyll a threshold is not exceeded. More specifically, if the 
chlorophyll a criterion for an individual lake is met for a period of 
record of at least three years, then the corresponding TN and TP 
criteria may be derived from ambient measurements of TN and TP from 
that lake within the bounds of the lower and upper values of the 
prediction interval discussed above. Both the ambient chlorophyll a 
levels as well as the corresponding ambient TN and TP concentrations in 
the lake must be established with at least three years worth of data. 
EPA's proposed rule provides that these modified criteria need to be 
documented by FDEP. EPA's rule, however, does not require that FDEP go 
through a formal SSAC process subject to EPA review and approval.
    In this proposed rule, EPA specifies that in no case, however, may 
the modified TN and TP criteria be higher than the upper value 
specified in the criteria bounds, nor lower than the lower value 
specified in the criteria bounds. In addition to nutrients, chlorophyll 
a in a lake may be limited by high water color, zooplankton grazing, 
mineral turbidity, or other unknown factors. In the absence of 
detailed, site-specific knowledge, the upper values represent 
increasing risk that chlorophyll a will exceed its criterion value. To 
maintain the risk at a manageable level, the upper values are not to be 
exceeded. EPA requests comments on this approach. EPA also requests 
comment on whether the rule should specify that the modified TN and TP 
criteria be set at levels lower than the lower value of the criteria 
bounds if that is what is reflected in the outcome of the ambient-based 
calculation.
    EPA's proposed approach for TN and TP criteria in lakes reflects 
the natural variability in the relationship between chlorophyll a 
concentrations and corresponding TP and TN concentrations that may 
exist in lakes. This variability remains even after some explanatory 
factors such as color and alkalinity are addressed by placing lakes in 
different categories based on color and alkalinity because other 
natural factors play important roles. Natural variability in the 
physical, chemical, and biological dynamics for any individual lake may 
result from differences in geomorphology, concentrations of other 
constituents in lake waters, hydrological conditions and mixing, and 
other factors.
    This approach allows for consideration of readily available site-
specific data to be taken into account in the expression of TN and TP 
criteria, while still ensuring protection of aquatic life by 
maintaining the associated chlorophyll a level at or below the proposed 
chlorophyll a criterion level. Because the chlorophyll a level in a 
lake is the direct measure of algal production, it can be used to 
evaluate levels that pose a risk to aquatic life. The scientific 
premise for the lake-specific ambient calculation provision for 
modified TN and TP criteria is that if ambient lake data show that a 
lake's chlorophyll a levels are below the established criteria and its 
TN and/or TP levels are within the lower and upper bounds, then those 
ambient levels of TN and TP represent protective conditions. Basing the 
ambient calculation upon at least three years worth of data is a 
condition set to address and account for year-to-year hydrologic 
variability in the derivation of modified criteria. EPA requests 
comment on the requirement of three years worth of data for both 
chlorophyll a and TN and TP in order to use this option. Specifically, 
are there situations in which less than three years of data might be 
adequate for an adjusted TN or TP criterion?
    EPA selected the proposed TP and TN criteria based on the 
relationships with chlorophyll a described above. However, the MEI 
modeling results described in Section III.B(2)(b) also provide 
additional support for the TP criteria selection. The MEI predicted a 
10% transparency loss when TP concentrations ranged from 0.053-0.098 
mg/L in colored lakes (with one predicted value at 0.037 mg/L), from 
0.038-0.068 mg/L in clear, alkaline lakes, and from 0.012-0.024 mg/L in 
clear, acidic lakes. All but one of these predicted values are within 
the lower and upper bounds of the proposed TP criteria. The MEI 
modeling results did not address TN.
(d) Proposed Criteria: Duration and Frequency
    Numeric criteria include magnitude (i.e., how much), duration 
(i.e., how long), and frequency (i.e., how often) components. Beginning 
with EPA's 2004 Integrated Report Guidance,\55\ EPA has used the term 
``exceeding criteria'' to refer to situations where all criteria 
components are not met. The term ``digression'' refers to an ambient 
level that goes beyond a level specified by the criterion-magnitude 
(e.g., in a given grab sample). The term ``excursion'' refers to 
conditions that do not meet the criterion-magnitude and criterion-
duration, in combination. A criterion-frequency specifies the maximum 
rate at which ``excursions'' may occur.
---------------------------------------------------------------------------

    \55\ USEPA. Guidance for 2004 Assessment, Listing and Reporting 
Requirements Pursuant to Sections 303(d) and 305(b) of the Clean 
Water Act. http://www.epa.gov/OWOW/tmdl/tmdl0103/Accessed December 
2009.
---------------------------------------------------------------------------

    For the chlorophyll a, TN, and TP criteria for lakes, the 
criterion-magnitude values (expressed as a concentration) are provided 
in the table and the criterion-duration (or averaging period) is 
specified as annual. The criterion-frequency is no-more-than-once-in-a-
three-year period. In addition, the long-term arithmetic average of 
annual geometric mean values shall not exceed the criterion-magnitude 
values (concentration values).
    Appropriate duration and frequency components of criteria should be 
based on how the data used to derive the criteria were analyzed, and 
what the implications are for protection of designated uses given the 
effects of exposure at the specified criterion concentration for 
different periods of time and recurrence patterns. For lakes, the 
stressor-response relationship was based on annual geometric means for

[[Page 4189]]

individual years at individual lakes. The appropriate duration period 
is therefore annual. The key question is whether this annual geometric 
mean needs to be met every year, or if some allowance for a particular 
year to exceed the applicable criterion could still be considered 
protective.
    Data that contribute to the analysis of TSI, as well as data 
generated from supporting paleolimnological studies and MEI modeling, 
typically represent periods of time greater than a single year. 
Moreover, many of the models and analyses that form the basis of TSI 
results are designed to represent the ``steady-state,'' or long-term 
stable water quality conditions. However, researchers have suggested 
caution in applying steady-state assumptions to lakes with long 
residence times.\56\ In other words, the effects of spikes in annual 
loading could linger and disrupt the steady-state in some lakes. As a 
result, EPA is proposing two expressions of allowable frequency, both 
of which are to be met. First, EPA proposes a no-more-than-one-in-
three-years excursion frequency for the annual geometric mean criteria 
for lakes. Second, EPA proposes that the long-term arithmetic average 
of annual geometric means not exceed the criterion-magnitude 
concentration. EPA anticipates that Florida will use its standard 
assessment periods as specified in Rule 62-303, F.A.C. (Impaired Waters 
Rule) to implement this second provision. These selected frequency and 
duration components recognize that hydrological variability will 
produce variability in nutrient regimes, and individual measurements 
may exceed the criteria magnitude concentrations. Furthermore, they 
balance the representation of underlying data and analyses based on the 
central tendency of many years of data (i.e., the long-term average 
component) with the need to exercise some caution to ensure that lakes 
have sufficient time to process individual years of elevated nutrient 
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 TSD for Florida's Inland 
Waters, Chapter 1: Methodology for Deriving U.S. EPA's Proposed 
Criteria for Lakes.
---------------------------------------------------------------------------

    \56\ Kenney (1998) as reported in Salas and Martino (1991).
---------------------------------------------------------------------------

    EPA requests comment on these proposed criteria duration and 
frequency expressions, and the basis for their derivation. EPA notes 
that some scientists and resource managers have suggested that nutrient 
criteria duration and frequency expressions should be more restrictive 
to avoid seasonal or annual ``spikes'' from which the aquatic system 
cannot easily recover, whereas others have suggested that criteria 
expressed as simply a long-term average of annual geometric means, 
consistent with data used in criteria derivation, would still be 
protective. EPA also requests comment on any alternative duration and 
frequency expressions that might be considered protective, including 
(1) a criterion-duration expressed as a monthly average or geometric 
mean, (2) a criterion-frequency expressed as meeting allowable 
magnitude and duration every year, (3) a criterion-frequency expressed 
as meeting allowable magnitude and duration in more than half the years 
of a given assessment period, and (4) a criterion-frequency expressed 
as meeting allowable magnitude and duration as a long-term average 
only. EPA further requests comment on whether an expression of the 
criteria in terms of an arithmetic average of annual geometric mean 
values based on rolling three-year periods of time would also be 
protective of the designated use.
(e) Application of Lake-Specific, Ambient Condition-Based Modified TP 
and TN Criteria
    As described in Section III.B(2)(c), EPA is proposing a framework 
that uses both the upper and lower bounds of the 50th percentile 
prediction interval to allow the derivation of modified TP and TN lake-
specific criteria to account for the natural variability in the 
relationship between chlorophyll a and TP and TN that may exist in 
certain lakes. The proposed rule would allow FDEP to calculate ambient 
modified criteria for TN and TP based on at least three years of 
ambient monitoring data with (a) at least four measurements per year 
and (b) at least one measurement between May and September and one 
measurement between October and April each year. If a calculated 
modified TN and TP criterion is below the lower value, then the lower 
value is the criteria. If a calculated modified TN and TP criterion is 
above the upper value, then the upper bound is the criteria. Calculated 
modified TP and TN values may not exceed criteria applicable to streams 
to which a lake discharges.
    EPA's proposed rule provides that FDEP must document these modified 
criteria and establish them in a manner that clearly recognizes their 
status as the applicable criterion for a particular lake so that the 
public and all regulatory authorities are aware of its existence. 
However, EPA's proposed rule does not require that FDEP go through a 
formal SSAC process subject to EPA review and approval. (For more 
information on the SSAC process, please refer to Section V of this 
proposal). EPA believes such modified criteria do not need to go 
through the SSAC process because the conditions under which they are 
applicable are clearly stated in the proposed rule and the methods of 
calculation are clearly laid out so that the outcome is predictable and 
transparent. 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 
approval by EPA.
    One technical concern is the extent to which the variability in the 
data relating chlorophyll a levels to TN and TP levels truly reflects 
differences between lakes, as opposed to temporal differences in the 
conditions in the same lake. To address this issue, EPA verified that 
the observed variability in the supporting analysis was indeed 
predominantly ``across lake'' variability, not ``within lake'' 
variability.
    Another technical concern is that there may be a time lag between 
the presence of high nutrients and the biological response. In a study 
of numerous lakes, researchers found that there was often a lag period 
of a few years in chlorophyll a response to changes in nutrient 
loading, but that there was correlation between chlorophyll a and 
nutrient concentrations on an annual basis.\57\ The difference between 
nutrient loading and nutrient concentration as a function of time is 
related to the hydraulic retention time of a lake. EPA proposed TN and 
TP criteria as concentration values with an annual averaging period, so 
any time lag in response would not be expected to confound the 
derivation of modified criteria. Furthermore, EPA is proposing to 
require three years worth of data, which would reflect any short time 
lag in response.
---------------------------------------------------------------------------

    \57\ Jeppeson et al. 2005. Lake responses to reduced nutrient 
loading--an analysis of contemporary long-term data from 35 case 
studies. Freshwater Biology 50: 1747-1771.
---------------------------------------------------------------------------

    A third technical concern is the presence of temporary or long-term 
site-specific factors that may suppress biological response, such as 
the presence of grazing zooplankton, excess sedimentation that blocks 
light penetration, extensive canopy cover, or seasonal herbicide use 
that impedes proliferation of algae. If any of these suppressing 
factors are removed, then nutrient levels may result in a spike in 
algal production above protective levels.

[[Page 4190]]

    EPA is proposing to require that the ambient calculation for 
modified TP and TN criteria be based on at least a three-year record of 
observation, and be based on representative sampling (i.e., four 
samples per year with at least one between May and September and one 
between October and April) during each year. These requirements will 
minimize the influence of long-term site-specific factors and ensure 
longer-term stable conditions. EPA selected three years as a reasonable 
minimum length of time to appropriately account for anomalous 
conditions in any given year that could lead to erroneous conclusions 
regarding the true relationship between nutrient levels in a lake and 
chlorophyll a levels. EPA anticipates that the State would use all 
recent consecutive years of data on record (i.e., it would not be 
appropriate to select three random years within a complete record over 
the past seven years). EPA is requiring four measurements within a year 
to provide seasonal representation (i.e., May-September and October-
April). Providing seasonal representation is important because nutrient 
levels can vary by season. In addition, this minimum sample size is 
conducive to the derivation of central tendency measurements, such as a 
geometric mean, with an acceptable degree of confidence. EPA is 
proposing that the chlorophyll a criterion must be met in each of the 
three or more years of ambient monitoring that define the record of 
observation for the lake to be eligible for the ambient calculation 
modified provision for TN and TP. EPA requests comment on whether three 
years of data is sufficient to establish for a particular lake that 
there is a fundamentally different relationship between chlorophyll a 
levels and TN and TP levels. EPA also requests comment on whether less 
data or a different specification would be sufficient to establish this 
different relationship in a particular lake, e.g. whether revised TN 
and TP ambient criteria should be allowed when the chlorophyll a 
criterion concentration has been exceeded once in three years.
    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 TP values as the 
applicable numeric nutrient criteria for TN and TP. For accountability 
and tracking purposes, the State would need to document in a publicly 
available and accessible manner, such as on an official State Web site, 
the result of the ambient calculation for any given lake. The State may 
wish to issue a public notification, with an opportunity to submit 
additional data and check calculations, to ensure an appropriate value 
is determined. The State may wish to publicly certify the outcome via a 
Secretarial order or some other official statement of intent and 
applicability. EPA's preference is that once modified criteria are 
developed, they remain the applicable criteria for the long-term. The 
State has the flexibility to revise the criteria, but the expectation 
is that they will not be a continuously moving target for 
implementation purposes. As an example of how the lakes criteria might 
work in practice, consider a colored lake which meets the chlorophyll a 
criterion. If FDEP established a modified TP criterion of 0.110 mg/L 
and subsequent monitoring showed levels at 0.136 mg/L, that lake would 
not be considered attaining the applicable criteria for CWA purposes 
(unless the State goes through the process of establishing a revised 
modified criterion).
    The permitting authority would use publicly certified modified TN 
or TP criteria to develop water quality-based effluent limits (WQBELs) 
that derive from and comply with applicable WQS. In this application, 
the permit writer would use the modified ambient criterion, computed as 
described above, as the basis for any reasonable potential analysis or 
permit limit derivation. In this case, as in any other case, EPA 
expects the details to be fully documented in the permit fact sheet.
    This type of ambient calculation provision based on meeting 
response criteria applicable to the assessed water may not be 
appropriate when the established TN and TP criteria are serving to 
maintain and protect waters downstream. To address this concern, EPA 
proposes that calculated TP and TN values in a lake that discharges to 
a stream may not exceed criteria applicable to the stream to which a 
lake discharges. EPA requests comment on this provision.
(3) Request for Comment and Data on Proposed Approach
    EPA is soliciting comment on the approaches described in this 
proposal, the data underlying those approaches, and the proposed 
criteria. EPA will evaluate all data and information submitted by the 
close of the public comment period for this rulemaking with regard to 
nutrient criteria for Florida's lakes. For the application of the 
modified ambient calculation provision, EPA is seeking comment on 
allowing the calculation to occur one time only, based on an adequate 
period of record, and then holding that value as the protective TP or 
TN criteria for future assessment and implementation purposes. EPA is 
also seeking comment on whether to require an ambient chlorophyll a 
level demonstrated to be below the chlorophyll a threshold criterion 
for at least three years become the protective chlorophyll a criterion 
for a lake subject to the modified ambient calculation provision (i.e., 
whether to require a more stringent chlorophyll a criterion if three 
years of data show that the more stringent level reflects current 
conditions in the lake). EPA also requests comment on whether an 
additional condition for being able to apply a modified criterion 
include continued ambient monitoring and verification that chlorophyll 
a levels remain below the protective criterion. EPA could specify that 
modified criteria remain in effect as long as FDEP subsequently 
conducts monthly (or some other periodic) monitoring of the lake to 
ensure that chlorophyll a levels continue to meet the protective 
criterion. If this monitoring is not conducted and documented, EPA 
could specify that the baseline criterion would become the applicable 
criterion. Among others, this provision may address concerns about 
whether the modified criterion adequately represents long-term 
hydrologic variability. Finally, EPA requests comment on the 
appropriate procedure for documenting and tracking the results of 
modified criteria that allows transparency, public access, and 
accountability.
(4) Alternatives Considered by EPA
    During EPA's review of the available data and information for 
development of numeric nutrient criteria for Florida's lakes, EPA 
considered and is soliciting comment on an alternative approach to 
deriving lakes criteria from the statistical correlation plots and 
regression analysis. The alternative approach would use either the 
central tendency values or the lower values associated with the 50th 
percentile prediction interval for TN and TP criteria and would not 
include the framework to calculate modified TP and TN criteria when the 
chlorophyll a criterion is met. EPA is also seeking comments on the 
following two supplementary modifications that EPA considered but did 
not include in this proposal: (1) the use of a modified categorization 
of lakes in Florida; and (2) the addition of upper percentile criteria 
with a different exceedance frequency.

[[Page 4191]]

(a) Single Value Approach To Derive Lakes Criteria--Derive TN and TP 
Criteria Using Correlations Associated With the Regression Line or 
Lower Value of the 50th Percentile Prediction Interval
    One alternative means of selecting TN and TP criteria is to use the 
regression line (central tendency) to calculate TP and TN 
concentrations that correlate to the proposed chlorophyll a criteria 
for each lake class. A second alternative is to use the lower value of 
the 50th percentile prediction interval to calculate TP and TN 
concentrations. Establishing TP and TN criteria using the central 
tendency of the regression line represents the best estimate of TN and 
TP associated with a protective chlorophyll a criterion across all 
lakes, but carries some risk of being overprotective for some 
individual lakes and under-protective for others because of the 
demonstrated variability of the data. On the other hand, establishing 
TP and TN criteria using the lower value of the 50th percentile 
prediction interval will likely be protective in most cases, but could 
be overprotective for a greater number of lakes because the data 
demonstrate that many lakes achieve the protective chlorophyll a 
criterion with higher levels of TN and TP. Neither approach accounts 
for lake-specific natural variability, apart from that accounted for by 
color and alkalinity classification. However, the correlated TP and TN 
concentrations within each lake class at these alternative statistical 
boundaries would result in single criteria values for TN and TP, which 
is an approach that water quality program managers will have more 
familiarity. EPA's rationale for proposing a framework that uses both 
the upper and lower values of the 50th percentile prediction interval 
to allow the derivation of modified TN and TP lake-specific criteria 
rather than either of these single values was to account for the 
natural variability in the relationship between chlorophyll a and TN 
and TP that may exist in lakes. EPA solicits comment, however, on this 
alternative approach of using single values for TN and TP criteria in 
Florida's lakes.
(b) Modification to Proposed Lakes Classification
    As discussed in Section III.B(2)(a), EPA used available data to 
determine a classification scheme for Florida's lakes, based on a color 
threshold of 40 PCU and a threshold of 50 mg/L alkalinity as 
CaCO<INF>3</INF>. In its July 2009 numeric nutrient criteria proposal, 
Florida considered a similar classification approach based on color and 
alkalinity but proposed a chlorophyll a criterion of 9 [micro]g/L to 
protect aquatic life in clear, acidic lakes. As discussed above, EPA 
believes that the scientific evidence more strongly supports a 
chlorophyll a criterion of 6 [micro]g/L to protect Florida's clear, 
acidic lakes that include the very oligotrophic lakes found in 
Florida's sandhills, principally in three areas: the Newhope Ridge/
Greenhead slope north of Panama City (locally called the Sandhill Lakes 
region); the Norfleet/Springhill Ridge just west of Tallahassee, and 
Trail Ridge northeast of Gainesville.\58\ However, some stakeholders 
have suggested that many lakes in the clear, acidic class (as currently 
defined) might be sufficiently protected with a chlorophyll a criterion 
of 9 [micro]g/L. EPA believes the scientific basis for a 9 [micro]g/L 
chlorophyll a value may be more applicable to clear acidic lakes other 
than those in Florida's sandhills (i.e., other than those in the 
Sandhill Lakes region, the Norfleet/Springhill Ridge just west of 
Tallahassee and Trail Ridge northeast of Gainesville). To address this, 
EPA could separate clear, acidic lakes into two categories: one 
category for clear, acidic lakes in sandhill regions of Florida, and a 
second category for clear, acidic lakes in other areas of the State. 
EPA could assign the first category (clear, acidic sandhill lakes) a 
chlorophyll a criterion of 6 [micro]g/L and the second category (clear, 
acidic non-sandhill lakes) a chlorophyll a criterion of 9 [micro]g/L.
---------------------------------------------------------------------------

    \58\ Griffith, G.E., D.E. Canfield, Jr., C.A. Horsburgh, J.M. 
Omernik, and S.H. Azevedo. 1997. Florida lake regions. U.S. EPA, 
Corvallis, OR. http://www.epa.gov/wed/pages/ecoregions/fl_eco.htm.
---------------------------------------------------------------------------

    Alternatively, EPA could lower the defining alkalinity threshold to 
20 mg/L CaCO<INF>3</INF> so that the clear, acidic lakes category would 
only include lakes with very acidic values and correspondingly low 
chlorophyll a, TN, and TP values. EPA's analysis of a distribution of 
alkalinity data from Florida's clear lakes found that lakes with 
alkalinity values >= 20 mg/L CaCO<INF>3</INF> had higher levels of 
nutrients and nutrient response parameters than lakes with alkalinity 
values < 20 mg/L CaCO<INF>3.</INF> By adjusting the alkalinity 
threshold to 20 mg/L CaCO<INF>3</INF>, EPA would be creating a smaller 
group of clear, acidic lakes that may be more representative of 
naturally more acidic, oligotrophic conditions than the proposed 
alkalinity threshold of 50 mg/L CaCO<INF>3</INF>. EPA opted to propose 
a threshold of 50 mg/L CaCO<INF>3</INF> because it represents a more 
comprehensive group of lakes that may be naturally oligotrophic (i.e., 
ensures protection where there may be some uncertainty). EPA solicits 
comment on these alternative approaches to classifying Florida's lakes. 
EPA also notes, as discussed previously, that FDEP recommended a 
criterion of 9 [mu]g/L as being protective of all clear acidic lakes, 
including sandhill lakes and that the Nutrient Criteria TAC supported 
``less than 10 [mu]g/L'' as protective. EPA also requests comment on 9 
[mu]g/L chlorophyll a as being protective of all clear acidic lakes, 
including sandhill lakes.
(c) Modification To Include Upper Percentile Criteria
    EPA is considering promulgating upper percentile criteria for 
chlorophyll a, TN, and TP in colored, clear alkaline, and clear acidic 
lakes to provide additional aquatic life protection. Accordingly, EPA 
could add that the instantaneous concentration in the lake not surpass 
these criterion-magnitude concentrations more than 10% of the time 
(criterion-duration: instant; criterion-frequency: 10% of the time). 
EPA derived example upper percentile criteria using the observed 
standard deviation from the mean of lake samples meeting the respective 
criteria (lower values of the TN and TP ranges) within each lake class. 
Using this example, the calculated criteria-magnitude concentrations 
for chlorophyll a, TN, and TP respectively by lake class are: 63 [mu]g/
L, 1.5 mg/L and 0.09 mg/L for colored lakes; 48 [mu]g/L, 1.8 mg/L and 
0.05 mg/L for clear, alkaline lakes; and 15 [mu]g/L, 0.6 mg/L and 0.02 
mg/L for clear, acidic lakes.
    These criteria would provide the means to protect lakes from 
episodic events that increase loadings for significant periods of time 
during the year, but are balanced out by lower levels in other parts of 
the year such that the annual geometric mean value is met. EPA chose 
not to propose such criteria because of the significant variability of 
chlorophyll a, TN, and TP, the variety of other factors that may 
influence levels of these parameters in the short-term, and that 
significant environmental damage from eutrophication is more likely 
when levels are elevated for longer periods of time. However, EPA 
solicits comment on this additional approach of promulgating upper 
percentile criteria for chlorophyll a, TN, and TP.
(5) Request for Comment and Data on Alternative Approaches
    EPA is soliciting comment on the Agency's proposed approach, as 
well as the alternative approach to deriving numeric nutrient criteria 
for Florida's lakes and the supplemental modifications as described in 
Section III.B(4). EPA will evaluate all data and

[[Page 4192]]

information submitted by the close of the public comment period for 
this rulemaking with regard to nutrient criteria for Florida's lakes.

C. Proposed Numeric Nutrient Criteria for the State of Florida's Rivers 
and Streams

(1) Proposed Numeric Nutrient Criteria for Rivers and Streams
    EPA is proposing numeric nutrient criteria for TN and TP in four 
geographically distinct watershed regions of Florida's rivers and 
streams (hereafter, streams) classified as Class I or III waters under 
Florida law (Rule 62-302.400, F.A.C.).

------------------------------------------------------------------------
                                             Instream protection value
                                                     criteria
        Nutrient watershed region        -------------------------------
                                           TN (mg/L) \a\   TP (mg/L) \a\
------------------------------------------------------------------------
Panhandle \b\...........................           0.824           0.043
Bone Valley \c\.........................           1.798           0.739
Peninsula \d\...........................           1.205           0.107
North Central \e\.......................           1.479           0.359
------------------------------------------------------------------------
\a\ Concentration values are based on annual geometric mean not to be
  surpassed more than once in a three-year period. In addition, the long-
  term average of annual geometric mean values shall not surpass the
  listed concentration values. (Duration = annual; Frequency = not to be
  surpassed more than once in a three-year period or as a long-term
  average).
\b\ Panhandle region includes the following watersheds: Perdido Bay
  Watershed, Pensacola Bay Watershed, Choctawhatchee Bay Watershed, St.
  Andrew Bay Watershed, Apalachicola Bay Watershed, Apalachee Bay
  Watershed, and Econfina/Steinhatchee Coastal Drainage Area.
\c\ Bone Valley region includes the following watersheds: Tampa Bay
  Watershed, Sarasota Bay Watershed, and Charlotte Harbor Watershed.
\d\ Peninsula region includes the following watersheds: Waccasassa
  Coastal Drainage Area, Withlacoochee Coastal Drainage Area, Crystal/
  Pithlachascotee Coastal Drainage Area, Indian River Watershed,
  Caloosahatchee River Watershed, St. Lucie Watershed, Kissimmee River
  Watershed, St. John's River Watershed, Daytona/St. Augustine Coastal
  Drainage Area, Nassau Coastal Drainage Area, and St. Mary's River
  Watershed.
\e\ North Central region includes the Suwannee River Watershed.

    The following section describes the methodology used to derive the 
proposed numeric nutrient criteria for streams. EPA is soliciting 
comments and scientific data and information regarding these proposed 
criteria and their derivation.
(2) Methodology for Deriving EPA's Proposed Criteria for Streams
    Like other aquatic ecosystems, excess nutrients in streams 
increases vegetative growth (plants and algae), and changes the 
assemblage of plant and algal species present in the system. These 
changes can affect the organisms that are consumers of algae and plants 
in many ways. For example, these changes can alter the available food 
resources by providing more dead plant material versus live plant 
material, or providing algae with a different cell size 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, these changes 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, can also be affected by 
excess nutrients. Each of these changes can, in turn, lead to other 
changes in the stream community and, ultimately, to the stream ecology 
that supports the overall function of the linked aquatic ecosystem.
    Although the general types of adverse effects can be described, not 
all of these effects will occur in every stream at all times. For 
example, some streams are well shaded, which would tend to reduce the 
near-field effect of excess nutrients on primary production because 
light, which is essential for plant or algae growth, does not reach the 
water surface. Some streams are fast moving and pulses of nutrients are 
swiftly carried away before any effect can be observed. However, if the 
same stream widens and slows downstream or the canopy that provided 
shading opens up, then the nutrients present may accelerate plant and 
algal biomass production. As another example, the material on the 
bottom of some streams, referred to as substrate, is frequently scoured 
from intense rain storms. These streams may lack a natural grazing 
community to consume excess plant growth and may be susceptible to 
phytoplankton algae blooms during periods when water velocity is slower 
and water residence time is longer. The effects of excess nutrients may 
be subtle or dramatic, easily captured by measures of plant and algal 
response (such as chlorophyll a) or not, and may occur in some 
locations along a stream but not others.
    Notwithstanding natural environmental variability, there are well 
understood and documented analyses and principles about the underlying 
biological effects of TN and TP on an aquatic ecosystem. There is a 
substantial and compelling scientific basis for the conclusion that 
excess TN and TP will have adverse effects; however, it is often 
unclear where precisely the impacts will occur. The value of regional 
numeric nutrient criteria for streams is that the substantial 
expenditure of time and scarce public resources to document and 
interpret inevitable and expected stream variability on a site-by-site, 
segment-by-segment basis (i.e., as in the course of interpreting a 
narrative WQS for WQBELs and TMDL estimations) is no longer necessary. 
Rather, regional numeric nutrient criteria for streams allows an 
expedited and expanded level of aquatic protection across watersheds 
and greatly strengthens local and regional capacity to support and 
maintain State designated uses throughout aquatic ecosystems. In terms 
of environmental outcomes, the result is a framework of expectations 
and standards that is able to extend the protection needed to restore 
and maintain valuable aquatic resources to entire watersheds and 
associated aquatic ecosystems. At the same time, the ability to 
promulgate SSAC, as well as other flexibilities discussed in this 
proposal, allows the State to continue to address water bodies where 
substantial data and analyses show that the regional criteria may be 
either more stringent than necessary or not stringent enough to protect 
designated uses.
    As mentioned earlier, to effectively apply this well understood and 
documented science, EPA has recommended that nutrient criteria

[[Page 4193]]

include both causal (e.g., TN and TP) and response variables (e.g., 
chlorophyll a and some measure of clarity) for water bodies.\59\ EPA 
recommends causal variables, in part, to have the means to develop 
source control targets and, in part, to have the means to assess stream 
condition with knowledge that responses can be variable, suppressed, 
delayed, or expressed at different locations. EPA recommends response 
variables, in part, to have a means to assess stream condition that 
synthesizes the effect of causal variables over time, recognizing the 
daily, seasonal, and annual variability in measured nutrient 
levels.\60\
---------------------------------------------------------------------------

    \59\ U.S. EPA. 1998. National Strategy for the Development of 
Regional Nutrient Criteria. Office of Water, Washington, DC. EPA 
822-R-98-002; Grubbs, G. 2001. U.S. EPA. (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. November 14, 2001); Grumbles, B.H. 2007. U.S. EPA. 
(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. May 25, 2007).
    \60\ U.S. EPA. 2000. Nutrient Criteria Technical Guidance 
Manual: Rivers and Streams. Office of Water, Washington, DC. EPA-
822-B-00-002.
---------------------------------------------------------------------------

    The ability to establish protective criteria for both causal and 
response variables depends on available data and scientific approaches 
to evaluate these data. Whereas, there are data available for water 
column chlorophyll a (phytoplankton) and algal thickness on various 
substrates (periphyton) for certain types of streams in Florida, there 
are currently no available approaches to interpret these data to infer 
scientifically supported thresholds for these nutrient-specific 
response variables in Florida streams. Additionally, in previously 
published guidance,\61\ EPA has recommended water clarity as a response 
variable for numeric nutrient criteria because algal density in a water 
column results in turbidity, and thus a related decrease in water 
clarity can serve as an indicator of excess algal growth. For water 
clarity, Florida has criteria for transparency and turbidity, 
applicable to all Class I and III waters, expressed in terms of a 
measurable deviation from natural background (32-302.530(67) and (69), 
F.A.C.). Therefore, EPA is not proposing criteria for any response 
variable in Florida's streams at this time, however, EPA will consider 
additional data that becomes available during the comment period. One 
approach for deriving criteria for water quality variables such as a 
measure for water clarity or chlorophyll a, could be to apply a 
statistical distribution approach to a population of streams for each 
of the proposed NWRs. This approach is further described in previous 
EPA guidance.\62\
---------------------------------------------------------------------------

    \61\ U.S. EPA. 2000. Nutrient Criteria Technical Guidance 
Manual: Lakes and Reservoirs. Office of Water, Washington, DC. EPA-
822-B-00-001; U.S. EPA. 2000. Nutrient Criteria Technical Guidance 
Manual: Rivers and Streams. Office of Water, Washington, DC. EPA-
822-B-00-002; U.S. EPA. 2001. Nutrient Criteria Technical Manual: 
Estuarine and Coastal Marine Waters. Office of Water, Washington, 
DC. EPA-822-B-01-003.
    \62\ U.S. EPA. 2000. Nutrient Criteria Technical Guidance 
Manual: Rivers and Streams. Office of Water. 4304. EPA-822-B-00-002.
---------------------------------------------------------------------------

    For Florida streams, EPA has determined that there are sufficient 
available data on TN and TP concentrations with corresponding 
information on biological condition for a wide variety of stream types 
that can be used to derive numeric nutrient criteria for those causal 
variables. EPA used multiple measures of stream condition (or metrics) 
that describe the biological condition of the benthic invertebrate 
community. EPA then coupled the stream condition metrics with 
associated measurements of TN and TP concentrations to provide the 
basis for deriving causal variable numeric nutrient criteria.
    EPA's proposed instream numeric nutrient criteria for Florida's 
streams are based upon EPA's evaluation of data on TN and TP levels in 
rivers and streams that have been carefully evaluated by FDEP, and 
subsequently by EPA, on a site-specific basis and identified as 
biologically healthy. EPA's approach results in numeric criteria that 
are protective of the streams themselves. EPA has determined, however, 
that these instream values may not always be protective of the 
designated uses in downstream lakes and estuaries. Therefore, EPA has 
also developed an approach for deriving TN and TP values for rivers and 
streams to ensure the protection of downstream lakes and estuaries. 
This approach is discussed in Section III.C(6).
(a) Methodology for Stream Classification: EPA's Nutrient Watershed 
Regions (NWRs)
    EPA classified Florida's streams north of Lake Okeechobee by 
separating watersheds with a substantially different ratio of TN and TP 
export 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. This watershed classification also 
facilitates the ability to address the effects of TN and TP from 
streams to downstream lakes or estuaries in the same watershed.
    EPA's classification approach results in four watershed regions: 
the Panhandle, the Bone Valley, the Peninsula, and the North Central 
(for a map of these regions, refer to the EPA TSD for Florida's Inland 
Waters or the list of watersheds in the table above). These four 
regions do not include the south Florida region (corresponding to 
FDEP's Everglades Bioregion) that is addressed separately in Section 
III.E which sets out EPA's proposed numeric nutrient criteria for 
canals in south Florida. All flowing waters in this region are either a 
canal or a wetland.
    When classifying Florida's streams, EPA identified geographic areas 
of the State as having phosphorus-rich soils and geology, such as the 
Bone Valley and the northern Suwannee River watershed. As indicated 
above, the Bone Valley region and the Suwannee River watersheds are 
classified in this proposal as separate NWRs because it is well 
established that the naturally phosphorus-rich soils in these areas 
significantly influence stream phosphorus concentrations in these 
watersheds. EPA would expect from a general ecological standpoint that 
the associated aquatic life uses, under these naturally-occurring, 
nutrient-rich conditions, would be supported. The Agency requests 
comment on this particular classification decision (regions based on 
phosphorus-rich soils), as well as an alternate classification approach 
that would not separate out the phosphorus-rich watersheds described in 
this notice. The latter approach is similar to the approach proposed by 
EPA, but would not result in separate NWRs for the Bone Valley and/or 
North Central. Rather these NWRs would be integrated within the other 
NWRs.
(b) The Use of the Stream Condition Index as an Indicator of 
Biologically Healthy Conditions
    For EPA's proposed approach, the Agency utilized a multi-metric 
index of benthic macroinvertebrate community composition and taxonomic 
data known as the Stream Condition Index (SCI) developed by FDEP to 
assess the

[[Page 4194]]

biological health of Florida's streams.\63\ Of the metrics that 
comprise the SCI, some decrease in response to human disturbance-based 
stressors, such as excess nutrients; for example, (1) total taxa 
richness, (2) richness of Ephemeroptera (mayflies), (3) richness of 
Plecoptera (stoneflies), (4) percentage of sensitive taxa, and (5) 
percentage of filterers and suspension feeders. Other metrics increase 
in response to human disturbance-based stressors; for example, percent 
of very tolerant taxa (e.g., Genera Prostoma, Lumbriculus) and percent 
of the dominant taxa (i.e., numerical abundance of the most dominant 
taxon divided by the total abundance of all taxa).
---------------------------------------------------------------------------

    \63\ The SCI method was developed and calibrated by FDEP. See 
``Fore et al. 2007. Development and testing biomonitoring tools for 
macroinvertebrates in Florida streams (Stream Condition Index and 
BioRecon). Final report to Florida Department of Environmental 
Protection'' and the EPA TSD for Florida's Inland Waters for more 
information on the SCI.
---------------------------------------------------------------------------

    The SCI was developed by FDEP in 2004, with subsequent revisions in 
2007 to reduce the variability of results. In order to ensure that data 
are produced with the highest quality, field biologists and lab 
technicians must follow detailed Standard Operating Procedures (SOPs) 
and additional guidance for sampling and data use provided through a 
FDEP document entitled ``Sampling and Use of the Stream Condition Index 
(SCI) for Assessing Flowing Waters: A Primer (DEP-SAS-001/09).'' Field 
biologists must pass a rigorous audit with FDEP, and laboratory 
taxonomists are regularly tested and must maintain greater than 95% 
identification accuracy.
    EPA considered two lines of evidence in determining the SCI range 
of scores that would indicate biologically healthy systems. The first 
line of evidence was an evaluation of SCI scores in streams considered 
by FDEP to be least-disturbed streams in Florida. A statistical 
analysis balanced the probability of a stream being included in this 
reference set with the probability of a stream not being included in 
this reference set, and indicated that an SCI score of 40 was an 
appropriate threshold. SCI scores range from 1 to 100 with higher 
scores indicating healthier biology.
    A second line of evidence was the result of an expert workshop 
convened by FDEP in October 2006. The workshop included scientists with 
specific knowledge and expertise in stream macroinvertebrates. These 
experts were asked to individually and collectively evaluate a range of 
SCI data (i.e., macroinvertebrate composition and taxonomic data) and 
then assign those data into one of the six Biological Condition 
Gradient (BCG) \64\ categories, ranging from highly disturbed (Category 
6) to pristine (Category 1). EPA analyzed the results of these 
categorical assignments using a proportional odds regression model \65\ 
that predicts the probability of an SCI score occurring within one of 
the BCG categories by overlapping the ranges of SCI scores associated 
with each category from the individual expert assignment. The results 
of the analysis provided support for identifying a range of SCI scores 
that minimized the probability of incorrectly assigning a low quality 
site to a high quality category, and incorrectly assigning a high 
quality site to a low quality category, using the collective judgment 
of expert opinion. The results indicated a range of SCI scores of 40-44 
to represent an appropriate threshold of healthy biological condition. 
Please refer to the EPA TSD for Florida's Inland Waters for more 
information on such topics as EPA's estimates of the Type I and Type II 
error associated with various threshold values. Thus, two very 
different approaches yielded comparable results. A subsequent EPA 
statistical analysis indicated that nutrient conditions in Florida 
streams within different regions remain essentially constant within an 
SCI score range of 40-50 providing further support for a selection of 
40 as a threshold that is sufficiently protective for this application. 
The resulting TN and TP concentrations associated with a SCI score of 
40 versus 50 did not represent a statistical difference and 40 was more 
in line with other lines of evidence for a SCI score threshold.
---------------------------------------------------------------------------

    \64\ Appendix H in ``Fore et al. 2007. Development and testing 
biomonitoring tools for macroinvertebrates in Florida streams 
(Stream Condition Index and BioRecon). Final report to Florida 
Department of Environmental Protection''.
    \65\ See the EPA TSD for Florida's Inland Waters for more 
information on the proportional odds regression model.
---------------------------------------------------------------------------

(c) Methodology for Calculating Instream Protection Values: The 
Nutrient Watershed Region Distribution Approach
    EPA evaluated several methodologies, including reference conditions 
and stressor-response relationships, to develop values that protect 
designated uses of Florida streams instream. EPA analyzed stressor-
response relationships in Florida streams based on available data, but, 
as mentioned above, did not find sufficient scientific support for 
their use in the derivation of numeric nutrient criteria for Florida 
streams. More specifically, EPA was not able to demonstrate a 
sufficiently strong correlation between the biological response 
indicators (e.g., chlorophyll a, periphyton biomass, or SCI) and TN or 
TP concentrations. Thus, the Agency could not confidently predict a 
specific biological response (such as an SCI score) for an individual 
stream solely from the associated stream measurements of TN or TP 
concentrations.
    There may be several reasons why empirical relationships between 
field-derived data of nutrient stressor and biological response 
variables show a relatively weak correlation. First, the relationship 
between nutrient concentrations and a biological response, such as 
algal growth, can be confounded by the presence of other stressors. For 
example, other stressors, such as excessive scour could cause low 
benthic invertebrate diversity, as measured by the SCI, even where 
nutrients are low. Excessive scour could also suppress a biological 
response (such as chlorophyll a or periphyton biomass) when nutrients 
are high. Another reason for stressor-response relationships with low 
correlations is that algal biomass accumulation is difficult to 
characterize because dynamic conditions in an individual stream can 
allow algae to accumulate and be removed rapidly, which is difficult to 
capture with periodic monitoring programs.
    As an alternative to the stressor-response approach, EPA analyzed 
the TN and TP concentrations associated with a healthy biological 
condition in streams, and examined the statistical distributions of 
these data in order to identify an appropriate threshold for providing 
protection of aquatic life designated uses. To derive the instream 
protection values under this approach, EPA first assembled the 
available nutrient concentrations and biological response data for 
streams in Florida. EPA used FDEP's data from the IWR and STORET \66\ 
databases and identified sites where SCI scores were 40 and higher. EPA 
further screened these sites by cross-referencing them with Florida's 
CWA section 303(d) list for Florida and excluded sites with identified 
nutrient impairments or dissolved oxygen impairments associated with 
elevated nutrients. EPA grouped the remaining sites (hereafter, 
biologically healthy sites) according to its nutrient watershed regions 
(Panhandle, Bone Valley, Peninsula, and North Central). For each 
nutrient watershed region, EPA compiled nutrient data (TN and TP

[[Page 4195]]

concentrations) associated with the biologically healthy sites, and 
calculated distributional statistics for annual average TN and TP 
concentrations.
---------------------------------------------------------------------------

    \66\ FL IWR and STORET can be found at: http://www.dep.state.fl.us/WATER/STORET/INDEX.HTM.
---------------------------------------------------------------------------

    The second step in deriving instream protection values was to 
further characterize the distribution of TN and TP among biologically 
healthy sites. Specifically, EPA calculated the number of biologically 
healthy sites within integer log-scale ranges of TN and TP 
concentrations, as well as the cumulative distribution. These nutrient 
distributions from biologically healthy sites in each nutrient 
watershed region are represented on a log-scale because concentration 
data are typically log-normally distributed. A log-normal distribution 
is skewed, with a mode near the geometric mean rather than the 
arithmetic mean.
    The third step in deriving instream protection values was to 
determine appropriate thresholds from these distributions for providing 
protection of aquatic life designated uses. Selection of a central 
tendency of the distribution (i.e., the median or geometric mean of a 
log-normal distribution) would imply that half of the biologically 
healthy sites are not attaining their uses. In contrast, an extreme 
upper end of the distribution (e.g., the 90th or 95th percentile) may 
be the most likely to be heavily influenced by extreme event factors 
that are not representative of typically biologically healthy sites. 
This might be the case because the upper tail of the distribution might 
reflect a high loading year (landscape and/or atmospheric), and/or lack 
of nutrient uptake by algae (in turn due to a myriad of physical and 
biological factors like scour, grazing, light limitation, other 
pollutants). Thus, this tail of the distribution may just represent the 
most nutrient ``tolerant'' among the sites. Another possibility is that 
these streams may experience adverse effects from nutrient enrichment 
that are not yet reflected in the SCI score. A reasonable choice for a 
threshold is one which lies just above the vast majority of the 
population of healthy streams. This choice is reasonable because it 
reflects a point where most biologically healthy sites will still be 
identified as attaining uses, but avoids extrapolations into areas of 
the distribution characterized by only a few data points (as would be 
the case for the 90th or 95th percentile). When a threshold is 
established as a water quality criterion, sites well below that 
threshold might be allowed to experience an increase in nutrient levels 
up to the threshold level. There is little assurance that biologically 
healthy sites with nutrient concentrations well below the 90th or 95th 
percentile would remain biologically healthy if nutrient concentrations 
increased to those levels because relatively few sites with nutrient 
concentrations as high as those at the 90th or 95th percentile are 
demonstrated to be biologically healthy.
    The range between the 25th and 75th percentiles, or inter-quartile 
range, is a common descriptive statistic used to characterize a 
distribution of values. For example, statistical software packages 
typically include the capability to display distributions as ``box and 
whisker'' plots, which very prominently identify the inter-quartile 
range. The inter-quartile range of a log normal distribution spans a 
smaller range of values than the inter-quartile range of a distribution 
of the data evenly spread across the entire range of values. This means 
that the further a value goes past the 75th percentile of a log normal 
distribution, the less representative it is of the majority of data (in 
this case, less representative of biologically healthy sites). Within 
the inter-quartile range of a log normal distribution, the slope of the 
cumulative frequency distribution will be the greatest. The 75th 
percentile represents a reasonable upper bound of where there is the 
greatest confidence that biologically healthy sites will be 
represented. Beyond the inter-quartile range (i.e., below the 25th 
percentile and above the 75th percentile), there is a greater chance 
that measurements may represent anomalies that would not correspond to 
long-term healthy conditions in the majority of streams. Based on this 
analysis, EPA concluded that the 75th percentile represents an 
appropriate and well-founded protective threshold derived from a 
distribution of nutrient concentrations from biologically healthy 
sites. EPA solicits comment on its analysis of what constitutes a 
protective threshold.
(d) Proposed Criteria: Duration and Frequency
    Aquatic life water quality criteria contain three components: 
Magnitude, duration, and frequency. For the TN and TP numeric criteria 
for streams, the derivation of the criterion-magnitude values is 
described above and these values are provided in the table in Section 
III.C(1). The criterion-duration of this magnitude is specified in 
footnote a of the streams criteria table as an annual geometric mean. 
EPA is proposing two expressions of allowable frequency, both of which 
are to be met. First, EPA proposes a no-more-than-one-in-three-years 
excursion frequency for the annual geometric mean criteria for lakes. 
Second, EPA proposes that the long-term arithmetic average of annual 
geometric means not to exceed the criterion-magnitude concentration. 
EPA anticipates that Florida will use their standard assessment periods 
as specified in Rule 62-303, F.A.C. (Impaired Waters Rule) to implement 
this second provision. These proposed 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 an occasionally elevated year of nutrient 
loadings. The Agency requests comment on these proposed duration and 
frequency components of the stream numeric nutrient criteria.
    EPA notes that some scientists and resource managers have suggested 
that nutrient criteria duration and frequency expressions should be 
more restrictive to avoid seasonal or annual ``spikes'' from which the 
aquatic system cannot easily recover, whereas others have suggested 
that criteria expressed as simply a long-term average of annual 
geometric means, consistent with data used in criteria derivation, and 
would still be protective. EPA requests comment on alternative duration 
and frequency expressions that might be considered protective, 
including (1) a criterion-duration expressed as a monthly average or 
geometric mean, (2) a criterion-frequency expressed as meeting 
allowable magnitude and duration every year, (3) a criterion-frequency 
expressed as meeting allowable magnitude and duration in more than half 
the years of a given assessment period, and (4) a criterion-frequency 
expressed as meeting allowable magnitude and duration as a long-term 
average only. EPA further requests comment on whether an expression of 
the criteria in terms of an arithmetic average of annual geometric mean 
values based on rolling three-year periods of time would also be 
protective of the designated use.
 (3) Request for Comment and Data on Proposed Approach
    EPA is soliciting comments on the approaches taken by the Agency to 
derive these proposed criteria, the data underlying those approaches, 
and the proposed criteria specifically. EPA is requesting that the 
public submit any other scientific data and information that may be 
available related to nutrient concentrations and associated biological 
responses in Florida's streams. EPA is

[[Page 4196]]

soliciting comment specifically on the selection of criteria parameters 
for TN and TP; the proposed classification of streams into four regions 
based on aggregated watersheds; and the conclusion that the proposed 
criteria for streams are protective of designated uses and adequately 
account for the spatial and temporal variability of nutrients. In 
addition, EPA requests comment on folding the Suwannee River watershed 
in north central Florida into the larger Peninsula NWR (i.e., not 
having a separate North Central region) or, alternatively, making a 
smaller North Central region within Hamilton County alone where the 
highest phosphorus-rich soils are located, with the remainder of the 
North Central becoming part of the Peninsula Region.
(4) Alternative Approaches Considered by EPA
    During EPA's review of the available data and information for 
derivation of numeric nutrient criteria for Florida's streams, EPA also 
considered an alternative approach for criteria derivation. EPA is 
specifically requesting comment on a modified reference condition 
approach called the benchmark distribution approach, as described 
below.
(a) Benchmark Distribution Approach
    EPA's previously published guidance has recommended a variety of 
methods to derive numeric nutrient criteria.\67\ One method, the 
reference condition approach, relies on the identification of reference 
waters that exhibit minimal impacts from anthropogenic disturbance and 
are known to support designated uses. The thresholds of nutrient 
concentrations where designated uses are in attainment are calculated 
from a distribution of the available associated measurements of ambient 
nutrient concentrations at these reference condition sites.
---------------------------------------------------------------------------

    \67\ U.S. EPA. 2000. Nutrient Criteria Technical Guidance 
Manual: Rivers and Streams. Office of Water. 4304. EPA-822-B-00-002.
---------------------------------------------------------------------------

    EPA is seeking comment on a modified reference condition approach, 
which was developed by FDEP and is referred to as the benchmark 
distribution approach. The benchmark approach relies on least-disturbed 
sites rather than true reference, or minimally-impacted, sites. The 
benchmark distribution is a step-wise procedure used to calculate 
distributional statistics of TN and TP from identified least-disturbed 
streams.
(i) Identification of Least-Disturbed Streams
    FDEP identified benchmark stream sites in the following step-wise 
manner (1) compiled a list of sites with low landscape development 
intensity using FDEP's Landscape Development Intensity Index,\68\ (2) 
eliminated any sites on Florida's CWA section 303(d) list of impaired 
waters due to nutrients, as well as certain sites impaired for 
dissolved oxygen, where the State determined the dissolved oxygen 
impairment was caused by nutrients, (3) eliminated any sites with 
nitrate concentrations greater than FDEP's 0.35 mg/L proposed nitrate-
nitrite criterion in order to reduce the possibility of including sites 
with far-field human disturbance from groundwater impacts, (4) 
eliminated sites known by FDEP district scientists to be disturbed, (5) 
eliminated potentially erroneous data through outlier analysis, (6) 
verified sites using high resolution aerial photographs, and (7) 
verified a random sample of the sites in the field.
---------------------------------------------------------------------------

    \68\ A quantitative, integrated measure of the degree of human 
landscape disturbance within 100 meters on either side of a 
specified stream reach and extending to 10 kilometers upstream of 
the same stream reach.
---------------------------------------------------------------------------

(ii) Calculation of Benchmark Distribution Approach and Selection of 
Percentiles From the Benchmark Distribution
    FDEP selected either the 75th or 90th percentile of the benchmark 
distribution approach from FDEP's proposed nutrient regions (75th 
percentile--Bone Valley; 90th percentile--Panhandle, North Central, 
Northeast, and Peninsula). FDEP's rationale for selecting either the 
75th or 90th percentiles was based on the degree of certainty regarding 
the benchmark sites reflecting least-disturbed conditions and a 
probability (10% for the 90th percentile) of falsely identifying a 
least-disturbed site as being impaired for nutrients.
    With this approach, the distribution of available annual geometric 
means of nutrient concentrations for the benchmark sites within the 
regional classes of streams is calculated. To compute the numeric 
criteria for the causal variables, TN, and TP, EPA is seeking comment 
on whether the 75th or 90th percentile of the benchmark distribution 
for each nutrient stream region should be selected. As mentioned above, 
the rationale for selecting either the 75th or 90th percentiles is 
based on the degree of certainty regarding the benchmark sites 
reflecting least-disturbed conditions and a probability of falsely 
identifying a least-disturbed site as being impaired for nutrients or 
vice-versa. In cases where data are more limited for a given nutrient 
region (i.e., in the Bone Valley there were only four sites), the 75th 
percentile may be more appropriate because the 90th percentile may not 
be sufficiently robust (i.e., may be highly sensitive to a few data 
points). In other cases, the 90th percentile may be more appropriate 
when there is a more extensive data set. For further information, 
please refer to EPA's TSD for Florida's Inland Waters, Chapter 2: 
Methodology for Deriving U.S. EPA's Proposed Criteria for Streams.
    In evaluating whether to propose this approach, EPA determined that 
a considerable amount of uncertainty remained whether this approach 
would result in a list of benchmark sites that represented truly least-
disturbed conditions. Specifically, EPA is concerned that nutrient 
concentrations at these sites may reflect anthropogenic sources (e.g., 
sources more than 100 meters away from and/or 10 kms upstream of the 
segment), even if the sites appear least-disturbed on a local basis. 
EPA is particularly concerned that several benchmark sites in the FDEP 
dataset appear to have a high potential to be affected by 
fertilizations associated with forestry activities. FDEP provided an 
analysis in which FDEP concluded that this is not likely.\69\ EPA 
solicits comment on this issue and more generally on whether the 
benchmark sites identified by FDEP in its July 2009 proposal are an 
appropriate set of least-disturbed sites on which to base the criteria 
calculations.
---------------------------------------------------------------------------

    \69\ FDEP document titled, ``Responses to Earthjustice's 
Comments on the Department's Reference Sites.'' Draft October 2, 
2009. Located in the docket ID EPA-HQ-OW-2009-0596.
---------------------------------------------------------------------------

(5) Request for Comment and Data on Alternative Approach
    EPA is soliciting comment on the alternative to deriving numeric 
nutrient criteria for Florida's streams as described in Section 
III.C(4).
(6) Protection of Downstream Lakes and Estuaries
    Two key objectives of WQS are: First, to protect the immediate 
water body to which a criterion initially applies and, second, to 
ensure that criteria provide for protection of downstream WQS affected 
by flow of pollutants from the upstream water body. See 40 CFR 131.11 
and 131.10(b). EPA WQS regulations reflect the importance of protecting 
downstream waters by requiring that upstream WQS ``provide for the 
attainment and maintenance of the water quality standards of

[[Page 4197]]

downstream waters.'' 40 CFR 131.10(b). Thus, in developing numeric 
nutrient criteria for Florida, EPA considered both instream aquatic 
conditions and downstream aquatic ecosystem needs. In addressing the 
issue of how, if at all, instream criteria values need to be adjusted 
to assure attainment of downstream standards, EPA necessarily examined 
the WQS for downstream lakes and estuaries. For lakes, this analysis 
starts with the numeric nutrient criteria proposed in this notice. For 
estuaries, this notice proposes an analytical approach to determine the 
loadings that a particular estuary can receive and still assure 
attainment and maintenance of the State's WQS for the estuary (i.e., a 
protective load). An approach is then proposed for translating those 
downstream loading values into criteria levels in the contributing 
watershed stream reaches in a manner that ensures that the protective 
downstream loadings are not exceeded.
    In connection with both lakes and estuaries, EPA fully recognizes 
that there are a range of important technical questions and related 
significant issues raised by this proposed approach for developing 
instream water quality criteria that are protective of downstream 
designated uses. With regard, in particular, to the protection of 
estuaries, the Agency is working closely with FDEP to derive estuarine 
numeric nutrient criteria for proposal and publication in 2011. Even 
though estuarine numeric nutrient criteria will be developed in 2011, 
there is already a substantial body of information, science, and 
analysis that presently exists that should be considered in determining 
flowing water criteria that are protective of downstream water quality.
    The substantial data, peer-reviewed methodologies, and extensive 
scientific analyses available to and conducted by the Agency to date 
indicate that numeric nutrient criteria for estuaries, when proposed 
and finalized in 2011, may result in the need for more stringent rivers 
and streams criteria to ensure protection of downstream water quality, 
particularly for the nitrogen component of nutrient pollution. 
Therefore, considering the numerous requests for the Agency to share 
its analysis and scientific and technical conclusions at the earliest 
possible opportunity to allow for full review and comment, EPA is 
including downstream protection values for TN as proposed criteria for 
rivers and streams to protect the State's estuaries in this notice.
    As described in more detail below and in EPA's TSD for Florida's 
Inland Waters accompanying this notice, these proposed nitrogen 
downstream protection values are based on substantial data, thorough 
scientific analysis, and extensive technical evaluation. However, EPA 
recognizes that additional data and analysis may be available for 
particular estuaries to help inform what water quality criteria are 
necessary to protect these waters. EPA also recognizes that substantial 
site-specific work (including some very sophisticated analyses in the 
context of certain TMDLs) has been completed for a number of these 
estuaries. This notice and the proposed downstream protection values 
are not intended to address or be interpreted as calling into question 
the utility and protectiveness of these site-specific analyses. Rather, 
the proposed values represent the output of a systematic and scientific 
approach that may be generally applicable to all flowing waters in 
Florida that terminate in estuaries for the purpose of ensuring the 
protection of downstream estuaries. EPA is interested in obtaining 
feedback at this time on this systematic and scientific approach. The 
Agency further recognizes that the proposed values in this notice will 
need to be considered in the context of the Agency's numeric nutrient 
criteria for estuaries scheduled for proposal in January of 2011. At 
this time, EPA plans to finalize any necessary downstream protection 
values for nitrogen in flowing waters as part of the second phase of 
this rulemaking process in coordination with the proposal and 
finalization of numeric criteria for estuarine and coastal waters in 
2011. However, if comments, data and analyses submitted as a result of 
this proposal support finalizing such values sooner, by October 2010, 
EPA may choose to proceed in this manner. To facilitate this process, 
EPA requests comments and welcomes thorough evaluation on the need for 
and the technical and scientific basis of these proposed downstream 
protection values as part of the broader comment and evaluation process 
that this proposal initiates.
    EPA believes that a detailed consideration and related proposed 
approach to address protection of downstream water quality in this 
proposal is necessary for several reasons, including (1) water quality 
standards are required to protect downstream uses under Federal 
regulations at 40 CFR 131.10(b), meaning also for prevention of 
impairment; (2) it may be a relevant consideration in the development 
of any TMDLs, NPDES permits, and Florida BMAPs that the State completes 
in the interim period between the final rule for Florida lakes and 
flowing waters in October 2010 and a final rule for Florida estuarine 
and coastal waters in October of 2011; and (3) perhaps most 
importantly, it is essential for informing and supporting a transparent 
and engaged public consideration, evaluation, and discussion on the 
question of what existing information, tools, and analyses suggest 
regarding the need to ensure protection of downstream waters. The 
Agency continues to emphasize its interest in and request for 
additional information, further analysis, and any alternative 
technically-based approaches that may be available to address 
protection of downstream water quality. EPA also reiterates its 
commitment to a full evaluation of all comments received and notes the 
ability to issue a NODA to allow a full public review should 
significant new additional information and analysis become available as 
part of the comment period.
    In deriving criteria to protect designated uses, as noted above, 
Federal WQS regulations established to implement the CWA provide WQS 
must provide for the protection of designated uses in downstream 
waters. In the case of deriving numeric nutrient criteria for streams 
in Florida, EPA's analyses reflected in this notice indicate that the 
proposed criteria values for instream protection of streams may not 
fully protect downstream lakes and downstream estuaries. EPA's proposed 
criteria for lakes are, in some cases, more stringent than the proposed 
criteria for streams that flow into the lakes. For estuaries, EPA's 
analyses of protective loads delivered to a specific estuary, and the 
corresponding expected concentration values for streams that flow into 
that estuary, indicate the proposed criteria for instream protection 
may not always be sufficient to provide for the attainment and 
maintenance of the estuarine WQS. For more detailed information, please 
consult EPA's TSD for Florida's Inland Waters, Chapter 2: Methodology 
for Deriving U.S. EPA's Proposed Criteria for Streams.
    To address each of these issues, EPA is proposing first, for lakes, 
an equation that allows for input of lake characteristics to determine 
the concentration in flowing streams that is needed to attain and 
maintain the receiving lake's designated use and protective criteria. 
Second, for estuaries, EPA is proposing an approach for identifying the 
total nutrient loads a particular estuary can receive and still attain 
and maintain the State's designated use for the water body.

[[Page 4198]]

Third, also for estuaries, the Agency is proposing a methodology to 
derive protective concentration values for the instream criteria where 
necessary to assure that downstream estuarine loads are not exceeded. 
The following sections provide a more detailed explanation of the 
proposed downstream protective approach for lakes and then for 
estuaries.
(a) Downstream Protection of Lakes
    EPA is proposing an equation to relate a lake TP concentration 
criterion to the concentration needed to be met in incoming streams to 
support the lake criterion. EPA proposes to apply the resulting stream 
concentration as the applicable criterion for all stream segments 
upstream of the lake. EPA used a mathematical modeling approach to 
derive this equation, with allowable input of lake-specific 
characteristics, to calculate protective criteria necessary to assure 
attainment and maintenance of the numeric lake nutrient criteria in 
this proposal. More specifically, EPA started with a phosphorus loading 
model equation first developed by Vollenweider.\70\ EPA assumed that 
rainfall exceeds evaporation in Florida lakes and that all external 
phosphorus loading comes from streams. EPA considers the first 
assumption reasonable given the rainfall frequency and volume in 
Florida. The second assumption is reasonable to the extent that surface 
runoff contributions are far greater than groundwater or atmospheric 
sources of TP in Florida lakes. EPA requests comment on both these 
assumptions. After expressing these assumptions in terms of the 
mathematical relationships among loading rates, stream flow, and lake 
and stream concentrations, EPA derived the following equation to relate 
a protective lake criterion to a corresponding protective stream 
concentration:
---------------------------------------------------------------------------

    \70\ 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.
[GRAPHIC] [TIFF OMITTED] TP26JA10.000

---------------------------------------------------------------------------
where:

[TP]<INF>S</INF> is the total phosphorus (TP) downstream lake 
protection value, mg/L
[TP]<INF>L</INF> is applicable TP lake criterion, mg/L
c<INF>f</INF> is the fraction of inflow due to all stream flow, 0 <= 
c<INF>f</INF> <= 1
[tau]<INF>w</INF> is lake's hydraulic retention time (water volume 
divided by annual flow rate)
The term
[GRAPHIC] [TIFF OMITTED] TP26JA10.005

expresses the net phosphorus loss from the water column (e.g. via 
settling of sediment-sorbed phosphorus) as a function of the lake's 
retention time

    This model equation requires input of two lake-specific 
characteristics: The fraction of inflow due to stream flow and the 
hydraulic retention time. Water in a lake can come from a combination 
of groundwater sources, rainfall, and streams that flow into it. Using 
the model equation above, the calculated stream TP criterion to protect 
a downstream lake will be more stringent for lakes where the portion of 
its volume coming from streams flowing into it is the greatest. In 
addition, the calculated stream TP criterion to protect a downstream 
lake will be more stringent for lakes with short hydraulic retention 
times (how long water stays in a lake) because the longer the water 
stays in the lake, the more phosphorus will settle out in the 
underlying lake sediment.
    Because lake-specific input values may not always be readily 
available, EPA is providing preset values for percent contribution from 
stream flow and hydraulic retention time. In Florida lakes, rainfall 
and groundwater sources tend to contribute a large portion of the total 
volume of lake water. In fact, only about 20% of the more than 7,000 
Florida lakes have a stream flowing into them,\71\ with the rest 
entirely comprised of groundwater and rainwater sources. EPA evaluated 
representative values for percent contribution from stream flow \72\ 
and hydraulic retention time,\73\ and selected 50% stream flow 
contribution and 0.2 years (about two and a half months) retention time 
as realistic and representative preset values to provide a protective 
outcome for Florida lakes, in the absence of site-specific data. Using 
these preset values, streams that flow into colored lakes would have a 
TP criterion of 0.12 mg/L, and streams that flow into clear, alkaline 
lakes would have a TP criterion of 0.073 mg/L, with respect to 
downstream lake protection. In the Peninsula NWR, this compares to a 
0.107 mg/L TP stream criterion protective of instream designated uses. 
EPA's proposed rule does offer the flexibility to use site-specific 
inputs to the Vollenweider equation for fraction of inflow from 
streamflow and hydraulic retention time, as long as data supporting 
such inputs are sufficiently robust and well-documented.
---------------------------------------------------------------------------

    \71\ Fernald, E.A. and E.D. Purdum. 1998. Water Resources Atlas 
of Florida. Tallahassee: Institute of Science and Public Affairs, 
Florida State University.
    \72\ Gao, X. 2006. Nutrient and Unionized Ammonia TMDLs for Lake 
Jesup, WBIDs 2981 and 2981A. Prepared by Florida Department of 
Environmental Protection, Division of Water Resource Management, 
Bureau of Watershed Management, Tallahassee, FL.
    \73\ Steward, J.S. and E.F. Lowe. In Press. General empirical 
models for estimating nutrient load limits for Florida's estuaries 
and inland waters. Limnol. Oceanogr. 55: (in press).
---------------------------------------------------------------------------

    EPA carefully evaluated use of a settling/loss term for phosphorus 
in the model equation. Florida lakes tend to be shallow, and internal 
loadings to the lake water (e.g. from re-suspension of settled 
phosphorus after storms that stir up lake sediment) may be substantial. 
A more detailed model might be able to simulate this phenomenon 
mechanistically, but would likely require substantial site-specific 
data for calibration. For this reason, EPA chose to use the model 
formulation above. EPA considered a simpler alternative to exclude the 
settling/loss term from the above equation, or even to reverse the sign 
on the settling/loss term so that it becomes a net source term, perhaps 
with the inclusion of a default multiplier. However, EPA did not have 
sufficient information to conclude that such a conservative approach 
was necessary as a general application to all Florida lakes. EPA 
remains open and receptive to comment on these alternatives or other 
technically sound and protective approaches. EPA's supporting analyses 
and detailed information on this downstream lake protection methodology 
are provided in the accompanying TSD for Florida's Inland Waters, 
Chapter 2: Methodology for Deriving U.S. EPA's Proposed Criteria for 
Streams.
    The same processes that occur in lakes and affect lake water 
phosphorus concentration may also occur in streams that feed lakes and 
affect stream water phosphorus concentrations. These processes include 
sorption to stream bed sediments, uptake into biota, and release into 
the water column from decaying vegetation. EPA took into consideration 
these processes when deciding whether it would be appropriate to add a 
term to the model equation to account for phosphorus loss or uptake 
within the streams in deriving stream criteria for downstream lake 
protection. However, the net result of these processes is nutrient 
spiraling, whereby nutrients released upstream gradually propagate 
downstream at a rate slower than that of the moving water, and cycle 
into and out of the food chain in the process. Over the short term, the 
result may be water concentrations that decrease in the downstream 
direction. However, unlike for nitrogen, there are no long-term 
phosphorus net removal processes at work in streams. Phosphorus 
adsorbed to sediment particles is eventually

[[Page 4199]]

carried downstream with the sediment, and phosphorus taken up by plants 
is eventually returned to the flowing water. Over the long term, 
upstream phosphorus inputs are in equilibrium with downstream 
phosphorus outputs. Recognizing this feature of stream systems and the 
conservative nature of phosphorus in aquatic environments, EPA 
concluded that it was not appropriate to include a phosphorus loss term 
that would apply to streams as they progress toward a downstream lake. 
For further information, please refer to EPA's TSD for Florida's Inland 
Waters, Chapter 2: Methodology for Deriving U.S. EPA's Proposed 
Criteria for Streams.
    EPA requests comment on the need for additional instream criteria 
to protect uses in downstream lakes. EPA further requests comment on 
the model equation approach presented here to protect downstream lakes, 
and also requests comment on use of an alternative model such as one 
with a negative or zero settling term (i.e., set (1+ 
[radic][tau]<INF>w</INF>) in the equation above either equal to zero or 
with the plus sign switched to a minus sign). EPA also requests comment 
on whether and how to address direct surface runoff into the lake. 
Where this input is substantial and land use around the lake indicates 
that phosphorus input is likely, EPA believes it may be appropriate to 
include this water volume contribution as part of the fraction of 
inflow considered to be streamflow to be protective and consistent with 
the assumption of no loading from sources other than streamflow. EPA 
specifically requests comment on use of the Land Development Index 
(LDI) as an indicator of how to treat this inflow, examination of 
regional groundwater phosphorus levels to see if a zero TP input from 
this source is appropriate, and potential development of regionally-
specific preset values as inputs to the equation. In addition, EPA 
requests comment on the potential to develop a corollary approach for 
nitrogen.
    EPA is open to alternative technically-supported approaches based 
on best available data that offer the ability to address lake-specific 
circumstances. The Agency recognizes that more specific information may 
be readily available for individual lakes which could allow the use of 
alternative approaches such as the BATHTUB model.\74\ The Agency 
welcomes comment and technical analysis on the availability and 
application of these models. In this regard, EPA requests 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 readily and currently available 
data, and whether use of such alternatives should best be facilitated 
through use of the SSAC procedure described in Section V.C.
---------------------------------------------------------------------------

    \74\ 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.
---------------------------------------------------------------------------

(b) Downstream Protection of Estuaries
(i) Overview
    EPA is proposing a methodology for calculation of applicable 
criteria for streams that flow into estuaries and provide for their 
protection. The proposed methodology would allow the State to utilize 
either (1) EPA's downstream protection values (DPVs), or (2) the EPA 
DPV methodology utilizing EPA's estimates of protective loading to 
estuaries but with the load re-distributed among the tributaries to 
each estuary, or (3) an alternative quantitative methodology, based on 
scientifically defensible approaches, to derive and quantify the 
protective load to each estuary and the associated protective stream 
concentrations. The DPV methodology with a re-distributed load may be 
used if the State provides public notice and opportunity for comment. 
To use an alternative technical approach, based on scientifically 
defensible methods to derive and quantify the protective load to each 
estuary and the associated protective stream concentrations, the State 
must go through the process for a Federal SSAC as described in Section 
V.C. In some cases, the substantial and sophisticated analyses and 
scientific effort already completed in the context of the TMDL process 
may provide sufficient support for a SSAC. In such circumstances, EPA 
encourages FDEP to submit these through the SSAC process and EPA looks 
forward to working with FDEP in this process.
    EPA's approach to developing nutrient criteria for streams to 
protect downstream estuaries in Florida involves two separate steps. 
The first step is determining the average annual nutrient load that can 
be delivered to an estuary without impairing designated uses. This is 
the protective load. The second step is determining nutrient 
concentrations throughout the network of streams and rivers that 
discharge into an estuary that, if achieved, are expected to result in 
nutrient loading to estuaries that do not exceed the protective load. 
These concentrations, called ``downstream protection values'' or DPVs, 
depend on the protective load for the receiving estuary and account for 
nutrient losses within streams from natural biological processes. In 
this way, higher DPVs may be appropriate in stream reaches where a 
significant fraction of either TN or TP is permanently removed within 
the reach before delivery to downstream receiving waters. EPA's 
approach utilizes results obtained from a watershed modeling approach 
called SPAtially Referenced Regressions on Watershed attributes, or 
SPARROW.\75\ The specific model that was used is the South Atlantic, 
Gulf and Tennessee (SAGT) regional SPARROW model.\76\ EPA selected this 
model because it provided the information that was needed at the 
appropriate temporal and spatial scales and it applies to all waters 
that flow to Florida's estuaries.\77\ SPARROW was developed by the 
United States Geological Survey (USGS) and has been reviewed, 
published, updated and widely applied over the last two decades. It has 
been used to address a variety of scientific applications, including 
management and regulatory applications.\78\ In order to fully 
understand EPA's methodology for developing DPVs, it is useful to 
understand how the approach utilizes results from SPARROW, as well some 
aspects of how SPARROW works.
---------------------------------------------------------------------------

    \75\ http://water.usgs.gov/nawqa/sparrow.
    \76\ Hoos, A.B., and G. McMahon. 2009. Spatial analysis of 
instream nitrogen loads and factors controlling nitrogen delivery to 
stream in the southeastern United Sates using spatially referenced 
regression on watershed attributes (SPARROW) and regional 
classification frameworks. Hydrological Processes. DOI: 10.1002/
hyp.7323.
    \77\ Hoos, A.B., S. Terziotti,, G. McMahon, K. Savvas, K.C. 
Tighe, and R. Alkons-Wolinsky. 2008. Data to support statistical 
modeling of instream nutrient load based on watershed attributes, 
southeastern United States, 2002: U.S. Geological Survey Open-File 
Report 2008-1163, 50 p.
    \78\ USGS SPARROW publications Web site: http://water.usgs.gov/nawqa/sparrow/intro/pubs.html.

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

[[Page 4200]]

[GRAPHIC] [TIFF OMITTED] TP26JA10.001

    The remaining discussion focuses on TN, for which EPA has already 
computed DPVs. The approach for computing DPVs for TP from estimates of 
the protective TP load is expected to be essentially the same as for 
TN. However, there is some question as to whether the same approach 
used to determine the protective TN load will also apply to TP. EPA 
requests comment on this issue.
(ii) EPA Approach to Estimating Protective Nitrogen Loads for Estuaries
    The first step in EPA's approach is to narrow the range of possible 
values. The protective TN load is expected to vary widely among Florida 
estuaries because they differ significantly in their size and physical 
and biological attributes. For example, well flushed estuaries are able 
to receive higher TN loading without adverse effect compared to poorly 
flushed estuaries. EPA recognized that it may be possible to narrow 
this initially very broad range of possible protective loads using one 
consistent approach, and then consider whether additional information 
might enable a further reduction in uncertainty. EPA is soliciting 
credible scientific evidence that may improve these estimates and 
further reduce uncertainty surrounding the proposed protective loads. 
The most useful evidence would provide a scientific rationale, an 
alternative estimate of the protective load, and an associated 
confidence interval for the estimate. For further information, please 
refer to EPA's TSD for Florida's Inland Waters, Chapter 2: Methodology 
for Deriving U.S. EPA's Proposed Criteria for Streams.
    EPA first narrowed the range of possible protective loads by 
establishing an estimate of current loading as an upper bound. Most of 
Florida's estuaries are listed as impaired to some extent by nutrients 
or nutrient-related causes. Florida's 1998 CWA section 303(d) verified 
list of impaired waters under the Impaired Waters Rule (FAC 62-303) 
identify many estuaries or estuary segments that are impaired by 
nutrients, chlorophyll a, or low dissolved oxygen. Many or most 
estuaries have reduced water clarity and substantial loss of seagrass 
habitats. The National Estuarine Eutrophication Assessment \79\ reports 
that current conditions are poor for many estuaries in Florida. This 
information implies that current levels of TN loading are at least an 
upper limit for the protective load and likely exceed the protective 
load in many estuaries.
---------------------------------------------------------------------------

    \79\ Bricker, S., B. Longstaff, W. Dennison, A. Jones, K. 
Boicourt, C. Wicks and J. Woerner, 2007. Effects of nutrient 
enrichment in the Nation's estuaries: A decade of change. NOAA 
Coastal Ocean Program Decision Analysis Series No. 26. National 
Centers for Coastal Ocean Science, Silver Spring, MD 322.
---------------------------------------------------------------------------

    EPA used the SAGT-SPARROW regional watershed model to estimate 
current loading to each estuary in Florida. While nitrogen loads have 
been estimated from monitored gauge stations in many stream and rivers, 
a large fraction of Florida streams and watersheds are not gauged and 
thus load estimates were not previously available. An approach was 
needed to spatially extrapolate the available measurements of loading 
to obtain estimates of loading for all streams including those in 
unmonitored watersheds or portions of watersheds. The SAGT SPARROW 
model provided these estimates for all Florida estuarine watersheds. 
The SPARROW modeling approach utilizes a multiple regression equation 
to describe the relationship between watershed attributes (i.e., the 
predictors) and measured instream nutrient loads (i.e., the responses). 
The statistical methods incorporated into SPARROW help explain instream 
nutrient water quality data (i.e., the mass flux of nitrogen) as a 
function of upstream sources and watershed attributes. The SAGT-SPARROW 
model utilized period of record monitored streamflow and nutrient water 
quality data from Florida and across the SAGT region for load 
estimation. SAGT-SPARROW also used extensive geospatial data sets 
describing topography, land-use, climate, and soil characteristics, 
nitrogen loading for point sources in Florida obtained from EPA's 
permit compliance system, and estimates of nitrogen in fertilizer and 
manure from county-level fertilizer sales, census of agriculture, and 
population estimates. TN load estimates explain 96% of the variation in 
observed loads from monitoring sites across the region with no spatial 
bias at Florida sites.\80\ A more thorough description of the SAGT-
SPARROW model, the data sources, and analyses are found in the EPA TSD 
for Florida's Inland Waters and in USGS publications.\81\
---------------------------------------------------------------------------

    \80\ Hoos, A.B., and G. McMahon. 2009. Spatial analysis of 
instream nitrogen loads and factors controlling nitrogen delivery to 
stream in the southeastern United Sates using spatially referenced 
regression on watershed attributes (SPARROW) and regional 
classification frameworks. Hydrological Processes. DOI: 10.1002/
hyp.7323.
    \81\ Hoos, A.B., S. Terziotti,, G. McMahon, K. Savvas, K.C. 
Tighe, and R. Alkons-Wolinsky. 2008. Data to support statistical 
modeling of instream nutrient load based on watershed attributes, 
southeastern United States, 2002: U.S. Geological Survey Open-File 
Report 2008-1163, 50 p.
---------------------------------------------------------------------------

    EPA further narrowed the range of possible protective loads by 
establishing the background load as a lower bound. EPA recognizes that 
a measure of natural background TN loading is the true lower limit, yet 
EPA recognizes also that some level of anthropogenic nutrient loading 
is acceptable, difficult to avoid, and unlikely to cause adverse 
biological responses. The current TN load minus the fraction of TN 
loading estimated to result from anthropogenic sources is used as an 
estimate of the background TN load. EPA used the SAGT-SPARROW regional 
watershed model to estimate background loading. SAGT-SPARROW 
empirically associates 100% of the measured nutrient loading into one 
of five classes (fertilizer, manure, urban, point sources, and 
atmospheric). EPA recognizes that some watershed models define more 
types of sources, according to their modeling objectives; however, it 
is important to recognize that these are

[[Page 4201]]

source classes, not sources, and that 100% of the measured loading is 
accounted for explicitly or implicitly by SPARROW in terms of these 
source classes.
    The class termed ``atmospheric'' reflects all loading that cannot 
be empirically attributed to causal variables associated with the other 
classes. EPA used the estimate for this class of loading as the 
background TN load. EPA recognizes that the SPARROW-estimated 
``atmospheric'' load includes anthropogenic contributions associated 
with regional-scale nitrogen emissions and does not represent pre-
industrial or true ``natural'' background loading. The ``atmospheric'' 
source term from SPARROW is also not equal to atmospheric nitrogen 
deposition as measured by the National Atmospheric Deposition Program 
(NADP). To properly interpret the TN load attributed to the 
``atmospheric'' source term in SPARROW, it is useful to recognize that 
SPARROW is a nonlinear regression model that seeks to explain measured 
TN loads in streams and rivers in terms of a series of explanatory 
variables. The atmospheric term is in all cases less, and often much 
less, than the measured deposition because not all the nitrogen 
deposited to the landscape is transported to streams, and not all of 
the nitrogen transported in streams reaches estuaries. The atmospheric 
source term from SPARROW excludes all the loading associated with both 
local anthropogenic nitrogen sources and factors contributing to 
increased transport of nitrogen from all sources (e.g., impervious 
surfaces). Therefore, EPA expects that reasonable values for the 
protective TN load are not likely to be less than these values.
    The protective TN load should be less than the current load and 
greater than the background load. Although this recognition may appear 
to be trivial, it is important. EPA estimates that TN loads to 
estuaries across Florida vary approximately 25-fold (~2 to 50 grams of 
nitrogen per square meter of estuary area). However, the ratio of the 
current load to the background load varies only between 1.7 and 5; for 
most estuaries, the range is between 2 and 4. Alternatively stated, 
current TN loads, which include local anthropogenic nitrogen sources, 
are two to four-fold higher than the background loads which do not 
include those sources. Thus, for any specific estuary, there is a 
relatively narrow range between the upper and lower bounds of potential 
protective loads.
    EPA acknowledges that not all the TN entering estuaries comes 
directly from the streams within its watershed. In some estuaries, 
direct atmospheric nitrogen deposition to the estuary surface may be an 
important source of TN loading to the estuary. Similarly, point sources 
such as industrial or wastewater treatment plant discharges directly to 
the estuary can be significant. In general, these sources are most 
significant when the ratio of watershed area to estuary area is 
relatively small compared to other estuaries (e.g., St. Andrew Bay, 
Sarasota Bay). In a few cases in Florida, point source loads directly 
to the estuary account for a large fraction of the aggregate load from 
all sources.
    As a second step, EPA sought to further reduce the range of 
possible protective loading values by considering additional evidence. 
One line of evidence EPA considered is previous estimates of protective 
loads. These have been developed as part of TMDLs for Florida estuaries 
or as part of Florida's Pollutant Load Reduction Goal or PLRG program. 
The scientific approaches utilized for TMDLs and PLRGs vary from simple 
to sophisticated and have recommended TN loading reductions between 3% 
and 63%, with a median of 38%. Higher reductions are typically 
associated with portions of estuaries currently receiving higher 
anthropogenic loading. Unfortunately, these analyses have not been 
completed for all of Florida's estuaries. Steward and Lowe (2009) \82\ 
showed that the TN loading limits suggested by TMDLs and PLRGs for a 
variety of aquatic ecosystems in Florida, including estuaries, could be 
statistically related to water residence time for the receiving water. 
EPA evaluated these relationships as an additional line of evidence for 
estimating protective TN loads for estuaries. EPA found these 
relationships to confirm in most cases, but not all, that the loading 
limits were likely between the bounds EPA previously established using 
SPARROW. However, the limits of uncertainty associated with the 
relationship were nearly as large as those already established. 
Nonetheless, the models provide additional support for EPA's estimates 
of protective estuary loads, but no further refinement of the 
estimates.
---------------------------------------------------------------------------

    \82\ Steward, J.S. and E.F. Lowe. 2010. General empirical models 
for estimating nutrient load limits for Florida's estuaries and 
inland waters. Limnology and Oceanography 55(1):433-445.
---------------------------------------------------------------------------

    Another approach to considering existing TMDLs and PLRGs is to 
consider directly the loading rate reductions recommended from those 
efforts, the median of which is 38% in Florida. This percent TN 
reduction is similar to the scientific consensus for several well-
studied coastal systems elsewhere (e.g., Chesapeake Bay, northern Gulf 
of Mexico) which have been subjected to increased TN loads from known 
anthropogenic sources. EPA recognizes that the magnitude of 
anthropogenic TN loads varies across Florida estuaries and that 
applying a uniform percent reduction across all estuaries does not 
account for the variable extent of anthropogenic loads and could lead 
to estimates below background load. An alternative approach is to 
assume that the appropriate loading reduction is proportional to the 
magnitude of anthropogenic enrichment. Thus, EPA suggests that 
protective TN loading may be estimated by assuming that the 
anthropogenic component of TN loading should be reduced by a constant 
fraction.
    As a result, EPA computed the protective TN load by reducing the 
current TN load by one half of the anthropogenic contribution to that 
load. EPA's protective load estimates are on average 25% less than 
current TN loading (range = 5 to 40%), consistent with most TMDLs and 
PLRGs for Florida estuaries.
    EPA developed protective TN loads for 16 estuarine water bodies in 
Florida for the purpose of computing DPVs for streams that are 
protective of uses in the estuarine receiving waters. EPA did not 
develop loading targets for the seven estuarine water bodies in south 
Florida (Caloosahatchee, St. Lucie, Biscayne Bay, Florida Bay, North 
and South Ten Thousand Islands, and Rookery Bay), because requisite 
information related to TN loading from the highly managed canals and 
waterways cannot be derived from SAGT-SPARROW and were not available 
otherwise, and three in central Florida (coastal drainage areas of the 
Withlacoochee River, Crystal-Pithlachascotee River and Daytona-St. 
Augustine) because EPA is still evaluating appropriate protective loads 
and the flows necessary to derive DPVs.
    EPA notes that some stakeholders, including FDEP staff,\83\ have 
raised

[[Page 4202]]

concerns about the suitability of the SAGT SPARROW to address 
downstream protection of estuaries and have suggested alternative 
models and approaches that have been applied for several of Florida's 
larger estuaries and their watersheds. These concerns include known 
limitations of the SPARROW model, particularly related to inadequate 
resolution of complex hydrology in several parts of the State. EPA also 
recognizes this limitation and as a result, has not used SAGT SPARROW 
to propose protective loads and associated downstream protection values 
for ten estuaries and their watersheds in Florida. EPA acknowledges 
that other approaches and models may also provide defensible estimates 
of protective loads.
---------------------------------------------------------------------------

    \83\ For further information on concerns raised by FDEP 
regarding the use of SPARROW, refer to ``Florida Department of 
Environmental Protection Review of SPARROW: How useful is it for the 
purposes of supporting water quality standards development?,'' 
``Assessment of FDEP Panhandle Stream proposed benchmark numeric 
nutrient criteria for downstream protection of Apalachicola Bay,'' 
and ``Analysis of Proposed Freshwater Stream Criteria's Relationship 
to Protective Levels in the Lower St. Johns River Based on the Lower 
St. Johns River Nutrient TMDL.'' located in EPA's docket ID No. EPA-
HQ-OW-2009-0596.
---------------------------------------------------------------------------

    Among the technical concerns that stakeholders including FDEP staff 
have raised are that: (1) SPARROW is useful for general pattern, but 
the large scale calibration lead to large errors for specific areas, 
(2) SPARROW only utilizes four source inputs, and (3) SPARROW was 
calibrated to only one year's worth of data. As presented in the above 
sections, but to briefly reiterate here: (1) SPARROW is calibrated 
across a larger area, but it utilizes a large amount of Florida site-
specific data and it explains 96% of the variation in observed loads 
from monitoring sites, (2) SPARROW accounts for all sources, but groups 
them into four general categories, and (3) SPARROW uses available data 
from the 1975-2004 period at monitored sites. This last concern may be 
confused with the technical procedure of presenting loading estimates 
as ``detrended to 2002''. This procedure accounts for long-term, inter-
annual variability to ensure that long-term conditions and trends are 
represented. The year 2002 was selected as a baseline because it has 
the best available land use/land cover information available, but the 
loading estimates, in fact, represent a long-term condition 
representative of many years of record. EPA encourages technical 
reviewers to consult with the technical references cited in this 
section for the complete explanations of technical procedures.
    EPA requests comment on its use of the SPARROW model to derive 
protective loads for downstream estuaries, as well as data and analyses 
that would support alternate methods of deriving downstream loads, or 
alternate methods of ensuring protection of designated uses in 
estuaries. For estuaries where sophisticated scientific analyses have 
been completed, relying on ample site-specific data to derive 
protective loads in the context of TMDLs, EPA encourages FDEP to submit 
resulting alternative DPVs under the SSAC process.
(iii) Computing Downstream Protection Values (DPVs)
    Once an estimate of protective TN loads is derived, EPA developed a 
methodology for computing DPVs, for streams that, if achieved, are 
expected to result in an average TN loading rate that does not exceed 
the protective load. EPA's methodology, which is used as the narrative 
translator, allows for the fraction of the protective TN loading 
contributed from each tributary within the watershed of an estuary to 
be determined by the fraction of the total freshwater flow contributed 
by that tributary. The DPV is specified as an average TN concentration, 
which is computed by dividing the protective TN load by the aggregate 
average freshwater inflow from the watershed. This approach results in 
the same DPV for each stream or river reach that terminates into a 
given estuary.
    EPA's methodology accounts for instream losses of TN. EPA 
recognizes that not all the TN transported within a stream network will 
ultimately reach estuaries. Rather, some TN is permanently lost from 
streams. This is not the same as reversible transformations of TN, such 
as algal uptake. Losses of TN are primarily associated with 
bacterially-mediated processes in stream sediments that convert 
biologically available nitrogen into inert N<INF>2</INF> gas, which 
enters the atmosphere (a process called denitrification). This occurs 
more rapidly in shallow streams and at almost negligible rates in 
deeper streams and rivers. EPA refers to the fraction of nitrogen 
transported in streams that ultimately reaches estuaries as the 
``fraction delivered.'' Estimates of the fraction delivered in Florida 
are less than 50% in streams very distant from the coast, but is 
between 80 and 100% in approximately half the stream reaches in 
Florida's estuarine watersheds.
    EPA's approach relies on estimating the fraction of TN delivered to 
downstream estuaries. Measuring instream loss rates at the appropriate 
time and space scale is exceedingly difficult, and it is not possible 
to do State-wide. EPA is not aware of other models or data suitable to 
estimating nitrogen losses in streams across the State of Florida. EPA 
obtained estimates from the SAGT-SPARROW model,\84\ which is possibly 
the best generally applicable approach to obtaining these estimates. 
One reason is that SPARROW estimates watershed-scale instream losses at 
the annual time scales across the entire region. Estimates of instream 
losses are modeled in SPARROW using a first-order decay rate as a 
function of time-of-travel in the reach. The inverse exponential 
relationship is consistent with scientific understanding that nitrogen 
losses decrease with increasing stream size and with results from 
experimental reach-scale studies using a variety of methods.\85\ EPA 
recognizes that stream attributes other than reach time-of-travel or 
size may influence instream loss rates and though the SPARROW model did 
not include these, the lack of spatial bias in model residuals suggests 
that inclusion of other potential subregional-scale or State-wide 
stream attributes may not improve modeled instream loss estimates.
---------------------------------------------------------------------------

    \84\ Hoos, A.B., and G. McMahon. 2009. Spatial analysis of 
instream nitrogen loads and factors controlling nitrogen delivery to 
streams in the southeastern United States using spatially referenced 
regression on watershed attributes (SPARROW) and regional 
classification frameworks. Hydrological Processes. DOI: 10.1002/
hyp.7323.
    \85\ Bohlke, J.K., R.C. Antweiler, J.W. Harvey, A.E. Laursen, 
L.K. Smith, R.L. Smith, and M.A. Voytek. 2009. Multi-scale 
measurements and modeling of Denitrification in streams with varying 
flow and nitrate concentration in the upper Mississippi River basin, 
USA. Biogeochemistry 93: 117-141. DOI 10.1007/s10533-008-9282-8.
---------------------------------------------------------------------------

    EPA developed and applied this methodology to compute DPVs for 
every stream reach in each of 16 estuarine watersheds starting with 
estuarine-specific estimates of the protective load. These estuarine 
watersheds align with the Nutrient Watershed Regions (NWR) used to 
derive instream protection values (IPVs). It is important to note that 
the scale at which protective loads and DPVs were derived is smaller 
than for IPVs (i.e., 16 estuarine watersheds vs. 4 nutrient watershed 
regions). EPA's recognition that some fraction of nitrogen transported 
in streams is retained or assimilated before reaching estuarine waters 
help ensure that the DPVs are not overprotective of downstream use in 
any particular estuary.
    In determining TN DPVs, EPA considered the contribution of TN 
inputs from wastewater discharged in shoreline catchments directly to 
the estuary. EPA found these point source inputs to be significant (> 
5% of total loading) in three (St. Andrew's Bay, St. Marys, St. John's) 
of the 16 estuaries. However, for the purpose of computing stream reach 
DPVs for a given estuarine watershed, EPA considered only those TN 
loads delivered from the estuarine watershed stream network and did not

[[Page 4203]]

include TN inputs from wastewater discharged in shoreline catchments 
directly to an estuary because these loads do not originate from 
upstream sources. However, point sources loads directly to the estuary 
would need to be considered in developing TMDLs based on estuary-
specific criteria.
    EPA's computation of DPVs using estimates of protective loading for 
each estuary and the fraction-delivered to estuaries is shown by 
equation (1):
[GRAPHIC] [TIFF OMITTED] TP26JA10.002

where the terms are defined as follows for a specific or (ith) 
stream reach:

Ci maximum flow-averaged nutrient concentration for a specific (the 
ith) stream reach consistent with downstream use protection (i.e., 
the DPV)
k fraction of all loading to the estuary that comes from the stream 
network resolved by SPARROW
Lest protective loading rate for the estuary, from all sources
QW combined average freshwater discharged into the estuary from the 
portion of the watershed resolved by the SPARROW stream network
Fi fraction of the flux at the downstream node of the specific (ith) 
reach that is transported through the stream network and ultimately 
delivered to estuarine receiving waters (i.e., Fraction Delivered).

    Note that the quantity kLest is equal to the loading to the estuary 
from sources resolved by SPARROW. For the purposes of practical 
implementation, EPA classified each stream water body (i.e., Water Body 
Identification or ``WBID'' using the FDEP term) according to the 
estuarine receiving water and one of six categories based on the 
fraction of TN delivered (0 to 50%, 51-60%, 61-70%, 71-80%, 81-90%, and 
91-100%). For each category, the upper end of the range was utilized to 
compute the applicable DPV for streams in the category, resulting in a 
value that will be protective. This approach reduces the number of 
unique DPVs from thousands to less than 100. Because the stream network 
utilized by the SAGT-SPARROW watershed model (ERF1) does not recognize 
all of the smaller streams in Florida (i.e., it is on a larger scale), 
EPA mapped WBIDs to the applicable watershed-scale unit, or 
``incremental watersheds,'' of the ERF1 reaches, assigning to each WBID 
the fraction of TN delivered estimated for the ERF1 reach whose 
incremental watershed includes the WBID. Where the WBID includes 
portions of the incremental watersheds of more than one ERF1 reach, EPA 
computed a weighted-average based on the proportion of WBID area in the 
watershed of each ERF1 reach.
    Given an even distribution of reaches within each 10% interval, 
EPA's ``binning'' approach to the fraction-delivered estimates results 
in a 5% to 10% margin of safety for the average reach in each range 
(closer to 10% for the lower fraction-delivered ranges). Potentially 
larger margins are possible within the 0 to 50% range, where the 
fraction delivered might be 20%, but the DPV would be computed assuming 
a fraction delivered of 50%. However, only one watershed in Florida for 
which EPA is proposing DPVs, the St. Johns River, has a substantial 
number of reaches estimated to have less than 50% TN delivered to 
estuarine waters. The SAGT-SPARROW watershed model estimates that 17% 
of the stream reaches in the St. Johns watershed are in this category, 
with about half the reaches delivering nearly 50% of TN and a 
substantial number delivering only 20% of TN. Given EPA's DPV for 
terminal reaches in the St. Johns watershed, however, the DPV for 
reaches with a fraction delivered less than 50% will be higher than the 
IPV, and therefore, will not apply. EPA requests comment on the binning 
approach for calculating DPVs, which allows for a relatively simple 
table of DPVs to be presented as compared to using the actual estimate 
of fraction TN delivered to calculate a DPV unique to each WBID using 
formula (1), above.
    At this time, EPA has not calculated protective TP loads for 
Florida's estuaries or DPVs for TP. However, advances in the 
application of regional watershed models, such as SPARROW, that address 
the sources and terrestrial and aquatic processes that influence the 
supply and transport of TP in the watershed and delivery to estuaries 
are currently in advanced stages of development.\86\ EPA anticipates 
obtaining the necessary data and information to compute TP loads for 
the estuarine water bodies in Florida in 2010 and could make this 
additional information available by issuing a supplemental Federal 
Register Notice of Data Availability (NODA), which would also be posted 
in the public docket for this proposed rule. EPA intends to derive 
proposed protective loads and DPVs for TP using an analogous approach 
as used for TN DPVs. EPA expects the approach will recognize that TP, 
like TN, is essential for estuarine processes but in excess will 
adversely impact aquatic life uses.
---------------------------------------------------------------------------

    \86\ Hoos, A.B., S. Terziotti, G. McMahon, K. Savvas, K.C. 
Tighe, and R. Alkons-Wolinsky. 2008. Data to support statistical 
modeling of instream nutrient load based on watershed attributes, 
southeastern United States, 2002: U.S. Geological Survey Open-File 
Report 2008--1163, 50 p.
---------------------------------------------------------------------------

(iv) EPA Downstream Protection Values (DPVs)
    The following criteria tables and corresponding DPVs for a given 
stream reach category have been geo-referenced to specific WBIDs which 
are managed by FDEP as the principal assessment unit for Florida's 
surface waters. To see where the criteria are geographically 
applicable, refer to EPA's TSD for Florida's Inland Waters, Appendix B-
18: In-Stream and Downstream Protection Value (IPV/DPV) Tables with DPV 
Geo-Reference Table to Florida WBIDs.

----------------------------------------------------------------------------------------------------------------
                                                          (mg L-1)                         TP (mg L-1)
    River/stream reach category--percent     -------------------------------------------------------------------
          delivered to estuary \4\               TN IPV \5\       TN DPV \6\       TP IPV \7\       TP DPV \8\
----------------------------------------------------------------------------------------------------------------
                                Perdido Bay Watershed \PH\ (EDA Code: \1\ G140x)
                            Protective TN Load for the Estuary: \2\: 847,520 kg y-\1\
                                   Protective TP Load for the Estuary: \3\ TBD
----------------------------------------------------------------------------------------------------------------
Less than 50%...............................              NR               NR            0.043              TBD
50.1-60.0%..................................              NR               NR            0.043              TBD
60.1-70.0%..................................              NR               NR            0.043              TBD
70.1-80.0%..................................              NR               NR            0.043              TBD
80.1-90.0%..................................           0.824             0.34            0.043              TBD
90.1-100%...................................           0.824             0.30            0.043              TBD
----------------------------------------------------------------------------------------------------------------

[[Page 4204]]

 
                               Pensacola Bay Watershed \PH\ (EDA Code: \1\ G130x)
                           Protective TN Load for the Estuary: \2\ 4,388,478 kg y-\1\
                                   Protective TP Load for the Estuary: \3\ TBD
----------------------------------------------------------------------------------------------------------------
Less than 50%...............................              NR               NR            0.043              TBD
50.1-60.0%..................................              NR               NR            0.043              TBD
60.1-70.0%..................................              NR               NR            0.043              TBD
70.1-80.0%..................................              NR               NR            0.043              TBD
80.1-90.0%..................................           0.824             0.48            0.043              TBD
90.1-100%...................................           0.824             0.43            0.043              TBD
----------------------------------------------------------------------------------------------------------------
                             Choctawhatchee Bay Watershed \PH\ (EDA Code: \1\ G120x)
                           Protective TN Load for the Estuary: \2\ 2,875,861 kg y-\1\
                                   Protective TP Load for the Estuary: \3\ TBD
----------------------------------------------------------------------------------------------------------------
Less than 50%...............................              NR               NR            0.043              TBD
50.1-60.0%..................................              NR               NR            0.043              TBD
60.1-70.0%..................................              NR               NR            0.043              TBD
70.1-80.0%..................................           0.824             0.48            0.043              TBD
80.1-90.0%..................................           0.824             0.43            0.043              TBD
90.1-100%...................................           0.824             0.39            0.043              TBD
----------------------------------------------------------------------------------------------------------------
                               St. Andrew Bay Watershed \PH\ (EDA Code: \1\ G110x)
                            Protective TN Load for the Estuary: \2\ 310,322 kg y-\1\
                                  Protective TP Load for the Estuary: \3\ TBDK
----------------------------------------------------------------------------------------------------------------
Less than 50%...............................           0.824             0.48            0.043              TBD
50.1-60.0%..................................              NR               NR            0.043              TBD
60.1-70.0%..................................              NR               NR            0.043              TBD
70.1-80.0%..................................           0.824             0.30            0.043              TBD
80.1-90.0%..................................           0.824             0.27            0.043              TBD
90.1-100%...................................           0.824             0.24            0.043              TBD
----------------------------------------------------------------------------------------------------------------
                              Apalachicola Bay Watershed \PH\ (EDA Code: \1\ G100x)
                           Protective TN Load for the Estuary: \2\ 10,971,582 kg y-\1\
                                   Protective TP Load for the Estuary: \3\ TBD
----------------------------------------------------------------------------------------------------------------
Less than 50%...............................           0.824             0.91            0.043              TBD
50.1-60.0%..................................              NR               NR            0.043              TBD
60.1-70.0%..................................           0.824             0.65            0.043              TBD
70.1-80.0%..................................           0.824             0.57            0.043              TBD
80.1-90.0%..................................           0.824             0.51            0.043              TBD
90.1-100%...................................           0.824             0.46            0.043              TBD
----------------------------------------------------------------------------------------------------------------
                               Apalachee Bay Watershed \PH\ (EDA Code: \1\ G090x)
                           Protective TN Load for the Estuary: \2\ 2,539,883 kg y-\1\
                                   Protective TP Load for the Estuary: \3\ TBD
----------------------------------------------------------------------------------------------------------------
Less than 50%...............................              NR               NR            0.043              TBD
50.1-60.0%..................................              NR               NR            0.043              TBD
60.1-70.0%..................................              NR               NR            0.043              TBD
70.1-80.0%..................................           0.824             0.67            0.043              TBD
80.1-90.0%..................................           0.824             0.59            0.043              TBD
90.1-100%...................................           0.824             0.53            0.043              TBD
----------------------------------------------------------------------------------------------------------------
                     Econfina/Steinhatchee Coastal Drainage Area \PH\ (CDA Code: \1\ G086x)
                            Protective TN Load for the Estuary: \2\ 185,301 kg y-\1\
                                   Protective TP Load for the Estuary: \3\ TBD
----------------------------------------------------------------------------------------------------------------
Less than 50%...............................              NR               NR            0.043              TBD
50.1-60.0%..................................              NR               NR            0.043              TBD
60.1-70.0%..................................              NR               NR            0.043              TBD
70.1-80.0%..................................              NR               NR            0.043              TBD
80.1-90.0%..................................           0.824             0.41            0.043              TBD
90.1-100%...................................           0.824             0.37            0.043              TBD
----------------------------------------------------------------------------------------------------------------
                                Suwannee River Watershed\NC\ (EDA Code: \1\G080x)
                           Protective TN Load for the Estuary: \2\ 5,421,050 kg y-\1\
                                   Protective TP Load for the Estuary: \3\ TBD
----------------------------------------------------------------------------------------------------------------
Less than 50%...............................              NR               NR            0.359              TBD
50.1-60.0%..................................              NR               NR            0.359              TBD
60.1-70.0%..................................           1.479             0.78            0.359              TBD

[[Page 4205]]

 
70.1-80.0%..................................           1.479             0.69            0.359              TBD
80.1-90.0%..................................           1.479             0.61            0.359              TBD
90.1-100%...................................           1.479             0.55            0.359              TBD
----------------------------------------------------------------------------------------------------------------
                           Waccasassa Coastal Drainage Area \PN\ (CDA Code: \1\ 078x)
                            Protective TN Load for the Estuary: \2\ 433,756 kg y-\1\
                                   Protective TP Load for the Estuary: \3\ TBD
----------------------------------------------------------------------------------------------------------------
Less than 50%...............................              NR               NR            0.107              TBD
50.1-60.0%..................................              NR               NR            0.107              TBD
60.1-70.0%..................................              NR               NR            0.107              TBD
70.1-80.0%..................................              NR               NR            0.107              TBD
80.1-90.0%..................................           1.205             0.45            0.107              TBD
90.1-100%...................................           1.205             0.40            0.107              TBD
----------------------------------------------------------------------------------------------------------------
                         Withlacoochee Coastal Drainage Area \PN\ (CDA Code: \1\ G076x)
                                   Protective TN Load for the Estuary: \2\ TBD
                                   Protective TP Load for the Estuary: \3\ TBD
----------------------------------------------------------------------------------------------------------------
Less than 50%...............................           1.205              TBD            0.107              TBD
50.1-60.0%..................................           1.205              TBD            0.107              TBD
60.1-70.0%..................................           1.205              TBD            0.107              TBD
70.1-80.0%..................................           1.205              TBD            0.107              TBD
80.1-90.0%..................................           1.205              TBD            0.107              TBD
90.1-100%...................................           1.205              TBD            0.107              TBD
----------------------------------------------------------------------------------------------------------------
                    Crystal/Pithlachascotee Coastal Drainage Area \PN\ (CDA Code: \1\ G074x)
                                   Protective TN Load for the Estuary: \2\ TBD
                                   Protective TP Load for the Estuary: \3\ TBD
----------------------------------------------------------------------------------------------------------------
Less than 50%...............................           1.205              TBD            0.107              TBD
50.1-60.0%..................................              NR              TBD            0.107              TBD
60.1-70.0%..................................              NR              TBD            0.107              TBD
70.1-80.0%..................................              NR              TBD            0.107              TBD
80.1-90.0%..................................           1.205              TBD            0.107              TBD
90.1-100%...................................           1.205              TBD            0.107              TBD
----------------------------------------------------------------------------------------------------------------
                                 Tampa Bay Watershed \BV\ (EDA Code: \1\ G070x)
                           Protective TN Load for the Estuary: \2\ 1,289,671 kg y-\1\
                                   Protective TP Load for the Estuary: \3\ TBD
----------------------------------------------------------------------------------------------------------------
Less than 50%...............................           1.798             1.11            0.739              TBD
50.1-60.0%..................................           1.798             0.93            0.739              TBD
60.1-70.0%..................................           1.798             0.80            0.739              TBD
70.1-80.0%..................................           1.798             0.70            0.739              TBD
80.1-90.0%..................................           1.798             0.62            0.739              TBD
90.1-100%...................................           1.798             0.56            0.739              TBD
----------------------------------------------------------------------------------------------------------------
                                Sarasota Bay Watershed \BV\ (EDA Code: \1\ G060x)
                            Protective TN Load for the Estuary: \2\ 155,576 kg y-\1\
                                   Protective TP Load for the Estuary: \3\ TBD
----------------------------------------------------------------------------------------------------------------
Less than 50%...............................              NR               NR            0.739              TBD
50.1-60.0%..................................              NR               NR            0.739              TBD
60.1-70.0%..................................              NR               NR            0.739              TBD
70.1-80.0%..................................              NR               NR            0.739              TBD
80.1-90.0%..................................              NR               NR            0.739              TBD
90.1-100%...................................           1.798             0.54            0.739              TBD
----------------------------------------------------------------------------------------------------------------
                              Charlotte Harbor Watershed \BV\ (EDA Code: \1\ G050w)
                           Protective TN Load for the Estuary: \2\ 2,710,107 kg y-\1\
                                   Protective TP Load for the Estuary: \3\ TBD
----------------------------------------------------------------------------------------------------------------
Less than 50%...............................              NR               NR            0.739              TBD
50.1-60.0%..................................           1.798             1.58            0.739              TBD
60.1-70.0%..................................           1.798             1.35            0.739              TBD
70.1-80.0%..................................           1.798             1.18            0.739              TBD
80.1-90.0%..................................           1.798             1.05            0.739              TBD
90.1-100%...................................           1.798             0.95            0.739              TBD
----------------------------------------------------------------------------------------------------------------

[[Page 4206]]

 
                                Indian River Watershed \PN\ (EDA Code: \1\ S190x)
                            Protective TN Load for the Estuary: \2\ 463,724 kg y-\1\
                                   Protective TP Load for the Estuary: \3\ TBD
----------------------------------------------------------------------------------------------------------------
Less than 50%...............................              NR               NR            0.107              TBD
50.1-60.0%..................................              NR               NR            0.107              TBD
60.1-70.0%..................................              NR               NR            0.107              TBD
70.1-80.0%..................................           1.205             0.87            0.107              TBD
80.1-90.0%..................................           1.205             0.77            0.107              TBD
90.1-100%...................................           1.205             0.69            0.107              TBD
----------------------------------------------------------------------------------------------------------------
                            Caloosahatchee River Watershed PN,# (EDA Code: \1\ G050a)
                                   Protective TN Load for the Estuary: \2\ TBD
                                   Protective TP Load for the Estuary: \3\ TBD
----------------------------------------------------------------------------------------------------------------
Less than 50%...............................           1.205              TBD            0.107              TBD
50.1-60.0%..................................           1.205              TBD            0.107              TBD
60.1-70.0%..................................           1.205              TBD            0.107              TBD
70.1-80.0%..................................           1.205              TBD            0.107              TBD
80.1-90.0%..................................           1.205              TBD            0.107              TBD
90.1-100%...................................           1.205              TBD            0.107              TBD
----------------------------------------------------------------------------------------------------------------
                              St. Lucie River Watershed PN,# (EDA Code: \1\ S190x)
                                   Protective TN Load for the Estuary: \2\ TBD
                                   Protective TP Load for the Estuary: \3\ TBD
----------------------------------------------------------------------------------------------------------------
Less than 50%...............................           1.205              TBD            0.107              TBD
50.1-60.0%..................................           1.205              TBD            0.107              TBD
60.1-70.0%..................................           1.205              TBD            0.107              TBD
70.1-80.0%..................................           1.205              TBD            0.107              TBD
80.1-90.0%..................................           1.205              TBD            0.107              TBD
90.1-100%...................................           1.205              TBD            0.107              TBD
----------------------------------------------------------------------------------------------------------------
                                      Kissimmee River Watershed PN,[caret]
                                   Protective TN Load for the Estuary: \2\ TBD
                                   Protective TP Load for the Estuary: \3\ TBD
----------------------------------------------------------------------------------------------------------------
Less than 50%...............................           1.205          TBD \9\            0.107          TBD \9\
50.1-60.0%..................................           1.205          TBD \9\            0.107          TBD \9\
60.1-70.0%..................................           1.205          TBD \9\            0.107          TBD \9\
70.1-80.0%..................................           1.205          TBD \9\            0.107          TBD \9\
80.1-90.0%..................................           1.205          TBD \9\            0.107          TBD \9\
90.1-100%...................................           1.205          TBD \9\            0.107          TBD \9\
----------------------------------------------------------------------------------------------------------------
                             St. John's River Watershed; \PN\ (EDA Code: \1\ S180x)
                           Protective TN Load for the Estuary: \2\ 4,954,662 kg y-\1\
                                   Protective TP Load for the Estuary: \3\ TBD
----------------------------------------------------------------------------------------------------------------
Less than 50%...............................           1.205             1.41            0.107              TBD
50.1-60.0%..................................           1.205             1.17            0.107              TBD
60.1-70.0%..................................           1.205             1.00            0.107              TBD
70.1-80.0%..................................           1.205             0.88            0.107              TBD
80.1-90.0%..................................           1.205             0.78            0.107              TBD
90.1-100%...................................           1.205             0.70            0.107              TBD
----------------------------------------------------------------------------------------------------------------
                     Daytona/St. Augustine Coastal Drainage Area \PN\ (CDA Code: \1\ S183x)
                                   Protective TN Load for the Estuary: \2\ TBD
                                   Protective TP Load for the Estuary: \3\ TBD
----------------------------------------------------------------------------------------------------------------
Less than 50%...............................              NR              TBD            0.107              TBD
50.1-60.0%..................................              NR              TBD            0.107              TBD
60.1-70.0%..................................              NR              TBD            0.107              TBD
70.1-80.0%..................................              NR              TBD            0.107              TBD
80.1-90.0%..................................           1.205              TBD            0.107              TBD
90.1-100%...................................           1.205              TBD            0.107              TBD
----------------------------------------------------------------------------------------------------------------
                             Nassau Coastal Drainage Area \PN\ (CDA Code: \1\ S175x)
                            Protective TN Load for the Estuary: \2\ 131,389 kg y-\1\
                                   Protective TP Load for the Estuary: \3\ TBD
----------------------------------------------------------------------------------------------------------------
Less than 50%...............................           1.205             0.59            0.107              TBD
50.1-60.0%..................................              NR               NR            0.107              TBD
60.1-70.0%..................................              NR               NR            0.107              TBD

[[Page 4207]]

 
70.1-80.0%..................................              NR               NR            0.107              TBD
80.1-90.0%..................................           1.205             0.33            0.107              TBD
90.1-100%...................................           1.205             0.30            0.107              TBD
----------------------------------------------------------------------------------------------------------------
                              St. Mary's River Watershed \PN\ (EDA Code: \1\ S170x)
                            Protective TN Load for the Estuary: \2\ 562,644 kg y-\1\
                                   Protective TP Load for the Estuary: \3\ TBD
----------------------------------------------------------------------------------------------------------------
Less than 50%...............................              NR               NR            0.107              TBD
50.1-60.0%..................................              NR               NR            0.107              TBD
60.1-70.0%..................................              NR               NR            0.107              TBD
70.1-80.0%..................................           1.205             0.43            0.107              TBD
80.1-90.0%..................................           1.205             0.38            0.107              TBD
90.1-100%...................................           1.205             0.34            0.107             TBD
----------------------------------------------------------------------------------------------------------------
Footnotes associated with this table:
\1\ Watershed delineated by NOAA's Coastal Assessment Framework and associated Florida Department of
  Environmental Protection's estuarine and coastal water body identifier (WBID).
\2\ Estimated TN load delivered to the estuary protective of aquatic life use. These estimates may be revised
  pursuant to the EPA final rule for numeric nutrient criteria for Florida's estuaries and coastal waters
  (October 2011).
\3\ Estimated TP load delivered to the estuary protective of aquatic life use. These estimates are currently
  under development. Preliminary estimates may be revised pursuant to the EPA final rule for numeric nutrient
  criteria for Florida's estuaries and coastal waters (October 2011).
\4\ River/Stream reach categories within each estuarine watershed are linked spatially to a specific FDEP water
  body identifier (WBID). See Appendix B-18 of the ``Technical Support Document for EPA's Proposed Rule for
  Numeric Nutrient Criteria for Florida's Inland Surface Fresh Waters.''
\5\ Instream Protection Value (IPV) is the TN concentration protective of instream aquatic life use.
\6\ Downstream protection values (DPVs) are estimated TN concentrations in the river/stream reach that meet the
  estimated TN load, protective of aquatic life use, delivered to the estuarine waters. These estimates may be
  revised pursuant to the EPA final rule for numeric nutrient criteria for Florida's estuaries and coastal
  waters (October 2011).
\7\ Instream Protection Value (IPV) is the TP concentration protective of instream aquatic life use.
\8\ Downstream protection values (DPVs) are estimated TP concentrations in the river/stream reach that meet the
  estimated TP load, protective of aquatic life use, delivered to the estuarine waters. These estimates are
  currently under development. Preliminary estimates may be revised pursuant to the EPA final rule for numeric
  nutrient criteria for Florida's estuaries and coastal waters (October 2011).
\9\ EPA's proposed TN and TP criteria for colored lakes (>40 PCU) are 1.2 and 0.050 mg L-\1\, respectively.
<greek-i> Estimated TN and TP loads protective of aquatic life in the Caloosahatchee and St. Lucie River
  estuaries, and in turn estimated TN and TP concentrations that would meet those protective loads, could not be
  calculated using EPA's downstream protection approach. An alternative downstream protection approach will be
  proposed in EPA's proposed rule for FL estuaries (January 2011).
[caret] Kissimmee River watershed does not have an EDA or CDA code because it does not drain directly to an
  estuary or coastal area, but rather indirectly through Lake Okeechobee and the south Florida canal system.
A protective TN and TP load for Lake Okeechobee has not been calculated, however, a TMDL is in effect for TP.
  EPA's proposed colored lake criteria (> 40 PCU) could be used to develop DPVs for TN and TP for the Kissimmee
  watershed (see footnote 9).
\LO\ DPVs to be based on protective TN and TP loads for Lake Okeechobee. EPA's proposed colored lake criteria
  (>40 PCU) could be used to develop DPVs for TN and TP for the Kissimmee watershed (see footnote 9).
\NR\ There are no stream reaches present in this watershed that have a percent-delivered within this range and
  thus criteria are not applicable.
\PH\ Panhandle Nutrient Watershed Region.
\BV\ Bone Valley Nutrient Watershed Region.
\PN\ Peninsula Nutrient Watershed Region.
\NC\ North Central Nutrient Watershed Region.
\TBD\ To be determined.

(v) Application of DPVs for Downstream Estuary Protection
    The following discussion further explains the conceptual 
relationship between IPVs and DPVs for stream criteria. EPA developed 
IPVs to protect the uses that occur within the stream itself at the 
point of application, such as protection of the benthic invertebrate 
community and maintenance of a healthy balance of phytoplankton 
species. In contrast, EPA developed DPVs for streams to protect WQS of 
downstream waters. EPA derived DPVs in Florida streams by distributing 
the protective load from the aggregate stream network identified for 
each downstream estuary (that is protective of estuarine conditions) 
across the watershed in proportion to the amount of flow contributed by 
each stream reach. EPA's approach also accounts for attenuation of 
nutrients (or loss from the system) as water travels from locations 
upstream in the watershed to locations near the mouth of the estuary.
    When comparing an IPV and DPV that are each deemed to apply to a 
particular stream segment, the more stringent of the two values is the 
numeric nutrient criterion that would need to be met when implementing 
CWA programs. Water bodies can differ significantly in their 
sensitivity to nutrients in general and to TN specifically. Although 
not universally true, freshwaters are generally phosphorus-limited and 
thus more sensitive to phosphorus enrichment because nitrogen is 
present in excess. Enriching freshwaters with phosphorus does not 
usually drive these systems into nitrogen limitation but can simply 
encourage growth of nitrogen-fixing algal species which can convert 
atmospheric nitrogen into ammonia. Conversely, estuaries are more often 
nitrogen limited and thus more sensitive to adverse impacts from 
nitrogen enrichment. As a result, it is not at all surprising that DPVs 
for TN in Florida are often less than the corresponding IPVs.
    Adjustments to DPVs are possible with a redistribution approach, 
which revises the original uniform assignment of protective downstream 
estuarine loadings across the estuarine drainage area using the DPV 
methodology, or by revising either the protective load delivered to the 
downstream estuary and/or the equivalent DPVs using a technical 
approach of comparable scientific rigor and the Federal SSAC procedure 
described in section V.C of this notice.

[[Page 4208]]

    Re-distributing the allocation of protective loading within an 
estuarine drainage area, or subset of an estuarine drainage area, is 
appropriate and protective because the total load delivered to the 
mouth of the estuary would still meet the protective load. DPVs may be 
a series of values for each reach in the upstream drainage area such 
that the sum of reach-specific incremental loading delivered to the 
estuary equals the protective loading rate taking into account that 
downstream reaches must reflect loads established for upstream reaches. 
Adjustments to DPVs may also factor in additional nutrient attenuation 
provided by already existing landscape modifications or treatment 
systems, such as constructed wetlands or stormwater treatment areas, 
where the attenuation is sufficiently documented and not a temporary 
condition. Unlike re-allocation of an even distribution of loading, 
these types of adjustments, as well as other site-specific information 
on alternative fractions delivered, would require use of the SSAC 
procedure under this proposal. EPA requests comment on whether these 
adjustments should be allowed to occur in the implementation of the re-
allocation process rather than as a SSAC.
    A technical approach of comparable scientific rigor will include a 
systematic data driven evaluation and accompanying analysis of relevant 
factors to identify a protective load delivered to the estuary. An 
acceptable alternate numeric approach also includes a method to 
distribute and apply the load to streams and other waters within the 
estuarine drainage area in a manner that recognizes conservation of 
mass and makes use of a peer-reviewed model (empirical or mechanistic) 
of comparable or greater rigor and scientific defensibility than the 
USGS SPARROW model. To use an alternative technical approach, the State 
must go through the process for a Federal SSAC procedure as described 
in Section V.C.
    EPA requests comment on the DPV approach, the technical merit of 
the estimated protective loadings, and the technical merit of the 
method for calculating stream reach values. EPA also requests comment 
on other scientifically defensible approaches for ensuring protection 
of designated uses in estuaries. At this time, EPA plans to take final 
action with respect to downstream protection values for nitrogen as 
part of the second phase of this rulemaking process in coordination 
with the proposal and finalization of numeric standards for estuarine 
and coastal waters in 2011. However, if comments, data and analyses 
submitted as a result of this proposal support finalizing these values 
sooner, by October 2010, EPA may choose to proceed in this manner. To 
facilitate this process, EPA requests comments and welcomes thorough 
evaluation on the technical and scientific basis of these proposed 
downstream protection values as part of the broader comment and 
evaluation process that this proposal initiates.

D. Proposed Numeric Nutrient Criteria for the State of Florida's 
Springs and Clear Streams

(1) Proposed Numeric Nutrient Criteria for Springs and Clear Streams
    Springs and their associated spring runs in Florida are a unique 
class of aquatic ecosystem, highly treasured for their biological, 
economic, aesthetic, and recreational value. Globally, the largest 
number of springs (per unit of area), occur in Florida; Florida has 
over 700 springs and associated spring runs. Many of the larger spring 
ecosystems in Florida have likely been in existence since the end of 
the last major ice age (approximately 15,000 to 30,000 years ago). The 
productivity of the diverse assemblage of aquatic flora and fauna in 
Florida springs is primarily determined by the naturally high amount of 
light availability of these waters (naturally high clarity).\87\ As 
recently as 50 years ago, these waters were considered by naturalists 
and scientists to be some of the most unique and exceptional waters in 
the State of Florida and the Nation as a whole.
---------------------------------------------------------------------------

    \87\ 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. http://www.dep.state.fl.us/springs/reports/files/UF_SpringsNutrients_Report.pdf, University of Florida, Gainesville, Florida.
---------------------------------------------------------------------------

    In Florida, springs are also highly valued as a water resource for 
human use: people use springs for a variety of recreational purposes 
and are interested in the intrinsic aesthetics of clear, cool water 
emanating vigorously from beneath the ground. A good example of the 
value of springs in Florida is the use of the spring boil areas that 
have sometimes been modified to encourage human recreation (bathing or 
swimming).\88\
---------------------------------------------------------------------------

    \88\ Scott, T.M., G.H. Means, R.P. Meegan, R.C. Means, S.B. 
Upchurch, R.E. Copeland, J. Jones, T. Roberts, and A. Willet. 2004. 
Springs of Florida. Bulletin No, 66. Florida Geological Survey. 
Tallahassee, FL. 677 pp.
---------------------------------------------------------------------------

    Over the past two decades, scientists have identified two 
significant anthropogenic factors linked to adverse changes in spring 
ecosystems that have the potential to permanently alter Florida's 
spring ecosystems. These are: (1) Pollution of groundwater,\89\ 
principally with nitrate-nitrite, resulting from human land use 
changes, cultural practices, and explosive population growth; and (2) 
simultaneous reductions in groundwater supply from human 
withdrawals.\90\ Pollution associated with human activities is one of 
the most critical issues affecting the health of Florida's springs.\91\
---------------------------------------------------------------------------

    \89\ 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. U.S. Geological Survey Water-
Resources Investigations Report 99-4252. Reston, VA.
    \90\ 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. http://www.dep.state.fl.us/springs/reports/files/UF_SpringsNutrients_Report.pdf, University of Florida, Gainesville, Florida.
    \91\ Ibid.
---------------------------------------------------------------------------

    Excess nutrients, in particular excess nitrogen, seep into the 
soils and move to groundwater.\92\ When in excess, nutrients lead to 
eutrophication of groundwater-fed springs, allowing algae and invasive 
plant species to displace native plants, which in turn results in an 
ecological imbalance.\93\ Excessive growth of nuisance algae and 
noxious plant species in turn result in reduced habitat and food 
sources for native wildlife,\94\ excess organic carbon production, 
accelerated decomposition, and lowered quality of the floor or 
``bottom'' of springs and spring runs, all of which adversely impact 
the overall health and aesthetics of Florida's springs.
---------------------------------------------------------------------------

    \92\ 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. U.S. Geological Survey Water-
Resources Investigations Report 99-4252. Reston, VA.
    \93\ Doyle, R.D. and R.M. Smart. 1998. Competitive reduction of 
noxious Lyngbya wollei mats by rooted aquatic plants. Aquatic Botany 
61:17-32.
    \94\ Stevenson, R.J., A. Pinowska, A. Albertin, and J.O. 
Sickman. 2007. Ecological condition of algae and nutrients in 
Florida springs: The Synthesis Report. Prepared for the Florida 
Department of Environmental Protection. Tallahassee, FL. 58 pp.
    Bonn, M.A. and F.W. Bell. 2003. Economic Impact of Selected 
Florida Springs on Surrounding Local Areas. Report prepared for the 
Florida Department of Environmental Protection. Tallahassee, FL.
---------------------------------------------------------------------------

    Adverse impacts on the overall health of Florida's springs have 
been evident over the past several decades. Within the last 20-30 
years, observations at

[[Page 4209]]

several of Florida's springs suggest that nuisance algae species have 
proliferated, and are now out-competing and replacing native submerged 
vegetation. Numerous biological studies have documented excessive algal 
growth at many major springs. In some of the more extreme examples, 
such as Silver Springs and Weeki Wachee Springs, algal mat 
accumulations have become over three feet thick.\95\\,\\96\
---------------------------------------------------------------------------

    \95\ Pinowska, A., R.J. Stevenson, J.O. Sickman, A. Albertin, 
and M. Anderson. 2007. 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.
    \96\ 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.
---------------------------------------------------------------------------

    As a result of human-induced land use changes, cultural practices, 
and explosive population growth, there has been an increase in the 
level of pollutants, especially nitrate, in groundwater over the past 
decades.\97\ Because there is no geologic source of nitrogen in 
springs, all of the nitrogen emerging in spring vents originates from 
that which is deposited on the land. Historically, nitrate 
concentrations in Florida's spring discharges were thought to have been 
around 0.05 mg/L or less, which is sufficiently low to restrict growth 
of algae and vegetation under ``natural'' conditions.\98\
---------------------------------------------------------------------------

    \97\ Scott, T.M., G.H. Means, R.P. Meegan, R.C. Means, S.B. 
Upchurch, R.E. Copeland, J. Jones, T. Roberts, and A. Willet. 2004. 
Springs of Florida. Bulletin No, 66. Florida Geological Survey. 
Tallahassee, FL. 677 pp.
    \98\ Maddox, G.L., J.M. Lloyd, T.M. Scott, S.B. Upchurch and R. 
Copeland. 1992. Florida's Groundwater Quality Monitoring Program--
Background Hydrochemistry. Florida Geological Survey Special 
Publication 34. Tallahassee, FL.
---------------------------------------------------------------------------

    Regions where springs emanate in Florida have experienced 
unprecedented population growth and changes in land use over the past 
several decades.\99\ With these changes in population and growth came a 
transfer of nutrients, particularly nitrate, to groundwater. Of 125 
spring vents sampled by the Florida Geological Survey in 2001-2002, 42% 
had nitrate concentrations exceeding 0.50 mg/L and 24% had 
concentrations greater than 1.0 mg/L.\100\ Similarly, a recent 
evaluation of water quality in 13 springs shows that mean nitrate-
nitrite levels have increased from 0.05 mg/L to 0.9 mg/L between 1970 
and 2002. Overall, data suggest that nitrate-nitrite concentrations in 
many spring discharges have increased from 10 to 350 fold over the past 
50 years, with the level of increase closely correlated with 
anthropogenic activity and land use changes within the karst regions of 
Florida where springs predominate.
---------------------------------------------------------------------------

    \99\ 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. U. S. Geological Survey Water-
Resources Investigations Report 99-4252. Reston, VA.
    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. http://www.dep.state.fl.us/springs/reports/files/UF_SpringsNutrients_Report.pdf, University of Florida, Gainesville, Florida.
    \100\ Scott, T.M., G.H. Means, R.P. Meegan, R.C. Means, S.B. 
Upchurch, R.E. Copeland, J. Jones, T. Roberts, and A. Willet. 2004. 
Springs of Florida. Bulletin No, 66. Florida Geological Survey. 
Tallahassee, FL. 677 pp.
---------------------------------------------------------------------------

    As nitrate-nitrite concentrations have increased during the past 20 
to 50 years, many Florida springs have undergone adverse environmental 
and biological changes. According to FDEP, there is a general consensus 
in the scientific community that nitrate is an important factor leading 
to the observed changes in spring ecosystems, and their associated 
biological communities. Nitrogen, particularly nitrate-nitrite, appears 
to be the most problematic nutrient problem in Florida's karst 
region.\101\
---------------------------------------------------------------------------

    \101\ 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. http://www.dep.state.fl.us/springs/reports/files/UF_SpringsNutrients_Report.pdf, University of Florida, Gainesville, Florida.
---------------------------------------------------------------------------

    Because nitrate-nitrite has been linked to many of the observed 
detrimental impacts in spring ecosystems, there is an immediate need to 
reduce nitrate-nitrite concentrations in spring vents and groundwater. 
A critical step in achieving reductions in nitrate-nitrite is to 
develop a numeric nitrate-nitrite criterion for spring systems that 
will be protective of these unique and treasured resources.\102\
---------------------------------------------------------------------------

    \102\ 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. http://www.dep.state.fl.us/springs/reports/files/UF_SpringsNutrients_Report.pdf, University of Florida, Gainesville, Florida.
---------------------------------------------------------------------------

    To protect springs and clear streams and to provide assessment 
levels and restoration goals for those that have already been impaired 
by nutrients, EPA is proposing numeric nutrient criteria for the 
following parameter for Florida's springs and clear streams (< 40 PCU) 
classified as Class I or III waters under Florida law (Rule 62-302.400, 
F.A.C.):

    Nitrate (NO<INF>3</INF>\-\)+Nitrite (NO<INF>2</INF>\-\) shall 
not surpass a concentration of 0.35 mg/L as an annual geometric mean 
more than once in a three-year period, nor surpassed as a long-term 
average of annual geometric mean values.

    In addition to the nitrate-nitrite criterion, TN and TP criteria 
developed for streams on a watershed basis are also applicable to clear 
streams. See Section III.C(1) ``Proposed Numeric Nutrient Criteria for 
the State of Florida's Rivers and Streams'' for the table of proposed 
TN and TP criteria that would apply to clear streams located within 
specific watersheds.
(2) Methodology for Deriving EPA's Proposed Criteria for Springs and 
Clear Streams
    EPA's proposed nitrate-nitrite criterion for springs and clear 
streams are derived from a combination of FDEP laboratory data, field 
surveys, and analyses which include analyses conducted to determine the 
stressor response-based thresholds that link nitrate-nitrite levels to 
biological risk in springs and clear streams. These data document the 
response of nuisance algae, Lyngbya wollei and Vaucheria sp., and 
periphyton to nitrate-nitrite concentrations. Please refer to EPA's TSD 
for Florida's Inland Waters, Chapter 3: Methodology for Deriving U.S. 
EPA's Proposed Criteria for Springs and Clear Streams.
    As described in Section III.C(2), the ability to establish 
protective criteria for both causal and response variables depends on 
available data and scientific approaches to evaluate these data. EPA 
has not undertaken the development of TP criteria for springs because 
phosphorus has historically been present in Florida's springs, given 
the State's naturally phosphorus-rich geology, and the lack of an 
increasing trend of phosphorus concentrations in most spring 
discharges. EPA is not proposing chlorophyll a and clarity criteria due 
to the lack of available data for these response variables in spring 
systems. Furthermore, scientific evidence examining the strong 
relationship between rapid periphyton survey data (measurements of the 
thickness of algal biomass attached to substrate rather than free-
floating) and nutrients in clear streams (those with color <40 PCU and 
canopy cover <= 40% which are comparable to most waters found in 
springs and spring runs) show that benthic algal thickness is highly 
dependent on nitrogen parameters (TN and total inorganic nitrogen), as 
opposed to phosphorus. In addition,

[[Page 4210]]

EPA is proposing to apply the nitrate-nitrite criteria derived for 
springs to clear streams as a measure to gauge anthropogenic 
contributions to TN. EPA is not currently proposing criteria for 
clarity and chlorophyll a for clear streams due to the lack of 
scientific evidence supporting the relationship between these response 
variables and nutrients. Clear streams show weak relationships between 
nutrients and chlorophyll a, as opposed to color streams where 
phytoplankton responses occur more readily than periphyton growth. 
Please refer to EPA's TSD for Florida's Inland Waters, Chapter 3: 
Methodology for Deriving U.S. EPA's Proposed Criteria for Springs and 
Clear Streams.
(a) Derivation of Proposed Nitrate-Nitrite Criteria
    EPA's goal in deriving nitrate-nitrite criteria for Florida springs 
and clear streams is to ensure that the criteria will preserve the 
ecosystem structure and function of Florida's springs and clear 
streams. EPA reviewed Florida data, FDEP's approach and analyses, and 
FDEP's proposed nitrate-nitrite criterion for springs and clear streams 
and has concluded that the FDEP approach and the values FDEP derived 
represent a scientifically sound basis for the derivation of these 
criteria. FDEP evaluated results from laboratory scale dosing studies, 
data from in-situ algal monitoring, real-world surveys of biological 
communities and nutrient levels in Florida springs, and data on 
nitrate-nitrite concentrations found in minimally-impacted reference 
locations.
    FDEP analyzed laboratory data\103\ that evaluated the growth 
response of nuisance algae to nitrate addition. FDEP's analysis showed 
that Lyngbya wollei and Vaucheria sp. reached 90% of their maximum 
growth at 0.230 mg/L and 0.261 mg/L nitrate-nitrite, respectively. FDEP 
also reviewed long-term field surveys that examined the response of 
nuisance algae, periphyton, and eutrophic indicator diatoms to nitrate-
nitrite concentration.\104\ The results showed a sharp increase in 
abundance and/or biomass of the nuisance algae, periphyton, and diatoms 
at 0.44 mg/L nitrate-nitrite.
---------------------------------------------------------------------------

    \103\ Stevenson, R.J., A. Pinowska, A. Albertin, and J.O. 
Sickman. 2007. Ecological condition of algae and nutrients in 
Florida springs: The Synthesis Report. Prepared for the Florida 
Department of Environmental Protection. Tallahassee, FL. 58 pp.
    Cowell, B.C. and C.J. Dawes. 2004. Growth and nitrate-nitrogen 
uptake by the cyanobacterium Lyngbya wollei. J. Aquatic Plant 
Management 42: 69-71.
    \104\ 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, Tallahassee, Florida.
---------------------------------------------------------------------------

    FDED also reviewed the field surveys used to develop TMDLs for 
Wekiva River and Rock Spring Run to evaluate the relationship between 
the observed excessive algal growth and imbalance in aquatic flora with 
measurements of nutrients in these particular systems. FDEP found that 
taxa indicative of eutrophic conditions increased significantly with 
increasing nitrate-nitrite concentrations above approximately 0.35 mg/
L.
    Based on its review of a combination of this laboratory and field 
data, FDEP concluded that significant alterations in community 
composition (eutrophic indicator diatoms), in combination with an 
increase in periphyton cell density and biomass, clearly demonstrate 
that a nitrate-nitrite level in the range between 0.23 mg/L (the 
laboratory threshold) and 0.44 mg/L (the field study derived value 
associated with the upper bound nitrate-nitrite concentration where 
substantial observed biological changes were apparent) is the amount of 
nitrate-nitrite associated with an imbalance of aquatic flora in spring 
systems.\105\
---------------------------------------------------------------------------

    \105\ Mattson, R.A., E.F. Lowe, C.L. Lippincott, D. Jian, and L. 
Battoe. 2006. Wekiva River and Rock Springs Run Pollutant Load 
Reduction Goals. St. Johns River Water Management District, Palatka, 
Florida.
---------------------------------------------------------------------------

    FDEP conducted further statistical analyses of the available data 
from the multiple lines of evidence, applied an appropriate safety 
factor to ensure that waters would not reach the nitrate-nitrite levels 
associated with ``substantial observed biological changes,'' and 
averaged the results to arrive at a final protective threshold value 
for nitrate-nitrite in springs and clear streams of 0.35 mg/L. Based on 
the discussion above and corresponding analysis in the TSD for 
Florida's Inland Waters, EPA has concluded that this value was derived 
in a scientifically sound manner, appropriately considering the 
available data, and appropriately interpreting the multiple lines of 
evidence. Accordingly, EPA is proposing 0.35 mg/L nitrate-nitrite as a 
protective criterion for aquatic life in Florida's springs and clear 
streams.
(b) Proposed Criteria: Duration and Frequency
    EPA is proposing a duration and frequency expression of an annual 
geometric mean not to be surpassed more than once in a three-year 
period to be consistent with the expressions of duration and frequency 
for other water body types (e.g., lakes, streams, canals) for TN and TP 
and for the same reasons EPA selected a three-year period for those 
waters. Second, EPA proposes that the long-term arithmetic average of 
annual geometric means not exceed the criterion-magnitude 
concentration. EPA anticipates that Florida will use its standard 
assessment periods as specified in Rule 62-303, F.A.C. (Impaired Waters 
Rule) to implement this second provision. EPA has determined that this 
frequency of excursions should not result in unacceptable effects on 
aquatic life as it will allow the springs and clear streams aquatic 
systems enough time to recover from an occasionally elevated year of 
nutrient loadings. The Agency requests comment on these proposed 
duration and frequency expressions of the springs and clear streams 
numeric nutrient criteria.
    EPA also considered as an alternative, expressing the criterion as 
a monthly median not to be surpassed more than 10% of the time. Stated 
another way, the median value over any given calendar month shall not 
be higher than the criterion-magnitude value in more than one out of 
every ten months. It is appropriate to express a monthly criterion as a 
median because the median is less susceptible to outliers than the 
geometric mean. This is particularly important when dealing with small 
sample sizes. This alternative is consistent with the expression that 
FDEP proposed in July 2009 for its State rule and the expression in the 
TSD for Florida's Inland Waters that EPA sent out for external 
scientific peer review in July 2009. The rationale for this alternative 
is that field data indicate that the response in springs is correlated 
to monthly exposure at the criterion-magnitude concentration value and 
a 10% frequency of excursions is a reasonable and fully protective 
allowance given small sample sizes in any given month (i.e., the 
anticipated amount of data that will be available for assessment 
purposes in the future). The clear streams nitrate-nitrite criterion 
was derived by FDEP based on multiple lines of evidence, with the 
primary lines of evidence being mesocosm dosing experiments and field 
studies. These two main studies were conducted by FDEP over very 
different time frames. One set of mesocosm studies was conducted by 
FDEP for periods just under one month (i.e., 21 to 28 days), while 
another, the algal biomass field survey, was conducted over an 18-year 
period and was analyzed using four to five year averaging periods.\106\ 
While lab

[[Page 4211]]

studies indicate that algal communities can respond to excess nitrate-
nitrite over a short period of time, the mesocosm and other dosing 
studies indicate that this response occurs on the order of a month, 
which might support a monthly expression of the criterion.\107\ 
However, there is no evidence to suggest that the responses observed 
within a month under controlled lab settings equate to impairment of 
the designated use in conditions experienced in State waters. Please 
refer to EPA's TSD for Florida's Inland Waters, Chapter 3: Methodology 
for Deriving U.S. EPA's Proposed Criteria for Springs and Clear 
Streams.
---------------------------------------------------------------------------

    \106\ Gao, X. 2008. Nutrient TMDLs for the Wekiva River (WBIDs 
2956, 2956A, 2956C) and Rock Springs Run (WBID 2967). Florida 
Department of Environmental Protection, Tallahassee, Florida.
    \107\ Stevenson, R.J., A. Pinowska, A. Albertin, and J.O. 
Sickman. 2007. Ecological condition of algae and nutrients in 
Florida springs: The Synthesis Report. Prepared for the Florida 
Department of Environmental Protection. Tallahassee, FL. 58 pp.
---------------------------------------------------------------------------

    The 10% excursion frequency would recognize that in most cases the 
monthly ``median'' would actually be based on a single sample, given 
that most springs are only sampled monthly at the most. A 10% excursion 
frequency may be considered a reasonable and fully protective allowance 
given small sample sizes in any given month, essentially requiring that 
the monthly median nitrate-nitrate concentrations thought to be fully 
supportive of relevant designated uses be met 90% of the time.
    EPA requests comment on these proposed criteria duration and 
frequency expressions, and the basis for their derivation. EPA notes 
that some scientists and resource managers have suggested that nutrient 
criteria duration and frequency expressions should be more restrictive 
to avoid seasonal or annual ``spikes'' from which the aquatic system 
cannot easily recover, whereas others have suggested that criteria 
expresssed as simply a long-term average of annual geometric means, 
consistent with data used in criteria derivation, would still be 
protective. EPA requests comment on alternative duration and frequency 
expressions that might be considered protective, including (1) a 
criterion-duration expressed as a monthly average or geometric mean, 
(2) a criterion-frequency expressed as meeting allowable magnitude and 
duration every year, (3) a criterion-frequency expressed as meeting 
allowable magnitude and duration in more than half the years of a given 
assessment period, and (4) a criterion-frequency expressed as meeting 
the allowable magnitude and duration as a long-term average only. EPA 
further requests comment on whether an expression of the criteria in 
terms of an arithmetic average of annual geometric mean values based on 
rolling three-year periods of time would also be protective of the 
designated use.
(3) Request for Comment and Data on Proposed Approach
    EPA believes the proposed nutrient criterion for springs and clear 
streams in this rule are protective of the designated aquatic life use 
of these waters in Florida. EPA is soliciting comment on the approach 
FDEP used and EPA adopted to derive nitrate-nitrite criterion for 
springs and clear streams, including the data and analyses underlying 
the proposed criterion. EPA is seeking additional, readily-available, 
pertinent data and information related to nutrient concentrations or 
nutrient responses in springs and clear streams in Florida. EPA is also 
soliciting views on other potential, scientifically sound approaches to 
deriving protective nitrate-nitrite criterion for springs and clear 
streams in Florida.
(4) Alternative Approaches: Nitrate-Nitrite Criterion for All Waters as 
an Independent Criterion
    EPA is soliciting comment on the environmental benefits associated 
with deriving a nitrate-nitrite criterion for all waters covered by 
this proposal (i.e., all streams, lakes, and canals), in addition to 
the other proposed nutrient criteria for those water bodies. Adoption 
of a nitrate-nitrite criterion for waters other than springs and clear 
streams could be useful from an assessment and management perspective. 
Florida could use nitrate-nitrite data to identify increasing trends 
that may indicate the need for more specific controls of certain 
nitrogen enrichment sources. In cases where waters are impaired for 
either TN, nitrate-nitrite, or both TN and nitrate-nitrite, FDEP could 
use the nitrate-nitrite data to potentially target discharges of 
anthropogenic origin given their relative source contribution to 
nitrogen enrichment.
    This alternative approach, which would involve EPA deriving 
nitrate-nitrite criteria for all waters or alternatively applying 0.35 
mg/L nitrate-nitrite to all waters, could provide additional protection 
for aquatic life designated uses. The alternative approach would also 
eliminate the need for FDEP to characterize streams as clear or not. 
Deriving and applying a nitrate-nitrite criterion to all waters would 
reduce the likelihood of excess loading of the specific anthropogenic 
components of TN to colored waters. However, these colored streams may 
be less likely to show an observed response to nitrate-nitrite due to 
the presence of tannins that block light penetration. Thus, the 
presence of color in streams may confound the relationship that 
produced the 0.35 mg/L nitrate-nitrite criterion.

E. Proposed Numeric Nutrient Criteria for South Florida Canals

(1) Proposed Numeric Nutrient Criteria for South Florida Canals
    There are thousands of miles of canals in Florida, particularly in 
the southeastern part of the State. Canals are artificial waterways 
that are either the result of modifications to existing rivers or 
streams, or waters that have been created for various purposes, 
including drainage and flood control (stormwater management), 
irrigation, navigation, and recreation. These canals also allow for the 
creation of many waterfront home sites in Florida. Ecosystems that 
existed in rivers and streams prior to their modification into canals 
are altered. These changes can affect fish and wildlife and plant 
growth, as further explained in the following paragraphs. Newly created 
canals may have a tendency to fill with aquatic plants. Canals in south 
Florida vary greatly in size and depth. They can be anywhere from a few 
feet wide and a few feet deep to hundreds of feet wide and as deep as 
30-35 feet.
    South Florida canals vary in their hydrology and behavior due to 
their size, function, and seasonality. Shallow canals with slow water 
flow have poor turnover of water and little flushing. Large canals also 
may have low flow and turnover during the dry season. In contrast, 
during the wet season these same large canals are flowing systems that 
quickly move large volumes of water, as they were designed to 
accomplish. Excess nutrients in canals in combination with poor water 
circulation and decreased levels of dissolved oxygen, can lead to 
accelerated eutrophication and adverse impacts on other forms of 
aquatic life such as fish and other aquatic animals. In these canals, 
the accumulation of decaying organic matter on the canal bottom can 
also adversely impact healthy aquatic ecosystems.
    South Florida canals are highly managed waterways. Some canals are 
prone to an over-abundance of aquatic plants. Without regular and 
frequent management, dense vegetation can clog the waterways making 
navigation difficult and slowing the movement of water through the 
canal system. This can interfere with flood control, boating, and 
fishing. Aquatic plants (like plants in the terrestrial environment) 
respond

[[Page 4212]]

and grow when fertilized with nutrients such as phosphorus and 
nitrogen, and thus nutrient runoff into canals is likely a significant 
contributor to both nuisance algal blooms and clogging of canal systems 
by aquatic plants.
    EPA is proposing numeric nutrient criteria for the following 
parameters and geographic classifications in south Florida, for canals 
classified as Class III waters under Florida law (Rule 62-302.400, 
F.A.C.). The proposed and alternative approaches described herein would 
not apply for TP in canals within the Everglades Protection Area (EvPA) 
since there is an existing TP criterion of 0.010 mg/L that currently 
applies to the marshes and adjacent canals within the EvPA (Rule 62-
302.540, F.A.C.).

----------------------------------------------------------------------------------------------------------------
                                                                                       Total
                                                                   Chlorophyll a    phosphorus    Total nitrogen
                                                                   ([micro]g/L)     (TP) (mg/L)     (TN) (mg/L)
                                                                        \a\           \a\ \b\           \a\
----------------------------------------------------------------------------------------------------------------
Canals..........................................................             4.0           0.042             1.6
----------------------------------------------------------------------------------------------------------------
\a\ Concentration values are based on annual geometric mean not to be surpassed more than once in a three-year
  period. In addition, the long-term average of annual geometric mean values shall not surpass the listed
  concentration values. (Duration = annual; Frequency = not to be surpassed more than once in a three-year
  period or as a long-term average).
\b\ Applies to all canals within the Florida Department of Environmental Protection's South Florida bioregion,
  with the exception of canals within the Everglades Protection Area (EvPA) where the TP criterion of 0.010 mg/L
  currently applies.

    The following sections detail the methodology EPA used to develop 
the proposed numeric nutrient criteria for canals in south Florida, and 
request comment on the proposed criteria and their derivation. In 
addition, EPA is providing details of two alternative options for 
deriving canal criteria values that EPA considered and is soliciting 
comments on these alternatives.
(2) Methodology for Deriving EPA's Proposed Criteria for South Florida 
Canals
    Based on the available information for canals, EPA determined that 
the most scientifically sound way to derive protective numeric nutrient 
criteria for south Florida's canals is to use a similar approach to 
what EPA used to derive numeric nutrient criteria for streams. That is, 
EPA chose a nutrient concentration distribution-based approach using 
data from only those canals that have been determined to support the 
applicable designated use. EPA used existing water quality assessments 
and identified canals that have been determined to be impaired for 
nutrients. Data for those canals were excluded from the larger data set 
in order to create a set of data representing canals attaining the 
designated use of aquatic life, according to FDEP's assessment 
decisions. For further information, please refer to EPA's TSD for 
Florida's Inland Waters, Chapter 4: Methodology for Deriving U.S. EPA's 
Proposed Criteria for Canals.
(a) Derivation of Proposed Numeric Nutrient Criteria for South Florida 
Canals
    EPA derived numeric nutrient criteria for south Florida canals for 
two causal variables, TN and TP, and one response variable, chlorophyll 
a. In contrast to EPA's proposed criteria for Florida's streams, EPA 
concluded that there was a sufficient scientific basis for a 
chlorophyll a criterion for south Florida canals. EPA considered 
chlorophyll a to be an appropriate indicator of nutrient impairment in 
canals on the basis of the observed seasonal flow regimes, particularly 
during the relatively drier winter months when flows are relatively 
lower and canal water residence time is relatively higher (as compared 
to wetter, summer months). Furthermore, EPA found evidence that canals 
are susceptible to impairment due to excessive chlorophyll a based on 
the number of canals on Florida's CWA section 303(d) list with 
chlorophyll a cited as the parameter of concern. EPA analyzed the range 
of chlorophyll a concentrations in canals and found that 12% of 
chlorophyll a concentration observations occurred at 10 [mu]g/L or 
higher and 5% of chlorophyll a concentration observations occurred at 
20 [mu]g/L or higher. As a point of reference, Florida has chlorophyll 
a thresholds of 20 as the numeric interpretations of its narrative 
nutrient criteria for streams and 11 [mu]g/L for estuaries/open coastal 
waters, respectively, in its Impaired Waters Rule (IWR) (Rules 62-
303.351 and 62-303.353, F.A.C.). Thus, EPA included chlorophyll a as a 
nutrient criterion to protect canal aquatic life designated uses from 
an unacceptable biological response to excess nutrients.
    EPA employed a statistical distribution approach for deriving 
numeric nutrient criteria for south Florida canals. Specifically, EPA 
computed statistical distributions and descriptive statistics (e.g., 
quartiles, mean, standard deviation) of TN, TP, and chlorophyll a 
concentrations from data derived at canal sites across south Florida 
that are not on the impaired waters list for Florida. EPA has 
determined that the criteria derived from a distribution of canal data 
from canals with no evidence of nutrient impairment are appropriate and 
protective of designated uses.
    As described in detail in Section III.C(2)(c), EPA concluded that 
the 75th percentiles of the respective TN, TP, and chlorophyll a 
distributions would yield values that would ensure that aquatic life 
designated uses would be protected in south Florida canals. A 
reasonable choice is one that lies just above the vast majority of the 
population. The 75th percentile represents such a point on the 
distribution of TN, TP, and chlorophyll a values.
(b) Other Data and Analyses Conducted and Considered by EPA in the 
Derivation of Proposed Numeric Nutrient Criteria for South Florida 
Canals
    EPA undertook extensive analyses and considered a variety of data 
and methods for deriving numeric nutrient criteria for Florida's 
canals. Although EPA derived the proposed values based on the approach 
outlined in the section above, EPA also factored into its decision-
making process the results of these other analyses as additional lines 
of evidence.
    One line of additional evidence is based on an evaluation of the 
stressor-response relationship between chlorophyll a levels in canals 
and TN and TP levels using a variety of statistical tools. A second 
line of evidence is based on a consideration of the distribution of 
chlorophyll a measurements, TN measurements, and TP measurements from 
all canals, impaired and not impaired. Nutrient concentrations at the 
lower end of these distributions were compared to the concentration 
that the stressor-response analysis determined to be associated with 
canals with no evidence of nutrient impairment. The third line of 
evidence is based on a consideration of the distribution of chlorophyll 
a, TN, and

[[Page 4213]]

TP values from only those canals considered to be minimally impacted by 
nutrient-related pollution. EPA considered each of these lines of 
evidence in deriving the numeric nutrient criteria for canals.
    Because soil or substrate type at the bottom of a canal can 
influence the nutrient cycling and relationships between the observed 
biological response and the TP and TN levels in canals, EPA used data 
on soil types in south Florida along with knowledge of the Everglades 
Agricultural Area (EAA) and the Everglades Protection Area (EvPA) to 
subdivide the canal areas for criteria derivation. Thus the first step 
in these other analyses was to group canals and canal data by soil 
type. The four groupings consist of histosol and entisol soils of the 
EAA; histosol and entisol soils of the EvPA; spodosol and alfisol soils 
and areas west of the EvPA and EAA (hereafter, West Coast); and 
spodosol, entisol and alfisol soils and areas east of the EvPA and EAA 
(hereafter East Coast).
    EPA then sorted canal data (provided by FDEP, Miami-Dade County, 
and the South Florida Water Management District) into the four canal 
groupings. EPA screened the data to ensure the exclusion of the 
following: (1) Sites without relevant data (e.g., nitrogen, phosphorus, 
chlorophyll a), (2) sites influenced by marine waters, (3) sites within 
Class IV canals or Lake Okeechobee, (4) data not originating within a 
canal, (5) data with questionable units, and (6) outlier data. Data 
were organized by canal regions and year. Each site occurring near the 
border of a region and/or WBID was visually inspected using geographic 
information system (GIS) tools to ensure the correct placement of those 
sites. Local experts were also consulted by EPA. EPA analyzed the 
resulting regionalized data using statistical distribution and 
regression analyses. EPA undertook its additional analyses using these 
canal (and data) groupings.
    EPA's analysis of the distribution of chlorophyll a values in each 
of the four groupings of canals (using data from impaired and 
unimpaired sites) indicated that the lower percentile (i.e., 25th 
percentile) ranged from 1.9 to 2.2 [micro]g/L for chlorophyll a in the 
EvPA, West Coast, and East Coast, and was 6.3 [micro]g/L for the EAA. 
EPA's analysis of the distribution of TN values in each of the four 
groupings of canals indicated that the lower percentile (i.e., 25th 
percentile) ranged from 0.8 to 1.4 mg/L for the EvPA, West Coast, and 
East Coast and was 2.1 mg/L for the EAA. EPA's analysis of the 
distribution of TP values in each of the four groupings of canals 
indicated that the lower percentile (i.e., 25th percentile) ranged from 
0.013 to 0.023 mg/L for the EvPA, West Coast, and East Coast and was 
0.048 mg/L for the EAA canals.
    In an effort to consider chlorophyll a, TN, and TP values in canals 
minimally impacted by nutrient pollution, EPA identified canal sites 
surrounded by the EvPA in the east and the Big Cypress National 
Preserve in the west and considered the distribution of chlorophyll a, 
TN and TP values for these sites. Although EPA acknowledges that these 
sites have not been thoroughly vetted for biological condition, EPA 
believes that because they are remote and surrounded by wetlands, that 
these canal sites represent sites with the lowest impact from human 
activities. The upper percentile values (i.e., the 75th percentile) 
from the distributions of chlorophyll a, TN and TP values for these 
lower impact sites are 3.4 [micro]g/L for chlorophyll a, 1.3 mg/L for 
TN and 0.018 mg/L for TP.
    When considering the results of these additional analyses and 
comparing these results to the outcome of EPA's analysis of TN, TP, and 
chlorophyll a concentrations from data derived at canal sites across 
south Florida that are not on the impaired waters list for Florida, it 
is clear that EPA's proposed criteria for canals are similar to those 
derived from alternative approaches and therefore, represent a 
reasonable integration of these multiple lines of evidence. For further 
information, please refer to EPA's TSD for Florida's Inland Waters, 
Chapter 4: Methodology for Deriving U.S. EPA's Proposed Criteria for 
Canals.
(c) Proposed Criteria: Duration and Frequency
    Aquatic life water quality criteria contain three components: 
magnitude, duration, and frequency. For the TN and TP numeric criteria 
for canals, the derivation of the criterion-magnitude values is 
described above and these values are provided in the table in Section 
III.E(1). The criterion-duration for this magnitude (or averaging 
period) is specified in footnote a of the canals criteria table as an 
annual geometric mean. EPA is proposing two expressions of allowable 
frequency, both of which are to be met. First, EPA proposes a no-more-
than-one-in-three-years excursion frequency for the annual geometric 
mean criteria for canals. Second, EPA proposes that the long-term 
arithmetic average of annual geometric means not exceed the criterion-
magnitude concentration. EPA anticipates that Florida will use their 
standard assessment periods as specified in Rule 62-303, F.A.C. 
(Impaired Waters Rule) to implement this second provision. These 
proposed duration and frequency components of the criteria are 
consistent with the data set used to derive the criteria that contained 
data from multiple years of record, all seasons, and a variety of 
hydrologic conditions. EPA has determined that this frequency of 
excursions should not result in unacceptable effects on aquatic life as 
it will allow the canal aquatic system enough time to recover from an 
occasionally elevated year of nutrient loadings. The Agency requests 
comment on these proposed duration and frequency expressions of the 
canal numeric nutrient criteria.
    EPA notes that some scientists and resource managers have suggested 
that nutrient criteria duration and frequency expressions should be 
more restrictive to avoid seasonal or annual ``spikes'' from which the 
aquatic system cannot easily recover, whereas others have suggested 
that criteria expressed as simply a long-term average of annual 
geometric means, consistent with data used in criteria derivation, 
would still be protective. EPA requests comment on alternative duration 
and frequency expressions that might be considered protective, 
including (1) a criterion-duration expressed as a monthly average or 
geometric mean, (2) a criterion-frequency expressed as meeting 
allowable magnitude and duration every year, (3) a criterion-frequency 
expressed as meeting allowable magnitude and duration in more than half 
of the years of a given assessment period, and (4) a criterion-
frequency expressed as meeting the allowable magnitude and duration as 
a long-term average only. EPA further requests comment on whether an 
expression of the criteria in terms of an arithmetic average of annual 
geometric mean values based on rolling three-year periods of time would 
also be protective of the designated use.
(3) Request for Comment and Data on Proposed Approach
    EPA believes the proposed numeric nutrient criteria for south 
Florida canals in this rule are protective of the designated uses, 
consistent with CWA section 303(c)(2)(A) and 40 CFR 131.11(a)(1). EPA 
solicits comment on the approaches taken by the Agency in this 
proposal, the data underlying those approaches, and the proposed 
criteria. EPA is seeking other pertinent scientific data and 
information that are readily available related to nutrient 
concentrations or nutrient responses in Class III canals in south 
Florida.

[[Page 4214]]

    EPA is soliciting comment specifically on the selection of criteria 
parameters for TN, TP, and chlorophyll a; development of criteria for 
Class III canals across south Florida; and the conclusion that the 
proposed criteria for Class III canals are protective of designated 
uses and adequately account for the spatial and temporal variability of 
nutrients.
(4) Alternative Approaches for Comment
    EPA is requesting comments and views on the advantages and 
disadvantages of alternative approaches to deriving protective criteria 
for south Florida canals. These approaches include: (1) A stressor-
response approach (based on data from all canals or canals grouped by 
soil type), and (2) methodologies that have been employed to develop 
nutrient targets in an EPA-proposed TMDL for dissolved oxygen and 
nutrients.\108\
---------------------------------------------------------------------------

    \108\ Proposed Total Maximum Daily Load (TMDL) for Dissolved 
Oxygen and Nutrient in the Everglades. Prepared by U.S. EPA Region 
4. September 2007.
---------------------------------------------------------------------------

    As previously described in Section III.E(2)(b), EPA considered the 
underlying soil type of south Florida canals as a possible basis for 
geographic classification. Analysis of the underlying soil types, 
indicated by STATSGO,\109\ led EPA to identify the following four canal 
regions: Everglades Agricultural Area (EAA) comprised of histosol and 
entisol soils, EvPA comprised of histosol and entisol soils, areas west 
of the EvPA and EAA, or West Coast, comprised of spodosol and alfisol 
soils, and areas east of the EvPA and EAA, or East Coast, comprised of 
spodosol, entisol, and alfisol soils.
---------------------------------------------------------------------------

    \109\ State Soil Geographic (STATSGO) database provided by the 
U.S. Department of Agriculture, Natural Resources Conservation 
Service (NRCS).
---------------------------------------------------------------------------

    Subsequent to classification, the proposed statistical 
distribution-based approach or the alternatives to the proposed 
approach described in the following sections could be used to derive 
numeric nutrient criteria by canal region for any or all of the 
proposed criteria (i.e., TN, TP, and chlorophyll a) provided that 
sufficient data are available.
(a) Stressor-Response Approach
    EPA considered two statistical analyses for assessing the stressor-
response relationship between nutrients and biological response. In 
contrast to the proposed option, which included only data from sites 
with no evidence of nutrient impairment, the stressor-response analyses 
included all data regardless of whether sites were associated with 
WBIDs that have been determined to be impaired. EPA conducted linear 
and quantile regression analyses between chlorophyll a, TP, and TN on a 
regional and aggregated regional basis. EPA used the linear regression 
model as a statistical tool to predict the chlorophyll a response based 
on matched chlorophyll a and TN and TP data. Similarly, quantile 
regression was used to analyze the matched nutrient and chlorophyll a 
data. In this application, quantile regression was used to predict the 
90th percentile of the distribution of chlorophyll a concentration at a 
given concentration of TN or TP.
    To apply either statistical approach for developing numeric 
nutrient criteria for TP or TN, EPA would need to identify the 
concentration of chlorophyll a that would be protective of the 
designated use for these canal systems. One approach would be to use 
EPA's proposed chlorophyll a criterion of 4.0 [mu]g/L for canals to 
derive the TN and TP criteria from stressor-response relationships.
(b) Calculation of TP Criteria for the Everglades Agricultural Area 
(EAA) Using a Downstream Protection Approach
    EPA considered using the methodologies described in the EPA-
proposed TMDL \110\ for dissolved oxygen and nutrients to develop 
numeric nutrient criteria, specifically TP, for portions of the EAA. 
These methodologies are described in the TMDL in Section 4.2.2.1 of the 
TMDL document, ``Approach <greek-i>1: Estimate STA inflow loads 
resulting in WQS in downstream waters'', and Section 4.2.2.2 of the 
TMDL document, ``Approach <greek-i>2: Simple modeling approach.'' The 
first approach takes into account the downstream criterion of the EvPA 
and the performance of the stormwater treatment areas (STAs). Based on 
these considerations, inflowing TP concentrations within the EAA to the 
STAs were derived to meet the downstream EvPA TP criterion of 0.010 mg/
L. The second approach used a model that extrapolated natural 
background TP concentrations, based on land use changes, for specific 
WBIDs within the EAA. These approaches could support the derivation of 
numeric nutrient criteria for TP within the EAA region. Approach 
<greek-i>1 would result in a TP concentration of 0.10 mg/L, while 
Approach <greek-i>2 would result in a TP concentration of 0.087 mg/L.
---------------------------------------------------------------------------

    \110\ Proposed Total Maximum Daily Load (TMDL) for Dissolved 
Oxygen and Nutrient in the Everglades. Prepared by U.S. EPA Region 
4. September 2007.
---------------------------------------------------------------------------

(5) Request for Comment and Data on Alternative Approaches
    The alternatives for Class III south Florida canal criteria in this 
proposed rule represent alternative approaches given the availability 
of data in the State of Florida to date and are consistent with the 
requirements of both the CWA and EPA's implementing regulations. EPA is 
soliciting comment on the alternative approaches considered by the 
Agency in this proposal, the data underlying those approaches, and the 
proposed alternatives themselves, including criteria expressed as an 
upper percentile maxima not to be exceeded more than 10% of the time in 
one year, similar to those discussed for lakes. For further information 
on the upper percentile criteria for canals, refer to EPA's TSD on 
Florida's Inland Waters, Chapter 4: Methodology for Deriving U.S. EPA's 
Proposed Criteria for Canals. EPA is seeking other pertinent data and 
information related to nutrient concentrations or nutrient responses in 
Class III canals in south Florida.

F. Comparison Between EPA's and Florida DEP's Proposed Numeric Nutrient 
Criteria for Florida's Lakes and Flowing Waters

    To date, Florida has invested significant resources in its 
statewide nutrient criteria effort, and has made substantial progress 
toward developing numeric nutrient criteria. For several years, FDEP 
has been actively working with EPA on the development of numeric 
nutrient criteria and EPA has worked extensively with FDEP on data 
interpretation and technical analyses for developing EPA's recommended 
numeric nutrient criteria proposed in this rulemaking.
    On January 14, 2009, EPA formally determined that numeric nutrient 
criteria were necessary to protect Florida's lakes and flowing waters 
and should be developed by January 14, 2010. FDEP, independently from 
EPA, initiated its own State rulemaking process to adopt numeric 
nutrient water quality criteria protective of Florida's lakes and 
flowing waters. According to FDEP, the State initiated its rulemaking 
process to facilitate the assessment of designated use attainment for 
Florida's waters and to provide a better means to protect its waters 
from the adverse effects of nutrient over-enrichment. Florida 
established a technical advisory committee, which met over a number of 
years, to help develop its proposed numeric nutrient criteria. The 
State also held several public workshops to solicit

[[Page 4215]]

comment on the draft WQS. While FDEP was progressing with its State 
rulemaking, EPA moved forward to develop Federal numeric nutrient 
criteria for Florida's lakes and flowing waters, consistent with EPA's 
January 14, 2009 determination and based on the best available science.
    Most recently, in July 2009, FDEP solicited public comment on its 
proposed numeric nutrient criteria for lakes and flowing waters. In 
October 2009, FDEP decided not to bring the draft criteria before the 
Florida Environmental Regulation Commission (ERC), as had been 
previously scheduled. FDEP did not make any final decisions as to 
whether it might be appropriate to ask the ERC to adopt the criteria or 
some portions of the criteria at a later date.
    As described in Section III., EPA is proposing numeric nutrient 
criteria for the following four water body types: Lakes, streams, 
springs and clear streams, and canals in south Florida. Given that FDEP 
has made its proposed numeric nutrient criteria available to the public 
via its Web site (http://www.dep.state.fl.us/water/wqssp/nutrients/index.htm), it is worth providing a comparative overview between the 
criteria and approaches that EPA is proposing in this rulemaking and 
the criteria and approaches FDEP had initially proposed. Both EPA and 
FDEP developed numeric criteria recognizing the hydrologic and spatial 
variability of nutrients in Florida's lakes and flowing waters. As FDEP 
indicated on its Web site, FDEP's preferred approach is to develop 
cause and effect relationships between nutrients and valued ecological 
attributes, and to establish nutrient criteria based on those cause and 
effect relationships that ensure that the designated uses of Florida's 
waters are protected and maintained. As described in EPA's guidance, 
EPA also recommends this approach when scientifically defensible data 
are available. Where cause and effect relationships could not be 
demonstrated, however, both FDEP and EPA relied on a distribution-based 
approach to derive numeric nutrient criteria protective of applicable 
designated uses.
    To set numeric nutrient criteria for lakes, EPA, like FDEP, is 
proposing a classification scheme using color and alkalinity based upon 
substantial data that show that lake color and alkalinity play an 
important role in the degree to which TN and TP concentrations result 
in a biological response such as elevated chlorophyll a levels. EPA and 
FDEP both found that correlations between nutrients and response 
parameters were sufficiently robust to use for criteria development in 
Florida's lakes. EPA is proposing the same chlorophyll a criteria for 
colored lakes and clear alkaline lakes as FDEP proposed, however, EPA 
is proposing a lower chlorophyll a criterion for clear acidic lakes. 
EPA, like FDEP, is also proposing an accompanying supplementary 
analytical approach that Florida can use to adjust general TN and TP 
lake criteria within a certain range where sufficient data on long-term 
ambient TN and TP levels are available to demonstrate that protective 
chlorophyll a criteria for a specific lake will still be maintained and 
attainment of the designated use will be assured.

--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                       EPA proposed criteria                         Florida proposed criteria
                       Lake class                        -----------------------------------------------------------------------------------------------
                                                          Chl a, [mu]g/L     TN, mg/L        TP, mg/L     Chl a, [mu]g/L     TN, mg/L        TP, mg/L
--------------------------------------------------------------------------------------------------------------------------------------------------------
Colored Lakes > 40 PCU..................................              20       1.23-2.25     0.050-0.157              20       1.23-2.25      0.05-0.157
Clear Lakes, Alkaline <= 40 PCU and > 50 mg/L CaCO3.....              20       1.00-1.81     0.030-0.087              20       1.00-1.81      0.03-0.087
Clear Lakes, Acidic <= 40 PCU and <= 50 mg/L CaCO3......               6     0.500-0.900     0.010-0.030               9       0.85-1.14     0.015-0.043
--------------------------------------------------------------------------------------------------------------------------------------------------------

    To set numeric nutrient criteria for streams, FDEP recommended a 
statistical distribution approach based on ``benchmark sites'' 
identified in five nutrient regions (five regions for TP and two 
regions for TN), given that FDEP determined cause and effect 
relationships to be insufficiently robust for establishing numeric 
thresholds. FDEP relied on the use of a narrative criterion to protect 
downstream waters. EPA also concluded that a scientifically defensible 
cause and effect relationship could not be demonstrated with the 
available data and that a distribution-based approach was most 
appropriate. However, EPA considered an alternative approach that 
evaluated a combination of biological information and data on the 
distribution of nutrients in a substantial number of healthy stream 
systems to derive scientifically sound TN and TP criteria for streams.
    The respective criteria for instream protection of Florida's 
streams derived using EPA's recommended approach and FDEP's recommended 
approach are comparable.

----------------------------------------------------------------------------------------------------------------
                                                EPA proposed                                       FL proposed
                                                  instream                                          instream
                                                  criteria        Florida nutrient watershed        criteria
       EPA nutrient watershed regions        ------------------             regions            -----------------
                                              TN (mg/  TP (mg/                                  TN (mg/  TP (mg/
                                                 L)       L)                                       L)       L)
----------------------------------------------------------------------------------------------------------------
Panhandle...................................    0.824    0.043  Panhandle.....................    0.820    0.069
Bone Valley.................................    1.798    0.739  Bone Valley...................    1.730    0.415
Peninsula...................................    1.205    0.107  Peninsula.....................  .......    0.116
North Central...............................    1.479    0.359  North Central.................  .......    0.322
                                              .......  .......  Northeast.....................  .......    0.101
----------------------------------------------------------------------------------------------------------------

    In terms of protecting downstream waters, EPA used best available 
science and data related to downstream waters and found that there are 
cases where the numeric nutrient criteria EPA is proposing to protect 
instream aquatic life may not be stringent enough to ensure protection 
of WQS for aquatic life in certain downstream lakes and estuaries. 
Accordingly, EPA is proposing an equation to be used to adjust stream 
TP criteria to protect downstream lakes, and a different methodology to 
adjust TN criteria for streams to ensure protection of WQS for

[[Page 4216]]

downstream estuaries. In cases where a stream first flows into a lake 
and then flows out from the lake into another lake or estuary, the 
portion of the stream that exits the lakes needs to comply with the 
downstream protection values for estuaries, assuming that is the 
terminal reach.
    EPA is proposing the same nitrate-nitrite causal variable criterion 
for springs and clear streams as proposed by FDEP. For canals in south 
Florida, EPA is proposing a statistical distribution approach based on 
sites meeting designated uses with respect to nutrients (i.e., not 
identified as impaired by FDEP) identified in four canal regions. FDEP 
did not propose numeric nutrient criteria for canals in its rulemaking.
    Please refer to Section IV. Under What Conditions Will Florida Be 
Removed From a Final Rule for information on how State-adopted and EPA-
approved WQS could become effective under the CWA 303(c).

G. Applicability of Criteria When Final

    EPA's proposed numeric nutrient criteria for Florida's lakes and 
flowing waters will be effective for CWA purposes 60 days after 
publication of final criteria 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, approved by EPA). EPA requests comment on this proposed 
effective date. 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. 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 meet the goals articulated in section 101(a)(2) of the CWA and the 
waters for which EPA is proposing criteria. Pursuant to the schedule 
set out in EPA's January 2009 determination, Class II waters will be 
addressed in rulemaking in January 2011. For water bodies designated as 
Class I and Class III predominately fresh waters, any final EPA numeric 
nutrient criteria will be applicable CWA water quality criteria for 
purposes of implementing CWA programs including permitting under the 
NPDES program, as well as monitoring and assessment based on applicable 
CWA WQS and establishment of TMDLs.
    The proposed criteria in this rule, if and when finalized, would be 
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 proposed 40 CFR 
131.43(d)(2). For example, Florida regulations at Rule 62-4.244, F.A.C. 
authorize mixing zones when deriving effluent limitations for 
discharges of pollutants to Florida waters. These regulations would 
apply to permit limitations implementing the criteria in this rule. 
This proposal includes some additional language on mixing zone 
requirements to help guide Florida in developing and applying mixing 
zone policies for nutrient criteria. Specifically, EPA provides that 
the criteria apply at the appropriate locations within or at the 
boundary of the mixing zones; otherwise the criteria apply throughout 
the water body including at the point of discharge into the water body. 
See proposed 40 CFR 131.43(d)(2)(i). Likewise, EPA includes proposed 
regulatory language specifying that Florida use an appropriate design 
flow condition, one that matches the proposed criteria duration and 
frequency, for use in deriving permit limits and establishing wasteload 
and load allocations for a TMDL. See proposed 40 CFR 131.43(d)(2)(ii).
    In addition, EPA recognizes that Florida regulations include 
provisions for assessing whether waters should be included on the list 
of impaired waters pursuant to section 303(d) of the CWA. See Rule 62-
303, F.A.C. The Impaired Waters Rule, or IWR, sets out a methodology to 
identify waters that do not meet the State's WQS and, therefore, are 
required to be included on CWA section 303(d) lists. The current IWR 
does not address how to assess waters based on EPA's proposed numeric 
nutrient criteria. The numeric nutrient criteria in any final rule, 
nevertheless, will be applicable WQS that must be addressed when the 
State assesses waters pursuant to CWA section 303(d).
    EPA proposes language in this rulemaking that acknowledges the IWR 
procedures and their function, specifying that those procedures apply 
where they are consistent with the level of protection provided by the 
proposed criteria. See proposed 40 CFR 131.43(d)(2)(iii). Some IWR 
provisions, which describe the sufficiency or reliability of 
information necessary for the State to make an attainment decision, do 
not change the level of protection afforded Florida waters. These are 
beyond the scope of WQS under CWA section 303(c). Other provisions of 
the IWR may provide some additional detail relevant to assessment, such 
as the number of years worth of data assessed for a particular listing 
cycle submittal, which should be consistent with the level of 
protection provided with the proposed criteria. Should any IWR 
provisions apply a different level of protection than the Federal 
criteria when making attainment decisions based on proposed criteria, 
EPA would expect to take appropriate action to ensure that the States' 
CWA section 303(d) list of impaired waters includes all waters not 
attaining the Federal criteria.

IV. Under What Conditions Will Federal Standards Be Either Not 
Finalized or 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 proposing numeric nutrient criteria for 
Florida's lakes and flowing waters, Florida continues to have the 
option to adopt and submit to EPA numeric nutrient criteria for the 
State's lakes and flowing waters consistent with CWA section 303(c) and 
implementing regulations at 40 CFR part 131. Consistent with CWA 
section 303(c)(4), if Florida adopts and submits numeric nutrient 
criteria and EPA approves such criteria as fully satisfying the CWA 
before publication of the final rulemaking, EPA will not proceed with 
the final rulemaking for those waters for which EPA approves Florida's 
criteria.
    Pursuant to 40 CFR 131.21(c), if EPA does finalize this proposed 
rule, the EPA promulgated WQS would be applicable WQS for purposes of 
the CWA until EPA withdraws the federally-promulgated standard. 
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 only if 
and when Florida adopts and EPA approves numeric nutrient criteria that 
fully meet the requirements of section 303(c) of the CWA and EPA's 
implementing regulations at 40 CFR part 131.
    If EPA finalizes the proposed restoration standard provision 
(discussed in Section VI below), that provision would be adopted into 
regulation and would allow Florida to establish interim designated uses 
with associated water quality criteria, while maintaining the full CWA 
section 101(a)(2) aquatic life and/or recreational

[[Page 4217]]

designated use of the water as the ultimate goal. EPA may proceed to 
promulgate numeric nutrient criteria for Florida together with or 
separate from EPA's proposed restoration standards provision, depending 
on the comments received on that proposal.

V. Alternative Regulatory Approaches and Implementation Mechanisms

A. Designating Uses

    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].'' CWA section 303(c)(1). EPA's 
regulation at 40 CFR 131.3(f) defines ``designated uses'' as ``those 
uses specified in water quality standards for each water body or 
segment whether or not they are being attained.'' Under 40 CFR 131.10, 
EPA's regulation addressing ``Designation of uses'', 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), 40 CFR 131.2 
provides that states ``should, wherever attainable, provide water 
quality for the protection and propagation of fish, shellfish, and 
wildlife and for recreation in and on the water.'' Where states do not 
designate those uses, or remove those uses, they must demonstrate that 
such uses are not attainable consistent with 40 CFR 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 and/or the associated 
pollutant criteria 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)).
    Within the framework described above, states have discretion in 
designating uses. EPA's proposed numeric nutrient criteria for lakes 
and flowing waters would 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 the Class I or Class III designated use 
for any particular water body ultimately affected by this rule, and EPA 
finds that removal to be consistent with CWA section 303(c) and the 
regulations at 40 CFR part 131, then the federally-promulgated numeric 
nutrient criteria would not apply to that water body. Instead, the 
nutrient criteria associated with the newly designated use would apply 
to that water body. FDEP has recently restarted an effort to refine the 
State's current designated use classifications. As this process 
continues, EPA expects that the State may find some instances where 
this particular discussion may be relevant and useful as the refinement 
of uses is investigated further.
    Where states can identify multiple waters with similar 
characteristics and constraints on attainability, EPA interprets the 
Federal WQS regulation to allow states to conduct a ``categorical'' use 
attainability analysis (UAA) under 40 CFR 131.10(g) for such waters. 
This approach may reduce data collection needs, allowing a single 
analysis to represent many sites. To use such an approach, however, the 
State would need to have enough information about each particular site 
to reliably place each site into a broader category and Florida would 
need to specifically identify each site covered by the analysis. 
Florida may wish to consider such an approach for certain waters, such 
as a network of canals with similar hydrologic and morphological 
characteristics, which can be characterized as a group and where the 
necessary level of protection may differ substantially from other lakes 
or flowing waters within the State.

B. Variances

    A variance is a temporary modification to the designated use and 
associated water quality criteria that would otherwise apply to the 
receiving water. A variance is based on a UAA and identifies the 
highest attainable use and associated criteria during the variance 
period. Typically, variances are time-limited (e.g., three years), but 
renewable. Modifying the designated use for a particular water 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 in a short period of 
time. By maintaining the standard rather than changing it, 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 geographical coverage, 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. A variance allows, among 
other things, NPDES permits to be written such that reasonable progress 
is made 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 also CWA section 
301(b)(1)(C).
    For purposes of this proposal, EPA is proposing criteria that apply 
to use designations that Florida has already established. EPA believes 
that the State has sufficient authority to use its adopted and EPA-
approved variance procedures with respect to modification of their 
Class I or Class III uses as it pertains to any federally-promulgated 
nutrient criteria. For this reason, EPA is not proposing a Federal 
variance procedure.

C. Site-Specific Criteria

    A site-specific criterion is an alternative value to a statewide, 
or otherwise applicable, water quality criterion that meets the 
regulatory test of protecting the designated use and having a basis in 
sound science, but is tailored to account for site-specific conditions. 
Site-specific alternative criteria (SSAC) may be more or less stringent 
than the otherwise applicable criteria. In either case, because the 
SSAC must protect the same designated use and must be based on sound 
science (i.e., meet the requirement of 40 CFR 131.11(a)), there is no 
need to modify the designated use or conduct a UAA. SSAC may be 
appropriate when additional scientific consideration can bring added 
precision or accuracy to express the necessary level or concentration 
of a water quality

[[Page 4218]]

parameter that is protective of the designated use.
    Florida has adopted procedures for developing and adopting SSAC in 
its WQS regulations at Florida Administrative Code (Rule 62-302.800, 
F.A.C.). Florida's Type I SSAC procedure is intended to address site-
specific situations where a particular water body cannot meet the 
applicable water quality criterion because of natural conditions. See 
Rule 62-302.800(1). Florida's Type II SSAC procedure is intended to 
address site-specific situations other than natural conditions where it 
can be established that an alternative criterion from the broadly 
applicable criteria established by the State is protective of a water's 
designated uses. See Rule 62-302.800(1), F.A.C. Florida's Type II 
procedure is primarily intended to address toxics but there is no 
limitation in its use for other parameters, except for certain 
parameters identified by FDEP, including nutrients. See Rule 62-
302.800(2). Florida's regulations currently do not allow use of Type II 
procedures for nutrient criteria development because the State 
currently does not have broadly applicable numeric nutrient criteria 
for State waters. Rather, the current narrative criterion for nutrients 
is implemented by translating it into numeric loads or concentrations 
on a case-by-case basis. EPA's proposed rule would not affect Florida's 
Type I or Type II SSAC procedures.
    EPA believes that there would be benefit in establishing a specific 
procedure in the Federal rule for EPA adoption of SSAC. In this 
rulemaking, EPA is proposing a procedure whereby the State could 
develop a SSAC and submit the SSAC to EPA with supporting documentation 
for EPA's consideration. The State SSAC could be developed under either 
the State SSAC procedures or EPA technical processes as set out more 
fully below. EPA elected to propose this approach because this 
procedure maintains the State in a primary decision-making role 
regarding development of SSAC for State waters. The procedure that EPA 
is proposing would also allow the State to submit a proposed SSAC to 
EPA without having to first go through the State's rulemaking process.
    The proposed procedure would provide that EPA could determine that 
the SSAC should apply in lieu of the generally applicable criteria 
promulgated pursuant to this rule. The proposed procedures provide that 
EPA would solicit public comment on its determination. Because EPA's 
rule would establish this procedure, implementation of this procedure 
would not require withdrawal of federally-promulgated criteria for 
affected water bodies in order for the 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.
    EPA also considered technical processes necessary to develop 
protective numeric nutrient criteria on a site-specific basis. To 
complete a thorough and successful analysis to develop numeric nutrient 
SSAC, EPA expects the State to conduct, or direct applicants to the 
State to conduct, a variety of supporting analyses. For the instream 
protection value (IPV) for streams, this analysis would, for example, 
consist 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 nutrients, such as periphyton algal 
thickness or chlorophyll a levels. The former analysis will help 
address concerns that a potential nutrient effect is masked by other 
stressors (such as turbidity which can limit light penetration and 
primary production response to nutrient response), whereas the latter 
analysis will help address concerns that a potential nutrient effect is 
lagging in time and has not yet manifested itself. Indicators of 
shorter-term response generally would not be expected to exhibit a lag 
time.
    It will also be important to examine a stream system on a watershed 
basis to ensure that a SSAC established for one segment does not result 
in adverse effects in nearby segments. For example, a shaded, 
relatively swift flowing segment may open up to a shallow, slow moving, 
open canopy segment that is more vulnerable to adverse nutrient 
impacts. Empirical data analysis of multiple factors affecting the 
expression of response to nutrients and mechanistic models of ecosystem 
processes can assist in this type of analysis. It will also be 
necessary to ensure that a larger load allowed from an upstream segment 
as a result of a SSAC does not compromise protection on a downstream 
segment that has not been evaluated.
    The intent of this discussion is to illustrate a process that is 
rigorous and based on sound scientific rationale, without being 
inappropriately onerous to complete. Corollary analyses for a lake, 
spring or clear stream, or canal situation would need to be pursued for 
a SSAC on those systems.
    In addition to the procedure that EPA is proposing, Florida always 
has the option of submitting State-adopted SSAC as new or revised WQS 
to EPA for review and approval under the CWA section 303(c). There is 
no bar to a state adopting new or revised WQS for waters covered by a 
federally-promulgated WQS. For any State-adopted SSAC that EPA approves 
under section 303(c) of the Act, EPA would also have to complete 
federal rulemaking to withdraw the Federal WQS for the affected water 
body before the State SSAC would be the applicable WQS for the affected 
water body for purposes of the Act. As discussed above, Florida WQS 
regulations currently do not authorize the State to adopt nutrient SSAC 
except where natural conditions are outside the limits of broadly 
applicable criteria established by the State (Rule 62-302.800, F.A.C.).
    This proposed SSAC process would also not limit EPA's authority to 
promulgate SSAC in addition to those developed by the State under the 
process described in this rule. The proposed rule recognizes that EPA 
always has the authority to promulgate through rulemaking SSAC for 
waters that are subject to federally-promulgated water quality 
criteria.

D. Compliance Schedules

    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.'' 40 CFR 122.2. 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). In addition, EPA regulations 
provide that schedules of compliance are to require compliance ``as 
soon as possible.''
    Florida has adopted a regulation authorizing compliance schedules, 
and that regulation is not affected by this proposed rule (Rule 62-
620.620(6), F.A.C.). The regulation provides, in part, for schedules 
providing for compliance ``as soon as sound engineering practices 
allow, but not later than any applicable statutes or rule deadline.'' 
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 under its rule for WQBELs based on federally-promulgated 
criteria.

[[Page 4219]]

VI. Proposed Restoration Water Quality Standards (WQS) Provision

    As described above, many of Florida's waters do not meet the water 
quality goals established by the State and envisioned by the CWA 
because of excess amounts of nutrients. In some cases, restoring these 
waters could take many years to achieve, especially where there is a 
large difference between current water quality conditions and the 
nutrient criteria levels necessary to protect aquatic life. In such 
cases, Florida may conclude that restoration programs will not result 
in waters attaining their designated aquatic life use (and associated 
numeric nutrient criteria) for a long period of time.
    EPA's current regulations provide that a state may remove a 
designated use if it meets certain requirements outlined at 40 CFR 
131.10. Under this provision, if the State demonstrates that a 
designated use is not attainable it may conduct a use attainability 
analysis (UAA) to revise the designated use to reflect the highest 
attainable aquatic life use, even though that use may not meet the CWA 
section 101(a)(2) goal.\111\ Another option that states use to address 
situations for an individual discharger is a discharger-specific 
variance.\112\ Neither of these approaches may be optimal or 
appropriate solutions if a state determines that certain waters cannot 
attain aquatic life uses due to excess nutrient in the near term.
---------------------------------------------------------------------------

    \111\ Clean Water Act section 101(a)(2) states that it is a 
national goal for water quality, wherever attainable, to provide for 
the protection and propagation of fish, shellfish, and wildlife and 
provide for recreation in and on the water
    \112\ A variance is a temporary modification to the designated 
use and associated water quality criteria that would otherwise 
apply. It is based on a use attainability demonstration and targets 
achievement of the highest attainable use and associated criteria 
during the variance period.
---------------------------------------------------------------------------

    Based on numerous workshops, meetings, conversations and day-to-day 
interactions with state environmental managers, EPA understands that 
states interested in restoring impaired water may desire the ability to 
express, in their WQS, successive time periods with incrementally more 
stringent designated uses and criteria that ultimately result in a 
designated use and criteria that reflect a CWA section 101(a)(2) 
designated use. Such an approach would allow the state and stakeholders 
necessary time to take incremental steps to achieve interim WQS as they 
move forward to ultimately attain a CWA section 101(a)(2) designated 
use. Some states have used variances to provide such time in their WQS. 
However, variances are typically time limited (e.g., three years) and 
discharger-specific and do not address the challenges of pursuing 
reductions from a variety of sources across a watershed. In addition, 
Federal regulations are not explicit in requiring that states pursue 
feasible (i.e. attainable) progress toward achieving the highest 
attainable use when implementing a variance. Variances also often lack 
specific milestones and a transparent set of expectations for the 
public, dischargers, and stakeholders.
    EPA seeks comment on this approach to providing Florida with an 
explicit regulatory mechanism for directing state efforts to achieve 
incremental progress in a step-wise fashion, applicable to all sources, 
as a part of its WQS. The proposed regulatory mechanism described in 
this section applies only to WQS for nutrients in Florida waters 
subject to this proposed rule.
    A ``restoration water quality standard'' under EPA's proposed rule 
would be a WQS that Florida could adopt for an impaired water. Under 
EPA's proposal, the State would retain the current designated use as 
the ultimate designated use (e.g. providing for eventual attainment of 
a full CWA section 101(a)(2) designated use and the associated 
criteria). However, under the restoration standard approach proposed in 
this rule, the State would also adopt interim less stringent designated 
uses and criteria that would be the basis for enforceable permit 
requirements and other control strategies during the prescribed 
timeframes. These interim uses could be no less stringent than an 
existing use as defined in 40 CFR 131.3, and would have to meet the 
requirements of 40 CFR 131.10(h)(2). The State would need to 
demonstrate that the interim uses and criteria, as well as the 
timeframe, are based on a UAA evaluation of what is attainable and by 
when. These interim designated uses and criteria and the applicable 
timeframes would all be incorporated into the State WQS on a site-
specific basis, as would be any other designated use change or adoption 
of site-specific criteria.
    For example, a restoration WQS for nutrients for an impaired Class 
I or Class III colored lake in Florida may take the form of the 
following for a lake whose current condition represents severely 
impaired aquatic life with chlorophyll a = 40 mg/L, TN = 2.7 mg/L, and 
TP = 0.15 mg/L:

----------------------------------------------------------------------------------------------------------------
                      Time                         Chl a      TN        TP        Designated Use Description
----------------------------------------------------------------------------------------------------------------
Year 0-5........................................       35      2.4      0.10  Moderately Impaired Aquatic Life.
Year 6-10.......................................       25      1.45     0.06  Slightly Impaired Aquatic Life.
Year 11.........................................       20      1.2      0.05  Full Aquatic Life Use.
----------------------------------------------------------------------------------------------------------------

    Including such revised interim designated uses and criteria within 
the regulations could support efforts by Florida to formally establish 
enforceable long-term plans for different watersheds or stream reaches 
to attain the ultimate designated use and the associated criteria. At 
the same time, the State would be able to ensure that its WQS 
explicitly reflect the attainable designated uses and water quality 
criteria to be met at any given time, consistent with the CWA and 
implementing regulations.
    Restoration WQS would provide in the Federal regulations the 
framework for authorizing the State of Florida to adopt restoration WQS 
for nutrients, along with maintaining the availability of other tools 
(e.g., variances and compliance schedule provisions), which provide 
flexibility regarding permitting individual dischargers. Restoration 
WQS would require a full public participation process to assure 
transparency as well as the opportunity for different parties to work 
together, exchange information and determine what is actually 
attainable within a particular time frame. Going through this process 
would provide Florida with a transparent set of expectations to push 
its waters towards restoration in a realistic yet verifiable manner.
    In this notice, EPA proposes restoration WQS as a clear regulatory 
pathway for the State of Florida to adjust the Class I and Class III 
designated uses (and associated nutrient criteria) of waters impaired 
by nutrients that is intended to promote active restoration, maintain 
progressive improvement, and ensure accountability. This approach would 
provide the State of Florida with the flexibility to adopt revised 
designated uses and criteria under a set of specific regulatory 
requirements.

[[Page 4220]]

    Under this proposal, the interim designated uses and criteria would 
be the basis for NPDES permits during the applicable period reflecting 
the fact that the restoration WQS introduces the critical element of 
time as part of the complete WQS. This is intended to allow imposition 
of the maximum feasible point source controls and nonpoint source 
nutrient reduction strategies to be phased in within the overall 
context of restoration activities within the watershed. By reflecting 
how it expects the existing poor quality of its waters to incrementally 
improve to achieve longer-term WQS goals, Florida could create the 
flexibility to explore more innovative ways to reach the requirements 
of the next phase, thus possibly reducing costs or allowing new 
approaches to resolve complex technological issues, and maximizing 
transparency with the public during each phase. These waters, however, 
would still be considered impaired for CWA assessment and listing 
purposes because the ultimate designated use and criteria would be part 
of the restoration WQS and would not yet be met.
    The restoration standards would be Florida WQS revisions that would 
go through the process of first being adopted under State law and then 
approved by EPA. This proposal would include eight requirements for the 
development of a restoration WQS for nutrients:
    1. It must be demonstrated that it is infeasible to attain the full 
CWA section 101(a)(2) aquatic life designated use during the time 
periods established for the restoration phases with a UAA based on one 
of the factors at 40 CFR 131.10(g).
    2. The highest attainable designated use and numeric criteria that 
apply at the termination of the restoration WQS (i.e., the ultimate 
long-term designated use and numeric criteria to be achieved) must be 
specified and this use is to include, at a minimum, uses that are 
consistent with the CWA section 101(a)(2) uses.
    3. Interim restoration designated uses and numeric water quality 
criteria, with each based on achieving the maximum feasible progress 
during the applicable phase as determined in the UAA, must be 
established.
    4. Specific time periods for each restoration phase must be 
established. The length of each phase must be based on the UAA 
demonstration of when interim uses can be attained on a case-specific 
basis. Interim restoration designated uses and numeric water quality 
criteria must reflect the highest attainable use during the time period 
of the restoration phase. The sum of these times periods may not exceed 
twenty years.
    5. The spatial extent to which the restoration WQS will apply 
(e.g., how far downstream the restoration WQS would apply) must be 
specified. EPA notes the importance of continuing to meet the 
requirements for protection of downstream WQS as expressed in section 
40 CFR 131.10(b). Adopting restoration WQS upstream of another impaired 
water may mean the State should also consider restoration WQS for the 
downstream water.
    6. The regulatory requirements for public participation and EPA 
review and approval whenever revising its WQS must continue to be met. 
Specifically, a restoration WQS may not include interim uses less 
stringent than a use that is an ``existing use'' as defined in 40 CFR 
131.3 or that do not meet the requirements of 40 CFR 131.10(h)(2).
    7. The State must include in its restoration WQS that if the water 
body does not attain the interim designated use and numeric water 
quality criteria at the end of any phase, the restoration WQS will no 
longer be in effect and the designated use and criteria that was to 
become effective at the end of the final restoration phase will become 
immediately effective unless Florida adopts and EPA approves a 
different revised designated use and criteria.
    8. The State must provide that waters for which a restoration WQS 
is adopted will be recognized as impaired for the purposes of listing 
impaired waters under section 303(d) of the CWA until the final use is 
attained.
    Under this proposal, EPA would require Florida to adopt the 
ultimate highest attainable designated use and criteria along with 
multiple phases reflecting the stepwise improvements in water quality 
between the initial effective date and when they expect to meet the 
ultimate highest attainable use as a single restoration WQS package. As 
with any revision to an aquatic life use, Florida would be required to 
demonstrate that the ultimate highest attainable designated use cannot 
be attained during the restoration period, based on one of the factors 
at 40 CFR 131.10(g)(1)-(6) (i.e., through a UAA). EPA would review the 
WQS and all supporting documents before approving the restoration WQS.
    At the beginning of the first restoration phase, the State would 
identify current conditions and establish the principle that there can 
be no further degradation. WQS for the first restoration phase should 
reflect the outcomes of all controls that can be implemented within the 
first restoration phase. Additionally, EPA expects that the interim 
restoration designated use and numeric criteria that are attainable at 
the end of the restoration phase apply at the beginning of each phase 
as well as throughout the phase. For each phase, the State would adopt 
interim designated uses and numeric water quality criteria that reflect 
achieving the maximum feasible progress. At the end of the first phase, 
EPA would expect the water body to be meeting the first interim 
designated use and water quality criteria.
    At the beginning of the second phase, the next (more stringent) 
interim designated use and water quality criteria would go into effect 
as the applicable WQS that the State would use to direct the next set 
of control actions. At the conclusion of the second phase, the next 
(more stringent) interim designated use and water quality criteria 
would become the applicable WQS. This process would repeat with each 
subsequent phase. Permit limits written during the restoration phases 
would include effluent limits as stringent as necessary to meet the 
applicable interim designated uses and numeric water quality criteria. 
In constructing each restoration phase (i.e. duration and interim 
designated use and numeric water quality criteria), EPA will require 
the maximum feasible progress. This means that necessary control 
actions that would improve water quality and can be implemented within 
the first phase must be reflected in the interim targets for the first 
restoration phase. This would include all technology-based requirements 
for point sources, and cost-effective and reasonable BMPs for nonpoint 
sources. For treatment upgrades to point sources, EPA expects careful 
scrutiny of technology that has been successfully implemented in 
comparable situations and presumes that this is feasible. EPA further 
expects careful scrutiny of all existing and new technology that will 
help achieve the ultimate highest attainable use.
    EPA recognizes that circumstances may change as controls are 
implemented and that new information may indicate that the timeframes 
established in the restoration WQS are too lengthy or possibly 
unrealistically short. If this is the case, the state has the 
discretion under 40 CFR 131.10 to conduct a new UAA and revise the 
interim targets in its restoration WQS after a full public process and 
EPA approval. However, there is a significant burden on the state to 
demonstrate what changed to alter the initial analysis and associated 
expectations for what was attainable for that phase. EPA would expect 
such a revision only if there was significant new information that

[[Page 4221]]

demonstrated that a different schedule and/or set of interim standards 
represents the maximum feasible progress towards the final designated 
use and criteria.
    If at the end of a phase, the water body is not meeting interim 
targets, then the restoration WQS would no longer be applicable. In 
such a case, the applicable WQS would be the ultimate highest 
attainable use and associated criteria unless the state adopted and 
submitted for EPA approval a revised WQS. This would help ensure that 
there would be no delay in implementing control measures. 
Alternatively, EPA considered an option of allowing the subsequent 
restoration phases to become applicable on the schedule adopted in the 
restoration WQS and as supported by the original UAA demonstration, 
even if the interim use and criteria are not fully achieved on 
schedule. This might have the advantage of encouraging the adoption of 
ambitious interim goals in the initial restoration standards, and would 
allow continued orderly progress towards achievement of the final use 
and criterion even where an interim step was not fully attained. EPA 
solicits comment on this alternative approach.
    To develop restoration WQS for numeric nutrient criteria, EPA would 
expect that the state identify waters in need of restoration, produce 
an inventory of point and nonpoint sources within the watershed, and 
evaluate current ambient conditions and the necessary reductions to 
achieve the numeric criteria. The next part of the process would 
involve determining the combinations of control strategies and 
management practices available, how likely they are to produce results, 
and the resources needed to implement them. At this point, the State 
would be in a good position to determine how much pollution reduction 
is likely to be attainable under what timeframes. The State could use 
this information to establish the time periods for each restoration 
phase consistent with the maximum feasible and attainable progress 
toward meeting the numeric criteria, establish interim restoration 
designated uses and water quality criteria, and make the necessary 
demonstration that it is infeasible to attain the long-term designated 
use during the time periods established and that the interim phases 
reflect the highest attainable uses and associated criteria.
    For excess nutrient pollution, the contributors to nutrient 
pollution could include publicly-owned treatment works (POTWs), 
industrial dischargers, urban and agricultural runoff, atmospheric 
deposition, and septic systems. Restoration WQS might reflect in an 
early phase, for example, all feasible short-term POTW treatment 
upgrades and a schedule to select, fund, and implement longer term 
nutrient reduction technologies, while aggressively pursuing reductions 
in nonpoint source runoff. This might include specific plans and a 
schedule to develop and implement innovative alternative approaches, 
such as trading programs, where appropriate.
    In Florida, many of the steps described above occur in the context 
of Basin Management Action Plans (BMAPs). FDEP describes BMAPs as:

    * * *the ``blueprint'' for restoring impaired waters by reducing 
pollutant loadings to meet the allowable loadings established in a 
Total Maximum Daily Load (TMDL). It represents a comprehensive set 
of strategies--permit limits on wastewater facilities, urban and 
agricultural best management practices, conservation programs, 
financial assistance and revenue generating activities, etc.--
designed to implement the pollutant reductions established by the 
TMDL. These broad-based plans are developed with local 
stakeholders--they rely on local input and local commitment--and 
they are adopted by Secretarial Order to be enforceable.

(http://www.dep.state.fl.us/Water/watersheds/bmap.htm) Florida has 
adopted BMAPs for the Hillsborough River Basin, Lower St. John's River, 
Log Branch, Orange Creek, and Upper Ocklawaha, and has plans for others 
to follow. To the extent necessary, FDEP could potentially use aspects 
of the BMAP process and plans such as these to help form the basis for 
restoration WQS.
    In summary, the WQS program is intended to protect and improve 
water quality and WQS are meant to guide actions to address the effects 
of pollution on the Nation's waters. The reality is that as more 
assessments are being done and TMDLs are being contemplated, and as new 
criteria are developed and considered, EPA and states face questions 
about what pollution control measures will meet the WQS, how long it 
might take, and whether it is feasible to attain the WQS established to 
meet the goals of the Act. These questions are often difficult to 
answer because of lack of data, lack of knowledge, and lack of 
experience in attempting restoration of waters. Stakeholders and co-
regulators alike have expressed a desire for ways to pursue progressive 
water quality improvement and evaluate those improvements to gain the 
data, knowledge, and experience necessary to ultimately determine the 
highest attainable use. In response, EPA has been investigating the 
best ways to use UAAs and related tools to make progress in identifying 
and achieving the most appropriate designated use.
    EPA requests comments on the usefulness of the ``restoration WQS'' 
proposal for Florida. EPA requests comment on how restoration WQS will 
operate in conjunction with listing impaired waters, and establishing 
NPDES permit limitations, and nonpoint source control strategies, as 
well as how these requirements should be reflected in regulatory 
language. EPA also requests comment on the proposed 20-year limit on 
the schedule to attain the final use and criteria. EPA also requests 
comments on how a restoration WQS process would be coordinated with the 
TMDL program and whether the transparency and review procedures for the 
two approaches, including the conditions under which a State or EPA 
would be required to develop a TMDL, are comparable. EPA also requests 
comment on any unintended adverse consequences of this approach for any 
of its water quality programs. Finally, EPA requests comment on 
potential definitions of ``maximum feasible progress.''

VII. Statutory and Executive Order Reviews

A. Executive Order 12866: Regulatory Planning and Review

    Under Executive Order (EO) 12866 (58 FR 51735, October 4, 1993), 
this action is a ``significant regulatory action.'' Accordingly, EPA 
submitted this action to the Office of Management and Budget (OMB) for 
review under EO 12866 and any changes made in response to OMB 
recommendations have been documented in the docket for this action.
    This proposed rule does not establish any requirements directly 
applicable to regulated entities or other sources of nutrient 
pollution. Moreover, existing narrative water quality criteria in State 
law already require that nutrients not be present in waters in 
concentrations that cause an imbalance in natural populations of flora 
and fauna in lakes and flowing waters in Florida.

B. Paperwork Reduction Act

    This action does not impose an information collection burden under 
the provisions of the Paperwork Reduction Act, 44 U.S.C. 3501 et seq. 
Burden is defined at 5 CFR 1320.3(b). It does not include any 
information collection, reporting, or record-keeping requirements.

[[Page 4222]]

C. Regulatory Flexibility Act

    The Regulatory Flexibility Act (RFA) generally requires an agency 
to prepare a regulatory flexibility analysis of any rule subject to 
notice and comment rulemaking requirements under the Administrative 
Procedure Act or any other statute unless the agency certifies that the 
rule will not have significant economic impact on a substantial number 
of small entities. Small entities include small businesses, small 
organizations, and small governmental jurisdictions.
    For purposes of assessing the impacts of this action on small 
entities, small entity is defined as: (1) A small business as defined 
by the Small Business Administration's (SBA) regulations at 13 CFR 
121.201; (2) a small governmental jurisdiction that is a government of 
a city, county, town, school district or special district with a 
population of less than 50,000; and (3) a small organization that is 
any not-for-profit enterprise that is independently owned and operated 
and is not dominant in its field.
    Under the CWA WQS program, states must adopt WQS for their waters 
and must submit those WQS to EPA for approval; if the Agency 
disapproves a state standard and the state does not adopt appropriate 
revisions to address EPA's disapproval, EPA must promulgate standards 
consistent with the statutory requirements. EPA also has the authority 
to promulgate WQS in any case where the Administrator determines that a 
new or revised standard is necessary to meet the requirements of the 
Act. These state standards (or EPA-promulgated standards) are 
implemented through various water quality control programs including 
the NPDES program, which limits discharges to navigable waters except 
in compliance with an NPDES permit. The CWA requires that all NPDES 
permits include any limits on discharges that are necessary to meet 
applicable WQS.
    Thus, under the CWA, EPA's promulgation of WQS establishes 
standards that the State implements through the NPDES permit process. 
The State has discretion in developing discharge limits, as needed to 
meet the standards. This proposed rule, as explained earlier, does not 
itself establish any requirements that are applicable to small 
entities. As a result of this action, the State of Florida will need to 
ensure that permits it issues include any limitations on discharges 
necessary to comply with the standards established in the final rule. 
In doing so, the State will have a number of choices associated with 
permit writing. While Florida's implementation of the rule may 
ultimately result in new or revised permit conditions for some 
dischargers, including small entities, EPA's action, by itself, does 
not impose any of these requirements on small entities; that is, these 
requirements are not self-implementing. Thus, I certify that this rule 
will not have a significant economic impact on a substantial number of 
small entities.
    EPA has prepared an analysis of potential costs associated with 
meeting these standards.\113\ EPA's analysis uses the criteria proposed 
by FDEP in July 2009 as a baseline against which to estimate the 
incremental costs of meeting the standards in this proposal. The 
baseline costs of meeting Florida's proposed standards are estimated to 
be $102 to $130 million per year. The incremental costs, over and above 
these baseline costs, of meeting the standards in this NPRM are 
estimated to be $4.7 to $10.1 million per year. This analysis assumes 
that most of these costs would fall on non-point sources and the 
categories of point sources that would be primarily affected are 
municipal wastewater treatment plants and industrial and general 
dischargers.\114\ EPA estimates the incremental costs for these two 
categories of dischargers, including small entities, at about $1 
million per year.
---------------------------------------------------------------------------

    \113\ Refer to Docket ID EPA-HQ-OW-2009-0596.
    \114\ EPA was not able to estimate costs for municipal 
stormwater systems because the need for incremental controls is 
uncertain.
---------------------------------------------------------------------------

D. Unfunded Mandates Reform Act

    Title II of the Unfunded Mandates Reform Act of 1995 (UMRA), Public 
Law 104-4, establishes requirements for Federal agencies to assess the 
effects of their regulatory actions on state, local, and tribal 
governments and the private sector. Under section 202 of the UMRA, EPA 
generally must prepare a written statement, including a cost-benefit 
analysis, for proposed and final rules with ``Federal mandates'' that 
may result in expenditures to state, local, and tribal governments, in 
the aggregate, or to the private sector, of $100 million or more in any 
one year. Before promulgating an EPA rule for which a written statement 
is needed, section 205 of the UMRA generally requires EPA to identify 
and consider a reasonable number of regulatory alternatives and adopt 
the least costly, most cost-effective or least burdensome alternative 
that achieves the objectives of the rule. The provisions of section 205 
do not apply when they are inconsistent with applicable law. Moreover, 
section 205 allows EPA to adopt an alternative other than the least 
costly, most cost-effective or least burdensome alternative if the 
Administrator publishes with the final rule an explanation of why that 
alternative was not adopted. Before EPA establishes any regulatory 
requirements that may significantly or uniquely affect small 
governments, including tribal governments, it must have developed under 
section 203 of the UMRA a small government agency plan. The plan must 
provide for notifying potentially affected small governments, enabling 
officials of affected small governments to have meaningful and timely 
input in the development of EPA regulatory proposals with significant 
Federal intergovernmental mandates, and informing, educating, and 
advising small governments on compliance with the regulatory 
requirements.
    This proposed rule contains no Federal mandates (under the 
regulatory provisions of Title II of the UMRA) for state, local, or 
tribal governments or the private sector. The State may use these 
resulting water quality criteria in implementing its water quality 
control programs. This proposed rule does not regulate or affect any 
entity and, therefore, is not subject to the requirements of sections 
202 and 205 of UMRA.
    EPA determined that this proposed rule contains no regulatory 
requirements that might significantly or uniquely affect small 
governments. Moreover, WQS, including those proposed here, apply 
broadly to dischargers and are not uniquely applicable to small 
governments. Thus, this proposed rule is not subject to the 
requirements of section 203 of UMRA.

E. Executive Order 13132 (Federalism)

    This action does not have federalism implications. It will not have 
substantial direct effects on the states, on the relationship between 
the national government and the states, or on the distribution of power 
and responsibilities among the various levels of government, as 
specified in Executive Order 13132. EPA's authority and responsibility 
to promulgate Federal WQS when state standards do not meet the 
requirements of the CWA is well established and has been used on 
various occasions in the past. The proposed rule would not 
substantially affect the relationship between EPA and the states and 
territories, or the distribution of power or responsibilities between 
EPA and the various levels of government. The proposed rule would not 
alter Florida's considerable discretion in implementing these WQS. 
Further, this proposed rule would not

[[Page 4223]]

preclude Florida from adopting WQS that meet the requirements of the 
CWA, either before or after promulgation of the final rule, thus 
eliminating the need for Federal standards. Thus, Executive Order 13132 
does not apply to this proposed rule.
    Although section 6 of Executive Order 13132 does not apply to this 
action, EPA had extensive communication with the State of Florida to 
discuss EPA's concerns with the State's nutrient water quality criteria 
and the Federal rulemaking process. In the spirit of Executive Order 
13132, and consistent with EPA policy to promote communications between 
EPA and state and local governments, EPA specifically solicits comment 
on this proposed rule from State and local officials.

F. Executive Order 13175 (Consultation and Coordination With Indian 
Tribal Governments)

    Subject to the Executive Order 13175 (65 FR 67249, November 9, 
2000) EPA may not issue a regulation that has tribal implications, that 
imposes substantial direct compliance costs, and that is not required 
by statute, unless the Federal government provides the funds necessary 
to pay the direct compliance costs incurred by tribal governments, or 
EPA consults with tribal officials early in the process of developing 
the proposed regulation and develops a tribal summary impact statement. 
EPA has concluded that this action may have tribal implications. 
However, the rule will neither impose substantial direct compliance 
costs on tribal governments, nor preempt Tribal law.
    In the State of Florida, there are two Indian tribes, the Seminole 
Tribe of Florida and the Miccosukee Tribe of Indians of Florida, with 
lakes and flowing waters. Both tribes have been approved for treatment 
in the same manner as a state (TAS) status for CWA sections 303 and 401 
and have federally-approved WQS in their respective jurisdictions. 
These tribes are not subject to this proposed rule. However, this rule 
may impact the tribes because the numeric nutrient criteria for Florida 
will apply to waters adjacent to the tribal waters.
    EPA has contacted the tribes to inform them of the potential future 
impact this proposal could have on tribal waters. A meeting with tribal 
officials has been requested to discuss the draft proposed rule and 
potential impacts on the tribes. EPA specifically solicits additional 
comment on this proposed rule from tribal officials.

G. Executive Order 13045 (Protection of Children From Environmental 
Health and Safety Risks)

    This action is not subject to EO 13045 (62 FR 19885, April 23, 
1997) because it is not economically significant as defined in EO 
12866, and because the Agency does not believe the environmental health 
or safety risks addressed by this action present a disproportionate 
risk to children.

H. Executive Order 13211 (Actions That Significantly Affect Energy 
Supply, Distribution, or Use)

    This rule is not a ``significant energy action'' as defined in 
Executive Order 13211, ``Actions Concerning Regulations That 
Significantly Affect Energy Supply, Distribution, or Use'' (66 FR 28355 
(May 22, 2001)), because it is not likely to have a significant adverse 
effect on the supply, distribution, or use of energy.

I. National Technology Transfer Advancement Act of 1995

    Section 12(d) of the National Technology Transfer and Advancement 
Act of 1995 (``NTTAA''), Public Law 104-113, section 12(d) (15 U.S.C. 
272 note) directs EPA to use voluntary consensus standards in its 
regulatory activities unless to do so would be inconsistent with 
applicable law or otherwise impractical. Voluntary consensus standards 
are technical standards (e.g., materials specifications, test methods, 
sampling procedures, and business practices) that are developed or 
adopted by voluntary consensus standards bodies. The NTTAA directs EPA 
to provide Congress, through OMB, explanations when the Agency decides 
not to use available and applicable voluntary consensus standards.
    This proposed rulemaking does not involve technical standards. 
Therefore, EPA is not considering the use of any voluntary consensus 
standards.

J. Executive Order 12898 (Federal Actions To Address Environmental 
Justice in Minority Populations and Low-Income Populations)

    Executive Order (EO) 12898 (59 FR 7629 (Feb. 16, 1994)) establishes 
Federal executive policy on environmental justice. Its main provision 
directs Federal agencies, to the greatest extent practicable and 
permitted by law, to make environmental justice part of their mission 
by identifying and addressing, as appropriate, disproportionately high 
and adverse human health or environmental effects of their programs, 
policies, and activities on minority populations and low-income 
populations in the United States.
    EPA has determined that this proposed rule does not have 
disproportionately high and adverse human health or environmental 
effects on minority or low-income populations because it would afford a 
greater level of protection to both human health and the environment if 
these numeric nutrient criteria are promulgated for Class I and Class 
III waters in the State of Florida.

List of Subjects in 40 CFR Part 131

    Environmental protection, water quality standards, nutrients, 
Florida.

    Dated: January 14, 2010.
Lisa P. Jackson,
Administrator.
    For the reasons set out in the preamble, EPA proposes to amend 40 
CFR part 131 as follows:

PART 131--WATER QUALITY STANDARDS

    1. The authority citation for part 131 continues to read as 
follows:

    Authority:  33 U.S.C. 1251 et seq.

Subpart D--[Amended]

    2. Section 131.43 is added as follows:


Sec.  131.43  Florida.

    (a) Scope. This section promulgates numeric nutrient criteria for 
lakes, streams, springs, canals, estuaries, and coastal waters in the 
State of Florida. This section also contains provisions for site-
specific criteria.
    (b) Definitions--
    (1) Canal means a trench, the bottom of which is normally covered 
by water with the upper edges of its two sides normally above water, 
excluding all secondary and tertiary canals, classified as Class IV 
waters, wholly within Florida's agricultural areas.
    (2) Clear stream means a free-flowing water whose color is less 
than 40 platinum cobalt units (PCU).
    (3) Lake means a freshwater water body that is not a stream or 
other watercourse with some open contiguous water free from emergent 
vegetation.
    (4) Lakes and flowing waters means inland surface waters that have 
been classified as Class I (Potable Water Supplies) or Class III 
(Recreation, Propagation and Maintenance of a Healthy, Well-Balanced 
Population of Fish and Wildlife) water bodies pursuant to Rule 62-
302.400, F.A.C., excluding wetlands, and are predominantly fresh 
waters.
    (5) Nutrient watershed region means an area of the State, 
corresponding to coastal/estuarine drainage basin and differing 
geographical conditions

[[Page 4224]]

affecting nutrient levels, as delineated in the Technical Support 
Document for EPA's Proposed Rule for Numeric Nutrient Criteria for 
Florida's Inland Surface Fresh Waters.
    (6) Predominantly fresh waters means surface waters in which the 
chloride concentration at the surface is less than 1,500 milligrams per 
liter.
    (7) Spring means the point where underground water emerges onto the 
Earth's surface, including its spring run.
    (8) Spring run means a free-flowing water that originates from a 
spring or spring group whose primary (>50%) source of water is from a 
spring or spring group.
    (9) State shall mean the State of Florida, whose transactions with 
the U.S. EPA in matters related to this regulation are administered by 
the Secretary, or officials delegated such responsibility, of the 
Florida Department of Environmental Protection (FDEP), or successor 
agencies.
    (10) Stream means a free-flowing, predominantly fresh surface water 
in a defined channel, and includes rivers, creeks, branches, canals 
(outside south Florida), freshwater sloughs, and other similar water 
bodies.
    (11) Surface water means water upon the surface of the earth, 
whether contained in bounds created naturally or artificially or 
diffused. Water from natural springs shall be classified as surface 
water when it exits from the spring onto the Earth's surface.
(c) Criteria for Florida waters--
    (1) Criteria for lakes. The applicable criterion for chlorophyll a, 
total nitrogen (TN), and total phosphorus (TP) for lakes within each 
respective lake class is shown on the following table:

----------------------------------------------------------------------------------------------------------------
                                                       Baseline criteria \b\        Modified criteria  (within
Long-term average lake color and   Chlorophyll a --------------------------------        these bounds) \c\
           alkalinity              \f\ ([mu]g/L)                                 -------------------------------
                                        \a\        TP (mg/L) \a\   TN (mg/L) \a\   TP (mg/L) \a\   TN (mg/L) \a\
----------------------------------------------------------------------------------------------------------------
A                                              B               C               D               E               F
----------------------------------------------------------------------------------------------------------------
Colored Lakes > 40 PCU..........              20           0.050            1.23     0.050-0.157       1.23-2.25
Clear Lakes, Alkaline <= 40 PCU               20           0.030            1.00     0.030-0.087       1.00-1.81
 \d\ and > 50 mg/L CaCO3 \e\....
Clear Lakes, Acidic <= 40 PCU                  6           0.010           0.500     0.010-0.030     0.500-0.900
 \d\ and <= 50 mg/L CaCO3 \e\...
----------------------------------------------------------------------------------------------------------------
\a\ Concentration values are based on annual geometric mean not to be surpassed more than once in a three-year
  period. In addition, the long-term average of annual geometric mean values shall not surpass the listed
  concentration values. (Duration = annual; Frequency = not to be surpassed more than once in a three-year
  period or as a long-term average).
\b\ Baseline criteria apply unless data are readily available to calculate and apply lake-specific, modified
  criteria as described below in footnote c and the Florida Department of Environmental Protection issues a
  determination that a lake-specific modified criterion is the applicable criterion for an individual lake. Any
  such determination must be made consistent with the provisions in footnote c below. Such determination must
  also be documented in an easily accessible and publicly available location, such as an official State Web
  site.
\c\ If chlorophyll a is below the criterion in column B and there are representative data to calculate ambient-
  based, lake-specific, modified TP and TN criteria, then FDEP may calculate such criteria within these bounds
  from ambient measurements to determine lake-specific, modified criteria pursuant to CWA section 303(c).
  Modified TN and TP criteria must be based on at least three years of ambient monitoring data with (a) at least
  four measurements per year and (b) at least one measurement between May and September and one measurement
  between October and April each year. These same data requirements apply to chlorophyll a when determining
  whether the chlorophyll a criterion is met for purposes of developing modified TN and TP criteria. If the
  calculated TN and/or TP value is below the lower value, then the lower value is the lake-specific, modified
  criterion. If the calculated TN and TP value is above the upper value, then the upper value is the lake-
  specific, modified criterion. Modified TP and TN criteria may not exceed criteria applicable to streams to
  which a lake discharges. If chlorophyll a is below the criterion in column B and representative data to
  calculate modified TN and TP criteria are not available, then the baseline TN and TP criteria apply. Once
  established, modified criteria are in place as the applicable WQS for all CWA purposes.
\d\ Platinum Cobalt Units (PCU) assessed as true color free from turbidity. Long-term average color based on a
  rolling average of up to seven years using all available lake color data.
\e\ If alkalinity data are unavailable, a specific conductance of 250 micromhos/cm may be substituted.
\f\ 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.

    (2) Criteria for streams.
    (i) The applicable instream protection value (IPV) criterion for 
total nitrogen (TN) and total phosphorus (TP) for streams within each 
respective nutrient watershed region is shown in the following table:

------------------------------------------------------------------------
                                             Instream protection value
                                                     criteria
        Nutrient watershed region        -------------------------------
                                           TN (mg/L) \a\   TP (mg/L) \a\
------------------------------------------------------------------------
Panhandle \b\...........................           0.824           0.043
Bone Valley \c\.........................           1.798           0.739
Peninsula \d\...........................           1.205           0.107
North Central \e\.......................           1.479           0.359
------------------------------------------------------------------------
\a\ Concentration values are based on annual geometric mean not to be
  surpassed more than once in a three-year period. In addition, the long-
  term average of annual geometric mean values shall not surpass the
  listed concentration values. (Duration = annual; Frequency = not to be
  exceeded more than once in a three-year period or as a long-term
  average).
\b\ Panhandle region includes the following watersheds: Perdido Bay
  Watershed, Pensacola Bay Watershed, Choctawhatchee Bay Watershed, St.
  Andrew Bay Watershed, Apalachicola Bay Watershed, Apalachee Bay
  Watershed, and Econfina/Steinhatchee Coastal Drainage Area.
\c\ Bone Valley region includes the following watersheds: Tampa Bay
  Watershed, Sarasota Bay Watershed, and Charlotte Harbor Watershed.
\d\ Peninsula region includes the following watersheds: Waccasassa
  Coastal Drainage Area, Withlacoochee Coastal Drainage Area, Crystal/
  Pithlachascotee Coastal Drainage Area, Indian River Watershed,
  Caloosahatchee River Watershed, St. Lucie Watershed, Kissimmee River
  Watershed, St. John's River Watershed, Daytona/St. Augustine Coastal
  Drainage Area, Nassau Coastal Drainage Area, and St. Mary's River
  Watershed.
\e\ North Central region includes the Suwannee River Watershed.


[[Page 4225]]

    (ii) Criteria for protection of downstream lakes.
    (A) The applicable total phosphorus criterion-magnitude for a 
stream that flows into downstream lakes is the more stringent of the 
value from the preceding table in paragraph (c)(2)(i) of this section 
or a downstream lake protection value derived from the following 
equation to protect the downstream lake:
[GRAPHIC] [TIFF OMITTED] TP26JA10.003


where:

[TP]<INF>S</INF> is the total phosphorus (TP) downstream lake 
protection value, mg/L
[TP]<INF>L</INF> is applicable TP lake criterion, mg/L
c<INF>f</INF> is the fraction of inflow due to all streamflow, 0 <= 
c<INF>f</INF> <= 1
[tau]<INF>w</INF> is lake's hydraulic retention time (water volume 
divided by annual flow rate)

The term
[GRAPHIC] [TIFF OMITTED] TP26JA10.006

expresses the net phosphorus loss from the water column (e.g., via 
settling of sediment-sorbed phosphorus) as a function of the lake's 
retention time.

    (B) The preset values for c<INF>f</INF> and [tau]<INF>w</INF>, 
respectively, are 0.5 and 0.2. The State may substitute site-specific 
values for these preset values where the State determines that they are 
appropriate and documents the site-specific values in an easily 
accessible and publicly available location, such as an official State 
Web site.
    (iii) Criteria for protection of downstream estuarine waters.
    (A) The applicable criteria for a stream that flows into downstream 
estuary is the more stringent of the values from the preceding table in 
paragraph (c)(2)(i) of this section or downstream protection values 
derived from the following equation to protect the downstream estuary. 
EPA's preset DPVs are listed in the Technical Support Document (TSD) 
for Florida's Inland Waters located at www.regulations.gov, Docket ID 
No. EPA-HQ-OW-2009-0569, and calculated for each stream reach as the 
average reach-specific concentration (Ci) equal to the average reach-
specific annual loading rate (L<INF>i</INF>) divided by the average 
reach-specific flow (Qi) where:
[GRAPHIC] [TIFF OMITTED] TP26JA10.004


and where the terms are defined as follows for a specific or 
(i<SUP>th</SUP>) stream reach:

Ci maximum flow-averaged nutrient concentration for a specific (the 
i<SUP>th</SUP>) stream reach consistent with downstream use 
protection (i.e., the DPV)
k fraction of all loading to the estuary that comes from the stream 
network resolved by SPARROW
Lest protective loading rate for the estuary, from all sources
Qw combined average freshwater discharged into the estuary from the 
portion of the watershed resolved by the SPARROW stream network
Fi fraction of the flux at the downstream node of the specific 
(i<SUP>th</SUP>) reach that is transported through the stream 
network and ultimately delivered to estuarine eceiving waters (i.e. 
Fraction Delivered).
DPVs may not exceed other criteria established for designated use 
protection in this section, nor result in an exceedance of other 
criteria for other water quality parameters established pursuant to 
Rule 62-302, F.A.C.

    (B) The State may calculate alternative DPVs as above for Ci except 
that Li is determined as a series of values for each reach in the 
upstream drainage area such that the sum of reach-specific incremental 
loading rates equals the target loading rate to the downstream water 
protective of downstream uses, taking into account that downstream 
reaches must reflect loads established for upstream reaches. 
Alternative DPVs may factor in additional nutrient attenuation provided 
by already existing landscape modifications or treatment systems, such 
as constructed wetlands or stormwater treatment areas. For alternative 
DPVs to become effective for Clean Water Act purposes, the State must 
provide public notice and opportunity for comment.
    (C) To use an alternative technical approach of comparable 
scientific rigor to quantitatively determine the protective load to the 
estuary and associated protective stream concentrations, the State must 
go through the process for a Federal site-specific alternative 
criterion pursuant to paragraph (e) of this section.
    (3) Criteria for springs, spring runs, and clear streams. The 
applicable nitrate-nitrite criterion is 0.35 mg/L as an annual 
geometric mean not to be surpassed more than once in a three year 
period, nor surpassed as a long-term average of annual geometric mean 
values. In addition to this nitrate-nitrite criterion, criteria 
identified in paragraph (c)(2) of this section are applicable to clear 
streams.
    (4) Criteria for south Florida canals. The applicable criterion for 
chlorophyll a, total nitrogen (TN), and total phosphorus (TP) for 
canals within each respective canal geographic classification area is 
shown on the following table:

----------------------------------------------------------------------------------------------------------------
                                                                                       Total
                                                                   Chlorophyll a    phosphorus    Total nitrogen
                                                                   ([mu]g/L) \a\    (TP) (mg/L)     (TN) (mg/L)
                                                                                      \a\ \b\           \a\
----------------------------------------------------------------------------------------------------------------
Canals..........................................................             4.0           0.042             1.6
----------------------------------------------------------------------------------------------------------------
\a\ Concentration values are based on annual geometric mean not to be surpassed more than once in a three-year
  period. In addition, the long-term average of annual geometric mean values shall not surpass the listed
  concentration values. (Duration = annual; Frequency = not to be surpassed more than once in a three-year
  period or as a long-term average).
\b\ Applies to all canals within the Florida Department of Environmental Protection's South Florida bioregion,
  with the exception of canals within the Everglades Protection Area (EvPA) where the TP criterion of 0.010 mg/L
  currently applies.

    (5) Criteria for estuaries. [Reserved]
    (6) Criteria for coastal waters. [Reserved]
    (d) Applicability.
    (1) The criteria in paragraphs (c)(1) through (4) of this section 
apply to surface waters of the State of Florida designated as Class I 
(Potable Water Supplies) or Class III (Recreation, Propagation and 
Maintenance of a Healthy, Well-Balanced Population of Fish and 
Wildlife) water bodies pursuant to Rule 62-302.400, F.A.C., excluding 
wetlands, and apply concurrently with other applicable water quality 
criteria, except when:
    (i) State regulations contain criteria which are more stringent for 
a particular parameter and use;
    (ii) The Regional Administrator determines that site-specific 
alternative criteria apply pursuant to the procedures in paragraph (e) 
of this section;
    (iii) The State adopts and EPA approves a water quality standards 
variance to the Class I or Class III designated use pursuant to Sec.  
131.13 that meets the applicable provisions of State law and the 
applicable Federal regulations at Sec.  131.10; or

[[Page 4226]]

    (iv) The State adopts and EPA approves restoration standards 
pursuant to paragraph (g) of this section.
    (2) The criteria established in this section are subject to the 
State's general rules of applicability in the same way and to the same 
extent as are the other federally-adopted and State-adopted numeric 
criteria when applied to the same use classifications.
    (i) For all waters with mixing zone regulations or implementation 
procedures, the criteria apply at the appropriate locations within or 
at the boundary of the mixing zones; otherwise the criteria apply 
throughout the water body including at the point of discharge into the 
water body.
    (ii) The State shall use an appropriate design flow condition, 
where necessary, for purposes of permit limit derivation or load and 
wasteload allocations that is consistent with the criteria duration and 
frequency established in this section (e.g., average annual flow for a 
criterion magnitude expressed as an average annual geometric mean 
value).
    (iii) The criteria established in this section apply for purposes 
of determining the list of impaired waters pursuant to section 303(d) 
of the Clean Water Act, subject to the procedures adopted pursuant to 
Rule 62-303, F.A.C., where such procedures are consistent with the 
level of protection provided by the criteria established in this 
section.
    (e) Site-specific alternative criteria.
    (1) Upon request from the State, the Regional Administrator may 
determine that site-specific alternative criteria shall apply to 
specific surface waters in lieu of the criteria established in 
paragraph (c) of this section. Any such determination shall be made 
consistent with Sec.  131.11.
    (2) To receive consideration from the Regional Administrator for a 
determination of site-specific alternative criteria, the State must 
submit a request that includes proposed alternative numeric criteria 
and supporting rationale suitable to meet the needs for a technical 
support document pursuant to paragraph (e)(3) of this section.
    (3) For any determination made under paragraph (e)(1) of this 
section, the Regional Administrator shall, prior to making such a 
determination, provide for public notice and comment on a proposed 
determination. For any such proposed determination, the Regional 
Administrator shall prepare and make available to the public a 
technical support document addressing the specific surface waters 
affected and the justification for each proposed determination. This 
document shall be made available to the public no later than the date 
of public notice issuance.
    (4) The Regional Administrator shall maintain and make available to 
the public an updated list of determinations made pursuant to paragraph 
(e)(1) of this section as well as the technical support documents for 
each determination.
    (5) Nothing in this paragraph (e) shall limit the Administrator's 
authority to modify the criteria in paragraph (c) of this section 
through rulemaking.
    (f) Effective date. All criteria will be in effect [date 60 days 
after publication of final rule].
    (g) Restoration Water Quality Standards (WQS). The State may, at 
its discretion, adopt restoration WQS to allow attainment of a 
designated use over phased time periods where the designated use is not 
currently attainable as a result of nutrient pollution but is 
attainable in the future. In establishing restoration WQS, the State 
must:
    (1) Demonstrate that the designated use is not attainable during 
the time periods established for the restoration phases based on one of 
the factors identified in Sec.  131.10(g)(1) through (6);
    (2) Specify the designated use to be attained at the termination of 
the restoration period, as well as the criteria necessary to protect 
such use, provided that the final designated use and corresponding 
criteria shall include, at a minimum, uses and criteria that are 
consistent with CWA section 101(a)(2) ;
    (3) Establish interim restoration designated uses and water quality 
criteria, that apply during each phase that will result in maximum 
feasible progress toward the highest attainable designated use and the 
use identified in paragraph (g)(2) of this section. Such interim uses 
and criteria may not provide for further degradation of a water body 
and may be revised prior to the end of each phase in accordance with 
Sec. Sec.  131.10 and 131.20 and submitted to EPA for approval;
    (4) Establish the time periods for each restoration phase that will 
result in maximum feasible progress toward the highest attainable use 
and the designated use identified in paragraph (g)(2) of this section, 
except that the sum of such time periods shall not exceed twenty years 
from the initial date of establishment of the restoration WQS under 
this section;
    (5) Specify the spatial extent of applicability for all affected 
waters;
    (6) Meet the requirements of Sec. Sec.  131.10 and 131.20; and
    (7) Include, in its State water quality standards, a specific 
provision that if the interim restoration designated uses and criteria 
established under paragraph (g)(3) of this section are not met during 
any phased time period established under paragraph (g)(4) of this 
section, the restoration WQS will no longer be applicable and the 
designated use and criteria identified in paragraph (g)(2) of this 
section will become applicable immediately.
    (8) Provide that waters for which a restoration water quality 
standard is adopted will be recognized as impaired for the purposes of 
listing impaired waters under section 303(d) of the CWA until the use 
designated identified in paragraph (g)(2) of this section is attained.

[FR Doc. 2010-1220 Filed 1-25-10; 8:45 am]
BILLING CODE 6560-50-P


</pre><script data-cfasync="false" src="/cdn-cgi/scripts/5c5dd728/cloudflare-static/email-decode.min.js"></script></body>
</html>