4174 Federal Register / Vol. 75, No. 16 / Tuesday, January 26, 2010 / Proposed Rules 

ENVIRONMENTAL PROTECTION 

AGENCY 

40 CFR Part 131 

[EPA–HQ–OW–2009–0596; FRL–9105–1] 

RIN 2040–AF11 

Water Quality Standards for the State 

of Florida’s Lakes and Flowing Waters 

AGENCY: Environmental Protection 

Agency (EPA). 

ACTION: Proposed rule. 

SUMMARY: The Environmental Protection 

Agency (EPA) is proposing numeric 

nutrient water quality criteria to protect 

aquatic life in lakes and flowing waters, 

including canals, within the State of 

Florida and proposing regulations to 

establish a framework for Florida to 

develop ‘‘restoration standards’’ for 

impaired waters. On January 14, 2009, 

EPA made a determination under 

section 303(c)(4)(B) of the Clean Water 

Act (‘‘CWA’’ or ‘‘the Act’’) that numeric 

nutrient water quality criteria for lakes 

and flowing waters and for estuaries and 

coastal waters are necessary for the State 

of Florida to meet the requirements of 

CWA section 303(c). Section 303(c)(4) of 

the CWA requires the Administrator to 

promptly prepare and publish proposed 

regulations setting forth new or revised 

water quality standards (‘‘WQS’’ or 

‘‘standards’’) when the Administrator, or 

an authorized delegate of the 

Administrator, determines that such 

new or revised WQS are necessary to 

meet requirements of the Act. This 

proposed rule fulfills EPA’s obligation 

under section 303(c)(4) of the CWA to 

promptly propose criteria for Florida’s 

lakes and flowing waters. 

DATES: Comments must be received on 

or before March 29, 2010. 

ADDRESSES: Submit your comments, 

identified by Docket ID No. EPA–HQ– 

OW–2009–0596, by one of the following 

methods: 

1. www.regulations.gov: Follow the 

online instructions for submitting 

comments. 

2. E-mail: ow-docket@epa.gov. 

3. Mail to: Water Docket, U.S. 

Environmental Protection Agency, Mail 

Code: 2822T, 1200 Pennsylvania 

Avenue, NW., Washington, DC 20460, 

Attention: Docket ID No. EPA–HQ–OW– 

2009–0596. 

4. Hand Delivery: EPA Docket Center, 

EPA West Room 3334, 1301 

Constitution Avenue, NW., Washington, 

DC 20004, Attention: Docket ID No. 

EPA–HQ–OW–2009–0596. Such 

deliveries are only accepted during the 

Docket’s normal hours of operation, and 

special arrangements should be made 

for deliveries of boxed information. 

Instructions: Direct your comments to 

Docket ID No. EPA–HQ–OW–2009– 

0596. EPA’s policy is that all comments 

received will be included in the public 

docket without change and may be 

made available online at 

www.regulations.gov, including any 

personal information provided, unless 

the comment includes information 

claimed to be Confidential Business 

Information (CBI) or other information 

whose disclosure is restricted by statute. 

Do not submit information that you 

consider to be CBI or otherwise 

protected through www.regulations.gov 

or e-mail. The www.regulations.gov Web 

site is an ‘‘anonymous access’’ system, 

which means EPA will not know your 

identity or contact information unless 

you provide it in the body of your 

comment. If you send an e-mail 

comment directly to EPA without going 

through www.regulations.gov your email address will be automatically 

captured and included as part of the 

comment that is placed in the public 

docket and made available on the 

Internet. If you submit an electronic 

comment, EPA recommends that you 

include your name and other contact 

information in the body of your 

comment and with any disk or CD–ROM 

you submit. If EPA cannot read your 

comment due to technical difficulties 

and cannot contact you for clarification, 

EPA may not be able to consider your 

comment. Electronic files should avoid 

the use of special characters, any form 

of encryption, and be free of any defects 

or viruses. For additional information 

about EPA’s public docket visit the EPA 

Docket Center homepage at http:// 

www.epa.gov/epahome/dockets.htm. 

Docket: All documents in the docket 

are listed in the www.regulations.gov 

index. Although listed in the index, 

some information is not publicly 

available, e.g., CBI or other information 

whose disclosure is restricted by statute. 

Certain other material, such as 

copyrighted material, will be publicly 

available only in hard copy. Publicly 

available docket materials are available 

either electronically in 

www.regulations.gov or in hard copy at 

a docket facility. The Office of Water 

(OW) Docket Center is open from 8:30 

until 4:30 p.m., Monday through Friday, 

excluding legal holidays. The OW 

Docket Center telephone number is 

(202) 566–2426, and the Docket address 

is OW Docket, EPA West, Room 3334, 

1301 Constitution Avenue, NW., 

Washington, DC 20004. The Public 

Reading Room is open from 8:30 a.m. to 

4:30 p.m., Monday through Friday, 

excluding legal holidays. The telephone 

number for the Public Reading Room is 

(202) 566–1744. 

Public hearings will be held in the 

following cities in Florida: Tallahassee, 

Orlando, and West Palm Beach. The 

public hearing in Tallahassee is 

scheduled for Tuesday, February 16, 

2010 and will be held from 1 p.m. to 5 

p.m. and 7 p.m. to 10 p.m. at the 

Holiday Inn Capitol East, 1355 

Apalachee Parkway, Tallahassee, FL 

32301. The public hearing in Orlando is 

scheduled for Wednesday, February 17, 

2010 and will be held from 1 p.m. to 5 

p.m. and 7 p.m. to 10 p.m. at the 

Crowne Plaza Orlando Universal, 7800 

Universal Boulevard, Orlando, FL 

32819. The public hearing in West Palm 

Beach is scheduled for Thursday, 

February 18, 2010 and will be held from 

1 p.m. to 5 p.m. and 7 p.m. to 10 p.m. 

at the Holiday Inn Palm Beach Airport, 

1301 Belvedere Road, West Palm Beach, 

FL 33405. If you need a sign language 

interpreter at any of these hearings, you 

should contact Sharon Frey at 202–566– 

1480 or frey.sharon@epa.gov at least ten 

business days prior to the meetings so 

that appropriate arrangements can be 

made. For further information, 

including registration information, 

please refer to the following Web site: 

http://www.epa.gov/waterscience/ 

standards/rules/florida/. 

FOR FURTHER INFORMATION CONTACT: 

Danielle Salvaterra, U.S. EPA 

Headquarters, Office of Water, 

Mailcode: 4305T, 1200 Pennsylvania 

Avenue, NW., Washington, DC 20460; 

telephone number: 202–564–1649; fax 

number: 202–566–9981; e-mail address: 

salvaterra.danielle@epa.gov. 

SUPPLEMENTARY INFORMATION: This 

supplementary information section is 

organized as follows: 

Table of Contents 

I. General Information 

A. Executive Summary 

B. What Entities May Be Affected by This 

Rule? 

C. What Should I Consider as I Prepare My 

Comments for EPA? 

D. How Can I Get Copies of This Document 

and Other Related Information? 

II. Background 

A. Nutrient Pollution 

B. Statutory and Regulatory Background 

C. Water Quality Criteria 

D. Agency Determination Regarding 

Florida 

III. Proposed Numeric Nutrient Criteria for 

the State of Florida’s Lakes and Flowing 

Waters 

A. General Information 

B. Proposed Numeric Nutrient Criteria for 

the State of Florida’s Lakes 

C. Proposed Numeric Nutrient Criteria for 

the State of Florida’s Rivers and Streams 

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1Florida Department of Environmental 

Protection. 2008. Integrated Water Quality 

Assessment for Florida: 2008 305(b) Report and 

303(d) List Update, p. 67. 

2http://www.census.gov/population/projections/ 

SummaryTabA1.pdf. 

D. Proposed Numeric Nutrient Criteria for 

the State of Florida’s Springs and Clear 

Streams 

E. Proposed Numeric Nutrient Criteria for 

South Florida Canals 

F. Comparison Between EPA’s and Florida 

DEP’s Proposed Numeric Nutrient 

Criteria for Florida’s Lakes and Flowing 

Waters 

G. Applicability of Criteria When Final 

IV. Under What Conditions Will Federal 

Standards Be Either Not Finalized or 

Withdrawn? 

V. Alternative Regulatory Approaches and 

Implementation Mechanisms 

A. Designating Uses 

B. Variances 

C. Site-Specific Criteria 

D. Compliance Schedules 

VI. Proposed Restoration Water Quality 

Standards (WQS) Provision 

VII. Statutory and Executive Order Reviews 

A. Executive Order 12866: Regulatory 

Planning and Review 

B. Paperwork Reduction Act 

C. Regulatory Flexibility Act 

D. Unfunded Mandates Reform Act 

E. Executive Order 13132 (Federalism) 

F. Executive Order 13175 (Consultation 

and Coordination With Indian Tribal 

Governments) 

G. Executive Order 13045 (Protection of 

Children From Environmental Health 

and Safety Risks) 

H. Executive Order 13211 (Actions That 

Significantly Affect Energy Supply, 

Distribution, or Use) 

I. National Technology Transfer 

Advancement Act of 1995 

J. Executive Order 12898 (Federal Actions 

To Address Environmental Justice in 

Minority Populations and Low-Income 

Populations) 

I. General Information 

A. Executive Summary 

Excess loadings of nitrogen and 

phosphorus, commonly referred to as 

nutrient pollution, are one of the most 

prevalent causes of water quality 

impairment in the United States. 

Anthropogenic nitrogen and 

phosphorus over-enrichment in many of 

the Nation’s waters is a widespread, 

persistent, and growing problem. 

Nutrient pollution can significantly 

impact aquatic life and long-term 

ecosystem health, diversity, and 

balance. More specifically, high 

nitrogen and phosphorus loadings, or 

nutrient pollution, result in harmful 

algal blooms (HABs), reduced spawning 

grounds and nursery habitats, fish kills, 

and oxygen-starved hypoxic or ‘‘dead’’ 

zones. Public health concerns related to 

nutrient pollution include impaired 

drinking water sources, increased 

exposure to toxic microbes such as 

cyanobacteria, and possible formation of 

disinfection byproducts in drinking 

water, some of which have been 

associated with serious human illnesses 

such as bladder cancer. Nutrient 

problems can exhibit themselves locally 

or much further downstream leading to 

degraded lakes, reservoirs, and 

estuaries, and to hypoxic zones where 

fish and aquatic life can no longer 

survive. 

In the State of Florida, nutrient 

pollution has contributed to severe 

water quality degradation. Based upon 

waters assessed and reported in the 

2008 Integrated Water Quality 

Assessment for Florida, approximately 

1,000 miles of rivers and streams, 

350,000 acres of lakes, and 900 square 

miles of estuaries are known to be 

impaired for nutrients by the State.1 The 

actual number of stream miles, lake 

acres, and estuarine square miles of 

waters impaired for nutrients in Florida 

may be higher, as many waters currently 

are classified as ‘‘unassessed.’’ 

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 sitespecific total maximum daily loads 

(TMDLs). 

Despite FDEP’s intensive efforts to 

diagnose and control nutrient pollution, 

substantial water quality degradation 

from nutrient over-enrichment remains 

a significant problem. On January 14, 

2009, EPA determined under CWA 

section 303(c)(4)(B) that new or revised 

WQS in the form of numeric nutrient 

water quality criteria are necessary to 

meet the requirements of the CWA in 

the State of Florida. The Agency 

considered (1) the State’s documented 

unique and threatened ecosystems, (2) 

the high number of impaired waters due 

to existing nutrient pollution, and (3) 

the challenge associated with growing 

nutrient pollution resulting from 

expanding urbanization, continued 

agricultural development, and a 

significantly increasing population that 

is expected to grow 75% between 2000 

to 2030.2 EPA also reviewed the State’s 

regulatory nutrient accountability 

system, which represents an impressive 

synthesis of technology-based 

standards, point source control 

authority, and authority to establish 

enforceable controls for nonpoint source 

activities. However, the significant 

challenge faced by the water quality 

components of this system is its 

dependence upon an approach 

involving resource-intensive and timeconsuming site-specific data collection 

and analysis to interpret non-numeric 

narrative nutrient criteria. EPA 

determined that Florida’s reliance on a 

case-by-case interpretation of its 

narrative nutrient criterion in 

implementing an otherwise 

comprehensive water quality framework 

of enforceable accountability was 

insufficient to ensure protection of 

applicable designated uses. As part of 

the Agency’s determination, EPA 

indicated that it expected to propose 

numeric nutrient criteria for lakes and 

flowing waters within 12 months, and 

for estuarine and coastal waters within 

24 months, of the January 14, 2009 

determination. 

On August 19, 2009, EPA entered into 

a phased Consent Decree with Florida 

Wildlife Federation, Sierra Club, 

Conservancy of Southwest Florida, 

Environmental Confederation of 

Southwest Florida, and St. Johns 

Riverkeeper, committing to sign a 

proposed rule setting forth numeric 

nutrient criteria for lakes and flowing 

waters in Florida by January 14, 2010, 

and for Florida’s estuarine and coastal 

waters by January 14, 2011, unless 

Florida submits and EPA approves State 

numeric nutrient criteria before EPA’s 

proposal. The phased Consent Decree 

also provides that EPA issue a final rule 

by October 15, 2010 for lakes and 

flowing water, and by October 15, 2011 

for estuarine and coastal waters, unless 

Florida submits and EPA approves State 

numeric nutrient criteria before a final 

EPA action. 

Accordingly, this proposal is part of a 

phased rulemaking process in which 

EPA will propose and take final action 

in 2010 on numeric nutrient criteria for 

lakes and flowing waters and for 

estuarine and coastal waters in 2011. 

The two phases of this rulemaking are 

linked because nutrient pollution in 

Florida’s rivers and streams affects not 

only instream aquatic conditions but 

also downstream estuarine and coastal 

waters ecosystem conditions. The 

Agency could have waited to propose 

estuarine and coastal downstream 

protection criteria values for rivers and 

streams as part of the second phase of 

this rulemaking process. However, the 

substantial data, peer-reviewed 

methodologies, and extensive scientific 

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4176 Federal Register / Vol. 75, No. 16 / Tuesday, January 26, 2010 / Proposed Rules 

analyses available to and conducted by 

the Agency to date indicate that 

numeric nutrient water quality criteria 

for estuarine and coastal waters, when 

proposed and finalized in 2011, may 

result in the need for more stringent 

rivers and streams criteria to ensure 

protection of downstream water quality, 

particularly for the nitrogen component 

of nutrient pollution. Therefore, 

considering the numerous requests for 

the Agency to share its analysis and 

scientific and technical conclusions at 

the earliest possible opportunity to 

allow for full review and comment, EPA 

is including downstream protection 

values for total nitrogen (TN) as 

proposed criteria for rivers and streams 

to protect the State’s estuaries and 

coastal waters in this notice. 

As described in more detail below 

and in the technical support document 

accompanying this notice, these 

proposed nitrogen downstream 

protection values are based on 

substantial data, thorough scientific 

analysis, and extensive technical 

evaluation. However, EPA recognizes 

that additional data and analysis may be 

available, including data for particular 

estuaries, to help inform what numeric 

nutrient criteria are necessary to protect 

Florida’s waters, including downstream 

lakes and estuaries. EPA also recognizes 

that substantial site-specific work has 

been completed for a number of these 

estuaries. This notice and the proposed 

downstream protection values are not 

intended to address or be interpreted as 

calling into question the utility and 

protectiveness of these site-specific 

analyses. Rather, the proposed values 

represent the output of a systematic and 

scientific approach that was developed 

to be generally applicable to all flowing 

waters in Florida that terminate in 

estuaries for the purpose of ensuring the 

protection of downstream estuaries. 

EPA is interested in obtaining feedback 

at this time on this systematic and 

scientific approach. EPA is also 

interested in feedback regarding sitespecific analyses for particular estuaries 

that should be used instead of this 

general approach for establishing final 

values. The Agency further recognizes 

that the proposed values in this notice 

will need to be considered in the 

context of the Agency’s numeric 

nutrient criteria for estuarine and 

coastal waters scheduled for proposal in 

January of 2011. 

Regarding the criteria for flowing 

waters for protection of downstream 

lakes and estuaries, at this time, EPA 

intends to take final action on the 

criteria for protection of downstream 

lakes as part of the first phase of this 

rulemaking (by October 15, 2010) and to 

finalize downstream protection values 

in flowing waters as part of the second 

phase of this rulemaking process (by 

October 15, 2011) in coordination with 

the proposal and finalization of numeric 

nutrient criteria for estuarine and 

coastal waters in 2011. However, if 

comments, data and analyses submitted 

as a result of this proposal support 

finalizing these values sooner, by 

October 2010, EPA may choose to 

proceed in this manner. To facilitate 

this process, EPA requests comments 

and welcomes thorough evaluation on 

the technical and scientific basis of 

these proposed downstream protection 

values, as well as information on 

estuaries where site-specific analyses 

should be used, as part of the broader 

comment and evaluation process that 

this proposal initiates. 

In accordance with the terms of EPA’s 

January 14, 2009 determination and the 

Consent Decree, EPA is proposing 

numeric nutrient criteria for Florida’s 

lakes and flowing waters which include 

the following four water body types: 

Lakes, streams, springs and clear 

streams, and canals in south Florida. In 

developing this proposal, EPA worked 

closely with FDEP staff to review and 

analyze the State’s extensive dataset of 

nutrient-related measurements as well 

as its analysis of stressor-response 

relationships and benchmark or 

modified-reference conditions. EPA also 

conducted further analyses and 

modeling, in addition to requesting an 

independent external peer review of the 

core methodologies and approaches that 

support this proposal. 

For lakes, EPA is proposing a 

classification scheme using color and 

alkalinity based upon substantial data 

that show that lake color and alkalinity 

play an important role in the degree to 

which TN and total phosphorus (TP) 

concentrations result in a biological 

response such as elevated chlorophyll a 

levels. EPA found that correlations 

between nutrients and biological 

response parameters in the different 

types of lakes in Florida were 

sufficiently robust, combined with 

additional lines of evidence, to support 

stressor-response criteria development 

for Florida’s lakes. The Agency is also 

proposing an accompanying 

supplementary analytical approach that 

the State can use to adjust TN and TP 

criteria for a particular lake within a 

certain range where sufficient data on 

long-term ambient TN and TP levels are 

available to demonstrate that protective 

chlorophyll a criteria for a specific lake 

will still be maintained and attainment 

of the designated use will be assured. 

This information is presented in more 

detail in Section III.B below. 

Regarding numeric nutrient criteria 

for streams and rivers, EPA considered 

the extensive work of FDEP to analyze 

the relationship between TN and TP 

levels and biological response in 

streams and rivers. EPA found that 

relationships between nutrients and 

biological response parameters in rivers 

and streams were affected by many 

factors that made derivation of a 

quantitative relationship between 

chlorophyll a levels and nutrients in 

streams and rivers difficult to establish 

in the same manner as EPA did for lakes 

(i.e., stressor-response relationship). 

EPA considered an alternative 

methodology that evaluated a 

combination of biological information 

and data on the distribution of nutrients 

in a substantial number of healthy 

stream systems. Based upon a technical 

evaluation of the significant available 

data on Florida streams and related 

scientific analysis, the Agency 

concluded that reliance on a statistical 

distribution methodology was a stronger 

and a more sound approach for deriving 

TN and TP criteria in streams and 

rivers. This information is presented in 

more detail in Section III.C below. 

In developing these proposed numeric 

nutrient criteria for rivers and streams, 

EPA also evaluated their effectiveness 

for assuring the protection of 

downstream lake and estuary designated 

uses pursuant to the provisions of 40 

CFR 130.10(b), which requires that WQS 

must provide for the attainment and 

maintenance of the WQS of downstream 

waters. For rivers and streams in 

Florida, EPA must ensure, to the extent 

that available science allows, that its 

nutrient criteria take into account the 

impact of near-field nutrient loads on 

aquatic life in downstream lakes and 

estuaries. EPA currently has evaluated 

the protectiveness of its rivers and 

streams TP criteria for lake protection 

and also the protectiveness of its rivers 

and streams TN criteria for 16 out of 26 

of Florida’s downstream estuaries using 

scientifically sound approaches for both 

estimating protective loads and deriving 

concentration-based upstream values. 

Of the ten downstream estuaries not 

completely evaluated to date, seven are 

in south Florida and receive TN loads 

from highly managed canals and 

waterways and three are in low lying 

areas of central Florida. 

As noted above, EPA used best 

available science and data related to 

downstream waters and found that there 

are cases where the nutrient criteria 

EPA is proposing to protect instream 

aquatic life may not be stringent enough 

to ensure protection of aquatic life in 

certain downstream lakes and estuaries. 

Accordingly, EPA is also proposing an 

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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 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 

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4178 Federal Register / Vol. 75, No. 16 / Tuesday, January 26, 2010 / Proposed Rules 

3To be used by living organisms, nitrogen gas 

must be fixed into its reactive forms; for plants, 

either nitrate or ammonia. 

4Eutrophication is defined as an increase in 

organic carbon to an aquatic ecosystem caused by 

primary productivity stimulated by excess 

nutrients—typically compounds containing 

nitrogen or phosphorus. Eutrophication can 

adversely affect aquatic life, recreation, and human 

health uses of waters. 

5 Villanueva, C.M. et al., 2006. Bladder Cancer 

and Exposure to Water Disinfection By-Products 

through Ingestion, Bathing, Showering, and 

Swimming in Pools. American Journal of 

Epidemiology, 165(2):148–156. 

6U.S. EPA. 2009. What Is in Our Drinking Water. 

United States Environmental Protection Agency, 

Office of Research and Development. http:// 

www.epa.gov/extrmurl/research/process/ 

drinkingwater.html. Accessed December 2009. 

7National Research Council, 2000. Clean Coastal 

Waters: Understanding and Reducing the Effects of 

Nutrient Pollution. Report prepared by the Ocean 

Study Board and Water Science and Technology 

Board, Commission on Geosciences, Environment 

and Resources, National Resource Council. National 

Academy Press, Washington, DC; Howarth, R.W., A. 

Sharpley, and D. Walker. 2002. Sources of nutrient 

pollution to coastal waters in the United States: 

Implications for achieving coastal water quality 

goals. Estuaries. 25(4b):656–676; Smith, V.H. 2003. 

Eutrophication of freshwater and coastal marine 

ecosystems. Environ. Sci. and Poll. Res. 10(2):126– 

139; Dodds, W.K., W.W. Bouska, J.L. Eitzmann, T.J. 

Pilger, K.L. Pitts, A.J. Riley, J.T. Schloesser, and D.J. 

Thornbrugh. 2009. Eutrophication of U.S. 

freshwaters: Analysis of potential economic 

damages. Environ. Sci. Tech.. 43(1):12–19. 

you mail to EPA, mark the outside of the 

disk or CD–ROM as CBI and then 

identify electronically within the disk or 

CD–ROM the specific information that 

is claimed as CBI. In addition to one 

complete version of the comment that 

includes information claimed as CBI, a 

copy of the comment that does not 

contain the information claimed as CBI 

must be submitted for inclusion in the 

public docket. Information so marked 

will not be disclosed except in 

accordance with procedures set forth in 

40 CFR part 2. 

2. Tips for Preparing Your Comments. 

When submitting comments, remember 

to: 

1. Identify the rulemaking by docket 

number and other identifying 

information (subject heading, Federal 

Register date, and page number). 

2. Follow directions—The agency may 

ask you to respond to specific questions 

or organize comments by referencing a 

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or section number. 

3. Explain why you agree or disagree; 

suggest alternatives and substitute 

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5. If you estimate potential costs or 

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7. Make sure to submit your 

comments by the comment period 

deadline identified. 

D. How Can I Get Copies of This 

Document and Other Related 

Information? 

1. Docket. EPA has established an 

official public docket for this action 

under Docket Id. No. EPA–HQ–OW– 

2009–0596. The official public docket 

consists of the document specifically 

referenced in this action, any public 

comments received, and other 

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Although a part of the official docket, 

the public docket does not include CBI 

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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., 

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Facility is open from 8:30 a.m. to 4:30 

p.m., Monday through Friday, excluding 

legal holidays. The Docket telephone 

number is 202–566–1744. A reasonable 

fee will be charged for copies. 

2. Electronic Access. You may access 

this Federal Register document 

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under the ‘‘Federal Register’’ listings at 

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An electronic version of the public 

docket is available through EPA’s 

electronic public docket and comment 

system, EPA Dockets. You may use EPA 

Dockets at http://www.regulations.gov to 

view public comments, access the index 

listing of the contents of the official 

public docket, and to access those 

documents in the public docket that are 

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visit the EPA Docket Center homepage 

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dockets.htm. Although not all docket 

materials may be available 

electronically, you may still access any 

of the publicly available docket 

materials through the Docket Facility 

identified in Section I.D(1). 

II. Background 

A. Nutrient Pollution 

1. What Is Nutrient Pollution? 

Excess anthropogenic concentrations 

of nitrogen (typically in oxidized, 

inorganic forms, such as nitrate) 3 and 

phosphorus (typically as phosphate), 

commonly referred to as nutrient 

pollution, in surface waters can result in 

excessive algal and aquatic plant 

growth, referred to as eutrophication.4

One impact associated with 

eutrophication is low dissolved oxygen, 

due to decomposition of the aquatic 

plants and algae when these plants and 

algae die. As noted above, high nitrogen 

and phosphorus loadings also result in 

HABs, reduced spawning grounds and 

nursery habitats for aquatic life, and fish 

kills. Public health concerns related to 

eutrophication include impaired 

drinking water sources, increased 

exposure to toxic microbes such as 

cyanobacteria, and possible formation of 

disinfection byproducts in drinking 

water, some of which have been 

associated with serious human illnesses 

such as bladder cancer.5 6 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.7

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 

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8Hauxwell, J. C. Jacoby, T. Frazer, and J. Stevely. 

2001. Nutrients and Florida’s Coastal Waters. 

Florida Sea Grant. 

9NOAA. 2009. Harmful Algal Blooms: Current 

Programs Overview. National Oceanic and 

Atmospheric Administration. http:// 

www.cop.noaa.gov/stressors/extremeevents/hab/ 

welcome.html. Accessed December 2009. 

10NOAA. 2009. Harmful Algal Blooms: Current 

Programs Overview. National Oceanic and 

Atmospheric Administration. http:// 

www.cop.noaa.gov/stressors/extremeevents/hab/ 

welcome.html. Accessed December 2009. 

11WHOI. 2008. HAB Impacts on Wildlife. Woods 

Hole Oceanographic Institution. http:// 

www.whoi.edu/redtide/page.do?pid=9682. 

Accessed December 2009. 

12WHOI. 2008. Marine Mammals. Woods Hole 

Oceanographic Institution. http://www.whoi.edu/ 

redtide/page.do?pid=14215. Accessed December 

2009. 

13WHOI. 2008. HAB Impacts on Wildlife. Woods 

Hole Oceanographic Institution. http:// 

www.whoi.edu/redtide/page.do?pid=9682. 

Accessed December 2009. 

14WHOI. 2008. Marine Mammals. Woods Hole 

Oceanographic Institution. http://www.whoi.edu/ 

redtide/page.do?pid=14215. Accessed December 

2009. 

15WHOI. 2008. Marine Mammals. Woods Hole 

Oceanographic Institution. http://www.whoi.edu/ 

redtide/page.do?pid=14215. Accessed December 

2009. 

16WHOI. 2008. HAB Impacts on Wildlife. Woods 

Hole Oceanographic Institution. http:// 

www.whoi.edu/redtide/page.do?pid=9682. 

Accessed December 2009. 17Falconer, I.R., A.R. Humpage. 2005. Health 

Risk Assessment of Cyanobacterial (Blue-green 

Algal) Toxins in Drinking Water. Int. J. Environ. 

Res. Public Health. 2(1): 43–50. 18NOAA. 2009. Harmful Algal Blooms: Current 

Programs Overview. National Oceanic and 

Atmospheric Administration. http:// 

www.cop.noaa.gov/stressors/extremeevents/hab/ 

welcome.html. Accessed December 2009. 

19USGS. 2009. Hypoxia. U.S. Geological Survey. 

http://toxics.usgs.gov/definitions/hypoxia.html. 

Accessed December 2009. 

20ESA. 2009. Hypoxia. Ecological Society of 

America. http://www.esa.org/education_diversity/ 

pdfDocs/hypoxia.pdf. Accessed December 2009. 

21USEPA. 2000. Ambient Aquatic Life Water 

Quality Criteria for Dissolved Oxygen (Saltwater): 

Cape Cod to Cape Hattaras. Environmental 

Protection Agency, Office of Water, Washington DC 

PA–822–R–00–012. 

22Ecological Society of America. 2009. Hypoxia. 

Ecological Society of America, Washington, DC. 

http://www.esa.org/education/edupdfs/ 

hypoxia.pdf. Accessed December 2009. 

23USEPA. 2007. Nitrates and Nitrites. U.S. 

Environmental Protection Agency. http:// 

www.epa.gov/teach/chem_summ/ 

Nitrates_summary.pdf. Accessed December 2009. 

24FDEP 2009. Chemical Data for 2004, 2005, 

2006, 2007 and 2008. Florida Department of 

Environmental Protection. http:// 

www.dep.state.fl.us/water/drinkingwater/ 

chemdata.htm. Accessed January 2010. 

25Southern Regional Water Program. 2010. 

Drinking Water and Human Health in Florida. 

Southern Regional Water Program, http:// 

srwqis.tamu.edu/florida/program-information/ 

florida-target-themes/drinking-water-and-humanhealth.aspx. Accessed January 2010. 

sunlight that submerged grasses need to 

grow, leading to a decline of seagrass 

beds and decreased habitat for juvenile 

organisms. Algal blooms can also 

increase turbidity and impair the ability 

of fish and other aquatic life to find 

food.8 Algae can also damage or clog the 

gills of fish and invertebrates.9

HABs can form toxins that cause 

illness or death for some animals. Some 

of the more commonly affected animals 

include sea lions, turtles, seabirds, 

dolphins, and manatees.10 More than 

50% of unusual marine mortality events 

may be associated with HABs.11 Lower 

level consumers, such as small fish or 

shellfish, may not be harmed by algal 

toxins, but they bioaccumulate toxins, 

causing higher exposures for higher 

level consumers (such as larger predator 

fish), resulting in health impairments 

and possibly death.12 13

There are many examples of HAB 

toxins significantly affecting marine 

animals. For example, between March 

and April 2003, 107 bottlenose dolphins 

(Tursiops truncatus) died, along with 

hundreds of fish and marine 

invertebrates, along the Florida 

Panhandle.14 High levels of brevetoxin 

(a neurotoxin), produced by a harmful 

species of dinoflagellate (a type of 

algae), were measured in all of the 

stranded dolphins examined, as well as 

in their fish prey.15

In freshwater, cyanobacteria can 

produce toxins that have been 

implicated as the cause of a large 

number of fish and bird mortalities. 

These toxins have also been tied to the 

death of pets and livestock that may be 

exposed through drinking contaminated 

water or grooming themselves after 

bodily exposure.16 A recent study 

showed that at least one type of 

cyanobacteria has been linked to cancer 

and tumor growth in animals.17

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.18 19 Low oxygen, or 

hypoxia, often occurs in episodic 

‘‘events,’’ which sometimes develop 

overnight. Mobile species, such as adult 

fish, can sometimes survive by moving 

to areas with more oxygen. However, 

migration to avoid hypoxia depends on 

species mobility, availability of suitable 

habitat, and adequate environmental 

cues for migration. Less mobile or 

immobile species, such as oysters and 

mussels, cannot move to avoid low 

oxygen and are often killed during 

hypoxic events.20 While certain mature 

aquatic animals can tolerate a range of 

dissolved oxygen levels that occur in 

the water, younger life stages of species 

like fish and shellfish often require 

higher levels of oxygen to survive.21

Sustained low levels of dissolved 

oxygen cause a severe decrease in the 

amount of aquatic life in hypoxic zones 

and affect the ability of aquatic 

organisms to find necessary food and 

habitat. In extreme cases, anoxic 

conditions occur when there is a 

complete lack of oxygen. Very few 

organisms can live without oxygen (for 

example some microbes), hence these 

areas are sometimes referred to as dead 

zones.22

Primary impacts to humans result 

directly from elevated nutrient pollution 

levels and indirectly from the 

subsequent water body changes that 

occur from increased nutrients (such as 

algal blooms and toxins). Direct impacts 

include effects on human health 

through drinking water or consuming 

toxic shellfish. Indirect impacts include 

restrictions on recreation (such as 

boating, swimming, and kayaking). 

Algal blooms can prevent opportunities 

to swim and engage in other types of 

recreation. In areas where recreation is 

determined to be unsafe because of algal 

blooms, warning signs are often posted 

to discourage human use of the waters. 

Highly elevated nitrogen levels, in the 

form of nitrate, in drinking water 

supplies and private wells can cause 

methemoglobinemia (blue baby 

syndrome, which refers to high levels of 

nitrate in a baby’s blood that reduce the 

blood’s ability to deliver oxygen to the 

skin and organs resulting in a bluish 

tinge to the skin; in severe cases 

methemoglobinemia can lead to coma 

and death).23 Monitoring of Florida 

Public Water Supplies from 2004–2007 

indicates that violations of nitrate 

maximum contaminant levels (MCL) 

ranged from 34–40 violations 

annually.24 In addition, in the 

predominantly agricultural regions of 

Florida, of 3,949 drinking water wells 

analyzed for nitrate by the Florida 

Department of Agriculture and 

Consumer Services, (FDACS) and the 

FDEP, 2,483 (63%) contained detectable 

nitrate and 584 wells (15%) contained 

nitrate above the U.S. EPA MCL. Of the 

584 wells statewide that exceeded the 

MCL, 519 were located in the Central 

Florida Ridge citrus growing region, 

encompassed primarily by Lake, Polk 

and Highland Counties.25 Human health 

can also be impacted by disinfection 

byproducts formed when disinfectants 

(such as chlorine) used to treat drinking 

water react with organic carbon (from 

the algae in source waters). Some 

disinfection byproducts have been 

linked to rectal, bladder, and colon 

cancers; reproductive health risks; and 

liver, kidney, and central nervous 

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26USEPA. 2009. Drinking Water Contaminants. 

U.S. Environmental Protection Agency. Accessed 

http://www.epa.gov/safewater/hfacts.html. 

December 2009. 

27CFR. 2006. 40 CFR parts 9, 141, and 142: 

National Primary Drinking Water Regulations: Stage 

2 Disinfectants and Disinfection Byproducts Rule. 

Code of Federal Regulations, Washington, DC. 

http://www.epa.gov/fedrgstr/EPA-WATER/2006/ 

January/Day-04/w03.htm. Accessed December 

2009. 

28Carmichael, W.W. 2000. Assessment of BlueGreen Algal Toxins in Raw and Finished Drinking 

Water. AWWA Research Foundation, Denver, CO. 

29NOAA. 2009. Marine Biotoxins. National 

Oceanic and Atmospheric Administration. http:// 

www.nwfsc.noaa.gov/hab/habs_toxins/ 

marine_biotoxins/index.html. Accessed December 

2009. 

30WHOI. 2008. Hearing on ’Harmful Algal 

Blooms: The Challenges on the Nation’s Coastlines.’ 

Woods Hole Oceanographic Institution. http:// 

www.whoi.edu/page.do?pid=8916&tid=282 

&cid=46007. Accessed December 2009. 

31 Dodds, W.K., W.W. Bouska, J.L. Eitzmann, T.J. 

Pilger, K.L. Pitts, A.J. Riley, J.T. Schloesser, and D.J. 

Thornbrugh. 2009. Eutrophication of U.S. 

freshwaters: analysis of potential economic 

damages. Environ.l Sci. Tech.y. 43(1):12–19. 

32Florida Department of Environmental 

Protection. 2008. Integrated Water Quality 

Assessment for Florida: 2008 305(b) Report and 

303(d) List Update. 

33Florida Department of Environmental 

Protection. 2008. Integrated Water Quality 

Assessment for Florida: 2008 305(b) Report and 

303(d) List Update. 

34U.S. Census Bureau. 2009. 2008 Population 

Estimates Ranked by State. http:// 

factfinder.census.gov. 

35Perry, W.B. 2008. Everglades restoration and 

water quality challenges in south Florida. 

Ecotoxicology 17:569–578. 

36USGS. 2009. Florida Waters: A Water 

Resources Manual. http://sofia.usgs.gov/ 

publications/reports/floridawaters/. Accessed June 

9, 2009. 

37Florida Department of Environmental 

Protection. 2008. Integrated Water Quality 

Assessment for Florida: 2008 305(b) Report and 

303(d) List Update. 

system problems.26 27 Humans can also 

be impacted by accidentally ingesting 

toxins, resulting from toxic algal blooms 

in water, while recreating or by 

consuming drinking water that still 

contains toxins despite treatment. For 

example, cyanobacteria toxins can 

sometimes pass through the normal 

water treatment process.28 After 

consuming seafood tainted by toxic 

HABs, humans can develop 

gastrointestinal distress, memory loss, 

disorientation, confusion, and even 

coma and death in extreme cases. Some 

toxins only require a small dose to cause 

illness or death.29 EPA expects that by 

addressing protection of aquatic life 

uses through the application of the 

proposed numeric nutrient criteria in 

this rulemaking, risks to human health 

will also be alleviated, as nutrient levels 

that represent a balance of natural 

populations of flora and fauna will not 

produce HABs nor result in highly 

elevated nitrate levels. 

Nutrient pollution and eutrophication 

can also impact the economy through 

additional reactive costs, such as 

medical treatment for humans who 

ingest HAB toxins, treating drinking 

water supplies to remove algae and 

organic matter, and monitoring water for 

shellfish and other affected resources. 

Economic losses from algal blooms 

and HABs can include reduced property 

values for lakefront areas, commercial 

fishery losses, and lost revenue from 

recreational fishing and boating trips, as 

well as other tourism-related businesses. 

Commercial fishery losses occur 

because of a decline in the amount of 

fish available for harvest due to habitat 

and oxygen declines. Some HAB toxins 

can make seafood unsafe for human 

consumption, and can reduce the 

amount of fish bought because people 

might question if eating fish is safe after 

learning of the presence of the algal 

bloom.30 To put the issue into 

perspective, consider the following 

estimates: For freshwater lakes, losses in 

fishing and boating trip-related revenues 

nationwide due to eutrophication are 

estimated to range from $370 million to 

almost $1.2 billion dollars and loss of 

lake property values from excessive 

algal growth are estimated to range from 

$300 million to $2.8 billion annually on 

a national level.31

3. Nutrient Pollution in Florida 

Water quality degradation resulting 

from excess nitrogen and phosphorus 

loadings is a documented and 

significant environmental issue in 

Florida. According to Florida’s 2008 

Integrated Report,32 approximately 

1,000 miles of rivers and streams, 

350,000 acres of lakes, and 900 square 

miles of estuaries are impaired for 

nutrients in the State. To put this in 

context, these values represent 

approximately 5% of the assessed river 

and stream miles, 23% of the assessed 

lake acres, and 24% of the assessed 

square miles of estuaries that Florida 

has listed as impaired in the 2008 

Integrated Report.33 Nutrients are 

ranked as the fourth major source of 

impairment for rivers and streams in the 

State (after dissolved oxygen, mercury 

in fish, and fecal coliforms). For lakes 

and estuaries, nutrients are ranked first 

and second, respectively. As discussed 

above, impairments due to nutrient 

pollution result in significant impacts to 

aquatic life and ecosystem health. 

Nutrient pollution also represents, as 

mentioned above, an increased human 

health risk in terms of contaminated 

drinking water supplies and private 

wells. 

Florida is particularly vulnerable to 

nutrient pollution. Historically, the 

State has experienced a rapidly 

expanding population, which is a strong 

predictor of nutrient loading and 

associated effects, and which combined 

with climate and other natural factors, 

make Florida waters sensitive to 

nutrient effects. Florida is currently the 

fourth most populous state in the 

nation, with an estimated 18 million 

people.34 Population is expected to 

continue to grow, resulting in an 

expected increase in urban 

development, home landscapes, and 

wastewater. Florida’s flat topography 

causes water to move slowly over the 

landscape, allowing ample opportunity 

for eutrophication responses to develop. 

Similarly, small tides in many of 

Florida’s estuaries (especially on the 

Gulf coast) also allow for welldeveloped eutrophication responses in 

tidal waters. Florida’s warm and wet, 

yet sunny, climate further contributes to 

increased run-off and subsequent 

eutrophication responses.35 Exchanges 

of surface water and ground water 

contribute to complex relationships 

between nutrient sources and the 

location and timing of eventual 

impacts.36

In addition, extensive agricultural 

development and associated hydrologic 

modifications (e.g., canals and ditches) 

amplify the State’s susceptibility to 

nutrient pollution. Many of Florida’s 

inland areas have extensive tracts of 

agricultural lands. Much of the 

intensive agriculture and associated 

fertilizer usage takes place in locations 

dominated by poorly drained sandy 

soils and with high annual rainfall 

amounts, two conditions favoring 

nutrient-rich runoff. These factors, along 

with population increase, have 

contributed to a significant upward 

trend in nutrient inputs to Florida’s 

waters.37 High historical water quality 

and the human and aquatic life uses of 

many waterways in Florida often means 

that very low nutrients, low 

productivity, and high water clarity are 

needed and expected to maintain uses. 

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 

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38U.S. EPA. 2000a. Nutrient Criteria Technical 

Guidance Manual: Lakes and Reservoirs. Office of 

Water, Washington, DC. EPA–822–B–00–001. 

39U.S. EPA. 2000b. Nutrient Criteria Technical 

Guidance Manual: Rivers and Streams. Office of 

Water, Washington, DC. EPA–822–B–00–002. 

40U.S. EPA. 2001. Nutrient Criteria Technical 

Manual: Estuarine and Coastal Marine Waters. 

Office of Water, Washington, DC. EPA–822–B–01– 

003, and wetlands (U.S. EPA, 2007). 

that protect the designated use’’ and that 

such criteria ‘‘must be based on sound 

scientific rationale and must contain 

sufficient parameters or constituents to 

protect the designated use.’’ As noted 

above, 40 CFR 130.10(b) provides that 

‘‘In designating uses of a water body and 

the appropriate criteria for those uses, 

the state shall take into consideration 

the water quality standards of 

downstream waters and ensure that its 

water quality standards provide for the 

attainment and maintenance of the 

water quality standards of downstream 

waters.’’ 

States are also required to review their 

WQS at least once every three years and, 

if appropriate, revise or adopt new 

standards (CWA section 303(c)(1)). 

States are required to submit these new 

or revised WQS for EPA review and 

approval or disapproval (CWA section 

303(c)(2)(A)). Finally, CWA section 

303(c)(4)(B) authorizes the 

Administrator to determine, even in the 

absence of a state submission, that a 

new or revised standard is needed to 

meet CWA requirements. The criteria 

proposed in this rulemaking apply to 

lakes and flowing waters of the State of 

Florida. EPA’s proposal defines ‘‘lakes 

and flowing waters’’ to mean inland 

surface waters that have been classified 

by Florida as Class I (Potable Water 

Supplies Use) or Class III (Recreation, 

Propagation and Maintenance of a 

Healthy, Well-Balanced Population of 

Fish and Wildlife Use) water bodies 

pursuant to Florida Administrative 

Code (F.A.C.) Rule 62–302.400, 

excluding wetlands, and which are 

predominantly fresh waters. 

C. Water Quality Criteria 

EPA has issued guidance for use by 

states when developing criteria. Under 

CWA section 304(a), EPA periodically 

publishes criteria recommendations 

(guidance) for use by states in setting 

water quality criteria for particular 

parameters to protect recreational and 

aquatic life uses of waters. When EPA 

has published recommended criteria, 

states have the option of adopting water 

quality criteria based on EPA’s CWA 

section 304(a) criteria guidance, section 

304(a) criteria guidance modified to 

reflect site-specific conditions, or other 

scientifically defensible methods. 40 

CFR 131.11(b)(1). 

For nutrients, EPA has published 

under CWA section 304(a) a series of 

peer-reviewed, national technical 

approaches and methods regarding the 

development of numeric nutrient 

criteria for lakes and reservoirs,38 rivers 

and streams,39 and estuaries and coastal 

marine waters.40 Basic analytical 

approaches for nutrient criteria 

derivation include, but are not limited 

to: (1) Stressor-response analysis, (2) the 

reference condition approach, and (3) 

mechanistic modeling. The stressorresponse, 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 EPArecommended 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 timeconsuming 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 overenrichment 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 

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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 reissuance. 

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 sitespecific analysis is conducted to 

determine what the narrative criterion 

means for a particular water body in 

developing a TMDL, the State takes sitespecific considerations into account and 

devises a method that works with the 

available data and information. 

In adopting the Impaired Waters Rule 

(IWR), Florida took important steps 

toward improving implementation of its 

narrative nutrient criterion by 

establishing and publishing an 

assessment methodology to identify 

waters impaired for nutrients. This 

methodology includes numeric nutrient 

impairment ‘‘thresholds’’ above which 

waters are automatically deemed 

impaired. Even when a listing is made, 

however, development of a TMDL is 

then generally required to support 

issuance of a permit or development of 

a BMAP. 

Based on the considerations outlined 

above, EPA concluded that numeric 

criteria for nutrients will enable the 

State to take necessary actions to protect 

the designated uses, in a timelier 

manner. The resource intensive efforts 

to interpret the State’s narrative 

criterion contribute to delays in 

implementing the criterion and 

therefore, affect the State’s ability to 

provide the needed protections for 

applicable designated uses. EPA, 

therefore, determined that numeric 

nutrient criteria are necessary for the 

State of Florida to meet the CWA 

requirement to have criteria that protect 

applicable designated uses. 

The combined impacts of urban and 

agricultural activities, along with 

Florida’s physical features and 

important and unique aquatic 

ecosystems, made it clear that the 

current use of the narrative nutrient 

criterion alone and the resulting delays 

that it entails do not ensure protection 

of applicable designated uses for the 

many State waters that are either 

unimpaired and need protection or have 

been listed as impaired and require 

loadings reductions. EPA determined 

that numeric nutrient water quality 

criteria would strengthen the foundation 

for identifying impaired waters, 

establishing TMDLs, and deriving water 

quality-based effluent limits in NPDES 

permits, thus providing the necessary 

protection for the State’s designated 

uses in its waters. In addition, numeric 

nutrient criteria will support the State’s 

ability to effectively partner with point 

and nonpoint sources to control 

nutrients, thus further providing the 

necessary protection for the designated 

uses of the State’s water bodies. EPA’s 

determination is available at the 

following Web site: http://www.epa.gov/ 

waterscience/standards/rules/fldetermination.htm. 

The January 14, 2009 determination 

stated EPA’s intent to propose numeric 

nutrient criteria for lakes and flowing 

waters in Florida within twelve months 

of the January 14, 2009 determination, 

and for estuarine and coastal waters 

within 24 months of the determination. 

EPA has also entered into a Consent 

Decree with Florida Wildlife Federation, 

Sierra Club, Conservancy of Southwest 

Florida, Environmental Confederation of 

Southwest Florida, and St. Johns 

Riverkeeper, committing to the schedule 

stated in EPA’s January 14, 2009 

determination to propose numeric 

nutrient criteria for lakes and flowing 

waters in Florida by January 14, 2010, 

and for Florida’s estuarine and coastal 

waters by January 14, 2011. The Consent 

Decree also requires that final rules be 

issued by October 15, 2010 for lakes and 

flowing waters, and by October 15, 2011 

for estuarine and coastal waters. 

In accordance with the determination 

and EPA’s Consent Decree, EPA is 

proposing numeric nutrient criteria for 

Florida’s lakes and flowing waters with 

this proposed rule. As envisioned in 

EPA’s determination, this time frame 

has allowed EPA to utilize the large data 

set collected by Florida as part of a 

detailed analysis of nutrient-impaired 

waters. In a separate rulemaking, EPA 

intends to develop and propose numeric 

nutrient criteria for Florida’s estuarine 

and coastal waters by January 14, 2011. 

EPA’s determination did not apply to 

Florida’s wetlands, and as a result, 

Florida’s wetlands will not be addressed 

in this rulemaking or in EPA’s 

forthcoming rulemaking involving 

estuarine and coastal waters. 

III. Proposed Numeric Nutrient Criteria 

for the State of Florida’s Lakes and 

Flowing Waters 

A. General Information 

(1) Which Water Bodies Are Affected by 

This Proposed Rule? 

The criteria proposed in this 

rulemaking apply to lakes and flowing 

waters of the State of Florida. EPA’s 

proposal defines ‘‘lakes and flowing 

waters’’ to mean inland surface waters 

that have been classified as Class I 

(Potable Water Supplies) or Class III 

(Recreation, Propagation and 

Maintenance of a Healthy, WellBalanced 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 

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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 

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41FDEP. 2008. Integrated Water Quality 

Assessment for Florida: 2008 305(b) Report and 

303(d) List Update. Florida Department of 

Environmental Protection. 

42Fernald, E.A. and E.D. Purdum. 1998. Water 

Resources Atlas of Florida. Tallahassee: Institute of 

Science and Public Affairs, Florida State University. 

43U.S. EPA. 1998. National Strategy for the 

Development of Regional Nutrient Criteria. Office of 

Water, Washington, DC. EPA 822–R–98–002; 

Grubbs, G. 2001. U.S. EPA. (Memorandum to 

Directors of State Water Programs, Directors of 

Great Water Body Programs, Directors of 

Authorized Tribal Water Quality Standards 

Programs and State and Interstate Water Pollution 

Control Administrators on Development and 

Adoption of Nutrient Criteria into Water Quality 

Standards. November 14, 2001); Grumbles, B.H. 

2007. U.S. EPA. (Memorandum to Directors of State 

Water Programs, Directors of Great Water Body 

Programs, Directors of Authorized Tribal Water 

Quality Standards Programs and State and Interstate 

Water Pollution Control Administrators on Nutrient 

Pollution and Numeric Water Quality Standards. 

May 25, 2007). 

located at www.regulations.gov, Docket 

ID No. EPA–HQ–OW–2009–0596. 

B. Proposed Numeric Nutrient Criteria 

for the State of Florida’s Lakes 

Florida’s 2008 Integrated Water 

Quality Assessment Report 41 indicates 

that Florida lakes provide important 

habitats for plant and animal species 

and are a valuable resource for human 

activities and enjoyment. The State has 

more than 7,700 lakes, which occupy 

close to 6% of its surface area. The 

largest lake, Lake Okeechobee (covering 

435,840 acres), is the ninth largest lake 

in surface area in the United States and 

the second largest freshwater lake 

wholly within the coterminous United 

States.42 Most of the State’s lakes are 

shallow, averaging seven to 20 feet 

deep, although many sinkhole lakes and 

parts of other lakes are much deeper. 

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.): 

Long-term average lake color and alkalinity Chlorophyll a f

(μg/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

A B C D E F 

Colored Lakes > 40 PCU .................................................... 20 0.050 1.23 0.050–0.157 1.23–2.25 

Clear Lakes, Alkaline ≤ 40 PCU 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 longterm 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). bBaseline 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. dPlatinum Cobalt Units (PCU) assessed as true color free from turbidity. Long-term average color based on a rolling average of up to seven 

years using all available lake color data. e If alkalinity data are unavailable, a specific conductance of 250 micromhos/cm may be substituted. 

f Chlorophyll a is defined as corrected chlorophyll, or the concentration of chlorophyll a remaining after the chlorophyll degradation product, 

phaeophytin a, has been subtracted from the uncorrected chlorophyll a measurement. 

The following section describes the 

methodologies EPA used to develop its 

proposed numeric nutrient criteria for 

lakes. EPA is soliciting comments and 

scientific data regarding the proposed 

criteria for lakes and their derivation. 

Section III.B(4) describes one alternative 

approach and two supplementary 

modifications considered by the Agency 

in developing this lakes proposal. EPA 

solicits comments and data on that 

approach and those modifications. 

(2) Methodologies for Deriving EPA’s 

Proposed Criteria for Lakes 

The process used to develop proposed 

numeric nutrient criteria for a range of 

diverse waters begins with grouping 

those waters into categories that 

generally have a common response to 

elevated levels of the stressor pollutants, 

in this case TN and TP. The following 

sections provide a discussion of (1) the 

lake classification approach for this 

proposal, (2) identification of an 

appropriate response variable and the 

levels of that variable that indicate or 

represent healthy aquatic conditions 

associated with each water body 

classification, and (3) the concentrations 

of TN and TP that correspond to 

protective levels of the response 

variable, in this case, chlorophyll a. 

EPA has recommended that nutrient 

criteria include both causal (e.g., TN 

and TP) and response variables (e.g., 

chlorophyll a and some measure of 

clarity) when establishing numeric 

nutrient criteria for water bodies.43 EPA 

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44U.S. EPA. 2000. Nutrient Criteria Technical 

Guidance Manual: Rivers and Streams. Office of 

Water, Washington, DC. EPA–822–B–00–002. 

45Shannon, E.E. and P.L. Brezonik. 1972. 

Limnological characteristics of north and central 

Florida lakes. Limnol. Oceanogr. 17(1): 97–110. 

46Trophic state describes the nutrient and algal 

state of an aquatic system: Oligotrophic (low 

nutrients and algal productivity), mesotrophic 

(moderate nutrients and algal productivity), and 

eutrophic (high nutrients and algal productivity). 

recommends causal variables, in part, to 

have the means to develop source 

control targets and, in part, to have the 

means to assess water body conditions 

with knowledge that responses can be 

variable, suppressed, delayed, or 

expressed at different locations. EPA 

recommends response variables, in part, 

to have a means to assess water body 

conditions that synthesize the effect of 

causal variables over time, recognizing 

the daily, seasonal, and annual 

variability in measured nutrient 

levels.44 The ability to establish 

protective criteria for both causal and 

response variables depends on available 

data and scientific approaches to 

evaluate these data. For its lake criteria, 

EPA is proposing causal variables for 

TN and TP and a response variable for 

chlorophyll a. For water clarity, Florida 

has criteria for transparency and 

turbidity, applicable to all Class I and III 

waters, expressed in terms of a 

measurable deviation from natural 

background (Rules 32–302.530(67) and 

(69), F.A.C.). For further information on 

this topic, refer to EPA’s TSD for 

Florida’s Inland Waters. 

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.45 Different relationships 

between nutrients and chlorophyll a 

emerged when lakes were characterized 

by color, with clear lakes demonstrating 

greater sensitivity to nutrients as would 

be predicted by the increased light 

penetration, which promotes algal 

growth. 

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

represent a comprehensive group of 

lakes that may be naturally oligotrophic. 

Thus, EPA proposes to classify Florida 

clear lakes as either acidic (≤50 mg/L 

alkalinity as 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 (μS/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 μS/cm is sufficiently correlated 

with alkalinity to serve as a surrogate 

measure. Of these two measures, 

alkalinity is the preferred parameter to 

measure because it is less variable and 

therefore, a more reliable indicator, and 

also because it is a more direct measure 

of the presence of underlying geology 

associated with elevated nutrient levels. 

EPA solicits comment on the 

proposed categorization scheme and 

associated thresholds used to classify 

Florida’s lakes. Please see Section 

III.B(4)(b) below in which EPA invites 

comment on alternative lake 

categorization approaches that EPA 

considered, in particular, those 

approaches with respect to alkalinity 

classification and lakes occurring in 

sandhills of northwestern and central 

Florida. 

(b) Methodology for Proposed 

Chlorophyll a Criteria 

Because excess algal growth is 

associated with degradation in aquatic 

life and because chlorophyll a levels are 

a measure of algal growth, EPA is using 

chlorophyll a levels as indicators of 

healthy biological conditions, 

supportive of aquatic life in each of the 

categories of Florida’s lakes described 

above. EPA found multiple lines of 

evidence supporting chlorophyll a 

criteria as an effective indicator of 

ambient conditions that would be 

protective of Florida’s aquatic life use in 

lakes. These lines of evidence included 

trophic state of lakes, historical 

reference conditions in Florida lakes, 

and model results. 

As a primary line of evidence, EPA 

reviewed and evaluated the Trophic 

State Index (TSI) information in 

deriving chlorophyll a criteria that are 

protective of designated aquatic life uses 

in Florida’s lakes. The TSI quantifies the 

degree of eutrophication (oligotrophic, 

mesotrophic, eutrophic) 46 in a water 

body based on observed measurements 

of nutrients and chlorophyll a. These 

types of boundaries are commonly used 

in scientific literature and represent an 

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47Carlson, R.E. 1977. A trophic state index for 

lakes. Limnol. Oceanogr. 22:361–369. 

48Carlson, R.E. 1977. A trophic state index for 

lakes. Limnol. Oceanogr. 22:361–369. 

49Salas and Martino. 1991. A simplified 

phosphorus trophic state index for warm water 

tropical lakes. Wat. Res. 25:341–350. 

50Whitmore and Brenner. 2002. Paleologic 

characterization of pre-disturbance water quality 

conditions in EPA defined Florida lake regions. 

Univ. Florida Dept. Fisheries and Aquatic Sciences. 

30 pp. 

50Whitmore and Brenner. 2002. Paleologic 

characterization of pre-disturbance water quality 

conditions in EPA defined Florida lake regions. 

Univ. Florida Dept. Fisheries and Aquatic Sciences. 

30 pp. 

51 Vighi and Chiaudani. 1985. A simple method 

to estimate lake phosphorus concentrations 

resulting from natural background loadings. Wat. 

Res.19:987–991. 

established, scientific classification 

system to describe current status and 

natural expectations for lake conditions 

with respect to nutrients and algal 

productivity.47 EPA’s review of TSI 

studies 48 49 indicated that in warmwater 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 50 that 

examined preserved diatom frustules in 

Florida lake sediments indicate that 

historical levels of chlorophyll a are 

consistent with mesotrophic 

expectations derived from the TSI 

studies described above, with 

chlorophyll a levels falling just below 

the selected criterion for mesotrophic 

lakes. (These studies did not evaluate 

lakes expected to be naturally 

oligotrophic so there is no comparable 

information for those lakes). 

In addition to this evidence, EPA used 

information from the application of a 

Morphoedaphic Index (MEI) model 51

that predicts nutrient and chlorophyll a 

concentrations for any lake given its 

depth, alkalinity, and color to support 

the proposed chlorophyll a criteria. 

Scientists from the St. John’s Water 

Management District presented 

modeling results for various Florida 

lakes in each colored and clear category 

at the August 5, 2009 meeting of the 

Nutrient Criteria TAC in Tallahassee. In 

addition to predicting natural or 

reference conditions, these scientists 

used the model to predict chlorophyll a 

and TP concentrations associated with a 

10% reduction in water transparency for 

a set of lakes with varying color levels 

and alkalinities. Because submerged 

aquatic vegetation is dependent on light, 

maintaining a lake’s historic balance 

between algae and submerged aquatic 

plants requires maintaining overall 

water transparency. The risk of 

disrupting the balance between algae 

and submerged aquatic plants increases 

when reductions in transparency exceed 

10%. The MEI predictions corroborated 

the results from lake TSI studies and 

investigations of paleolimnological 

reference conditions because natural or 

reference predictions (i.e., a ‘‘no effect’’ 

level) were generally below selected 

criteria levels and 10% transparency 

loss predictions (i.e., a ‘‘threshold effect’’ 

level) were at or slightly above selected 

criteria levels. EPA considered these 

lines of evidence to develop the 

proposed chlorophyll a criteria, 

discussed below by lake class: 

(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, 

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52Canfield, D.E., Jr., M.J. Maceina, L.M. Hodgson, 

and K.A. Langeland. 1983. Limnological features of 

some northwestern Florida lakes. J. Freshw. Ecol. 

2:67–79; Griffith, G.E., D.E. Canfield, Jr., C.A. 

Horsburgh, J.M. Omernik, and S.H. Azevedo. 1997. 

Lake regions of Florida. Map prepared by U.S. EPA, 

Corvallis, OR; available at http://www.epa.gov/wed/ 

pages/ecoregions/fl_eco.htm (accessed 10/09/2009). 

53More information on this issue is available on 

FDEP’s Web site at http://www.dep.state.fl.us/ 

water/wqssp/nutrients/docs/ 

dep_responses_100909.pdf and included in the 

‘‘External Peer Review of EPA’s ‘Proposed Methods 

and Approaches for Developing Numeric Nutrient 

Criteria for Florida’s Inland Waters’ ’’ and EPA’s 

TSD for Florida’s Inland Waters located in the 

docket ID No. EPA–HQ–OW–2009–0596. 

54FDEP document titled, ‘‘DEP’s Responses to 

EPA’s 9/16 Comment Letter.’’ October 9, 2009. 

Located in the docket ID EPA–HQ–OW–2009–0596. 

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 52 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.53 In comments sent to 

EPA via e-mail in October 2009,54 FDEP 

reported that the Nutrient TAC 

suggested in June 2009 that maintaining 

chlorophyll a below 10 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 oligotrophicmesotrophic 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 μg/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. 

EPA specifically solicits comment on 

the chlorophyll a criterion of 6 ug/L and 

the evidence EPA used to support the 

criterion. EPA also solicits comment on 

whether a higher criterion of 9 ug/L, as 

proposed by Florida in its July 2009 

proposed nutrient WQS, would be fully 

protective of clear acidic lakes, and the 

scientific basis for such a conclusion. 

(c) Methodology for Proposed Total 

Phosphorus (TP) and Total Nitrogen 

(TN) Criteria in Lakes 

EPA proposes TP and TN criteria for 

each of the classes of lakes described in 

Section III.B(2)(a). The proposed TP and 

TN criteria are based principally on 

independent statistical correlations 

between TN and chlorophyll a, and TP 

and chlorophyll a for clear and colored 

lakes in Florida. Each data point used in 

the statistical correlations represents a 

geometric mean of samples taken over 

the course of a year in a particular 

Florida lake. After establishing the 

protective levels of chlorophyll a as 20 

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 

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55USEPA. Guidance for 2004 Assessment, Listing 

and Reporting Requirements Pursuant to Sections 

303(d) and 305(b) of the Clean Water Act. http:// 

www.epa.gov/OWOW/tmdl/tmdl0103/Accessed 

December 2009. 

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 lakespecific knowledge of whether the lake 

chlorophyll a threshold is met, accounts 

for the naturally variable behavior of TN 

and TP while ensuring protection of 

aquatic life. 

EPA’s proposed criteria framework 

sets a protective chlorophyll a threshold 

and TN and TP criteria at the lower 

values of the range defined by the 50th 

percentile prediction interval for the 

three different categories of lakes as 

‘‘baseline’’ criteria. The criteria 

framework also provides flexibility for 

FDEP to derive lake-specific, modified 

TN and TP criteria within the bounds of 

the upper and lower values based on at 

least three years of ambient 

measurements where a chlorophyll a 

threshold is not exceeded. More 

specifically, if the chlorophyll a 

criterion for an individual lake is met 

for a period of record of at least three 

years, then the corresponding TN and 

TP criteria may be derived from ambient 

measurements of TN and TP from that 

lake within the bounds of the lower and 

upper values of the prediction interval 

discussed above. Both the ambient 

chlorophyll a levels as well as the 

corresponding ambient TN and TP 

concentrations in the lake must be 

established with at least three years 

worth of data. EPA’s proposed rule 

provides that these modified criteria 

need to be documented by FDEP. EPA’s 

rule, however, does not require that 

FDEP go through a formal SSAC process 

subject to EPA review and approval. 

In this proposed rule, EPA specifies 

that in no case, however, may the 

modified TN and TP criteria be higher 

than the upper value specified in the 

criteria bounds, nor lower than the 

lower value specified in the criteria 

bounds. In addition to nutrients, 

chlorophyll a in a lake may be limited 

by high water color, zooplankton 

grazing, mineral turbidity, or other 

unknown factors. In the absence of 

detailed, site-specific knowledge, the 

upper values represent increasing risk 

that chlorophyll a will exceed its 

criterion value. To maintain the risk at 

a manageable level, the upper values are 

not to be exceeded. EPA requests 

comments on this approach. EPA also 

requests comment on whether the rule 

should specify that the modified TN and 

TP criteria be set at levels lower than 

the lower value of the criteria bounds if 

that is what is reflected in the outcome 

of the ambient-based calculation. 

EPA’s proposed approach for TN and 

TP criteria in lakes reflects the natural 

variability in the relationship between 

chlorophyll a concentrations and 

corresponding TP and TN 

concentrations that may exist in lakes. 

This variability remains even after some 

explanatory factors such as color and 

alkalinity are addressed by placing lakes 

in different categories based on color 

and alkalinity because other natural 

factors play important roles. Natural 

variability in the physical, chemical, 

and biological dynamics for any 

individual lake may result from 

differences in geomorphology, 

concentrations of other constituents in 

lake waters, hydrological conditions and 

mixing, and other factors. 

This approach allows for 

consideration of readily available sitespecific data to be taken into account in 

the expression of TN and TP criteria, 

while still ensuring protection of 

aquatic life by maintaining the 

associated chlorophyll a level at or 

below the proposed chlorophyll a 

criterion level. Because the chlorophyll 

a level in a lake is the direct measure 

of algal production, it can be used to 

evaluate levels that pose a risk to 

aquatic life. The scientific premise for 

the lake-specific ambient calculation 

provision for modified TN and TP 

criteria is that if ambient lake data show 

that a lake’s chlorophyll a levels are 

below the established criteria and its TN 

and/or TP levels are within the lower 

and upper bounds, then those ambient 

levels of TN and TP represent protective 

conditions. Basing the ambient 

calculation upon at least three years 

worth of data is a condition set to 

address and account for year-to-year 

hydrologic variability in the derivation 

of modified criteria. EPA requests 

comment on the requirement of three 

years worth of data for both chlorophyll 

a and TN and TP in order to use this 

option. Specifically, are there situations 

in which less than three years of data 

might be adequate for an adjusted TN or 

TP criterion? 

EPA selected the proposed TP and TN 

criteria based on the relationships with 

chlorophyll a described above. 

However, the MEI modeling results 

described in Section III.B(2)(b) also 

provide additional support for the TP 

criteria selection. The MEI predicted a 

10% transparency loss when TP 

concentrations ranged from 0.053–0.098 

mg/L in colored lakes (with one 

predicted value at 0.037 mg/L), from 

0.038–0.068 mg/L in clear, alkaline 

lakes, and from 0.012–0.024 mg/L in 

clear, acidic lakes. All but one of these 

predicted values are within the lower 

and upper bounds of the proposed TP 

criteria. The MEI modeling results did 

not address TN. 

(d) Proposed Criteria: Duration and 

Frequency 

Numeric criteria include magnitude 

(i.e., how much), duration (i.e., how 

long), and frequency (i.e., how often) 

components. Beginning with EPA’s 

2004 Integrated Report Guidance,55 EPA 

has used the term ‘‘exceeding criteria’’ to 

refer to situations where all criteria 

components are not met. The term 

‘‘digression’’ refers to an ambient level 

that goes beyond a level specified by the 

criterion-magnitude (e.g., in a given grab 

sample). The term ‘‘excursion’’ refers to 

conditions that do not meet the 

criterion-magnitude and criterionduration, in combination. A criterionfrequency specifies the maximum rate at 

which ‘‘excursions’’ may occur. 

For the chlorophyll a, TN, and TP 

criteria for lakes, the criterionmagnitude 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-thanonce-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 

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56 Kenney (1998) as reported in Salas and Martino 

(1991). 

57 Jeppeson et al. 2005. Lake responses to reduced 

nutrient loading—an analysis of contemporary longterm data from 35 case studies. Freshwater Biology 

50: 1747–1771. 

individual years at individual lakes. The 

appropriate duration period is therefore 

annual. The key question is whether 

this annual geometric mean needs to be 

met every year, or if some allowance for 

a particular year to exceed the 

applicable criterion could still be 

considered protective. 

Data that contribute to the analysis of 

TSI, as well as data generated from 

supporting paleolimnological studies 

and MEI modeling, typically represent 

periods of time greater than a single 

year. Moreover, many of the models and 

analyses that form the basis of TSI 

results are designed to represent the 

‘‘steady-state,’’ or long-term stable water 

quality conditions. However, 

researchers have suggested caution in 

applying steady-state assumptions to 

lakes with long residence times.56 In 

other words, the effects of spikes in 

annual loading could linger and disrupt 

the steady-state in some lakes. As a 

result, EPA is proposing two 

expressions of allowable frequency, 

both of which are to be met. First, EPA 

proposes a no-more-than-one-in-threeyears 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. 

EPA requests comment on these 

proposed criteria duration and 

frequency expressions, and the basis for 

their derivation. EPA notes that some 

scientists and resource managers have 

suggested that nutrient criteria duration 

and frequency expressions should be 

more restrictive to avoid seasonal or 

annual ‘‘spikes’’ from which the aquatic 

system cannot easily recover, whereas 

others have suggested that criteria 

expressed as simply a long-term average 

of annual geometric means, consistent 

with data used in criteria derivation, 

would still be protective. EPA also 

requests comment on any alternative 

duration and frequency expressions that 

might be considered protective, 

including (1) a criterion-duration 

expressed as a monthly average or 

geometric mean, (2) a criterionfrequency expressed as meeting 

allowable magnitude and duration every 

year, (3) a criterion-frequency expressed 

as meeting allowable magnitude and 

duration in more than half the years of 

a given assessment period, and (4) a 

criterion-frequency expressed as 

meeting allowable magnitude and 

duration as a long-term average only. 

EPA further requests comment on 

whether an expression of the criteria in 

terms of an arithmetic average of annual 

geometric mean values based on rolling 

three-year periods of time would also be 

protective of the designated use. 

(e) Application of Lake-Specific, 

Ambient Condition-Based Modified TP 

and TN Criteria 

As described in Section III.B(2)(c), 

EPA is proposing a framework that uses 

both the upper and lower bounds of the 

50th percentile prediction interval to 

allow the derivation of modified TP and 

TN lake-specific criteria to account for 

the natural variability in the 

relationship between chlorophyll a and 

TP and TN that may exist in certain 

lakes. The proposed rule would allow 

FDEP to calculate ambient modified 

criteria for TN and TP based on at least 

three years of ambient monitoring data 

with (a) at least four measurements per 

year and (b) at least one measurement 

between May and September and one 

measurement between October and 

April each year. If a calculated modified 

TN and TP criterion is below the lower 

value, then the lower value is the 

criteria. If a calculated modified TN and 

TP criterion is above the upper value, 

then the upper bound is the criteria. 

Calculated modified TP and TN values 

may not exceed criteria applicable to 

streams to which a lake discharges. 

EPA’s proposed rule provides that 

FDEP must document these modified 

criteria and establish them in a manner 

that clearly recognizes their status as the 

applicable criterion for a particular lake 

so that the public and all regulatory 

authorities are aware of its existence. 

However, EPA’s proposed rule does not 

require that FDEP go through a formal 

SSAC process subject to EPA review 

and approval. (For more information on 

the SSAC process, please refer to 

Section V of this proposal). EPA 

believes such modified criteria do not 

need to go through the SSAC process 

because the conditions under which 

they are applicable are clearly stated in 

the proposed rule and the methods of 

calculation are clearly laid out so that 

the outcome is predictable and 

transparent. By providing a specific 

process for deriving modified criteria 

within the WQS rule itself, each 

individual outcome of this process is an 

effective WQS for CWA purposes and 

does not need separate approval by 

EPA. 

One technical concern is the extent to 

which the variability in the data relating 

chlorophyll a levels to TN and TP levels 

truly reflects differences between lakes, 

as opposed to temporal differences in 

the conditions in the same lake. To 

address this issue, EPA verified that the 

observed variability in the supporting 

analysis was indeed predominantly 

‘‘across lake’’ variability, not ‘‘within 

lake’’ variability. 

Another technical concern is that 

there may be a time lag between the 

presence of high nutrients and the 

biological response. In a study of 

numerous lakes, researchers found that 

there was often a lag period of a few 

years in chlorophyll a response to 

changes in nutrient loading, but that 

there was correlation between 

chlorophyll a and nutrient 

concentrations on an annual basis.57

The difference between nutrient loading 

and nutrient concentration as a function 

of time is related to the hydraulic 

retention time of a lake. EPA proposed 

TN and TP criteria as concentration 

values with an annual averaging period, 

so any time lag in response would not 

be expected to confound the derivation 

of modified criteria. Furthermore, EPA 

is proposing to require three years worth 

of data, which would reflect any short 

time lag in response. 

A third technical concern is the 

presence of temporary or long-term sitespecific 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. 

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4190 Federal Register / Vol. 75, No. 16 / Tuesday, January 26, 2010 / Proposed Rules 

EPA is proposing to require that the 

ambient calculation for modified TP and 

TN criteria be based on at least a threeyear record of observation, and be based 

on representative sampling (i.e., four 

samples per year with at least one 

between May and September and one 

between October and April) during each 

year. These requirements will minimize 

the influence of long-term site-specific 

factors and ensure longer-term stable 

conditions. EPA selected three years as 

a reasonable minimum length of time to 

appropriately account for anomalous 

conditions in any given year that could 

lead to erroneous conclusions regarding 

the true relationship between nutrient 

levels in a lake and chlorophyll a levels. 

EPA anticipates that the State would use 

all recent consecutive years of data on 

record (i.e., it would not be appropriate 

to select three random years within a 

complete record over the past seven 

years). EPA is requiring four 

measurements within a year to provide 

seasonal representation (i.e., May– 

September and October–April). 

Providing seasonal representation is 

important because nutrient levels can 

vary by season. In addition, this 

minimum sample size is conducive to 

the derivation of central tendency 

measurements, such as a geometric 

mean, with an acceptable degree of 

confidence. EPA is proposing that the 

chlorophyll a criterion must be met in 

each of the three or more years of 

ambient monitoring that define the 

record of observation for the lake to be 

eligible for the ambient calculation 

modified provision for TN and TP. EPA 

requests comment on whether three 

years of data is sufficient to establish for 

a particular lake that there is a 

fundamentally different relationship 

between chlorophyll a levels and TN 

and TP levels. EPA also requests 

comment on whether less data or a 

different specification would be 

sufficient to establish this different 

relationship in a particular lake, e.g. 

whether revised TN and TP ambient 

criteria should be allowed when the 

chlorophyll a criterion concentration 

has been exceeded once in three years. 

Application of the ambient 

calculation provision has implications 

for assessment and permitting because 

the outcome of applying this provision 

is to establish alternate numeric TN and 

TP values as the applicable numeric 

nutrient criteria for TN and TP. For 

accountability and tracking purposes, 

the State would need to document in a 

publicly available and accessible 

manner, such as on an official State Web 

site, the result of the ambient 

calculation for any given lake. The State 

may wish to issue a public notification, 

with an opportunity to submit 

additional data and check calculations, 

to ensure an appropriate value is 

determined. The State may wish to 

publicly certify the outcome via a 

Secretarial order or some other official 

statement of intent and applicability. 

EPA’s preference is that once modified 

criteria are developed, they remain the 

applicable criteria for the long-term. The 

State has the flexibility to revise the 

criteria, but the expectation is that they 

will not be a continuously moving target 

for implementation purposes. As an 

example of how the lakes criteria might 

work in practice, consider a colored lake 

which meets the chlorophyll a criterion. 

If FDEP established a modified TP 

criterion of 0.110 mg/L and subsequent 

monitoring showed levels at 0.136 mg/ 

L, that lake would not be considered 

attaining the applicable criteria for CWA 

purposes (unless the State goes through 

the process of establishing a revised 

modified criterion). 

The permitting authority would use 

publicly certified modified TN or TP 

criteria to develop water quality-based 

effluent limits (WQBELs) that derive 

from and comply with applicable WQS. 

In this application, the permit writer 

would use the modified ambient 

criterion, computed as described above, 

as the basis for any reasonable potential 

analysis or permit limit derivation. In 

this case, as in any other case, EPA 

expects the details to be fully 

documented in the permit fact sheet. 

This type of ambient calculation 

provision based on meeting response 

criteria applicable to the assessed water 

may not be appropriate when the 

established TN and TP criteria are 

serving to maintain and protect waters 

downstream. To address this concern, 

EPA proposes that calculated TP and 

TN values in a lake that discharges to 

a stream may not exceed criteria 

applicable to the stream to which a lake 

discharges. EPA requests comment on 

this provision. 

(3) Request for Comment and Data on 

Proposed Approach 

EPA is soliciting comment on the 

approaches described in this proposal, 

the data underlying those approaches, 

and the proposed criteria. EPA will 

evaluate all data and information 

submitted by the close of the public 

comment period for this rulemaking 

with regard to nutrient criteria for 

Florida’s lakes. For the application of 

the modified ambient calculation 

provision, EPA is seeking comment on 

allowing the calculation to occur one 

time only, based on an adequate period 

of record, and then holding that value 

as the protective TP or TN criteria for 

future assessment and implementation 

purposes. EPA is also seeking comment 

on whether to require an ambient 

chlorophyll a level demonstrated to be 

below the chlorophyll a threshold 

criterion for at least three years become 

the protective chlorophyll a criterion for 

a lake subject to the modified ambient 

calculation provision (i.e., whether to 

require a more stringent chlorophyll a 

criterion if three years of data show that 

the more stringent level reflects current 

conditions in the lake). EPA also 

requests comment on whether an 

additional condition for being able to 

apply a modified criterion include 

continued ambient monitoring and 

verification that chlorophyll a levels 

remain below the protective criterion. 

EPA could specify that modified criteria 

remain in effect as long as FDEP 

subsequently conducts monthly (or 

some other periodic) monitoring of the 

lake to ensure that chlorophyll a levels 

continue to meet the protective 

criterion. If this monitoring is not 

conducted and documented, EPA could 

specify that the baseline criterion would 

become the applicable criterion. Among 

others, this provision may address 

concerns about whether the modified 

criterion adequately represents longterm 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. 

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58 Griffith, G.E., D.E. Canfield, Jr., C.A. Horsburgh, 

J.M. Omernik, and S.H. Azevedo. 1997. Florida lake 

regions. U.S. EPA, Corvallis, OR. http:// 

www.epa.gov/wed/pages/ecoregions/fl_eco.htm. 

(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 lakespecific 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.58 However, 

some stakeholders have suggested that 

many lakes in the clear, acidic class (as 

currently defined) might be sufficiently 

protected with a chlorophyll a criterion 

of 9 μg/L. EPA believes the scientific 

basis for a 9 μg/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. 

Alternatively, EPA could lower the 

defining alkalinity threshold to 20 mg/ 

L CaCO3 so that the clear, acidic lakes 

category would only include lakes with 

very acidic values and correspondingly 

low chlorophyll a, TN, and TP values. 

EPA’s analysis of a distribution of 

alkalinity data from Florida’s clear lakes 

found that lakes with alkalinity values 

≥ 20 mg/L CaCO3 had higher levels of 

nutrients and nutrient response 

parameters than lakes with alkalinity 

values < 20 mg/L CaCO3. By adjusting 

the alkalinity threshold to 20 mg/L 

CaCO3, EPA would be creating a smaller 

group of clear, acidic lakes that may be 

more representative of naturally more 

acidic, oligotrophic conditions than the 

proposed alkalinity threshold of 50 mg/ 

L CaCO3. EPA opted to propose a 

threshold of 50 mg/L CaCO3 because it 

represents a more comprehensive group 

of lakes that may be naturally 

oligotrophic (i.e., ensures protection 

where there may be some uncertainty). 

EPA solicits comment on these 

alternative approaches to classifying 

Florida’s lakes. EPA also notes, as 

discussed previously, that FDEP 

recommended a criterion of 9 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 

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4192 Federal Register / Vol. 75, No. 16 / Tuesday, January 26, 2010 / Proposed Rules 

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 longterm 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). bPanhandle 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. cBone Valley region includes the following watersheds: Tampa Bay Watershed, Sarasota Bay Watershed, and Charlotte Harbor Watershed. dPeninsula 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-bysite, 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 

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59U.S. EPA. 1998. National Strategy for the 

Development of Regional Nutrient Criteria. Office of 

Water, Washington, DC. EPA 822–R–98–002; 

Grubbs, G. 2001. U.S. EPA. (Memorandum to 

Directors of State Water Programs, Directors of 

Great Water Body Programs, Directors of 

Authorized Tribal Water Quality Standards 

Programs and State and Interstate Water Pollution 

Control Administrators on Development and 

Adoption of Nutrient Criteria into Water Quality 

Standards. November 14, 2001); Grumbles, B.H. 

2007. U.S. EPA. (Memorandum to Directors of State 

Water Programs, Directors of Great Water Body 

Programs, Directors of Authorized Tribal Water 

Quality Standards Programs and State and Interstate 

Water Pollution Control Administrators on Nutrient 

Pollution and Numeric Water Quality Standards. 

May 25, 2007). 

60U.S. EPA. 2000. Nutrient Criteria Technical 

Guidance Manual: Rivers and Streams. Office of 

Water, Washington, DC. EPA–822–B–00–002. 

61U.S. EPA. 2000. Nutrient Criteria Technical 

Guidance Manual: Lakes and Reservoirs. Office of 

Water, Washington, DC. EPA–822–B–00–001; U.S. 

EPA. 2000. Nutrient Criteria Technical Guidance 

Manual: Rivers and Streams. Office of Water, 

Washington, DC. EPA–822–B–00–002; U.S. EPA. 

2001. Nutrient Criteria Technical Manual: Estuarine 

and Coastal Marine Waters. Office of Water, 

Washington, DC. EPA–822–B–01–003. 

62U.S. EPA. 2000. Nutrient Criteria Technical 

Guidance Manual: Rivers and Streams. Office of 

Water. 4304. EPA–822–B–00–002. 

include both causal (e.g., TN and TP) 

and response variables (e.g., chlorophyll 

a and some measure of clarity) for water 

bodies.59 EPA recommends causal 

variables, in part, to have the means to 

develop source control targets and, in 

part, to have the means to assess stream 

condition with knowledge that 

responses can be variable, suppressed, 

delayed, or expressed at different 

locations. EPA recommends response 

variables, in part, to have a means to 

assess stream condition that synthesizes 

the effect of causal variables over time, 

recognizing the daily, seasonal, and 

annual variability in measured nutrient 

levels.60

The ability to establish protective 

criteria for both causal and response 

variables depends on available data and 

scientific approaches to evaluate these 

data. Whereas, there are data available 

for water column chlorophyll a 

(phytoplankton) and algal thickness on 

various substrates (periphyton) for 

certain types of streams in Florida, there 

are currently no available approaches to 

interpret these data to infer 

scientifically supported thresholds for 

these nutrient-specific response 

variables in Florida streams. 

Additionally, in previously published 

guidance,61 EPA has recommended 

water clarity as a response variable for 

numeric nutrient criteria because algal 

density in a water column results in 

turbidity, and thus a related decrease in 

water clarity can serve as an indicator 

of excess algal growth. For water clarity, 

Florida has criteria for transparency and 

turbidity, applicable to all Class I and III 

waters, expressed in terms of a 

measurable deviation from natural 

background (32–302.530(67) and (69), 

F.A.C.). Therefore, EPA is not proposing 

criteria for any response variable in 

Florida’s streams at this time, however, 

EPA will consider additional data that 

becomes available during the comment 

period. One approach for deriving 

criteria for water quality variables such 

as a measure for water clarity or 

chlorophyll a, could be to apply a 

statistical distribution approach to a 

population of streams for each of the 

proposed NWRs. This approach is 

further described in previous EPA 

guidance.62

For Florida streams, EPA has 

determined that there are sufficient 

available data on TN and TP 

concentrations with corresponding 

information on biological condition for 

a wide variety of stream types that can 

be used to derive numeric nutrient 

criteria for those causal variables. EPA 

used multiple measures of stream 

condition (or metrics) that describe the 

biological condition of the benthic 

invertebrate community. EPA then 

coupled the stream condition metrics 

with associated measurements of TN 

and TP concentrations to provide the 

basis for deriving causal variable 

numeric nutrient criteria. 

EPA’s proposed instream numeric 

nutrient criteria for Florida’s streams are 

based upon EPA’s evaluation of data on 

TN and TP levels in rivers and streams 

that have been carefully evaluated by 

FDEP, and subsequently by EPA, on a 

site-specific basis and identified as 

biologically healthy. EPA’s approach 

results in numeric criteria that are 

protective of the streams themselves. 

EPA has determined, however, that 

these instream values may not always be 

protective of the designated uses in 

downstream lakes and estuaries. 

Therefore, EPA has also developed an 

approach for deriving TN and TP values 

for rivers and streams to ensure the 

protection of downstream lakes and 

estuaries. This approach is discussed in 

Section III.C(6). 

(a) Methodology for Stream 

Classification: EPA’s Nutrient 

Watershed Regions (NWRs) 

EPA classified Florida’s streams north 

of Lake Okeechobee by separating 

watersheds with a substantially 

different ratio of TN and TP export into 

Nutrient Watershed Regions (NWR). The 

resulting regions reflect the inherent 

differences in the natural factors that 

contribute to nutrient concentrations in 

streams (e.g., geology, soil composition, 

and/or hydrology). Reliance on a 

watershed-based classification approach 

reflects the understanding that upstream 

water quality affects downstream water 

quality. This watershed classification 

also facilitates the ability to address the 

effects of TN and TP from streams to 

downstream lakes or estuaries in the 

same watershed. 

EPA’s classification approach results 

in four watershed regions: the 

Panhandle, the Bone Valley, the 

Peninsula, and the North Central (for a 

map of these regions, refer to the EPA 

TSD for Florida’s Inland Waters or the 

list of watersheds in the table above). 

These four regions do not include the 

south Florida region (corresponding to 

FDEP’s Everglades Bioregion) that is 

addressed separately in Section III.E 

which sets out EPA’s proposed numeric 

nutrient criteria for canals in south 

Florida. All flowing waters in this 

region are either a canal or a wetland. 

When classifying Florida’s streams, 

EPA identified geographic areas of the 

State as having phosphorus-rich soils 

and geology, such as the Bone Valley 

and the northern Suwannee River 

watershed. As indicated above, the Bone 

Valley region and the Suwannee River 

watersheds are classified in this 

proposal as separate NWRs because it is 

well established that the naturally 

phosphorus-rich soils in these areas 

significantly influence stream 

phosphorus concentrations in these 

watersheds. EPA would expect from a 

general ecological standpoint that the 

associated aquatic life uses, under these 

naturally-occurring, nutrient-rich 

conditions, would be supported. The 

Agency requests comment on this 

particular classification decision 

(regions based on phosphorus-rich 

soils), as well as an alternate 

classification approach that would not 

separate out the phosphorus-rich 

watersheds described in this notice. The 

latter approach is similar to the 

approach proposed by EPA, but would 

not result in separate NWRs for the 

Bone Valley and/or North Central. 

Rather these NWRs would be integrated 

within the other NWRs. 

(b) The Use of the Stream Condition 

Index as an Indicator of Biologically 

Healthy Conditions 

For EPA’s proposed approach, the 

Agency utilized a multi-metric index of 

benthic macroinvertebrate community 

composition and taxonomic data known 

as the Stream Condition Index (SCI) 

developed by FDEP to assess the 

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4194 Federal Register / Vol. 75, No. 16 / Tuesday, January 26, 2010 / Proposed Rules 

63The SCI method was developed and calibrated 

by FDEP. See ‘‘Fore et al. 2007. Development and 

testing biomonitoring tools for macroinvertebrates 

in Florida streams (Stream Condition Index and 

BioRecon). Final report to Florida Department of 

Environmental Protection’’ and the EPA TSD for 

Florida’s Inland Waters for more information on the 

SCI. 

64Appendix H in ‘‘Fore et al. 2007. Development 

and testing biomonitoring tools for 

macroinvertebrates in Florida streams (Stream 

Condition Index and BioRecon). Final report to 

Florida Department of Environmental Protection’’. 

65See the EPA TSD for Florida’s Inland Waters 

for more information on the proportional odds 

regression model. 

66FL IWR and STORET can be found at: http:// 

www.dep.state.fl.us/WATER/STORET/INDEX.HTM. 

biological health of Florida’s streams.63

Of the metrics that comprise the SCI, 

some decrease in response to human 

disturbance-based stressors, such as 

excess nutrients; for example, (1) total 

taxa richness, (2) richness of 

Ephemeroptera (mayflies), (3) richness 

of Plecoptera (stoneflies), (4) percentage 

of sensitive taxa, and (5) percentage of 

filterers and suspension feeders. Other 

metrics increase in response to human 

disturbance-based stressors; for 

example, percent of very tolerant taxa 

(e.g., Genera Prostoma, Lumbriculus) 

and percent of the dominant taxa (i.e., 

numerical abundance of the most 

dominant taxon divided by the total 

abundance of all taxa). 

The SCI was developed by FDEP in 

2004, with subsequent revisions in 2007 

to reduce the variability of results. In 

order to ensure that data are produced 

with the highest quality, field biologists 

and lab technicians must follow 

detailed Standard Operating Procedures 

(SOPs) and additional guidance for 

sampling and data use provided through 

a FDEP document entitled ‘‘Sampling 

and Use of the Stream Condition Index 

(SCI) for Assessing Flowing Waters: A 

Primer (DEP–SAS–001/09).’’ Field 

biologists must pass a rigorous audit 

with FDEP, and laboratory taxonomists 

are regularly tested and must maintain 

greater than 95% identification 

accuracy. 

EPA considered two lines of evidence 

in determining the SCI range of scores 

that would indicate biologically healthy 

systems. The first line of evidence was 

an evaluation of SCI scores in streams 

considered by FDEP to be leastdisturbed streams in Florida. A 

statistical analysis balanced the 

probability of a stream being included 

in this reference set with the probability 

of a stream not being included in this 

reference set, and indicated that an SCI 

score of 40 was an appropriate 

threshold. SCI scores range from 1 to 

100 with higher scores indicating 

healthier biology. 

A second line of evidence was the 

result of an expert workshop convened 

by FDEP in October 2006. The 

workshop included scientists with 

specific knowledge and expertise in 

stream macroinvertebrates. These 

experts were asked to individually and 

collectively evaluate a range of SCI data 

(i.e., macroinvertebrate composition and 

taxonomic data) and then assign those 

data into one of the six Biological 

Condition Gradient (BCG) 64 categories, 

ranging from highly disturbed (Category 

6) to pristine (Category 1). EPA analyzed 

the results of these categorical 

assignments using a proportional odds 

regression model 65 that predicts the 

probability of an SCI score occurring 

within one of the BCG categories by 

overlapping the ranges of SCI scores 

associated with each category from the 

individual expert assignment. The 

results of the analysis provided support 

for identifying a range of SCI scores that 

minimized the probability of incorrectly 

assigning a low quality site to a high 

quality category, and incorrectly 

assigning a high quality site to a low 

quality category, using the collective 

judgment of expert opinion. The results 

indicated a range of SCI scores of 40– 

44 to represent an appropriate threshold 

of healthy biological condition. Please 

refer to the EPA TSD for Florida’s 

Inland Waters for more information on 

such topics as EPA’s estimates of the 

Type I and Type II error associated with 

various threshold values. Thus, two 

very different approaches yielded 

comparable results. A subsequent EPA 

statistical analysis indicated that 

nutrient conditions in Florida streams 

within different regions remain 

essentially constant within an SCI score 

range of 40–50 providing further 

support for a selection of 40 as a 

threshold that is sufficiently protective 

for this application. The resulting TN 

and TP concentrations associated with a 

SCI score of 40 versus 50 did not 

represent a statistical difference and 40 

was more in line with other lines of 

evidence for a SCI score threshold. 

(c) Methodology for Calculating 

Instream Protection Values: The 

Nutrient Watershed Region Distribution 

Approach 

EPA evaluated several methodologies, 

including reference conditions and 

stressor-response relationships, to 

develop values that protect designated 

uses of Florida streams instream. EPA 

analyzed stressor-response relationships 

in Florida streams based on available 

data, but, as mentioned above, did not 

find sufficient scientific support for 

their use in the derivation of numeric 

nutrient criteria for Florida streams. 

More specifically, EPA was not able to 

demonstrate a sufficiently strong 

correlation between the biological 

response indicators (e.g., chlorophyll a, 

periphyton biomass, or SCI) and TN or 

TP concentrations. Thus, the Agency 

could not confidently predict a specific 

biological response (such as an SCI 

score) for an individual stream solely 

from the associated stream 

measurements of TN or TP 

concentrations. 

There may be several reasons why 

empirical relationships between fieldderived data of nutrient stressor and 

biological response variables show a 

relatively weak correlation. First, the 

relationship between nutrient 

concentrations and a biological 

response, such as algal growth, can be 

confounded by the presence of other 

stressors. For example, other stressors, 

such as excessive scour could cause low 

benthic invertebrate diversity, as 

measured by the SCI, even where 

nutrients are low. Excessive scour could 

also suppress a biological response 

(such as chlorophyll a or periphyton 

biomass) when nutrients are high. 

Another reason for stressor-response 

relationships with low correlations is 

that algal biomass accumulation is 

difficult to characterize because 

dynamic conditions in an individual 

stream can allow algae to accumulate 

and be removed rapidly, which is 

difficult to capture with periodic 

monitoring programs. 

As an alternative to the stressorresponse approach, EPA analyzed the 

TN and TP concentrations associated 

with a healthy biological condition in 

streams, and examined the statistical 

distributions of these data in order to 

identify an appropriate threshold for 

providing protection of aquatic life 

designated uses. To derive the instream 

protection values under this approach, 

EPA first assembled the available 

nutrient concentrations and biological 

response data for streams in Florida. 

EPA used FDEP’s data from the IWR and 

STORET66 databases and identified 

sites where SCI scores were 40 and 

higher. EPA further screened these sites 

by cross-referencing them with Florida’s 

CWA section 303(d) list for Florida and 

excluded sites with identified nutrient 

impairments or dissolved oxygen 

impairments associated with elevated 

nutrients. EPA grouped the remaining 

sites (hereafter, biologically healthy 

sites) according to its nutrient 

watershed regions (Panhandle, Bone 

Valley, Peninsula, and North Central). 

For each nutrient watershed region, EPA 

compiled nutrient data (TN and TP 

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concentrations) associated with the 

biologically healthy sites, and 

calculated distributional statistics for 

annual average TN and TP 

concentrations. 

The second step in deriving instream 

protection values was to further 

characterize the distribution of TN and 

TP among biologically healthy sites. 

Specifically, EPA calculated the number 

of biologically healthy sites within 

integer log-scale ranges of TN and TP 

concentrations, as well as the 

cumulative distribution. These nutrient 

distributions from biologically healthy 

sites in each nutrient watershed region 

are represented on a log-scale because 

concentration data are typically lognormally distributed. A log-normal 

distribution is skewed, with a mode 

near the geometric mean rather than the 

arithmetic mean. 

The third step in deriving instream 

protection values was to determine 

appropriate thresholds from these 

distributions for providing protection of 

aquatic life designated uses. Selection of 

a central tendency of the distribution 

(i.e., the median or geometric mean of a 

log-normal distribution) would imply 

that half of the biologically healthy sites 

are not attaining their uses. In contrast, 

an extreme upper end of the distribution 

(e.g., the 90th or 95th percentile) may be 

the most likely to be heavily influenced 

by extreme event factors that are not 

representative of typically biologically 

healthy sites. This might be the case 

because the upper tail of the 

distribution might reflect a high loading 

year (landscape and/or atmospheric), 

and/or lack of nutrient uptake by algae 

(in turn due to a myriad of physical and 

biological factors like scour, grazing, 

light limitation, other pollutants). Thus, 

this tail of the distribution may just 

represent the most nutrient ‘‘tolerant’’ 

among the sites. Another possibility is 

that these streams may experience 

adverse effects from nutrient 

enrichment that are not yet reflected in 

the SCI score. A reasonable choice for a 

threshold is one which lies just above 

the vast majority of the population of 

healthy streams. This choice is 

reasonable because it reflects a point 

where most biologically healthy sites 

will still be identified as attaining uses, 

but avoids extrapolations into areas of 

the distribution characterized by only a 

few data points (as would be the case for 

the 90th or 95th percentile). When a 

threshold is established as a water 

quality criterion, sites well below that 

threshold might be allowed to 

experience an increase in nutrient levels 

up to the threshold level. There is little 

assurance that biologically healthy sites 

with nutrient concentrations well below 

the 90th or 95th percentile would 

remain biologically healthy if nutrient 

concentrations increased to those levels 

because relatively few sites with 

nutrient concentrations as high as those 

at the 90th or 95th percentile are 

demonstrated to be biologically healthy. 

The range between the 25th and 75th 

percentiles, or inter-quartile range, is a 

common descriptive statistic used to 

characterize a distribution of values. For 

example, statistical software packages 

typically include the capability to 

display distributions as ‘‘box and 

whisker’’ plots, which very prominently 

identify the inter-quartile range. The 

inter-quartile range of a log normal 

distribution spans a smaller range of 

values than the inter-quartile range of a 

distribution of the data evenly spread 

across the entire range of values. This 

means that the further a value goes past 

the 75th percentile of a log normal 

distribution, the less representative it is 

of the majority of data (in this case, less 

representative of biologically healthy 

sites). Within the inter-quartile range of 

a log normal distribution, the slope of 

the cumulative frequency distribution 

will be the greatest. The 75th percentile 

represents a reasonable upper bound of 

where there is the greatest confidence 

that biologically healthy sites will be 

represented. Beyond the inter-quartile 

range (i.e., below the 25th percentile 

and above the 75th percentile), there is 

a greater chance that measurements may 

represent anomalies that would not 

correspond to long-term healthy 

conditions in the majority of streams. 

Based on this analysis, EPA concluded 

that the 75th percentile represents an 

appropriate and well-founded protective 

threshold derived from a distribution of 

nutrient concentrations from 

biologically healthy sites. EPA solicits 

comment on its analysis of what 

constitutes a protective threshold. 

(d) Proposed Criteria: Duration and 

Frequency 

Aquatic life water quality criteria 

contain three components: Magnitude, 

duration, and frequency. For the TN and 

TP numeric criteria for streams, the 

derivation of the criterion-magnitude 

values is described above and these 

values are provided in the table in 

Section III.C(1). The criterion-duration 

of this magnitude is specified in 

footnote a of the streams criteria table as 

an annual geometric mean. EPA is 

proposing two expressions of allowable 

frequency, both of which are to be met. 

First, EPA proposes a no-more-than-onein-three-years excursion frequency for 

the annual geometric mean criteria for 

lakes. Second, EPA proposes that the 

long-term arithmetic average of annual 

geometric means not to exceed the 

criterion-magnitude concentration. EPA 

anticipates that Florida will use their 

standard assessment periods as 

specified in Rule 62–303, F.A.C. 

(Impaired Waters Rule) to implement 

this second provision. These proposed 

duration and frequency components of 

the criteria are consistent with the data 

set used to derive these criteria, which 

applied distributional statistics to 

measures of annual geometric mean 

values from multiple years of record. 

EPA has determined that this frequency 

of excursions will not result in 

unacceptable effects on aquatic life as it 

will allow the stream ecosystem enough 

time to recover from an occasionally 

elevated year of nutrient loadings. The 

Agency requests comment on these 

proposed duration and frequency 

components of the stream numeric 

nutrient criteria. 

EPA notes that some scientists and 

resource managers have suggested that 

nutrient criteria duration and frequency 

expressions should be more restrictive 

to avoid seasonal or annual ‘‘spikes’’ 

from which the aquatic system cannot 

easily recover, whereas others have 

suggested that criteria expressed as 

simply a long-term average of annual 

geometric means, consistent with data 

used in criteria derivation, and would 

still be protective. EPA requests 

comment on alternative duration and 

frequency expressions that might be 

considered protective, including (1) a 

criterion-duration expressed as a 

monthly average or geometric mean, (2) 

a criterion-frequency expressed as 

meeting allowable magnitude and 

duration every year, (3) a criterionfrequency expressed as meeting 

allowable magnitude and duration in 

more than half the years of a given 

assessment period, and (4) a criterionfrequency expressed as meeting 

allowable magnitude and duration as a 

long-term average only. EPA further 

requests comment on whether an 

expression of the criteria in terms of an 

arithmetic average of annual geometric 

mean values based on rolling three-year 

periods of time would also be protective 

of the designated use. 

(3) Request for Comment and Data on 

Proposed Approach 

EPA is soliciting comments on the 

approaches taken by the Agency to 

derive these proposed criteria, the data 

underlying those approaches, and the 

proposed criteria specifically. EPA is 

requesting that the public submit any 

other scientific data and information 

that may be available related to nutrient 

concentrations and associated biological 

responses in Florida’s streams. EPA is 

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67U.S. EPA. 2000. Nutrient Criteria Technical 

Guidance Manual: Rivers and Streams. Office of 

Water. 4304. EPA–822–B–00–002. 

68A quantitative, integrated measure of the degree 

of human landscape disturbance within 100 meters 

on either side of a specified stream reach and 

extending to 10 kilometers upstream of the same 

stream reach. 

69FDEP document titled, ‘‘Responses to 

Earthjustice’s Comments on the Department’s 

Reference Sites.’’ Draft October 2, 2009. Located in 

the docket ID EPA–HQ–OW–2009–0596. 

soliciting comment specifically on the 

selection of criteria parameters for TN 

and TP; the proposed classification of 

streams into four regions based on 

aggregated watersheds; and the 

conclusion that the proposed criteria for 

streams are protective of designated 

uses and adequately account for the 

spatial and temporal variability of 

nutrients. In addition, EPA requests 

comment on folding the Suwannee 

River watershed in north central Florida 

into the larger Peninsula NWR (i.e., not 

having a separate North Central region) 

or, alternatively, making a smaller North 

Central region within Hamilton County 

alone where the highest phosphorusrich soils are located, with the 

remainder of the North Central 

becoming part of the Peninsula Region. 

(4) Alternative Approaches Considered 

by EPA 

During EPA’s review of the available 

data and information for derivation of 

numeric nutrient criteria for Florida’s 

streams, EPA also considered an 

alternative approach for criteria 

derivation. EPA is specifically 

requesting comment on a modified 

reference condition approach called the 

benchmark distribution approach, as 

described below. 

(a) Benchmark Distribution Approach 

EPA’s previously published guidance 

has recommended a variety of methods 

to derive numeric nutrient criteria.67

One method, the reference condition 

approach, relies on the identification of 

reference waters that exhibit minimal 

impacts from anthropogenic disturbance 

and are known to support designated 

uses. The thresholds of nutrient 

concentrations where designated uses 

are in attainment are calculated from a 

distribution of the available associated 

measurements of ambient nutrient 

concentrations at these reference 

condition sites. 

EPA is seeking comment on a 

modified reference condition approach, 

which was developed by FDEP and is 

referred to as the benchmark 

distribution approach. The benchmark 

approach relies on least-disturbed sites 

rather than true reference, or minimallyimpacted, sites. The benchmark 

distribution is a step-wise procedure 

used to calculate distributional statistics 

of TN and TP from identified leastdisturbed streams. 

(i) Identification of Least-Disturbed 

Streams 

FDEP identified benchmark stream 

sites in the following step-wise manner 

(1) compiled a list of sites with low 

landscape development intensity using 

FDEP’s Landscape Development 

Intensity Index,68 (2) eliminated any 

sites on Florida’s CWA section 303(d) 

list of impaired waters due to nutrients, 

as well as certain sites impaired for 

dissolved oxygen, where the State 

determined the dissolved oxygen 

impairment was caused by nutrients, (3) 

eliminated any sites with nitrate 

concentrations greater than FDEP’s 0.35 

mg/L proposed nitrate-nitrite criterion 

in order to reduce the possibility of 

including sites with far-field human 

disturbance from groundwater impacts, 

(4) eliminated sites known by FDEP 

district scientists to be disturbed, (5) 

eliminated potentially erroneous data 

through outlier analysis, (6) verified 

sites using high resolution aerial 

photographs, and (7) verified a random 

sample of the sites in the field. 

(ii) Calculation of Benchmark 

Distribution Approach and Selection of 

Percentiles From the Benchmark 

Distribution 

FDEP selected either the 75th or 90th 

percentile of the benchmark distribution 

approach from FDEP’s proposed 

nutrient regions (75th percentile—Bone 

Valley; 90th percentile—Panhandle, 

North Central, Northeast, and 

Peninsula). FDEP’s rationale for 

selecting either the 75th or 90th 

percentiles was based on the degree of 

certainty regarding the benchmark sites 

reflecting least-disturbed conditions and 

a probability (10% for the 90th 

percentile) of falsely identifying a leastdisturbed site as being impaired for 

nutrients. 

With this approach, the distribution 

of available annual geometric means of 

nutrient concentrations for the 

benchmark sites within the regional 

classes of streams is calculated. To 

compute the numeric criteria for the 

causal variables, TN, and TP, EPA is 

seeking comment on whether the 75th 

or 90th percentile of the benchmark 

distribution for each nutrient stream 

region should be selected. As mentioned 

above, the rationale for selecting either 

the 75th or 90th percentiles is based on 

the degree of certainty regarding the 

benchmark sites reflecting leastdisturbed conditions and a probability 

of falsely identifying a least-disturbed 

site as being impaired for nutrients or 

vice-versa. In cases where data are more 

limited for a given nutrient region (i.e., 

in the Bone Valley there were only four 

sites), the 75th percentile may be more 

appropriate because the 90th percentile 

may not be sufficiently robust (i.e., may 

be highly sensitive to a few data points). 

In other cases, the 90th percentile may 

be more appropriate when there is a 

more extensive data set. For further 

information, please refer to EPA’s TSD 

for Florida’s Inland Waters, Chapter 2: 

Methodology for Deriving U.S. EPA’s 

Proposed Criteria for Streams. 

In evaluating whether to propose this 

approach, EPA determined that a 

considerable amount of uncertainty 

remained whether this approach would 

result in a list of benchmark sites that 

represented truly least-disturbed 

conditions. Specifically, EPA is 

concerned that nutrient concentrations 

at these sites may reflect anthropogenic 

sources (e.g., sources more than 100 

meters away from and/or 10 kms 

upstream of the segment), even if the 

sites appear least-disturbed on a local 

basis. EPA is particularly concerned that 

several benchmark sites in the FDEP 

dataset appear to have a high potential 

to be affected by fertilizations associated 

with forestry activities. FDEP provided 

an analysis in which FDEP concluded 

that this is not likely.69 EPA solicits 

comment on this issue and more 

generally on whether the benchmark 

sites identified by FDEP in its July 2009 

proposal are an appropriate set of leastdisturbed sites on which to base the 

criteria calculations. 

(5) Request for Comment and Data on 

Alternative Approach 

EPA is soliciting comment on the 

alternative to deriving numeric nutrient 

criteria for Florida’s streams as 

described in Section III.C(4). 

(6) Protection of Downstream Lakes and 

Estuaries 

Two key objectives of WQS are: First, 

to protect the immediate water body to 

which a criterion initially applies and, 

second, to ensure that criteria provide 

for protection of downstream WQS 

affected by flow of pollutants from the 

upstream water body. See 40 CFR 

131.11 and 131.10(b). EPA WQS 

regulations reflect the importance of 

protecting downstream waters by 

requiring that upstream WQS ‘‘provide 

for the attainment and maintenance of 

the water quality standards of 

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downstream waters.’’ 40 CFR 131.10(b). 

Thus, in developing numeric nutrient 

criteria for Florida, EPA considered both 

instream aquatic conditions and 

downstream aquatic ecosystem needs. 

In addressing the issue of how, if at all, 

instream criteria values need to be 

adjusted to assure attainment of 

downstream standards, EPA necessarily 

examined the WQS for downstream 

lakes and estuaries. For lakes, this 

analysis starts with the numeric nutrient 

criteria proposed in this notice. For 

estuaries, this notice proposes an 

analytical approach to determine the 

loadings that a particular estuary can 

receive and still assure attainment and 

maintenance of the State’s WQS for the 

estuary (i.e., a protective load). An 

approach is then proposed for 

translating those downstream loading 

values into criteria levels in the 

contributing watershed stream reaches 

in a manner that ensures that the 

protective downstream loadings are not 

exceeded. 

In connection with both lakes and 

estuaries, EPA fully recognizes that 

there are a range of important technical 

questions and related significant issues 

raised by this proposed approach for 

developing instream water quality 

criteria that are protective of 

downstream designated uses. With 

regard, in particular, to the protection of 

estuaries, the Agency is working closely 

with FDEP to derive estuarine numeric 

nutrient criteria for proposal and 

publication in 2011. Even though 

estuarine numeric nutrient criteria will 

be developed in 2011, there is already 

a substantial body of information, 

science, and analysis that presently 

exists that should be considered in 

determining flowing water criteria that 

are protective of downstream water 

quality. 

The substantial data, peer-reviewed 

methodologies, and extensive scientific 

analyses available to and conducted by 

the Agency to date indicate that 

numeric nutrient criteria for estuaries, 

when proposed and finalized in 2011, 

may result in the need for more 

stringent rivers and streams criteria to 

ensure protection of downstream water 

quality, particularly for the nitrogen 

component of nutrient pollution. 

Therefore, considering the numerous 

requests for the Agency to share its 

analysis and scientific and technical 

conclusions at the earliest possible 

opportunity to allow for full review and 

comment, EPA is including downstream 

protection values for TN as proposed 

criteria for rivers and streams to protect 

the State’s estuaries in this notice. 

As described in more detail below 

and in EPA’s TSD for Florida’s Inland 

Waters accompanying this notice, these 

proposed nitrogen downstream 

protection values are based on 

substantial data, thorough scientific 

analysis, and extensive technical 

evaluation. However, EPA recognizes 

that additional data and analysis may be 

available for particular estuaries to help 

inform what water quality criteria are 

necessary to protect these waters. EPA 

also recognizes that substantial sitespecific work (including some very 

sophisticated analyses in the context of 

certain TMDLs) has been completed for 

a number of these estuaries. This notice 

and the proposed downstream 

protection values are not intended to 

address or be interpreted as calling into 

question the utility and protectiveness 

of these site-specific analyses. Rather, 

the proposed values represent the 

output of a systematic and scientific 

approach that may be generally 

applicable to all flowing waters in 

Florida that terminate in estuaries for 

the purpose of ensuring the protection 

of downstream estuaries. EPA is 

interested in obtaining feedback at this 

time on this systematic and scientific 

approach. The Agency further 

recognizes that the proposed values in 

this notice will need to be considered in 

the context of the Agency’s numeric 

nutrient criteria for estuaries scheduled 

for proposal in January of 2011. At this 

time, EPA plans to finalize any 

necessary downstream protection values 

for nitrogen in flowing waters as part of 

the second phase of this rulemaking 

process in coordination with the 

proposal and finalization of numeric 

criteria for estuarine and coastal waters 

in 2011. However, if comments, data 

and analyses submitted as a result of 

this proposal support finalizing such 

values sooner, by October 2010, EPA 

may choose to proceed in this manner. 

To facilitate this process, EPA requests 

comments and welcomes thorough 

evaluation on the need for and the 

technical and scientific basis of these 

proposed downstream protection values 

as part of the broader comment and 

evaluation process that this proposal 

initiates. 

EPA believes that a detailed 

consideration and related proposed 

approach to address protection of 

downstream water quality in this 

proposal is necessary for several 

reasons, including (1) water quality 

standards are required to protect 

downstream uses under Federal 

regulations at 40 CFR 131.10(b), 

meaning also for prevention of 

impairment; (2) it may be a relevant 

consideration in the development of any 

TMDLs, NPDES permits, and Florida 

BMAPs that the State completes in the 

interim period between the final rule for 

Florida lakes and flowing waters in 

October 2010 and a final rule for Florida 

estuarine and coastal waters in October 

of 2011; and (3) perhaps most 

importantly, it is essential for informing 

and supporting a transparent and 

engaged public consideration, 

evaluation, and discussion on the 

question of what existing information, 

tools, and analyses suggest regarding the 

need to ensure protection of 

downstream waters. The Agency 

continues to emphasize its interest in 

and request for additional information, 

further analysis, and any alternative 

technically-based approaches that may 

be available to address protection of 

downstream water quality. EPA also 

reiterates its commitment to a full 

evaluation of all comments received and 

notes the ability to issue a NODA to 

allow a full public review should 

significant new additional information 

and analysis become available as part of 

the comment period. 

In deriving criteria to protect 

designated uses, as noted above, Federal 

WQS regulations established to 

implement the CWA provide WQS must 

provide for the protection of designated 

uses in downstream waters. In the case 

of deriving numeric nutrient criteria for 

streams in Florida, EPA’s analyses 

reflected in this notice indicate that the 

proposed criteria values for instream 

protection of streams may not fully 

protect downstream lakes and 

downstream estuaries. EPA’s proposed 

criteria for lakes are, in some cases, 

more stringent than the proposed 

criteria for streams that flow into the 

lakes. For estuaries, EPA’s analyses of 

protective loads delivered to a specific 

estuary, and the corresponding expected 

concentration values for streams that 

flow into that estuary, indicate the 

proposed criteria for instream protection 

may not always be sufficient to provide 

for the attainment and maintenance of 

the estuarine WQS. For more detailed 

information, please consult EPA’s TSD 

for Florida’s Inland Waters, Chapter 2: 

Methodology for Deriving U.S. EPA’s 

Proposed Criteria for Streams. 

To address each of these issues, EPA 

is proposing first, for lakes, an equation 

that allows for input of lake 

characteristics to determine the 

concentration in flowing streams that is 

needed to attain and maintain the 

receiving lake’s designated use and 

protective criteria. Second, for estuaries, 

EPA is proposing an approach for 

identifying the total nutrient loads a 

particular estuary can receive and still 

attain and maintain the State’s 

designated use for the water body. 

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70 Vollenweider, R.A. 1975. Input-output models 

with special reference to the phosphorus loading 

concept in limnology. Schweizerische Zeitschrift 

fur Hydrologie. 37: 53–84; Vollenweider, R.A. 1976. 

Advances in differing critical loading levels for 

phosphorus in lake eutrophication. Mem. Ist. Ital. 

Idrobid. 33:53:83. 

71Fernald, E.A. and E.D. Purdum. 1998. Water 

Resources Atlas of Florida. Tallahassee: Institute of 

Science and Public Affairs, Florida State University. 

72 Gao, X. 2006. Nutrient and Unionized 

Ammonia TMDLs for Lake Jesup, WBIDs 2981 and 

2981A. Prepared by Florida Department of 

Environmental Protection, Division of Water 

Resource Management, Bureau of Watershed 

Management, Tallahassee, FL. 

73Steward, J.S. and E.F. Lowe. In Press. General 

empirical models for estimating nutrient load limits 

for Florida’s estuaries and inland waters. Limnol. 

Oceanogr. 55: (in press). 

Third, also for estuaries, the Agency is 

proposing a methodology to derive 

protective concentration values for the 

instream criteria where necessary to 

assure that downstream estuarine loads 

are not exceeded. The following 

sections provide a more detailed 

explanation of the proposed 

downstream protective approach for 

lakes and then for estuaries. 

(a) Downstream Protection of Lakes 

EPA is proposing an equation to relate 

a lake TP concentration criterion to the 

concentration needed to be met in 

incoming streams to support the lake 

criterion. EPA proposes to apply the 

resulting stream concentration as the 

applicable criterion for all stream 

segments upstream of the lake. EPA 

used a mathematical modeling approach 

to derive this equation, with allowable 

input of lake-specific characteristics, to 

calculate protective criteria necessary to 

assure attainment and maintenance of 

the numeric lake nutrient criteria in this 

proposal. More specifically, EPA started 

with a phosphorus loading model 

equation first developed by 

Vollenweider.70 EPA assumed that 

rainfall exceeds evaporation in Florida 

lakes and that all external phosphorus 

loading comes from streams. EPA 

considers the first assumption 

reasonable given the rainfall frequency 

and volume in Florida. The second 

assumption is reasonable to the extent 

that surface runoff contributions are far 

greater than groundwater or 

atmospheric sources of TP in Florida 

lakes. EPA requests comment on both 

these assumptions. After expressing 

these assumptions in terms of the 

mathematical relationships among 

loading rates, stream flow, and lake and 

stream concentrations, EPA derived the 

following equation to relate a protective 

lake criterion to a corresponding 

protective stream concentration: 

[] [] TP

c

S TP

f

= + L w ( ) 1 1 τ

where: 

[TP]S is the total phosphorus (TP) 

downstream lake protection value, mg/L 

[TP]L is applicable TP lake criterion, mg/L 

cf is the fraction of inflow due to all stream 

flow, 0 ≤ cf ≤ 1 

tw is lake’s hydraulic retention time (water 

volume divided by annual flow rate) 

The term 

( ) 1+ τw

expresses the net phosphorus loss from the 

water column (e.g. via settling of sedimentsorbed phosphorus) as a function of the 

lake’s retention time 

This model equation requires input of 

two lake-specific characteristics: The 

fraction of inflow due to stream flow 

and the hydraulic retention time. Water 

in a lake can come from a combination 

of groundwater sources, rainfall, and 

streams that flow into it. Using the 

model equation above, the calculated 

stream TP criterion to protect a 

downstream lake will be more stringent 

for lakes where the portion of its volume 

coming from streams flowing into it is 

the greatest. In addition, the calculated 

stream TP criterion to protect a 

downstream lake will be more stringent 

for lakes with short hydraulic retention 

times (how long water stays in a lake) 

because the longer the water stays in the 

lake, the more phosphorus will settle 

out in the underlying lake sediment. 

Because lake-specific input values 

may not always be readily available, 

EPA is providing preset values for 

percent contribution from stream flow 

and hydraulic retention time. In Florida 

lakes, rainfall and groundwater sources 

tend to contribute a large portion of the 

total volume of lake water. In fact, only 

about 20% of the more than 7,000 

Florida lakes have a stream flowing into 

them,71 with the rest entirely comprised 

of groundwater and rainwater sources. 

EPA evaluated representative values for 

percent contribution from stream flow 72

and hydraulic retention time,73 and 

selected 50% stream flow contribution 

and 0.2 years (about two and a half 

months) retention time as realistic and 

representative preset values to provide a 

protective outcome for Florida lakes, in 

the absence of site-specific data. Using 

these preset values, streams that flow 

into colored lakes would have a TP 

criterion of 0.12 mg/L, and streams that 

flow into clear, alkaline lakes would 

have a TP criterion of 0.073 mg/L, with 

respect to downstream lake protection. 

In the Peninsula NWR, this compares to 

a 0.107 mg/L TP stream criterion 

protective of instream designated uses. 

EPA’s proposed rule does offer the 

flexibility to use site-specific inputs to 

the Vollenweider equation for fraction 

of inflow from streamflow and 

hydraulic retention time, as long as data 

supporting such inputs are sufficiently 

robust and well-documented. 

EPA carefully evaluated use of a 

settling/loss term for phosphorus in the 

model equation. Florida lakes tend to be 

shallow, and internal loadings to the 

lake water (e.g. from re-suspension of 

settled phosphorus after storms that stir 

up lake sediment) may be substantial. A 

more detailed model might be able to 

simulate this phenomenon 

mechanistically, but would likely 

require substantial site-specific data for 

calibration. For this reason, EPA chose 

to use the model formulation above. 

EPA considered a simpler alternative to 

exclude the settling/loss term from the 

above equation, or even to reverse the 

sign on the settling/loss term so that it 

becomes a net source term, perhaps 

with the inclusion of a default 

multiplier. However, EPA did not have 

sufficient information to conclude that 

such a conservative approach was 

necessary as a general application to all 

Florida lakes. EPA remains open and 

receptive to comment on these 

alternatives or other technically sound 

and protective approaches. EPA’s 

supporting analyses and detailed 

information on this downstream lake 

protection methodology are provided in 

the accompanying TSD for Florida’s 

Inland Waters, Chapter 2: Methodology 

for Deriving U.S. EPA’s Proposed 

Criteria for Streams. 

The same processes that occur in 

lakes and affect lake water phosphorus 

concentration may also occur in streams 

that feed lakes and affect stream water 

phosphorus concentrations. These 

processes include sorption to stream 

bed sediments, uptake into biota, and 

release into the water column from 

decaying vegetation. EPA took into 

consideration these processes when 

deciding whether it would be 

appropriate to add a term to the model 

equation to account for phosphorus loss 

or uptake within the streams in deriving 

stream criteria for downstream lake 

protection. However, the net result of 

these processes is nutrient spiraling, 

whereby nutrients released upstream 

gradually propagate downstream at a 

rate slower than that of the moving 

water, and cycle into and out of the food 

chain in the process. Over the short 

term, the result may be water 

concentrations that decrease in the 

downstream direction. However, unlike 

for nitrogen, there are no long-term 

phosphorus net removal processes at 

work in streams. Phosphorus adsorbed 

to sediment particles is eventually 


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Federal Register / Vol. 75, No. 16 / Tuesday, January 26, 2010 / Proposed Rules 4199 

74 Kennedy, R.H., 1995. Application of the 

BATHTUB Model to Selected Southeastern 

Reservoirs. Technical Report EL–95–14, U.S. Army 

Engineer Waterways Experiment Station, Vicksburg, 

MS. Walker, W.W., 1985. Empirical Methods for 

Predicting Eutrophication in Impoundments; Report 

3, Phase II: Model Refinements. Technical Report 

E–81–9, U.S. Army Engineer Waterways 

Experiment Station, Vicksburg, MS. 

Walker, W.W., 1987. Empirical Methods for 

Predicting Eutrophication in Impoundments; Report 

4, Phase III: Applications Manual. Technical Report 

E–81–9, U.S. Army Engineer Waterways 

Experiment Station, Vicksburg, MS. 

75http://water.usgs.gov/nawqa/sparrow. 

76Hoos, A.B., and G. McMahon. 2009. Spatial 

analysis of instream nitrogen loads and factors 

controlling nitrogen delivery to stream in the 

southeastern United Sates using spatially 

referenced regression on watershed attributes 

(SPARROW) and regional classification 

frameworks. Hydrological Processes. DOI: 10.1002/ 

hyp.7323. 

77Hoos, A.B., S. Terziotti,, G. McMahon, K. 

Savvas, K.C. Tighe, and R. Alkons-Wolinsky. 2008. 

Data to support statistical modeling of instream 

nutrient load based on watershed attributes, 

southeastern United States, 2002: U.S. Geological 

Survey Open-File Report 2008–1163, 50 p. 

78USGS SPARROW publications Web site: http:// 

water.usgs.gov/nawqa/sparrow/intro/pubs.html. 

carried downstream with the sediment, 

and phosphorus taken up by plants is 

eventually returned to the flowing 

water. Over the long term, upstream 

phosphorus inputs are in equilibrium 

with downstream phosphorus outputs. 

Recognizing this feature of stream 

systems and the conservative nature of 

phosphorus in aquatic environments, 

EPA concluded that it was not 

appropriate to include a phosphorus 

loss term that would apply to streams as 

they progress toward a downstream 

lake. For further information, please 

refer to EPA’s TSD for Florida’s Inland 

Waters, Chapter 2: Methodology for 

Deriving U.S. EPA’s Proposed Criteria 

for Streams. 

EPA requests comment on the need 

for additional instream criteria to 

protect uses in downstream lakes. EPA 

further requests comment on the model 

equation approach presented here to 

protect downstream lakes, and also 

requests comment on use of an 

alternative model such as one with a 

negative or zero settling term (i.e., set 

(1+ √tw) in the equation above either 

equal to zero or with the plus sign 

switched to a minus sign). EPA also 

requests comment on whether and how 

to address direct surface runoff into the 

lake. Where this input is substantial and 

land use around the lake indicates that 

phosphorus input is likely, EPA 

believes it may be appropriate to 

include this water volume contribution 

as part of the fraction of inflow 

considered to be streamflow to be 

protective and consistent with the 

assumption of no loading from sources 

other than streamflow. EPA specifically 

requests comment on use of the Land 

Development Index (LDI) as an indicator 

of how to treat this inflow, examination 

of regional groundwater phosphorus 

levels to see if a zero TP input from this 

source is appropriate, and potential 

development of regionally-specific 

preset values as inputs to the equation. 

In addition, EPA requests comment on 

the potential to develop a corollary 

approach for nitrogen. 

EPA is open to alternative technicallysupported approaches based on best 

available data that offer the ability to 

address lake-specific circumstances. 

The Agency recognizes that more 

specific information may be readily 

available for individual lakes which 

could allow the use of alternative 

approaches such as the BATHTUB 

model.74 The Agency welcomes 

comment and technical analysis on the 

availability and application of these 

models. In this regard, EPA requests 

comment on whether there should be a 

specific allowance for use of alternative 

lake-specific models where 

demonstrated to be protective and 

scientifically defensible based upon 

readily and currently available data, and 

whether use of such alternatives should 

best be facilitated through use of the 

SSAC procedure described in Section 

V.C. 

(b) Downstream Protection of Estuaries 

(i) Overview 

EPA is proposing a methodology for 

calculation of applicable criteria for 

streams that flow into estuaries and 

provide for their protection. The 

proposed methodology would allow the 

State to utilize either (1) EPA’s 

downstream protection values (DPVs), 

or (2) the EPA DPV methodology 

utilizing EPA’s estimates of protective 

loading to estuaries but with the load redistributed among the tributaries to each 

estuary, or (3) an alternative quantitative 

methodology, based on scientifically 

defensible approaches, to derive and 

quantify the protective load to each 

estuary and the associated protective 

stream concentrations. The DPV 

methodology with a re-distributed load 

may be used if the State provides public 

notice and opportunity for comment. To 

use an alternative technical approach, 

based on scientifically defensible 

methods to derive and quantify the 

protective load to each estuary and the 

associated protective stream 

concentrations, the State must go 

through the process for a Federal SSAC 

as described in Section V.C. In some 

cases, the substantial and sophisticated 

analyses and scientific effort already 

completed in the context of the TMDL 

process may provide sufficient support 

for a SSAC. In such circumstances, EPA 

encourages FDEP to submit these 

through the SSAC process and EPA 

looks forward to working with FDEP in 

this process. 

EPA’s approach to developing 

nutrient criteria for streams to protect 

downstream estuaries in Florida 

involves two separate steps. The first 

step is determining the average annual 

nutrient load that can be delivered to an 

estuary without impairing designated 

uses. This is the protective load. The 

second step is determining nutrient 

concentrations throughout the network 

of streams and rivers that discharge into 

an estuary that, if achieved, are 

expected to result in nutrient loading to 

estuaries that do not exceed the 

protective load. These concentrations, 

called ‘‘downstream protection values’’ 

or DPVs, depend on the protective load 

for the receiving estuary and account for 

nutrient losses within streams from 

natural biological processes. In this way, 

higher DPVs may be appropriate in 

stream reaches where a significant 

fraction of either TN or TP is 

permanently removed within the reach 

before delivery to downstream receiving 

waters. EPA’s approach utilizes results 

obtained from a watershed modeling 

approach called SPAtially Referenced 

Regressions on Watershed attributes, or 

SPARROW.75 The specific model that 

was used is the South Atlantic, Gulf and 

Tennessee (SAGT) regional SPARROW 

model.76 EPA selected this model 

because it provided the information that 

was needed at the appropriate temporal 

and spatial scales and it applies to all 

waters that flow to Florida’s estuaries.77

SPARROW was developed by the 

United States Geological Survey (USGS) 

and has been reviewed, published, 

updated and widely applied over the 

last two decades. It has been used to 

address a variety of scientific 

applications, including management 

and regulatory applications.78 In order 

to fully understand EPA’s methodology 

for developing DPVs, it is useful to 

understand how the approach utilizes 

results from SPARROW, as well some 

aspects of how SPARROW works. 

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79Bricker, S., B. Longstaff, W. Dennison, A. Jones, 

K. Boicourt, C. Wicks and J. Woerner, 2007. Effects 

of nutrient enrichment in the Nation’s estuaries: A 

decade of change. NOAA Coastal Ocean Program 

Decision Analysis Series No. 26. National Centers 

for Coastal Ocean Science, Silver Spring, MD 322. 

80Hoos, A.B., and G. McMahon. 2009. Spatial 

analysis of instream nitrogen loads and factors 

controlling nitrogen delivery to stream in the 

southeastern United Sates using spatially 

referenced regression on watershed attributes 

(SPARROW) and regional classification 

frameworks. Hydrological Processes. DOI: 10.1002/ 

hyp.7323. 

81Hoos, A.B., S. Terziotti,, G. McMahon, K. 

Savvas, K.C. Tighe, and R. Alkons-Wolinsky. 2008. 

Data to support statistical modeling of instream 

nutrient load based on watershed attributes, 

southeastern United States, 2002: U.S. Geological 

Survey Open-File Report 2008–1163, 50 p. 

The remaining discussion focuses on 

TN, for which EPA has already 

computed DPVs. The approach for 

computing DPVs for TP from estimates 

of the protective TP load is expected to 

be essentially the same as for TN. 

However, there is some question as to 

whether the same approach used to 

determine the protective TN load will 

also apply to TP. EPA requests comment 

on this issue. 

(ii) EPA Approach to Estimating 

Protective Nitrogen Loads for Estuaries 

The first step in EPA’s approach is to 

narrow the range of possible values. The 

protective TN load is expected to vary 

widely among Florida estuaries because 

they differ significantly in their size and 

physical and biological attributes. For 

example, well flushed estuaries are able 

to receive higher TN loading without 

adverse effect compared to poorly 

flushed estuaries. EPA recognized that it 

may be possible to narrow this initially 

very broad range of possible protective 

loads using one consistent approach, 

and then consider whether additional 

information might enable a further 

reduction in uncertainty. EPA is 

soliciting credible scientific evidence 

that may improve these estimates and 

further reduce uncertainty surrounding 

the proposed protective loads. The most 

useful evidence would provide a 

scientific rationale, an alternative 

estimate of the protective load, and an 

associated confidence interval for the 

estimate. For further information, please 

refer to EPA’s TSD for Florida’s Inland 

Waters, Chapter 2: Methodology for 

Deriving U.S. EPA’s Proposed Criteria 

for Streams. 

EPA first narrowed the range of 

possible protective loads by establishing 

an estimate of current loading as an 

upper bound. Most of Florida’s estuaries 

are listed as impaired to some extent by 

nutrients or nutrient-related causes. 

Florida’s 1998 CWA section 303(d) 

verified list of impaired waters under 

the Impaired Waters Rule (FAC 62–303) 

identify many estuaries or estuary 

segments that are impaired by nutrients, 

chlorophyll a, or low dissolved oxygen. 

Many or most estuaries have reduced 

water clarity and substantial loss of 

seagrass habitats. The National 

Estuarine Eutrophication Assessment 79

reports that current conditions are poor 

for many estuaries in Florida. This 

information implies that current levels 

of TN loading are at least an upper limit 

for the protective load and likely exceed 

the protective load in many estuaries. 

EPA used the SAGT–SPARROW 

regional watershed model to estimate 

current loading to each estuary in 

Florida. While nitrogen loads have been 

estimated from monitored gauge stations 

in many stream and rivers, a large 

fraction of Florida streams and 

watersheds are not gauged and thus load 

estimates were not previously available. 

An approach was needed to spatially 

extrapolate the available measurements 

of loading to obtain estimates of loading 

for all streams including those in 

unmonitored watersheds or portions of 

watersheds. The SAGT SPARROW 

model provided these estimates for all 

Florida estuarine watersheds. The 

SPARROW modeling approach utilizes 

a multiple regression equation to 

describe the relationship between 

watershed attributes (i.e., the predictors) 

and measured instream nutrient loads 

(i.e., the responses). The statistical 

methods incorporated into SPARROW 

help explain instream nutrient water 

quality data (i.e., the mass flux of 

nitrogen) as a function of upstream 

sources and watershed attributes. The 

SAGT–SPARROW model utilized 

period of record monitored streamflow 

and nutrient water quality data from 

Florida and across the SAGT region for 

load estimation. SAGT–SPARROW also 

used extensive geospatial data sets 

describing topography, land-use, 

climate, and soil characteristics, 

nitrogen loading for point sources in 

Florida obtained from EPA’s permit 

compliance system, and estimates of 

nitrogen in fertilizer and manure from 

county-level fertilizer sales, census of 

agriculture, and population estimates. 

TN load estimates explain 96% of the 

variation in observed loads from 

monitoring sites across the region with 

no spatial bias at Florida sites.80 A more 

thorough description of the SAGT– 

SPARROW model, the data sources, and 

analyses are found in the EPA TSD for 

Florida’s Inland Waters and in USGS 

publications.81

EPA further narrowed the range of 

possible protective loads by establishing 

the background load as a lower bound. 

EPA recognizes that a measure of 

natural background TN loading is the 

true lower limit, yet EPA recognizes also 

that some level of anthropogenic 

nutrient loading is acceptable, difficult 

to avoid, and unlikely to cause adverse 

biological responses. The current TN 

load minus the fraction of TN loading 

estimated to result from anthropogenic 

sources is used as an estimate of the 

background TN load. EPA used the 

SAGT–SPARROW regional watershed 

model to estimate background loading. 

SAGT–SPARROW empirically 

associates 100% of the measured 

nutrient loading into one of five classes 

(fertilizer, manure, urban, point sources, 

and atmospheric). EPA recognizes that 

some watershed models define more 

types of sources, according to their 

modeling objectives; however, it is 

important to recognize that these are 


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82Steward, J.S. and E.F. Lowe. 2010. General 

empirical models for estimating nutrient load limits 

for Florida’s estuaries and inland waters. Limnology 

and Oceanography 55(1):433–445. 

83For further information on concerns raised by 

FDEP regarding the use of SPARROW, refer to 

‘‘Florida Department of Environmental Protection 

Review of SPARROW: How useful is it for the 

purposes of supporting water quality standards 

development?,’’ ‘‘Assessment of FDEP Panhandle 

Stream proposed benchmark numeric nutrient 

criteria for downstream protection of Apalachicola 

Bay,’’ and ‘‘Analysis of Proposed Freshwater Stream 

Criteria’s Relationship to Protective Levels in the 

Lower St. Johns River Based on the Lower St. Johns 

River Nutrient TMDL.’’ located in EPA’s docket ID 

No. EPA–HQ–OW–2009–0596. 

source classes, not sources, and that 

100% of the measured loading is 

accounted for explicitly or implicitly by 

SPARROW in terms of these source 

classes. 

The class termed ‘‘atmospheric’’ 

reflects all loading that cannot be 

empirically attributed to causal 

variables associated with the other 

classes. EPA used the estimate for this 

class of loading as the background TN 

load. EPA recognizes that the 

SPARROW-estimated ‘‘atmospheric’’ 

load includes anthropogenic 

contributions associated with regionalscale nitrogen emissions and does not 

represent pre-industrial or true ‘‘natural’’ 

background loading. The ‘‘atmospheric’’ 

source term from SPARROW is also not 

equal to atmospheric nitrogen 

deposition as measured by the National 

Atmospheric Deposition Program 

(NADP). To properly interpret the TN 

load attributed to the ‘‘atmospheric’’ 

source term in SPARROW, it is useful 

to recognize that SPARROW is a 

nonlinear regression model that seeks to 

explain measured TN loads in streams 

and rivers in terms of a series of 

explanatory variables. The atmospheric 

term is in all cases less, and often much 

less, than the measured deposition 

because not all the nitrogen deposited to 

the landscape is transported to streams, 

and not all of the nitrogen transported 

in streams reaches estuaries. The 

atmospheric source term from 

SPARROW excludes all the loading 

associated with both local 

anthropogenic nitrogen sources and 

factors contributing to increased 

transport of nitrogen from all sources 

(e.g., impervious surfaces). Therefore, 

EPA expects that reasonable values for 

the protective TN load are not likely to 

be less than these values. 

The protective TN load should be less 

than the current load and greater than 

the background load. Although this 

recognition may appear to be trivial, it 

is important. EPA estimates that TN 

loads to estuaries across Florida vary 

approximately 25-fold (∼2 to 50 grams of 

nitrogen per square meter of estuary 

area). However, the ratio of the current 

load to the background load varies only 

between 1.7 and 5; for most estuaries, 

the range is between 2 and 4. 

Alternatively stated, current TN loads, 

which include local anthropogenic 

nitrogen sources, are two to four-fold 

higher than the background loads which 

do not include those sources. Thus, for 

any specific estuary, there is a relatively 

narrow range between the upper and 

lower bounds of potential protective 

loads. 

EPA acknowledges that not all the TN 

entering estuaries comes directly from 

the streams within its watershed. In 

some estuaries, direct atmospheric 

nitrogen deposition to the estuary 

surface may be an important source of 

TN loading to the estuary. Similarly, 

point sources such as industrial or 

wastewater treatment plant discharges 

directly to the estuary can be significant. 

In general, these sources are most 

significant when the ratio of watershed 

area to estuary area is relatively small 

compared to other estuaries (e.g., St. 

Andrew Bay, Sarasota Bay). In a few 

cases in Florida, point source loads 

directly to the estuary account for a 

large fraction of the aggregate load from 

all sources. 

As a second step, EPA sought to 

further reduce the range of possible 

protective loading values by considering 

additional evidence. One line of 

evidence EPA considered is previous 

estimates of protective loads. These 

have been developed as part of TMDLs 

for Florida estuaries or as part of 

Florida’s Pollutant Load Reduction Goal 

or PLRG program. The scientific 

approaches utilized for TMDLs and 

PLRGs vary from simple to 

sophisticated and have recommended 

TN loading reductions between 3% and 

63%, with a median of 38%. Higher 

reductions are typically associated with 

portions of estuaries currently receiving 

higher anthropogenic loading. 

Unfortunately, these analyses have not 

been completed for all of Florida’s 

estuaries. Steward and Lowe (2009) 82

showed that the TN loading limits 

suggested by TMDLs and PLRGs for a 

variety of aquatic ecosystems in Florida, 

including estuaries, could be 

statistically related to water residence 

time for the receiving water. EPA 

evaluated these relationships as an 

additional line of evidence for 

estimating protective TN loads for 

estuaries. EPA found these relationships 

to confirm in most cases, but not all, 

that the loading limits were likely 

between the bounds EPA previously 

established using SPARROW. However, 

the limits of uncertainty associated with 

the relationship were nearly as large as 

those already established. Nonetheless, 

the models provide additional support 

for EPA’s estimates of protective estuary 

loads, but no further refinement of the 

estimates. 

Another approach to considering 

existing TMDLs and PLRGs is to 

consider directly the loading rate 

reductions recommended from those 

efforts, the median of which is 38% in 

Florida. This percent TN reduction is 

similar to the scientific consensus for 

several well-studied coastal systems 

elsewhere (e.g., Chesapeake Bay, 

northern Gulf of Mexico) which have 

been subjected to increased TN loads 

from known anthropogenic sources. 

EPA recognizes that the magnitude of 

anthropogenic TN loads varies across 

Florida estuaries and that applying a 

uniform percent reduction across all 

estuaries does not account for the 

variable extent of anthropogenic loads 

and could lead to estimates below 

background load. An alternative 

approach is to assume that the 

appropriate loading reduction is 

proportional to the magnitude of 

anthropogenic enrichment. Thus, EPA 

suggests that protective TN loading may 

be estimated by assuming that the 

anthropogenic component of TN loading 

should be reduced by a constant 

fraction. 

As a result, EPA computed the 

protective TN load by reducing the 

current TN load by one half of the 

anthropogenic contribution to that load. 

EPA’s protective load estimates are on 

average 25% less than current TN 

loading (range = 5 to 40%), consistent 

with most TMDLs and PLRGs for 

Florida estuaries. 

EPA developed protective TN loads 

for 16 estuarine water bodies in Florida 

for the purpose of computing DPVs for 

streams that are protective of uses in the 

estuarine receiving waters. EPA did not 

develop loading targets for the seven 

estuarine water bodies in south Florida 

(Caloosahatchee, St. Lucie, Biscayne 

Bay, Florida Bay, North and South Ten 

Thousand Islands, and Rookery Bay), 

because requisite information related to 

TN loading from the highly managed 

canals and waterways cannot be derived 

from SAGT–SPARROW and were not 

available otherwise, and three in central 

Florida (coastal drainage areas of the 

Withlacoochee River, CrystalPithlachascotee River and Daytona-St. 

Augustine) because EPA is still 

evaluating appropriate protective loads 

and the flows necessary to derive DPVs. 

EPA notes that some stakeholders, 

including FDEP staff,83 have raised 

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4202 Federal Register / Vol. 75, No. 16 / Tuesday, January 26, 2010 / Proposed Rules 

84Hoos, A.B., and G. McMahon. 2009. Spatial 

analysis of instream nitrogen loads and factors 

controlling nitrogen delivery to streams in the 

southeastern United States using spatially 

referenced regression on watershed attributes 

(SPARROW) and regional classification 

frameworks. Hydrological Processes. DOI: 10.1002/ 

hyp.7323. 

85Bohlke, J.K., R.C. Antweiler, J.W. Harvey, A.E. 

Laursen, L.K. Smith, R.L. Smith, and M.A. Voytek. 

2009. Multi-scale measurements and modeling of 

Denitrification in streams with varying flow and 

nitrate concentration in the upper Mississippi River 

basin, USA. Biogeochemistry 93: 117–141. DOI 

10.1007/s10533–008–9282–8. 

concerns about the suitability of the 

SAGT SPARROW to address 

downstream protection of estuaries and 

have suggested alternative models and 

approaches that have been applied for 

several of Florida’s larger estuaries and 

their watersheds. These concerns 

include known limitations of the 

SPARROW model, particularly related 

to inadequate resolution of complex 

hydrology in several parts of the State. 

EPA also recognizes this limitation and 

as a result, has not used SAGT 

SPARROW to propose protective loads 

and associated downstream protection 

values for ten estuaries and their 

watersheds in Florida. EPA 

acknowledges that other approaches and 

models may also provide defensible 

estimates of protective loads. 

Among the technical concerns that 

stakeholders including FDEP staff have 

raised are that: (1) SPARROW is useful 

for general pattern, but the large scale 

calibration lead to large errors for 

specific areas, (2) SPARROW only 

utilizes four source inputs, and (3) 

SPARROW was calibrated to only one 

year’s worth of data. As presented in the 

above sections, but to briefly reiterate 

here: (1) SPARROW is calibrated across 

a larger area, but it utilizes a large 

amount of Florida site-specific data and 

it explains 96% of the variation in 

observed loads from monitoring sites, 

(2) SPARROW accounts for all sources, 

but groups them into four general 

categories, and (3) SPARROW uses 

available data from the 1975–2004 

period at monitored sites. This last 

concern may be confused with the 

technical procedure of presenting 

loading estimates as ‘‘detrended to 

2002’’. This procedure accounts for longterm, inter-annual variability to ensure 

that long-term conditions and trends are 

represented. The year 2002 was selected 

as a baseline because it has the best 

available land use/land cover 

information available, but the loading 

estimates, in fact, represent a long-term 

condition representative of many years 

of record. EPA encourages technical 

reviewers to consult with the technical 

references cited in this section for the 

complete explanations of technical 

procedures. 

EPA requests comment on its use of 

the SPARROW model to derive 

protective loads for downstream 

estuaries, as well as data and analyses 

that would support alternate methods of 

deriving downstream loads, or alternate 

methods of ensuring protection of 

designated uses in estuaries. For 

estuaries where sophisticated scientific 

analyses have been completed, relying 

on ample site-specific data to derive 

protective loads in the context of 

TMDLs, EPA encourages FDEP to 

submit resulting alternative DPVs under 

the SSAC process. 

(iii) Computing Downstream Protection 

Values (DPVs) 

Once an estimate of protective TN 

loads is derived, EPA developed a 

methodology for computing DPVs, for 

streams that, if achieved, are expected to 

result in an average TN loading rate that 

does not exceed the protective load. 

EPA’s methodology, which is used as 

the narrative translator, allows for the 

fraction of the protective TN loading 

contributed from each tributary within 

the watershed of an estuary to be 

determined by the fraction of the total 

freshwater flow contributed by that 

tributary. The DPV is specified as an 

average TN concentration, which is 

computed by dividing the protective TN 

load by the aggregate average freshwater 

inflow from the watershed. This 

approach results in the same DPV for 

each stream or river reach that 

terminates into a given estuary. 

EPA’s methodology accounts for 

instream losses of TN. EPA recognizes 

that not all the TN transported within a 

stream network will ultimately reach 

estuaries. Rather, some TN is 

permanently lost from streams. This is 

not the same as reversible 

transformations of TN, such as algal 

uptake. Losses of TN are primarily 

associated with bacterially-mediated 

processes in stream sediments that 

convert biologically available nitrogen 

into inert N2 gas, which enters the 

atmosphere (a process called 

denitrification). This occurs more 

rapidly in shallow streams and at almost 

negligible rates in deeper streams and 

rivers. EPA refers to the fraction of 

nitrogen transported in streams that 

ultimately reaches estuaries as the 

‘‘fraction delivered.’’ Estimates of the 

fraction delivered in Florida are less 

than 50% in streams very distant from 

the coast, but is between 80 and 100% 

in approximately half the stream 

reaches in Florida’s estuarine 

watersheds. 

EPA’s approach relies on estimating 

the fraction of TN delivered to 

downstream estuaries. Measuring 

instream loss rates at the appropriate 

time and space scale is exceedingly 

difficult, and it is not possible to do 

State-wide. EPA is not aware of other 

models or data suitable to estimating 

nitrogen losses in streams across the 

State of Florida. EPA obtained estimates 

from the SAGT–SPARROW model,84

which is possibly the best generally 

applicable approach to obtaining these 

estimates. One reason is that SPARROW 

estimates watershed-scale instream 

losses at the annual time scales across 

the entire region. Estimates of instream 

losses are modeled in SPARROW using 

a first-order decay rate as a function of 

time-of-travel in the reach. The inverse 

exponential relationship is consistent 

with scientific understanding that 

nitrogen losses decrease with increasing 

stream size and with results from 

experimental reach-scale studies using a 

variety of methods.85 EPA recognizes 

that stream attributes other than reach 

time-of-travel or size may influence 

instream loss rates and though the 

SPARROW model did not include these, 

the lack of spatial bias in model 

residuals suggests that inclusion of 

other potential subregional-scale or 

State-wide stream attributes may not 

improve modeled instream loss 

estimates. 

EPA developed and applied this 

methodology to compute DPVs for every 

stream reach in each of 16 estuarine 

watersheds starting with estuarinespecific estimates of the protective load. 

These estuarine watersheds align with 

the Nutrient Watershed Regions (NWR) 

used to derive instream protection 

values (IPVs). It is important to note that 

the scale at which protective loads and 

DPVs were derived is smaller than for 

IPVs (i.e., 16 estuarine watersheds vs. 4 

nutrient watershed regions). EPA’s 

recognition that some fraction of 

nitrogen transported in streams is 

retained or assimilated before reaching 

estuarine waters help ensure that the 

DPVs are not overprotective of 

downstream use in any particular 

estuary. 

In determining TN DPVs, EPA 

considered the contribution of TN 

inputs from wastewater discharged in 

shoreline catchments directly to the 

estuary. EPA found these point source 

inputs to be significant (> 5% of total 

loading) in three (St. Andrew’s Bay, St. 

Marys, St. John’s) of the 16 estuaries. 

However, for the purpose of computing 

stream reach DPVs for a given estuarine 

watershed, EPA considered only those 

TN loads delivered from the estuarine 

watershed stream network and did not 

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86Hoos, A.B., S. Terziotti, G. McMahon, K. 

Savvas, K.C. Tighe, and R. Alkons-Wolinsky. 2008. 

Data to support statistical modeling of instream 

nutrient load based on watershed attributes, 

southeastern United States, 2002: U.S. Geological 

Survey Open-File Report 2008—1163, 50 p. 

include TN inputs from wastewater 

discharged in shoreline catchments 

directly to an estuary because these 

loads do not originate from upstream 

sources. However, point sources loads 

directly to the estuary would need to be 

considered in developing TMDLs based 

on estuary-specific criteria. 

EPA’s computation of DPVs using 

estimates of protective loading for each 

estuary and the fraction-delivered to 

estuaries is shown by equation (1): 

C kL

Q F i est

W i

= 1 , (1)

where the terms are defined as follows for a 

specific or (ith) stream reach: 

C ̄ i maximum flow-averaged nutrient 

concentration for a specific (the ith) 

stream reach consistent with 

downstream use protection (i.e., the 

DPV) 

k fraction of all loading to the estuary that 

comes from the stream network resolved 

by SPARROW 

Lest protective loading rate for the estuary, 

from all sources 

Q ̄ W combined average freshwater 

discharged into the estuary from the 

portion of the watershed resolved by the 

SPARROW stream network 

Fi fraction of the flux at the downstream 

node of the specific (ith) reach that is 

transported through the stream network 

and ultimately delivered to estuarine 

receiving waters (i.e., Fraction 

Delivered). 

Note that the quantity kLest is equal 

to the loading to the estuary from 

sources resolved by SPARROW. For the 

purposes of practical implementation, 

EPA classified each stream water body 

(i.e., Water Body Identification or 

‘‘WBID’’ using the FDEP term) according 

to the estuarine receiving water and one 

of six categories based on the fraction of 

TN delivered (0 to 50%, 51–60%, 61– 

70%, 71–80%, 81–90%, and 91–100%). 

For each category, the upper end of the 

range was utilized to compute the 

applicable DPV for streams in the 

category, resulting in a value that will 

be protective. This approach reduces the 

number of unique DPVs from thousands 

to less than 100. Because the stream 

network utilized by the SAGT– 

SPARROW watershed model (ERF1) 

does not recognize all of the smaller 

streams in Florida (i.e., it is on a larger 

scale), EPA mapped WBIDs to the 

applicable watershed-scale unit, or 

‘‘incremental watersheds,’’ of the ERF1 

reaches, assigning to each WBID the 

fraction of TN delivered estimated for 

the ERF1 reach whose incremental 

watershed includes the WBID. Where 

the WBID includes portions of the 

incremental watersheds of more than 

one ERF1 reach, EPA computed a 

weighted-average based on the 

proportion of WBID area in the 

watershed of each ERF1 reach. 

Given an even distribution of reaches 

within each 10% interval, EPA’s 

‘‘binning’’ approach to the fractiondelivered estimates results in a 5% to 

10% margin of safety for the average 

reach in each range (closer to 10% for 

the lower fraction-delivered ranges). 

Potentially larger margins are possible 

within the 0 to 50% range, where the 

fraction delivered might be 20%, but the 

DPV would be computed assuming a 

fraction delivered of 50%. However, 

only one watershed in Florida for which 

EPA is proposing DPVs, the St. Johns 

River, has a substantial number of 

reaches estimated to have less than 50% 

TN delivered to estuarine waters. The 

SAGT–SPARROW watershed model 

estimates that 17% of the stream reaches 

in the St. Johns watershed are in this 

category, with about half the reaches 

delivering nearly 50% of TN and a 

substantial number delivering only 20% 

of TN. Given EPA’s DPV for terminal 

reaches in the St. Johns watershed, 

however, the DPV for reaches with a 

fraction delivered less than 50% will be 

higher than the IPV, and therefore, will 

not apply. EPA requests comment on 

the binning approach for calculating 

DPVs, which allows for a relatively 

simple table of DPVs to be presented as 

compared to using the actual estimate of 

fraction TN delivered to calculate a DPV 

unique to each WBID using formula (1), 

above. 

At this time, EPA has not calculated 

protective TP loads for Florida’s 

estuaries or DPVs for TP. However, 

advances in the application of regional 

watershed models, such as SPARROW, 

that address the sources and terrestrial 

and aquatic processes that influence the 

supply and transport of TP in the 

watershed and delivery to estuaries are 

currently in advanced stages of 

development.86 EPA anticipates 

obtaining the necessary data and 

information to compute TP loads for the 

estuarine water bodies in Florida in 

2010 and could make this additional 

information available by issuing a 

supplemental Federal Register Notice of 

Data Availability (NODA), which would 

also be posted in the public docket for 

this proposed rule. EPA intends to 

derive proposed protective loads and 

DPVs for TP using an analogous 

approach as used for TN DPVs. EPA 

expects the approach will recognize that 

TP, like TN, is essential for estuarine 

processes but in excess will adversely 

impact aquatic life uses. 

(iv) EPA Downstream Protection Values 

(DPVs) 

The following criteria tables and 

corresponding DPVs for a given stream 

reach category have been geo-referenced 

to specific WBIDs which are managed 

by FDEP as the principal assessment 

unit for Florida’s surface waters. To see 

where the criteria are geographically 

applicable, refer to EPA’s TSD for 

Florida’s Inland Waters, Appendix 

B–18: In-Stream and Downstream 

Protection Value (IPV/DPV) Tables with 

DPV Geo-Reference Table to Florida 

WBIDs. 

River/stream reach category—percent delivered to estuary 4

(mg L¥1) TP (mg L¥1) 

TN IPV5 TN DPV6 TP IPV7 TP DPV8

Perdido Bay Watershed PH (EDA Code: 1 G140x) 

Protective TN Load for the Estuary: 2: 847,520 kg y¥1

Protective TP Load for the Estuary: 3 TBD 

Less than 50% ................................................................................................. NR NR 0.043 TBD 

50.1–60.0% ...................................................................................................... NR NR 0.043 TBD 

60.1–70.0% ...................................................................................................... NR NR 0.043 TBD 

70.1–80.0% ...................................................................................................... NR NR 0.043 TBD 

80.1–90.0% ...................................................................................................... 0.824 0.34 0.043 TBD 

90.1–100% ....................................................................................................... 0.824 0.30 0.043 TBD 


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River/stream reach category—percent delivered to estuary 4

(mg L¥1) TP (mg L¥1) 

TN IPV5 TN DPV6 TP IPV7 TP DPV8

Pensacola Bay Watershed PH (EDA Code: 1 G130x) 

Protective TN Load for the Estuary: 2 4,388,478 kg y¥1

Protective TP Load for the Estuary: 3 TBD 

Less than 50% ................................................................................................. NR NR 0.043 TBD 

50.1–60.0% ...................................................................................................... NR NR 0.043 TBD 

60.1–70.0% ...................................................................................................... NR NR 0.043 TBD 

70.1–80.0% ...................................................................................................... NR NR 0.043 TBD 

80.1–90.0% ...................................................................................................... 0.824 0.48 0.043 TBD 

90.1–100% ....................................................................................................... 0.824 0.43 0.043 TBD 

Choctawhatchee Bay Watershed PH (EDA Code: 1 G120x) 

Protective TN Load for the Estuary: 2 2,875,861 kg y¥1

Protective TP Load for the Estuary: 3 TBD 

Less than 50% ................................................................................................. NR NR 0.043 TBD 

50.1–60.0% ...................................................................................................... NR NR 0.043 TBD 

60.1–70.0% ...................................................................................................... NR NR 0.043 TBD 

70.1–80.0% ...................................................................................................... 0.824 0.48 0.043 TBD 

80.1–90.0% ...................................................................................................... 0.824 0.43 0.043 TBD 

90.1–100% ....................................................................................................... 0.824 0.39 0.043 TBD 

St. Andrew Bay Watershed PH (EDA Code: 1 G110x) 

Protective TN Load for the Estuary: 2 310,322 kg y¥1

Protective TP Load for the Estuary: 3 TBDK 

Less than 50% ................................................................................................. 0.824 0.48 0.043 TBD 

50.1–60.0% ...................................................................................................... NR NR 0.043 TBD 

60.1–70.0% ...................................................................................................... NR NR 0.043 TBD 

70.1–80.0% ...................................................................................................... 0.824 0.30 0.043 TBD 

80.1–90.0% ...................................................................................................... 0.824 0.27 0.043 TBD 

90.1–100% ....................................................................................................... 0.824 0.24 0.043 TBD 

Apalachicola Bay Watershed PH (EDA Code: 1 G100x) 

Protective TN Load for the Estuary: 2 10,971,582 kg y¥1

Protective TP Load for the Estuary: 3 TBD 

Less than 50% ................................................................................................. 0.824 0.91 0.043 TBD 

50.1–60.0% ...................................................................................................... NR NR 0.043 TBD 

60.1–70.0% ...................................................................................................... 0.824 0.65 0.043 TBD 

70.1–80.0% ...................................................................................................... 0.824 0.57 0.043 TBD 

80.1–90.0% ...................................................................................................... 0.824 0.51 0.043 TBD 

90.1–100% ....................................................................................................... 0.824 0.46 0.043 TBD 

Apalachee Bay Watershed PH (EDA Code: 1 G090x) 

Protective TN Load for the Estuary: 2 2,539,883 kg y¥1

Protective TP Load for the Estuary: 3 TBD 

Less than 50% ................................................................................................. NR NR 0.043 TBD 

50.1–60.0% ...................................................................................................... NR NR 0.043 TBD 

60.1–70.0% ...................................................................................................... NR NR 0.043 TBD 

70.1–80.0% ...................................................................................................... 0.824 0.67 0.043 TBD 

80.1–90.0% ...................................................................................................... 0.824 0.59 0.043 TBD 

90.1–100% ....................................................................................................... 0.824 0.53 0.043 TBD 

Econfina/Steinhatchee Coastal Drainage Area PH (CDA Code: 1 G086x) 

Protective TN Load for the Estuary: 2 185,301 kg y¥1

Protective TP Load for the Estuary: 3 TBD 

Less than 50% ................................................................................................. NR NR 0.043 TBD 

50.1–60.0% ...................................................................................................... NR NR 0.043 TBD 

60.1–70.0% ...................................................................................................... NR NR 0.043 TBD 

70.1–80.0% ...................................................................................................... NR NR 0.043 TBD 

80.1–90.0% ...................................................................................................... 0.824 0.41 0.043 TBD 

90.1–100% ....................................................................................................... 0.824 0.37 0.043 TBD 

Suwannee River WatershedNC (EDA Code: 1G080x) 

Protective TN Load for the Estuary: 2 5,421,050 kg y¥1

Protective TP Load for the Estuary: 3 TBD 

Less than 50% ................................................................................................. NR NR 0.359 TBD 

50.1–60.0% ...................................................................................................... NR NR 0.359 TBD 

60.1–70.0% ...................................................................................................... 1.479 0.78 0.359 TBD 

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River/stream reach category—percent delivered to estuary 4

(mg L¥1) TP (mg L¥1) 

TN IPV5 TN DPV6 TP IPV7 TP DPV8

70.1–80.0% ...................................................................................................... 1.479 0.69 0.359 TBD 

80.1–90.0% ...................................................................................................... 1.479 0.61 0.359 TBD 

90.1–100% ....................................................................................................... 1.479 0.55 0.359 TBD 

Waccasassa Coastal Drainage Area PN (CDA Code: 1 078x) 

Protective TN Load for the Estuary: 2 433,756 kg y¥1

Protective TP Load for the Estuary: 3 TBD 

Less than 50% ................................................................................................. NR NR 0.107 TBD 

50.1–60.0% ...................................................................................................... NR NR 0.107 TBD 

60.1–70.0% ...................................................................................................... NR NR 0.107 TBD 

70.1–80.0% ...................................................................................................... NR NR 0.107 TBD 

80.1–90.0% ...................................................................................................... 1.205 0.45 0.107 TBD 

90.1–100% ....................................................................................................... 1.205 0.40 0.107 TBD 

Withlacoochee Coastal Drainage Area PN (CDA Code: 1 G076x) 

Protective TN Load for the Estuary: 2 TBD 

Protective TP Load for the Estuary: 3 TBD 

Less than 50% ................................................................................................. 1.205 TBD 0.107 TBD 

50.1–60.0% ...................................................................................................... 1.205 TBD 0.107 TBD 

60.1–70.0% ...................................................................................................... 1.205 TBD 0.107 TBD 

70.1–80.0% ...................................................................................................... 1.205 TBD 0.107 TBD 

80.1–90.0% ...................................................................................................... 1.205 TBD 0.107 TBD 

90.1–100% ....................................................................................................... 1.205 TBD 0.107 TBD 

Crystal/Pithlachascotee Coastal Drainage Area PN (CDA Code: 1 G074x) 

Protective TN Load for the Estuary: 2 TBD 

Protective TP Load for the Estuary: 3 TBD 

Less than 50% ................................................................................................. 1.205 TBD 0.107 TBD 

50.1–60.0% ...................................................................................................... NR TBD 0.107 TBD 

60.1–70.0% ...................................................................................................... NR TBD 0.107 TBD 

70.1–80.0% ...................................................................................................... NR TBD 0.107 TBD 

80.1–90.0% ...................................................................................................... 1.205 TBD 0.107 TBD 

90.1–100% ....................................................................................................... 1.205 TBD 0.107 TBD 

Tampa Bay Watershed BV (EDA Code: 1 G070x) 

Protective TN Load for the Estuary: 2 1,289,671 kg y¥1

Protective TP Load for the Estuary: 3 TBD 

Less than 50% ................................................................................................. 1.798 1.11 0.739 TBD 

50.1–60.0% ...................................................................................................... 1.798 0.93 0.739 TBD 

60.1–70.0% ...................................................................................................... 1.798 0.80 0.739 TBD 

70.1–80.0% ...................................................................................................... 1.798 0.70 0.739 TBD 

80.1–90.0% ...................................................................................................... 1.798 0.62 0.739 TBD 

90.1–100% ....................................................................................................... 1.798 0.56 0.739 TBD 

Sarasota Bay Watershed BV (EDA Code: 1 G060x) 

Protective TN Load for the Estuary: 2 155,576 kg y¥1

Protective TP Load for the Estuary: 3 TBD 

Less than 50% ................................................................................................. NR NR 0.739 TBD 

50.1–60.0% ...................................................................................................... NR NR 0.739 TBD 

60.1–70.0% ...................................................................................................... NR NR 0.739 TBD 

70.1–80.0% ...................................................................................................... NR NR 0.739 TBD 

80.1–90.0% ...................................................................................................... NR NR 0.739 TBD 

90.1–100% ....................................................................................................... 1.798 0.54 0.739 TBD 

Charlotte Harbor Watershed BV (EDA Code: 1 G050w) 

Protective TN Load for the Estuary: 2 2,710,107 kg y¥1

Protective TP Load for the Estuary: 3 TBD 

Less than 50% ................................................................................................. NR NR 0.739 TBD 

50.1–60.0% ...................................................................................................... 1.798 1.58 0.739 TBD 

60.1–70.0% ...................................................................................................... 1.798 1.35 0.739 TBD 

70.1–80.0% ...................................................................................................... 1.798 1.18 0.739 TBD 

80.1–90.0% ...................................................................................................... 1.798 1.05 0.739 TBD 

90.1–100% ....................................................................................................... 1.798 0.95 0.739 TBD 

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River/stream reach category—percent delivered to estuary 4

(mg L¥1) TP (mg L¥1) 

TN IPV5 TN DPV6 TP IPV7 TP DPV8

Indian River Watershed PN (EDA Code: 1 S190x) 

Protective TN Load for the Estuary: 2 463,724 kg y¥1

Protective TP Load for the Estuary: 3 TBD 

Less than 50% ................................................................................................. NR NR 0.107 TBD 

50.1–60.0% ...................................................................................................... NR NR 0.107 TBD 

60.1–70.0% ...................................................................................................... NR NR 0.107 TBD 

70.1–80.0% ...................................................................................................... 1.205 0.87 0.107 TBD 

80.1–90.0% ...................................................................................................... 1.205 0.77 0.107 TBD 

90.1–100% ....................................................................................................... 1.205 0.69 0.107 TBD 

Caloosahatchee River Watershed PN,# (EDA Code: 1 G050a) 

Protective TN Load for the Estuary: 2 TBD 

Protective TP Load for the Estuary: 3 TBD 

Less than 50% ................................................................................................. 1.205 TBD 0.107 TBD 

50.1–60.0% ...................................................................................................... 1.205 TBD 0.107 TBD 

60.1–70.0% ...................................................................................................... 1.205 TBD 0.107 TBD 

70.1–80.0% ...................................................................................................... 1.205 TBD 0.107 TBD 

80.1–90.0% ...................................................................................................... 1.205 TBD 0.107 TBD 

90.1–100% ....................................................................................................... 1.205 TBD 0.107 TBD 

St. Lucie River Watershed PN,# (EDA Code: 1 S190x) 

Protective TN Load for the Estuary: 2 TBD 

Protective TP Load for the Estuary: 3 TBD 

Less than 50% ................................................................................................. 1.205 TBD 0.107 TBD 

50.1–60.0% ...................................................................................................... 1.205 TBD 0.107 TBD 

60.1–70.0% ...................................................................................................... 1.205 TBD 0.107 TBD 

70.1–80.0% ...................................................................................................... 1.205 TBD 0.107 TBD 

80.1–90.0% ...................................................................................................... 1.205 TBD 0.107 TBD 

90.1–100% ....................................................................................................... 1.205 TBD 0.107 TBD 

Kissimmee River Watershed PN,∧ 

Protective TN Load for the Estuary: 2 TBD 

Protective TP Load for the Estuary: 3 TBD 

Less than 50% ................................................................................................. 1.205 TBD 9 0.107 TBD 9

50.1–60.0% ...................................................................................................... 1.205 TBD 9 0.107 TBD 9

60.1–70.0% ...................................................................................................... 1.205 TBD 9 0.107 TBD 9

70.1–80.0% ...................................................................................................... 1.205 TBD 9 0.107 TBD 9

80.1–90.0% ...................................................................................................... 1.205 TBD 9 0.107 TBD 9

90.1–100% ....................................................................................................... 1.205 TBD 9 0.107 TBD 9

St. John’s River Watershed; PN (EDA Code: 1 S180x) 

Protective TN Load for the Estuary: 2 4,954,662 kg y¥1

Protective TP Load for the Estuary: 3 TBD 

Less than 50% ................................................................................................. 1.205 1.41 0.107 TBD 

50.1–60.0% ...................................................................................................... 1.205 1.17 0.107 TBD 

60.1–70.0% ...................................................................................................... 1.205 1.00 0.107 TBD 

70.1–80.0% ...................................................................................................... 1.205 0.88 0.107 TBD 

80.1–90.0% ...................................................................................................... 1.205 0.78 0.107 TBD 

90.1–100% ....................................................................................................... 1.205 0.70 0.107 TBD 

Daytona/St. Augustine Coastal Drainage Area PN (CDA Code: 1 S183x) 

Protective TN Load for the Estuary: 2 TBD 

Protective TP Load for the Estuary: 3 TBD 

Less than 50% ................................................................................................. NR TBD 0.107 TBD 

50.1–60.0% ...................................................................................................... NR TBD 0.107 TBD 

60.1–70.0% ...................................................................................................... NR TBD 0.107 TBD 

70.1–80.0% ...................................................................................................... NR TBD 0.107 TBD 

80.1–90.0% ...................................................................................................... 1.205 TBD 0.107 TBD 

90.1–100% ....................................................................................................... 1.205 TBD 0.107 TBD 

Nassau Coastal Drainage Area PN (CDA Code: 1 S175x) 

Protective TN Load for the Estuary: 2 131,389 kg y¥1

Protective TP Load for the Estuary: 3 TBD 

Less than 50% ................................................................................................. 1.205 0.59 0.107 TBD 

50.1–60.0% ...................................................................................................... NR NR 0.107 TBD 

60.1–70.0% ...................................................................................................... NR NR 0.107 TBD 

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River/stream reach category—percent delivered to estuary 4

(mg L¥1) TP (mg L¥1) 

TN IPV5 TN DPV6 TP IPV7 TP DPV8

70.1–80.0% ...................................................................................................... NR NR 0.107 TBD 

80.1–90.0% ...................................................................................................... 1.205 0.33 0.107 TBD 

90.1–100% ....................................................................................................... 1.205 0.30 0.107 TBD 

St. Mary’s River Watershed PN (EDA Code: 1 S170x) 

Protective TN Load for the Estuary: 2 562,644 kg y¥1

Protective TP Load for the Estuary: 3 TBD 

Less than 50% ................................................................................................. NR NR 0.107 TBD 

50.1–60.0% ...................................................................................................... NR NR 0.107 TBD 

60.1–70.0% ...................................................................................................... NR NR 0.107 TBD 

70.1–80.0% ...................................................................................................... 1.205 0.43 0.107 TBD 

80.1–90.0% ...................................................................................................... 1.205 0.38 0.107 TBD 

90.1–100% ....................................................................................................... 1.205 0.34 0.107 TBD 

Footnotes associated with this table: 

1 Watershed delineated by NOAA’s Coastal Assessment Framework and associated Florida Department of Environmental Protection’s estuarine and coastal water body identifier (WBID). 2 Estimated TN load delivered to the estuary protective of aquatic life use. These estimates may be revised pursuant to the EPA final rule for 

numeric nutrient criteria for Florida’s estuaries and coastal waters (October 2011). 3 Estimated TP load delivered to the estuary protective of aquatic life use. These estimates are currently under development. Preliminary estimates may be revised pursuant to the EPA final rule for numeric nutrient criteria for Florida’s estuaries and coastal waters (October 2011). 4 River/Stream reach categories within each estuarine watershed are linked spatially to a specific FDEP water body identifier (WBID). See Appendix B–18 of the ‘‘Technical Support Document for EPA’s Proposed Rule for Numeric Nutrient Criteria for Florida’s Inland Surface Fresh Waters.’’ 5 Instream Protection Value (IPV) is the TN concentration protective of instream aquatic life use. 6 Downstream protection values (DPVs) are estimated TN concentrations in the river/stream reach that meet the estimated TN load, protective 

of aquatic life use, delivered to the estuarine waters. These estimates may be revised pursuant to the EPA final rule for numeric nutrient criteria 

for Florida’s estuaries and coastal waters (October 2011). 7 Instream Protection Value (IPV) is the TP concentration protective of instream aquatic life use. 8 Downstream protection values (DPVs) are estimated TP concentrations in the river/stream reach that meet the estimated TP load, protective 

of aquatic life use, delivered to the estuarine waters. These estimates are currently under development. Preliminary estimates may be revised 

pursuant to the EPA final rule for numeric nutrient criteria for Florida’s estuaries and coastal waters (October 2011). 9 EPA’s proposed TN and TP criteria for colored lakes (>40 PCU) are 1.2 and 0.050 mg L¥1, respectively. 

# Estimated TN and TP loads protective of aquatic life in the Caloosahatchee and St. Lucie River estuaries, and in turn estimated TN and TP 

concentrations that would meet those protective loads, could not be calculated using EPA’s downstream protection approach. An alternative 

downstream protection approach will be proposed in EPA’s proposed rule for FL estuaries (January 2011). 

∧ Kissimmee River watershed does not have an EDA or CDA code because it does not drain directly to an estuary or coastal area, but rather 

indirectly through Lake Okeechobee and the south Florida canal system. 

A protective TN and TP load for Lake Okeechobee has not been calculated, however, a TMDL is in effect for TP. EPA’s proposed colored lake 

criteria (> 40 PCU) could be used to develop DPVs for TN and TP for the Kissimmee watershed (see footnote 9). LO DPVs to be based on protective TN and TP loads for Lake Okeechobee. EPA’s proposed colored lake criteria (>40 PCU) could be used to 

develop DPVs for TN and TP for the Kissimmee watershed (see footnote 9). NR There are no stream reaches present in this watershed that have a percent-delivered within this range and thus criteria are not applicable. PH Panhandle Nutrient Watershed Region. BV Bone Valley Nutrient Watershed Region. PN Peninsula Nutrient Watershed Region. NC North Central Nutrient Watershed Region. TBD To be determined. 

(v) Application of DPVs for Downstream 

Estuary Protection 

The following discussion further 

explains the conceptual relationship 

between IPVs and DPVs for stream 

criteria. EPA developed IPVs to protect 

the uses that occur within the stream 

itself at the point of application, such as 

protection of the benthic invertebrate 

community and maintenance of a 

healthy balance of phytoplankton 

species. In contrast, EPA developed 

DPVs for streams to protect WQS of 

downstream waters. EPA derived DPVs 

in Florida streams by distributing the 

protective load from the aggregate 

stream network identified for each 

downstream estuary (that is protective 

of estuarine conditions) across the 

watershed in proportion to the amount 

of flow contributed by each stream 

reach. EPA’s approach also accounts for 

attenuation of nutrients (or loss from the 

system) as water travels from locations 

upstream in the watershed to locations 

near the mouth of the estuary. 

When comparing an IPV and DPV that 

are each deemed to apply to a particular 

stream segment, the more stringent of 

the two values is the numeric nutrient 

criterion that would need to be met 

when implementing CWA programs. 

Water bodies can differ significantly in 

their sensitivity to nutrients in general 

and to TN specifically. Although not 

universally true, freshwaters are 

generally phosphorus-limited and thus 

more sensitive to phosphorus 

enrichment because nitrogen is present 

in excess. Enriching freshwaters with 

phosphorus does not usually drive these 

systems into nitrogen limitation but can 

simply encourage growth of nitrogenfixing algal species which can convert 

atmospheric nitrogen into ammonia. 

Conversely, estuaries are more often 

nitrogen limited and thus more sensitive 

to adverse impacts from nitrogen 

enrichment. As a result, it is not at all 

surprising that DPVs for TN in Florida 

are often less than the corresponding 

IPVs. 

Adjustments to DPVs are possible 

with a redistribution approach, which 

revises the original uniform assignment 

of protective downstream estuarine 

loadings across the estuarine drainage 

area using the DPV methodology, or by 

revising either the protective load 

delivered to the downstream estuary 

and/or the equivalent DPVs using a 

technical approach of comparable 

scientific rigor and the Federal SSAC 

procedure described in section V.C of 

this notice. 

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4208 Federal Register / Vol. 75, No. 16 / Tuesday, January 26, 2010 / Proposed Rules 

87Brown M.T., K. Chinners Reiss, M.J. Cohen, 

J.M. Evans, P.W. Inglett, K. Sharma Inglett, K. 

Ramesh Reddy, T.K. Fraze, C.A. Jacoby, E.J. Phlips, 

R.L. Knight, S.K. Notestein, R.G. Hamann, and K.A. 

McKee. 2008. Summary and Synthesis of the 

Available Literature on the Effects of Nutrients on 

Spring Organisms and Systems. http:// 

www.dep.state.fl.us/springs/reports/files/ 

UF_SpringsNutrients_Report.pdf, University of 

Florida, Gainesville, Florida. 

88Scott, T.M., G.H. Means, R.P. Meegan, R.C. 

Means, S.B. Upchurch, R.E. Copeland, J. Jones, T. 

Roberts, and A. Willet. 2004. Springs of Florida. 

Bulletin No, 66. Florida Geological Survey. 

Tallahassee, FL. 677 pp. 

89 Katz, B.G., H.D. Hornsby, J.F. Bohlke and M.F. 

Mokray. 1999. Sources and chronology of nitrate 

contamination in spring water, Suwannee River 

Basin, Florida. U.S. Geological Survey WaterResources Investigations Report 99–4252. Reston, 

VA. 

90Brown M.T., K. Chinners Reiss, M.J. Cohen, 

J.M. Evans, P.W. Inglett, K. Sharma Inglett, K. 

Ramesh Reddy, T.K. Fraze, C.A. Jacoby, E.J. Phlips, 

R.L. Knight, S.K. Notestein, R.G. Hamann, and K.A. 

McKee. 2008. Summary and Synthesis of the 

Available Literature on the Effects of Nutrients on 

Spring Organisms and Systems. http:// 

www.dep.state.fl.us/springs/reports/files/ 

UF_SpringsNutrients_Report.pdf, University of 

Florida, Gainesville, Florida. 

91 Ibid. 

92 Katz, B.G., H.D. Hornsby, J.F. Bohlke and M.F. 

Mokray. 1999. Sources and chronology of nitrate 

contamination in spring water, Suwannee River 

Basin, Florida. U.S. Geological Survey WaterResources Investigations Report 99–4252. Reston, 

VA. 

93 Doyle, R.D. and R.M. Smart. 1998. Competitive 

reduction of noxious Lyngbya wollei mats by rooted 

aquatic plants. Aquatic Botany 61:17–32. 

94Stevenson, R.J., A. Pinowska, A. Albertin, and 

J.O. Sickman. 2007. Ecological condition of algae 

and nutrients in Florida springs: The Synthesis 

Report. Prepared for the Florida Department of 

Environmental Protection. Tallahassee, FL. 58 pp. 

Bonn, M.A. and F.W. Bell. 2003. Economic 

Impact of Selected Florida Springs on Surrounding 

Local Areas. Report prepared for the Florida 

Department of Environmental Protection. 

Tallahassee, FL. 

Re-distributing the allocation of 

protective loading within an estuarine 

drainage area, or subset of an estuarine 

drainage area, is appropriate and 

protective because the total load 

delivered to the mouth of the estuary 

would still meet the protective load. 

DPVs may be a series of values for each 

reach in the upstream drainage area 

such that the sum of reach-specific 

incremental loading delivered to the 

estuary equals the protective loading 

rate taking into account that 

downstream reaches must reflect loads 

established for upstream reaches. 

Adjustments to DPVs may also factor in 

additional nutrient attenuation provided 

by already existing landscape 

modifications or treatment systems, 

such as constructed wetlands or 

stormwater treatment areas, where the 

attenuation is sufficiently documented 

and not a temporary condition. Unlike 

re-allocation of an even distribution of 

loading, these types of adjustments, as 

well as other site-specific information 

on alternative fractions delivered, 

would require use of the SSAC 

procedure under this proposal. EPA 

requests comment on whether these 

adjustments should be allowed to occur 

in the implementation of the reallocation process rather than as a 

SSAC. 

A technical approach of comparable 

scientific rigor will include a systematic 

data driven evaluation and 

accompanying analysis of relevant 

factors to identify a protective load 

delivered to the estuary. An acceptable 

alternate numeric approach also 

includes a method to distribute and 

apply the load to streams and other 

waters within the estuarine drainage 

area in a manner that recognizes 

conservation of mass and makes use of 

a peer-reviewed model (empirical or 

mechanistic) of comparable or greater 

rigor and scientific defensibility than 

the USGS SPARROW model. To use an 

alternative technical approach, the State 

must go through the process for a 

Federal SSAC procedure as described in 

Section V.C. 

EPA requests comment on the DPV 

approach, the technical merit of the 

estimated protective loadings, and the 

technical merit of the method for 

calculating stream reach values. EPA 

also requests comment on other 

scientifically defensible approaches for 

ensuring protection of designated uses 

in estuaries. At this time, EPA plans to 

take final action with respect to 

downstream protection values for 

nitrogen as part of the second phase of 

this rulemaking process in coordination 

with the proposal and finalization of 

numeric standards for estuarine and 

coastal waters in 2011. However, if 

comments, data and analyses submitted 

as a result of this proposal support 

finalizing these values sooner, by 

October 2010, EPA may choose to 

proceed in this manner. To facilitate 

this process, EPA requests comments 

and welcomes thorough evaluation on 

the technical and scientific basis of 

these proposed downstream protection 

values as part of the broader comment 

and evaluation process that this 

proposal initiates. 

D. Proposed Numeric Nutrient Criteria 

for the State of Florida’s Springs and 

Clear Streams 

(1) Proposed Numeric Nutrient Criteria 

for Springs and Clear Streams 

Springs and their associated spring 

runs in Florida are a unique class of 

aquatic ecosystem, highly treasured for 

their biological, economic, aesthetic, 

and recreational value. Globally, the 

largest number of springs (per unit of 

area), occur in Florida; Florida has over 

700 springs and associated spring runs. 

Many of the larger spring ecosystems in 

Florida have likely been in existence 

since the end of the last major ice age 

(approximately 15,000 to 30,000 years 

ago). The productivity of the diverse 

assemblage of aquatic flora and fauna in 

Florida springs is primarily determined 

by the naturally high amount of light 

availability of these waters (naturally 

high clarity).87 As recently as 50 years 

ago, these waters were considered by 

naturalists and scientists to be some of 

the most unique and exceptional waters 

in the State of Florida and the Nation as 

a whole. 

In Florida, springs are also highly 

valued as a water resource for human 

use: people use springs for a variety of 

recreational purposes and are interested 

in the intrinsic aesthetics of clear, cool 

water emanating vigorously from 

beneath the ground. A good example of 

the value of springs in Florida is the use 

of the spring boil areas that have 

sometimes been modified to encourage 

human recreation (bathing or 

swimming).88

Over the past two decades, scientists 

have identified two significant 

anthropogenic factors linked to adverse 

changes in spring ecosystems that have 

the potential to permanently alter 

Florida’s spring ecosystems. These are: 

(1) Pollution of groundwater,89

principally with nitrate-nitrite, resulting 

from human land use changes, cultural 

practices, and explosive population 

growth; and (2) simultaneous reductions 

in groundwater supply from human 

withdrawals.90 Pollution associated 

with human activities is one of the most 

critical issues affecting the health of 

Florida’s springs.91

Excess nutrients, in particular excess 

nitrogen, seep into the soils and move 

to groundwater.92 When in excess, 

nutrients lead to eutrophication of 

groundwater-fed springs, allowing algae 

and invasive plant species to displace 

native plants, which in turn results in 

an ecological imbalance.93 Excessive 

growth of nuisance algae and noxious 

plant species in turn result in reduced 

habitat and food sources for native 

wildlife,94 excess organic carbon 

production, accelerated decomposition, 

and lowered quality of the floor or 

‘‘bottom’’ of springs and spring runs, all 

of which adversely impact the overall 

health and aesthetics of Florida’s 

springs. 

Adverse impacts on the overall health 

of Florida’s springs have been evident 

over the past several decades. Within 

the last 20–30 years, observations at 

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95Pinowska, A., R.J. Stevenson, J.O. Sickman, A. 

Albertin, and M. Anderson. 2007. Integrated 

interpretation of survey for determining nutrient 

thresholds for macroalgae in Florida Springs: 

Macroalgal relationships to water, sediment and 

macroalgae nutrients, diatom indicators and land 

use. Florida Department of Environmental 

Protection, Tallahassee, FL. 

96Stevenson, R.J., A. Pinowska, and Y.K. Wang. 

2004. Ecological condition of algae and nutrients in 

Florida springs. Florida Department of 

Environmental Protection, Tallahassee, FL. 

97Scott, T.M., G.H. Means, R.P. Meegan, R.C. 

Means, S.B. Upchurch, R.E. Copeland, J. Jones, T. 

Roberts, and A. Willet. 2004. Springs of Florida. 

Bulletin No, 66. Florida Geological Survey. 

Tallahassee, FL. 677 pp. 

98Maddox, G.L., J.M. Lloyd, T.M. Scott, S.B. 

Upchurch and R. Copeland. 1992. Florida’s 

Groundwater Quality Monitoring Program— 

Background Hydrochemistry. Florida Geological 

Survey Special Publication 34. Tallahassee, FL. 

99 Katz, B.G., H.D. Hornsby, J.F. Bohlke and M.F. 

Mokray. 1999. Sources and chronology of nitrate 

contamination in spring water, Suwannee River 

Basin, Florida. U. S. Geological Survey WaterResources Investigations Report 99–4252. Reston, 

VA. 

Brown M.T., K. Chinners Reiss, M.J. Cohen, J.M. 

Evans, P.W. Inglett, K. Sharma Inglett, K. Ramesh 

Reddy, T.K. Fraze, C.A. Jacoby, E.J. Phlips, R.L. 

Knight, S.K. Notestein, R.G. Hamann, and K.A. 

McKee. 2008. Summary and Synthesis of the 

Available Literature on the Effects of Nutrients on 

Spring Organisms and Systems. http:// 

www.dep.state.fl.us/springs/reports/files/ 

UF_SpringsNutrients_Report.pdf, University of 

Florida, Gainesville, Florida. 

100Scott, T.M., G.H. Means, R.P. Meegan, R.C. 

Means, S.B. Upchurch, R.E. Copeland, J. Jones, T. 

Roberts, and A. Willet. 2004. Springs of Florida. 

Bulletin No, 66. Florida Geological Survey. 

Tallahassee, FL. 677 pp. 

101Brown M.T., K. Chinners Reiss, M.J. Cohen, 

J.M. Evans, P.W. Inglett, K. Sharma Inglett, K. 

Ramesh Reddy, T.K. Fraze, C.A. Jacoby, E.J. Phlips, 

R.L. Knight, S.K. Notestein, R.G. Hamann, and K.A. 

McKee. 2008. Summary and Synthesis of the 

Available Literature on the Effects of Nutrients on 

Spring Organisms and Systems. http:// 

www.dep.state.fl.us/springs/reports/files/ 

UF_SpringsNutrients_Report.pdf, University of 

Florida, Gainesville, Florida. 

102Brown M.T., K. Chinners Reiss, M.J. Cohen, 

J.M. Evans, P.W. Inglett, K. Sharma Inglett, K. 

Ramesh Reddy, T.K. Fraze, C.A. Jacoby, E.J. Phlips, 

R.L. Knight, S.K. Notestein, R.G. Hamann, and K.A. 

McKee. 2008. Summary and Synthesis of the 

Available Literature on the Effects of Nutrients on 

Spring Organisms and Systems. http:// 

www.dep.state.fl.us/springs/reports/files/ 

UF_SpringsNutrients_Report.pdf, University of 

Florida, Gainesville, Florida. 

several of Florida’s springs suggest that 

nuisance algae species have 

proliferated, and are now out-competing 

and replacing native submerged 

vegetation. Numerous biological studies 

have documented excessive algal 

growth at many major springs. In some 

of the more extreme examples, such as 

Silver Springs and Weeki Wachee 

Springs, algal mat accumulations have 

become over three feet thick.95,96

As a result of human-induced land 

use changes, cultural practices, and 

explosive population growth, there has 

been an increase in the level of 

pollutants, especially nitrate, in 

groundwater over the past decades.97

Because there is no geologic source of 

nitrogen in springs, all of the nitrogen 

emerging in spring vents originates from 

that which is deposited on the land. 

Historically, nitrate concentrations in 

Florida’s spring discharges were thought 

to have been around 0.05 mg/L or less, 

which is sufficiently low to restrict 

growth of algae and vegetation under 

‘‘natural’’ conditions.98

Regions where springs emanate in 

Florida have experienced 

unprecedented population growth and 

changes in land use over the past 

several decades.99 With these changes in 

population and growth came a transfer 

of nutrients, particularly nitrate, to 

groundwater. Of 125 spring vents 

sampled by the Florida Geological 

Survey in 2001–2002, 42% had nitrate 

concentrations exceeding 0.50 mg/L and 

24% had concentrations greater than 1.0 

mg/L.100 Similarly, a recent evaluation 

of water quality in 13 springs shows that 

mean nitrate-nitrite levels have 

increased from 0.05 mg/L to 0.9 mg/L 

between 1970 and 2002. Overall, data 

suggest that nitrate-nitrite 

concentrations in many spring 

discharges have increased from 10 to 

350 fold over the past 50 years, with the 

level of increase closely correlated with 

anthropogenic activity and land use 

changes within the karst regions of 

Florida where springs predominate. 

As nitrate-nitrite concentrations have 

increased during the past 20 to 50 years, 

many Florida springs have undergone 

adverse environmental and biological 

changes. According to FDEP, there is a 

general consensus in the scientific 

community that nitrate is an important 

factor leading to the observed changes 

in spring ecosystems, and their 

associated biological communities. 

Nitrogen, particularly nitrate-nitrite, 

appears to be the most problematic 

nutrient problem in Florida’s karst 

region.101

Because nitrate-nitrite has been linked 

to many of the observed detrimental 

impacts in spring ecosystems, there is 

an immediate need to reduce nitratenitrite concentrations in spring vents 

and groundwater. A critical step in 

achieving reductions in nitrate-nitrite is 

to develop a numeric nitrate-nitrite 

criterion for spring systems that will be 

protective of these unique and treasured 

resources.102

To protect springs and clear streams 

and to provide assessment levels and 

restoration goals for those that have 

already been impaired by nutrients, EPA 

is proposing numeric nutrient criteria 

for the following parameter for Florida’s 

springs and clear streams (< 40 PCU) 

classified as Class I or III waters under 

Florida law (Rule 62–302.400, F.A.C.): 

Nitrate (NO3 )+Nitrite (NO2 ) shall 

not surpass a concentration of 0.35 mg/L as 

an annual geometric mean more than once in 

a three-year period, nor surpassed as a longterm average of annual geometric mean 

values. 

In addition to the nitrate-nitrite 

criterion, TN and TP criteria developed 

for streams on a watershed basis are also 

applicable to clear streams. See Section 

III.C(1) ‘‘Proposed Numeric Nutrient 

Criteria for the State of Florida’s Rivers 

and Streams’’ for the table of proposed 

TN and TP criteria that would apply to 

clear streams located within specific 

watersheds. 

(2) Methodology for Deriving EPA’s 

Proposed Criteria for Springs and Clear 

Streams 

EPA’s proposed nitrate-nitrite 

criterion for springs and clear streams 

are derived from a combination of FDEP 

laboratory data, field surveys, and 

analyses which include analyses 

conducted to determine the stressor 

response-based thresholds that link 

nitrate-nitrite levels to biological risk in 

springs and clear streams. These data 

document the response of nuisance 

algae, Lyngbya wollei and Vaucheria sp., 

and periphyton to nitrate-nitrite 

concentrations. Please refer to EPA’s 

TSD for Florida’s Inland Waters, 

Chapter 3: Methodology for Deriving 

U.S. EPA’s Proposed Criteria for Springs 

and Clear Streams. 

As described in Section III.C(2), the 

ability to establish protective criteria for 

both causal and response variables 

depends on available data and scientific 

approaches to evaluate these data. EPA 

has not undertaken the development of 

TP criteria for springs because 

phosphorus has historically been 

present in Florida’s springs, given the 

State’s naturally phosphorus-rich 

geology, and the lack of an increasing 

trend of phosphorus concentrations in 

most spring discharges. EPA is not 

proposing chlorophyll a and clarity 

criteria due to the lack of available data 

for these response variables in spring 

systems. Furthermore, scientific 

evidence examining the strong 

relationship between rapid periphyton 

survey data (measurements of the 

thickness of algal biomass attached to 

substrate rather than free-floating) and 

nutrients in clear streams (those with 

color <40 PCU and canopy cover ≤ 40% 

which are comparable to most waters 

found in springs and spring runs) show 

that benthic algal thickness is highly 

dependent on nitrogen parameters (TN 

and total inorganic nitrogen), as 

opposed to phosphorus. In addition, 

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103Stevenson, R.J., A. Pinowska, A. Albertin, and 

J.O. Sickman. 2007. Ecological condition of algae 

and nutrients in Florida springs: The Synthesis 

Report. Prepared for the Florida Department of 

Environmental Protection. Tallahassee, FL. 58 pp. 

Cowell, B.C. and C.J. Dawes. 2004. Growth and 

nitrate-nitrogen uptake by the cyanobacterium 

Lyngbya wollei. J. Aquatic Plant Management 42: 

69–71. 

104 Gao, X. 2008. Nutrient TMDLs for the Wekiva 

River (WBIDs 2956, 2956A, and 2956C) and Rock 

Springs Run (WBID 2967). Florida Department of 

Environmental Protection, Tallahassee, Florida. 

105Mattson, R.A., E.F. Lowe, C.L. Lippincott, D. 

Jian, and L. Battoe. 2006. Wekiva River and Rock 

Springs Run Pollutant Load Reduction Goals. St. 

Johns River Water Management District, Palatka, 

Florida. 

106 Gao, X. 2008. Nutrient TMDLs for the Wekiva 

River (WBIDs 2956, 2956A, 2956C) and Rock 

EPA is proposing to apply the nitratenitrite criteria derived for springs to 

clear streams as a measure to gauge 

anthropogenic contributions to TN. EPA 

is not currently proposing criteria for 

clarity and chlorophyll a for clear 

streams due to the lack of scientific 

evidence supporting the relationship 

between these response variables and 

nutrients. Clear streams show weak 

relationships between nutrients and 

chlorophyll a, as opposed to color 

streams where phytoplankton responses 

occur more readily than periphyton 

growth. Please refer to EPA’s TSD for 

Florida’s Inland Waters, Chapter 3: 

Methodology for Deriving U.S. EPA’s 

Proposed Criteria for Springs and Clear 

Streams. 

(a) Derivation of Proposed NitrateNitrite Criteria 

EPA’s goal in deriving nitrate-nitrite 

criteria for Florida springs and clear 

streams is to ensure that the criteria will 

preserve the ecosystem structure and 

function of Florida’s springs and clear 

streams. EPA reviewed Florida data, 

FDEP’s approach and analyses, and 

FDEP’s proposed nitrate-nitrite criterion 

for springs and clear streams and has 

concluded that the FDEP approach and 

the values FDEP derived represent a 

scientifically sound basis for the 

derivation of these criteria. FDEP 

evaluated results from laboratory scale 

dosing studies, data from in-situ algal 

monitoring, real-world surveys of 

biological communities and nutrient 

levels in Florida springs, and data on 

nitrate-nitrite concentrations found in 

minimally-impacted reference locations. 

FDEP analyzed laboratory data103 that 

evaluated the growth response of 

nuisance algae to nitrate addition. 

FDEP’s analysis showed that Lyngbya 

wollei and Vaucheria sp. reached 90% 

of their maximum growth at 0.230 

mg/L and 0.261 mg/L nitrate-nitrite, 

respectively. FDEP also reviewed longterm field surveys that examined the 

response of nuisance algae, periphyton, 

and eutrophic indicator diatoms to 

nitrate-nitrite concentration.104 The 

results showed a sharp increase in 

abundance and/or biomass of the 

nuisance algae, periphyton, and diatoms 

at 0.44 mg/L nitrate-nitrite. 

FDED also reviewed the field surveys 

used to develop TMDLs for Wekiva 

River and Rock Spring Run to evaluate 

the relationship between the observed 

excessive algal growth and imbalance in 

aquatic flora with measurements of 

nutrients in these particular systems. 

FDEP found that taxa indicative of 

eutrophic conditions increased 

significantly with increasing nitratenitrite concentrations above 

approximately 0.35 mg/L. 

Based on its review of a combination 

of this laboratory and field data, FDEP 

concluded that significant alterations in 

community composition (eutrophic 

indicator diatoms), in combination with 

an increase in periphyton cell density 

and biomass, clearly demonstrate that a 

nitrate-nitrite level in the range between 

0.23 mg/L (the laboratory threshold) and 

0.44 mg/L (the field study derived value 

associated with the upper bound nitratenitrite concentration where substantial 

observed biological changes were 

apparent) is the amount of nitrate-nitrite 

associated with an imbalance of aquatic 

flora in spring systems.105

FDEP conducted further statistical 

analyses of the available data from the 

multiple lines of evidence, applied an 

appropriate safety factor to ensure that 

waters would not reach the nitratenitrite levels associated with 

‘‘substantial observed biological 

changes,’’ and averaged the results to 

arrive at a final protective threshold 

value for nitrate-nitrite in springs and 

clear streams of 0.35 mg/L. Based on the 

discussion above and corresponding 

analysis in the TSD for Florida’s Inland 

Waters, EPA has concluded that this 

value was derived in a scientifically 

sound manner, appropriately 

considering the available data, and 

appropriately interpreting the multiple 

lines of evidence. Accordingly, EPA is 

proposing 0.35 mg/L nitrate-nitrite as a 

protective criterion for aquatic life in 

Florida’s springs and clear streams. 

(b) Proposed Criteria: Duration and 

Frequency 

EPA is proposing a duration and 

frequency expression of an annual 

geometric mean not to be surpassed 

more than once in a three-year period to 

be consistent with the expressions of 

duration and frequency for other water 

body types (e.g., lakes, streams, canals) 

for TN and TP and for the same reasons 

EPA selected a three-year period for 

those waters. Second, EPA proposes that 

the long-term arithmetic average of 

annual geometric means not exceed the 

criterion-magnitude concentration. EPA 

anticipates that Florida will use its 

standard assessment periods as 

specified in Rule 62–303, F.A.C. 

(Impaired Waters Rule) to implement 

this second provision. EPA has 

determined that this frequency of 

excursions should not result in 

unacceptable effects on aquatic life as it 

will allow the springs and clear streams 

aquatic systems enough time to recover 

from an occasionally elevated year of 

nutrient loadings. The Agency requests 

comment on these proposed duration 

and frequency expressions of the 

springs and clear streams numeric 

nutrient criteria. 

EPA also considered as an alternative, 

expressing the criterion as a monthly 

median not to be surpassed more than 

10% of the time. Stated another way, 

the median value over any given 

calendar month shall not be higher than 

the criterion-magnitude value in more 

than one out of every ten months. It is 

appropriate to express a monthly 

criterion as a median because the 

median is less susceptible to outliers 

than the geometric mean. This is 

particularly important when dealing 

with small sample sizes. This 

alternative is consistent with the 

expression that FDEP proposed in July 

2009 for its State rule and the 

expression in the TSD for Florida’s 

Inland Waters that EPA sent out for 

external scientific peer review in July 

2009. The rationale for this alternative 

is that field data indicate that the 

response in springs is correlated to 

monthly exposure at the criterionmagnitude concentration value and a 

10% frequency of excursions is a 

reasonable and fully protective 

allowance given small sample sizes in 

any given month (i.e., the anticipated 

amount of data that will be available for 

assessment purposes in the future). The 

clear streams nitrate-nitrite criterion 

was derived by FDEP based on multiple 

lines of evidence, with the primary lines 

of evidence being mesocosm dosing 

experiments and field studies. These 

two main studies were conducted by 

FDEP over very different time frames. 

One set of mesocosm studies was 

conducted by FDEP for periods just 

under one month (i.e., 21 to 28 days), 

while another, the algal biomass field 

survey, was conducted over an 18-year 

period and was analyzed using four to 

five year averaging periods.106 While lab 

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Springs Run (WBID 2967). Florida Department of 

Environmental Protection, Tallahassee, Florida. 

107Stevenson, R.J., A. Pinowska, A. Albertin, and 

J.O. Sickman. 2007. Ecological condition of algae 

and nutrients in Florida springs: The Synthesis 

Report. Prepared for the Florida Department of 

Environmental Protection. Tallahassee, FL. 58 pp. 

studies indicate that algal communities 

can respond to excess nitrate-nitrite 

over a short period of time, the 

mesocosm and other dosing studies 

indicate that this response occurs on the 

order of a month, which might support 

a monthly expression of the criterion.107

However, there is no evidence to suggest 

that the responses observed within a 

month under controlled lab settings 

equate to impairment of the designated 

use in conditions experienced in State 

waters. Please refer to EPA’s TSD for 

Florida’s Inland Waters, Chapter 3: 

Methodology for Deriving U.S. EPA’s 

Proposed Criteria for Springs and Clear 

Streams. 

The 10% excursion frequency would 

recognize that in most cases the 

monthly ‘‘median’’ would actually be 

based on a single sample, given that 

most springs are only sampled monthly 

at the most. A 10% excursion frequency 

may be considered a reasonable and 

fully protective allowance given small 

sample sizes in any given month, 

essentially requiring that the monthly 

median nitrate-nitrate concentrations 

thought to be fully supportive of 

relevant designated uses be met 90% of 

the time. 

EPA requests comment on these 

proposed criteria duration and 

frequency expressions, and the basis for 

their derivation. EPA notes that some 

scientists and resource managers have 

suggested that nutrient criteria duration 

and frequency expressions should be 

more restrictive to avoid seasonal or 

annual ‘‘spikes’’ from which the aquatic 

system cannot easily recover, whereas 

others have suggested that criteria 

expresssed as simply a long-term 

average of annual geometric means, 

consistent with data used in criteria 

derivation, would still be protective. 

EPA requests comment on alternative 

duration and frequency expressions that 

might be considered protective, 

including (1) a criterion-duration 

expressed as a monthly average or 

geometric mean, (2) a criterionfrequency expressed as meeting 

allowable magnitude and duration every 

year, (3) a criterion-frequency expressed 

as meeting allowable magnitude and 

duration in more than half the years of 

a given assessment period, and (4) a 

criterion-frequency expressed as 

meeting the allowable magnitude and 

duration as a long-term average only. 

EPA further requests comment on 

whether an expression of the criteria in 

terms of an arithmetic average of annual 

geometric mean values based on rolling 

three-year periods of time would also be 

protective of the designated use. 

(3) Request for Comment and Data on 

Proposed Approach 

EPA believes the proposed nutrient 

criterion for springs and clear streams in 

this rule are protective of the designated 

aquatic life use of these waters in 

Florida. EPA is soliciting comment on 

the approach FDEP used and EPA 

adopted to derive nitrate-nitrite 

criterion for springs and clear streams, 

including the data and analyses 

underlying the proposed criterion. EPA 

is seeking additional, readily-available, 

pertinent data and information related 

to nutrient concentrations or nutrient 

responses in springs and clear streams 

in Florida. EPA is also soliciting views 

on other potential, scientifically sound 

approaches to deriving protective 

nitrate-nitrite criterion for springs and 

clear streams in Florida. 

(4) Alternative Approaches: NitrateNitrite Criterion for All Waters as an 

Independent Criterion 

EPA is soliciting comment on the 

environmental benefits associated with 

deriving a nitrate-nitrite criterion for all 

waters covered by this proposal (i.e., all 

streams, lakes, and canals), in addition 

to the other proposed nutrient criteria 

for those water bodies. Adoption of a 

nitrate-nitrite criterion for waters other 

than springs and clear streams could be 

useful from an assessment and 

management perspective. Florida could 

use nitrate-nitrite data to identify 

increasing trends that may indicate the 

need for more specific controls of 

certain nitrogen enrichment sources. In 

cases where waters are impaired for 

either TN, nitrate-nitrite, or both TN and 

nitrate-nitrite, FDEP could use the 

nitrate-nitrite data to potentially target 

discharges of anthropogenic origin given 

their relative source contribution to 

nitrogen enrichment. 

This alternative approach, which 

would involve EPA deriving nitratenitrite criteria for all waters or 

alternatively applying 0.35 mg/L nitratenitrite to all waters, could provide 

additional protection for aquatic life 

designated uses. The alternative 

approach would also eliminate the need 

for FDEP to characterize streams as clear 

or not. Deriving and applying a nitratenitrite criterion to all waters would 

reduce the likelihood of excess loading 

of the specific anthropogenic 

components of TN to colored waters. 

However, these colored streams may be 

less likely to show an observed response 

to nitrate-nitrite due to the presence of 

tannins that block light penetration. 

Thus, the presence of color in streams 

may confound the relationship that 

produced the 0.35 mg/L nitrate-nitrite 

criterion. 

E. Proposed Numeric Nutrient Criteria 

for South Florida Canals 

(1) Proposed Numeric Nutrient Criteria 

for South Florida Canals 

There are thousands of miles of canals 

in Florida, particularly in the 

southeastern part of the State. Canals are 

artificial waterways that are either the 

result of modifications to existing rivers 

or streams, or waters that have been 

created for various purposes, including 

drainage and flood control (stormwater 

management), irrigation, navigation, and 

recreation. These canals also allow for 

the creation of many waterfront home 

sites in Florida. Ecosystems that existed 

in rivers and streams prior to their 

modification into canals are altered. 

These changes can affect fish and 

wildlife and plant growth, as further 

explained in the following paragraphs. 

Newly created canals may have a 

tendency to fill with aquatic plants. 

Canals in south Florida vary greatly in 

size and depth. They can be anywhere 

from a few feet wide and a few feet deep 

to hundreds of feet wide and as deep as 

30–35 feet. 

South Florida canals vary in their 

hydrology and behavior due to their 

size, function, and seasonality. Shallow 

canals with slow water flow have poor 

turnover of water and little flushing. 

Large canals also may have low flow 

and turnover during the dry season. In 

contrast, during the wet season these 

same large canals are flowing systems 

that quickly move large volumes of 

water, as they were designed to 

accomplish. Excess nutrients in canals 

in combination with poor water 

circulation and decreased levels of 

dissolved oxygen, can lead to 

accelerated eutrophication and adverse 

impacts on other forms of aquatic life 

such as fish and other aquatic animals. 

In these canals, the accumulation of 

decaying organic matter on the canal 

bottom can also adversely impact 

healthy aquatic ecosystems. 

South Florida canals are highly 

managed waterways. Some canals are 

prone to an over-abundance of aquatic 

plants. Without regular and frequent 

management, dense vegetation can clog 

the waterways making navigation 

difficult and slowing the movement of 

water through the canal system. This 

can interfere with flood control, boating, 

and fishing. Aquatic plants (like plants 

in the terrestrial environment) respond 

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and grow when fertilized with nutrients 

such as phosphorus and nitrogen, and 

thus nutrient runoff into canals is likely 

a significant contributor to both 

nuisance algal blooms and clogging of 

canal systems by aquatic plants. 

EPA is proposing numeric nutrient 

criteria for the following parameters and 

geographic classifications in south 

Florida, for canals classified as Class III 

waters under Florida law (Rule 62– 

302.400, F.A.C.). The proposed and 

alternative approaches described herein 

would not apply for TP in canals within 

the Everglades Protection Area (EvPA) 

since there is an existing TP criterion of 

0.010 mg/L that currently applies to the 

marshes and adjacent canals within the 

EvPA (Rule 62–302.540, F.A.C.). 

Chlorophyll a 

(μg/L) a

Total phosphorus (TP) 

(mg/L) a b

Total nitrogen 

(TN) 

(mg/L) a

Canals .......................................................................................................................................... 4.0 0.042 1.6 

a Concentration values are based on annual geometric mean not to be surpassed more than once in a three-year period. In addition, the longterm average of annual geometric mean values shall not surpass the listed concentration values. (Duration = annual; Frequency = not to be surpassed more than once in a three-year period or as a long-term average). b Applies to all canals within the Florida Department of Environmental Protection’s South Florida bioregion, with the exception of canals within 

the Everglades Protection Area (EvPA) where the TP criterion of 0.010 mg/L currently applies. 

The following sections detail the 

methodology EPA used to develop the 

proposed numeric nutrient criteria for 

canals in south Florida, and request 

comment on the proposed criteria and 

their derivation. In addition, EPA is 

providing details of two alternative 

options for deriving canal criteria values 

that EPA considered and is soliciting 

comments on these alternatives. 

(2) Methodology for Deriving EPA’s 

Proposed Criteria for South Florida 

Canals 

Based on the available information for 

canals, EPA determined that the most 

scientifically sound way to derive 

protective numeric nutrient criteria for 

south Florida’s canals is to use a similar 

approach to what EPA used to derive 

numeric nutrient criteria for streams. 

That is, EPA chose a nutrient 

concentration distribution-based 

approach using data from only those 

canals that have been determined to 

support the applicable designated use. 

EPA used existing water quality 

assessments and identified canals that 

have been determined to be impaired for 

nutrients. Data for those canals were 

excluded from the larger data set in 

order to create a set of data representing 

canals attaining the designated use of 

aquatic life, according to FDEP’s 

assessment decisions. For further 

information, please refer to EPA’s TSD 

for Florida’s Inland Waters, Chapter 4: 

Methodology for Deriving U.S. EPA’s 

Proposed Criteria for Canals. 

(a) Derivation of Proposed Numeric 

Nutrient Criteria for South Florida 

Canals 

EPA derived numeric nutrient criteria 

for south Florida canals for two causal 

variables, TN and TP, and one response 

variable, chlorophyll a. In contrast to 

EPA’s proposed criteria for Florida’s 

streams, EPA concluded that there was 

a sufficient scientific basis for a 

chlorophyll a criterion for south Florida 

canals. EPA considered chlorophyll a to 

be an appropriate indicator of nutrient 

impairment in canals on the basis of the 

observed seasonal flow regimes, 

particularly during the relatively drier 

winter months when flows are relatively 

lower and canal water residence time is 

relatively higher (as compared to wetter, 

summer months). Furthermore, EPA 

found evidence that canals are 

susceptible to impairment due to 

excessive chlorophyll a based on the 

number of canals on Florida’s CWA 

section 303(d) list with chlorophyll a 

cited as the parameter of concern. EPA 

analyzed the range of chlorophyll a 

concentrations in canals and found that 

12% of chlorophyll a concentration 

observations occurred at 10 μg/L or 

higher and 5% of chlorophyll a 

concentration observations occurred at 

20 μg/L or higher. As a point of 

reference, Florida has chlorophyll a 

thresholds of 20 as the numeric 

interpretations of its narrative nutrient 

criteria for streams and 11 μg/L for 

estuaries/open coastal waters, 

respectively, in its Impaired Waters 

Rule (IWR) (Rules 62–303.351 and 62– 

303.353, F.A.C.). Thus, EPA included 

chlorophyll a as a nutrient criterion to 

protect canal aquatic life designated 

uses from an unacceptable biological 

response to excess nutrients. 

EPA employed a statistical 

distribution approach for deriving 

numeric nutrient criteria for south 

Florida canals. Specifically, EPA 

computed statistical distributions and 

descriptive statistics (e.g., quartiles, 

mean, standard deviation) of TN, TP, 

and chlorophyll a concentrations from 

data derived at canal sites across south 

Florida that are not on the impaired 

waters list for Florida. EPA has 

determined that the criteria derived 

from a distribution of canal data from 

canals with no evidence of nutrient 

impairment are appropriate and 

protective of designated uses. 

As described in detail in Section 

III.C(2)(c), EPA concluded that the 75th 

percentiles of the respective TN, TP, 

and chlorophyll a distributions would 

yield values that would ensure that 

aquatic life designated uses would be 

protected in south Florida canals. A 

reasonable choice is one that lies just 

above the vast majority of the 

population. The 75th percentile 

represents such a point on the 

distribution of TN, TP, and chlorophyll 

a values. 

(b) Other Data and Analyses Conducted 

and Considered by EPA in the 

Derivation of Proposed Numeric 

Nutrient Criteria for South Florida 

Canals 

EPA undertook extensive analyses 

and considered a variety of data and 

methods for deriving numeric nutrient 

criteria for Florida’s canals. Although 

EPA derived the proposed values based 

on the approach outlined in the section 

above, EPA also factored into its 

decision-making process the results of 

these other analyses as additional lines 

of evidence. 

One line of additional evidence is 

based on an evaluation of the stressorresponse relationship between 

chlorophyll a levels in canals and TN 

and TP levels using a variety of 

statistical tools. A second line of 

evidence is based on a consideration of 

the distribution of chlorophyll a 

measurements, TN measurements, and 

TP measurements from all canals, 

impaired and not impaired. Nutrient 

concentrations at the lower end of these 

distributions were compared to the 

concentration that the stressor-response 

analysis determined to be associated 

with canals with no evidence of nutrient 

impairment. The third line of evidence 

is based on a consideration of the 

distribution of chlorophyll a, TN, and 

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TP values from only those canals 

considered to be minimally impacted by 

nutrient-related pollution. EPA 

considered each of these lines of 

evidence in deriving the numeric 

nutrient criteria for canals. 

Because soil or substrate type at the 

bottom of a canal can influence the 

nutrient cycling and relationships 

between the observed biological 

response and the TP and TN levels in 

canals, EPA used data on soil types in 

south Florida along with knowledge of 

the Everglades Agricultural Area (EAA) 

and the Everglades Protection Area 

(EvPA) to subdivide the canal areas for 

criteria derivation. Thus the first step in 

these other analyses was to group canals 

and canal data by soil type. The four 

groupings consist of histosol and entisol 

soils of the EAA; histosol and entisol 

soils of the EvPA; spodosol and alfisol 

soils and areas west of the EvPA and 

EAA (hereafter, West Coast); and 

spodosol, entisol and alfisol soils and 

areas east of the EvPA and EAA 

(hereafter East Coast). 

EPA then sorted canal data (provided 

by FDEP, Miami-Dade County, and the 

South Florida Water Management 

District) into the four canal groupings. 

EPA screened the data to ensure the 

exclusion of the following: (1) Sites 

without relevant data (e.g., nitrogen, 

phosphorus, chlorophyll a), (2) sites 

influenced by marine waters, (3) sites 

within Class IV canals or Lake 

Okeechobee, (4) data not originating 

within a canal, (5) data with 

questionable units, and (6) outlier data. 

Data were organized by canal regions 

and year. Each site occurring near the 

border of a region and/or WBID was 

visually inspected using geographic 

information system (GIS) tools to ensure 

the correct placement of those sites. 

Local experts were also consulted by 

EPA. EPA analyzed the resulting 

regionalized data using statistical 

distribution and regression analyses. 

EPA undertook its additional analyses 

using these canal (and data) groupings. 

EPA’s analysis of the distribution of 

chlorophyll a values in each of the four 

groupings of canals (using data from 

impaired and unimpaired sites) 

indicated that the lower percentile (i.e., 

25th percentile) ranged from 1.9 to 2.2 

μg/L for chlorophyll a in the EvPA, 

West Coast, and East Coast, and was 6.3 

μg/L for the EAA. EPA’s analysis of the 

distribution of TN values in each of the 

four groupings of canals indicated that 

the lower percentile (i.e., 25th 

percentile) ranged from 0.8 to 1.4 mg/L 

for the EvPA, West Coast, and East Coast 

and was 2.1 mg/L for the EAA. EPA’s 

analysis of the distribution of TP values 

in each of the four groupings of canals 

indicated that the lower percentile (i.e., 

25th percentile) ranged from 0.013 to 

0.023 mg/L for the EvPA, West Coast, 

and East Coast and was 0.048 mg/L for 

the EAA canals. 

In an effort to consider chlorophyll a, 

TN, and TP values in canals minimally 

impacted by nutrient pollution, EPA 

identified canal sites surrounded by the 

EvPA in the east and the Big Cypress 

National Preserve in the west and 

considered the distribution of 

chlorophyll a, TN and TP values for 

these sites. Although EPA acknowledges 

that these sites have not been 

thoroughly vetted for biological 

condition, EPA believes that because 

they are remote and surrounded by 

wetlands, that these canal sites 

represent sites with the lowest impact 

from human activities. The upper 

percentile values (i.e., the 75th 

percentile) from the distributions of 

chlorophyll a, TN and TP values for 

these lower impact sites are 3.4 μg/L for 

chlorophyll a, 1.3 mg/L for TN and 

0.018 mg/L for TP. 

When considering the results of these 

additional analyses and comparing 

these results to the outcome of EPA’s 

analysis of TN, TP, and chlorophyll a 

concentrations from data derived at 

canal sites across south Florida that are 

not on the impaired waters list for 

Florida, it is clear that EPA’s proposed 

criteria for canals are similar to those 

derived from alternative approaches and 

therefore, represent a reasonable 

integration of these multiple lines of 

evidence. For further information, 

please refer to EPA’s TSD for Florida’s 

Inland Waters, Chapter 4: Methodology 

for Deriving U.S. EPA’s Proposed 

Criteria for Canals. 

(c) Proposed Criteria: Duration and 

Frequency 

Aquatic life water quality criteria 

contain three components: magnitude, 

duration, and frequency. For the TN and 

TP numeric criteria for canals, the 

derivation of the criterion-magnitude 

values is described above and these 

values are provided in the table in 

Section III.E(1). The criterion-duration 

for this magnitude (or averaging period) 

is specified in footnote a of the canals 

criteria table as an annual geometric 

mean. EPA is proposing two expressions 

of allowable frequency, both of which 

are to be met. First, EPA proposes a nomore-than-one-in-three-years excursion 

frequency for the annual geometric 

mean criteria for canals. Second, EPA 

proposes that the long-term arithmetic 

average of annual geometric means not 

exceed the criterion-magnitude 

concentration. EPA anticipates that 

Florida will use their standard 

assessment periods as specified in Rule 

62–303, F.A.C. (Impaired Waters Rule) 

to implement this second provision. 

These proposed duration and frequency 

components of the criteria are consistent 

with the data set used to derive the 

criteria that contained data from 

multiple years of record, all seasons, 

and a variety of hydrologic conditions. 

EPA has determined that this frequency 

of excursions should not result in 

unacceptable effects on aquatic life as it 

will allow the canal aquatic system 

enough time to recover from an 

occasionally elevated year of nutrient 

loadings. The Agency requests comment 

on these proposed duration and 

frequency expressions of the canal 

numeric nutrient criteria. 

EPA notes that some scientists and 

resource managers have suggested that 

nutrient criteria duration and frequency 

expressions should be more restrictive 

to avoid seasonal or annual ‘‘spikes’’ 

from which the aquatic system cannot 

easily recover, whereas others have 

suggested that criteria expressed as 

simply a long-term average of annual 

geometric means, consistent with data 

used in criteria derivation, would still 

be protective. EPA requests comment on 

alternative duration and frequency 

expressions that might be considered 

protective, including (1) a criterionduration expressed as a monthly average 

or geometric mean, (2) a criterionfrequency expressed as meeting 

allowable magnitude and duration every 

year, (3) a criterion-frequency expressed 

as meeting allowable magnitude and 

duration in more than half of the years 

of a given assessment period, and (4) a 

criterion-frequency expressed as 

meeting the allowable magnitude and 

duration as a long-term average only. 

EPA further requests comment on 

whether an expression of the criteria in 

terms of an arithmetic average of annual 

geometric mean values based on rolling 

three-year periods of time would also be 

protective of the designated use. 

(3) Request for Comment and Data on 

Proposed Approach 

EPA believes the proposed numeric 

nutrient criteria for south Florida canals 

in this rule are protective of the 

designated uses, consistent with CWA 

section 303(c)(2)(A) and 40 CFR 

131.11(a)(1). EPA solicits comment on 

the approaches taken by the Agency in 

this proposal, the data underlying those 

approaches, and the proposed criteria. 

EPA is seeking other pertinent scientific 

data and information that are readily 

available related to nutrient 

concentrations or nutrient responses in 

Class III canals in south Florida. 

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108Proposed Total Maximum Daily Load (TMDL) 

for Dissolved Oxygen and Nutrient in the 

Everglades. Prepared by U.S. EPA Region 4. 

September 2007. 

109State Soil Geographic (STATSGO) database 

provided by the U.S. Department of Agriculture, 

Natural Resources Conservation Service (NRCS). 

110Proposed Total Maximum Daily Load (TMDL) 

for Dissolved Oxygen and Nutrient in the 

Everglades. Prepared by U.S. EPA Region 4. 

September 2007. 

EPA is soliciting comment 

specifically on the selection of criteria 

parameters for TN, TP, and chlorophyll 

a; development of criteria for Class III 

canals across south Florida; and the 

conclusion that the proposed criteria for 

Class III canals are protective of 

designated uses and adequately account 

for the spatial and temporal variability 

of nutrients. 

(4) Alternative Approaches for 

Comment 

EPA is requesting comments and 

views on the advantages and 

disadvantages of alternative approaches 

to deriving protective criteria for south 

Florida canals. These approaches 

include: (1) A stressor-response 

approach (based on data from all canals 

or canals grouped by soil type), and (2) 

methodologies that have been employed 

to develop nutrient targets in an EPAproposed TMDL for dissolved oxygen 

and nutrients.108

As previously described in Section 

III.E(2)(b), EPA considered the 

underlying soil type of south Florida 

canals as a possible basis for geographic 

classification. Analysis of the 

underlying soil types, indicated by 

STATSGO,109 led EPA to identify the 

following four canal regions: Everglades 

Agricultural Area (EAA) comprised of 

histosol and entisol soils, EvPA 

comprised of histosol and entisol soils, 

areas west of the EvPA and EAA, or 

West Coast, comprised of spodosol and 

alfisol soils, and areas east of the EvPA 

and EAA, or East Coast, comprised of 

spodosol, entisol, and alfisol soils. 

Subsequent to classification, the 

proposed statistical distribution-based 

approach or the alternatives to the 

proposed approach described in the 

following sections could be used to 

derive numeric nutrient criteria by canal 

region for any or all of the proposed 

criteria (i.e., TN, TP, and chlorophyll a) 

provided that sufficient data are 

available. 

(a) Stressor-Response Approach 

EPA considered two statistical 

analyses for assessing the stressorresponse relationship between nutrients 

and biological response. In contrast to 

the proposed option, which included 

only data from sites with no evidence of 

nutrient impairment, the stressorresponse analyses included all data 

regardless of whether sites were 

associated with WBIDs that have been 

determined to be impaired. EPA 

conducted linear and quantile 

regression analyses between chlorophyll 

a, TP, and TN on a regional and 

aggregated regional basis. EPA used the 

linear regression model as a statistical 

tool to predict the chlorophyll a 

response based on matched chlorophyll 

a and TN and TP data. Similarly, 

quantile regression was used to analyze 

the matched nutrient and chlorophyll a 

data. In this application, quantile 

regression was used to predict the 90th 

percentile of the distribution of 

chlorophyll a concentration at a given 

concentration of TN or TP. 

To apply either statistical approach 

for developing numeric nutrient criteria 

for TP or TN, EPA would need to 

identify the concentration of 

chlorophyll a that would be protective 

of the designated use for these canal 

systems. One approach would be to use 

EPA’s proposed chlorophyll a criterion 

of 4.0 μg/L for canals to derive the TN 

and TP criteria from stressor-response 

relationships. 

(b) Calculation of TP Criteria for the 

Everglades Agricultural Area (EAA) 

Using a Downstream Protection 

Approach 

EPA considered using the 

methodologies described in the EPAproposed TMDL 110 for dissolved 

oxygen and nutrients to develop 

numeric nutrient criteria, specifically 

TP, for portions of the EAA. These 

methodologies are described in the 

TMDL in Section 4.2.2.1 of the TMDL 

document, ‘‘Approach #1: Estimate STA 

inflow loads resulting in WQS in 

downstream waters’’, and Section 4.2.2.2 

of the TMDL document, ‘‘Approach #2: 

Simple modeling approach.’’ The first 

approach takes into account the 

downstream criterion of the EvPA and 

the performance of the stormwater 

treatment areas (STAs). Based on these 

considerations, inflowing TP 

concentrations within the EAA to the 

STAs were derived to meet the 

downstream EvPA TP criterion of 0.010 

mg/L. The second approach used a 

model that extrapolated natural 

background TP concentrations, based on 

land use changes, for specific WBIDs 

within the EAA. These approaches 

could support the derivation of numeric 

nutrient criteria for TP within the EAA 

region. Approach #1 would result in a 

TP concentration of 0.10 mg/L, while 

Approach #2 would result in a TP 

concentration of 0.087 mg/L. 

(5) Request for Comment and Data on 

Alternative Approaches 

The alternatives for Class III south 

Florida canal criteria in this proposed 

rule represent alternative approaches 

given the availability of data in the State 

of Florida to date and are consistent 

with the requirements of both the CWA 

and EPA’s implementing regulations. 

EPA is soliciting comment on the 

alternative approaches considered by 

the Agency in this proposal, the data 

underlying those approaches, and the 

proposed alternatives themselves, 

including criteria expressed as an upper 

percentile maxima not to be exceeded 

more than 10% of the time in one year, 

similar to those discussed for lakes. For 

further information on the upper 

percentile criteria for canals, refer to 

EPA’s TSD on Florida’s Inland Waters, 

Chapter 4: Methodology for Deriving 

U.S. EPA’s Proposed Criteria for Canals. 

EPA is seeking other pertinent data and 

information related to nutrient 

concentrations or nutrient responses in 

Class III canals in south Florida. 

F. Comparison Between EPA’s and 

Florida DEP’s Proposed Numeric 

Nutrient Criteria for Florida’s Lakes and 

Flowing Waters 

To date, Florida has invested 

significant resources in its statewide 

nutrient criteria effort, and has made 

substantial progress toward developing 

numeric nutrient criteria. For several 

years, FDEP has been actively working 

with EPA on the development of 

numeric nutrient criteria and EPA has 

worked extensively with FDEP on data 

interpretation and technical analyses for 

developing EPA’s recommended 

numeric nutrient criteria proposed in 

this rulemaking. 

On January 14, 2009, EPA formally 

determined that numeric nutrient 

criteria were necessary to protect 

Florida’s lakes and flowing waters and 

should be developed by January 14, 

2010. FDEP, independently from EPA, 

initiated its own State rulemaking 

process to adopt numeric nutrient water 

quality criteria protective of Florida’s 

lakes and flowing waters. According to 

FDEP, the State initiated its rulemaking 

process to facilitate the assessment of 

designated use attainment for Florida’s 

waters and to provide a better means to 

protect its waters from the adverse 

effects of nutrient over-enrichment. 

Florida established a technical advisory 

committee, which met over a number of 

years, to help develop its proposed 

numeric nutrient criteria. The State also 

held several public workshops to solicit 

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comment on the draft WQS. While 

FDEP was progressing with its State 

rulemaking, EPA moved forward to 

develop Federal numeric nutrient 

criteria for Florida’s lakes and flowing 

waters, consistent with EPA’s January 

14, 2009 determination and based on 

the best available science. 

Most recently, in July 2009, FDEP 

solicited public comment on its 

proposed numeric nutrient criteria for 

lakes and flowing waters. In October 

2009, FDEP decided not to bring the 

draft criteria before the Florida 

Environmental Regulation Commission 

(ERC), as had been previously 

scheduled. FDEP did not make any final 

decisions as to whether it might be 

appropriate to ask the ERC to adopt the 

criteria or some portions of the criteria 

at a later date. 

As described in Section III., EPA is 

proposing numeric nutrient criteria for 

the following four water body types: 

Lakes, streams, springs and clear 

streams, and canals in south Florida. 

Given that FDEP has made its proposed 

numeric nutrient criteria available to the 

public via its Web site (http:// 

www.dep.state.fl.us/water/wqssp/ 

nutrients/index.htm), it is worth 

providing a comparative overview 

between the criteria and approaches that 

EPA is proposing in this rulemaking and 

the criteria and approaches FDEP had 

initially proposed. Both EPA and FDEP 

developed numeric criteria recognizing 

the hydrologic and spatial variability of 

nutrients in Florida’s lakes and flowing 

waters. As FDEP indicated on its Web 

site, FDEP’s preferred approach is to 

develop cause and effect relationships 

between nutrients and valued ecological 

attributes, and to establish nutrient 

criteria based on those cause and effect 

relationships that ensure that the 

designated uses of Florida’s waters are 

protected and maintained. As described 

in EPA’s guidance, EPA also 

recommends this approach when 

scientifically defensible data are 

available. Where cause and effect 

relationships could not be 

demonstrated, however, both FDEP and 

EPA relied on a distribution-based 

approach to derive numeric nutrient 

criteria protective of applicable 

designated uses. 

To set numeric nutrient criteria for 

lakes, EPA, like FDEP, is proposing a 

classification scheme using color and 

alkalinity based upon substantial data 

that show that lake color and alkalinity 

play an important role in the degree to 

which TN and TP concentrations result 

in a biological response such as elevated 

chlorophyll a levels. EPA and FDEP 

both found that correlations between 

nutrients and response parameters were 

sufficiently robust to use for criteria 

development in Florida’s lakes. EPA is 

proposing the same chlorophyll a 

criteria for colored lakes and clear 

alkaline lakes as FDEP proposed, 

however, EPA is proposing a lower 

chlorophyll a criterion for clear acidic 

lakes. EPA, like FDEP, is also proposing 

an accompanying supplementary 

analytical approach that Florida can use 

to adjust general TN and TP lake criteria 

within a certain range where sufficient 

data on long-term ambient TN and TP 

levels are available to demonstrate that 

protective chlorophyll a criteria for a 

specific lake will still be maintained 

and attainment of the designated use 

will be assured. 

Lake class 

EPA proposed criteria Florida proposed criteria 

Chl a, μg/L TN, mg/L TP, mg/L Chl a, μg/L TN, mg/L TP, mg/L 

Colored Lakes > 40 PCU ........................ 20 1.23–2.25 0.050–0.157 20 1.23–2.25 0.05–0.157 

Clear Lakes, Alkaline ≤ 40 PCU and > 

50 mg/L CaCO3 .................................... 20 1.00–1.81 0.030–0.087 20 1.00–1.81 0.03–0.087 

Clear Lakes, Acidic ≤ 40 PCU and ≤ 50 

mg/L CaCO3 ......................................... 6 0.500–0.900 0.010–0.030 9 0.85–1.14 0.015–0.043 

To set numeric nutrient criteria for 

streams, FDEP recommended a 

statistical distribution approach based 

on ‘‘benchmark sites’’ identified in five 

nutrient regions (five regions for TP and 

two regions for TN), given that FDEP 

determined cause and effect 

relationships to be insufficiently robust 

for establishing numeric thresholds. 

FDEP relied on the use of a narrative 

criterion to protect downstream waters. 

EPA also concluded that a scientifically 

defensible cause and effect relationship 

could not be demonstrated with the 

available data and that a distributionbased approach was most appropriate. 

However, EPA considered an alternative 

approach that evaluated a combination 

of biological information and data on 

the distribution of nutrients in a 

substantial number of healthy stream 

systems to derive scientifically sound 

TN and TP criteria for streams. 

The respective criteria for instream 

protection of Florida’s streams derived 

using EPA’s recommended approach 

and FDEP’s recommended approach are 

comparable. 

EPA nutrient watershed regions 

EPA proposed 

instream criteria 

Florida nutrient watershed regions 

FL proposed 

instream criteria 

TN 

(mg/L) 

TP 

(mg/L) 

TN 

(mg/L) 

TP 

(mg/L) 

Panhandle ................................................................. 0.824 0.043 Panhandle ................................................................. 0.820 0.069 

Bone Valley ............................................................... 1.798 0.739 Bone Valley .............................................................. 1.730 0.415 

Peninsula .................................................................. 1.205 0.107 Peninsula .................................................................. ............ 0.116 

North Central ............................................................ 1.479 0.359 North Central ............................................................ ............ 0.322 

Northeast .................................................................. ............ 0.101 

In terms of protecting downstream 

waters, EPA used best available science 

and data related to downstream waters 

and found that there are cases where the 

numeric nutrient criteria EPA is 

proposing to protect instream aquatic 

life may not be stringent enough to 

ensure protection of WQS for aquatic 

life in certain downstream lakes and 

estuaries. Accordingly, EPA is 

proposing an equation to be used to 

adjust stream TP criteria to protect 

downstream lakes, and a different 

methodology to adjust TN criteria for 

streams to ensure protection of WQS for 

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downstream estuaries. In cases where a 

stream first flows into a lake and then 

flows out from the lake into another lake 

or estuary, the portion of the stream that 

exits the lakes needs to comply with the 

downstream protection values for 

estuaries, assuming that is the terminal 

reach. 

EPA is proposing the same nitratenitrite causal variable criterion for 

springs and clear streams as proposed 

by FDEP. For canals in south Florida, 

EPA is proposing a statistical 

distribution approach based on sites 

meeting designated uses with respect to 

nutrients (i.e., not identified as impaired 

by FDEP) identified in four canal 

regions. FDEP did not propose numeric 

nutrient criteria for canals in its 

rulemaking. 

Please refer to Section IV. Under What 

Conditions Will Florida Be Removed 

From a Final Rule for information on 

how State-adopted and EPA-approved 

WQS could become effective under the 

CWA 303(c). 

G. Applicability of Criteria When Final 

EPA’s proposed numeric nutrient 

criteria for Florida’s lakes and flowing 

waters will be effective for CWA 

purposes 60 days after publication of 

final criteria and will apply in addition 

to any other existing CWA-effective 

criteria for Class I or Class III waters 

already adopted by the State and 

submitted to EPA (and for those adopted 

after May 30, 2000, approved by EPA). 

EPA requests comment on this proposed 

effective date. FDEP establishes its 

designated uses through a system of 

classes and Florida waters are 

designated into one of several different 

classes. Class III waters provide for 

healthy aquatic life and safe recreational 

use. Class I waters include all the 

protection of designated uses provided 

for Class III waters, and also include 

protection for designated uses related to 

drinking water supply. Class I and III 

waters, together with Class II waters that 

are designated for shellfish propagation 

or harvesting, comprise the set of 

Florida waters that meet the goals 

articulated in section 101(a)(2) of the 

CWA and the waters for which EPA is 

proposing criteria. Pursuant to the 

schedule set out in EPA’s January 2009 

determination, Class II waters will be 

addressed in rulemaking in January 

2011. For water bodies designated as 

Class I and Class III predominately fresh 

waters, any final EPA numeric nutrient 

criteria will be applicable CWA water 

quality criteria for purposes of 

implementing CWA programs including 

permitting under the NPDES program, 

as well as monitoring and assessment 

based on applicable CWA WQS and 

establishment of TMDLs. 

The proposed criteria in this rule, if 

and when finalized, would be subject to 

Florida’s general rules of applicability 

in the same way and to the same extent 

as are other State-adopted and/or 

federally-promulgated criteria for 

Florida waters. See proposed 40 CFR 

131.43(d)(2). For example, Florida 

regulations at Rule 62–4.244, F.A.C. 

authorize mixing zones when deriving 

effluent limitations for discharges of 

pollutants to Florida waters. These 

regulations would apply to permit 

limitations implementing the criteria in 

this rule. This proposal includes some 

additional language on mixing zone 

requirements to help guide Florida in 

developing and applying mixing zone 

policies for nutrient criteria. 

Specifically, EPA provides that the 

criteria apply at the appropriate 

locations within or at the boundary of 

the mixing zones; otherwise the criteria 

apply throughout the water body 

including at the point of discharge into 

the water body. See proposed 40 CFR 

131.43(d)(2)(i). Likewise, EPA includes 

proposed regulatory language specifying 

that Florida use an appropriate design 

flow condition, one that matches the 

proposed criteria duration and 

frequency, for use in deriving permit 

limits and establishing wasteload and 

load allocations for a TMDL. See 

proposed 40 CFR 131.43(d)(2)(ii). 

In addition, EPA recognizes that 

Florida regulations include provisions 

for assessing whether waters should be 

included on the list of impaired waters 

pursuant to section 303(d) of the CWA. 

See Rule 62–303, F.A.C. The Impaired 

Waters Rule, or IWR, sets out a 

methodology to identify waters that do 

not meet the State’s WQS and, therefore, 

are required to be included on CWA 

section 303(d) lists. The current IWR 

does not address how to assess waters 

based on EPA’s proposed numeric 

nutrient criteria. The numeric nutrient 

criteria in any final rule, nevertheless, 

will be applicable WQS that must be 

addressed when the State assesses 

waters pursuant to CWA section 303(d). 

EPA proposes language in this 

rulemaking that acknowledges the IWR 

procedures and their function, 

specifying that those procedures apply 

where they are consistent with the level 

of protection provided by the proposed 

criteria. See proposed 40 CFR 

131.43(d)(2)(iii). Some IWR provisions, 

which describe the sufficiency or 

reliability of information necessary for 

the State to make an attainment 

decision, do not change the level of 

protection afforded Florida waters. 

These are beyond the scope of WQS 

under CWA section 303(c). Other 

provisions of the IWR may provide 

some additional detail relevant to 

assessment, such as the number of years 

worth of data assessed for a particular 

listing cycle submittal, which should be 

consistent with the level of protection 

provided with the proposed criteria. 

Should any IWR provisions apply a 

different level of protection than the 

Federal criteria when making 

attainment decisions based on proposed 

criteria, EPA would expect to take 

appropriate action to ensure that the 

States’ CWA section 303(d) list of 

impaired waters includes all waters not 

attaining the Federal criteria. 

IV. Under What Conditions Will 

Federal Standards Be Either Not 

Finalized or Withdrawn? 

Under the CWA, Congress gave states 

primary responsibility for developing 

and adopting WQS for their navigable 

waters. See CWA section 303(a)–(c). 

Although EPA is proposing numeric 

nutrient criteria for Florida’s lakes and 

flowing waters, Florida continues to 

have the option to adopt and submit to 

EPA numeric nutrient criteria for the 

State’s lakes and flowing waters 

consistent with CWA section 303(c) and 

implementing regulations at 40 CFR part 

131. Consistent with CWA section 

303(c)(4), if Florida adopts and submits 

numeric nutrient criteria and EPA 

approves such criteria as fully satisfying 

the CWA before publication of the final 

rulemaking, EPA will not proceed with 

the final rulemaking for those waters for 

which EPA approves Florida’s criteria. 

Pursuant to 40 CFR 131.21(c), if EPA 

does finalize this proposed rule, the 

EPA promulgated WQS would be 

applicable WQS for purposes of the 

CWA until EPA withdraws the 

federally-promulgated standard. 

Withdrawing the Federal standards for 

the State of Florida would require 

rulemaking by EPA pursuant to the 

requirements of the Administrative 

Procedure Act (5 U.S.C. 551 et seq.). 

EPA would undertake such a 

rulemaking to withdraw the Federal 

criteria only if and when Florida adopts 

and EPA approves numeric nutrient 

criteria that fully meet the requirements 

of section 303(c) of the CWA and EPA’s 

implementing regulations at 40 CFR part 

131. 

If EPA finalizes the proposed 

restoration standard provision 

(discussed in Section VI below), that 

provision would be adopted into 

regulation and would allow Florida to 

establish interim designated uses with 

associated water quality criteria, while 

maintaining the full CWA section 

101(a)(2) aquatic life and/or recreational 

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designated use of the water as the 

ultimate goal. EPA may proceed to 

promulgate numeric nutrient criteria for 

Florida together with or separate from 

EPA’s proposed restoration standards 

provision, depending on the comments 

received on that proposal. 

V. Alternative Regulatory Approaches 

and Implementation Mechanisms 

A. Designating Uses 

Under CWA section 303(c), states 

shall adopt designated uses after taking 

‘‘into consideration the use and value of 

water for public water supplies, 

protection and propagation of fish, 

shellfish, and wildlife, recreation in and 

on the water, agricultural, industrial and 

other purposes including navigation.’’ 

Designated uses ‘‘shall be such as to 

protect the public health or welfare, 

enhance the quality of water and serve 

the purposes of [the CWA].’’ CWA 

section 303(c)(1). EPA’s regulation at 40 

CFR 131.3(f) defines ‘‘designated uses’’ 

as ‘‘those uses specified in water quality 

standards for each water body or 

segment whether or not they are being 

attained.’’ Under 40 CFR 131.10, EPA’s 

regulation addressing ‘‘Designation of 

uses’’, a ‘‘use’’ is a particular function of, 

or activity in, waters of the United 

States that requires a specific level of 

water quality to support it. In other 

words, designated uses are a state’s 

concise statements of its management 

objectives and expectations for each of 

the individual surface waters under its 

jurisdiction. 

In the context of designating uses, 

states often work with stakeholders to 

identify a collective goal for their waters 

that the state intends to strive for as it 

manages water quality. States may 

evaluate the attainability of these goals 

and expectations to ensure they have 

designated appropriate uses (see 40 CFR 

131.10(g)). Consistent with CWA 

sections 101(a)(2) and 303(c)(2)(A), 40 

CFR 131.2 provides that states ‘‘should, 

wherever attainable, provide water 

quality for the protection and 

propagation of fish, shellfish, and 

wildlife and for recreation in and on the 

water.’’ Where states do not designate 

those uses, or remove those uses, they 

must demonstrate that such uses are not 

attainable consistent with 40 CFR 

131.10(g). States may determine, based 

on a UAA, that attaining a designated 

use is not feasible and propose to EPA 

to change the use and/or the associated 

pollutant criteria to something that is 

attainable. This action to change a 

designated use must be completed in 

accordance with EPA regulations (see 40 

CFR 131.10(g) and (h)). 

Within the framework described 

above, states have discretion in 

designating uses. EPA’s proposed 

numeric nutrient criteria for lakes and 

flowing waters would apply to those 

waters designated by FDEP as Class I 

(Potable Water Supplies) or Class III 

(Recreation, Propagation and 

Maintenance of a Healthy, WellBalanced Population of Fish and 

Wildlife). If Florida removes the Class I 

or Class III designated use for any 

particular water body ultimately 

affected by this rule, and EPA finds that 

removal to be consistent with CWA 

section 303(c) and the regulations at 40 

CFR part 131, then the federallypromulgated numeric nutrient criteria 

would not apply to that water body. 

Instead, the nutrient criteria associated 

with the newly designated use would 

apply to that water body. FDEP has 

recently restarted an effort to refine the 

State’s current designated use 

classifications. As this process 

continues, EPA expects that the State 

may find some instances where this 

particular discussion may be relevant 

and useful as the refinement of uses is 

investigated further. 

Where states can identify multiple 

waters with similar characteristics and 

constraints on attainability, EPA 

interprets the Federal WQS regulation to 

allow states to conduct a ‘‘categorical’’ 

use attainability analysis (UAA) under 

40 CFR 131.10(g) for such waters. This 

approach may reduce data collection 

needs, allowing a single analysis to 

represent many sites. To use such an 

approach, however, the State would 

need to have enough information about 

each particular site to reliably place 

each site into a broader category and 

Florida would need to specifically 

identify each site covered by the 

analysis. Florida may wish to consider 

such an approach for certain waters, 

such as a network of canals with similar 

hydrologic and morphological 

characteristics, which can be 

characterized as a group and where the 

necessary level of protection may differ 

substantially from other lakes or flowing 

waters within the State. 

B. Variances 

A variance is a temporary 

modification to the designated use and 

associated water quality criteria that 

would otherwise apply to the receiving 

water. A variance is based on a UAA 

and identifies the highest attainable use 

and associated criteria during the 

variance period. Typically, variances are 

time-limited (e.g., three years), but 

renewable. Modifying the designated 

use for a particular water through a 

variance process allows a state to limit 

the applicability of a specific criterion 

to that water and to identify an 

alternative designated use and 

associated criteria to be met during the 

term of the variance. A variance should 

be used instead of removal of a use 

where the state believes the standard 

can be attained in a short period of time. 

By maintaining the standard rather than 

changing it, the state ensures that 

further progress will be made in 

improving water quality and attaining 

the standard. A variance may be written 

to address a specified geographical 

coverage, a specified pollutant or 

pollutants, and/or a specified pollutant 

source. All other applicable WQS not 

specifically modified by the variance 

would remain applicable (e.g., any other 

criteria adopted to protect the 

designated use). State variance 

procedures, as part of state WQS, must 

be consistent with the substantive 

requirements of 40 CFR part 131. A 

variance allows, among other things, 

NPDES permits to be written such that 

reasonable progress is made toward 

attaining the underlying standards for 

affected waters without violating section 

402(a)(l) of the Act, which requires that 

NPDES permits must meet the 

applicable WQS. See also CWA section 

301(b)(1)(C). 

For purposes of this proposal, EPA is 

proposing criteria that apply to use 

designations that Florida has already 

established. EPA believes that the State 

has sufficient authority to use its 

adopted and EPA-approved variance 

procedures with respect to modification 

of their Class I or Class III uses as it 

pertains to any federally-promulgated 

nutrient criteria. For this reason, EPA is 

not proposing a Federal variance 

procedure. 

C. Site-Specific Criteria 

A site-specific criterion is an 

alternative value to a statewide, or 

otherwise applicable, water quality 

criterion that meets the regulatory test of 

protecting the designated use and 

having a basis in sound science, but is 

tailored to account for site-specific 

conditions. Site-specific alternative 

criteria (SSAC) may be more or less 

stringent than the otherwise applicable 

criteria. In either case, because the 

SSAC must protect the same designated 

use and must be based on sound science 

(i.e., meet the requirement of 40 CFR 

131.11(a)), there is no need to modify 

the designated use or conduct a UAA. 

SSAC may be appropriate when 

additional scientific consideration can 

bring added precision or accuracy to 

express the necessary level or 

concentration of a water quality 

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parameter that is protective of the 

designated use. 

Florida has adopted procedures for 

developing and adopting SSAC in its 

WQS regulations at Florida 

Administrative Code (Rule 62–302.800, 

F.A.C.). Florida’s Type I SSAC 

procedure is intended to address sitespecific situations where a particular 

water body cannot meet the applicable 

water quality criterion because of 

natural conditions. See Rule 62– 

302.800(1). Florida’s Type II SSAC 

procedure is intended to address sitespecific situations other than natural 

conditions where it can be established 

that an alternative criterion from the 

broadly applicable criteria established 

by the State is protective of a water’s 

designated uses. See Rule 62– 

302.800(1), F.A.C. Florida’s Type II 

procedure is primarily intended to 

address toxics but there is no limitation 

in its use for other parameters, except 

for certain parameters identified by 

FDEP, including nutrients. See Rule 62– 

302.800(2). Florida’s regulations 

currently do not allow use of Type II 

procedures for nutrient criteria 

development because the State currently 

does not have broadly applicable 

numeric nutrient criteria for State 

waters. Rather, the current narrative 

criterion for nutrients is implemented 

by translating it into numeric loads or 

concentrations on a case-by-case basis. 

EPA’s proposed rule would not affect 

Florida’s Type I or Type II SSAC 

procedures. 

EPA believes that there would be 

benefit in establishing a specific 

procedure in the Federal rule for EPA 

adoption of SSAC. In this rulemaking, 

EPA is proposing a procedure whereby 

the State could develop a SSAC and 

submit the SSAC to EPA with 

supporting documentation for EPA’s 

consideration. The State SSAC could be 

developed under either the State SSAC 

procedures or EPA technical processes 

as set out more fully below. EPA elected 

to propose this approach because this 

procedure maintains the State in a 

primary decision-making role regarding 

development of SSAC for State waters. 

The procedure that EPA is proposing 

would also allow the State to submit a 

proposed SSAC to EPA without having 

to first go through the State’s 

rulemaking process. 

The proposed procedure would 

provide that EPA could determine that 

the SSAC should apply in lieu of the 

generally applicable criteria 

promulgated pursuant to this rule. The 

proposed procedures provide that EPA 

would solicit public comment on its 

determination. Because EPA’s rule 

would establish this procedure, 

implementation of this procedure would 

not require withdrawal of federallypromulgated criteria for affected water 

bodies in order for the SSAC to be 

effective for purposes of the CWA. EPA 

has promulgated similar procedures for 

EPA granting of variances and SSACs in 

other federally-promulgated WQS. 

EPA also considered technical 

processes necessary to develop 

protective numeric nutrient criteria on a 

site-specific basis. To complete a 

thorough and successful analysis to 

develop numeric nutrient SSAC, EPA 

expects the State to conduct, or direct 

applicants to the State to conduct, a 

variety of supporting analyses. For the 

instream protection value (IPV) for 

streams, this analysis would, for 

example, consist of examining both 

indicators of longer-term response to 

multiple stressors such as benthic 

macroinvertebrate health, as determined 

by Florida’s Stream Condition Index 

(SCI) and indicators of shorter-term 

response specific to nutrients, such as 

periphyton algal thickness or 

chlorophyll a levels. The former 

analysis will help address concerns that 

a potential nutrient effect is masked by 

other stressors (such as turbidity which 

can limit light penetration and primary 

production response to nutrient 

response), whereas the latter analysis 

will help address concerns that a 

potential nutrient effect is lagging in 

time and has not yet manifested itself. 

Indicators of shorter-term response 

generally would not be expected to 

exhibit a lag time. 

It will also be important to examine 

a stream system on a watershed basis to 

ensure that a SSAC established for one 

segment does not result in adverse 

effects in nearby segments. For example, 

a shaded, relatively swift flowing 

segment may open up to a shallow, slow 

moving, open canopy segment that is 

more vulnerable to adverse nutrient 

impacts. Empirical data analysis of 

multiple factors affecting the expression 

of response to nutrients and mechanistic 

models of ecosystem processes can 

assist in this type of analysis. It will also 

be necessary to ensure that a larger load 

allowed from an upstream segment as a 

result of a SSAC does not compromise 

protection on a downstream segment 

that has not been evaluated. 

The intent of this discussion is to 

illustrate a process that is rigorous and 

based on sound scientific rationale, 

without being inappropriately onerous 

to complete. Corollary analyses for a 

lake, spring or clear stream, or canal 

situation would need to be pursued for 

a SSAC on those systems. 

In addition to the procedure that EPA 

is proposing, Florida always has the 

option of submitting State-adopted 

SSAC as new or revised WQS to EPA for 

review and approval under the CWA 

section 303(c). There is no bar to a state 

adopting new or revised WQS for waters 

covered by a federally-promulgated 

WQS. For any State-adopted SSAC that 

EPA approves under section 303(c) of 

the Act, EPA would also have to 

complete federal rulemaking to 

withdraw the Federal WQS for the 

affected water body before the State 

SSAC would be the applicable WQS for 

the affected water body for purposes of 

the Act. As discussed above, Florida 

WQS regulations currently do not 

authorize the State to adopt nutrient 

SSAC except where natural conditions 

are outside the limits of broadly 

applicable criteria established by the 

State (Rule 62–302.800, F.A.C.). 

This proposed SSAC process would 

also not limit EPA’s authority to 

promulgate SSAC in addition to those 

developed by the State under the 

process described in this rule. The 

proposed rule recognizes that EPA 

always has the authority to promulgate 

through rulemaking SSAC for waters 

that are subject to federally-promulgated 

water quality criteria. 

D. Compliance Schedules 

A compliance schedule, or schedule 

of compliance, refers to ‘‘a schedule of 

remedial measures included in a 

‘permit,’ including an enforceable 

sequence of interim requirements * * * 

leading to compliance with the CWA 

and regulations.’’ 40 CFR 122.2. In an 

NPDES permit, WQBELs are effluent 

limits based on applicable WQS for a 

given pollutant in a specific receiving 

water (See NPDES Permit Writers 

Manual, EPA–833–B–96–003, 

December, 1996). In addition, EPA 

regulations provide that schedules of 

compliance are to require compliance 

‘‘as soon as possible.’’ 

Florida has adopted a regulation 

authorizing compliance schedules, and 

that regulation is not affected by this 

proposed rule (Rule 62–620.620(6), 

F.A.C.). The regulation provides, in part, 

for schedules providing for compliance 

‘‘as soon as sound engineering practices 

allow, but not later than any applicable 

statutes or rule deadline.’’ The complete 

text of the Florida rules concerning 

compliance schedules is available at 

https://www.flrules.org/gateway/ 

RuleNo.asp?ID=62-620.620. Florida is, 

therefore, authorized to grant 

compliance schedules under its rule for 

WQBELs based on federallypromulgated criteria. 

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111Clean Water Act section 101(a)(2) states that 

it is a national goal for water quality, wherever 

attainable, to provide for the protection and 

propagation of fish, shellfish, and wildlife and 

provide for recreation in and on the water 

112A variance is a temporary modification to the 

designated use and associated water quality criteria 

that would otherwise apply. It is based on a use 

attainability demonstration and targets achievement 

of the highest attainable use and associated criteria 

during the variance period. 

VI. Proposed Restoration Water Quality 

Standards (WQS) Provision 

As described above, many of Florida’s 

waters do not meet the water quality 

goals established by the State and 

envisioned by the CWA because of 

excess amounts of nutrients. In some 

cases, restoring these waters could take 

many years to achieve, especially where 

there is a large difference between 

current water quality conditions and the 

nutrient criteria levels necessary to 

protect aquatic life. In such cases, 

Florida may conclude that restoration 

programs will not result in waters 

attaining their designated aquatic life 

use (and associated numeric nutrient 

criteria) for a long period of time. 

EPA’s current regulations provide that 

a state may remove a designated use if 

it meets certain requirements outlined at 

40 CFR 131.10. Under this provision, if 

the State demonstrates that a designated 

use is not attainable it may conduct a 

use attainability analysis (UAA) to 

revise the designated use to reflect the 

highest attainable aquatic life use, even 

though that use may not meet the CWA 

section 101(a)(2) goal.111 Another option 

that states use to address situations for 

an individual discharger is a dischargerspecific variance.112 Neither of these 

approaches may be optimal or 

appropriate solutions if a state 

determines that certain waters cannot 

attain aquatic life uses due to excess 

nutrient in the near term. 

Based on numerous workshops, 

meetings, conversations and day-to-day 

interactions with state environmental 

managers, EPA understands that states 

interested in restoring impaired water 

may desire the ability to express, in 

their WQS, successive time periods with 

incrementally more stringent designated 

uses and criteria that ultimately result 

in a designated use and criteria that 

reflect a CWA section 101(a)(2) 

designated use. Such an approach 

would allow the state and stakeholders 

necessary time to take incremental steps 

to achieve interim WQS as they move 

forward to ultimately attain a CWA 

section 101(a)(2) designated use. Some 

states have used variances to provide 

such time in their WQS. However, 

variances are typically time limited 

(e.g., three years) and dischargerspecific and do not address the 

challenges of pursuing reductions from 

a variety of sources across a watershed. 

In addition, Federal regulations are not 

explicit in requiring that states pursue 

feasible (i.e. attainable) progress toward 

achieving the highest attainable use 

when implementing a variance. 

Variances also often lack specific 

milestones and a transparent set of 

expectations for the public, dischargers, 

and stakeholders. 

EPA seeks comment on this approach 

to providing Florida with an explicit 

regulatory mechanism for directing state 

efforts to achieve incremental progress 

in a step-wise fashion, applicable to all 

sources, as a part of its WQS. The 

proposed regulatory mechanism 

described in this section applies only to 

WQS for nutrients in Florida waters 

subject to this proposed rule. 

A ‘‘restoration water quality standard’’ 

under EPA’s proposed rule would be a 

WQS that Florida could adopt for an 

impaired water. Under EPA’s proposal, 

the State would retain the current 

designated use as the ultimate 

designated use (e.g. providing for 

eventual attainment of a full CWA 

section 101(a)(2) designated use and the 

associated criteria). However, under the 

restoration standard approach proposed 

in this rule, the State would also adopt 

interim less stringent designated uses 

and criteria that would be the basis for 

enforceable permit requirements and 

other control strategies during the 

prescribed timeframes. These interim 

uses could be no less stringent than an 

existing use as defined in 40 CFR 131.3, 

and would have to meet the 

requirements of 40 CFR 131.10(h)(2). 

The State would need to demonstrate 

that the interim uses and criteria, as 

well as the timeframe, are based on a 

UAA evaluation of what is attainable 

and by when. These interim designated 

uses and criteria and the applicable 

timeframes would all be incorporated 

into the State WQS on a site-specific 

basis, as would be any other designated 

use change or adoption of site-specific 

criteria. 

For example, a restoration WQS for 

nutrients for an impaired Class I or 

Class III colored lake in Florida may 

take the form of the following for a lake 

whose current condition represents 

severely impaired aquatic life with 

chlorophyll a = 40 mg/L, TN = 2.7 mg/ 

L, and TP = 0.15 mg/L: 

Time Chl a TN TP Designated Use Description 

Year 0–5 .......................................................................... 35 2 .4 0.10 Moderately Impaired Aquatic Life. 

Year 6–10 ........................................................................ 25 1 .45 0.06 Slightly Impaired Aquatic Life. 

Year 11 ............................................................................ 20 1 .2 0.05 Full Aquatic Life Use. 

Including such revised interim 

designated uses and criteria within the 

regulations could support efforts by 

Florida to formally establish enforceable 

long-term plans for different watersheds 

or stream reaches to attain the ultimate 

designated use and the associated 

criteria. At the same time, the State 

would be able to ensure that its WQS 

explicitly reflect the attainable 

designated uses and water quality 

criteria to be met at any given time, 

consistent with the CWA and 

implementing regulations. 

Restoration WQS would provide in 

the Federal regulations the framework 

for authorizing the State of Florida to 

adopt restoration WQS for nutrients, 

along with maintaining the availability 

of other tools (e.g., variances and 

compliance schedule provisions), which 

provide flexibility regarding permitting 

individual dischargers. Restoration 

WQS would require a full public 

participation process to assure 

transparency as well as the opportunity 

for different parties to work together, 

exchange information and determine 

what is actually attainable within a 

particular time frame. Going through 

this process would provide Florida with 

a transparent set of expectations to push 

its waters towards restoration in a 

realistic yet verifiable manner. 

In this notice, EPA proposes 

restoration WQS as a clear regulatory 

pathway for the State of Florida to 

adjust the Class I and Class III 

designated uses (and associated nutrient 

criteria) of waters impaired by nutrients 

that is intended to promote active 

restoration, maintain progressive 

improvement, and ensure 

accountability. This approach would 

provide the State of Florida with the 

flexibility to adopt revised designated 

uses and criteria under a set of specific 

regulatory requirements. 

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4220 Federal Register / Vol. 75, No. 16 / Tuesday, January 26, 2010 / Proposed Rules 

Under this proposal, the interim 

designated uses and criteria would be 

the basis for NPDES permits during the 

applicable period reflecting the fact that 

the restoration WQS introduces the 

critical element of time as part of the 

complete WQS. This is intended to 

allow imposition of the maximum 

feasible point source controls and 

nonpoint source nutrient reduction 

strategies to be phased in within the 

overall context of restoration activities 

within the watershed. By reflecting how 

it expects the existing poor quality of its 

waters to incrementally improve to 

achieve longer-term WQS goals, Florida 

could create the flexibility to explore 

more innovative ways to reach the 

requirements of the next phase, thus 

possibly reducing costs or allowing new 

approaches to resolve complex 

technological issues, and maximizing 

transparency with the public during 

each phase. These waters, however, 

would still be considered impaired for 

CWA assessment and listing purposes 

because the ultimate designated use and 

criteria would be part of the restoration 

WQS and would not yet be met. 

The restoration standards would be 

Florida WQS revisions that would go 

through the process of first being 

adopted under State law and then 

approved by EPA. This proposal would 

include eight requirements for the 

development of a restoration WQS for 

nutrients: 

1. It must be demonstrated that it is 

infeasible to attain the full CWA section 

101(a)(2) aquatic life designated use 

during the time periods established for 

the restoration phases with a UAA 

based on one of the factors at 40 CFR 

131.10(g). 

2. The highest attainable designated 

use and numeric criteria that apply at 

the termination of the restoration WQS 

(i.e., the ultimate long-term designated 

use and numeric criteria to be achieved) 

must be specified and this use is to 

include, at a minimum, uses that are 

consistent with the CWA section 

101(a)(2) uses. 

3. Interim restoration designated uses 

and numeric water quality criteria, with 

each based on achieving the maximum 

feasible progress during the applicable 

phase as determined in the UAA, must 

be established. 

4. Specific time periods for each 

restoration phase must be established. 

The length of each phase must be based 

on the UAA demonstration of when 

interim uses can be attained on a casespecific basis. Interim restoration 

designated uses and numeric water 

quality criteria must reflect the highest 

attainable use during the time period of 

the restoration phase. The sum of these 

times periods may not exceed twenty 

years. 

5. The spatial extent to which the 

restoration WQS will apply (e.g., how 

far downstream the restoration WQS 

would apply) must be specified. EPA 

notes the importance of continuing to 

meet the requirements for protection of 

downstream WQS as expressed in 

section 40 CFR 131.10(b). Adopting 

restoration WQS upstream of another 

impaired water may mean the State 

should also consider restoration WQS 

for the downstream water. 

6. The regulatory requirements for 

public participation and EPA review 

and approval whenever revising its 

WQS must continue to be met. 

Specifically, a restoration WQS may not 

include interim uses less stringent than 

a use that is an ‘‘existing use’’ as defined 

in 40 CFR 131.3 or that do not meet the 

requirements of 40 CFR 131.10(h)(2). 

7. The State must include in its 

restoration WQS that if the water body 

does not attain the interim designated 

use and numeric water quality criteria at 

the end of any phase, the restoration 

WQS will no longer be in effect and the 

designated use and criteria that was to 

become effective at the end of the final 

restoration phase will become 

immediately effective unless Florida 

adopts and EPA approves a different 

revised designated use and criteria. 

8. The State must provide that waters 

for which a restoration WQS is adopted 

will be recognized as impaired for the 

purposes of listing impaired waters 

under section 303(d) of the CWA until 

the final use is attained. 

Under this proposal, EPA would 

require Florida to adopt the ultimate 

highest attainable designated use and 

criteria along with multiple phases 

reflecting the stepwise improvements in 

water quality between the initial 

effective date and when they expect to 

meet the ultimate highest attainable use 

as a single restoration WQS package. As 

with any revision to an aquatic life use, 

Florida would be required to 

demonstrate that the ultimate highest 

attainable designated use cannot be 

attained during the restoration period, 

based on one of the factors at 40 CFR 

131.10(g)(1)–(6) (i.e., through a UAA). 

EPA would review the WQS and all 

supporting documents before approving 

the restoration WQS. 

At the beginning of the first 

restoration phase, the State would 

identify current conditions and 

establish the principle that there can be 

no further degradation. WQS for the first 

restoration phase should reflect the 

outcomes of all controls that can be 

implemented within the first restoration 

phase. Additionally, EPA expects that 

the interim restoration designated use 

and numeric criteria that are attainable 

at the end of the restoration phase apply 

at the beginning of each phase as well 

as throughout the phase. For each 

phase, the State would adopt interim 

designated uses and numeric water 

quality criteria that reflect achieving the 

maximum feasible progress. At the end 

of the first phase, EPA would expect the 

water body to be meeting the first 

interim designated use and water 

quality criteria. 

At the beginning of the second phase, 

the next (more stringent) interim 

designated use and water quality criteria 

would go into effect as the applicable 

WQS that the State would use to direct 

the next set of control actions. At the 

conclusion of the second phase, the next 

(more stringent) interim designated use 

and water quality criteria would become 

the applicable WQS. This process 

would repeat with each subsequent 

phase. Permit limits written during the 

restoration phases would include 

effluent limits as stringent as necessary 

to meet the applicable interim 

designated uses and numeric water 

quality criteria. In constructing each 

restoration phase (i.e. duration and 

interim designated use and numeric 

water quality criteria), EPA will require 

the maximum feasible progress. This 

means that necessary control actions 

that would improve water quality and 

can be implemented within the first 

phase must be reflected in the interim 

targets for the first restoration phase. 

This would include all technologybased requirements for point sources, 

and cost-effective and reasonable BMPs 

for nonpoint sources. For treatment 

upgrades to point sources, EPA expects 

careful scrutiny of technology that has 

been successfully implemented in 

comparable situations and presumes 

that this is feasible. EPA further expects 

careful scrutiny of all existing and new 

technology that will help achieve the 

ultimate highest attainable use. 

EPA recognizes that circumstances 

may change as controls are 

implemented and that new information 

may indicate that the timeframes 

established in the restoration WQS are 

too lengthy or possibly unrealistically 

short. If this is the case, the state has the 

discretion under 40 CFR 131.10 to 

conduct a new UAA and revise the 

interim targets in its restoration WQS 

after a full public process and EPA 

approval. However, there is a significant 

burden on the state to demonstrate what 

changed to alter the initial analysis and 

associated expectations for what was 

attainable for that phase. EPA would 

expect such a revision only if there was 

significant new information that 

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demonstrated that a different schedule 

and/or set of interim standards 

represents the maximum feasible 

progress towards the final designated 

use and criteria. 

If at the end of a phase, the water 

body is not meeting interim targets, then 

the restoration WQS would no longer be 

applicable. In such a case, the 

applicable WQS would be the ultimate 

highest attainable use and associated 

criteria unless the state adopted and 

submitted for EPA approval a revised 

WQS. This would help ensure that there 

would be no delay in implementing 

control measures. Alternatively, EPA 

considered an option of allowing the 

subsequent restoration phases to 

become applicable on the schedule 

adopted in the restoration WQS and as 

supported by the original UAA 

demonstration, even if the interim use 

and criteria are not fully achieved on 

schedule. This might have the 

advantage of encouraging the adoption 

of ambitious interim goals in the initial 

restoration standards, and would allow 

continued orderly progress towards 

achievement of the final use and 

criterion even where an interim step 

was not fully attained. EPA solicits 

comment on this alternative approach. 

To develop restoration WQS for 

numeric nutrient criteria, EPA would 

expect that the state identify waters in 

need of restoration, produce an 

inventory of point and nonpoint sources 

within the watershed, and evaluate 

current ambient conditions and the 

necessary reductions to achieve the 

numeric criteria. The next part of the 

process would involve determining the 

combinations of control strategies and 

management practices available, how 

likely they are to produce results, and 

the resources needed to implement 

them. At this point, the State would be 

in a good position to determine how 

much pollution reduction is likely to be 

attainable under what timeframes. The 

State could use this information to 

establish the time periods for each 

restoration phase consistent with the 

maximum feasible and attainable 

progress toward meeting the numeric 

criteria, establish interim restoration 

designated uses and water quality 

criteria, and make the necessary 

demonstration that it is infeasible to 

attain the long-term designated use 

during the time periods established and 

that the interim phases reflect the 

highest attainable uses and associated 

criteria. 

For excess nutrient pollution, the 

contributors to nutrient pollution could 

include publicly-owned treatment 

works (POTWs), industrial dischargers, 

urban and agricultural runoff, 

atmospheric deposition, and septic 

systems. Restoration WQS might reflect 

in an early phase, for example, all 

feasible short-term POTW treatment 

upgrades and a schedule to select, fund, 

and implement longer term nutrient 

reduction technologies, while 

aggressively pursuing reductions in 

nonpoint source runoff. This might 

include specific plans and a schedule to 

develop and implement innovative 

alternative approaches, such as trading 

programs, where appropriate. 

In Florida, many of the steps 

described above occur in the context of 

Basin Management Action Plans 

(BMAPs). FDEP describes BMAPs as: 

* * *the ‘‘blueprint’’ for restoring impaired 

waters by reducing pollutant loadings to 

meet the allowable loadings established in a 

Total Maximum Daily Load (TMDL). It 

represents a comprehensive set of 

strategies—permit limits on wastewater 

facilities, urban and agricultural best 

management practices, conservation 

programs, financial assistance and revenue 

generating activities, etc.—designed to 

implement the pollutant reductions 

established by the TMDL. These broad-based 

plans are developed with local 

stakeholders—they rely on local input and 

local commitment—and they are adopted by 

Secretarial Order to be enforceable. 

(http://www.dep.state.fl.us/Water/ 

watersheds/bmap.htm) Florida has 

adopted BMAPs for the Hillsborough 

River Basin, Lower St. John’s River, Log 

Branch, Orange Creek, and Upper 

Ocklawaha, and has plans for others to 

follow. To the extent necessary, FDEP 

could potentially use aspects of the 

BMAP process and plans such as these 

to help form the basis for restoration 

WQS. 

In summary, the WQS program is 

intended to protect and improve water 

quality and WQS are meant to guide 

actions to address the effects of 

pollution on the Nation’s waters. The 

reality is that as more assessments are 

being done and TMDLs are being 

contemplated, and as new criteria are 

developed and considered, EPA and 

states face questions about what 

pollution control measures will meet 

the WQS, how long it might take, and 

whether it is feasible to attain the WQS 

established to meet the goals of the Act. 

These questions are often difficult to 

answer because of lack of data, lack of 

knowledge, and lack of experience in 

attempting restoration of waters. 

Stakeholders and co-regulators alike 

have expressed a desire for ways to 

pursue progressive water quality 

improvement and evaluate those 

improvements to gain the data, 

knowledge, and experience necessary to 

ultimately determine the highest 

attainable use. In response, EPA has 

been investigating the best ways to use 

UAAs and related tools to make 

progress in identifying and achieving 

the most appropriate designated use. 

EPA requests comments on the 

usefulness of the ‘‘restoration WQS’’ 

proposal for Florida. EPA requests 

comment on how restoration WQS will 

operate in conjunction with listing 

impaired waters, and establishing 

NPDES permit limitations, and 

nonpoint source control strategies, as 

well as how these requirements should 

be reflected in regulatory language. EPA 

also requests comment on the proposed 

20-year limit on the schedule to attain 

the final use and criteria. EPA also 

requests comments on how a restoration 

WQS process would be coordinated 

with the TMDL program and whether 

the transparency and review procedures 

for the two approaches, including the 

conditions under which a State or EPA 

would be required to develop a TMDL, 

are comparable. EPA also requests 

comment on any unintended adverse 

consequences of this approach for any 

of its water quality programs. Finally, 

EPA requests comment on potential 

definitions of ‘‘maximum feasible 

progress.’’ 

VII. Statutory and Executive Order 

Reviews 

A. Executive Order 12866: Regulatory 

Planning and Review 

Under Executive Order (EO) 12866 

(58 FR 51735, October 4, 1993), this 

action is a ‘‘significant regulatory 

action.’’ Accordingly, EPA submitted 

this action to the Office of Management 

and Budget (OMB) for review under EO 

12866 and any changes made in 

response to OMB recommendations 

have been documented in the docket for 

this action. 

This proposed rule does not establish 

any requirements directly applicable to 

regulated entities or other sources of 

nutrient pollution. Moreover, existing 

narrative water quality criteria in State 

law already require that nutrients not be 

present in waters in concentrations that 

cause an imbalance in natural 

populations of flora and fauna in lakes 

and flowing waters in Florida. 

B. Paperwork Reduction Act 

This action does not impose an 

information collection burden under the 

provisions of the Paperwork Reduction 

Act, 44 U.S.C. 3501 et seq. Burden is 

defined at 5 CFR 1320.3(b). It does not 

include any information collection, 

reporting, or record-keeping 

requirements. 

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4222 Federal Register / Vol. 75, No. 16 / Tuesday, January 26, 2010 / Proposed Rules 

113Refer to Docket ID EPA–HQ–OW–2009–0596. 

114EPA was not able to estimate costs for 

municipal stormwater systems because the need for 

incremental controls is uncertain. 

C. Regulatory Flexibility Act 

The Regulatory Flexibility Act (RFA) 

generally requires an agency to prepare 

a regulatory flexibility analysis of any 

rule subject to notice and comment 

rulemaking requirements under the 

Administrative Procedure Act or any 

other statute unless the agency certifies 

that the rule will not have significant 

economic impact on a substantial 

number of small entities. Small entities 

include small businesses, small 

organizations, and small governmental 

jurisdictions. 

For purposes of assessing the impacts 

of this action on small entities, small 

entity is defined as: (1) A small business 

as defined by the Small Business 

Administration’s (SBA) regulations at 13 

CFR 121.201; (2) a small governmental 

jurisdiction that is a government of a 

city, county, town, school district or 

special district with a population of less 

than 50,000; and (3) a small 

organization that is any not-for-profit 

enterprise that is independently owned 

and operated and is not dominant in its 

field. 

Under the CWA WQS program, states 

must adopt WQS for their waters and 

must submit those WQS to EPA for 

approval; if the Agency disapproves a 

state standard and the state does not 

adopt appropriate revisions to address 

EPA’s disapproval, EPA must 

promulgate standards consistent with 

the statutory requirements. EPA also has 

the authority to promulgate WQS in any 

case where the Administrator 

determines that a new or revised 

standard is necessary to meet the 

requirements of the Act. These state 

standards (or EPA-promulgated 

standards) are implemented through 

various water quality control programs 

including the NPDES program, which 

limits discharges to navigable waters 

except in compliance with an NPDES 

permit. The CWA requires that all 

NPDES permits include any limits on 

discharges that are necessary to meet 

applicable WQS. 

Thus, under the CWA, EPA’s 

promulgation of WQS establishes 

standards that the State implements 

through the NPDES permit process. The 

State has discretion in developing 

discharge limits, as needed to meet the 

standards. This proposed rule, as 

explained earlier, does not itself 

establish any requirements that are 

applicable to small entities. As a result 

of this action, the State of Florida will 

need to ensure that permits it issues 

include any limitations on discharges 

necessary to comply with the standards 

established in the final rule. In doing so, 

the State will have a number of choices 

associated with permit writing. While 

Florida’s implementation of the rule 

may ultimately result in new or revised 

permit conditions for some dischargers, 

including small entities, EPA’s action, 

by itself, does not impose any of these 

requirements on small entities; that is, 

these requirements are not selfimplementing. Thus, I certify that this 

rule will not have a significant 

economic impact on a substantial 

number of small entities. 

EPA has prepared an analysis of 

potential costs associated with meeting 

these standards.113 EPA’s analysis uses 

the criteria proposed by FDEP in July 

2009 as a baseline against which to 

estimate the incremental costs of 

meeting the standards in this proposal. 

The baseline costs of meeting Florida’s 

proposed standards are estimated to be 

$102 to $130 million per year. The 

incremental costs, over and above these 

baseline costs, of meeting the standards 

in this NPRM are estimated to be $4.7 

to $10.1 million per year. This analysis 

assumes that most of these costs would 

fall on non-point sources and the 

categories of point sources that would 

be primarily affected are municipal 

wastewater treatment plants and 

industrial and general dischargers.114

EPA estimates the incremental costs for 

these two categories of dischargers, 

including small entities, at about $1 

million per year. 

D. Unfunded Mandates Reform Act 

Title II of the Unfunded Mandates 

Reform Act of 1995 (UMRA), Public 

Law 104–4, establishes requirements for 

Federal agencies to assess the effects of 

their regulatory actions on state, local, 

and tribal governments and the private 

sector. Under section 202 of the UMRA, 

EPA generally must prepare a written 

statement, including a cost-benefit 

analysis, for proposed and final rules 

with ‘‘Federal mandates’’ that may result 

in expenditures to state, local, and tribal 

governments, in the aggregate, or to the 

private sector, of $100 million or more 

in any one year. Before promulgating an 

EPA rule for which a written statement 

is needed, section 205 of the UMRA 

generally requires EPA to identify and 

consider a reasonable number of 

regulatory alternatives and adopt the 

least costly, most cost-effective or least 

burdensome alternative that achieves 

the objectives of the rule. The 

provisions of section 205 do not apply 

when they are inconsistent with 

applicable law. Moreover, section 205 

allows EPA to adopt an alternative other 

than the least costly, most cost-effective 

or least burdensome alternative if the 

Administrator publishes with the final 

rule an explanation of why that 

alternative was not adopted. Before EPA 

establishes any regulatory requirements 

that may significantly or uniquely affect 

small governments, including tribal 

governments, it must have developed 

under section 203 of the UMRA a small 

government agency plan. The plan must 

provide for notifying potentially 

affected small governments, enabling 

officials of affected small governments 

to have meaningful and timely input in 

the development of EPA regulatory 

proposals with significant Federal 

intergovernmental mandates, and 

informing, educating, and advising 

small governments on compliance with 

the regulatory requirements. 

This proposed rule contains no 

Federal mandates (under the regulatory 

provisions of Title II of the UMRA) for 

state, local, or tribal governments or the 

private sector. The State may use these 

resulting water quality criteria in 

implementing its water quality control 

programs. This proposed rule does not 

regulate or affect any entity and, 

therefore, is not subject to the 

requirements of sections 202 and 205 of 

UMRA. 

EPA determined that this proposed 

rule contains no regulatory 

requirements that might significantly or 

uniquely affect small governments. 

Moreover, WQS, including those 

proposed here, apply broadly to 

dischargers and are not uniquely 

applicable to small governments. Thus, 

this proposed rule is not subject to the 

requirements of section 203 of UMRA. 

E. Executive Order 13132 (Federalism) 

This action does not have federalism 

implications. It will not have substantial 

direct effects on the states, on the 

relationship between the national 

government and the states, or on the 

distribution of power and 

responsibilities among the various 

levels of government, as specified in 

Executive Order 13132. EPA’s authority 

and responsibility to promulgate 

Federal WQS when state standards do 

not meet the requirements of the CWA 

is well established and has been used on 

various occasions in the past. The 

proposed rule would not substantially 

affect the relationship between EPA and 

the states and territories, or the 

distribution of power or responsibilities 

between EPA and the various levels of 

government. The proposed rule would 

not alter Florida’s considerable 

discretion in implementing these WQS. 

Further, this proposed rule would not 

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preclude Florida from adopting WQS 

that meet the requirements of the CWA, 

either before or after promulgation of 

the final rule, thus eliminating the need 

for Federal standards. Thus, Executive 

Order 13132 does not apply to this 

proposed rule. 

Although section 6 of Executive Order 

13132 does not apply to this action, EPA 

had extensive communication with the 

State of Florida to discuss EPA’s 

concerns with the State’s nutrient water 

quality criteria and the Federal 

rulemaking process. In the spirit of 

Executive Order 13132, and consistent 

with EPA policy to promote 

communications between EPA and state 

and local governments, EPA specifically 

solicits comment on this proposed rule 

from State and local officials. 

F. Executive Order 13175 (Consultation 

and Coordination With Indian Tribal 

Governments) 

Subject to the Executive Order 13175 

(65 FR 67249, November 9, 2000) EPA 

may not issue a regulation that has tribal 

implications, that imposes substantial 

direct compliance costs, and that is not 

required by statute, unless the Federal 

government provides the funds 

necessary to pay the direct compliance 

costs incurred by tribal governments, or 

EPA consults with tribal officials early 

in the process of developing the 

proposed regulation and develops a 

tribal summary impact statement. EPA 

has concluded that this action may have 

tribal implications. However, the rule 

will neither impose substantial direct 

compliance costs on tribal governments, 

nor preempt Tribal law. 

In the State of Florida, there are two 

Indian tribes, the Seminole Tribe of 

Florida and the Miccosukee Tribe of 

Indians of Florida, with lakes and 

flowing waters. Both tribes have been 

approved for treatment in the same 

manner as a state (TAS) status for CWA 

sections 303 and 401 and have 

federally-approved WQS in their 

respective jurisdictions. These tribes are 

not subject to this proposed rule. 

However, this rule may impact the 

tribes because the numeric nutrient 

criteria for Florida will apply to waters 

adjacent to the tribal waters. 

EPA has contacted the tribes to inform 

them of the potential future impact this 

proposal could have on tribal waters. A 

meeting with tribal officials has been 

requested to discuss the draft proposed 

rule and potential impacts on the tribes. 

EPA specifically solicits additional 

comment on this proposed rule from 

tribal officials. 

G. Executive Order 13045 (Protection of 

Children From Environmental Health 

and Safety Risks) 

This action is not subject to EO 13045 

(62 FR 19885, April 23, 1997) because 

it is not economically significant as 

defined in EO 12866, and because the 

Agency does not believe the 

environmental health or safety risks 

addressed by this action present a 

disproportionate risk to children. 

H. Executive Order 13211 (Actions That 

Significantly Affect Energy Supply, 

Distribution, or Use) 

This rule is not a ‘‘significant energy 

action’’ as defined in Executive Order 

13211, ‘‘Actions Concerning Regulations 

That Significantly Affect Energy Supply, 

Distribution, or Use’’ (66 FR 28355 (May 

22, 2001)), because it is not likely to 

have a significant adverse effect on the 

supply, distribution, or use of energy. 

I. National Technology Transfer 

Advancement Act of 1995 

Section 12(d) of the National 

Technology Transfer and Advancement 

Act of 1995 (‘‘NTTAA’’), Public Law 

104–113, section 12(d) (15 U.S.C. 272 

note) directs EPA to use voluntary 

consensus standards in its regulatory 

activities unless to do so would be 

inconsistent with applicable law or 

otherwise impractical. Voluntary 

consensus standards are technical 

standards (e.g., materials specifications, 

test methods, sampling procedures, and 

business practices) that are developed or 

adopted by voluntary consensus 

standards bodies. The NTTAA directs 

EPA to provide Congress, through OMB, 

explanations when the Agency decides 

not to use available and applicable 

voluntary consensus standards. 

This proposed rulemaking does not 

involve technical standards. Therefore, 

EPA is not considering the use of any 

voluntary consensus standards. 

J. Executive Order 12898 (Federal 

Actions To Address Environmental 

Justice in Minority Populations and 

Low-Income Populations) 

Executive Order (EO) 12898 (59 FR 

7629 (Feb. 16, 1994)) establishes Federal 

executive policy on environmental 

justice. Its main provision directs 

Federal agencies, to the greatest extent 

practicable and permitted by law, to 

make environmental justice part of their 

mission by identifying and addressing, 

as appropriate, disproportionately high 

and adverse human health or 

environmental effects of their programs, 

policies, and activities on minority 

populations and low-income 

populations in the United States. 

EPA has determined that this 

proposed rule does not have 

disproportionately high and adverse 

human health or environmental effects 

on minority or low-income populations 

because it would afford a greater level 

of protection to both human health and 

the environment if these numeric 

nutrient criteria are promulgated for 

Class I and Class III waters in the State 

of Florida. 

List of Subjects in 40 CFR Part 131 

Environmental protection, water 

quality standards, nutrients, Florida. 

Dated: January 14, 2010. 

Lisa P. Jackson, 

Administrator. 

For the reasons set out in the 

preamble, EPA proposes to amend 40 

CFR part 131 as follows: 

PART 131—WATER QUALITY 

STANDARDS 

1. The authority citation for part 131 

continues to read as follows: 

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

Subpart D—[Amended] 

2. Section 131.43 is added as follows: 

§ 131.43 Florida. 

(a) Scope. This section promulgates 

numeric nutrient criteria for lakes, 

streams, springs, canals, estuaries, and 

coastal waters in the State of Florida. 

This section also contains provisions for 

site-specific criteria. 

(b) Definitions— 

(1) Canal means a trench, the bottom 

of which is normally covered by water 

with the upper edges of its two sides 

normally above water, excluding all 

secondary and tertiary canals, classified 

as Class IV waters, wholly within 

Florida’s agricultural areas. 

(2) Clear stream means a free-flowing 

water whose color is less than 40 

platinum cobalt units (PCU). 

(3) Lake means a freshwater water 

body that is not a stream or other 

watercourse with some open contiguous 

water free from emergent vegetation. 

(4) Lakes and flowing waters means 

inland surface waters that have been 

classified as Class I (Potable Water 

Supplies) or Class III (Recreation, 

Propagation and Maintenance of a 

Healthy, Well-Balanced Population of 

Fish and Wildlife) water bodies 

pursuant to Rule 62–302.400, F.A.C., 

excluding wetlands, and are 

predominantly fresh waters. 

(5) Nutrient watershed region means 

an area of the State, corresponding to 

coastal/estuarine drainage basin and 

differing geographical conditions 

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affecting nutrient levels, as delineated 

in the Technical Support Document for 

EPA’s Proposed Rule for Numeric 

Nutrient Criteria for Florida’s Inland 

Surface Fresh Waters. 

(6) Predominantly fresh waters means 

surface waters in which the chloride 

concentration at the surface is less than 

1,500 milligrams per liter. 

(7) Spring means the point where 

underground water emerges onto the 

Earth’s surface, including its spring run. 

(8) Spring run means a free-flowing 

water that originates from a spring or 

spring group whose primary (>50%) 

source of water is from a spring or 

spring group. 

(9) State shall mean the State of 

Florida, whose transactions with the 

U.S. EPA in matters related to this 

regulation are administered by the 

Secretary, or officials delegated such 

responsibility, of the Florida 

Department of Environmental Protection 

(FDEP), or successor agencies. 

(10) Stream means a free-flowing, 

predominantly fresh surface water in a 

defined channel, and includes rivers, 

creeks, branches, canals (outside south 

Florida), freshwater sloughs, and other 

similar water bodies. 

(11) Surface water means water upon 

the surface of the earth, whether 

contained in bounds created naturally 

or artificially or diffused. Water from 

natural springs shall be classified as 

surface water when it exits from the 

spring onto the Earth’s surface. 

(c) Criteria for Florida waters— 

(1) Criteria for lakes. The applicable 

criterion for chlorophyll a, total 

nitrogen (TN), and total phosphorus 

(TP) for lakes within each respective 

lake class is shown on the following 

table: 

Long-term average lake color and alkalinity Chlorophyll a f

(μg/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

A B C D E F 

Colored Lakes > 40 PCU .................................................... 20 0.050 1.23 0.050–0.157 1.23–2.25 

Clear Lakes, Alkaline ≤ 40 PCU 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 longterm 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). bBaseline 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. dPlatinum Cobalt Units (PCU) assessed as true color free from turbidity. Long-term average color based on a rolling average of up to seven 

years using all available lake color data. e If alkalinity data are unavailable, a specific conductance of 250 micromhos/cm may be substituted. 

f Chlorophyll a is defined as corrected chlorophyll, or the concentration of chlorophyll a remaining after the chlorophyll degradation product, 

phaeophytin a, has been subtracted from the uncorrected chlorophyll a measurement. 

(2) Criteria for streams. 

(i) The applicable instream protection 

value (IPV) criterion for total nitrogen 

(TN) and total phosphorus (TP) for 

streams within each respective nutrient 

watershed region is shown in the 

following table: 

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 longterm average of annual geometric mean values shall not surpass the listed concentration values. (Duration = annual; Frequency = not to be exceeded more than once in a three-year period or as a long-term average). bPanhandle 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. cBone Valley region includes the following watersheds: Tampa Bay Watershed, Sarasota Bay Watershed, and Charlotte Harbor Watershed. dPeninsula 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. 

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(ii) Criteria for protection of 

downstream lakes. 

(A) The applicable total phosphorus 

criterion-magnitude for a stream that 

flows into downstream lakes is the more 

stringent of the value from the 

preceding table in paragraph (c)(2)(i) of 

this section or a downstream lake 

protection value derived from the 

following equation to protect the 

downstream lake: 

[] [] TP

c

S TP

f

= + L w ( ) 1 1 τ

where: 

[TP]S is the total phosphorus (TP) 

downstream lake protection value, mg/L 

[TP]L is applicable TP lake criterion, mg/L 

cf is the fraction of inflow due to all 

streamflow, 0 ≤ cf ≤ 1 

tw is lake’s hydraulic retention time (water 

volume divided by annual flow rate) 

The term 

( ) 1+ τw

expresses the net phosphorus loss from the 

water column (e.g., via settling of sedimentsorbed phosphorus) as a function of the 

lake’s retention time. 

(B) The preset values for cf and tw, 

respectively, are 0.5 and 0.2. The State 

may substitute site-specific values for 

these preset values where the State 

determines that they are appropriate 

and documents the site-specific values 

in an easily accessible and publicly 

available location, such as an official 

State Web site. 

(iii) Criteria for protection of 

downstream estuarine waters. 

(A) The applicable criteria for a 

stream that flows into downstream 

estuary is the more stringent of the 

values from the preceding table in 

paragraph (c)(2)(i) of this section or 

downstream protection values derived 

from the following equation to protect 

the downstream estuary. EPA’s preset 

DPVs are listed in the Technical 

Support Document (TSD) for Florida’s 

Inland Waters located at 

www.regulations.gov, Docket ID No. 

EPA–HQ–OW–2009–0569, and 

calculated for each stream reach as the 

average reach-specific concentration (C ̄ i) 

equal to the average reach-specific 

annual loading rate (Li) divided by the 

average reach-specific flow (Q ̄ i) where: 

C kL

Q F i est

W i

= 1 ,

and where the terms are defined as 

follows for a specific or (ith) stream 

reach: 

C ̄ i maximum flow-averaged nutrient 

concentration for a specific (the ith) stream 

reach consistent with downstream use 

protection (i.e., the DPV) 

k fraction of all loading to the estuary that 

comes from the stream network resolved by 

SPARROW 

Lest protective loading rate for the estuary, 

from all sources 

Q ̄ w combined average freshwater discharged 

into the estuary from the portion of the 

watershed resolved by the SPARROW 

stream network 

Fi fraction of the flux at the downstream 

node of the specific (ith) reach that is 

transported through the stream network 

and ultimately delivered to estuarine 

eceiving waters (i.e. Fraction Delivered). 

DPVs may not exceed other criteria 

established for designated use protection in 

this section, nor result in an exceedance of 

other criteria for other water quality 

parameters established pursuant to Rule 

62–302, F.A.C. 

(B) The State may calculate 

alternative DPVs as above for C ̄ i except 

that Li is determined as a series of values 

for each reach in the upstream drainage 

area such that the sum of reach-specific 

incremental loading rates equals the 

target loading rate to the downstream 

water protective of downstream uses, 

taking into account that downstream 

reaches must reflect loads established 

for upstream reaches. Alternative DPVs 

may factor in additional nutrient 

attenuation provided by already existing 

landscape modifications or treatment 

systems, such as constructed wetlands 

or stormwater treatment areas. For 

alternative DPVs to become effective for 

Clean Water Act purposes, the State 

must provide public notice and 

opportunity for comment. 

(C) To use an alternative technical 

approach of comparable scientific rigor 

to quantitatively determine the 

protective load to the estuary and 

associated protective stream 

concentrations, the State must go 

through the process for a Federal sitespecific alternative criterion pursuant to 

paragraph (e) of this section. 

(3) Criteria for springs, spring runs, 

and clear streams. The applicable 

nitrate-nitrite criterion is 0.35 mg/L as 

an annual geometric mean not to be 

surpassed more than once in a three 

year period, nor surpassed as a longterm average of annual geometric mean 

values. In addition to this nitrate-nitrite 

criterion, criteria identified in paragraph 

(c)(2) of this section are applicable to 

clear streams. 

(4) Criteria for south Florida canals. 

The applicable criterion for chlorophyll 

a, total nitrogen (TN), and total 

phosphorus (TP) for canals within each 

respective canal geographic 

classification area is shown on the 

following table: 

Chlorophyll a 

(μg/L) a

Total phosphorus (TP) 

(mg/L) a b

Total nitrogen 

(TN) 

(mg/L) a

Canals .......................................................................................................................................... 4.0 0.042 1.6 

a Concentration values are based on annual geometric mean not to be surpassed more than once in a three-year period. In addition, the longterm 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). bApplies to all canals within the Florida Department of Environmental Protection’s South Florida bioregion, with the exception of canals within 

the Everglades Protection Area (EvPA) where the TP criterion of 0.010 mg/L currently applies. 

(5) Criteria for estuaries. [Reserved] 

(6) Criteria for coastal waters. 

[Reserved] 

(d) Applicability. 

(1) The criteria in paragraphs (c)(1) 

through (4) of this section apply to 

surface waters of the State of Florida 

designated as Class I (Potable Water 

Supplies) or Class III (Recreation, 

Propagation and Maintenance of a 

Healthy, Well-Balanced Population of 

Fish and Wildlife) water bodies 

pursuant to Rule 62–302.400, F.A.C., 

excluding wetlands, and apply 

concurrently with other applicable 

water quality criteria, except when: 

(i) State regulations contain criteria 

which are more stringent for a particular 

parameter and use; 

(ii) The Regional Administrator 

determines that site-specific alternative 

criteria apply pursuant to the 

procedures in paragraph (e) of this 

section; 

(iii) The State adopts and EPA 

approves a water quality standards 

variance to the Class I or Class III 

designated use pursuant to § 131.13 that 

meets the applicable provisions of State 

law and the applicable Federal 

regulations at § 131.10; or 


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(iv) The State adopts and EPA 

approves restoration standards pursuant 

to paragraph (g) of this section. 

(2) The criteria established in this 

section are subject to the State’s general 

rules of applicability in the same way 

and to the same extent as are the other 

federally-adopted and State-adopted 

numeric criteria when applied to the 

same use classifications. 

(i) For all waters with mixing zone 

regulations or implementation 

procedures, the criteria apply at the 

appropriate locations within or at the 

boundary of the mixing zones; 

otherwise the criteria apply throughout 

the water body including at the point of 

discharge into the water body. 

(ii) The State shall use an appropriate 

design flow condition, where necessary, 

for purposes of permit limit derivation 

or load and wasteload allocations that is 

consistent with the criteria duration and 

frequency established in this section 

(e.g., average annual flow for a criterion 

magnitude expressed as an average 

annual geometric mean value). 

(iii) The criteria established in this 

section apply for purposes of 

determining the list of impaired waters 

pursuant to section 303(d) of the Clean 

Water Act, subject to the procedures 

adopted pursuant to Rule 62–303, 

F.A.C., where such procedures are 

consistent with the level of protection 

provided by the criteria established in 

this section. 

(e) Site-specific alternative criteria. 

(1) Upon request from the State, the 

Regional Administrator may determine 

that site-specific alternative criteria 

shall apply to specific surface waters in 

lieu of the criteria established in 

paragraph (c) of this section. Any such 

determination shall be made consistent 

with § 131.11. 

(2) To receive consideration from the 

Regional Administrator for a 

determination of site-specific alternative 

criteria, the State must submit a request 

that includes proposed alternative 

numeric criteria and supporting 

rationale suitable to meet the needs for 

a technical support document pursuant 

to paragraph (e)(3) of this section. 

(3) For any determination made under 

paragraph (e)(1) of this section, the 

Regional Administrator shall, prior to 

making such a determination, provide 

for public notice and comment on a 

proposed determination. For any such 

proposed determination, the Regional 

Administrator shall prepare and make 

available to the public a technical 

support document addressing the 

specific surface waters affected and the 

justification for each proposed 

determination. This document shall be 

made available to the public no later 

than the date of public notice issuance. 

(4) The Regional Administrator shall 

maintain and make available to the 

public an updated list of determinations 

made pursuant to paragraph (e)(1) of 

this section as well as the technical 

support documents for each 

determination. 

(5) Nothing in this paragraph (e) shall 

limit the Administrator’s authority to 

modify the criteria in paragraph (c) of 

this section through rulemaking. 

(f) Effective date. All criteria will be 

in effect [date 60 days after publication 

of final rule]. 

(g) Restoration Water Quality 

Standards (WQS). The State may, at its 

discretion, adopt restoration WQS to 

allow attainment of a designated use 

over phased time periods where the 

designated use is not currently 

attainable as a result of nutrient 

pollution but is attainable in the future. 

In establishing restoration WQS, the 

State must: 

(1) Demonstrate that the designated 

use is not attainable during the time 

periods established for the restoration 

phases based on one of the factors 

identified in § 131.10(g)(1) through (6); 

(2) Specify the designated use to be 

attained at the termination of the 

restoration period, as well as the criteria 

necessary to protect such use, provided 

that the final designated use and 

corresponding criteria shall include, at 

a minimum, uses and criteria that are 

consistent with CWA section 101(a)(2) ; 

(3) Establish interim restoration 

designated uses and water quality 

criteria, that apply during each phase 

that will result in maximum feasible 

progress toward the highest attainable 

designated use and the use identified in 

paragraph (g)(2) of this section. Such 

interim uses and criteria may not 

provide for further degradation of a 

water body and may be revised prior to 

the end of each phase in accordance 

with §§ 131.10 and 131.20 and 

submitted to EPA for approval; 

(4) Establish the time periods for each 

restoration phase that will result in 

maximum feasible progress toward the 

highest attainable use and the 

designated use identified in paragraph 

(g)(2) of this section, except that the sum 

of such time periods shall not exceed 

twenty years from the initial date of 

establishment of the restoration WQS 

under this section; 

(5) Specify the spatial extent of 

applicability for all affected waters; 

(6) Meet the requirements of §§ 131.10 

and 131.20; and 

(7) Include, in its State water quality 

standards, a specific provision that if 

the interim restoration designated uses 

and criteria established under paragraph 

(g)(3) of this section are not met during 

any phased time period established 

under paragraph (g)(4) of this section, 

the restoration WQS will no longer be 

applicable and the designated use and 

criteria identified in paragraph (g)(2) of 

this section will become applicable 

immediately. 

(8) Provide that waters for which a 

restoration water quality standard is 

adopted will be recognized as impaired 

for the purposes of listing impaired 

waters under section 303(d) of the CWA 

until the use designated identified in 

paragraph (g)(2) of this section is 

attained. 

[FR Doc. 2010–1220 Filed 1–25–10; 8:45 am] 

BILLING CODE 6560–50–P 

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