FINAL

FLORIDA DEPARTMENT OF ENVIRONMENTAL PROTECTION

Division of Water Resource Management, Bureau of Watershed Management

SOUTHEAST DISTRICT • ST. LUCIE – LOXAHATCHEE BASIN

TMDL Report

Nutrient and Dissolved Oxygen 

TMDL for the St. Lucie Basin

Keith Parmer, PhD

Kristina Laskis

Robert McTear

Rhonda Peets

October 2008
ii

Acknowledgments

This study could not have been accomplished without significant support and assistance 

provided by Florida Department of Environmental Protection-Tallahassee and Southeast

District Offices, the South Florida Water Management District, County officials, 

Environmental Advocacy Groups, consultants, and other stakeholders who volunteered 

to participate or whose participation was requested. 

Editorial assistance provided by Jennifer Gihring, Linda Lord, and Jan Mandrup-Poulsen.

Note: All maps found in this document were prepared by Robert McTear and are for 

illustrative purposes only. They are a representation of ground conditions and are not 

intended for delineations or analysis of the features shown. 

For additional information on the watershed management approach and impaired waters 

in the St. Lucie - Loxahatchee Basin, contact:

Jennifer Gihring

Florida Department of Environmental Protection

Bureau of Watershed Management

Watershed Planning and Coordination Section

2600 Blair Stone Road, Mail Station 3565

Tallahassee, FL 32399-2400

Email: Jennifer.Gihring@dep.state.fl.us

Phone: (850) 245–8418

Fax: (850) 245–8434

Access to all data used in the development of this report can be obtained by contacting:

Keith Parmer, PhD.

Florida Department of Environmental Protection

Bureau of Watershed Management

Watershed Assessment Section

2600 Blair Stone Road, Mail Station 3555

Tallahassee, FL 32399-2400

Email: Keith.Parmer@dep.state.fl.us

Phone: (850) 245–8465

Fax: (850) 245–8444
iii

Contents 

EXECUTIVE SUMMARY ______________________________________________ x

Chapter 1: INTRODUCTION___________________________________1

1.1 Purpose of Report________________________________________________ 1

1.2 Identification of Waterbody ________________________________________ 1

St. Lucie Basin __________________________________________________ 1

Planning Units and WBIDs of the St. Lucie Basin ________________________ 3

MS4 Areas in the St. Lucie Basin ____________________________________ 5

1.3 Background_____________________________________________________ 9

1.3.1 Development of TMDL ________________________________________ 9

Chapter 2: DESCRIPTION OF WATER QUALITY PROBLEM _______10

2.1 Statutory Requirements and Rulemaking History _____________________ 10

2.2 Information on Verified Impairment_________________________________ 10

Chapter 3: DESCRIPTION OF APPLICABLE WATER QUALITY 

STANDARDS AND TARGETS_______________________13

3.1 Classification of the Waterbody and Criterion Applicable to the TMDL____ 13

3.2 Applicable Water Quality Standards and Numeric Water Quality 

Targets _______________________________________________________ 13

3.2.1 Interpretation of Dissolved Oxygen Criterion ______________________ 13

3.2.2 Interpretation of Biochemical Oxygen Demand Criterion _____________ 13

3.2.3 Interpretation of Narrative Nutrient Criterion_______________________ 13

3.2.4 Factors That Influence Nutrient Concentrations ____________________ 14

3.2.5 Factors That Influence Dissolved Oxygen ________________________ 14

Chapter 4: ASSESSMENT OF SOURCES_______________________16

4.1 Types of Sources _______________________________________________ 16

4.2 Potential Point Sources of TN, TP, and BOD in the St. Lucie Basin 

(WBIDs 3193, 3194, 3194B, 3197, 3200, 3210, 3210A, 3211, and 3218) ____ 16

4.2.1 NPDES Wastewater Facilities _________________________________ 16

4.2.2 Municipal Separate Storm Sewer System Permittees _______________ 18

4.2.3 Lake Okeechobee __________________________________________ 18

4.2.4 Groundwater_______________________________________________ 18

Chapter 5: DETERMINATION OF ASSIMILATIVE CAPACITY_______20

5.1 Target Nutrient Reduction Goals___________________________________ 20

5.1.1 IRL-S Targets______________________________________________ 20

5.1.2 Updated IRL-S Calculations and Links to Seagrass_________________ 21

5.1.3 Statewide Estuary Descriptive Statistics _________________________ 21

5.1.4 Comparison of Targets_______________________________________ 22
iv

5.2 Data Used in the Determination of the TMDL _________________________ 22

5.3 TMDL Development Process ______________________________________ 23

5.3.1 Modeled Flows _____________________________________________ 24

5.3.2 Measured Nutrient Concentration Data __________________________ 26

5.3.3 Flow Duration Curves________________________________________ 28

5.3.4 Load Duration Curves _______________________________________ 30

5.3.5 Annual Existing and Allowable Loads____________________________ 32

Chapter 6: DETERMINATION OF THE TMDL ____________________36

6.1 Expression and Allocation of the TMDL _____________________________ 36

6.2 Load Allocation _________________________________________________ 37

6.3 Wasteload Allocation ____________________________________________ 38

6.3.1 NPDES Wastewater Discharges _______________________________ 38

6.3.2 NPDES Stormwater Discharges________________________________ 38

6.4 Margin of Safety ________________________________________________ 38

Chapter 7: NEXT STEPS: IMPLEMENTATION PLAN 

DEVELOPMENT AND BEYOND _____________________39

7.1 Basin Management Action Plan____________________________________ 39

References _______________________________________________40

Appendix A _______________________________________________43

Background Information on Federal and State Stormwater Programs _______ 43

Appendix B _______________________________________________44

2004-05 Level 1 and Level 2 FLUCCS Landuse Figures for the St. Lucie 

Basin (WBIDs 3193, 3194, 3194B, 3197, 3200, 3210, 3210A, 3211, and 

3218,) ________________________________________________________ 44

Appendix C _______________________________________________53

Total Number of Samples and Annual TN and TP Mean Concentrations by 

WBID for the St. Lucie Basin (WBIDs 3193, 3194, 3194B, 3197, 3200, 

3210, 3210A, 3211, and 3218) _____________________________________ 53

Appendix D _______________________________________________58

Total Number of Samples and BOD Mean Concentrations by WBID for the 

St. Lucie Basin (WBIDs 3193, 3194, 3194B, 3197, 3200, 3210, 3210A, 

3211, and 3218) ________________________________________________ 58

Appendix E _______________________________________________59

Impaired WBID Maps with Sampling Station Locations, Yearly Statistical 

Values, and 10-year Average Flow_________________________________ 59

Appendix F _______________________________________________68
v

Outlier Analysis Summary Results ____________________________________ 68
vi

List of Tables

Table 2.1. Verified Impaired Listings for Nutrients and Dissolved Oxygen for 

the St. Lucie Basin (WBIDs 3193, 3194, 3194B, 3197, 3200, 3210, 

3210A, 3211, and 3218)_______________________________________ 11

Table 4.1 NPDES Permitted Wastewater Facilities __________________________ 17

Table 5.1 Target Method Summary ______________________________________ 22

Table 5.2 WaSh Estimated Flows with Annual Existing and Allowable TN 

Loads _____________________________________________________ 33

Table 5.3 WaSh Estimated Flows with Annual Existing and Allowable TP 

Loads _____________________________________________________ 34

Table 5.4 Annual Existing and Allowable BOD Concentrations _________________ 34

Table 6.1 TMDL Components for the St. Lucie Basin_________________________ 37

Table C.1 WBID 3193 Number of Samples and Annual TN and TP 

Concentrations ______________________________________________ 53

Table C.2 WBID 3194 Number of Samples and Annual TN and TP 

Concentrations ______________________________________________ 53

Table C.3 WBID 3194B Number of Samples and Annual TN and TP 

Concentrations ______________________________________________ 54

Table C.4 WBID 3197 Number of Samples and Annual TN and TP 

Concentrations ______________________________________________ 54

Table C.5 WBID 3200 Number of Samples and Annual TN and TP 

Concentrations ______________________________________________ 55

Table C.6 WBID 3210 Number of Samples and Annual TN and TP 

Concentrations ______________________________________________ 55

Table C.7 WBID 3210A Number of Samples and Annual TN and TP 

Concentrations ______________________________________________ 56

Table C.8 WBID 3211 Number of Samples and Annual TN and TP 

Concentrations ______________________________________________ 56

Table C.9 WBID 3218 Number of Samples and Annual TN and TP 

Concentrations ______________________________________________ 57

Table D.1 BOD Average Concentration Values and Number of Samples from 

1996 - Present ______________________________________________ 58

Table D.2 BOD Average Concentration Values and Number of Samples from 

1996 - 2005 ________________________________________________ 58
vii

List of Figures

Figure 1.1 Location of the St. Lucie Basin in St. Lucie and Martin Counties _________ 6

Figure 1.2 Planning Units and WBIDs of the St. Lucie Basin_____________________ 7

Figure 1.3 Key Watershed Features of the St. Lucie Basin ______________________ 8

Figure 2.1 Verified Impaired WBIDs for Nutrients and Dissolved Oxygen for 

the St. Lucie Basin (WBIDs 3193, 3194, 3194B, 3197, 3200, 3210, 

3210A, 3211, and 3218)_______________________________________ 12

Figure 4.1 Contributing Phase II MS4 Permit Jurisdictions _____________________ 19

Figure 5.1 Modeled Flows to Estuary with Lake Okeechobee ___________________ 25

Figure 5.2 Modeled Flows to Estuary without Lake Okeechobee_________________ 25

Figure 5.3 Annual Average Total Nitrogen (mg/L) for each WBID ________________ 27

Figure 5.4 Annual Average Total Phosphorus (mg/L) for each WBID _____________ 27

Figure 5.5 WBID 3200 Flow Duration Curve 1996-2005 _______________________ 29

Figure 5.6 WBID 3194 Flow Duration Curve 1996-2005 _______________________ 29

Figure 5.7 WBID 3200 TP Load Duration Curve 1996-2005 ____________________ 31

Figure 5.8 WBID 3194 TN Load Duration Curve 1996-2005 ____________________ 31

Figure 5.9 Current and Target Average Annual Total Nitrogen Loads _____________ 35

Figure 5.10 Current and Target Average Annual Total Phosphorus Loads _________ 35

Figure B.1 WBID 3193 2004-05 Level 1 and Level 2 FLUCCS Landuse ___________ 44

Figure B.2 WBID 3194 2004-05 Level 1 and Level 2 FLUCCS Landuse ___________ 45

Figure B.3 WBID 3194B 2004-05 Level 1 and Level 2 FLUCCS Landuse__________ 46

Figure B.4 WBID 3197 2004-05 Level 1 and Level 2 FLUCCS Landuse ___________ 47

Figure B.5 WBID 3200 2004-05 Level 1 and Level 2 FLUCCS Landuse ___________ 48

Figure B.6 WBID 3210 2004-05 Level 1 and Level 2 FLUCCS Landuse ___________ 49

Figure B.7 WBID 3210A 2004-05 Level 1 and Level 2 FLUCCS Landuse__________ 50

Figure B.8 WBID 3211 2004-05 Level 1 and Level 2 FLUCCS Landuse ___________ 51

Figure B.9 WBID 3218 2004-05 Level 1 and Level 2 FLUCCS Landuse ___________ 52

Figure E.1 WBID 3193 Sampling Locations and Data _________________________ 59

Figure E.2 WBID 3194 Sampling Locations, Data, and Flow ____________________ 60

Figure E.3 WBID 3194B Sampling Locations, Data, and Flow___________________ 61

Figure E.4 WBID 3197 Sampling Locations, Data, and Flow ____________________ 62

Figure E.5 WBID 3200 Sampling Locations, Data, and Flow ____________________ 63

Figure E.6 WBID 3210 Sampling Locations, Data, and Flow ____________________ 64

Figure E.7 WBID 3210A Sampling Locations, Data, and Flow___________________ 65

Figure E.8 WBID 3211 Sampling Locations, Data, and Flow ____________________ 66

Figure E.9 WBID 3218 Sampling Locations, Data, and Flow ____________________ 67
viii

Websites

Florida Department of Environmental Protection, Bureau of 

Watershed Management

TMDL Program

http://www.dep.state.fl.us/water/tmdl/index.htm

Identification of Impaired Surface Waters Rule

http://www.dep.state.fl.us/water/tmdl/docs/AmendedIWR.pdf

STORET Program

http://www.dep.state.fl.us/water/storet/index.htm

2006 305(b) Report

http://www.dep.state.fl.us/water/tmdl/docs/2006_Integrated_Report.pdf

Criteria for Surface Water Quality Classifications

http://www.dep.state.fl.us/water/wqssp/classes.htm

Basin Status Reports and Water Quality Assessment Reports

http://www.dep.state.fl.us/water/tmdl/stat_rep.htm

U.S. Environmental Protection Agency

Region 4: Total Maximum Daily Loads in Florida

http://www.epa.gov/region4/water/tmdl/florida/

National STORET Program

http://www.epa.gov/storet/

U.S. Geological Survey

Groundwater Data Site

http://www.sflorida.er.usgs.gov/ddn_data/text/stl.html

South Florida Water Management District

Groundwater Data Site

http://www.sfwmd.gov/pls/portal/realtime.realtime_app.rtv2?p_op=FORT_PIERCE
ix

ACRONYMS AND ABBREVIATIONS

BMAP Basin Management Action Plan

BMPs Best Management Practices

BOD Biochemical Oxygen Demand

CBOD Carbonaceous Biochemical Oxygen Demand

CFR Code of Federal Regulations

cfs cubic feet per second

Chl-a Chlorophyll a

CWA Clean Water Act

DCIA Directly Connected Impervious Area

DMR Discharge Monitoring Report

DO Dissolved Oxygen

EMC Event Mean Concentration

EPA Environmental Protection Agency

ERP Environmental Resource Permit

FAC Florida Administrative Code

FDACS Florida Department of Agriculture and Consumer Affairs

FDEP Florida Department of Environmental Protection

FLUCCS Florida Land Use and Cover Classification System

FS Florida Statutes

FWRA Florida Watershed Restoration Act

GIS Geographical Information System

GUI Graphical User Interface

IFAS Institute of Food and Agricultural Services

IWR Impaired Waters Rule

LA Load Allocation

mg/L Milligrams per liter (also parts per million - ppm)

MOS Margin of Safety

MS4 Municipal Separate Storm Sewer System

NEP National Estuary Program

NPDES National Pollutant Discharge Elimination System

NPS Nonpoint Source

PS Point Source

SFWMD South Florida Water Management District

SOD Sediment Oxygen Demand

STORET EPA or FDEP STOrage and RETrieval Program

TMDL Total Maximum Daily Load

TN Total Nitrogen

TP Total Phosphorus

μg/L Micrograms per liter (also parts per billion - ppb)

USACE United States Army Corps of Engineers

USDA United States Department of Agriculture

USGS United States Geological Survey

WASH Watershed Model

WBID Water Body Identification

WLA Waste Load Allocation

WWW World Wide Web
x

EXECUTIVE SUMMARY 

1. Impaired Waters Rule (IWR) Listed Waterbody Information

Basin Group: Group II St. Lucie-Loxahatchee

Planning 

Unit Waterbody WBID Impairment Status & Details

Dissolved Oxygen Nutrients

Coastal

St. Lucie River Lower 

Estuary 3193 Not Impaired Impaired

North St. Lucie

North Fork St. Lucie 

River 3194

Impaired; linked to high TP and 

BOD Impaired

North St. Lucie North St. Lucie Estuary 3194B Impaired; linked to high TN Impaired

C-24 C-24 3197

Impaired; linked to high TP and 

BOD Impaired

C-23 C-23 3200 Impaired; linked to high TP Impaired

South St. Lucie South St. Lucie Estuary 3210 Not Impaired Impaired

South St. Lucie

South Fork St. Lucie 

River 3210A Impaired; linked to high TN Impaired

South St. Lucie Bessey Creek 3211 Impaired; linked to high TP Impaired

C-44 C-44 3218 Impaired; linked to high BOD Not Impaired

2. TMDL Endpoints:

TN Target: 0.72 mg/L; TP Target: 0.081 mg/L; BOD Target: 2.0 mg/L

3. Lead on TMDL: 

Florida Department of Environmental Protection

4. TMDL considers point or non-point sources: 

Point source (Municipal Separate Sewer Systems) 

5. Major NPDES dischargers into surface water: 

None
xi

6. TMDL Allocation:

Waterbody Parameter Daily TMDL

Loading

LA 

(% Reduction) MOS

St. Lucie Estuary

(3193)

TN 0.72 mg/L 21.4 Implicit

TP 0.081 mg/L 41.3 Implicit

North Fork St. Lucie River

(3194)

TN 384 lbs 25.0 Implicit

TP 43 lbs 42.2 Implicit

BOD 2.0 mg/L 74.0 Implicit

North Fork St. Lucie Estuary

(3194B)

TN 284 lbs 28.8 Implicit

TP 32 lbs 58.1 Implicit

C-24 Canal

(3197)

TN 956 lbs 51.8 Implicit

TP 108 lbs 72.2 Implicit

BOD 2.0 mg/L 33.3 Implicit

C-23 Canal

(3200)

TN 664 lbs 51.7 Implicit

TP 75 lbs 78.6 Implicit

South Fork St. Lucie Estuary

(3210)

TN 67 lbs 38.4 Implicit

TP 8 lbs 57.2 Implicit

South Fork St. Lucie River

(3210A)

TN 248 lbs 47.1 Implicit

TP 28 lbs 61.8 Implicit

Bessey Creek

(3211)

TN 82 lbs 23.9 Implicit

TP 9 lbs 51.2 Implicit

C-44 Canal (3218)

TN 666 lbs 51.2 Implicit

TP 75 lbs 55.0 Implicit

BOD 2.0 mg/L 69.7 Implicit

7. Additional Comments

This Total Maximum Daily Loads (TMDL) document provides information on the development of 

targets for the St. Lucie Basin. The basin is subdivided into water body identification units 

(WBID) as detailed in the document. There are nine impaired WBIDs that this TMDL addresses 

for dissolved oxygen (DO), nutrients, and biochemical oxygen demand (BOD). Although there 

are other WBIDs that contribute significant flows to the St. Lucie Estuary, these WBIDs are not 

considered in this TMDL because they already have TMDLs associated with them, are 

scheduled for TMDL development in the future, or have significant water improvement projects 

underway within their boundaries. 

The relationships between DO, nutrient concentration, and BOD are complex in any system, 

and the St. Lucie Estuary is a prime example. Processes that consume oxygen in the water 

column, such as the microbial breakdown of organic material and sediment oxygen demand 

(SOD), are fairly constant over the short term. Algal populations, however, can increase rapidly
xii

with high nutrient concentrations, and the production of oxygen as a result of photosynthesis 

during daylight hours and the respiration or consumption from the water column at night can 

result in large diurnal fluctuations of DO in the water column. As algal populations die, a fraction 

of algal biomass will become part of the organic material that will be broken down by microbes 

or settle to the bottom. The reductions proposed in this TMDL are expected to decrease 

nutrients to the point that the estuarine threshold of 11 μg/L chlorophyll-a will not be exceeded.

The reduction in nutrient loads is also expected to improve DO by reducing the diurnal 

fluctuations in DO and improving DO levels. The TMDL, by law, is designed to address 

concerns caused by the discharge of pollutants. Other factors that may lower DO, like 

hydrology or temperature, are not addressed as a part of TMDLs.

The development of a TMDL for a particular WBID is part of an adaptive management process 

that is reflected in the Florida Department of Environmental Protection (Department) rotating 

basin evaluations and basin management action plans. While this document provides TMDLs 

for impaired WBIDs, the TMDLs will be re-evaluated as part of the rotating basin evaluation 

process and as new data and tools are developed to assess and restore the impaired basins.
1

Chapter 1: INTRODUCTION

1.1 Purpose of Report

This report presents the Total Maximum Daily Load (TMDL) for nutrients and dissolved oxygen 

(DO) for the St. Lucie basin: WBIDs (WaterBody IDentification) 3193 (St. Lucie River Lower 

Estuary), 3194 (North Fork St. Lucie River), 3194B (North St. Lucie Estuary), 3197 (C-24 canal), 

3200 (C-23 canal), 3210 (South St. Lucie Estuary), 3210A (South Fork St. Lucie River), 3211 

(Bessey Creek), and 3218 (C-44 Canal). Using the methodology described in Rule 62-303,

Florida Administrative Code (F.A.C.), Identification of Impaired Surface Waters Rule (IWR)

(2001a), which identifies and verifies water quality impairments, the above WBIDs have been 

determined to be impaired for nutrients and dissolved oxygen except WBIDs 3193 and 3210 

which are only impaired for nutrients and WBID and 3218 which is only impaired for DO. The 

Verified List of impaired waters for the Group 2 St. Lucie – Loxahatchee Basin was adopted by

Secretarial Order, December 2004. Portions of the St. Lucie watershed appear on the 1998 

303(d) Consent Decree Listing for nutrients and DO. The TMDL process quantifies the amount 

of a pollutant that can be assimilated in a waterbody, identifies the sources of the pollutant, and 

recommends regulatory or other actions to be taken to achieve compliance with applicable 

water quality standards, based on the relationship between pollutant sources and instream 

water quality conditions. In this TMDL, thresholds for causative pollutants were developed 

through an annual average loading reduction from contributing source areas. Contributing 

source areas are basins and sub-basins that provide point and non-point source discharge to 

receiving waterbodies.

1.2 Identification of Waterbody

St. Lucie Basin

In the St. Lucie Basin (Figure 1.1), all waterbodies drain directly to either the St. Lucie Estuary 

(SLE) or the Southern Indian River Lagoon (IRL-S). The SLE watershed comprises 

approximately 832,500 acres in Martin and St. Lucie Counties. Within the watershed 

approximately 684,087 acres are agricultural and 117,387 acres are urban (SFWMD, 04-05).

The inland portion of the SLE is composed of the South Fork and the North Fork. The two forks 

converge at the Roosevelt Bridge to form a single waterbody that extends eastward, where it 

joins the IRL-S. The watershed contains 15 hydrologic basins, sub-basins, and over 40 named 

tributaries. Historically, this area included a much smaller natural watershed that directly 

contributed to the river system, and interior areas of Martin and St. Lucie counties contained 

large expanses of poorly drained wetlands that did not directly feed into the river and estuary

(Gunsalus, 2008). With the construction of drainage improvements in inland areas, the effective 

drainage area of the SLE and IRL-S expanded to include almost all of Martin and St. Lucie 

counties.

The C-44 canal serves as a flood control conveyance for Lake Okeechobee and transports 

water from the lake into the South Fork. The C-44 canal also transports runoff from agricultural 

areas in its sub-basin. The construction of canals C-23 and C-24 (in addition to C-44) provided 

connections between their respective sub-basins. C-23 and C-24 canals discharge to the North 

Fork. The C-25 canal receives agricultural runoff from northern St. Lucie County and areas to 

the north; it discharges directly into the Central Indian River Lagoon (C-IRL) across from the 
2

Fort Pierce Inlet. However, the C-25 canal is not included in this assessment because it does 

not discharge directly into the SLE. Rather, it discharges to the IRL and will be accounted for in 

a separate TMDL.

The St. Lucie Inlet is a man-made inlet that provides ocean access, as well as tidal exchange,

between the estuary and the Atlantic Ocean (Sime, 2005). Prior to construction of the St. Lucie 

Inlet, the SLE was a freshwater lagoon (FDEP, 2003). Due to extensive urban and agricultural 

drainage projects in the watershed of the SLE, the historic drainage basin area has been greatly 

expanded to almost 775 square miles (SFWMD, 2003).

The climate in St. Lucie and Martin Counties is subtropical, with annual rainfall averaging 

approximately 45.67 inches near Lake Okeechobee and 55.51 inches near the coast; however, 

rainfall amounts can vary greatly from year to year (SFWMD DBHYDRO). The majority of the 

watershed’s annual rainfall comes during the wet season (May through October) from summer 

thunderstorms and tropical systems. High intensity rain events with short duration 

thunderstorms are common during the wet season in south Florida (Broward County, 2003). 

The dry season rainfall (November through April) usually stems from frontal systems that can 

produce significant rainfall, but occur less frequently than storms during the wet season. At 

times, this pattern is disrupted by a long-term weather pattern known as El Niño, which causes 

wetter winters and drier summers (FDEP, 2001). The average summer temperature is 84o

F, 

and the average winter temperature is 64o

F (NOAA, 2008).

The topography of the SLE and IRL-S watershed reflects its location within southeastern 

Florida. Elevations range in the western part of the sub-basin around 10 to 15 feet above sea 

level and in the eastern part of the sub-basin near the coast around 5 to 10 feet above sea level. 

The predominant soil types are moderately to well-drained shelly sand and clay and medium 

fine sand and silt (FDEP, 2008). 

In 2007, the Florida Legislature expanded the Lake Okeechobee Protection Act (LOPA, Section 

373.4595, F.S.) to strengthen protection for the Northern Everglades watersheds by 

incorporating restoration efforts for the St. Lucie and Caloosahatchee watersheds, including the 

estuaries. The Northern Everglades & Estuaries Protection Program (NEEPP):

• Recognizes that Lake Okeechobee and the Caloosahatchee and St. Lucie Watersheds are 

critical water resources of the state

• Recognizes the TMDL program as a primary means of addressing water quality problems 

related to phosphorus and other pollutants

• Requires development of Watershed Protection Plans for the St. Lucie and Caloosahatchee 

watersheds by January 1, 2009

• Expands the use of the Save Our Everglades Trust Fund for Northern Everglades 

restoration

• Extends the Save Our Everglades Trust Fund through 2020

The NEEPP specifies that the estuary programs shall provide for consideration of all water 

quality issues needed to meet the TMDL targets, in addition to a number of other substantive 

requirements. Pollutant load reductions identified in this TMDL and established in accordance 

with section 403.067 F.S. shall serve as a program objective in the NEEPP process. The South 

Florida Water Management District (SFWMD), the Department of Agriculture and Consumer 

Services (DACS), and the Florida Department of Environmental Protection (FDEP) are working 

closely together to integrate the TMDL and NEEPP processes to meet statutory requirements.
3

Planning Units and WBIDs of the St. Lucie Basin

To provide a smaller-scale geographic basis for assessing, reporting, and documenting water 

quality improvement projects, FDEP divides basin groups into smaller areas called planning 

units. Planning units help organize information and management strategies around prominent 

sub-basin characteristics and drainage features. To the extent possible, planning units were 

chosen to reflect sub-basins that had previously been defined by SFWMD. The St. Lucie 

watershed contains six planning units: North St. Lucie, C-23, C-24, C-44, South St. Lucie, and 

Coastal. Water quality assessments were conducted on individual waterbody segments within 

each planning unit. Each waterbody segment is assigned a unique WBID number (FDEP, 

2003). Refer to Figure 1.2 for planning units and WBIDs in the St. Lucie basin.

For illustrative purposes, the spatial distribution and acreage of different landuse categories 

were identified using 2004-05 landuse coverage data (scale 1:60,000) provided by the SFWMD. 

Landuse categories were lumped into Level 1 and Level 2 Florida Land Use Cover and 

Classification System (FLUCCS) categories (Harper and Baker, 2003). Refer to Appendix B for 

individual WBID landuse figures. 

North St. Lucie

The North St. Lucie planning unit encompasses 120,776 acres, with approximately 36,657 acres

(30.35%) of agriculture and 49,994 acres (41.39%) of urban. It extends from Ft. Pierce Inlet to 

the St. Lucie Inlet and westward to the C-24 Canal. Historically, the North Fork St. Lucie River 

and its main tributaries (Ten Mile and Five Mile Creeks) drained naturally into the St. Lucie 

Estuary. The planning unit also includes the North St. Lucie Water Control District where 

drainage is to Ten Mile Creek, C-24, and C-25. It contains WBIDs 3194, 3194A, 3194B, 3194C, 

and 3194D. For the purpose of this TMDL, WBIDs 3194 and 3194B have been included 

because they are impaired for nutrients and dissolved oxygen. WBIDs 3194 and 3194B 

encompass 34,372 acres (28.4%) of the North St. Lucie planning unit. These WBIDs also cover 

most of Port St. Lucie, the southeastern portion of the St. Lucie County Municipal Separate 

Storm Sewer System (MS4) area, and the northern portions of Stuart and urban Martin County. 

Ten Mile Creek (WBID 3194A) is currently impaired based on data from Run 33 of the IWR

because its DO concentration routinely falls below the state standard of 5 mg/L (related to 

elevated TP). It is also on the consent decree list with a due date of 2010. The Department 

considered expediting the schedule and including Ten Mile Creek in this TMDL. However, 

SFWMD has made, and continues to make, progress in the construction, operation, and 

refinement of the Ten Mile Creek Water Preserve Area. Thus, the Department decided to not 

include WBID 3194A in this TMDL and will wait for the resulting water quality data before 

developing TMDL load reduction requirements for Ten Mile Creek. This WBID will be revisited 

in 2010 and the performance of the stormwater treatment area (STA), along with any changes in 

water quality, will be taken into consideration. If the Ten Mile project is achieving the expected 

nutrient reduction benefits, a TMDL may not be needed for this waterbody.

South St. Lucie

The South St. Lucie planning unit encompasses 65,275 acres with approximately 16,948 acres 

(25.96%) of agriculture and 21,203 acres (32.48%) of urban. This planning unit is located in 

Martin County and includes most of Stuart (in the southeastern part), plus portions of Palm City, 

Coral Gardens, Gomez, and Hobe Sound. This planning unit includes the natural drainage of 

the South Fork St. Lucie River and contains several other drainage areas including Basin 2, 
4

Bessey Creek (Basin 4), Basin 5, Danforth Creek (Basin 6), and the Tidal St. Lucie. It also 

includes the outlet of the C-44 canal. All of these drainage areas converge at the South Fork of 

the St. Lucie Estuary, except Bessey Creek which empties into the North Fork of the estuary. It 

contains WBIDs 3210, 3210A, 3210B, 3211, 3211A, 3215, 3217, and 3220. WBIDs 3210, 

3210A, and 3211 encompass 18,949 acres (29.0%) of the South St. Lucie planning unit. 

Coastal

The Coastal planning unit comprises 175,496 acres. The IRL-S and most of the SLE are 

included as well as three inlets to the Atlantic Ocean: the Ft. Pierce, St. Lucie, and Loxahatchee 

Inlets. Historically, the IRL-S had a long and narrow drainage basin. At the turn of the century, 

extensive drainage systems were constructed that have more than doubled the size of the 

drainage basin of the lagoon. Smaller drainage systems were also constructed to provide 

stormwater drainage for individual residential, commercial, and agricultural development 

projects. These drainage systems discharge large volumes of freshwater from urban and 

agricultural runoff to the IRL-S (NEP, 1996). This planning unit contains WBIDs 3166, 3190, 

3193, 3208, 3208A, 3226, 3226B, 5003A, 8101, 8102, 8103, and 8104. WBID 3193 is almost 

entirely open water which encompasses 3,226 acres (1.84%) of the Coastal planning unit. 

WBID 3193 also covers a small portion of the northeastern Stuart MS4 area.

C-23 & C-24 Canals

The C-23 planning unit, WBID 3200, encompasses 106,840 acres. The C-24 planning unit,

WBID 3197, encompasses 109,015 acres. C-23 and C-24 canals discharge water into the 

North Fork of the St. Lucie Estuary. These canals transport loads of nutrients and eroded 

sediment to the estuary with slugs of freshwater that create fluctuations in estuarine salinity 

levels. Urban and residential areas continue to expand in the coastal areas with urban 

stormwater runoff and seepage from septic tanks also contributing to the water quality problems 

in the streams and canals. As a result of C-23 and C-24 inflows, parts of the St. Lucie Estuary 

(SLE) are impaired for nutrients and DO. Nutrient loads, salinity fluctuations, and accumulations 

of sediment stress the estuarine ecology. Other evidence to support impairment status was 

gathered through a FDEP Southeast District Biological Survey for the SLE segments. Sediment 

accumulation, decline of seagrasses and oysters, algal blooms, fish kills, and low diversity of 

benthic macro invertebrates in the SLE comprise this body of evidence (Graves et al., June 

2002). Within the C-23 planning unit approximately 80,300 acres (75.16%) are agricultural and 

2,753 acres (2.58%) are urban. Within the C-24 planning unit approximately 75,689 acres 

(69.43%) are agricultural and 12,682 acres (11.63%) are urban.

C-44

The C-44 planning unit, WBID 3218, encompasses 123,078 acres. It includes the C-44 Canal 

which is part of the navigational route between the east and west coasts of Florida, and directly 

connects Lake Okeechobee to the St. Lucie River. Agricultural drainage canals connect 

extensively along the entire length of the canal. Within the planning unit approximately 78,927

acres (64.13%) are agricultural and 3,122 acres (2.54%) are urban. This area also includes a 

portion of urban Martin County.
5

MS4 Areas in the St. Lucie Basin

City of Port St. Lucie

The city of Port St. Lucie is approximately 45,740 acres, over 70% of which is urban. According 

to the U.S. Census Bureau, the population density in the city of Port St. Lucie in 2000 was 1,320 

people per square mile. The Bureau reports that the total population for the city was 88,769 

residing in 36,908 housing units (U.S. Census Bureau Website, 2008).

City of Stuart

The city of Stuart is approximately 5,648 acres, over half of which is urban. According to the 

U.S. Census Bureau, the population density in the city of Stuart in 2000 was 2,308 people per 

square mile. The Bureau reports that the total population for the city was 14,633 residing in

8,879 housing units (U.S. Census Bureau Website, 2008).

Martin County

The Martin County MS4 area was unable to be obtained at the time this document was written. 

The urban area is approximately 41,063 acres (DEP TIGER, 2003). According to the U.S. 

Census Bureau, the population density in Martin County in 2000 was 228 people per square 

mile. The Bureau reports that the total population for the county was 126,731 residing in 65,471 

housing units (U.S. Census Bureau Website, 2008).

St. Lucie County

The St. Lucie County MS4 area is approximately 186,157.71 acres, over 65% of which is 

agriculture. According to the U.S. Census Bureau, the population density in St. Lucie County in 

2000 was 337 people per square. The Bureau reports that the total population for the county 

was 192,695 residing in 91,262 housing units (U.S. Census Bureau Website, 2008).
6

Figure 1.1 Location of the St. Lucie Basin in St. Lucie and Martin 

Counties
7

Figure 1.2 Planning Units and WBIDs of the St. Lucie Basin 
8

Figure 1.3 Key Watershed Features of the St. Lucie Basin
9

1.3 Background

This report was developed as part of the Department’s watershed management approach for 

restoring and protecting state waters and addressing TMDL Program requirements. The 

watershed approach, which is implemented using a cyclical management process that rotates 

through the state’s 52 river basins over a 5-year cycle, provides a framework for implementing 

the TMDL Program–related requirements of the 1972 federal Clean Water Act and the 1999 

Florida Watershed Restoration Act (FWRA) (Chapter 99-223, Laws of Florida).

A TMDL represents the maximum amount of a given pollutant that a waterbody can assimilate 

and still meet water quality standards, including its applicable water quality criteria and its 

designated uses. TMDLs are developed for waterbodies that are verified as not meeting their 

water quality standards. They provide important water quality restoration goals that will guide 

restoration activities.

This TMDL report will be followed by the development and implementation of a Basin 

Management Action Plan, or BMAP, which will be designed to reduce the amount of TN and TP 

needed to address the nutrient and DO impairments in the St. Lucie watershed. The action 

plan’s activities will depend heavily on the active participation of the SFWMD, Martin County 

Division of Natural Resources Environmental Section, St. Lucie County Division of Natural 

Resources Environmental Section, Fish and Wildlife Commission (FWC), University of Florida -

Institute of Food and Agriculture Sciences (UF-IFAS), Florida Department of Transportation

(FDOT), local businesses, and other stakeholders. The Department will work with these 

organizations and individuals to undertake or continue reductions in the discharge of pollutants 

and achieve the established TMDL targets.

1.3.1 Development of TMDL

This TMDL was developed in cooperation with the SFWMD, Martin County Division of Natural 

Resources Environmental Section, St. Lucie County Division of Natural Resources 

Environmental Section, Fish and Wildlife Commission (FWC), and University of Florida - IFAS. 

There was also active coordination with a variety of local stakeholders throughout the TMDL 

development process. This coordination included meetings and teleconference discussions

between DEP representatives, County officials, Environmental Advocacy Groups, consultants, 

and other stakeholders who participated in the process.
10

Chapter 2: DESCRIPTION OF WATER QUALITY 

PROBLEM

2.1 Statutory Requirements and Rulemaking History

Section 303(d) of the Clean Water Act requires states to submit to the U.S. Environmental 

Protection Agency (EPA) a list of surface waters that do not meet applicable water quality 

standards (impaired waters) and establish a TMDL for each pollutant causing the identified 

impairment of the listed waters on a schedule. The Department has developed these lists, 

commonly referred to as 303(d) lists, since 1992. The list of impaired waters in each basin is 

also required by the FWRA (Subsection 403.067[4], Florida Statutes [F.S.]), and the Department 

is developing basin-specific lists as part of the watershed management cycle. 

The 1998 303(d) list included portions of the St. Lucie Basin (FDEP, 1998). However, the 

FWRA (Section 403.067, F.S.) stated that all previous Florida 303(d) lists were for planning 

purposes only and directed the Department to develop, and adopt by rule, a new science-based 

methodology to identify impaired waters. After a long rulemaking process, the Environmental 

Regulation Commission (ERC) adopted the new methodology as Rule 62-303, F.A.C.

Identification of the IWR, (FDEP, 2001a); the IWR was subsequently modified in 2006 and 

2007. The list of waters for which impairments have been verified using the methodology in the 

IWR is referred to as the Verified List.

2.2 Information on Verified Impairment

The Department used the IWR to assess water quality impairments and has verified the 

impairments for nutrients and low DO in the St. Lucie basin (Table 2.1 and 2.2). The basin

contains the following impaired WBIDs: 3193, 3194, 3194B, 3197, 3200, 3210, 3210A, 3211, 

and 3218. The locations of these WBIDs are shown in Figure 2.1. WBIDs were verified as 

impaired for DO based on data that indicated an exceedance rate greater than or equal to 10 

per cent. The Class III freshwater water quality criterion is that DO shall not be less than 5.0 

mg/L. Normal daily and seasonal fluctuations above these levels shall be maintained. For 

Class III marine water bodies, the DO shall not average less than 5.0 mg/L in a 24 hour period 

and shall never be less than 4.0 mg/L. Normal daily and seasonal fluctuations above these 

levels shall be maintained. WBIDs were verified as impaired for nutrients based on annual 

chlorophyll-a data exceeding the nutrient narrative criteria of 20 μg/L for freshwater and 11 μg/L 

for marine waters (IWR, 62-302). The IWR data were based on samples collected between the 

01/1996 – 06/2003. The nutrient and DO data for the St. Lucie basin are available upon 

request.
11

Table 2.1. Verified Impaired Listings for Nutrients and Dissolved 

Oxygen for the St. Lucie Basin (WBIDs 3193, 3194, 3194B, 

3197, 3200, 3210, 3210A, 3211, and 3218)

Planning Unit Waterbody WBID Impairment Status & Details

Dissolved Oxygen Nutrients

Coastal

St. Lucie River Lower 

Estuary 3193 Not Impaired Impaired

North St. Lucie

North Fork St. Lucie 

River 3194 Impaired; linked to high TP and BOD Impaired

North St. Lucie North St. Lucie Estuary 3194B Impaired; linked to high TN Impaired

C-24 C-24 3197 Impaired; linked to high TP and BOD Impaired

C-23 C-23 3200 Impaired; linked to high TP Impaired

South St. Lucie South St. Lucie Estuary 3210 Not Impaired Impaired

South St. Lucie

South Fork St. Lucie 

River 3210A Impaired; linked to high TN Impaired

South St. Lucie Bessey Creek 3211 Impaired; linked to high TP Impaired

C-44 C-44 3218 Impaired; linked to high BOD Not Impaired
12

Figure 2.1 Verified Impaired WBIDs for Nutrients and Dissolved 

Oxygen for the St. Lucie Basin (WBIDs 3193, 3194, 3194B, 

3197, 3200, 3210, 3210A, 3211, and 3218)
13

Chapter 3: DESCRIPTION OF APPLICABLE WATER 

QUALITY STANDARDS AND TARGETS

3.1 Classification of the Waterbody and Criterion Applicable to the TMDL

Florida’s surface waters are protected for five designated use classifications, as follows:

Class I Potable water supplies

Class II Shellfish propagation or harvesting

Class III Recreation, propagation, and maintenance of a healthy, wellbalanced population of fish and wildlife

Class IV Agricultural water supplies

Class V Navigation, utility, and industrial use (there are no state waters 

currently in this class)

3.2 Applicable Water Quality Standards and Numeric Water Quality Targets

The St. Lucie Basin (WBIDs 3193, 3194, 3194B, 3197, 3200, 3210, 3210A, 3211, and 3218) is 

composed of Class III waterbodies, with a designated use of recreation, propagation, and 

maintenance of a healthy, well-balanced population of fish and wildlife. The Class III water 

quality criteria applicable to the impairment addressed by this TMDL are for DO and the 

narrative nutrient criteria.

3.2.1 Interpretation of Dissolved Oxygen Criterion

The DO criterion for Class III freshwater waterbodies states that DO shall not be less than 5.0 

mg/L. Normal daily and seasonal fluctuations above these levels shall be maintained. For 

Class III marine water bodies the DO shall not average less than 5.0 mg/L in a 24 hour period 

and shall never be less than 4.0 mg/L. Normal daily and seasonal fluctuations above these 

levels shall be maintained.

3.2.2 Interpretation of Biochemical Oxygen Demand Criterion

Florida’s BOD criterion is narrative. For any Class III freshwater, the BOD shall not be

increased so as to cause DO to be depressed below the applicable DO criterion, and in no

case, shall it be great enough to cause nuisance conditions. Natural freshwater systems with 

low nutrient levels have been observed to have BOD values less than 2.0 mg/L. The existence 

of elevated BOD (mean and median values > 2.0 mg/L) in several of the watersheds being 

assessed led to the conclusion that BOD levels were a negative influence on the DO 

concentrations. The current method detection limit is 2.0 mg/L for most determinations which 

practically sets a level for determining whether or not BOD contributes to depression of DO 

levels.

3.2.3 Interpretation of Narrative Nutrient Criterion

Florida’s nutrient criterion is narrative; nutrient concentrations of a body of water shall not be 

altered so as to cause an imbalance in natural populations of aquatic flora or fauna. The 
14

Department currently uses chlorophyll-a measurements as a surrogate measure for 

phytoplankton population. When chlorophyll-a concentrations above 20 μg/L are observed in 

freshwater systems or 11 μg/L in marine systems, there is an indication that primary producer 

population is out of balance and nutrient concentrations should be investigated. Accordingly, a 

nutrient-related target was needed to represent levels at which an imbalance in flora or fauna is 

expected to occur. While the IWR provides a threshold for nutrient impairment for streams and

estuaries based on annual average chlorophyll-a levels, these thresholds are not standards.

These thresholds were used in the assessment and verification of the WBIDs impaired for 

nutrients listed in this TMDL. 

3.2.4 Factors That Influence Nutrient Concentrations

The St. Lucie Estuary system receives nutrients from natural streams and rivers and structurecontrolled canal systems, surface water runoff, groundwater, and tidal influences. Nutrient 

enrichment in the Estuary has been ongoing for years as the result of both the urbanization of 

the coastal regions of St. Lucie and Martin Counties and agricultural activities in the western 

regions of the watershed. Landuse changes have affected the St. Lucie in two primary ways: 

increasing nutrient loads and hydrologic modifications.

Recent data compiled by Harper & Baker (2007) demonstrated that increasing intensity of 

landuse generally results in increasing nutrient runoff concentration (Harper & Baker, 2007, 

Table 4-17) and an increase in runoff volume (Harper & Baker, 2007, Figure 4-4). Both 

urbanization and increasing intensity of agricultural landuse (e.g. conversion from rangeland to 

a managed pasture) can result in increased delivery of nutrients to local receiving waters.

Specific agricultural activities that can contribute to the declining health of the system include 

water flow changes due to the creation of secondary and tertiary canal systems for use in 

irrigation and flood control and the introduction of nutrients via fertilization. Urbanization can 

result in reduction of pervious areas for infiltration of runoff, which contributes significantly to 

increased runoff and nutrient load (Harper & Baker, 2007). Other activities associated with 

urbanization also increase nutrient inputs such as the installation of septic tanks, sewage 

overflows, fertilizer usage, and the use of irrigation quality water in sprinkler systems in golf 

courses and new housing developments. The impact of agricultural and urban activities on 

eutrophication of receiving waters can be decreased through the implementation of best 

management practices (BMPs).

Natural processes also influence nutrient concentrations in the St. Lucie Watershed. In general, 

sediment that enters the system settles out of the water column, accumulating behind canal 

structures and on the bottom of the Estuary. Although data are sparse to quantify this factor, 

these sediments can contribute to increased SOD, thus lowering DO levels in the water column. 

Input and re-suspension of sediments also can decrease light penetration, reducing the light 

intensity with depth, thus reducing viability of submerged aquatic vegetation (SAV) and affecting 

typical nutrient and oxygen dynamics that would be associated with healthy seagrass systems.

3.2.5 Factors That Influence Dissolved Oxygen

The availability of DO in a marine or freshwater system is highly variable due to several factors. 

Oxygen is produced in the water column by photosynthesis and is consumed by respiration of 

plants, animals and aerobic bacteria, and by chemical reactions that occur in brackish waters 

due to the interaction of sunlight, humic and fulvic materials, as well as oxidation and reduction 

reactions. The ability of a system to absorb oxygen from the atmosphere is dependent on flow 

factors such as water depth and turbulence. Elevated nitrogen and phosphorus compounds 
15

contribute to excess algae growth. Under high nutrient levels, algae grow rapidly and raise DO

concentrations during daylight hours. Respiration (i.e. BOD) by the dense algal populations and 

other consumers reduce DO concentrations during the night. When phytoplankton cells die, 

they sink towards the bottom, and are decomposed by bacteria, a process (i.e. SOD) that 

further reduces DO in the water column. 

As mentioned above, factors that may cause significant oxygen depletion include BOD and 

SOD. BOD, including carbonaceous BOD (CBOD) and nitrogenous BOD (NBOD) may be the 

product of both naturally occurring oxygen use from the decomposition of organic materials, and 

the stabilization of waste products associated with nonpoint source runoff. The significance of 

any of these factors depends on the specific stream conditions. BOD related to microorganisms 

is called CBOD. The source material for CBOD is organic matter. CBOD results when oxygen 

is consumed by microorganisms in converting organic material into CO2, H20, nutrients, energy, 

and new cells. Algal cells contain organic chemicals that consume oxygen during 

decomposition. BOD related to chemical oxidation is called NBOD. The source materials for 

NBOD include organic matter that decays to ammonia, and ammonia entering the system 

through stormwater systems or runoff. Nitrification, the process of oxidizing ammonia to nitrates 

by microorganisms, requires almost 5 mg/L of DO (NBOD) for every mg/L of ammonia that is 

oxidized.

SOD is the overall demand for DO from the water column that is exerted by the combination of 

biological, biochemical, and chemical processes at the sediment-water interface. The primary 

sources of SOD are anaerobic (low-oxygen) chemical compounds in the riverbed sediments and 

particulate BOD (including algae and other sources of organic matter) that settle out of the water 

column. SOD is generally composed of biological respiration from benthic organisms and the 

biochemical (i.e., bacterial) decay processes in the top layer of deposited sediments. In addition 

to DO depletion, degradation of organic matter in the sediment results in the release of oxygendemanding (i.e., reduced) nutrients, metals, ammonium, iron, manganese, sulfide, and 

ammonia (Price et al, 1994). These soluble chemicals are released into the water and exert a 

relatively rapid (i.e., it occurs on a timescale of hours) oxygen demand as the reduced 

chemicals are oxidized. Some oxidation processes, such as nitrification of ammonia to nitrate, 

require bacteria and may be slower (i.e., days). In stratified waters, the sediment and the 

bottom layer of water are somewhat "trapped" and the oxygen is depleted as a result of decay 

of organic matter and lack of exchange of oxygenated water from upper layers (EPA, 2007). 

Estuarine waters are often considered to be stratified
16

Chapter 4: ASSESSMENT OF SOURCES

4.1 Types of Sources

An important part of the TMDL analysis is the identification of pollutant source categories, 

source subcategories, or individual sources of the pollutant or pollutants causing impairment in 

the watershed and the amount of pollutant loading contributed by each of these sources. 

Sources are broadly classified as either “point sources” or “nonpoint sources.” Historically, the 

term “point sources” has meant discharges to surface waters that typically have a continuous 

flow via a discernable, confined, and discrete conveyance, such as a pipe. Domestic and 

industrial wastewater treatment facilities (WWTFs) are examples of traditional point sources. In 

contrast, the term “nonpoint sources” was used to describe intermittent, rainfall-driven, diffuse 

sources of pollution associated with everyday human activities, including runoff from urban land, 

agriculture, silviculture, and mining; discharges from failing septic systems; and atmospheric 

deposition.

However, the 1987 amendments to the Clean Water Act (CWA) redefined certain nonpoint 

sources of pollution as point sources subject to regulation under the EPA’s National Pollutant 

Discharge Elimination System (NPDES) Program. These nonpoint sources included certain 

urban stormwater discharges, including those from local government master drainage systems, 

construction sites over five acres, and a wide variety of industries (see Appendix A for 

background information on the federal and state stormwater programs).

To be consistent with CWA definitions, the term “point source” is used to describe traditional 

point sources (such as domestic and industrial wastewater discharges) and stormwater systems 

requiring an NPDES stormwater permit when allocating pollutant load reductions required by a 

TMDL. However, the methodologies used to estimate nonpoint source loads do not distinguish 

between NPDES stormwater discharges and non-NPDES stormwater discharges, and as such, 

this source assessment section does not make any distinction between the two types of 

stormwater.

4.2 Potential Point Sources of TN, TP, and BOD in the St. Lucie Basin (WBIDs

3193, 3194, 3194B, 3197, 3200, 3210, 3210A, 3211, and 3218)

4.2.1 NPDES Wastewater Facilities

According to the FDEP Waste Application Facilities Report (WAFR) database, 15 NPDES 

permitted wastewater facilities exist in the St. Lucie basin (Table 4.1). These wastewater 

facilities are only permitted to discharge to surface water during a 25-year/72-hour storm event

making discharge from these facilities very infrequent. Facilities that have permitted discharges 

above this level are for cooling or dewatering, which are effectively discharging ambient water. 

Since this report is based on ambient conditions in the watershed, the infrequent discharge from 

the above mentioned facilities is not included in the overall reduction. If conditions change in 

the permits for any of the facilities mentioned, that change will be included as part of the 

restoration effort. 
17

Table 4.1 NPDES Permitted Wastewater Facilities

WBID Facility Name Facility ID

3194 St. Lucie County Fairgrounds FL0434698

3194 Prestige AB Mgmt Co LLC - Ft. Pierce FLG110569

3194 Rinker Materials of Florida Inc. W. Ft. Pierce Plant FLG110576

3194 Adonel Ft. Pierce Plant FLG110638

3197 Florida Rock industry FL0140406

3200 Gracewood Dairy FLA187577

3210 Tarmac America - Stuart Plant FL0126411

3210 Rinker Materials - Stuart Plant FLG110333

3210 Continental FL Matl - Stuart FLG110543

3218 Florida Power and Light Plant co- Martin County FL0030988

3218 Indian Town Cogeneration Plant Emergency Discharge FL0183750

3218 Payson Park Thoroughbred Training Center FLA413950

3218 Rinker Materials of Florida Inc. Indiantown FLG110724

3218 Circle K store # 7403 FLG912597

5003A Sailfish Point Utilities Corp FL0037001
18

4.2.2 Municipal Separate Storm Sewer System Permittees

A municipal separate storm sewer system (MS4) is a publicly owned conveyance or system of 

conveyances (e.g., ditches, curbs, catch basins, underground pipes, etc.) that is designed or 

used for collecting or conveying stormwater and that discharges to surface waters of the State. 

MS4 discharges are regulated by the FDEP under the NPDES Stormwater Program, outlined in 

Ch. 62-624, F.A.C. There are six permitted MS4s in the St. Lucie Basin: Martin County 

#FLR04E013, St. Lucie County #FLR04E029, City of Stuart #FLR04E031, City of Port St. Lucie 

#FLR04E001, Department of Transportation (FDOT) District 4 #FLR04E083, and Florida 

Turnpike Enterprise #FLR04E049. Figure 4.2 shows the extent of the MS4 permitted area for 

each local government. The spatial extent of the DOT and Florida Turnpike Enterprise MS4 

permitted area was unavailable at the time of TMDL development. 

4.2.3 Lake Okeechobee

Lake Okeechobee was connected to the St. Lucie Estuary by the creation of the C-44 Canal as 

an outlet to manage water levels in the Lake. Through this connection, the Lake is able to 

discharge freshwater to the C-44 Canal at a very high rate. These releases carry significant 

nutrient loads which have a known impact on the SLE watershed. Lake Okeechobee currently 

has a TMDL in place, adopted in May 2001, which calls for an annual load of 140 metric tons of 

phosphorus to Lake Okeechobee to achieve an in-lake target phosphorus concentration of 40 

ppb in the limnetic zone of the lake. It is the Department’s stance that any TMDL targets 

already in place shall be used as inputs into any connecting waterbodies thus, this document 

will assume that the Lake is meeting its target TP concentration of 40 ppb. Through modeling 

work done by SFWMD it has been determined that through the reduction of TP levels, TN levels 

will also decrease to a value of approximately 1.4 mg/L (Tom James, SFWMD, Pers. Comm. 

2008). 

4.2.4 Groundwater

Groundwater discharge as a potentially significant source of both water and chemicals to 

coastal areas has presented controversy as to the actual magnitude of groundwater discharge 

on both local and regional scales. This controversy is fueled by differences in the magnitude of 

the flux in different locations and the difficulties in quantifying the freshwater and seawater 

components of groundwater discharge. Groundwater and surface water are unequivocally 

associated in this region. A quick comparison of the USGS real-time groundwater monitoring 

website for the St. Lucie area with the SFWMD real-time gate, gauge, and stage web page 

demonstrate this phenomenon. Since the region is well-drained by an extensive canal network, 

the water quality at the control structures should be representative of the aquifer which provides 

seepage to the canal system and eventually the estuary. The hydrologic model which is used in 

this TMDL considers groundwater flow on a regional basis, including irrigation, seepage, and 

eventual expression in the canal system. Due to the high solubility of nutrients in water, 

groundwater is considered to be taken into account when samples are collected at the control 

structures and water quality sampling stations throughout the waterbodies.
19

Figure 4.1 Contributing Phase II MS4 Permit Jurisdictions
20

Chapter 5: DETERMINATION OF ASSIMILATIVE 

CAPACITY

5.1 Target Nutrient Reduction Goals

The assimilative capacity of the estuary was established by using target nutrient reduction goals 

at the Roosevelt Bridge, which were calculated during development of the South Indian River 

Lagoon Final Integrated Protect Implementation Report and Environmental Impact Statement 

(IRL-S Plan; SFWMD and U.S. Army Corps of Engineers, 2004). The Department’s preferred 

approach is to use the TP and TN targets from the (IRL-S Plan) as the end point for calculating 

the TMDLs for the various WBIDs. These targets (81 μg/L TP; 0.72 mg/L TN), applied at the 

Roosevelt Bridge, are supported by several additional lines of evidence, detailed below,

developed through subsequent evaluations by the Department and the SFWMD. The 

Department realizes that this is a very complex system and that the targets set by this TMDL 

can be revisited in the future. By revisiting this TMDL we will be able to re-evaluate the targets

based on new data as well as any water quality improvements from implemented projects. This 

iterative TMDL approach allows for a protective yet mutable document that can be updated as

knowledge and technology improve.

5.1.1 IRL-S Targets

The Indian River Lagoon Project Implementation Report (IRL-S Plan) was published by the 

SFWMD, U.S. Army Corps of Engineers, and partner agencies in 2004. Within the IRL-S Plan, 

water quality targets were identified for the Indian River Lagoon proper and its contributing 

areas, including the St. Lucie. The primary IRL-S targets (TN and TP) were set at levels 

considered protective of healthy seagrass beds in the Lagoon. These values were then 

propagated to the contributing areas, wherein waterbody-specific water quality targets were 

identified that were considered both protective of the waterbody itself and protective of 

downstream conditions in the Lagoon. Further detail on these calculations can be found in the 

IRL-S Plan (USACE/SFWMD, 2004).

The targets identified in the 2004 IRL-S plan for the St. Lucie Estuary (SLE) were calculated by 

the IRL-S Plan Water Quality Sub-team (See Appendix A of the IRL-S Plan). The TP value was 

calculated based on an adjusted mean of all Florida estuaries with some estuaries omitted due 

to geologically induced high phosphorus from substantial phosphate deposits (e.g. Tampa Bay). 

Modeling conducted during development of the IRL-S Plan indicated that a TP concentration of 

81 μg/L TP at Roosevelt Bridge would require that TP loads from the freshwater canals be 

decreased to 110 metric tons/year TP. This would result in a concentration of 53 μg/L TP in the 

Lagoon, the IRL-S Plan TP target for the Lagoon proper.

The TN target identified in the IRL-S Plan was based on a paper by Chamberlain and Hayward 

(1996). The TN target for the St. Lucie identified in the IRL-S Plan was expressed as a 30% 

reduction in TN. At the time the IRL-S Plan was written, the TN concentration for the estuary 

was 1.03 mg/L (DBHYDRO SFWMD 1999-2004), and a 30% reduction would yield a 

concentration of 0.721 mg/L TN. Similar to the link between St. Lucie and Lagoon TP targets, 

the 0.721 mg/L TN target in the St. Lucie was evaluated and found to be protective of water 

quality conditions in the Lagoon proper (TN target of 0.67 mg/L) because nitrogen 

concentrations decrease significantly between Roosevelt Bridge (monitoring station SE03; see 
21

Figure 1.3) and the Lagoon proper (monitoring station SE01; see Figure 1.3). Although the 

IRL-S work was conducted prior to 2004, this pattern in nutrient concentrations between 

Roosevelt Bridge and the Lagoon persists. Current median TN concentration at Roosevelt 

Bridge (SE03) is 1.063 mg/L while the Lagoon/Estuary Confluence (SE01) is 0.876 

mg/L. Current median TP concentrations at Roosevelt Bridge (164 μg/L) are double those at 

SE01 (84 μg/L). 

Through the work conducted for Plan development, the IRL-S Plan demonstrated that 81 μg/L 

TP and 0.72 mg/L TN targets in the SLE support water quality restoration in the Estuary and 

targets established for the broader Lagoon ecosystem. Thus, given the extensive scientific 

work and support afforded to these targets, the IRL-S TN and TP concentration targets, applied 

at Roosevelt Bridge, were used as targets in this TMDL.

5.1.2 Updated IRL-S Calculations and Links to Seagrass

Because the IRL-S Plan calculations were conducted in 2004, SFWMD and FDEP recalculated

the original IRL-S Lagoon targets to see if there was a significant difference with the inclusion of 

more recent data. Two methods were used to accomplish this task: 1) using the original IRL-S 

method (as described above); and 2) using polynomial equations to try to obtain a better fit to 

the data. The original IRL-S targets for the Lagoon were 53 μg/L TP and 0.67 mg/L TN. The 

recalculations completed by SFWMD using the same method as the IRL-S Plan resulted in

targets of 49 μg/L TP and 0.68 mg/L TN based on median values. Recalculations using the 

quadratic method resulted in targets of 51 μg/L TP and 0.66 mg/L TN. The result of both of 

these recalculation efforts are very similar to the Lagoon targets outlined in the original IRL-S 

Plan. These recalculation efforts support the validity of the original 2004 IRL-S Plan targets for 

use under current conditions.

5.1.3 Statewide Estuary Descriptive Statistics

Another approach used to evaluate the validity of the IRL-S targets was to calculate TN and TP 

concentrations for comparable non-impaired estuaries throughout Florida. DEP evaluated TN, 

TP, and chlorophyll-a data for all estuaries in the state from 2000 - 2007. Estuaries were 

removed that were known to be high in phosphates and dissimilar in locale and nutrient 

composition. Median values from the selected estuaries were compared to median values for 

the St. Lucie Estuary. This analysis showed a median TP value of 65 μg/L and median TN 

value of 0.86 mg/L for the selected estuaries. The 0.86 mg/L TN value, though slightly higher, is

comparable to that identified in the IRL-S Plan for the SLE (0.72 mg/L). The 65 μg/L TP value is 

slightly lower than that identified in the IRL-S Plan for the SLE (81 μg/L). However, the 

watershed that drains to the St. Lucie has unique characteristics due to it being a heavily 

modified, man-made estuary. Lake Okeechobee, via the C-44 Canal, is not a natural 

connection to the estuary and carries with it a large TP load. The other areas of the watershed 

that input to the estuary are extensive artificial drainage and irrigation systems unlike anything in 

relation to most other estuarine systems in Florida. These areas drain mostly agricultural lands 

which are connected to the estuary through a system of highly managed canals. These

differences could result in a higher phosphorus loading regime that does not affect the other 

selected estuaries. Even with these differences though, the comparability of the TN and TP 

concentrations support selection of the IRL-S Plan SLE targets for the TMDL.
22

5.1.4 Comparison of Targets

Table 5.1 Target Method Summary

Method

St. Lucie Estuary 

Targets

Indian River Lagoon 

Targets Period of 

Record

Method of 

Analysis

TN (mg/L) TP (μg/L) TN (mg/L) TP (μg/L)

SLE Targets from 

2004 IRL-S Plan 0.72 81 N/A N/A 1999 - 2004 Median

SFWMD IRL 

PLRG N/A N/A 0.67 53 1990 - 1999 Median

Seagrass 

Comparison N/A N/A 0.66 55 1995 - 2005 Median

Seagrass 

Polynomial N/A N/A 0.66 51 1995 - 2005 Regression

Statewide 

Comparison 0.86 65 N/C N/C 2000 - 2007 Median

N/A: Sufficient data was not available to recalculate these values

N/C: Values not calculated

As shown in Table 5.1, three different lines of calculation support the selection of the 2004 IRLS TN and TP concentrations of 0.72 mg/L and 81 μg/L as the TMDL targets for the St. Lucie 

Watershed. This weight-of-evidence approach to establishing nutrient targets for the TMDL 

supports the use of the original IRL-S targets for the St. Lucie Estuary. Additionally, these 

values are consistent with the best professional judgment of local scientists and stakeholders 

based on their knowledge of the estuary. 

With respect to DO, these targets support what is necessary to control pollutants in such a 

manner that restores an appropriate balance of flora in the estuary. It is possible that DO is also 

influenced by factors other than the nutrients and BOD in the system, such as hydrology or 

existing sediment quality. However, any further depression in DO in the estuary would not be 

caused by pollutant discharges and thus, not taken into account in this TMDL. 

5.2 Data Used in the Determination of the TMDL

Keeping true to the Verified Period for the St. Lucie River basin water quality assessment which 

started in 1996, no data earlier than 1996 were used to determine verification. WBID 3211 

(Bessey Creek), a recently monitored waterbody, has only a five-year period of data (2001 –

2005). All other WBIDs utilize the ten-year period of record (1996 – 2005). Appendix C

contains the total number of samples and annual TP and TN concentrations utilized for each 

WBID and Appendix D contains the BOD data.
23

5.3 TMDL Development Process

Ideally, flows and loads impacting a waterbody should be simulated using a model that 

accurately simulates hydrologic and water quality conditions. Though not a fully complete, 

calibrated and validated model, the Department has decided to use the WaSh model, in part, as 

the basis for this TMDL. Due to the insensitivity of the model’s response to nutrient levels, the 

model was not used to estimate nutrient concentration levels. Rather, the hydrology of the 

basin, which the model predicts well as agreed upon by the technical working group, was used 

to calculate contributing flows to the Estuary.

The WaSh model is a distributed process-based, coupled hydrologic, hydrodynamic and water 

quality model originally developed for the unique hydrologic conditions in south Florida. 

Additionally, the WaSh model was already configured and applied to basins draining to the SLE 

for previous studies conducted by the South Florida Water Management District. Since its initial 

development, there have been substantial improvements made to the model, some of which 

include changes to the phytoplankton – nutrient cycling interaction, the inclusion of atmospheric 

deposition, and a more detailed look at Aerial Based Mean Concentrations (similar to Event 

Mean Concentrations) specific to the St. Lucie basin. There are a few shortcomings to the 

model still, two being the lack of SOD and BOD data to calibrate against. Work is being done to 

overcome these limitations though and that, along with the updates made to the model will 

make it better able to simulate realistic conditions. When completed, the WaSh model will aid 

the BMAP process by providing some foresight into the consequences of potential 

implementation projects.

The model’s hydrologic response has been configured and successfully calibrated and validated 

for all of the basins influencing the SLE. The flow calibration consisted of comparisons of daily 

flow measurements over a six-year period (1995 – 2000) and comparisons to monthly salinity 

data for a three-year period (2003 – 2005). For more detailed information on flow calibration 

and validation see WaSh Model Documentation Report (URS, 2008).

One of the unique qualities of the St. Lucie Estuary is the combination of ocean, rivers, canals 

and gated structures that control most surface basin flows to the estuary. Other than the natural 

tidal influence of the Atlantic Ocean, the North Fork of the St. Lucie River, and several small 

creeks, most surface flow to the estuary is controlled by structures that can modify the flow from 

low to high and even stop the flow completely, turning the canals into reservoirs.

The St. Lucie is a highly modified system and many of the WBIDs in the watershed have some 

sort of structure controlling the flow. Waterbodies 3193, 3194B, 3210, meet at the Roosevelt 

Bridge and create a confluence with a salinity gradient which decreases as one traverses from 

3193 to the North (3194B) or South (3210) Forks of the estuary. A percent reduction was 

applied to WBID 3193 based on its current mean nutrient concentrations. The nutrient target 

applied to WBID 3193 was applied to all WBIDS which contribute to the estuary and are listed in 

Tables 5.2 and 5.3. Figures 5.9 and 5.10 present bar graphs of the current loads and required 

reductions. 
24

5.3.1 Modeled Flows 

Using the WaSh model, flows were estimated for waterbodies in the system. Figures 5.1 and 

5.2 illustrate the fraction of modeled average annual flows from the contributing source areas. It 

is important to note that while Lake Okeechobee contributes a significant flow to the estuary, a 

TMDL has been established for the Lake, so its nutrient contributions are not considered in this 

TMDL except as noted in Chapter 6. WBID Flow data was obtained from the WaSh model in 

two ways: 

1) for those WBIDs with structures at their endpoints, modeled flow data was used from that 

point and assumed representative of the entire WBID, 

2) for those WBIDs without major control structures, the WaSh model has the capability to 

estimate daily flow values at selected nodes in the routing network. Nodes from each 

waterbody were selected at or near the intersection of the upstream and downstream boundary 

of the WBID. Subtracting annual upstream flow from annual downstream flow results in a net 

annual flow for those waterbodies. 
25

Figure 5.1 Modeled Flows to Estuary with Lake Okeechobee

C-24 Canal (3197)

C-23 Canal (3200)

C-44 Canal (3218)

Lake Okeechobee

South Fork St. Lucie 

Bessey Creek (3211) River (3210A)

South Fork St. Lucie 

Estuary (3210)

North Fork St. Lucie 

Estuary (3194B)

North Fork St. Lucie 

River (3194)

Figure 5.2 Modeled Flows to Estuary without Lake Okeechobee

North Fork St. Lucie 

Estuary (3194B)

C-24 Canal (3197)

C-23 Canal (3200)

North Fork St. Lucie 

River (3194)

C-44 Canal (3218)

Bessey Creek (3211)

South Fork St. Lucie 

Estuary (3210)

South Fork St. Lucie 

River (3210A)
26

5.3.2 Measured Nutrient Concentration Data

IWR data from sampling stations within each WBID were used to calculate individual waterbody 

concentrations based on 10-year measured mean annual nutrient concentrations, as displayed 

in Tables 5.2 and 5.3. Figures 5.3 and 5.4 illustrate the relative concentrations from each 

WBID.

Appendix E provides maps of sampling stations and a summary of the descriptive statistics of 

the nutrient levels associated with each waterbody. An outlier analysis was conducted on the 

data set from each waterbody to determine if measured values were not representative of the 

population. The results of the outlier analyses are in Appendix F. The only waterbody that had 

data censored was C23 Canal, WBID 3200. According to the data and additional investigation, 

the sample site station 21FLWPB28010391 / Site 89 located in a drainage canal at Melear Dairy 

Farm has been identified as a high nutrient source, which will be addressed during the BMAP 

process. The data from this station was censored for the nutrient analysis since it is sitespecific and not representative of the C-23 basin. 
27

Figure 5.3 Annual Average Total Nitrogen (mg/L) for each WBID

0.916

0.96

1.01

1.492

1.489

1.168

1.359

0.945

1.473

St. Lucie Estuary (3193)

North Fork St. Lucie River (3194)

North Fork St. Lucie Estuary (3194B)

C-24 Canal (3197)

C-23 Canal (3200)

South Fork St. Lucie Estuary (3210)

South Fork St. Lucie River (3210A)

Bessey Creek (3211)

C-44 Canal (3218)

Figure 5.4 Annual Average Total Phosphorus (mg/L) for each WBID

0.138

0.14

0.193

0.291

0.379

0.189

0.212

0.166

0.18

St. Lucie Estuary (3193)

North Fork St. Lucie River (3194)

North Fork St. Lucie Estuary (3194B)

C-24 Canal (3197)

C-23 Canal (3200)

South Fork St. Lucie Estuary (3210)

South Fork St. Lucie River (3210A)

Bessey Creek (3211)

C-44 Canal (3218)
28

5.3.3 Flow Duration Curves

The TMDL is expressed as a percent reduction in concentration to meet the TMDL

concentration target. This approach is supported by examination of flow and load duration 

curves for the various waterbodies. The majority of flow, and thus loads to the estuary is 

provided by a system of canals with control structures. For example, Figure 5.5 and 5.6

present flow duration curves for WBIDs 3200 (C-23) and WBID 3194 (North Fork St. Lucie 

River). The flow duration curve includes daily flows from the 10-year period of record. The flow 

duration curves use hydrologic data from the WaSh model to examine the cumulative frequency 

of historic flow data over the period of record. The daily flow rates are sorted from the highest 

value to lowest. A duration curve relates flow values to the percent of time those values have 

been met or exceeded. The use of “percent of time” on the x axis provides a uniform scale 

ranging between 0 and 100. The full range of flows is considered. Low flows (on the right) are 

exceeded a majority of the time, whereas floods (on the left) are exceeded infrequently. 

Duration curve analysis thus identifies intervals, which can be used as a general indicator of 

hydrologic condition (i.e., wet, dry, seasonal, and to what degree). Generally, dry seasons are 

represented by low flow conditions, and wet seasons are captured by high flow conditions. 

Figure 5.5, WBID 3200 (C-23) represents a water body with a control structure. Figure 5.6, 

WBID 3194 (North Fork St. Lucie River) demonstrates a flow duration curve for a water body 

with no major control structures.

For WBID 3200, it is interesting to note that there is a significant increase in flows at 60% of 

days exceeded, and a series of “steps” of constant flow from 20% to 55% of days exceeded 

from this basin. This is reflective of the operation of the control structures along with associated 

weather patterns. Other WBIDS with control structures exhibit flow characteristics reflective of 

gate operation and weather patterns.

For WBID 3194, there are no major control structures and the flow duration curve exhibits the 

typical sigmoidal pattern for natural systems. A similar flow duration curve pattern is repeated 

for WBIDs without major control structures.
29

Figure 5.5 WBID 3200 Flow Duration Curve 1996-2005

0.01

0.1

1

10

100

1000

10000

0 10 20 30 40 50 60 70 80 90 100

Percent of Days Exceeded

CFS

Figure 5.6 WBID 3194 Flow Duration Curve 1996-2005

1

10

100

1000

10000

0 10 20 30 40 50 60 70 80 90 100

Percent of Days Exceeded

CFS
30

5.3.4 Load Duration Curves

After flow durations are considered, the next step is to consider the daily load in relation to the 

target concentration. This is accomplished through the use of a load duration curve. As an 

example, Figure 5.7 presents the total phosphorus load duration curves for WBID 3200 (Canal 

23).

The load duration curve allows one to compare the target load with the measured load using the 

estimated flows from the WaSh model for all flow conditions. High loads are on the left side of 

the figure and low loads are on the right side of the figure. The target load is the series of blue 

points, and the measured loads are the red points. 

WBID 3200 requires a 78.6 percent annual total phosphorus concentration reduction to meet 

the target daily load given the flows and concentrations for the period of record. The pattern of 

exceedances for all flow conditions (wet, dry, annual) is repeated for all of the WBIDS and their 

respective nutrient loads. However, due to variability in flow and load characteristics, the 

reductions for each WBID are not uniform.

Figure 5.8 exhibits the total nitrogen load duration curve for WBID 3194 which has no major 

control structure. It is interesting that WBID 3194 currently meets the target load for several 

days throughout the period of record, and this is reflected in the lower percent reduction for total 

nitrogen of 25 percent for WBID 3194. WBID 3194 exceeds the target load throughout the 

period of record over all flow regimes. The exceedances across all flow regimes require a 

longer-term approach to estimating the percent reductions due to the inherent variability of flow 

and load estimates. Note that annual average concentration target and the total maximum 

“daily load” work together. An annual averaging period provides a way to achieve long-term 

program objectives by averaging short term problems such as high flow storm events. 
31

Figure 5.7 WBID 3200 TP Load Duration Curve 1996-2005

0.01

0.1

1

10

100

1000

10000

100000

0 10 20 30 40 50 60 70 80 90 10

0

Percent of days exceeded

TP (lbs)

TP Load (lbs)

TP Target (lbs)

Figure 5.8 WBID 3194 TN Load Duration Curve 1996-2005

1.0

10.0

100.0

1000.0

10000.0

100000.0

0 20 40 60 80 100

Percent of Days Exceeded

TN Load (lbs)

TN Load (lbs)

TN Target (lbs)
32

5.3.5 Annual Existing and Allowable Loads

After examining the load duration curves for the contributing WBIDS, the general procedure for 

calculating estimated nutrient loads and reductions was conducted as follows. The load is 

generated by multiplying concentration times flow and a conversion factor:

=×× LfQC

Where C is the IWR Mean Annual concentration, Q is the modeled annual flow for the 

contributing source area, and f is a conversion factor for units. The average value of the 10-

year mean annual load is then calculated. WBID 3211 has a 5-year mean annual load since 

instrumentation of the site has occurred only recently. All other WBIDS have a 10-year period 

of record for TN and TP. An example TN calculation for WBID 3218 for 1996 is:

pounds

mg

pounds

gallon

Liter

acre ft

gallons

acre ft L

mg 147,503 37.592,453

851,325 78.3 530,1423.1 × × = − × ×−

To calculate the target load, the same process is used with a substitution of the target 

concentration value, Ctarget , for the measured IWR mean annual concentration to yield a target 

load, Ltarget: 

t arg et =×× LfQC t arg et

The annual load reduction in pounds can then be calculated by subtracting the current load from 

the target load. Percent reduction is the fraction that must be reduced from the current mean 

annual load. The annual flows estimated by the WaSh Model and nutrient loads for each 

impaired waterbody are summarized in Table 5.2 for total nitrogen and Table 5.3 for total 

phosphorus. Annual flow values were multiplied by target concentrations to obtain a target 

annual load from each waterbody. Mean values were calculated for each WBID resulting in a 

ten-year mean annual concentration for each waterbody. Figures 5.5 and 5.6 illustrate the 

relative current loads and reductions of nutrients in pounds to achieve the target concentrations. 

It is anticipated that when the nutrient targets are achieved, flora in the system will be in balance 

in the Estuary.
33

Table 5.2 WaSh Estimated Flows with Annual Existing and 

Allowable TN Loads

Waterbody

Modeled 

Flow

(acre-ft/yr)

Annual 

Average

TN

[mg/L]

Annual 

Average 

TN Load 

(lbs)

Target 

Annual TN 

Load (lbs) 

or TN

[mg/L]

Annual Load 

Reduction 

(lbs) or TN

[mg/L]

Percent 

Reduction

Average 

Daily 

Load

(lbs)

TMDL

(lbs)

St. Lucie 

Estuary

(3193) N/A 0.916 N/A [0.720] [0.196] 21.4 N/A N/A

North Fork St. 

Lucie River

(3194) 71,600 0.960 186,962 140,134 46,828 25.0 512 384

North Fork St. 

Lucie Estuary

(3194B) 53,009 1.010 145,625 103,747 41,878 28.8 399 284

C-24 Canal

(3197) 178,296 1.492 723,569 348,957 374,612 51.8 1,982 956

C-23 Canal

(3200) 123,751 1.489 501,201 242,202 258,999 51.7 1,373 664

South Fork St. 

Lucie Estuary

(3210) 12,499 1.168 39,710 24,463 15,246 38.4 109 67

South Fork St. 

Lucie River

(3210A) 46,225 1.359 170,870 90,471 80,400 47.1 468 248

Bessey Creek

(3211) 15,318 0.945 39,374 29,981 9,394 23.9 108 82

C-44 Canal

(3218) 124,122 1.473 497,303 242,929 254,374 51.2 1,362 666

Period of Record: 1996 - 2005

N/A – Not Applicable
34

Table 5.3 WaSh Estimated Flows with Annual Existing and 

Allowable TP Loads

Waterbody

Modeled 

Flow

(acre-ft/yr)

Annual 

Average 

TP

[mg/L]

Annual 

Average 

Load 

(lbs)

Target 

Annual TP 

Load (lbs) 

or TP

[mg/L]

Annual 

Load 

Reduction 

(lbs) or TP

[mg/L]

Percent 

Reduction

Average 

Daily 

Load

(lbs)

TMDL

(lbs)

St. Lucie 

Estuary

(3193) N/A 0.138 N/A [0.081] [0.057] 41.3 N/A N/A

North Fork St. 

Lucie River

(3194) 71,600 0.140 27,265 15,765 11,500 42.2 75 43

North Fork St. 

Lucie Estuary

(3194B) 53,009 0.193 27,827 11,672 16,156 58.1 76 32

C-24 Canal

(3197) 178,296 0.291 141,125 39,258 101,867 72.2 387 108

C-23 Canal

(3200) 123,751 0.379 127,572 27,248 100,325 78.6 350 75

South Fork St. 

Lucie Estuary

(3210) 12,499 0.189 6,426 2,752 3,673 57.2 18 8

South Fork St. 

Lucie River

(3210A) 46,225 0.212 26,655 10,178 16,477 61.8 73 28

Bessey Creek

(3211) 15,318 0.166 6,917 3,373 3,544 51.2 19 9

C-44 Canal

(3218) 124,122 0.180 60,770 27,330 33,441 55.0 166 75

Period of Record: 1996 - 2005

N/A – Not Applicable

Table 5.4 Annual Existing and Allowable BOD Concentrations

Waterbody

Modeled 

Flow

(acre-ft/yr)

Annual 

Average 

[BOD]

mg/L

Target 

Annual 

[BOD]

mg/L

Annual 

Reduction 

[BOD]

mg/L

Percent 

Reduction

North Fork St. 

Lucie River

(3194) 71,600 [7.70] [2.00] [5.70] 74.0

C-24 Canal

(3197) 178,296 [3.00] [2.00] [1.00] 33.3

C-44 Canal

(3218) 124,122 [6.60] [2.00] [4.60] 69.7

Period of Record: 1996 - 2005
35

Figure 5.9 Current and Target Average Annual Total Nitrogen Loads

186,962

145,625

723,569

501,201

39,710

170,870

39,374

497,303

140,134

103,747

348,957

242,202

24,463 90,471 29,981

242,929

0

100,000

200,000

300,000

400,000

500,000

600,000

700,000

800,000

North Fork

St. Lucie

River (3194)

North Fork

St. Lucie

Estuary

(3194B)

C-24 Canal

(3197)

C-23 Canal

(3200)

South Fork

St. Lucie

Estuary

(3210)

South Fork

St. Lucie

River

(3210A)

Bessey

Creek

(3211)

C-44 Canal

(3218)

Waterbody

TN Load (lbs)

Current Annual Average Load Target Annual Load

Figure 5.10 Current and Target Average Annual Total Phosphorus 

Loads

27,265 27,827

141,125

127,572

6,426

26,655

6,917

60,770

15,765 11,672

39,258

27,248

2,752

10,178

3,373

27,330

0

20,000

40,000

60,000

80,000

100,000

120,000

140,000

160,000

North Fork

St. Lucie

River (3194)

North Fork

St. Lucie

Estuary

(3194B)

C-24 Canal

(3197)

C-23 Canal

(3200)

South Fork

St. Lucie

Estuary

(3210)

South Fork

St. Lucie

River

(3210A)

Bessey

Creek

(3211)

C-44 Canal

(3218)

Waterbody

TP Load (lbs)

Current Annual Average Load Target Annual Load
36

Chapter 6: DETERMINATION OF THE TMDL

6.1 Expression and Allocation of the TMDL 

The objective of a TMDL is to provide a basis for allocating acceptable loads among all of the 

known pollutant sources in a watershed so that appropriate control measures can be 

implemented and water quality standards achieved. The goal of the TMDL development for the 

St. Lucie Basin (WBIDs 3193, 3194, 3194B, 3197, 3200, 3210, 3210A, 3211, and 3218) is to 

identify the maximum allowable TN, TP, and BOD loadings to the watershed so that it will meet 

applicable water quality standards and maintain its function and designated use as Class III 

water. 

A TMDL is typically expressed as the sum of all point source loads (Wasteload Allocations, or 

WLAs), nonpoint source loads (Load Allocations, or LAs), and an appropriate margin of safety 

(MOS) that takes into account any uncertainty concerning the relationship between effluent 

limitations and water quality:

TMDL = ∑ WLAs + ∑ LAs + MOS

Due to the complex nature of the St. Lucie system, large tidal exchange, constant mixing 

between the North and South forks, etc., flow values for the WBIDs 3193, 3194B, and 3210 

were difficult to determine. As such, load reductions will be calculated for those waterbodies 

that input to the estuary based on concentration reductions applied to the three waterbodies 

mentioned above that are directly connected to the compliance point of the system, the 

Roosevelt Bridge.

As discussed earlier, the WLA is broken out into separate subcategories for wastewater 

discharges and stormwater discharges regulated under the NPDES Program:

TMDL ≅ ∑ WLAswastewater + ∑ WLAsNPDES Stormwater + ∑ LAs + MOS

It should be noted that the various components of the revised TMDL equation may not sum up 

to the value of the TMDL because (a) the WLA for NPDES stormwater is typically based on the 

percent reduction needed for nonpoint sources and is also accounted for within the LA, and (b) 

TMDL components can be expressed in different terms (for example, the WLA for stormwater is 

typically expressed as a percent reduction, and the WLA for wastewater is typically expressed 

as mass per day).

WLAs for stormwater discharges are typically expressed as “percent reduction” because it is 

very difficult to quantify the loads from MS4s (given the numerous discharge points) and to 

distinguish loads from MS4s from other nonpoint sources (given the nature of stormwater 

transport). The permitting of stormwater discharges also differs from the permitting of most 

wastewater point sources. Because stormwater discharges cannot be centrally collected, 

monitored, and treated, they are not subject to the same types of effluent limitations as 

wastewater facilities and instead, are required to meet a performance standard of providing 

treatment to the “maximum extent practical” through the implementation of best management 

practices (BMPs).

This approach is consistent with federal regulation 40 CFR § 130.2[I] (EPA, 2003), which states 

that TMDLs can be expressed in terms of mass per time (e.g., pounds per day), toxicity, or other 
37

appropriate measure, such as mass per volume. The TMDL for the St. Lucie Estuary is 

expressed in terms of percent reduction, and represents the reductions in TN, TP, and BOD the 

estuary systems needs to maintain its designated uses (Table 6.1).

Table 6.1 TMDL Components for the St. Lucie Basin 

Waterbody Parameter

Annual 

TMDL Target

lbs or [C]

WLA

LA 

(% Reduction) NPDES MOS

Wastewater 

(mg/L)

NPDES 

Stormwater 

(% Reduction)

St. Lucie 

Estuary

(3193)

TN [0.720] N/A 21.4 21.4 Implicit

TP [0.081] N/A 41.3 41.3 Implicit

North Fork St. 

Lucie River

(3194)

TN 140,134 N/A 25.0 25.0 Implicit

TP 15,765 N/A 42.2 42.2 Implicit

BOD [2.0] N/A 74.0 74.0 Implicit

North Fork St. 

Lucie Estuary

(3194B)

TN 103,747 N/A 28.8 28.8 Implicit

TP 11,672 N/A 58.1 58.1 Implicit

C-24 Canal

(3197)

TN 348,957 N/A 51.8 51.8 Implicit

TP 39,258 N/A 72.2 72.2 Implicit

BOD [2.0] N/A 33.3 33.3 Implicit

C-23 Canal

(3200)

TN 242,202 N/A 51.7 51.7 Implicit

TP 27,248 N/A 78.6 78.6 Implicit

South Fork St. 

Lucie Estuary

(3210)

TN 24,463 N/A 38.4 38.4 Implicit

TP 2,752 N/A 57.2 57.2 Implicit

South Fork St. 

Lucie River

(3210A)

TN 90,471 N/A 47.1 47.1 Implicit

TP 10,178 N/A 61.8 61.8 Implicit

Bessey Creek

(3211)

TN 29,981 N/A 23.9 23.9 Implicit

TP 3,373 N/A 51.2 51.2 Implicit

C-44 Canal 

(3218)

TN 242,929 N/A 51.2 51.2 Implicit

TP 27,330 N/A 55.0 55.0 Implicit

BOD [2.0] N/A 69.7 69.7 Implicit

 N/A – Not Applicable, [ ] – concentration in mg/L

6.2 Load Allocation

The load allocation is a percentage of the estimated mean annual load that will result in 

attainment of target concentration values. Reductions for this TMDL are based strictly on a 

percent reduction of load allocations (see Tables 5.2 and 5.3 for actual values). Reductions will 

be applied to each waterbody that inputs to the Estuary. Though there is a specific point at 

which each waterbody joins the Estuary, they are considered nonpoint sources and thus, fall in 

the load allocation section. Specific allocations will be applied during the BMAP process for all 

contributors to each individual waterbody (e.g. MS4s). For BOD, which is dependent on 

reduction of algal blooms and other biological processes, the load allocation is a percentage of 

the mean annual load that will result in attainment of BOD criteria discussed in section 3.2.2

(see Table 5.4 for actual values).
38

6.3 Wasteload Allocation

6.3.1 NPDES Wastewater Discharges

There are 15 permitted NPDES wastewater facilities (Table 4.1) in the St. Lucie basin which are 

permitted to discharge only during a 25-year/72-hour storm event amounting to minimal and 

highly irregular impact on nutrient discharges. Facilities that have permitted discharges above 

this level are for cooling or dewatering, which are effectively discharging ambient water. Since 

this report is based on ambient conditions in the watershed, the infrequent discharge from the 

above mentioned facilities is not included in the overall reduction. If conditions change in the 

permits for any of the facilities mentioned, that change will be included as part of the restoration 

effort. 

6.3.2 NPDES Stormwater Discharges

Chapter 4 listed six Municipal Separate Storm Sewer Systems (MS4s) which may discharge 

nutrients to water bodies in response to storm events. Although boundaries and locations of 

MS4s are exhibited in Chapter 4, little information was available to the Department at the time 

this analysis was conducted regarding the descriptive nature or character (flows and loads) of 

the NPDES stormwater discharges that would distinguish them from other land uses within the 

basins. The stormwater TN and TP loadings from MS4 areas were estimated by their inclusion 

in the comprehensive stormwater modeling of the basin (see WaSh Model Documentation, 

URS, 2008 for detailed information).

6.4 Margin of Safety

TMDLs must address uncertainty issues by incorporating a margin of safety into the analysis. 

The MOS is a required component of a TMDL and accounts for the uncertainty about the 

relationship between pollutant loads and the quality of the receiving waterbody (Clean Water 

Act, Section 303[d][1][c]). Considerable uncertainty is usually inherent in estimating nutrient 

loading from nonpoint sources, as well as in predicting water quality response. The 

effectiveness of management activities (e.g., stormwater management plans) in reducing 

loading is also subject to uncertainty. For the St. Lucie Basin an implicit MOS was employed

and the following are two of the critical assumptions that went into the design of this report:

1) Average Annual Flows–

Average annual flows for the10-year period results in a lower TMDL versus a seasonal 

averaging period and is supported by the flow and concentration data that is available. The 

estimation using a lower flow value is in accord with the Department’s policy to use 

conservative values for TMDL development. 

2) Lake Okeechobee meeting its TMDL target –

It is Department policy that a waterbody with a TMDL in place shall be assumed to be 

meeting its established target. Lake Okeechobee is an indirect contributor to the Estuary 

via the C-44 Canal and, as such, all waters being released from the Lake are assumed to 

be at 40 ppb TP, the target established in the Lake’s TMDL. This assumption allows for 

the partitioning of impairment between the Lake water and the C-44 watershed and does 

not put the burden of resolving the Lake’s impairment issues on the contributors to the C44 and southern estuary watersheds.
39

Chapter 7: NEXT STEPS: IMPLEMENTATION PLAN 

DEVELOPMENT AND BEYOND

7.1 Basin Management Action Plan

This TMDL will be implemented primarily through a Basin Management Action Plan (BMAP). 

Section 373.4595 F.S. requires that the BMAP be initiated no later than 90 days after adoption 

of this TMDL, and that the BMAP be completed as soon as practicable. In the St. Lucie 

Watershed, the BMAP process will be closely coordinated with the NEEPP River Watershed 

Protection Plan. As discussed in Chapter 1, the St. Lucie NEEPP River Watershed Protection 

Plan is being developed primarily by the SFWMD, with participation from DEP, DACS, and a 

variety of interested stakeholders. The St. Lucie NEEPP River Watershed Protection Plan is 

due to the Florida Legislature on January 1, 2009. 

Section 373.4595 F.S. calls for expeditious implementation of the River Watershed Protection 

Plan and states that implementation of the Watershed Plan and any related BMAPs is a 

reasonable means of achieving TMDLs and compliance with state water quality standards. The 

SFWMD, FDACS, and FDEP are working closely together to coordinate the NEEPP and BMAP 

processes, avoid overlap, and ensure that implementation efforts are timely and cost-effective. 

Prior to initiation of the BMAP, the DEP will closely review the River Watershed Protection Plan 

and identify components of the Watershed Plan that are directly applicable to the BMAP. Basic 

BMAP guidelines are outlined in 403.067(7) F.S., including:

• Appropriate load reduction allocations among the affected parties, or to the basin as a whole 

(403.067(7)(a)2.);

• A description of the appropriate management strategies to be undertaken, including regional 

treatment systems or other public works, where appropriate;

• An implementation schedule;

• A basis for evaluating the plan’s effectiveness;

• Feasible funding strategies;

• Linkages to affected NPDES permits;

• Mechanisms by which potential future increases in pollutant loading will be addressed;

• A water quality monitoring component sufficient to evaluate progress in pollutant load 

reductions; and

• An assessment process to occur no less than every five years.

The BMAP will likely include other factors beyond these basic elements. The BMAP 

development process will occur with the close cooperation of local stakeholders and DEP’s 

partner NEEPP agencies (SFWMD and FDACS), many of whom were involved in development 

of this TMDL. 
40

References 

Broward County. August 2003. Broward-by-the-numbers. Broward County, Office of Urban 

Planning and Redevelopment, Planning Services Division. No. 2. Available: 

http://www.broward.org/planningservices/bbtn2.pdf.

Brown, M. T. 1995. South Dade Watershed Project. University of Miami, SFWMD Chemical 

and Trophic State Characteristics of Lakes in Relation to Regional Geology. Final Report 

Submitted to Coop. Fish and Wildlife Research Unit, University of Florida. 444 pp.

Chamberlain, Robert and Hayward, Donald, 1996. Evaluation of Water Quality and Monitoring 

in the St. Lucie Estuary, Florida. Water Resources Bulletin 32 (4): 681 – 696.

CDM, 1998. User’s Manual: Watershed Management Model, Version 4.1. Camp Dresser, and 

McKee, Rouge River National Wet Weather Demonstration Project. Wayne County, Michigan. 

PRO-NPS-TM27.02 

Florida Department of Environmental Protection. Florida Watershed Restoration Act. 1999. 

Chapter 99-223, Laws of Florida.

_____________. February 2001. A report to the Governor and the Legislature on the allocation 

of total maximum daily loads in Florida. Tallahassee, Florida: Allocation Technical Advisory 

Committee, Division of Water Resource Management, Bureau of Watershed Management.

_____________. April 2001a. Rule 62-303, F.A.C., Identification of Impaired Surface Waters 

Rule (IWR). Tallahassee, Florida: Division of Water Resource Management, Bureau of 

Watershed Management.

_____________. April 2001b. Rule 62-302, F.A.C., Surface Water Quality standards. 

Tallahassee, Florida: Division of Water Resource Management, Bureau of Watershed 

Management.

_____________. May 2001b. Rule 62-304.700, F.A.C., Total Maximum Daily Loads. 

Tallahassee, Florida: Division of Water Resource Management, Bureau of Watershed 

Management. Available: https://www.flrules.org/gateway/RuleNo.asp?ID=62-304.700

_____________. 2003. Basin Status Report: St. Lucie and Loxahatchee. Watershed Planning 

and Coordination Section. Bureau of Watershed Management.

_____________. June 2008. Tallahassee, Florida: Division of Water Resource Management, 

Bureau of Information Systems, Geographic Information Systems Section. Available: 

http://www.dep.state.fl.us/gis/contact.htm.

Francis-Floyd, Ruth. 2003. Dissolved Oxygen for Fish Production. Fact Sheet FA 27, one of a 

series of the Department of Fisheries and Aquaculture, Florida Cooperative Extension Service, 

Institute of Food and Agricultural Sciences, University of Florida.
41

Gunsalus, Boyd E. and Goldstein, Alan L., 2008. St. Lucie Estuary and Southern Indian River 

Lagoon: Watershed Water Quality Summary, SFWMD, Stuart

Graves, G., M. Thompson, D. Strom, and D. Fike, June 2002. St. Lucie Estuary: Evidence of 

Impairment (In Draft), FDEP Southeast District Water Quality Section, Port St. Lucie.

Harper, H. & D. Baker. 2007. Evaluation of Current Stormwater Design Criteria in Florida. 

Prepared by Environmental Research and Design for the Florida Department of Environmental 

Protection. Available: 

National Oceanic Atmospheric Adminstration (NOAA). National Weather Service Forecast 

Office - Weather Records. Available at 

http://www.dep.state.fl.us/water/nonpoint/docs/nonpoint/SW_TreatmentReportFinal_71907.pdf

Harper, H. H. and Baker, D. M., 2003. Evaluation of Alternative Stormwater Regulations for 

Southwest Florida, Final Report. Environmental Research and Design, Inc., Orlando, Florida, 

September, 2003.

Harper, H. H. and E. H. Livingston. 1999. Everything You Always Wanted to Know About 

Stormwater Management but Were Afraid to Ask. Biennial Stormwater Research Conference, 

Tampa, FL.

Kils, U., U. Waller, and P. Fischer. 1989. The Fish Kill of the Autumn 1988 in Kiel Bay. 

International Council for the Exploration of the sea C M 1989/L:14 

Macpherson, Tara A. and et al, 2007. Water Column Oxygen Demand and Sediment Oxygen 

Flux: Patterns of Oxygen Depletion in Tidal Creeks. Hydrobiologia, 586: 235 – 248. 

http://www.weather.gov/climate/

Price, Cynthia B., Carl Cerco, and Douglas Gunnison. 1994. Sediment Oxygen Demand and 

Its Effects on Dissolved Oxygen Concentrations and Nutrient Release; Initial Laboratory 

Studies. U. S. Army Corps of Engineers. Water Quality Research Program. Technical Report 

W-94-1.

Sime, P. 2005. St. Lucie Estuary and Indian River Lagoon conceptual ecological model. 

Wetlands 25 (4): 898 – 907.

South Florida Water Management District (SFWMD). DBHydro database. Available at 

http://my.sfwmd.gov/dbhydroplsql/show_dbkey_info.main_menu

South Florida Water Management District (SFWMD), 2003. CERP Monitoring and Assessment 

Plan. Appendix A: Conceptual Ecological Models

URS 2008, WaSh Model Documentation Report, Prepared for South Florida Water 

management District, March 17, 2006

U.S. Census Bureau Website. 2008. Available: http://www.census.gov/.

U.S. Environmental Protection Agency. April 1991. Guidance for water quality–based 

decisions: The TMDL process. EPA-440/4-91-001. Washington, D.C.: Office of Water.
42

_____________. 2007. Sediment Oxygen Demand Studies. Office of Environmental 

Measurement and Evaluation. Last updated on Monday, May 14th, 2007. http://www.epa.gov/
43

Appendix A

Background Information on Federal and State Stormwater Programs

In 1982, Florida became the first state in the country to implement statewide regulations to 

address the issue of nonpoint source pollution by requiring new development and 

redevelopment to treat stormwater before it is discharged. The Stormwater Rule, as authorized 

in Chapter 403, F.S., was established as a technology-based program that relies on the 

implementation of BMPs that are designed to achieve a specific level of treatment (e.g., 

performance standards) as set forth in Rule 62-40, F.A.C.

The rule requires the state’s water management districts to establish stormwater pollutant load 

reduction goals (PLRGs) and adopt them as part of a Surface Water Improvement and 

Management (SWIM) plan, other watershed plan, or rule. Stormwater PLRGs are a major 

component of the load allocation part of a TMDL. To date, stormwater PLRGs have been 

established for Tampa Bay, Lake Thonotosassa, the Winter Haven Chain of Lakes, the 

Everglades, Lake Okeechobee, and Lake Apopka. No PLRG had been developed for Newnans 

Lake at the time this report was developed. 

In 1987, the U.S. Congress established Section 402(p) as part of the federal Clean Water Act 

Reauthorization. This section of the law amended the scope of the federal NPDES stormwater 

permitting program to designate certain stormwater discharges as “point sources” of pollution. 

These stormwater discharges include certain discharges that are associated with industrial 

activities designated by specific standard industrial classification (SIC) codes, construction sites 

disturbing 5 or more acres of land, and master drainage systems of local governments with a 

population above 100,000, which are better known as MS4s. However, because the master 

drainage systems of most local governments in Florida are interconnected, the EPA has 

implemented Phase 1 of the MS4 permitting program on a countywide basis, which brings in all 

cities (incorporated areas), Chapter 298 urban water control districts, and FDOT throughout the 

15 counties meeting the population criteria. 

An important difference between the federal and state stormwater permitting programs is that 

the federal program covers both new and existing discharges, while the state program focuses 

on new discharges. Additionally, Phase II of the NPDES Program expands the need for these 

permits to construction sites between 1 and 5 acres, and to local governments with as few as 

10,000 people. The revised rules required that these additional activities obtain permits by 

2003. While these urban stormwater discharges are now technically referred to as “point 

sources” for the purpose of regulation, they are still diffuse sources of pollution that cannot be 

easily collected and treated by a central treatment facility, as are other point sources of pollution 

such as domestic and industrial wastewater discharges. The Department recently accepted 

delegation from the EPA for the stormwater part of the NPDES Program. It should be noted that 

most MS4 permits issued in Florida include a reopener clause that allows permit revisions to 

implement TMDLs once they are formally adopted by rule.
44

Appendix B

2004-05 Level 1 and Level 2 FLUCCS Landuse Figures for the St. Lucie Basin 

(WBIDs 3193, 3194, 3194B, 3197, 3200, 3210, 3210A, 3211, and 3218,)

Figure B.1 WBID 3193 2004-05 Level 1 and Level 2 FLUCCS Landuse
45

Figure B.2 WBID 3194 2004-05 Level 1 and Level 2 FLUCCS Landuse
46

Figure B.3 WBID 3194B 2004-05 Level 1 and Level 2 FLUCCS Landuse
47

Figure B.4 WBID 3197 2004-05 Level 1 and Level 2 FLUCCS Landuse
48

Figure B.5 WBID 3200 2004-05 Level 1 and Level 2 FLUCCS Landuse
49

Figure B.6 WBID 3210 2004-05 Level 1 and Level 2 FLUCCS Landuse
50

Figure B.7 WBID 3210A 2004-05 Level 1 and Level 2 FLUCCS Landuse
51

Figure B.8 WBID 3211 2004-05 Level 1 and Level 2 FLUCCS Landuse
52

Figure B.9 WBID 3218 2004-05 Level 1 and Level 2 FLUCCS Landuse
53

Appendix C

Total Number of Samples and Annual TN and TP Mean Concentrations by WBID 

for the St. Lucie Basin (WBIDs 3193, 3194, 3194B, 3197, 3200, 3210, 3210A, 3211, 

and 3218)

Table C.1 WBID 3193 Number of Samples and Annual TN and TP 

Concentrations

Year # 

Samples

TP 

Conc. 

(mg/L)

# 

Samples

TN 

Conc. 

(mg/L)

1996 45 0.11 45 1.04

1997 31 0.1 30 1.1

1998 32 0.14 32 1.5

1999 53 0.16 51 0.66

2000 49 0.1 49 0.61

2001 23 0.18 22 0.85

2002 26 0.13 25 0.82

2003 22 0.14 24 0.82

2004 23 0.18 22 0.9

2005 21 0.19 22 1.1

Table C.2 WBID 3194 Number of Samples and Annual TN and TP 

Concentrations

Year # 

Samples

TP 

Conc. 

(mg/L)

# 

Samples

TN 

Conc. 

(mg/L)

1996 43 0.2 42 1.33

1997 27 0.25 25 1.32

1998 26 0.31 26 1.54

1999 40 0.29 40 0.94

2000 39 0.24 39 0.9

2001 108 0.16 108 1

2002 601 0.1 595 0.9

2003 421 0.14 423 0.9

2004 369 0.14 368 0.98

2005 261 0.131 268 0.98
54

Table C.3 WBID 3194B Number of Samples and Annual TN and TP 

Concentrations

Year # 

Samples

TP 

Conc. 

(mg/L)

# 

Samples

TN 

Conc. 

(mg/L)

1996 84 0.19 84 1.3

1997 38 0.19 34 1.2

1998 42 0.26 43 1.6

1999 68 0.22 68 0.8

2000 68 0.16 68 0.8

2001 69 0.21 69 1.1

2002 237 0.15 254 0.9

2003 161 0.14 168 0.9

2004 26 0.3 26 1.03

2005 164 0.26 163 1.1

Table C.4 WBID 3197 Number of Samples and Annual TN and TP 

Concentrations

Year # 

Samples

TP

Conc. 

(mg/L)

# 

Samples

TN 

Conc. 

(mg/L)

1996 22 0.23 22 1.5

1997 62 0.24 56 1.7

1998 71 0.29 62 1.7

1999 191 0.34 187 1.6

2000 158 0.27 155 1.5

2001 83 0.25 83 1.5

2002 121 0.28 121 1.2

2003 70 0.27 66 1.4

2004 58 0.33 56 1.4

2005 90 0.32 85 1.6
55

Table C.5 WBID 3200 Number of Samples and Annual TN and TP 

Concentrations

Year # 

Samples

TP 

Conc. 

(mg/L)

# 

Samples

TN 

Conc. 

(mg/L)

1996 36 0.23 34 1.3

1997 76 0.28 79 1.6

1998 91 0.4 85 1.6

1999 106 0.5 102 1.7

2000 109 0.4 102 1.3

2001 74 0.5 75 1.6

2002 91 0.5 91 1.4

2003 83 0.34 82 1.4

2004 71 0.5 71 1.4

2005 106 0.4 139 1.6

Table C.6 WBID 3210 Number of Samples and Annual TN and TP 

Concentrations

Year # 

Samples

TP 

Conc. 

(mg/L)

# 

Samples

TN 

Conc. 

(mg/L)

1996 39 0.17 40 1.3

1997 24 0.18 22 1.3

1998 26 0.21 26 1.6

1999 64 0.21 64 0.9

2000 50 0.18 50 0.9

2001 57 0.21 57 0.1

2002 255 0.17 263 1.1

2003 160 0.18 164 1.1

2004 89 0.14 89 1.1

2005 217 0.22 217 1.4
56

Table C.7 WBID 3210A Number of Samples and Annual TN and TP 

Concentrations

Year # 

Samples

TP 

Conc. 

(mg/L)

# 

Samples

TN 

Conc. 

(mg/L)

1996 16 0.16 16 1.4

1997 10 0.2 9 1.8

1998 10 0.23 10 1.6

1999 30 0.2 30 1.2

2000 28 0.24 28 1.4

2001 37 0.25 37 1.4

2002 118 0.17 117 1.1

2003 80 0.24 80 1.4

2004 23 0.24 22 1.7

2005 22 0.23 23 1.8

Table C.8 WBID 3211 Number of Samples and Annual TN and TP 

Concentrations

Year # 

Samples

TP 

Conc. 

(mg/L)

# 

Samples

TN 

Conc. 

(mg/L)

1996 - - 

1997 - -

1998 - -

1999 - -

2000 - - 

2001 18 0.22 18 0.99

2002 83 0.15 94 0.89

2003 57 0.15 59 0.97

2004 26 0.19 30 0.88

2005 25 0.18 27 1.1
57

Table C.9 WBID 3218 Number of Samples and Annual TN and TP 

Concentrations

Year # 

Samples

TP 

Conc. 

(mg/L)

# 

Samples

TN 

Conc. 

(mg/L)

1996 22 0.13 21 1.3

1997 21 0.12 20 1.4

1998 51 0.17 49 1.7

1999 121 0.19 121 1.4

2000 173 0.17 170 1.4

2001 47 0.22 47 1.3

2002 82 0.16 82 1.2

2003 95 0.22 95 1.4

2004 80 0.18 78 1.8

2005 101 0.22 100 1.8
58

Appendix D

Total Number of Samples and BOD Mean Concentrations by WBID for the St. 

Lucie Basin (WBIDs 3193, 3194, 3194B, 3197, 3200, 3210, 3210A, 3211, and 3218)

Table D.1 BOD Average Concentration Values and Number of Samples 

from 1996 - Present

WBID # 

Samples Average Exceeded Threshold?

3193 12 1.5

3194 43 2.1 Yes

3194B 12 1.8

3197 18 2.7 Yes

3200 12 2.8 Yes

3210 28 2.0

3210A 13 2.0

3211 34 2.0

3218 15 1.2

Table D.2 BOD Average Concentration Values and Number of Samples 

from 1996 - 2005

WBID # 

Samples Average Exceeded Threshold?

3193 No Data No Data

3194 24 2.1 Yes

3194B 2 1.8

3197 3 2.6 Yes

3200 No Data No Data

3210 4 1.7

3210A No Data No Data

3211 24 2.0

3218 No Data No Data
59

Appendix E

Impaired WBID Maps with Sampling Station Locations, Yearly Statistical Values, 

and 10-year Average Flow

Figure E.1 WBID 3193 Sampling Locations and Data
60

Figure E.2 WBID 3194 Sampling Locations, Data, and Flow
61

Figure E.3 WBID 3194B Sampling Locations, Data, and Flow
62

Figure E.4 WBID 3197 Sampling Locations, Data, and Flow
63

Figure E.5 WBID 3200 Sampling Locations, Data, and Flow
64

Figure E.6 WBID 3210 Sampling Locations, Data, and Flow
65

Figure E.7 WBID 3210A Sampling Locations, Data, and Flow
66

Figure E.8 WBID 3211 Sampling Locations, Data, and Flow
67

Figure E.9 WBID 3218 Sampling Locations, Data, and Flow
68

Appendix F

Outlier Analysis Summary Results

The Tukey-Kramer Mean Comparison statistical analysis uses a t-statistic when sample sizes 

are not equal. Tukey-Kramer was designed to be used with unequal sample sizes but is 

appropriate only if population variances are equal. Database (.JMP) and Journal Files (.JRN) 

for tables and figures displaying the summarized data are available upon request. View using 

JMP software.

WBID 3193

Within the IWR database, the majority of TN and TP data (77%) for WBID 3193 is sampled at 

stations 21FLSFWMSE 01 and 21FLSFWMSE 02 (SE 01: TP mean = 0.121 mg/L, n = 135 and 

TN mean = 0.90 mg/L, n = 133; SE 02: TP mean = 0.158 mg/L, n = 134 and TN mean = 1.00 

mg/L, n = 132). All other stations within the WBID have a sample size (n) less than or equal to 

26 at each station. Using the Tukey-Kramer Mean Comparison statistical analysis with a 

significance level of 0.05, no significant difference exists between stations within the WBID. 

WBID 3194

Within the IWR database, the TN and TP data for WBID 3194 is proportional distributed across 

all sample stations. Using the Tukey-Kramer Mean Comparison statistical analysis with a 

significance level of 0.05, no significant difference exists between stations within the WBID. 

WBID 3194B

Within the IWR database, the TN and TP data for WBID 3194B is proportional distributed across 

all sample stations. Using the Tukey-Kramer Mean Comparison statistical analysis with a 

significance level of 0.05, no significant difference exists between stations within the WBID. 

WBID 3197

Within the IWR database, the majority of TN and TP data (82%) for WBID 3197 is sampled at 

the control structure station 21FLSFWMC24S49 (TP mean = 0.278 mg/L, n = 805 and TN mean 

= 1.45 mg/L, n = 773). All other stations within the WBID have a sample size (n) less than or 

equal to 22 at each station. Using the Tukey-Kramer Mean Comparison statistical analysis with 

a significance level of 0.05, no significant difference exists between stations within the WBID. 

WBID 3200

Within the IWR database, the majority of TN and TP data (88%) for WBID 3200 is sampled at 

the control structure station 21FLSFWMC23S48 (TP mean = 0.37 mg/L, n = 833 and TN mean 

= 1.49 mg/L, n = 802). All other stations within the WBID have a sample size (n) less than or 

equal to 20 at each station. Using the Tukey-Kramer Mean Comparison statistical analysis with 

a significance level of 0.05, between stations within the WBID only one station significantly 

differed from the mean. Station 21FLWPB 28010391 TP mean = 12.54 mg/L, n = 8 and TN 

mean = 38.8 mg/L, n = 7. However, further investigation is necessary into this station because 

of the extremely high unrealistic average values.

WBID 3210

Within the IWR database, the TN and TP data for WBID 3210 is proportional distributed across 

all sample stations. Using the Tukey-Kramer Mean Comparison statistical analysis with a 

significance level of 0.05, no significant difference exists between stations within the WBID. 
69

WBID 3210A

Within the IWR database, the TN and TP data for WBID 3210A is proportional distributed across 

all sample stations. Using the Tukey-Kramer Mean Comparison statistical analysis with a 

significance level of 0.05, no significant difference exists between stations within the WBID for 

TN. However, for TP only one station significantly differed from the mean between all stations 

within the WBID. Station 21FLSFWMSLT-4, located in Mapps Creek a tributary off the main 

stem of the South Fork St. Lucie River, TP mean = 0.121 mg/L, n = 70. 

WBID 3211

Within the IWR database, the TN and TP data for WBID 3211 is proportional distributed across 

all sample stations. Using the Tukey-Kramer Mean Comparison statistical analysis with a 

significance level of 0.05, no significant difference exists between stations within the WBID. 

WBID 3218

Within the IWR database, the majority of TN and TP data (90%) for WBID 3218 is sampled at 

the control structure station 21FLSFWMC44S80 (TP mean = 0.17 mg/L, n = 774 and TN mean 

= 1.47 mg/L, n = 763). All other stations within the WBID have a sample size (n) less than or 

equal to 27 at each station. Using the Tukey-Kramer Mean Comparison statistical analysis with 

a significance level of 0.05, between stations within the WBID only one station significantly 

differed from the mean. Station 21FLWPB 28010415 TP mean = 1.10 mg/L, n = 3 and TN 

mean = 3.52 mg/L, n = 3.
70

Florida Department of Environmental Protection 

Division of Water Resource Management

Bureau of Watershed Management

2600 Blair Stone Road, Mail Station 3565

Tallahassee, Florida 32399-2400

www2.dep.state.fl.us/water/