## FINAL



## FLORIDA DEPARTMENT OF ENVIRONMENTAL PROTECTION

Division of Water Resource Management, Bureau of Watershed Management



### SOUTH EAST DISTRICT • ST. LUCIE

– LOXAHATCHEE BASIN



# TMDL Report

Nutrient and Dissolved Oxygen
TMDL for the St. Lucie Basin

Kei th Parm e r, PhD
Kristina Laskis
Robert McTear
Rhonda Peets

October 2008ii 

# Acknowledgments

This study could not have been accomplished without significant support and assistance provided by Florida Department of Environmental Protection

- Tallahassee and S outheast
District Office s , 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 deline ations or analysis of the features shown.

For additional information on the watershed management approach and impaired waters
in the St. Lucie

- Loxahatchee Basin, c ontact :

Jennifer Gihring Florida Department of Environmental Protection
Bureau of Waters hed 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 Parm e r , 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

– 84 65 Fax: (850) 245

– 8 4 4 4iii 

# Contents

EXECUTIVE SUMMAR Y

________________________________ ______________ 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


## Chapt **er 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

Ta rgets

________________________________ _______________________ 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 Nutrie nt 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 NPDE S Wastewater Facilities

________________________________ _ 16 4.2.2 Municipal Separate Storm Sewer System Permittees

_______________ 18
4.2.3 Lake Okeechobee

________________________________ __________ 18
4.2.4 Groundwater

________________________________ _______________ 18


## Chapt **er 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

________________________________ _______ 22iv 

### 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 L oad 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, 31 94B, 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

________________________________ ____ 68vi 

### List of Tables

Table 2.1. Verified Impaired Listings for Nutrients and Dissolved Oxygen for
the St. Lu cie 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 S amples 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 Sampl es from

1996

- 2005

________________________________ ________________ 58vii 

### 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, 32 00, 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 Figu re E.5 WBID 3200 Sampling Locations, Data, and Flow

____________________ 6 3 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

____________________ 67viii 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

200 6 305(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

Reg ion 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. **G eological**  **Survey**

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



## South Fl **orida Water Management District**

Groundwater Data Site http://www.sfwmd.gov/pls/portal/realtime.realtime_app.rtv2?p_op=FORT_PIERCEix 

## ACRONYMS AND ABBREVIATIONS

BMAP Basin Management Action Plan
BMPs Best Management Practices
BOD Biochemic al 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 Oxyg en 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
FLU CCS 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 Po int 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

μ g/L Micrograms per liter (also parts per billio n

- 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 Webx 

### EXECUTIVE SUMMAR Y

1. I mpaired W aters R ule (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 Imp aired

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 n on
- point sources:

Point source (Municipal Separate Sewer Systems)

5 . Major NPDES dischargers into surface water:

Nonexi 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 4 1.3 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 Cana l

( 319 7) 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 6 7 lbs 38.4 Implicit

TP 8 lbs 57.2 Implicit

South For k 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. Add itional 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 w ater b ody id entification units (WBID) as detailed in the document . There are nine i mpaired 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 E stuary, these WBID s are not
considered in this TMDL becaus e 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 i n 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 rapidlyxii 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 o f 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 reduction s 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 n utrient 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 i s reflected in the Florida Department of Environmental Protection ( Department ) rotating basin evaluations and basin management action plans. While this document provides TMDLs for impaired WBID s , the TMDLs will be re

- evaluated as part of the rotating basi n 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 o xygen (DO) for the St. Lucie basin : WBIDs ( W ater B ody ID entification) 3193 ( St. Lucie River Lower Estuary), 3194 ( North Fork St. Lucie River) , 3194B (North St. Lucie Estuar y ), 3197 (C

- 24 canal), 3200 (C

- 23 canal), 3210 ( South St. Lucie Estuary )

, 3210A ( South Fork St. Lucie Ri ver ), 3211 (Bessey Creek), and 3218 (C

- 44 Canal) . U sing the methodology described in Rule 62

- 303

, Florid a Administrative Code (F.A.C.)

, Identification of I mpaired Surface Waters Rule ( IWR ) (2001a) , which identifies and verifies water quality impairments

, t he above WBIDs have been
determined to be impaired for n utrients and d issolved o xygen except WBID s 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 S t. 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 ass imilated in a waterbody, identifies the sources of the pollutant, and recommends regulatory or other actions to be taken to achieve compliance w ith applicable water quality s tan dards, based on the relationship between pollut ant sources and instream water q uality 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 di scharge 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 co mprises approximately 832

, 500 acres in Martin and St. Lucie C ounties

. Within the watershed approximately 684,087 acres are agricultural and 11 7, 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 join s the IRL

- S

. The watershed contains 15 hydrologic basins, sub

- basins, and over 40 named
tributaries. Historically, this area included a m uch smaller na tural watershed that directly contributed to the river system, and i nterior areas of Martin and St. Lucie counties contained large expanses of poorly drained wetlands that did not directly feed in to the river and estuary (Gunsalus

, 2008 )

. Wi th 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 tra nsports 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

- 2 3 and C

- 24 canals discharge to the North
Fork

. The C

- 25 canal receives agricultural runoff from northern St. Lucie C ounty and areas to
the north ; i t discharges directly into the Central Indian River Lagoon ( C

- IRL) across from the2 Fort Pierce Inlet. Howev er

, 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 ( S ime, 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 5 5.51 inches near the coast; however, rainfall amounts can vary greatly from year to year (SFWMD DBH YDRO ). The majority of the watershed’s annual rainfall comes during the wet season (May through October) from summer thunderstorms and tropical systems. Hi gh intensity rain events with short duration thunderstorms are common during the wet season in s outh 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 Ni ñ o , which causes wetter winters and drier summers (FDEP, 2001). The average summer temperature is 84 o F,
and the average winter temperature is 64 o F (NOAA, 2008).

The topography of the SLE and IRL

- S watershed reflects its location within s outheastern Florida. Elevations range in the western part of the sub

- basin around 10 to 15 feet above sea
level and in the easte rn 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 O keechobee 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 wat er quality problems
related t o phosphorus and other pollutants

**•** Requires development of Watershed Protection Plans for the St. Lucie and Caloosahatchee
watershed s by January 1, 2009

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

**•** Extends the Sa ve 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 loa d reductions identified in this TMDL and established in accordance
with s ection 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 (F DEP ) 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 geograp hic basis for assessing, reporting, and documenting water quality improvement projects, FDEP divide s basin groups into smaller areas called planning units. Planning units help organize information and management strategies around prominent
sub

- basin chara cteristics 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 waterbod y 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 ba sin

.

For illustrative purposes, t he spatial distribution and acreage of different landuse categories were identified using 2004

- 05 landuse coverage data (scale 1:60,000) provided by the SFWMD

. L anduse categories were lumped into Level 1 and Level 2 F lori da L and U se C over and
C lassification S ystem (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 ac res (30.35%) of agricultur e and 49,994 acres (41.39%) of urban

. I t e xtends 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 M ile and Five M ile 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 M ile 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 sout heastern portion of the St. Lucie County Municipal Separate Storm Sewer System ( MS4 ) area, and the northern portions of Stuart and urban Martin County.

Ten M ile 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 M ile Creek in this TMDL. Howeve r, SFWMD has made

, and continues to make

, progress in the construction, operation, and
refinement of the Ten M ile 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 M ile 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 M ile 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 converg e 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
Inlet s

. Historically, the I RL

- 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

stormwa ter 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 l oads 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 a reas with urban

storm water runoff and seepage from septic t anks 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 sedi ment stress the estuarine ecology. Other evidence to support impairment status was gathered through a FDEP Southeast District Biological S urvey 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 plann ing 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 i ncludes 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%) a re 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 populat ion 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 TI GER, 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 Bu reau 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

Count ies7 

### Figure 1.2 Planning Units and WBIDs of th e St. Lucie Basin8 

### Figure 1. 3 Key Watershed Features of the St. Lucie Basin9 

### 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 requir ements. 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 applic able water quality criteria and its designated uses. TMDLs are developed for waterbodies that are verified as not meeting their water quality standards. T hey 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 impairment s in the St. Lucie watershed. The actio n 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), U niversity 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 Divisi on 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 includ ed meetings and teleconference discussions between DEP representatives, County officials, Environmental Advocacy Groups, consultants, and other stakeholders who participate d in the process

.10 

# Chapter 2: DESCRIPTION OF WATER QUALITY

PROBLEM

2.1 Statutory Re quirements 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 199 2 . 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 (Secti on 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 En vironmental Regulation Commission (ERC) adopted the new methodology as Rule 62

- 303, F.A.C.
Identification of the IWR, (FDEP , 2001 a ) ; 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 exceedan ce 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 chlorophyl l

- a data exceeding the nutrient narrative criteria of 20 μ g/L for freshwater and 11 μ g/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 ava ilable upon request.11 

### Table 2. 1

. Verified Impaired Listing s 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

Dissolve d 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 Im paired

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 Impaired12 

### Figure 2.1 Verified Impaired WBIDs for Nutrients and Dissolved Oxygen for the St. Lucie Basin (WBIDs 319 3, 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 Criteri on Applicable to the TMDL

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

Class I Potable water supplies
Class II Shellfish propagation or harvesting
Class III Recreation, propagation, and maintenance of a healthy, well

balanced population of fish and wildlife
Class IV Agricultural wa ter supplies
Class V Navigation, utility, and industrial use (there are no state waters currently in this class)



### 3.2 Applicable Water Qual ity Standards and Numeric Water Quality Targets

The St. Lucie Basin (WBIDs 3193, 3194, 3194B, 3197, 3200, 3210, 3210 A, 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 criteri a applicable to the impairment addre ssed 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 water bodies states that DO shall not be less than 5.0 mg/L. Normal daily and seasonal fluctuati ons 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 mainta ined.



### 3.2. **2 Interpretation of Biochemical Oxygen Demand Criterion** 

Florida’s BOD criterion is narrative. F or 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, shal l 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 watershed s being
assessed led to the conclusion that BOD levels were a negative influence on the DO

concentrations. T he 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 ; n utrient concentrations of a body of water shall not be altered so as to cause an imbalance in natural populations of aquatic flo ra or fauna. The14 Depart ment currently uses chlorophyll

- a measurements as a surrogate measure for phytoplankto n population. When chlorophyll

- a concentrations above 20 μg/L are observed in freshwater systems or 11 μg/L in marine systems, there is an indica tion 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 list ed in this TMDL.



### 3.2. **4 Factors That Influence Nutrient**  **Concentrations**

The St. Lucie Estuary system receives nutrients from natural streams and rivers and structur e

controlled canal systems, surface water runoff, groundwater, and tidal influences. Nutrie nt 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. Land use changes have affected the S t. 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 & B aker, 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 nutri ents 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 t he 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 w ith 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 agricultu ral 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 wa ter 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 as sociated 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 consu med 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 ab sorb oxygen from the atmosphere is dependent on flow factors such as water depth and turbulence. Elevated nitrogen and phosphorus compounds15 contribute to excess algae growth. Under high nutrient levels

, algae grow rapidly and raise DO
concentrations duri ng 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. B OD 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 CO 2 , H 2 0, 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 a mmonia 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 proces ses 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 g enerally 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 rel ease of oxygen

demanding (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) oxy gen 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 "trapp ed" 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 stratified16 

# Chapter 4: ASSESSMENT OF SOURCES

4.1 Types of Source s

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 d iscrete 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) re defined 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 “poin t 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 methodol ogies 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 Po tential Point Sources of TN , TP, and BOD in the St. Lucie Basin (WBID s 3193, 3194, 3194B, 3197, 3200, 3210, 3210A, 3211, and 3218 )

**4.2.1 NPDES Wastewater Facilities** 

According to the FDEP W aste A pplication F acilities R eport (WAFR) database

, 15 NPDES permitt ed wastewater facilities exist in the St. Lucie basin ( Table 4.1 ). These waste water
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 h ave 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 no t included in the overall reduction. If conditions change in the permits for any of the facil ities mentioned, that change will be included as part of the
restoration effort.17 

### Table 4.1 NPDES Permitted Wastewater Facilities

WBID Facility Name Facility I D

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 Gra cewood 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 FL003700118 

### 4.2.2 Munici **pal 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 convey ing 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, Dep artment of Transportation ( F DOT) District 4 #FLR04E083, and Florida Turnpike Enterprise #FLR04E049. Figure 4.2 shows the extent of the MS4 permitted area for

eac h 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

- 4 4 Canal as

an outlet to manage water levels in the Lake . Through this connection, the L ake 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 watersh ed. 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 limnet ic zone of the lake

. I t 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 L ake 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 dif ficulties 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 Jurisdictions20 

# C hapter 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). T he Department’s preferred approach i s to use the TP and TN targets from the (IRL

- S Pl an) as the end point for calculating the TMDLs for the various WBIDs. These targets (81 μ g/L TP; 0.7 2 mg/L TN )

, applied at the Roosevelt Bridge

, are supported by several additional lines of evidence , detailed below, developed through subsequent evaluation s 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 we ll 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 Impleme ntation 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 S t. 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 fo r the St. Lucie Estuary (SLE) w ere 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 induc ed 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 (199 6 ). Th e 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 1.0 3 mg/L (DBH YDRO SFWMD 1999

- 2004) , and a 30% reduction would yield a

conc entration of 0.72 1 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 n itrogen concentrations decrease significantly between Roosevelt Bridge (monit oring station SE03; see21 Figure 1.3 ) and the Lagoon proper (monit oring 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 demon strated 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 b roader Lagoon ecosystem. Thus, given the extensive scientific work and support afforded to these targets, the IRL

- S T N and TP concentration targets, applied at Roosevelt Bridge, were used as targets in this TMDL.



### 5.1.2 Updated IRL

**- S Calculations**  **and Link**  **s to Seagrass**

Because the IRL

- S Plan calculations were conducted in 2004, SFWMD and F DEP recalculate d the original IRL

- S L agoon targets to see if there was a significant difference with the inclusion of
more recent data. Two methods were used to accomplis h this task: 1) using the original IRL

- S method (as describe d 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 μ g/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 μ g/L TP and 0.68 mg/L TN based on median values. Recalculations using the quadratic method resulted in targets of 51 μ g/L TP and 0.66 mg/L TN

. The result of b oth of
these recalculat ion efforts are very similar to the Lagoon targets outlined in the original IRL

- S

Plan. T hese recalculation efforts support the validity of the original 2004 IRL

- S Plan targets for
use under current conditions.



### 5.1.3 **Statewide Estuary Descriptive Statist**  **ics**

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 2 000

- 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 med ian TP value of 65 μ g/L and median TN value of 0.86 mg/L for the selected estuaries

. The 0.86 mg/L TN value , though s lightly higher, is comparable to that identified in the IRL

- S Plan for the SLE (0.7 2 mg/L). The 65 μ g/L TP value is slightly lower than t hat identified in the IRL

- S Plan for the SLE (81 μ g/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 dr ain mostly agricultural lands
which are connected to the estuary through a system of highly managed canal s. Th ese difference s could result in a higher phosphorus loading regime that does not affect the other
selected estuaries. Even with these difference s though, t he 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 T arget Method Summary

Method St. Lucie Estuary Targets Indian River Lagoon Targets Period of

R ecord Method of Analysis TN (mg/L) TP ( μ g/L) TN (mg/L) TP ( μ g/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

Se agrass 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 T able 5.1

, three different lines of calculation support the selection of the 2004 IRL

S TN and TP concentrations of 0. 72 mg/L and 81 μ g/L as the TMDL targets for the St. Lucie

Watershed. This weight

- of

- evidence approach to establishing nutrient targets for the TMDL support s the use of th e 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 target s support wh at 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 sedimen t 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. L ucie 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 WBID s u tilize th e 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 imp acting 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 fo r 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.
Additional ly, 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, s ome 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 val idated 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 detai led 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. Water bodies 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 nut rient target applied to WBID 3193 was applied to all WBIDS which contribute to the estuary and are listed in
Table s 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 m odel, 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 net work. 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 River (3210A) Bessey Creek (3211) 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

conce ntrations based on 10

- year measured mean annual nutrient concentrations, as displayed

in Table s 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 desc riptive 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 identi fied 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 site

specific and not representative of the C

- 23 basin.27 

### Figure 5.3 Annual Average Total Nitro gen (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 ex amination 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 f low
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 un iform 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) r epresents 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 significan t 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 si gm oidal 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 ExceededCFS



### 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 ExceededCFS30 

### 5.3.4 Load Duration Curves

After flow durations are considered, th e 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 t arget 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 reco rd. 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.

F igure 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 l ower 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 perce nt 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 provide s a way to achieve long

- term program objectives by av eraging 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 exceededTP (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 ExceededTN Load (lbs)

TN Load (lbs)

TN Target (lbs)32 

### 5.3.5 Annual Existing and Allowable Loads

After examining the load dura tion 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 annua l 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

ft acre gallons ft acre L mg 147,503 37.592,453 78.3 851,325 530,1423.1 **= ×**  **×**

**− ×−**  **×**

To calculate the target load, the same proc ess is used with a substitution of the target concentration value, C target , for the measured IWR mean annual concentration to yield a target load, L target :

et t et t 

### LfQC

arg arg 

### =××

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 T able 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 balan ce 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 0.9 16 N/A [0.72 0 ] [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 1.0 10 145

, 625 103

, 747 41

, 878 28.8 399 284

C

- 24 Canal

(3197) 178,296 1.4 92 723

, 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 1.1 68 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 0.9 45 39

, 374 29

, 981 9

, 394 23.9 108 82

C

- 44 Canal

(3218) 124,122 1.4 73 497

, 303 242

, 929 254

, 374 51.2 1

, 362 666

Period of Rec ord : 1996

- 2005
N / A

– Not A pplicable34 

### Table 5. 3 WaSh Estimated Flows with Annual Existing and

Allowable T P 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
Re duction (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 Estu ary (3194B) 53

, 009 0.193 27

, 827 11

, 67 2 16

, 156 58.1 76 32

C

- 24 Canal

(3197) 178

, 296 0.291 141

, 125 39

, 25 8 101

, 867 72.2 387 108

C

- 23 Canal

(3200) 123

, 751 0.379 127

, 572 27

, 24 8 100

, 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

, 17 8 16

, 477 61.8 73 28

Bessey Creek (3211) 15

, 318 0.166 6

, 917 3

, 37 3 3

, 544 51.2 19 9

C

- 44 Canal

(3218) 124

, 122 0.180 60

, 770 27

, 3 30 33

, 441 55.0 166 75

Period of Record : 1996

- 2005
N / A

– Not A pplicable



### 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

, 60 0 [ 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

- 200535 

### 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)

WaterbodyTN Load (lbs) Current Annual Average Load Target Annual Load



### Figure 5. 10 Current a nd 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)

WaterbodyTP Load (lbs) Current Annual Average Load Target Annual Load36 

# 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 loading s to the watershed s o 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 (Waste l oad Al locations, 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 ea rlier, the WLA is broken out into separate subcategories for wastewater discharges and stormwater discharges regulated under the NPDES Program:

TMDL **≅ ∑**  WLAs wastewater + **∑** WLAs NPDES 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 reduc tion 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 typicall y 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 no npoint 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, the y 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 other37 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

W aterbody Par ameter Annual

TM DL Target

lbs or [ C ] WLA

LA (% Reduction) MOS NPDES

Waste water (mg/L) NPDES
Stormwater (% Reduction)

St. Lucie Estuary ( 3193 ) TN [ 0.72 0 ] N / A 21.4 21.4 Implicit

TP [ 0.08 1 ] 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

( 319 7) TN 3 48,957 N/A 51. 8 51. 8 I mplicit

TP 39,258 N/A 7 2.2 7 2.2 Implicit

BOD [2.0] N/A 33.3 33.3 Implicit

C

- 23 Canal

( 3200 ) TN 242,202 N/A 5 1.7 5 1.7 Implicit

TP 2 7,248 N/A 7 8. 6 78.6 Implicit

South Fork St. Lucie Estuary ( 3210 ) TN 24, 463 N/A 38. 4 3 8. 4 Implicit

TP 2,752 N/A 5 7.2 5 7.2 Implicit

South Fork St.

Lucie River

( 3210A ) TN 90,471 N/A 47.1 47.1 Implicit

TP 10,178 N/A 6 1.8 6 1.8 Implicit

Bessey Creek ( 3211 ) TN 29,981 N/A 23.9 2 3.9 Implicit

TP 3,373 N/A 5 1.2 5 1.2 Implicit

C

- 44 Canal

( 3218 ) TN 2 42,929 N/A 5 1. 2 5 1. 2 Implic it

TP 27,330 N/A 5 5.0 55.0 Implicit

BOD [2.0] N/A 69.7 69.7 Implicit

N/A

– Not A pplicable , [ ]

– concentration in mg/L



### 6.2 Load Allocation

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

T here 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 minima l 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 water shed, 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 C hapter 4, little informa tion 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

. T he stormwa ter 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 uncerta inty issues b y incorporating a m argin o f s afety 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

– A verage annual flow s for the 10

- year period result s 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 m eeting its TMDL t arget

– I t is Department policy that a waterbo dy 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 res olving the Lake’s impairment issues on the contributors to the C

44 and southern e stuary 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 Bas in 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 clo sely 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 stake holders. 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 W atershed Plan and any related BMAPs is a reasonable means of achieving TMDLs and compliance with state water quality standards. The
SFWMD , FDACS, and F DEP are working closely together to coordinate the NEEPP and BMAP processes, avoid overlap, and ensure t hat 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 regi onal 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 proce ss to occur no less than every five years.

The BMAP will likely include other factors beyond th ese basic elements. The BMAP development process will occur with the close cooperation of local stakeholders and DEP’s partner NEEPP agencies (SFWMD and F DACS), many of whom were involved in development
of this TMDL.40 

# References

Broward County. Au gust 2003. Broward

- by

- the

- numbers

. Broward County, Office of Urban Planning and Redevelopment, Planning Services Division. No. 2. Available: http://www.broward.org/planningservices/bbtn 2.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 Flori da. 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 Demo n stration Project. Wayne County, Michigan

. PRO

- NPS

- TM27 .02

Florida Department of Environmental Protection

. Florida Watershed Restoration Act. 1999. Chapter 99

- 223, Laws of Florida.

____________ _. F ebruary 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 Manageme nt.

_____________. April 2001 a

. 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 2001 b

. Rule 62

- 302, F.A.C., S urface W ater Q uality s tandards

. Tallahassee, Florida: Division of Water Resource Management, Bureau of Watershed Management.

_____________. May 2001 b

. Rule 62

- 30 4.700 , F.A.C., Total Maximum Daily Loads

. Tallahassee, Florida: Division of Water Resourc e Management, Bureau of Watershed Management. Available: https://www.flrules.org/gateway/RuleNo.asp?ID=62

- 304.700

_____________. 200 3 . Basin Status Report: St. Lucie and Loxahatc hee . Watershed Planning and Coordination Section. Bureau of Watershed Manageme n t.

_____________. June 200 8

. 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, Fl orida 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

Gr aves, 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 i n 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
Sout hwest 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 Stormwa ter 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 Dema nd 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 data base. Available at http://my.sfwmd.gov/dbhydroplsql/show_dbkey_info.main_menu

South Florida Water Management District (SFWMD), 2003. CERP Monitoring and Assessment

Plan. Append ix A: Conceptual Ecological Models

URS 2008, WaSh Model Documentation Report, Prepared for South Florida Water management District, March 17, 2006

U.S. Census Bureau Web s ite. 200 8 . 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

M easurement and Evaluation. Last updated on Monday, May 14th, 2007. http://www.epa.gov/43 

# Append ix A

B ackground Information on Federal and State Stormwater Programs

In 1982, Florida became the first state in the country to implement statewide regulations t o 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
redu ction 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

establi shed 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 4 02(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 discha rges 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 wi th 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 f ederal program covers both new and existing discharges, while the state program focuses on new discharges. Additionally, Phase II of the NPDES Program expand s 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 require d 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 di ffuse 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 Lev el 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 Landuse45 

### Figure B .2 WBID 3194 2004

- 05 Level 1 and Level 2 FLUCCS Landuse46 

### Fig ure B.3 WBID 3194B 2004

- 05 Level 1 and Level 2 FLUCCS Landuse47 

### Figure B.4 WBID 3197 2004

- 05 Level 1 and Level 2 FLUCCS Landuse48 

### Figure B.5 WBID 3200 2004

- 05 Level 1 and Level 2 FLUCCS Landuse49 

### Figure B. 6 WBID 3210 2004

- 05 Level 1 and Level 2 FLUCCS La nduse50 

### Figure B.7 WBID 3210A 2004

- 05 Level 1 and Level 2 FLUCCS Landuse51 

### Figure B.8 WBID 3211 2004

- 05 Level 1 and Level 2 FLUCCS Landuse52 

### Figure B.9 WBID 3218 2004

- 05 Level 1 and Level 2 FLUCCS Landuse53 

# 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 #
S amples TP
C onc

. (mg/L) #
S amples TN
C onc

. ( 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 Sa mples and Annual TN and TP

Concentrations

Year #
S amples TP
C onc

. (mg/L) #
S amples TN
C onc

. (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 0.9854 

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

Concentrations

Year #
S amples TP
C onc

. (mg/L) #
S amples TN
C onc

. (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 #
S amples TP
C onc

. (mg/L) #
S amples TN
C onc

. (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 1.655 

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

Concentrations

Year #
S amples TP
C onc

. (mg/L) #
S amples TN
C onc

. (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 #
S amples TP
C onc

. (mg/L) #
S amples TN
C onc

. (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 1.456 

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

Concentrations

Year #
S amples TP
C onc

. (mg/L) #
S amples TN
C onc

. (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 #
S amples TP
C onc

. (mg/L) #
S amples TN
C onc

. (mg/L)

1996 - -

1997

- -

1998

- -

1999

- -

2000 - -

2001 18 0.22 18 0.99

2002 83 0.15 94 0.89

2 003 57 0.15 59 0.97

2004 26 0.19 30 0.88

2005 25 0.18 27 1.157 

### Table C. 9 WBID 321 8 Number of Samples and Annual TN and TP

Concentrations

Year #
S amples TP
C onc

. (mg/L) #
S amples TN
C onc

. (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 1.858 

# 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 Ye s

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 Data59 

# Appendix E

Impaired WBID Maps with Sampling Station Locations, Yearly Statistical Values,

and 10

- year Average Flow

Figu re E .1 WBID 3193 Sampling Locations and Data60 

### Figure E .2 WBID 3194 Sampling Locations, Data, and Flow61 

### Figure E .3 WBID 3194B Sampling Locations, Data, and Flow62 

### Figure E .4 WBID 3197 Sampling Locations, Data, and Flow63 

### Figure E .5 WBID 3200 Sampling Locations, Data, and Flow64 

### Figure E .6 WBID 3210 Sampling Locations, Data, and Flow65 

### Figure E .7 WBID 3210A Sampling Locations, Data, and Flow66 

### Figure E .8 WBID 3211 Sampling Locations, Data, and Flow67 

### Figure E .9 WBID 3218 Sampling Locations, Data, a nd Flow68 

# 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 popu lation 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 samp le 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, th e 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 betwe en 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 sta tions 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 2801 0391 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 i s 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 3210 A 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 321 1 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 oth er 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
dif fered 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 Re source Management
Bureau of Watershed Management

2600 Blair Stone Road, Mail Station 3565

Tallahassee, Florida 32399

- 2400 www2.dep.state.fl.us/water/