Environmental Protection Agency

40 CFR Part 131

[EPA-HQ-OW-2009-0596; FRL-XXXX-X]

[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 [insert date], 60 days
after publication in the Federal Register.

ADDRESSES: Submit your comments, identified by Docket ID No.
EPA-HQ-OW-2009-0596, by one of the following methods:

  HYPERLINK "http://www.regulations.gov"  www.regulations.gov :  Follow
the on-line instructions for submitting comments.

Email<EMAIL_ADDRESS>
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.

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
HYPERLINK "http://www.regulations.gov"  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   HYPERLINK "http://www.regulations.gov"  www.regulations.gov
or e-mail.  The   HYPERLINK "http://www.regulations.gov"
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   HYPERLINK
"http://www.regulations.gov"  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   HYPERLINK
"http://www.epa.gov/epahome/dockets.htm"
http://www.epa.gov/epahome/dockets.htm .

Docket: All documents in the docket are listed in the   HYPERLINK
"http://www.regulations.gov"  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   HYPERLINK
"http://www.regulations.gov"  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<PHONE_NUMBER>, 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<PHONE_NUMBER>.

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 1:00 p.m. to 5:00 p.m. and 7:00 p.m. to 10:00 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 1:00 p.m. to 5:00 p.m. and 7:00 p.m. to 10:00 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 1:00 p.m. to 5:00 p.m.
and 7:00 p.m. to 10:00 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   HYPERLINK<EMAIL_ADDRESS><EMAIL_ADDRESS>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:<PHONE_NUMBER>; fax
number:<PHONE_NUMBER>; email address<EMAIL_ADDRESS>
SUPPLEMENTARY INFORMATION:  This supplementary information section is
organized as follows:

Table of Contents

General Information

Executive Summary

What Entities May Be Affected By This Rule?

What Should I Consider as I Prepare My Comments for EPA?

How Can I Get Copies of This Document and Other Related Information?

Background

Nutrient Pollution

Statutory and Regulatory Background

Water Quality Criteria

Agency Determination Regarding Florida

Proposed Numeric Nutrient Criteria for the State of Florida’s Lakes
and Flowing Waters

General Information

Proposed Numeric Nutrient Criteria for the State of Florida’s Lakes

Proposed Numeric Nutrient Criteria for the State of Florida’s Rivers
and Streams

Proposed Numeric Nutrient Criteria for the State of Florida’s Springs
and Clear Streams

Proposed Numeric Nutrient Criteria for South Florida Canals

Comparison Between EPA’s and Florida DEP’s Proposed Numeric Nutrient
Criteria for Florida’s Lakes and Flowing Waters

Applicability of Criteria When Final

Under What Conditions Will Federal Standards Be Either Not Finalized or
Withdrawn?

Alternative Regulatory Approaches and Implementation Mechanisms

Designating Uses

Variances

Site-specific Criteria

Compliance Schedules

Proposed Restoration Water Quality Standards (WQS) Provision

Statutory and Executive Order Reviews

Executive Order 12866:  Regulatory Planning and Review

Paperwork Reduction Act

Regulatory Flexibility Act

Unfunded Mandates Reform Act

Executive Order 13132 (Federalism)

Executive Order 13175 (Consultation and Coordination with Indian Tribal
Governments)

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

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

National Technology Transfer Advancement Act of 1995

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.  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.”

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.  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 estuaries and coastal waters
within 24 months, of the January 14, 2009 determination.

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 estuaries 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 analyses available to and conducted by the Agency
to date indicate that numeric nutrient water quality criteria for
estuaries 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 estuaries 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
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:

Category	Examples of potentially 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
HYPERLINK "http://www.regulations.gov"  http://www.regulations.gov  or
e-mail.  Clearly mark the part or all of the information that you claim
to be CBI.  For CBI information in a disk or CD-ROM that you mail to
EPA, mark the outside of the disk or CD-ROM as CBI and then identify
electronically within the disk or CD-ROM the specific information that
is claimed as CBI.  In addition to one complete version of the comment
that includes information claimed as CBI, a copy of the comment that
does not contain the information claimed as CBI must be submitted for
inclusion in the public docket.  Information so marked will not be
disclosed except in accordance with procedures set forth in 40 CFR part
2.

    2. Tips for Preparing Your Comments. When submitting comments,
remember to:

Identify the rulemaking by docket number and other identifying
information (subject heading, Federal Register date, and page number).

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.

Explain why you agree or disagree; suggest alternatives and substitute
language for your requested changes.

Describe any assumptions and provide any technical information and/or
data that you used.

If you estimate potential costs or burdens, explain how you arrived at
your estimate in sufficient detail to allow for it to be reproduced.

Provide specific examples to illustrate your concerns, and suggest
alternatives.

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<PHONE_NUMBER>.  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   HYPERLINK "http://www.epa.gov/fedrgstr/"
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   HYPERLINK "http://www.regulations.gov"
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   HYPERLINK
"http://www.epa.gov/epahome/dockets.htm"
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) 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.  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.,   Nutrient problems can manifest locally or much further
downstream in lakes, reservoirs, and estuaries.

	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.

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
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.  Algae can also damage or clog the
gills of fish and invertebrates.

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.  More than 50% of unusual marine
mortality events may be associated with HABs.  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.,

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.  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.

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.  A recent study showed that at least
one type of cyanobacteria has been linked to cancer and tumor growth in
animals.

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.,   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.  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.  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.

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.

onitoring of Florida Public Water Supplies from 2004-2007 indicates that
violations of nitrate maximum contaminant levels (MCL) ranged from 34-40
violations annually.  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.  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 system problems.,  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.
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.  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.

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.  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.

	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, 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.  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.

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.
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.  Exchanges of surface water and ground water
contribute to complex relationships between nutrient sources and the
location and timing of eventual impacts.

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.  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.

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 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 as 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,
rivers and streams, and estuaries and coastal marine waters.  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.

	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 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:    HYPERLINK
"http://www.epa.gov/waterscience/standards/rules/fl-determination.htm"
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 estuaries
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 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 located at
HYPERLINK "http://www.regulations.gov"  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 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.  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.

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.):

A	B	C	D	E	F

Long Term Average Lake Color and Alkalinity	Chlorophyll a f  (g/L) a
Baseline Criteria b	Modified Criteria

 (within these bounds) c

TP (mg/L) a	TN (mg/L) a	TP (mg/L) a	TN (mg/L) a

Colored Lakes

> 40 PCU	20 	0.050	1.23	0.050-0.157	1.23-2.25

Clear Lakes, Alkaline

≤ 40 PCU d and > 50 mg/L CaCO3 e	20	0.030	1.00	0.030-0.087	1.00-1.81

Clear Lakes, Acidic

≤ 40 PCU d and ≤ 50 mg/L CaCO3 e	6	0.010	0.500	0.010-0.030
0.500-0.900

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.
EPA 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.  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.

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 (CaCO3), and 3) Clear
Lakes ≤ 40 PCU with alkalinity ≤ 50 mg/L CaCO3.

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.  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.

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 (CaCO3),
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
CaCO3) 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 CaCO3 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 CaCO3 is an appropriate distinguishing characteristic in
clear lakes in Florida because lakes with alkalinity ≤50 CaCO3
represents 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 CaCO3) or alkaline (>50 mg/L
alkalinity as CaCO3).

 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
(S/cm) as a substitute for the threshold of 50 mg/L alkalinity as
CaCO3.  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 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) 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 established, scientific
classification system to describe current status and natural
expectations for lake conditions with respect to nutrients and algal
productivity.  EPA’s review of TSI studies, 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 (µg/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 µg/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
µg/L).  EPA requests comment on these conclusions regarding
oligotrophic and mesotrophic status expectations for these categories of
Florida lakes.

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 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).

In addition to this evidence, EPA used information from the application
of a Morphoedaphic Index (MEI) model 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:

(i) Colored Lakes:  EPA proposes a chlorophyll a criterion of 20 µg/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 µg/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 µg/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
µg/L and the MEI model predicted reference chlorophyll a concentrations
of 1-25 µg/L for a set of colored lakes in Florida.  The model also
predicted that concentrations of chlorophyll a ranging from 15-36 µg/L
in individual lakes would result in a 10% loss of transparency (all but
two lakes were above 20 µg/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
µg/L chlorophyll a and the clear majority (nine of eleven) of lakes had
predicted 10% transparency loss above 20 µg/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 µg/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 µg/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
µg/L.  Similar to the results for colored lakes, half of the clear,
alkaline lakes had predicted natural or referenced conditions at or
below 20 µg/L chlorophyll a and all but one clear, alkaline lake had
predicted 10% transparency loss above 20 µg/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 µg/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 with chlorophyll
a levels of less than 2 µg/L.  As discussed above, warm water TSI
studies suggest a chlorophyll a level of approximately 7 µg/L at the
oligotrophic-mesotrophic boundary.

In July 2009, FDEP proposed a chlorophyll a criterion for clear, acidic
lakes of 9 μg/L.   In comments sent to EPA via email in October 2009,
FDEP reported that the Nutrient TAC suggested in June 2009 that
maintaining chlorophyll a below 10 μg/L in clear, acidic lakes would be
protective of the designated use, because a value of <10 μg/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 μg/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 µg/L as supporting evidence
for a chlorophyll a criterion of 9 ug/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 µg/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 µg/L (with seven of the
eight values below 5 µg/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 µg/L (with five of the eight values
below 7 µg/L).  All but one of the clear, acid lakes had predicted
natural or reference conditions below 6 µg/L chlorophyll a and the
majority (six of eight) of clear, alkaline lakes had predicted 10%
transparency loss above 6 µg/L chlorophyll a.  Given available
information on reference condition and predicted effect levels, EPA
adjusted the approximate oligotrophic-mesotrophic boundary value of 7
µg/L slightly downward to 6 µg/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 µg/L.

PA 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 µg/L for colored lakes and clear alkaline lakes
and 6 µg/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 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.

PA 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, 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.

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
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.  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.

) 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.  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.

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.

PA 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.

(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
CaCO3.  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 µg/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 µg/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.  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 µg/L.
EPA believes the scientific basis for a 9 ug/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 µg/L and
the second category (clear, acidic non-sandhill lakes) a chlorophyll a
criterion of 9 µg/L.

PA also notes, as discussed previously, that FDEP recommended a
criterion of 9 µg/L as being protective of all clear acidic lakes,
including sandhill lakes and that the Nutrient Criteria TAC supported
“less than 10 µg/L” as protective.  EPA also requests comment on 9
µg/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 µg/L, 1.5
mg/L and 0.09 mg/L for colored lakes; 48 µg/L, 1.8 mg/L and 0.05 mg/L
for clear, alkaline lakes; and 15 µg/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 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.).

Nutrient Watershed Region	Instream Protection Value Criteria

	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 include
both causal (e.g., TN and TP) and response variables (e.g., chlorophyll
a and some measure of clarity) for water bodies.  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.

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, 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