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Moccasin Creek Tidal WBID and Lake Tarpon

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					                                                             DRAFT


FLORIDA DEPARTMENT OF ENVIRONMENTAL PROTECTION
      Division of Environmental Assessment and Restoration
                Bureau of Watershed Restoration
              SOUTHWEST DISTRICT • TAMPA BASIN



                    TMDL Report
     Dissolved Oxygen and
       Nutrient TMDLs for
Moccasin Creek Tidal (WBID 1530,)
  and Lake Tarpon Canal (WBID
         1541A, 1541B)

                  Nathan Bailey, Ph.D.
                     Rhonda Peets




               February 18, 2010June 19, 2009
   DRAFT TMDL Report: Tampa Basin, Moccasin Creek, Lake Tarpon Canal Freshwater and Lake Tarpon
                                            Marine


Acknowledgments
This TMDL analysis could not have been accomplished without significant contributions from
staff in Pinellas County, the Florida Department of Environmental Protection’s Southwest District
Office, and the Watershed Evaluation and TMDL Section.

Editorial assistance provided by Jan Mandrup-Poulsen, Xueqing Gao, and Linda Lord
and research assistance by Kevin Petrus and Douglas Gilbert.

For additional information on the watershed management approach and impaired waters
in the Tampa Bay Basin, contact:

Terry Hansen
Florida Department of Environmental Protection
Bureau of Watershed Management
Watershed Planning and Coordination Section
2600 Blair Stone Road, Mail Station 3565
Tallahassee, FL 32399-2400
Email:terry.hansen@dep.state.fl.us
Phone: (850) 245–8561
Fax: (850) 245–8434

Access to all data used in the development of this report can be obtained by contacting:
Dr. Nathan Bailey
Florida Department of Environmental Protection
Bureau of Watershed Restoration
Watershed Evaluation and TMDL Section
2600 Blair Stone Road, Mail Station 3555
Tallahassee, FL 32399-2400
Email: nathan.bailey@dep.state.fl.us
Phone: (850) 245–8465.
Fax: (850) 245–8444

Kevin Petrus
Florida Department of Environmental Protection
Bureau of Watershed Restoration
Watershed Evaluation and TMDL Section
2600 Blair Stone Road, Mail Station 3555
Tallahassee, FL 32399-2400
Email: kevin.petrus@dep.state.fl.us
Phone: (850) 245–8459.
Fax: (850) 245–8444




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Florida Department of Environmental Protection
   DRAFT TMDL Report: Tampa Basin, Moccasin Creek, Lake Tarpon Canal Freshwater and Lake Tarpon
                                            Marine



Table of Contents
Chapter 1: INTRODUCTION ___________________________________ 1
      1.1 Purpose of Report______________________________________________ 1
      1.2 Identification of Waterbody______________________________________ 1
      1.3 Background __________________________________________________ 1
Chapter 2: DESCRIPTION OF WATER QUALITY PROBLEM ________ 5
      2.1 Statutory Requirements and Rulemaking History ___________________ 5
      2.2 Information on Verified Impairment _______________________________ 5
Chapter 3. DESCRIPTION OF APPLICABLE WATER QUALITY
           STANDARDS AND TARGETS _______________________ 9
      3.1 Classification of the Waterbody and Criteria Applicable to the TMDL _______ 9
      3.2 Applicable Water Quality Standards and Numeric Water Quality Target _____ 9
           3.2.2 Identification of Causative Pollutants __________________________ 10
           3.2.3 Numeric Water Quality Target Development ____________________ 12
Chapter 4: ASSESSMENT OF SOURCES _______________________ 16
      4.1 Types of Sources _____________________________________________ 16
      4.2 Potential Sources of BOD and Low DO in the [*Moccasin Creek or
          Lake Tarpon Canal*] Watershed _________________________________ 16
           4.2.1 Point Sources ___________________________________________ 16
           4.2.2 Land Uses and Nonpoint Sources ____________________________ 17
Chapter 5: DETERMINATION OF ASSIMILATIVE CAPACITY _______ 25
      5.1 Determination of Loading Capacity ______________________________ 25
      5.2 Data Used in the Determination of the TMDL ______________________ 25
      5.3 TMDL Development Process ___________________________________ 28
Chapter 6: DETERMINATION OF THE TMDL _____________________ 1
      6.1 Expression and Allocation of the TMDL ___________________________ 1
      6.2 Wasteload Allocation___________________________________________ 2
           6.2.1 NPDES Wastewater Discharges ______________________________ 2
           6.2.2 NPDES Stormwater Discharges ______________________________ 3
      6.3 Load Allocation _______________________________________________ 3
      6.4 Margin of Safety _______________________________________________ 3
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Florida Department of Environmental Protection
   DRAFT TMDL Report: Tampa Basin, Moccasin Creek, Lake Tarpon Canal Freshwater and Lake Tarpon
                                            Marine


Chapter 7: TMDL IMPLEMENTATION ___________________________ 4
      7.1 Basin Management Action Plan __________________________________ 4
References ________________________________________________ 6
Appendices ________________________________________________ 7
      Appendix A: Sample Stations and Median Concentration Data ___________ 7
      Appendix B: Background Information on Federal and State
         Stormwater Programs __________________________________________ 8
      Appendix C: Reference Approach Information _________________________ 9
      Appendix D: Comments and Responses _____________________________ 16
           D-1: Responses to FDOT Comments ______________________________ 17
           D-2: Responses to Pinellas County Comments ______________________ 31



List of Tables
Table 2.1.     Verified Impairments for Moccasin Creek Tidal (WBID 1530) and
               Lake Tarpon (WBID 1541A, 1541B) ____________________________ 6
Table 2.2.     Summary of Dissolved Oxygen Data for Moccasin Creek Tidal
               (WBID 1530), and Lake Tarpon Canal (WBID 1541A, 1541B)
               (January 1, 2000–June 30, 2007) ______________________________ 6
Table 3.1 Tampa Bay Estuary Program Targets _____________________________ 10
Table 3.2 Allen Creek and Cross Canal North TN and Chlorophyll-A _____________ 10
Table 3.3 Stream and Estuary Target Concentrations by Ecoregion _____________ 13
Table 3.4. Verified Period Summary of TN, TP, and B.O.D. Median
               Concentrations in Moccasin Creek, Lake Tarpon Canal Marine,
               And Lake Tarpon Canal Fresh _______________________________ 15
Table 4.1a.     Level 1 Land Uses in the Moccasin Creek, WBID 1530 ___________ 17
Table 4.1b.    Level 1 Land Uses in the Lake Tarpon Canal Marine, WBID
               1541A __________________________________________________ 19
Table 4.1c.    Level 1 Land Uses in the Lake Tarpon Canal Fresh, WBID 1541B ___ 19
Table 4.2a.     Level 2 Land Use Categories in the Gordon Moccasin Creek
               watershed, WBID 1530 _____________________________________ 19
Table 4.2b.     Level 2 Land Use Categories in the Lake Tarpon Canal Marine
               (1541A) watershed. _______________________________________ 20
Table 4.c.     Classification of Level 2 Land Use Categories in the Lake Tarpon
               Canal – Fresh watershed (1541B) ____________________________ 20
Table 4.3a.     Moccasin Creek Land Use Categories and Corresponding
               Runoff, 2000–07 __________________________________________ 21
Table 4.3b.     Tarpon Lake Canal Marine Land Use Categories and
               Corresponding Runoff, 2000–07 ______________________________ 22


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Florida Department of Environmental Protection
   DRAFT TMDL Report: Tampa Basin, Moccasin Creek, Lake Tarpon Canal Freshwater and Lake Tarpon
                                            Marine


Table 4.3c.     Tarpon Lake Canal Fresh Use Categories and Corresponding
              Runoff, 2000–07 __________________________________________ 22
Table 4.4a.    Moccasin Creek Land Use Categories and Corresponding EMC
              Contributions Based on 2000–07 Rainfall_______________________ 23
Table 4.4b.    Lake Tarpon Canal Marine Land Use Categories and
              Corresponding EMC Contributions Based on 2000–07 Rainfall ______ 23
Table 4.4c Tarpon Lake canal Fresh Land Use Categories and Corresponding
              EMC Contributions Based on 2000–07 Rainfall __________________ 24
Table 5.1a.   Data Collectors and Station List for the Moccasin Creek ___________ 25
Table 5.1b.   Station List for the Lake Tarpon Canal Marine ___________________ 26
Table 5.1c.   Station List for the Lake Tarpon Canal Fresh ____________________ 26
Table 5.2.    Moccasin Creek, Lake Tarpon Marine and Fresh TN Percent
              Reduction Table, 2000–07 __________________________________ 30
Table 6.1.    TMDL Components and Current Loadings for the Moccasin Creek
              (WBID 1530) and Lake Tarpon Canal (WBIDs 1541A and 1541B) ____ 2
Table A.1.    Freshwater Sample Stations in the Southwest Coast Planning Unit
              Used in the TN–DO Correlation _______________________________ 7
Table C-1: Tampa Bay Watershed WBIDs Used for Nutrient Target Setting _______ 10
Table C-2: Tampa Bay Watershed Station and Ecoregion Nutrient Results ________ 11




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Florida Department of Environmental Protection
   DRAFT TMDL Report: Tampa Basin, Moccasin Creek, Lake Tarpon Canal Freshwater and Lake Tarpon
                                            Marine


List of Figures
Figure 1.1.   Location of Moccasin Creek and Lake Tarpon Canal in Pinellas
              County and Major Geopolitical Features in the Area _______________ 2
Figure 1.2.   Location of Moccasin Creek and Lake Tarpon Canal _______________ 3
Figure 2.1.   Dissolved Oxygen Measurements for Moccasin Creek Tidal,
              WBID 1530 (January 2000 – June 2007) ________________________ 7
Figure 2.1.   Dissolved Oxygen Measurements for Lake Tarpon Canal, WBID
              1541A (March 2005 – November 2005) _________________________ 7
Figure 2.1.   Dissolved Oxygen Measurements for Lake Tarpon Canal, WBID
              1541B (January 2000 – June 2007) ____________________________ 8
Figure 3.1a   Chlorophyll a vs. TN Moccasin Creek __________________________ 11
Figure 3.1b   Chlorophyll a vs. TN, Lake Tarpon Canal _______________________ 11
Figure 4.1.   Moccasin Creek Tidal, Lake Tarpon Canal Marine, and Lake
              Tarpon Canal Fresh Land uses. ______________________________ 18
Figure 5.1.   Major Sample Stations for Moccasin Creek and Lake Tarpon
              Canal Watersheds. ________________________________________ 27
Figure C-1 – Waterbodies in the Tampa Bay Watershed Used to Develop
              Nutrient Targets. __________________________________________ 47




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Florida Department of Environmental Protection
   DRAFT TMDL Report: Tampa Basin, Moccasin Creek, Lake Tarpon Canal Freshwater and Lake Tarpon
                                            Marine


Websites
Florida Department of Environmental Protection, Bureau of
Watershed Restoration
      Total Maximum Daily Load (TMDL) Program
      http://www.dep.state.fl.us/water/tmdl/index.htm
      Identification of Impaired Surface Waters Rule
     https://www.flrules.org/gateway/chapterhome.asp?chapter=62-303
      STORET Program
      http://www.dep.state.fl.us/water/storet/index.htm
      2008 Integrated305(b) Report
     http://www.dep.state.fl.us/water/tmdl/docs/2008_Integrated_Report.pdf
      Criteria for Surface Water Quality Classifications
      http://www.dep.state.fl.us/water/wqssp/classes.htm
      Basin Status Report for the Tampa Bay Basins
      http://www.dep.state.fl.us/water/tmdl/stat_rep.htm
      Basin Water Quality Assessment Report for the Tampa Bay Basins
      http://www.dep.state.fl.us/water/tmdl/stat_rep.htm

U.S. Environmental Protection Agency
     Region 4: Total Maximum Daily Loads in Florida
     http://www.epa.gov/region4/water/tmdl/florida/
     National STORET Program
     http://www.epa.gov/storet/




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Florida Department of Environmental Protection
   DRAFT TMDL Report: Tampa Basin, Moccasin Creek, Lake Tarpon Canal Freshwater and Lake Tarpon
                                            Marine




Chapter 1: INTRODUCTION

1.1 Purpose of Report
This report presents the Total Maximum Daily Load (TMDL) for low dissolved oxygen (DO) for
Moccasin Creek Tidal (WBID 1530) and Lake Tarpon Canal (WBID 1541A, 1541B), waterbodies
in the Tampa Bay Basin. These waterbodies were verified impaired for low DO and therefore
was included on the Verified List of impaired waters for the Tampa Bay Basin that was adopted
by Secretarial Order on June 3, 2008. This TMDL establishes the allowable Nutrient loadings to
these waterbodies that would restore them so that they meet applicable water quality criterion
for DO.


1.2 Identification of Waterbody
Moccasin Creek and Lake Tarpon Canal are located in the northeast portion of Pinellas County.
Moccasin Creek is within the boundaries of the City of Oldsmar, with a population of
approximately 13,477 people (U.S. Census Bureau, 2007). Lake Tarpon Canal’s eastern edge
is also located in the City of Oldsmar and the southwestern edge located in the City of Safety
Harbor (Figure 1.1). Moccasin Creek (~1.75 miles in length) flows primarily in a southeasterly
direction entering Tampa Bay at its northwestern edge, approximately 2 miles southeast of Lake
Tarpon, and drains an area of about 0.89 square miles. Lake Tarpon Canal runs along the west
side of Moccasin Creek for (~3 miles). The head waters of the canal originate from Lake Tarpon
and empties out into Tampa Bay. The canal is lined on both sides with homes, ponds and some
open land areas. McMullen Booth Road runs parallel to the upper portion of the canal.
Additional information about the river’s hydrology and geology are available in the Tampa Bay
Basin Status Report (Florida Department of Environmental Protection, [Department], 2001).

For assessment purposes, the Florida Department of Environmental Protection (Department)
has divided the Tampa Bay Basin into water assessment polygons with a unique waterbody
identification (WBID) number for each watershed or stream reach. The Moccasin Creek and
Lake Tarpon watersheds are identified as WBID 1530, and WBID 1541A, 1541B, respectively.
(Figure 1.2).


1.3 Background
This report was developed as part of the Department’s watershed management approach for
restoring and protecting state waters and addressing TMDL Program requirements. The
watershed approach, which is implemented using a cyclical management process that rotates
through the state’s 52 river basins over a 5-year cycle, provides a framework for implementing
the TMDL Program–related requirements of the 1972 federal Clean Water Act and the 1999
Florida Watershed Restoration Act (FWRA) (Chapter 99-223, Laws of Florida).




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Florida Department of Environmental Protection
   DRAFT TMDL Report: Tampa Basin, Moccasin Creek, Lake Tarpon Canal Freshwater and Lake Tarpon
                                            Marine




Figure 1.1. Location of Moccasin Creek and Lake Tarpon Canal in Pinellas
            County and Major Geopolitical Features in the Area


                                                 2
Florida Department of Environmental Protection
   DRAFT TMDL Report: Tampa Basin, Moccasin Creek, Lake Tarpon Canal Freshwater and Lake Tarpon
                                            Marine




Note: FDOT Local Roads are for illustration and not meant to be a depiction of all FDOT local roads.

Figure 1.2. Location of Moccasin Creek and Lake Tarpon Canal



                                                    3
Florida Department of Environmental Protection
   DRAFT TMDL Report: Tampa Basin, Moccasin Creek, Lake Tarpon Canal Freshwater and Lake Tarpon
                                            Marine


A TMDL represents the maximum amount of a given pollutant that a waterbody can assimilate
and still meet water quality standards, including its applicable water quality criteria and its
designated uses. TMDLs are developed for waterbodies that are verified as not meeting their
water quality standards. They provide important water quality restoration goals that will guide
restoration activities.
This TMDL Report may be followed by the development and implementation of a restoration
planBasin Management Action Plan, or BMAP, designed to reduce the amount of nutrients that
caused the verified impairment of the tidal portion of Moccasin Creek (WBID 1530) and the Lake
Tarpon Canal (WBID 1541A,1541B). These activities will depend heavily on the active
participation of the Southwest Florida Water Management District (SWFWMD), Pinellas
County’s Department of Environmental Management (PDEM), local governments, 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
TMDLs for impaired waterbodies.




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Florida Department of Environmental Protection
   DRAFT TMDL Report: Tampa Basin, Moccasin Creek, Lake Tarpon Canal Freshwater and Lake Tarpon
                                            Marine


Chapter 2: DESCRIPTION OF WATER QUALITY
PROBLEM

2.1 Statutory Requirements and Rulemaking History
Section 303(d) of the federal Clean Water Act requires states to submit to the U.S.
Environmental Protection Agency (EPA) lists of surface waters that do not meet applicable
water quality standards (impaired waters) and establish a TMDL for each pollutant causing
impairment of listed waters on a schedule. The Department has developed such lists,
commonly referred to as 303(d) lists, since 1992. The list of impaired waters in each basin,
referred to as the Verified List, is also required by the FWRA (Subsection 403.067[4], Florida
Statutes [F.S.]); the state’s 303(d) list is amended annually to include basin updates.

Florida’s 1998 303(d) list included 47 waterbodies in the Tampa Bay Basin. However, the
FWRA (Section 403.067, F.S.) stated that all previous Florida 303(d) lists were for planning
purposes only and directed the Department to develop, and adopt by rule, a new science-based
methodology to identify impaired waters. After a long rulemaking process, the Environmental
Regulation Commission adopted the new methodology as Rule 62-303, Florida Administrative
Code (F.A.C.) (Identification of Impaired Surface Waters Rule, or IWR), in April 2001; the rule
was modified in 2006 and 2007.

2.2 Information on Verified Impairment
The Department used the IWR to assess water quality impairments in Moccasin Creek (WBID
1530) and Lake Tarpon Canal (WBID 1541A, 1541B) watersheds and verified the impairments
during the second cyle of the TMDL program (Table 2.1). Table 2.2 summarizes the Dissolved
Oxygen data collected during the verification period (January 1, 2000, through June 30, 2007).
The projected year for the [1998 303(d) listed] DO TMDL for Moccasin Creek (WBID 1530) and
Lake Tarpon Canal (WBID1541A, 1541B) was 2008, but the Settlement Agreement between
EPA and Earthjustice, which drives the TMDL development schedule for waters on the 1998
303(d) list, allows an additional nine months to complete the TMDLs. As such, this TMDL must
be adopted and submitted to EPA by September 30, 2009.

These waterbodies were verified as impaired based on Dissolved Oxygen because, using the
IWR methodology, more than 10 percent of the values exceeded the Class III marine and fresh
water criterion. The Dissolved Oxygen data used in this report are based on the IWR Run35
database. The verified impairments were based on data collected by Pinellas County and the
DEP’s Southwest District, WBID location and STORET stations are shown in Figure 5.1.
Figure 2.1 displays the median monthly DO data collected during the verified period (January 1,
2000 – June 30, 2007) for Moccasin Creek (WBID 1530,) and Lake Tarpon Canal (WBID
1541A, 1541B).




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Florida Department of Environmental Protection
    DRAFT TMDL Report: Tampa Basin, Moccasin Creek, Lake Tarpon Canal Freshwater and Lake Tarpon
                                             Marine


Table 2.1. Verified Impairments for Moccasin Creek Tidal (WBID 1530) and Lake
           Tarpon (WBID 1541A, 1541B)
                             Water-                           1998 303(d)                                      Priority for
           Waterbody                     Waterbody                                  Parameter Causing
WBID                         body                            Parameters of                                       TMDL
           Segment                         Class                                       Impairment
                             Type                              Concern                                        Development
            Moccasin
1530                         Estuary          3M            Dissolved Oxygen           Total Nitrogen              Low
           Creek Tidal
           Lake Tarpon
1541A                        Estuary          3M            Dissolved Oxygen           Total Nitrogen              Low
              Canal
           Lake Tarpon
1541B                        Stream           3F            Dissolved Oxygen           Total Nitrogen              Low
              Canal
**Note – WBID 1530 (Moccasin Creek Tidal) and WBID (1541A, 1541B) Lake tarpon was included on the 1998 303(d) List for
Dissolved Oxygen with a TMDL priority of Low and due date of 2008.




Table 2.2. Summary of Dissolved Oxygen Data for Moccasin Creek Tidal
           (WBID 1530), and Lake Tarpon Canal (WBID 1541A, 1541B)
           (January 1, 2000–June 30, 2007)
              Total        IWR-required
                                                    Number of       Number of
             Number          number of
  WBID                                               observed      seasons data       Mean     Median      Min      Max
               of         exceedances for
                                                   exceedances     were collected
             Samples      the Verified List
   1530         15                5                    9                  4             4.0       3.6       0.7    10.13
  1541A         22                5                    5                  4             5.7       6.0      2.29    10.36
  1541B         90                14                   49                 4             4.9       4.7      0.18    10.42




                                                             6
Florida Department of Environmental Protection
   DRAFT TMDL Report: Tampa Basin, Moccasin Creek, Lake Tarpon Canal Freshwater and Lake Tarpon
                                            Marine


                                                                                   Mocassin Creek Tidal (WBID 1530) Dissolved Oxygen
                                                                                  Monthly Measurem ents (January 1, 2000 - June 30, 2007)
                                                                       10

                                                                        9




                                             Dissolved Oxygen (mg/L)
                                                                        8

                                                                        7

                                                                        6

                                                                        5

                                                                        4

                                                                        3

                                                                        2

                                                                         1

                                                                        0




                                                                                                                                            Jul
                                                                                Jan

                                                                                           Feb




                                                                                                                               Jun




                                                                                                                                                                          Oct
                                                                                                 Mar



                                                                                                                         May




                                                                                                                                                                                     Nov

                                                                                                                                                                                              Dec
                                                                                                                                                                  Sept
                                                                                                                                                           Aug
                                                                                                          Apr


                                                                                                                Dissolved Oxygen Criterion



Figure 2.1. Dissolved Oxygen Measurements for Moccasin Creek
            Tidal, WBID 1530 (January 2000 – June 2007)


                                                                                Lake Tarpon Canal (WBID 1541A) Dissolved Oxygen Monthly
                                                                                     Measurem ents (March, 2005 - Novem ber, 2005 )
                                                           14


                                                           12
                   Dissolved Oxygen (mg/L)




                                                           10


                                                                  8


                                                                  6


                                                                  4


                                                                  2


                                                                  0
                                                                       Mar-05




                                                                                                                               Jul-05




                                                                                                                                                                            Oct-05
                                                                                                 May-05


                                                                                                                Jun-05




                                                                                                                                                                                           Nov-05
                                                                                                                                                                 Sep-05
                                                                                      Apr-05




                                                                                                                                                  Aug-05




                                                                                                            Dissolved Oxygen Criterion




Figure 2.1. Dissolved Oxygen Measurements for Lake Tarpon Canal,
            WBID 1541A (March 2005 – November 2005)




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Florida Department of Environmental Protection
   DRAFT TMDL Report: Tampa Basin, Moccasin Creek, Lake Tarpon Canal Freshwater and Lake Tarpon
                                            Marine




                                                   Lake Tarpon Canal (WBID 1541B) Dissolved Oxygen Monthly
                                                        Measurements (January 1, 2000 - June 30, 2007)
                                         8

                                         7
               Dissolved Oxygen (mg/L)


                                         6

                                         5

                                         4

                                         3

                                         2

                                         1

                                         0
                                                                      May
                                                          Mar

                                                                Apr




                                                                                                               Nov
                                                                                            Aug

                                                                                                  Sept

                                                                                                         Oct




                                                                                                                     Dec
                                             Jan

                                                    Feb




                                                                            Jun

                                                                                      Jul


                                                                      Dissolved Oxygen Criterion




Figure 2.1. Dissolved Oxygen Measurements for Lake Tarpon Canal,
            WBID 1541B (January 2000 – June 2007)




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Florida Department of Environmental Protection
   DRAFT TMDL Report: Tampa Basin, Moccasin Creek, Lake Tarpon Canal Freshwater and Lake Tarpon
                                            Marine


Chapter 3. DESCRIPTION OF APPLICABLE WATER
QUALITY STANDARDS AND TARGETS

3.1 Classification of the Waterbody and Criteria Applicable to the TMDL
Florida’s surface waters are protected for five designated use classifications, as follows:

     Class I Potable water supplies
     Class II Shellfish propagation or harvesting
     Class III Recreation, propagation, and maintenance of a healthy, well-
               balanced population of fish and wildlife
     Class IV Agricultural water supplies
     Class V Navigation, utility, and industrial use (there are no state waters
               currently in this class)

Moccasin Creek Tidal (WBID 1530) and Lake Tarpon Canal (WBID 1541A, 1541B) are Class III
waterbodies, with a designated use of recreation, propagation, and the maintenance of a
healthy, well-balanced population of fish and wildlife. The criteria applicable to this TMDL report
are the Class III criterion for dissolved oxygen and nutrients, for the respective freshwater and
marine portions.nutrients.


3.2 Applicable Water Quality Standards and Numeric Water Quality Target

3.2.1 Dissolved Oxygen Criterion
The Class III marine criteria for Dissolved Oxygen as established by Rule 62-302,530(30),
F.A.C., states the following: Dissolved Oxygen shall not average less than 5.0 milligrams per
liter (mg/L) in a 24-hour period and shall not be less than 4 mg/L, and that normal daily and
seasonal fluctuations above these levels shall be maintained. The Class III freshwater criteria
for Dissolved Oxygen as established by Rule 62-302,530(30), F.A.C., states that dissolved
oxygen shall not be less than 5 mg/L, and that normal daily and seasonal fluctuations above this
level shall be maintained.

3.2.2 Nutrient Criterion

Florida’s Nutrient Criterion is narrative only, i.e. nutrient concentrations of a body of water shall
not be altered so as to cause imbalance in natural populations of aquatic flora or fauna.
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 estuaries based on annual average chlorophyll a levels, these thresholds are not standards
and need not be used as the nutrient-related water quality target for TMDLs. It should be
recognized that the IWR thresholds were developed using statewide average conditions, the
IWR (Section 62-303.450, F.A.C.) specifically allows the use of alternative site-specific
thresholds that more accurately reflect conditions beyond which an imbalance in flora or fauna
occurs in the waterbody.


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Florida Department of Environmental Protection
   DRAFT TMDL Report: Tampa Basin, Moccasin Creek, Lake Tarpon Canal Freshwater and Lake Tarpon
                                            Marine


3.2.2 Identification of Causative Pollutants
After verification of the low DO in Moccasin Creek and Lake Tarpon Canal, the Department
identified the causative pollutants by investigating those parameters typically responsible for
depressed DO. One method of identifying causative pollutants is to use statewide screening
level concentrations set at the 70th percentile of all STORET data across the state from 1970 to
1987. This approach is useful if there are no significant regional differences in what is defined
as a waterbody meeting its intended designated uses. The Department’s statewide screening
level for streams is for freshwater; 2.0 mg/L for BOD5, 1.6 mg/L for TN, and 0.22 mg/L for TP,
and for marine water is 2.1 mg/L for BOD5, 1.0 mg/L for TN, and 0.19 mg/L for TP. But the
department has noted that there are significantly lower nutrient levels leading to impairment in
south Florida than the statewide screening levels indicated. Other required considerations
include the restrictions or nutrient targets of the receiving waters of the surface waters being
analyzed. In the case of those waters in the Old Tampa Bay Planning area, there are
Chlorophyll-a Targets that must be met. For Tampa Bay these targets are as stated below in
Table 3.1.
                   Table 3.1 Tampa Bay Estuary Program Targets

                                 Tampa Bay                 Tampa Bay Estuary
                                 Segments                   Program Targets
                          Lower Tampa Bay                       5.1 ug/L
                          Middle Tampa Bay                      8.5 ug/L
                          Old Tampa Bay                         9.3 ug/L
                          Hillsborough Bay                      15 ug/L

The Chorophyll-a target relevant to Moccasin Creek Tidal and Lake Tarpon Canal Marine is that
for Old Tampa Bay, (9.3 micrograms per liter (ug/L). The Tampa Bay Estuary Program’s Old
Tampa Bay Target is the primary tool when determining the Total Nitrogen target for Bishop and
Mullet Creek Tidal. The estuary target must be that total nitrogen concentration is consistent
with a 9.3 ug/L estuary target. To obtain this value, the Chlorophyll a of all the applicable bay
WBIDs for Verified Period samples were compared to the total nitrogen concentration in those
Bay WBIDs. The Total Nitrogen levels measured when the chla was at or below 9.3 ug/L could
thus be determined as the target concentrations for Mullet Creek Tidal and Bishop Creek Tidal.
Table 3.2 shows the Chla concentrations and the corresponding total nitrogen concentrations
for Moccasin Creek (Tidal) and Lake Tarpon Canal-Marine.

Table 3.2 Allen Creek and Cross Canal North TN and Chlorophyll-A

                                       Lake Tarpon
             Moccasin Creek
                                       Canal (WBID
  YEAR        (WBID 1530)
                                         1541A)
              Chl-a        TN         Chl-a      TN
    2000        8.24       0.945
    2001       10.51       1.167
    2002         5.9        1.11
    2003       40.55
    2004
    2005       33.67       1.194           26    1.11


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Florida Department of Environmental Protection
                          DRAFT TMDL Report: Tampa Basin, Moccasin Creek, Lake Tarpon Canal Freshwater and Lake Tarpon
                                                                   Marine


Because of the lack of such data for Lake Tarpon Canal Marine, the data from Lake Tarpon
Canal Marine was grouped with the Moccasin Creek data in pursuit of developing a more
reliable relationship between Chla and TN. Figures 3.1a and 3.1b graph regression equations
of the Chla-TN relationships of Moccasin Creek and Lake Tarpon Canal.

                                         Mocassin Creek Annual Average Chlorophyll a vs. TN
                                                          Verified Period
                           1.4




                           1.2




                             1
   Total Nitrogen (mg/L)




                           0.8
                                                                                            Chla = 0.005 TN + 1.0305
                                                                                                   R2 = 0.3266
                           0.6




                           0.4




                           0.2




                             0
                                 0   5         10               15           20             25             30         35        40        45
                                                                          Chlorophyll a (ug/L)


Figure 3.1a Chlorophyll a vs. TN Moccasin Creek

                                            (Also includes single Annual Median from Lake Tarpon Canal Marine)
                           1.4




                           1.2




                            1
  Total Nitrogen (mg/L)




                           0.8




                           0.6

                                                                                    Chla = 0.0042 TN + 1.0333
                                                                                           R2 = 0.2843
                           0.4




                           0.2




                            0
                                 0   5       10            15           20             25             30         35        40        45
                                                                       Chlorophyll a (ug/L)



Figure 3.1b Chlorophyll a vs. TN, Lake Tarpon Canal




                                                                                                 11
Florida Department of Environmental Protection
   DRAFT TMDL Report: Tampa Basin, Moccasin Creek, Lake Tarpon Canal Freshwater and Lake Tarpon
                                            Marine


Regardless of which regression equation is used (from Figure 3.1a and 3.1b), 1.07 mg/L is the
calculated TN when Chla equals 9.3 ug/L. Although this assessment may demonstrate that a
1.07 mg/L concentration is protective of the Old Tampa Bay 9.3 ug/L Chla criteria, it does not
demonstrate that it is protective of the Dissolved Oxygen Criteria of 4.0 mg/L.

3.2.3 Numeric Water Quality Target Development

To address the DO and nutrient impairment in developing the TMDL, a reference waterbody
approach was used to establish nutrient concentration targets for total nitrogen and total
phosphorus. This approach was used to establish nutrient targets for the impaired stream and
estuary segments in the Tampa Bay Basin and Hillsborough River Basin with draft dissolved
oxygen and nutrient TMDLs proposed by the Department in 2009. The target concentrations
were derived by using data from waters not impaired for DO and nutrients in the Tampa Bay
watershed that were similar to the impaired waterbodies, in terms of hydrologic conditions and
drainage area size. By having applied the EPA recommended TMDL development procedures
for non-numeric water quality standards, there is the expectation that the DO and nutrient
criteria will be met, if the selected target values are achieved (EPA, 1999).

The methods used to develop the restoration targets are described below. Separate targets
were developed for the Tampa Bay watershed streams and estuaries in both the “Bone Valley”
and “Peninsula” ecoregions.

Setting the Restoration Targets:

      1. WBIDs used in this process are WBIDs assessed as “Not Impaired” for both Dissolved
         Oxygen and Nutrients (based on chlorophyll a) following the Florida Impaired Waters
         Rule Assessment Methodology. The water quality assessments are based on recent
         data collected in the Basin Rotation Cycle 2 Verified Periods in the stream and estuary
         WBIDs of the Tampa Bay watershed.

      2. From this set of “Not Impaired” waters, WBIDs were removed from further consideration
         if a point source discharges to surface waters in the WBID or if the drainage area of the
         WBID was determined to be appreciably different than that of the impaired WBIDs for
         which reference target conditions are being developed.

      3. For streams, this process resulted in excluding three stream WBIDs because they
         directly receive point source discharge effluent. An additional four stream WBIDs on
         the main stem of the rivers flowing to Tampa Bay, (one WBID each along the
         Hillsborough, Alafia, Little Manatee, and Manatee Rivers) were excluded because their
         drainage areas are larger than the impaired stream WBIDs for which the nutrient targets
         are being developed.

      4. For estuaries, two WBIDs were excluded because they receive input from point source
         discharges. Additionally, all the WBIDs located within the major Tampa Bay segments
         were excluded due to their larger size relative to the tidal streams and embayments for
         which the nutrient targets are being developed.


                                                 12
Florida Department of Environmental Protection
   DRAFT TMDL Report: Tampa Basin, Moccasin Creek, Lake Tarpon Canal Freshwater and Lake Tarpon
                                            Marine


      5. The stream and estuary WBIDs that that were not excluded in the screening process
         and were used for nutrient target setting are listed in Table C-1 and displayed in Figure
         C-1 in Appendix C.

      6. For the set of WBIDs used to develop the nutrient targets, the concentrations were
         calculated using the Cycle 2 verified period nutrient data, obtained from IWR Database
         Run 35_2, that covers the period of 2000-2007.

      7. The data were first analyzed by station and year by calculating annual station medians
         for total nitrogen and total phosphorus. Station data included in this process had to
         have a minimum of 8 samples in a calendar year for an annual median to be calculated.

      8. Separate annual averages of the station medians were then calculated for the streams
         and estuaries in both the Bone Valley and Peninsula ecoregions. For each of these
         four groups the average of the annual averages for all the station medians in each
         reference group in the verified period were calculated and selected as the nutrient
         target concentrations (each year of the verified period, where sufficient data were
         available, provided equal weight). The station medians and averages used to establish
         the targets are provided in Table C-2 in Appendix C.

      9. The resulting nutrient concentration targets from the data analyses are shown in Table
         3.1.


Table 3.3 Stream and Estuary Target Concentrations by Ecoregion.


                                        Bone Valley                Peninsula
        Parameter                 Stream         Estuary    Stream         Estuary
 Total Nitrogen (mg/L)            1.16           1.04        0.87           0.97
 Total Phosphorus (mg/L)          0.473          0.309       0.181          0.158


The nutrient targets are used for establishing the TMDL by calculating the reductions needed in
existing concentrations to meet the targets. The process for calculating pollutant reductions is
described in Chapter 5.To determine a nutrient level protective of a dissolved oxygen
concentration of not below 4 mg/L, with a mean of at least 5.0 mg/L, a reference approach was
pursued. The concentrations of TN, DO, and Chlorophyll a was observed for Sample Stations
in WBIDs found not to be impaired for DO nor Nutrients and summarized in Table 3.3.




                                                      13
Florida Department of Environmental Protection
   DRAFT TMDL Report: Tampa Basin, Moccasin Creek, Lake Tarpon Canal Freshwater and Lake Tarpon
                                            Marine


Table 3.3 Statistical Station Summaries of “Not Impaired” and “Impaired”
           Tampa Bay and Tampa Bay Tributary Sample Stations




Note: NI = Not Impaired for Dissolved Oxygen and not Impaired for Nutrients by FDEP IWR Assessment.


Table 3.3 shows that for “Not Impaired” WBIDs in Marine Estuary Tampa Bay WBIDs have an
average median sample station TN concentration of 0.62 mg/L, the annual median Dissolved
Oxygen concentration is 6.11 mg/L, and a mean Chlorophyll a concentration of 7.58 mg/L. In
the nearby Tampa Bay Tributaries Group, the median sample station D.O. for non Impaired
WBIDs is 0.88 mg/L, and although there were not enough Chlorophyll a samples to obtain a
median corresponding concentration, the Dissolved Oxygen median for these WBIDs is 6.39
mg/L, also well above the 4.0 mg/L Florida criteria, Thus, the TN target selected is the average
of these two sets of ‘Not Impaired’ WBIDs, or 0.75 mg/L. A target of 0.75 mg/L should be both
protective of the Old Tampa Bay Chlorophyll-a limit, be protective of the dissolved oxygen
criteria, and meet reasonable expectations of attainability when compared to standards of local
WBIDs impaired neither for DO nor Nutrients.
 The present nutrient and BOD levels in Moccasin Creek (1530), Lake Tarpon Canal Marine
(1541A), and Lake Tarpon Canal Fresh (1541B) are shown in Table 3.4.




                                                 14
Florida Department of Environmental Protection
     DRAFT TMDL Report: Tampa Basin, Moccasin Creek, Lake Tarpon Canal Freshwater and Lake Tarpon
                                              Marine


  Table 3.4. Verified Period Summary of TN, TP, and B.O.D. Median
             Concentrations in Moccasin Creek, Lake Tarpon Canal Marine,
             And Lake Tarpon Canal Fresh

                      IWR Verified Period Summary (2000 - 2007)

                                                       Total
                            Total Nitrogen                                5 Day Bod
                                                    Phosphorus
       WBID
                            Sample   Concent.      Sample    Concent.   Sample   Concent.
                             Count    mg/L          Count     Mg/L       Count    mg/L
  Moccasin Creek
    (WBID 1530)                 75        1.24         76       0.225       49         2
 Lake Tarpon Canal
Marine (WBID 1541A)             22       1.108         22       0.245       22     3.15 *
 Lake Tarpon Canal
Fresh (WBID 1541B)              77        0.96         80       0.058       31         2
  * BOD data under review




                                                        15
  Florida Department of Environmental Protection
   DRAFT TMDL Report: Tampa Basin, Moccasin Creek, Lake Tarpon Canal Freshwater and Lake Tarpon
                                            Marine


Chapter 4: ASSESSMENT OF SOURCES

4.1 Types of Sources
An important part of the TMDL analysis is the identification of pollutant source categories,
source subcategories, or individual sources of low DO in the watershed and the amount of
pollutant loading contributed by each of these sources. Sources are broadly classified as either
“point sources” or “nonpoint sources.” Historically, the term “point sources” has meant
discharges to surface waters that typically have a continuous flow via a discernable, confined,
and discrete conveyance, such as a pipe. Domestic and industrial wastewater treatment
facilities (WWTFs) are examples of traditional point sources. In contrast, the term “nonpoint
sources” was used to describe intermittent, rainfall-driven, diffuse sources of pollution
associated with everyday human activities, including runoff from urban land uses, agriculture,
silviculture, and mining; discharges from failing septic systems; and atmospheric deposition.

However, the 1987 amendments to the Clean Water Act redefined certain nonpoint sources of
pollution as point sources subject to regulation under the EPA’s National Pollutant Discharge
Elimination System (NPDES) Program. These nonpoint sources included certain urban
stormwater discharges, including those from local government master drainage systems,
construction sites over five acres, and a wide variety of industries (see Appendix B for
background information on the federal and state stormwater programs).

To be consistent with Clean Water Act definitions, the term “point source” is used to describe
traditional point sources (such as domestic and industrial wastewater discharges) and
stormwater systems requiring an NPDES stormwater permit when allocating pollutant load
reductions required by a TMDL. However, the methodologies used to estimate nonpoint source
loads do not distinguish between NPDES stormwater discharges and non-NPDES stormwater
discharges, and as such, this source assessment section does not make any distinction
between the two types of stormwater.


4.2 Potential Sources of BOD and Low DO in the [*Moccasin Creek or Lake
    Tarpon Canal*] Watershed
4.2.1 Point Sources
Estimating Point Source Loads
There are no permitted wastewater facilities located in the either Moccasin Creek, Lake Tarpon
Canal Fresh, or Lake Tarpon Canal Marine WBIDs.




                                                 16
Florida Department of Environmental Protection
   DRAFT TMDL Report: Tampa Basin, Moccasin Creek, Lake Tarpon Canal Freshwater and Lake Tarpon
                                            Marine


Municipal Separate Storm Sewer System Permittees
Within the Moccasin Creek Tidal, Lake Tarpon Canal Marine, and Lake Tarpon Canal
Freshwater, there is the same single Phase I municipal separate storm sewer system (MS4)
permits (FLS000005, Pinellas County and co-permittees). The responsible co-permittees in
Moccasin Creek (1530) are the City of Oldsmar and Pinellas County. The responsible co-
permittees in Lake Tarpon Canal Marine (1541A) and fresh (1541B) are the City of Oldsmar and
Pinellas County.

4.2.2 Land Uses and Nonpoint Sources
In the Moccasin Creek (576 acres) Lake Tarpon Canal Marine (603 acres), and Lake Tarpon
Freshwater (814 acres), a number of land uses affect water quality through nonpoint source
runoff (Figure 4.1). The most significant nonpoint sources include runoff and erosion from
developed areas, small-scale construction, residential and commercial fertilizer use, pets,
residential septic tank failure, or poorly designed septic tanks. The watershed has a limited
amount of agriculture, with only 58 acres devoted to cropland and pasture.

Land Uses
Land use categories in the Moccasin Creek and Lake Tarpon Canal watersheds were
aggregated using the simplified Level 1 codes (Table 4.1a, 4.1b, and 4.1c). By far the largest
Level 1 land use is urban and built-up (78 percent of Moccasin Creek, 70.5% of Lake Tarpon
Canal Marine, and 61.5% of Lake Tarpon Canal Freshwater). When looking at Level 2, which is
a more detailed categorization of land use (Table 4.2a , 4.2b, and 4.2c), urban and built-up land
uses is comprised mainly of high density residential, medium density residential, low density
residential and commercial. After urban and built-up, the second largest land use category is
water and wetland.



Table 4.1a. Level 1 Land Uses in the Moccasin Creek, WBID 1530

 Landuse Code and Description (WBID 1530)                Acres      % Total
 1000: Urban and Built up                                 449.7      78.1%
 5000: Water                                               56.9       9.9%
 6000: Wetland                                             40.9       7.1%
 8000: Transportation, Communication, & Utilities          24.1       4.2%
 3000: Rangeland                                            4.4       0.8%

 Total                                                   576.0      100.0%




                                                    17
Florida Department of Environmental Protection
   DRAFT TMDL Report: Tampa Basin, Moccasin Creek, Lake Tarpon Canal Freshwater and Lake Tarpon
                                            Marine




Figure 4.1. Moccasin Creek Tidal, Lake Tarpon Canal Marine, and Lake
            Tarpon Canal Fresh Land uses.




                                                 18
Florida Department of Environmental Protection
   DRAFT TMDL Report: Tampa Basin, Moccasin Creek, Lake Tarpon Canal Freshwater and Lake Tarpon
                                            Marine


Table 4.1b. Level 1 Land Uses in the Lake Tarpon Canal Marine, WBID
          1541A
    Landuse Code and Description (WBID
                 1541A)                                  Acres      % Total
 1000: Urban and Built up                                 425.0      70.49%
 5000: Water                                               62.7      10.40%
 8000: Transportation, Communication, & Utilities          33.6       5.58%
 6000: Wetland                                             30.9       5.13%
 2000: Agriculture                                         26.0       4.31%
 4000: Upland Forests                                      24.7       4.10%

 Total                                                   602.9    100.00%


Table 4.1c. Level 1 Land Uses in the Lake Tarpon Canal Fresh, WBID
          1541B
    Landuse Code and Description (WBID
                 1541B)                                  Acres      % Total
 1000: Urban and Built up                                500.5       61.5%
 6000: Wetland                                           101.2       12.4%
 8000: Transportation, Communication, & Utilities         93.3       11.5%
 5000: Water                                              81.1       10.0%
 4000: Upland Forests                                     36.2        4.4%
 2000: Agriculture                                         2.1        0.3%

 Total                                                   814.4      100.0%


Table 4.2a. Level 2 Land Use Categories in the Gordon Moccasin Creek
          watershed, WBID 1530

 Landuse Code and Description (WBID 1530)                 Acres      % Total
 1300: Residential, High Density                            243.5      42.28%
 1200: Residential, Medium Density                           78.8      13.68%
 1900: Openland                                              47.1       8.17%
 1500: Industrial                                            39.9       6.92%
 1400: Commercial                                            33.0       5.74%
 5300: Reservoirs                                            32.7       5.67%
 6400: Vegetated Nonforested Wetlands                        32.1       5.58%
 5400: Bays and Estuaries                                    24.2       4.21%
 8100: Transportation                                        24.1       4.18%
 1700: Institutional                                          7.4       1.28%
 6300: Wetland Forest Mixed                                   5.7       0.99%
 3200: Shrub and Brushland                                    4.4       0.77%
 6100: Wetland hardwood forests                               3.1       0.53%

 Total                                                    576.0      100.00%

                                                    19
Florida Department of Environmental Protection
   DRAFT TMDL Report: Tampa Basin, Moccasin Creek, Lake Tarpon Canal Freshwater and Lake Tarpon
                                            Marine


Table 4.2b. Level 2 Land Use Categories in the Lake Tarpon Canal
          Marine (1541A) watershed.

 Landuse Code and Description (WBID 1541A)                 Acres          % Total
 1300: Residential, High Density                              181.6         30.12%
 1200: Residential, Medium Density                             85.0         14.09%
 1900: Openland                                                62.1         10.31%
 1700: Institutional                                           39.5          6.55%
 5100: Streams and Waterways                                   38.3          6.36%
 8100: Transportation                                          33.6          5.58%
 1400: Commercial                                              31.9          5.30%
 6400: Vegetated Nonforested Wetlands                             28.3       4.70%
 2100: Cropland and Pastureland                                   26.0       4.31%
 1800: Recreation                                                 24.9       4.13%
 5300: Reservoirs                                                 20.4       3.38%
 4100: Upland Coniferous                                          17.8       2.94%
 4300: Upland Mixed Forest                                         6.9       1.15%
 5400: Bays and Estuaries                                          4.0       0.66%
 6500: Non Vegetated Wetlands                                      2.6       0.43%

 Total                                                      602.9         100.00%

Table 4.c. Classification of Level 2 Land Use Categories in the Lake
           Tarpon Canal – Fresh watershed (1541B)
     Landuse Code and Description (WBID
                  1541B)                                 Acres           % Total
 1300: Residential, High Density                          344.6           42.3%
 1400: Commercial                                          72.3            8.9%
 8100: Transportation                                      52.9            6.5%
 6100: Wetland hardwood forests                            51.6            6.3%
 5100: Streams and Waterways                               49.3            6.1%
 1900: Openland                                            43.6            5.3%
 8300: Utilities                                           40.4            5.0%
 1800: Recreation                                         29.8            3.7%
 5300: Reservoirs                                         28.2            3.5%
 4100: Upland Coniferous                                  24.6            3.0%
 6300: Wetland Forest Mixed                               21.9            2.7%
 6400: Vegetated Nonforested Wetlands                     20.8            2.6%
 4300: Upland Mixed Forest                                11.5            1.4%
 1200: Residential, Medium Density                        10.3            1.3%
 6500: Non Vegetated Wetlands                              5.1            0.6%
 5200: Lakes                                               3.6            0.4%
 2600: Other Open Lands                                    2.1            0.3%
 6200: Wetland Coniferous Forests                          1.8            0.2%
 1700: Institutional                                       0.0            0.0%

 Total                                                   814.4           100.0%

                                                 20
Florida Department of Environmental Protection
    DRAFT TMDL Report: Tampa Basin, Moccasin Creek, Lake Tarpon Canal Freshwater and Lake Tarpon
                                             Marine


The primarily nonurban land uses include wetland forest (345 acres), upland coniferous (273
acres), wetland coniferous (140 acres), upland hardwood (117 acres), and upland mixed forests
(63 acres), for a total of approximately 940 acres in wetland or upland forest.

The runoff from the Moccasin Creek and Lake Tarpon Canal watershed is based on impervious
area (Harper, 2003; Duncan, 1995), as shown in Tables 4.3a, 4.3b, and 4.3c. The nutrient
contributions are determined by combining the runoff information for each land use with the
corresponding event mean concentration (EMC) (Tables 4.4a, 4.4b, and 4.4c). These tables
show that the top three land use contributors of TN are commercial, medium-density residential,
and industrial, in order of decreasing contribution.

Table 4.3a. Moccasin Creek Land Use Categories and Corresponding
          Runoff, 2000–07
                                                                          Impervious Pervious              Avg      Runoff Runoff
                                          Area     Percent                  Runoff    Runoff              Precip.   (Acre- Million
        Land Use                         (acres) Impervious                 Coeff.    Coeff.               "/yr      feet)  Gallons
A. Forest/Rural Open                       51.51     27.0%                      0.95    0.159              49.43       79.0    25.7
B. Urban Open                              24.07       0.4%                     0.95    0.041              49.43        4.5      1.5
C. Agriculture/Pasture                       0.00      1.1%                     0.95    0.317              49.43        0.0      0.0
D. Low
Density/Residential                           0.00              5.3%                0.95          0.150    49.43       0.0      0.0
E. Medium
Density/Residential                          78.82            24.8%                 0.95          0.088    49.43      98.0     31.9
F. High
Density/Residential                        243.52              7.3%                 0.95          0.120    49.43     181.4      59.1
G. Commercial                               40.40             10.5%                 0.95          0.120    49.43      34.5      11.3
H. Industrial                               39.86              7.7%                 0.95          0.120    49.43      30.2       9.8
I. Highways                                  0.00              2.6%                 0.95          0.542    49.43       0.0       0.0
J. Wetland                                  40.91              9.4%                 0.95          0.230    49.43      50.2      16.4
K. Water                                    56.90              3.8%                 0.95          0.000    49.43       8.4       2.7
Other 2                                                                                                                0.0       0.0
Total                                      575.98                                                                   486.16     158.4
Note: Based on effective rainfall of 55.95 inches per year. All impervious R.O. coefficients are 0.95.




                                                                  21
Florida Department of Environmental Protection
            DRAFT TMDL Report: Tampa Basin, Moccasin Creek, Lake Tarpon Canal Freshwater and Lake Tarpon
                                                     Marine


      Table 4.3b. Tarpon Lake Canal Marine Land Use Categories and
                Corresponding Runoff, 2000–07

                                                                             Impervious       Pervious           Avg        Runoff Runoff
                                           Area     Percent                    Runoff          Runoff           Precip.     (Acre- Million
          Land Use                        (acres) Impervious                   Coeff.          Coeff.            "/yr        feet)  Gallons
A. Forest/Rural Open                       111.71     27.0%                        0.95          0.159            49.43       171.3    55.8
B. Urban Open                               33.62       0.4%                       0.95          0.041            49.43         6.3      2.0
C. Agriculture/Pasture                      25.98       1.1%                       0.95          0.317            49.43        34.7    11.3
D. Low Density/Residential                    0.00      5.3%                       0.95          0.150            49.43         0.0      0.0
E. Medium
Density/Residential                          84.97             24.8%                 0.95          0.088          49.43      105.6      34.4
F. High Density/Residential                 181.61              7.3%                 0.95          0.120          49.43      135.3      44.1
G. Commercial                                71.41             10.5%                 0.95          0.120          49.43       61.0      19.9
H. Industrial                                 0.00              7.7%                 0.95          0.120          49.43        0.0       0.0
I. Highways                                   0.00              2.6%                 0.95          0.542          49.43        0.0       0.0
J. Wetland                                   30.94              9.4%                 0.95          0.230          49.43       38.0      12.4
K. Water                                     62.69              3.8%                 0.95          0.000          49.43        9.2       3.0
Other 2                                                                                                                                  0.0
Total                                       602.93                                                                          561.39     182.9
      Note: Based on effective rainfall of 55.95 inches per year. All impervious R.O. coefficients are 0.95.


      Table 4.3c. Tarpon Lake Canal Fresh Use Categories and Corresponding
                Runoff, 2000–07

                                                                                 Impervious Pervious               Avg       Runoff Runoff
                                                 Area     Percent                  Runoff    Runoff               Precip.    (Acre- Million
                  Land Use                      (acres) Impervious                 Coeff.    Coeff.                "/yr       feet)  Gallons
          A. Forest/Rural Open                   109.48     27.0%                      0.95    0.159                49.43     167.9     54.7
          B. Urban Open                           93.31       0.4%                     0.95    0.041                49.43       17.4      5.7
          C. Agriculture/Pasture                   2.10       1.1%                     0.95    0.317                49.43        2.8      0.9
          D. Low
          Density/Residential                        0.00              5.3%               0.95          0.150       49.43        0.0      0.0
          E. Medium
          Density/Residential                      10.34             24.8%                0.95          0.088       49.43       12.9      4.2
          F. High
          Density/Residential                     344.60              7.3%                0.95          0.120       49.43     256.7      83.7
          G. Commercial                            72.26             10.5%                0.95          0.120       49.43      61.8      20.1
          H. Industrial                             0.00              7.7%                0.95          0.120       49.43       0.0       0.0
          I. Highways                               0.00              2.6%                0.95          0.542       49.43       0.0       0.0
          J. Wetland                              101.25              9.4%                0.95          0.230       49.43     124.3      40.5
          K. Water                                 81.09              3.8%                0.95          0.000       49.43      11.9       3.9
          Other 2                                                                                                               0.0       0.0
          Total                                   814.42                                                                     655.64     213.6
      Note: Based on effective rainfall of 55.95 inches per year. All impervious R.O. coefficients are 0.95.



                                                                        22
      Florida Department of Environmental Protection
          DRAFT TMDL Report: Tampa Basin, Moccasin Creek, Lake Tarpon Canal Freshwater and Lake Tarpon
                                                   Marine


       Table 4.4a. Moccasin Creek Land Use Categories and Corresponding EMC
                 Contributions Based on 2000–07 Rainfall
                                                                                             Expressed   Expressed
                                                                                              as % of     as % of
                                         TN                  TP                               Total TN    Total TP
                                    Concentration       Concentration    TN load   TP load   Watershed   Watershed
           Land Use                    (mg/L)              (mg/L)         (lbs)     (lbs)      Load        Load
A. Forest/Rural Open                     1.09              0.046         234.1       9.9        897.3%      222.7%
B. Urban Open                            1.12               0.18         13.7        2.2         52.4%       49.6%
C. Agriculture/Pasture                   2.32               0.344         0.0        0.0          0.0%        0.0%
D. Low Density/Residential               1.64               0.191         0.0        0.0          0.0%        0.0%
E. Medium
Density/Residential                      2.18               0.335        580.7       89.2     2225.6%     2011.5%
F. High Density/Residential              2.42               0.49        1,194.0     241.8     4576.1%     5449.6%
G. Commercial                            2.42               0.49         227.3       46.0      871.0%     1037.2%
H. Industrial                            2.42               0.49         198.6       40.2      761.0%      906.3%
I. Highways                              2.23               0.27           0.0       0.0         0.0%        0.0%
J. Wetland                               1.01               0.09         137.9       12.3      528.5%      277.0%
K. Water                                 1.01               0.09          23.0       2.0        88.0%       46.1%


             Total                       0.00               0.00        2,609.3     443.6      0.0%        0.0%

       Table 4.4b. Lake Tarpon Canal Marine Land Use Categories and
                 Corresponding EMC Contributions Based on 2000–07 Rainfall
                                                                                             Expressed   Expressed
                                                                                              as % of     as % of
                                        TN               TP                                   Total TN    Total TP
                                   Concentration    Concentration       TN load    TP load   Watershed   Watershed
          Land Use                    (mg/L)           (mg/L)            (lbs)      (lbs)      Load        Load
A. Forest/Rural Open                   1.09               0.046         507.7       21.4          18.2         5.0
B. Urban Open                           1.12               0.18         19.1        3.1            0.7         0.7
C. Agriculture/Pasture                  2.32               0.344        218.8       32.4           7.8         7.6
D. Low Density/Residential              1.64               0.191         0.0        0.0            0.0         0.0
E. Medium
Density/Residential                     2.18               0.335        626.0       96.2          22.4        22.6
F. High Density/Residential             2.42               0.49         890.5      180.3          31.9        42.3
G. Commercial                           2.42               0.49         401.7       81.3          14.4        19.1
H. Industrial                           2.42               0.49          0.0        0.0            0.0         0.0
I. Highways                             2.23               0.27          0.0        0.0            0.0         0.0
J. Wetland                              1.01               0.09         104.3       9.3            3.7         2.2
K. Water                                1.01               0.09         25.3        2.3            0.9         0.5


            Total                      0.00                0.00         2,793.4    426.3      100.0       100.0



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       Florida Department of Environmental Protection
          DRAFT TMDL Report: Tampa Basin, Moccasin Creek, Lake Tarpon Canal Freshwater and Lake Tarpon
                                                   Marine


       Table 4.4c Tarpon Lake canal Fresh Land Use Categories and
                 Corresponding EMC Contributions Based on 2000–07 Rainfall
                                                                                        Expressed   Expressed
                                                                                         as % of     as % of
                                        TN               TP                              Total TN    Total TP
                                   Concentration    Concentration   TN load   TP load   Watershed   Watershed
          Land Use                    (mg/L)           (mg/L)        (lbs)     (lbs)      Load        Load
A. Forest/Rural Open                   1.09             0.046       497.5      21.0     1597.4%       418.6%
B. Urban Open                           1.12            0.18        53.1       8.5       170.4%       170.0%
C. Agriculture/Pasture                  2.32            0.344       17.7       2.6        56.8%        52.3%
D. Low Density/Residential              1.64            0.191        0.0       0.0         0.0%         0.0%
E. Medium
Density/Residential                     2.18            0.335         76.2     11.7      244.6%      233.4%
F. High Density/Residential             2.42            0.49        1,689.6   342.1     5424.8%     6820.3%
G. Commercial                           2.42            0.49         406.5     82.3     1305.2%     1641.0%
H. Industrial                           2.42            0.49           0.0     0.0         0.0%        0.0%
I. Highways                             2.23            0.27           0.0     0.0         0.0%        0.0%
J. Wetland                              1.01            0.09         341.3     30.4     1095.8%      606.3%
K. Water                                1.01            0.09          32.7     2.9       105.1%       58.1%


            Total                      0.00             0.00        3,114.7   501.6       0.0%        0.0%




                                                               24
       Florida Department of Environmental Protection
             DRAFT TMDL Report: Tampa Basin, Moccasin Creek, Lake Tarpon Canal Freshwater and Lake Tarpon
                                                      Marine


         Chapter 5: DETERMINATION OF ASSIMILATIVE
         CAPACITY

         5.1 Determination of Loading Capacity
         The TMDL development process identifies pollutant target concentrations and pollutant
         reductions for Mocassin Creek, Lake Tarpon Canal Marine, and Lake Tarpon Canal Freshwater
         for these waterbodies to achieve the applicable DO and nutrient water quality criteria, and
         maintain their function and designated use as a Class 3M (Marine) or Class 3F (Fresh) water.
         The targets were developed based on an analysis of nutrient data for streams or estuaries in the
         Tampa Bay watershed that are not impaired for DO and nutrients, as described in Chapter 3.
         The TMDLs were established using a percent reduction approach in existing nutrient
         concentrations to meet the water quality targets, based on data collected in the Cycle 2 verified
         period.
         The goal of this TMDL analysis is to reduce the anthropogenic TN loads to conditions
         comparable to those found in surrounding, unimpaired watersheds. The methodology used is a
         percent reduction approach between the existing condition concentration and the region-based
         reference concentration.


         5.2 Data Used in the Determination of the TMDL
         The stations located in the Moccasin Creek (1530), Lake Tarpon Canal Freshwater (1541B),
         and Lake Tarpon Canal Marine (1541A) have DO and TN observations. Data providers include
         the Department, Pinellas County, and SWFWMD, which maintains a routine sampling site.
         Tables 5.1a, 5.1b, and 5.1c show verified period sample analyses summaries for the major
         sample stations in the WBIDs. Figure 5.1 shows the locations of the WBID’s major ambient
         water sample sites.


         Table 5.1a. Data Collectors and Station List for the Moccasin Creek
  Station ID                      Station Name                            Total Nitrogen Summary                         D.O.
                                                                         Count Median        75                Count   Median      75
                                                                                          Percentile                            Percentile


21FLPDEMAMB
05-1                Moccasin Creek, West Branch                               19       1.13            1.225     22     3.695       4.685
21FLPDEMAMB
05-2                Moccasin Creek, East Branch                               16       1.13             1.34     18     4.565      5.3075
21FLTPA
28020958240534      TP360-Moccasin Creek                                       8     1.262             1.453     16       3.4       7.705
21FLTPA
2821288240456       TP361-Moccasin Creek                                       7     1.126         1.5185        15       3.3        5.78
                    1530 - Moccasin Creek Tidal - at bridge
21FLBRA 1530-A      on Forest Lake Blvd                                        1     0.604             0.604
         Note: Total number of samples includes data for all parameters assessed in verified period.




                                                                         25
         Florida Department of Environmental Protection
              DRAFT TMDL Report: Tampa Basin, Moccasin Creek, Lake Tarpon Canal Freshwater and Lake Tarpon
                                                       Marine


        Table 5.1b. Station List for the Lake Tarpon Canal Marine
   Station ID                   Station Name                 Total Nitrogen Summary                     D.O.
                                                            Count Median        75           Count    Median       75
                                                                             Percentile                         Percentile

21FLTPA
28025538242267        TP389-Lake Tarpon Canal                    22    1.108      1.2185        22     5.745       7.3725



        Table 5.1c. Station List for the Lake Tarpon Canal Fresh
 Station ID                   Station Name                      Total Nitrogen Summary                  D.O.
                                                               Count Median        75        Count    Median        75
                                                                                Percentile                       Percentile

21FLPDEM06-
04               Lake Tarpon Outfall Structure                    36      0.94       1.17        38      5.41        6.715
21FLPDEMAMB
06-4             Lake Tarpon Outfall Canal                        32    0.985      1.1825        37      4.54         7.22
112WRD           LAKE TARPON CANAL AT S-551, NR
02307498         OLDSMAR, FLA.                                     7      1.12       1.22        15       4.6         5.25




                                                          26
        Florida Department of Environmental Protection
   DRAFT TMDL Report: Tampa Basin, Moccasin Creek, Lake Tarpon Canal Freshwater and Lake Tarpon
                                            Marine




Note: FDOT Local Roads are for illustration and not meant to be a depiction of all FDOT local roads.

Figure 5.1. Major Sample Stations for Moccasin Creek and Lake Tarpon
            Canal Watersheds.



                                                   27
Florida Department of Environmental Protection
   DRAFT TMDL Report: Tampa Basin, Moccasin Creek, Lake Tarpon Canal Freshwater and Lake Tarpon
                                            Marine


The approach to calculating DO and nutrient TMDLs depends on the number of water quality
samples and the availability of other required datasets. When minimal or no nutrient, BOD, or
flow data are available, the existing loads are calculated using the nonpoint source spreadsheet
and the TMDL is expressed as a percent reduction to meet a pollutant concentration target
based on natural or reference conditions (EPA, 2000). The assumption is that BOD and
nutrients (primarily TN and TP) are the major controllable factors for DO. To return DO
concentrations to a “naturally” expected condition, unimpaired by pollutants, BOD and nutrient
loadings also need to be returned to near natural loading conditions.

DO can also be affected or lowered by in-stream modifications such as dredging and
channelization. These processes slow down water velocity, reduce reaeration, and increase the
settling of solids, thus increasing sediment oxygen demand (SOD) and lowering DO
concentrations. Further analyses and monitoring must be completed to develop an appropriate,
site-specific DO criterion.

Having determined the TN level that meets the Chla limits for Old Tampa Bay, the approach
used here was to obtain percent reductions by determining those areas within the Tampa Bay
Basin meeting nutrient and dissolved oxygen standards for Class 3 Marine and Fresh Waters,
and to utilize those concentrations as a target to meet the more difficult to attain dissolved
oxygen levels. The median target concentration is, from Table 3.3, for N.I. Marine waters in
Tampa Bay Tributaries a TN=0.62 mg/L, TP=0.18 mg/L, and BOD5=1.5 mg/L. For Fresh water
the limit is TN=0.97 mg/L, TP=0.202 mg/L, and BOD5=1.6 mg/L. Because Lake Tarpon Canal
Fresh is directly upstream of Lake Tarpon Canal Marine, and the Marine targets are greaterless
than the fresh, Lake Tarpon Canal Fresh Canal Fresh is consistent will adopt the standards of
Lake Tarpon Canal Marine to provide a level of assurance that Lake Tarpon Canal Marine can
meet its target. Because, for Mocassin Creek and Lake Tarpon Canals, these waterbodies
either have median TP concentrations the Tampa Bay Tributaries contact many stations in the
Bone Valley Basin with traditionally higher TP, the Tampa Bay NI data will not be averaged with
the Tampa Bay Tributary data to obtain a TP target (as was done with the TN target). Note that
the Lake Tarpon Canal Fresh TP concentration is below the reference or the TN/TP ratios
indicate a nitrogen limited system andproposed target, thus do not warrant TP reductions.no
TMDL would be required. Because the measured BOD has multiple 2.0 values, same as
laboratory detection limits, there will be no BOD TMDL until there is a further review of data.


5.3 TMDL Development Process
The concentration marked for reduction was determined to be the highest annual average
station median measured during the Verified Period. To be included in the WBID annual
median station concentration calculations, the station must have at least one sample taken
during each of the four seasons. The concentration targeted as meeting the goals of this TMDL
was determined by the process described in Chapter 3 for Target Concentration. The
percentage reduction was calculated using the target concentrations described in Chapter 3 and
the highest annual median sample station TN concentration. The below equation, utilizing the
concentration marked for reduction and the TMDL target concentration, is used to calculate the
percent reduction:strategy for the goal in total nitrogen reduction is to have the maximum
sample station median TN concentration observed during the verified period reduced to a level
where it has been demonstrated to be at a median TN (and corresponding DO) which has been
shown to meet Florida criteria. The reduction was thus calculated as follows;

        [(Concentration Marked for Reduction) – (TMDL Target Concentration)]
                                                 28
Florida Department of Environmental Protection
   DRAFT TMDL Report: Tampa Basin, Moccasin Creek, Lake Tarpon Canal Freshwater and Lake Tarpon
                                            Marine


        ---------------------------------------------------------------------------------------------------------- X 100
                                    (Concentration Marked for Reduction)

                              [(Max Observed TN) – (water quality target)]
                            -------------------------------------------------------------------   X    100
                                                (Max Observed TN)

      Where Max Observed TN = Maximum Verified Period Sample Station Median Annual TN Concentration

Tables 5.2a, 5.2b, and 5.2c

Table 5.2 shows the results of the equation applied to Moccasin Creek, Lake Tarpon Canal
Marine, and Lake Tarpon Canal Freshwater.




                                                           29
Florida Department of Environmental Protection
                                DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),



         Table 5.2. Moccasin Creek, Lake Tarpon Marine and Fresh TN Percent Reduction Table, 2000–07

                                    Total Nitrogen Highest Annual Average Calculation                                    Surface     Target     Required
            WBID                                                                                                          Water   Concentration Percent
                                                                         Station        WBID           Target = Maximum Body Type  (Chapter 3) Reduction
 No                                                                                                       N.I. Annual
                 Name                Station with at least 1             Annual         Annual                              &
                                                                                                            Median
                                  Sample Every Season of Year Year       Median         Median                            Class
1530                                                                                                                    ESTUARY
                                  21FLPDEMAMB 05-1              2000             0.81                                                 0.97       39.4%
                                                                                                                           3M
                                  21FLPDEMAMB 05-2              2000             1.09           0.95
                                  21FLPDEMAMB 05-1              2001             1.19
        MOCCASIN CREEK TIDAL 21FLPDEMAMB 05-2                   2001             1.15           1.17         1.60
                                  21FLPDEM05-05                 2003             1.60           1.60
                                  21FLTPA 28020958240534        2005             1.26
                                  21FLTPA 2821288240456         2005             1.13
                                  21FLTPA 2824878241307         2005             2.36           1.26
1541A                                                                                                                   ESTUARY
         LAKE TARPON CANAL        21FLTPA 28025538242267       2005       1.11           1.11                1.11                     0.97       12.6%
                                                                                                                           3M
1541B                                                                                                                   STREAM
                                  21FLPDEMAMB 06-4              2000             0.95           0.95                                  0.87       25.6%
                                                                                                                           3F
                                  21FLPDEMAMB 06-4              2001             0.94           0.94
                                  21FLPDEMAMB 06-4              2002             1.17           1.17
         LAKE TARPON CANAL
                                  21FLPDEM06-04                 2003             0.93           0.93         1.17
                                  21FLPDEM06-04                 2004             1.00           1.00
                                  21FLPDEM06-04                 2005             1.07           1.07
                                  21FLPDEM06-04                 2006             0.92           0.92




                                                                                 30
         Florida Department of Environmental Protection
                       DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),



Table 5.2a.Moccasin Creek TN Percent Reduction Table, 2000–07
               Major Sample Stations         VP                Sample Station Median Annual Total Nitrogen Concentration        Verified
                during verified period     Sample                                                                               Period
               for MOCCASIN CREEK
                                                             2000   2001     2002   2003    2004      2005   2006     2007     Maximum
                                           Count
                 TIDAL, WBID 1530                                                                                               Annual
                                                                                                                                Median
            21FLPDEMAMB 05-1                          19      0.81    1.19                                                           1.19
            21FLPDEMAMB 05-2                          16      1.09    1.15    1.11                                                   1.15
            21FLTPA
            28020958240534                             8                                              1.26                           1.26
            21FLTPA
            2821288240456                              7                                              1.13                           1.13
                    Worst Year Median TN to for which reduction is to be applied to (Maximum Annual Station median)                  1.26
                                                                                       Target Concentration (mg/L)                   0.75
                                                                                                        Percent Reduction          40.6%
Table 5.2b. Lake Tarpon Canal Marine TN Percent Reduction Table, 2000–07
            Major Sample Stations          VP                Sample Station Median Annual Total Nitrogen Concentration        Verified
             during verified period      Sample                                                                               Period
          for LAKE TARPON CANAL,
                                                           2000   2001     2002   2003    2004      2005   2006     2007
                                         Count                                                                               Maximum
                 WBID 1541A
          21FLTPA
          28025538242267                         22                                                 1.11                           1.11

                                                                                            Target Concentration (mg/L)            0.75
                                                                                                     Percent Reduction           32.3%
Table 5.2b. Lake Tarpon Canal Fresh TN Percent Reduction Table, 2000–07
             Major Sample Stations          VP               Sample Station Median Annual Total Nitrogen Concentration        Verified
              during verified period      Sample                                                                              Period
           for LAKE TARPON CANAL,
                                                           2000   2001     2002   2003    2004      2005   2006     2007
                                          Count                                                                              Maximum
                  WBID 1541B
           21FLPDEM06-04                         36                                  0.93    1.00    1.07    0.92                   1.07
           21FLPDEMAMB 06-4                      32          0.95    0.94    1.17                                                   1.17
              Worst Year Median TN to for which reduction is to be applied to (Maximum Annual Station median)                       1.17
                                                                                    Target Concentration (mg/L)                     0.75
                                                                                                      Percent Reduction           35.9%
                                                                               31
Florida Department of Environmental Protection
             DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),



          Table 5.3a. Moccasin Creek TP Percent Reduction Table
   Major Sample Stations                   Sample Station Median Annual Total Nitrogen Concentration                  Verified
    during verified period                                                                                            Period
                                2000       2001      2002      2003      2004        2005     2006        2007
   for MOCCASIN CREEK                                                                                                Maximum
     TIDAL, WBID 1530

21FLPDEMAMB 05-1            0.27        0.23                                                                             0.27
21FLPDEMAMB 05-2            0.24        0.22                                                                             0.24
21FLTPA
28020958240534                                                           0.25                                            0.25
21FLTPA
2821288240456                                                            0.30                                              0.3
            Worst Year Median TN to for which reduction is to be applied to (Maximum Annual Station median)                0.3

                                                                                    Target Concentration (mg/L)           0.18
                                                                                             Percent Reduction          40.0%




          Table 5.3b. Lake Tarpon Canal Marine TP Percent Reduction Table
  Major Sample Stations                  Sample Station Median Annual Total Nitrogen Concentration                   Verified
   during verified period                                                                                            Period
                              2000       2001      2002      2003      2004        2005     2006         2007
for LAKE TARPON CANAL,                                                                                              Maximum
       WBID 1541A

21FLTPA
28025538242267                   0.00        0.00          0.00       0.00   0.25      0.00                     0      0.245

                                                                                    Target Concentration (mg/L)          0.18
                                                                                             Percent Reduction         26.5%




                                                                  0
          Florida Department of Environmental Protection
  DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),




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. A TMDL is expressed as the sum of all
point source loads (wasteload allocations, or WLAs), nonpoint source loads (load allocations, or
LAs), and an appropriate margin of safety (MOS), which takes into account any uncertainty
concerning the relationship between effluent limitations and water quality:

TMDL = ∑ WLAs + ∑ LAs + MOS

As discussed earlier, the WLA is broken out into separate subcategories for wastewater
discharges and stormwater discharges regulated under the NPDES Program:

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

It should be noted that the various components of the revised TMDL equation may not sum up
to the value of the TMDL because (a) the WLA for NPDES stormwater is typically based on the
percent reduction needed for nonpoint sources and is also accounted for within the LA, and (b)
TMDL components can be expressed in different terms (for example, the WLA for stormwater is
typically expressed as a percent reduction, and the WLA for wastewater is typically expressed
as mass per day).

WLAs for stormwater discharges are typically expressed as “percent reduction” because it is
very difficult to quantify the loads from MS4s (given the numerous discharge points) and to
distinguish loads from MS4s from other nonpoint sources (given the nature of stormwater
transport). The permitting of stormwater discharges also differs from the permitting of most
wastewater point sources. Because stormwater discharges cannot be centrally collected,
monitored, and treated, they are not subject to the same types of effluent limitations as
wastewater facilities, and instead are required to meet a performance standard of providing
treatment to the “maximum extent practical” through the implementation of best management
practices (BMPs).

This approach is consistent with federal regulations (40 CFR § 130.2[I]), which state that TMDLs
can be expressed in terms of mass per time (e.g., pounds per day), toxicity, or other
appropriate measure. The TMDLs for Moccasin Creek and or Lake Tarpon Canal Marine and
Lake Tarpon Canal Fresh is expressed in terms of a percent reductions in TN and TP to protect
the DO concentration (Table 6.1).




                                                 1
Florida Department of Environmental Protection
  DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),



Table 6.1. TMDL Components and Current Loadings for the Moccasin Creek
           (WBID 1530) and Lake Tarpon Canal (WBIDs 1541A and 1541B)
       N/A – Not applicable.

                                                           WLA
                                  TMDL                                            LA
         WBID        Parameter                                  NPDES                         MOS
                                  (mg/L)     Wastewater                      (% reduction)
                                                              Stormwater
                                               (mg/L)
                                                             (% reduction)
       Moccasin
        Creek             TN       0.97          N/A             39.4            39.4        Implicit
        (1530)
         Lake
        Tarpon
        Canal             TN       0.97          N/A             12.5            12.6        Implicit
        Marine
       (1541A)
         Lake
        Tarpon
        Canal             TN       0.87          N/A             25.6            25.6        Implicit
        Fresh
       (1541B)


                                                           WLA
                                  TMDL                                            LA
         WBID        Parameter                                  NPDES                         MOS
                                  (mg/L)     Wastewater                      (% reduction)
                                                              Stormwater
                                               (mg/L)
                                                             (% reduction)

                          TN       0.75          N/A             40.6%          40.6%        Implicit
       Moccasin
        Creek
        (1530)
                          TP       0.18          N/A             40%             40%         Implicit


          Lake            TN       0.75          N/A             32.3%          32.2%        Implicit
         Tarpon
         Canal
         Marine
        (1541A)           TP       0.18          N/A             26.5%          26.5%        Implicit

          Lake
         Tarpon
         Canal            TN       0.75          N/A             47%            35.9%        Implicit
         Fresh
        (1541B)



6.2 Wasteload Allocation
6.2.1 NPDES Wastewater Discharges
There are currently no wastewater facilities in the Moccasin Creek or Lake Tarpon Canal
watershed.




                                                       2
Florida Department of Environmental Protection
  DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),



6.2.2 NPDES Stormwater Discharges
The WLAs for stormwater discharges with an MS4 permit (FLS000005, Pinellas County and co-
permittees) is a 39.4%50.9% reduction in TN for Moccasin Creek, 12.6%44% reduction in TN
for Lake Tarpon Canal Marine, and a 25.6%47% reduction in TN for Lake Tarpon Canal fresh.
For Total phosphorus reductions, there is a 40% reduction in Moccasin Creek and a 26.5%
reduction in Lake Tarpon Canal Marine. It should be noted that any MS4 permittee is only
responsible for reducing the anthropogenic loads associated with stormwater outfalls that it
owns or otherwise has responsible control over, and it is not responsible for reducing other
nonpoint source loads in its jurisdiction. The responsible co-permittes in Moccasin Creek (1530)
are the City of Oldsmar and Pinellas County. The responsible co-permittees in Lake Tarpon
Canal Marine (1541A)and fresh (1541B) are the City of Oldsmar and Pinellas County.


6.3 Load Allocation
The Load allocation for nonpoint sources is a 39.4%50.9% reduction in TN for Moccasin Creek,
12.6%44% reduction in TN for Lake Tarpon Canal Marine, and a 25.6%47% reduction in TN for
Lake Tarpon Canal fresh. For Total phosphorus reductions, there is a 40% reduction in
Moccasin Creek and a 26.5% reduction in Lake Tarpon Canal Marine.


6.4 Margin of Safety
Consistent with the recommendations of the Allocation Technical Advisory Committee
(Department, 2001), an implicit MOS was used in the development of this TMDL. An implicit
MOS was provided by the conservative decisions associated with a number of modeling
assumptions, the development of site-specific alternative water quality targets, and the
development of assimilative capacity. An implicit MOS was used by targeting a loading based
on reference waterbodies.




                                                 3
Florida Department of Environmental Protection
    DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),




Chapter 7: TMDL IMPLEMENTATION

7.1 Basin Management Action Plan7 TMDL Implementation
Following the adoption of these TMDLsthis TMDL by rule, the Department will determine the
best course of action regarding theirits implementation. Depending upon the pollutant(s)
causing the waterbody impairment and the significance of the waterbody, the Department will
select the best course of action leading to the development of a plan to restore the waterbody.
Often this will be accomplished cooperatively with stakeholders by creating a Basin
Management Action Plan, referred to as the BMAP. BMAPs Basin Management Action Plans
are the primary mechanism through which TMDLs are implemented in Florida (see[see
Subsection 403.067[7],403.067(7) F.S.).F.S.]. A single BMAP may provide the conceptual plan
for the restoration of one or many impaired waterbodies.

If the Department determines that a BMAP is needed to support the implementation of these
TMDLs,this TMDL, a BMAP will be developed through a transparent, stakeholder-driven
process intended to result in a plan that is cost-effective, technically feasible, and meets the
restoration needs of the applicable waterbodies. Once adopted by order of the Department
Secretary, BMAPs are enforceable through wastewater and municipal stormwater permits for
point sources and through BMP implementation for nonpoint sources. Among other
components, BMAPs typically include the following::

•    Water quality goals (based directly on the TMDLs);TMDL);
•    Refined source identification;
•    Load reduction requirements for stakeholders (quantitative detailed allocations, if technically
     feasible);
•    A description of the load reduction activities to be undertaken, including structural projects,
     nonstructural BMPs, and public education and outreach;
•    A description of further research, data collection, or source identification needed in order to
     achieve the TMDLs;TMDL;
•    Timetables for implementation;
•    Implementation funding mechanisms;
•    An evaluation of future increases in pollutant loading due to population growth;
•    Implementation milestones, project tracking, water quality monitoring, and adaptive
     management procedures; and
•    Stakeholder statements of commitment (typically a local government resolution).

BMAPs are updated through annual meetings and may be officially revised every five years.
Completed BMAPs in the state have improved communication and cooperation among local
stakeholders and state agencies;agencies, improved internal communication within local
governments;governments, applied high-quality science and local information in managing
water resources;resources, clarified the obligations of wastewater point source, MS4, and non-
MS4 stakeholders in TMDL implementation;implementation, enhanced transparency in the


                                                   4
Florida Department of Environmental Protection
  DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),



Department’sDEP decision making;-making, and built strong relationships between the
DepartmentDEP and local stakeholders that have benefited other program areas.


7.2 Other TMDL Implementation Tools
However, in some basins, and for some parameters, particularly those with fecal coliform
impairments, the development of a BMAP using the process described above will not be the
most efficient way to restore a waterbody, such that it meets its designated uses. This is
because fecal coliform impairments result from the cumulative effects of a multitude of potential
sources, both natural and anthropogenic. Addressing these problems requires good old-
fashioned detective work that is best done by those in the area.

A multitude of assessment tools is available to assist local governments and interested
stakeholders in this detective work. The tools range from the simple (such as Walk the WBIDs
and GIS mapping) to the complex (such as bacteria source tracking). Department staff will
provide technical assistance, guidance, and oversight of local efforts to identify and minimize
fecal coliform sources of pollution. Based on work in the Lower St Johns River tributaries and
the Hillsborough Basin, the Department and local stakeholders have developed a logical
process and tools to serve as a foundation for this detective work. In the near future, the
Department will be releasing these tools to assist local stakeholders with the development of
local implementation plans to address fecal coliform impairments. In such cases, the
Department will rely on these local initiatives as a more cost-effective and simplified approach to
identify the actions needed to put in place a road map for restoration activities, while still
meeting the requirements of Subsection 403.067(7), F.S.




                                                 5
Florida Department of Environmental Protection
  DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),




References
Duncan, H. 1995. Urban stormwater pollutant concentrations and loads, Chapter 3. Australian
   Runoff Quality Institution of Engineers, Australia's National Committee on Water
   Engineering.

Florida Administrative Code. Rule 62-302, Surface water quality standards.

———. Rule 62-303, Identification of impaired surface waters.

Florida Department of Environmental Protection. February 1, 2001. A report to the Governor
     and the Legislature on the allocation of total maximum daily loads in Florida. Tallahassee,
     Florida: Bureau of Watershed Management, Division of Water Resource Management.

Harper, H. 2003. Evaluation of alternative stormwater regulations for southwest Florida: Draft
    final report (Table 26: Summary of literature-based runoff concentrations for selected land
    use categories in southwest Florida). Water Enhancement & Restoration Coalition, Inc.

U.S. Environmental Protection Agency. 2000. Ambient water quality criteria recommendations:
    Information supporting the development of state and tribal nutrient criteria for rivers and
    streams in Nutrient Ecoregion III. EPA 822-B-00-016. Washington, D.C.

U.S. Environmental Protection Agency. 1999. Protocol for Developing Nutrient TMDLs. EPA
841-B-99-007. Washington, DC: Office of Water.




                                                 6
Florida Department of Environmental Protection
  DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),




Appendices

Appendix A: Sample Stations and Median Concentration Data

Table A.1. Freshwater Sample Stations in the Southwest Coast Planning
           Unit Used in the TN–DO Correlation
                                                                    DO       TN
      WBID              Station             Latitude   Longitude                     Observations
                                                                   Median   Median
     3278G         21FLSFWMBC12            26.00883    -81.45811    5.44    0.240        59
     3278G         21FLSFWMBC18            25.91867    -81.39096     3      0.610        60
     3278G         21FLSFWMBC19            25.92696    -81.41765    3.13    0.810        59
     3278G         21FLSFWMBC21            25.96047    -81.50022    4.24    0.800        59
     3278G      21FLSFWMCHKMATE            26.14361    -81.38929    1.71    0.830        15
     3278H     21FLFTM 28030070FTM         26.29331    -81.52947    6.8     0.695         3
     3278H       21FLSFWMFAKA858           26.29288    -81.52964    4.96    0.750        56
      3278I        21FLSFWMBC10            26.10314    -81.05234    6.82    0.370        57
      3278I        21FLSFWMBC20            25.96104    -81.51664    4.11    0.650        59
      3278I         21FLSFWMBC7            25.99276    -81.52181   7.525    0.435        58
      3278I         21FLSFWMBC8            25.99330    -81.49038    7.18    0.365        60
      3278I         21FLSFWMBC9            26.15317    -81.55526    5.1     0.500        57
      3278I        21FLSFWMFAKA            25.96051    -81.50951   6.755    0.380        58
      3278V        21FLSFWMBC22            26.05711    -81.68396    6.18    0.640        57




                                                       7
Florida Department of Environmental Protection
  DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),



Appendix B: Background Information on Federal and State Stormwater Programs
In 1982, Florida became the first state in the country to implement statewide regulations to
address the issue of nonpoint source pollution by requiring new development and
redevelopment to treat stormwater before it is discharged. The Stormwater Rule, as authorized
in Chapter 403, F.S., was established as a technology-based program that relies on the
implementation of BMPs that are designed to achieve a specific level of treatment (i.e.,
performance standards) as set forth in Rule 62-40, F.A.C.

The rule requires the state’s water management districts to establish stormwater pollutant load
reduction goals (PLRGs) and adopt them as part of a Surface Water Improvement and
Management (SWIM) plan, other watershed plan, or rule. Stormwater PLRGs are a major
component of the load allocation part of a TMDL. To date, stormwater PLRGs have been
established for Tampa Bay, Lake Thonotosassa, the Winter Haven Chain of Lakes, the
Everglades, Lake Okeechobee, and Lake Apopka. No PLRG had been developed for Newnans
Lake at the time this analysis was conducted.

In 1987, the U.S. Congress established Section 402(p) as part of the federal Clean Water Act
Reauthorization. This section of the law amended the scope of the federal NPDES stormwater
permitting program to designate certain stormwater discharges as “point sources” of pollution.
These stormwater discharges include certain discharges that are associated with industrial
activities designated by specific standard industrial classification (SIC) codes, construction sites
disturbing 5 or more acres of land, and master drainage systems of local governments with a
population above 100,000, which are better known as MS4s. However, because the master
drainage systems of most local governments in Florida are interconnected, the EPA has
implemented Phase 1 of the MS4 permitting program on a countywide basis, which brings in all
cities (incorporated areas), Chapter 298 urban water control districts, and Florida Department of
Transportation (FDOT) throughout the 15 counties meeting the population criteria.

An important difference between the federal and state stormwater permitting programs is that
the federal program covers both new and existing discharges, while the state program focuses
on new discharges. Additionally, Phase 2 of the NPDES Program will expand 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 that these additional activities obtain permits by
2003. While these urban stormwater discharges are now technically referred to as “point
sources” for the purpose of regulation, they are still diffuse sources of pollution that cannot be
easily collected and treated by a central treatment facility, as are other point sources of
pollution, such as domestic and industrial wastewater discharges. The Department recently
accepted delegation from the EPA for the stormwater part of the NPDES Program. It should be
noted that most MS4 permits issued in Florida include a reopener clause that allows permit
revisions to implement TMDLs once they are formally adopted by rule.




                                                 8
Florida Department of Environmental Protection
  DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),




Appendix C: Reference Approach Information




                                                 9
Florida Department of Environmental Protection
                        DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),



Table C-1: Tampa Bay Watershed WBIDs Used for Nutrient Target Setting

                                       NUTRIENT                                               WATERBODY
         PLANNING UNIT                ECOREGION     WBID               BASIN                     TYPE        CLASS              COMMENTS
                                                                                                                         Water quality between Sept.
                                                                                                                         2004 and Oct. 2005
                                                                                                                         influenced by upstream
                                                                                                                         emergency order
                                                                                                                         discharges. Data from 2004
                                                                                                                         and 2005 not used in
 Alafia River                         Bone Valley   1621D   ALAFIA RIVER (NORTH PRONG)          STREAM         3F        analysis.
 Hillsborough River                   Bone Valley   1482    BLACKWATER CREEK                    STREAM         3F
 Hillsborough River                   Bone Valley   1495A   ITCHEPACKASASSA CREEK               STREAM         3F
                                                            LITTLE MANATEE RIVER (NORTH
 Little Manatee River                 Bone Valley   1742B   FORK)                              STREAM          3F        OFW
 Manatee River                        Bone Valley   1819    GAMBLE CREEK                       STREAM          3F
 Hillsborough River                   Bone Valley   1542    PEMBERTON CREEK                    STREAM          3F
 Manatee River                        Bone Valley   1930A   COOPER CREEK                       STREAM           1
 Manatee River                        Bone Valley   1912    UNNAMED DRAIN                      STREAM           1
 Manatee River                        Bone Valley   1807D   MANATEE RIVER (NORTH FORK)         STREAM           1
 Alafia River                         Bone Valley   1583    POLEY CREEK                        STREAM          3F
 Alafia River                         Bone Valley   1658    FISHHAWK CREEK                     STREAM          3F
 Coastal Hillsborough Bay Tributary   Bone Valley   1666    BULLFROG CREEK                     STREAM          3F
 Coastal Old Tampa Bay Tributary      Peninsula     1541C   BRIAR CREEK                        STREAM          3F
 Coastal Old Tampa Bay Tributary      Peninsula     1569A   BISHOP CREEK                       STREAM          3F
 Coastal Old Tampa Bay Tributary      Peninsula     1529    COW BRANCH                         STREAM          3F
 Hillsborough River                   Peninsula     1454    FISH HATCHERY DRAIN                STREAM          3F
 Manatee River                        Bone Valley   1876    BRADEN RIVER BELOW WARD LAKE       ESTUARY         3M
 Manatee River                        Bone Valley   1848B   MANATEE RIVER BELOW DAM            ESTUARY         3M
 Coastal Old Tampa Bay Tributary      Peninsula     1603    DIRECT RUNOFF TO BAY               ESTUARY         3M
 Coastal Hillsborough Bay Tributary   Peninsula     1609    DIRECT RUNOFF TO BAY               ESTUARY         3M
 Coastal Middle Tampa Bay
 Tributary                            Peninsula     1709F   FRENCHMANNS CREEK - BASIN U        ESTUARY         3M




                                                                      10
Florida Department of Environmental Protection
                                DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),



Table C-2: Tampa Bay Watershed Station and Ecoregion Nutrient Results
Peninsula Streams                                                                             Total Nitrogen Station Medians (mg/L)
  WBID             Station Number                Station Name           Year:   2000   2001       2002    2003      2004         2005     2006     2007
   1529     21FLPDEM06-03                    Cow Branch Creek                                                                               0.75
   1529     21FLPDEMAMB 06-3                 Cow Branch Creek
   1529     21FLTPA 280405408243235          TP 450 - Cow Branch                                                                            0.71
  1541C     21FLPDEM11-05                    Briar Creek                                                     1.26      0.92        1.04     0.92
  1541C     21FLPDEMAMB 11-5                 Briar Creek
  1541C     21FLTPA 2821088242192            TP388-Lake Tarpon Canal                                                               0.97
  1569A     21FLPDEM12-03                    Bishop Creek                                                              0.76        0.78     0.73
  1569A     21FLPDEM12-02                    Bishop Creek                                                              1.02        0.79     0.83
  1569A     21FLPDEM12-04                    Bishop Creek, South Branch
   1454     21FLTPA 281058608200429          TP481 - Fish Hatchery Drain                                                                             0.51
                                                    TN Annual Averages                                       1.26      0.90        0.89     0.79     0.51
                                                   Peninsula Stream Average                                                                          0.87



Peninsula Streams                                                                        Total Phosphorus Station Medians (mg/L)
  WBID             Station Number                Station Name           Year:   2000   2001       2002    2003      2004         2005     2006     2007
   1529     21FLPDEM06-03                    Cow Branch Creek                                               0.160                          0.070
   1529     21FLPDEMAMB 06-3                 Cow Branch Creek
   1529     21FLTPA 280405408243235          TP 450 - Cow Branch                                                                           0.100
  1541C     21FLPDEM11-05                    Briar Creek                                                    0.220                 0.200    0.165
  1541C     21FLPDEMAMB 11-5                 Briar Creek
  1541C     21FLTPA 2821088242192            TP388-Lake Tarpon Canal                                                              0.235
  1569A     21FLPDEM12-03                    Bishop Creek                                                                                  0.090
  1569A     21FLPDEM12-02                    Bishop Creek                                                                                  0.215
  1569A     21FLPDEM12-04                    Bishop Creek, South Branch
   1454     21FLTPA 281058608200429          TP481 - Fish Hatchery Drain                                                                            0.190
                                                    TP Annual Averages                                      0.190                 0.218    0.128    0.190
                                                   Peninsula Stream Average                                                                         0.181




                                                                                 11
Florida Department of Environmental Protection
                                DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),


Bone Valley Streams                                                                             Total Nitrogen Station Medians (mg/L)
  WBID             Station Number                Station Name           Year:   2000     2001       2002     2003     2004       2005     2006     2007
   1666     21FLHILL132                      Bullfrog Creek at Symmes Road        1.41     1.11       1.29     1.21     1.42

   1666     21FLHILL167                      Bullfrog Creek at Big Bend Rd.                                                        0.67

   1666     21FLTPA 275007208220464 TP 440 - Bullfrog Creek                                                                                 1.13
   1666     112WRD 02300700         BULLFROG CREEK NR
                                    WIMAUMA, FLA.
   1666     21FLTPA 274747808220566 TP 441 - Bullfrog Creek                                                                                 0.68
   1583     21FLPOLKPOLEY CRK N1 "W on Pipkin; R on S Pipkin Rd
                                    1/4 Mile of R
   1583     21FLPOLKPOLEY CRK S2 "W on Pipkin; R on S Pipkin Rd
                                    1/4 Mile of R
   1583     21FLTPA 27552458201486 Poley Creek @ SR 60                                                                  0.88       0.82
   1658     21FLHILL155             Fishhawk Creek at Fishhawk                                                                     0.79              0.65
                                    Blvd.
   1658     21FLWQSPHIL598GS        Alafia River (Long Flat Cr) near
                                    Hobson Sim Rd (WBID 1658)
   1658     21FLWQSPHIL596GS                 Fishawk Creek at Boyette Rd
                                             (WBID 1658)
   1819     21FLMANAGC2                      GC2                                           1.22                1.16     0.96       1.24     1.64     0.93
  1621D     21FLHILL115                      N Prong Alafia River upstream        1.77     1.41       1.35     1.50                                  1.46
                                             of confluence w/ S Prong
  1742B     21FLHILL140                      Little Manatee River at CR 579       1.38     1.63       1.90     1.37     1.68       1.46              1.60
  1742B     21FLHILL129                      Little Manatee River at SR 674       0.88     1.00       1.13     0.93     1.23       1.14              0.96
  1742B     21FLIMCALM674                    Little Manatee R. at SR674                    1.19
  1495A     21FLTPA 24030067                 TP43 - ITCHEPACKASASSA                                                                                  1.31
                                             CREEK
   1912     21FLMANATS5                      TS5                                           0.87       1.12     1.07     0.73       1.02     1.06     0.87
  1807D     21FLMANAD3                       D3                                            0.98       1.16     1.23     0.59       1.16     1.07     0.75
  1930A     21FLMANATS4                      TS4                                                      0.83     1.20     0.94       1.10     1.38     0.92
  1930A     21FLMANATS3                      TS3                                                      1.00     1.23     0.93       1.16     1.32     1.21
                                                      Annual Averages             1.36     1.17       1.22     1.21     1.04       1.05     1.18     1.07
                                                  Bone Valley Stream Average                                                                         1.16


                                                                                 12
Florida Department of Environmental Protection
                                DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),


Bone Valley Streams                                                                        Total Phosphorus Station Medians (mg/L)
  WBID             Station Number                Station Name           Year:   2000     2001     2002     2003     2004         2005     2006     2007
   1666     21FLHILL132                      Bullfrog Creek at Symmes Road       0.215    0.280    0.350    0.225     0.190
   1666     21FLHILL167                      Bullfrog Creek at Big Bend Rd.                                                       0.190
   1666     21FLTPA 275007208220464 TP 440 - Bullfrog Creek                                                                                0.180
   1666     112WRD 02300700         BULLFROG CREEK NR
                                    WIMAUMA, FLA.
   1666     21FLTPA 274747808220566 TP 441 - Bullfrog Creek                                                                                0.230
   1583     21FLPOLKPOLEY CRK N1 "W on Pipkin; R on S Pipkin Rd
                                    1/4 Mile of R
   1583     21FLPOLKPOLEY CRK S2 "W on Pipkin; R on S Pipkin Rd
                                    1/4 Mile of R
   1583     21FLTPA 27552458201486 Poley Creek @ SR 60                                                                0.795       0.660
   1658     21FLHILL155             Fishhawk Creek at Fishhawk                                                                    0.480             0.456
                                    Blvd.
   1658     21FLWQSPHIL598GS        Alafia River (Long Flat Cr) near
                                    Hobson Sim Rd (WBID 1658)

   1658     21FLWQSPHIL596GS                 Fishawk Creek at Boyette Rd
                                             (WBID 1658)
   1819     21FLMANAGC2                      GC2                                          0.386    0.362    0.382     0.390       0.380    0.270    0.220
  1621D     21FLHILL115                      N Prong Alafia River upstream                3.280    3.045    2.965                                   1.848
                                             of confluence w/ S Prong
  1742B     21FLHILL140                      Little Manatee River at CR 579               0.350    0.430    0.495     0.610       0.385             0.297
  1742B     21FLHILL129                      Little Manatee River at SR 674               0.580    0.580    0.650     0.750       0.635             0.761
  1742B     21FLIMCALM674                    Little Manatee R. at SR674                   0.600
  1495A     21FLTPA 24030067                 TP43 - ITCHEPACKASASSA                                                                                 0.460
                                             CREEK
   1912     21FLMANATS5                      TS5                                          0.311             0.081     0.110       0.105    0.056    0.056
  1807D     21FLMANAD3                       D3                                           0.434    0.334    0.381     0.390       0.360    0.335    0.415
  1930A     21FLMANATS4                      TS4                                          0.172             0.134     0.190       0.083    0.120    0.110
  1930A     21FLMANATS3                      TS3                                                            0.112     0.200       0.145    0.056    0.056
                                                      Annual Averages            0.215    0.710    0.850    0.603     0.403       0.342    0.178    0.468
                                                  Bone Valley Stream Average                                                                        0.471



                                                                                 13
Florida Department of Environmental Protection
                                DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),


Peninsula Estuaries                                                              Total Nitrogen Station Medians
                                                                                             (mg/L)
  WBID             Station Number                Station Name            Year:    2000     2001       2002     2003     2004     2005     2006     2007
   1609     21FLHILL36                       Old Tampa Bay                                              0.73
  1709F     21FLPDEM48-03                    Frenchman's Creek
   1603     21FLPDEMAMB 21-1                 Coastal Zone 3                         0.78     1.14       1.26
                                                      Annual Averages               0.78     1.14       0.99
                                                  Peninsula Estuaries Average                                                                        0.97

Peninsula Estuaries                                                                Total Phosphorous
                                                                                 Station Medians (mg/L)
  WBID             Station Number                Station Name            Year:    2000     2001       2002     2003     2004     2005     2006     2007
   1609     21FLHILL36                       Old Tampa Bay                                             0.140
  1709F     21FLPDEM48-03                    Frenchman's Creek
   1603     21FLPDEMAMB 21-1                 Coastal Zone 3                        0.145    0.170      0.180
                                                      Annual Averages              0.145    0.170      0.160
                                                  Peninsula Estuaries Average                                                                       0.158

Bone Valley Estuaries                                                                             Total Nitrogen Station Medians (mg/L)
  WBID             Station Number                Station Name            Year:    2000     2001       2002     2003     2004     2005     2006     2007
  1848B     21FLMANALM4                      LM4                                             1.25                0.86     0.81     1.42     1.14     0.71
  1848B     21FLMANALM5                      LM5                                                                                            1.19     0.77
   1876     21FLMANALM3                      LM3                                             1.35                0.82     0.92     1.33     1.09     0.75
                                                      Annual Averages                        1.30                0.84     0.87     1.37     1.14     0.74
                                                 Bone Valley Estuaries Average                                                                       1.04

Bone Valley Estuaries                                                                       Total Phosphorous Station Medians (mg/L)
  WBID             Station Number                Station Name            Year:    2000     2001       2002     2003     2004     2005     2006     2007
  1848B     21FLMANALM4                      LM4                                            0.426      0.327    0.275    0.345    0.300    0.270    0.260
  1848B     21FLMANALM5                      LM5                                                                                           0.370    0.355
   1876     21FLMANALM3                      LM3                                            0.356      0.304    0.291    0.215    0.270    0.305    0.285
                                                      Annual Averages                       0.391               0.283    0.280    0.285    0.315    0.300
                                                 Bone Valley Estuaries Average                                                                      0.309

                                                                                   14
Florida Department of Environmental Protection
Figure C-1 – Waterbodies in the Tampa Bay Watershed Used to Develop
            Nutrient Targets.


                                   15
  DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),




Appendix D: Comments and Responses




                                                 16
Florida Department of Environmental Protection
  DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),




D-1: Responses to FDOT Comments

                                           August 18, 2009



Ms. Susan C. Moore
Maintenance Environmental Coordinator
Florida Department of Transportation
11201 N. McKinley Drive, MS 1200
Tampa, FL 33612

Dear Ms. Moore:

Thank you for your time and effort in reviewing the TMDLs that the Department recently proposed for
impaired waters in the Tampa Bay basin. We appreciate your detailed review and the well thought-out
questions that you presented in your comments.

In the order in which they were presented, what follows are the comments from FDOT District 7and our
responses (shown in blue).

GENERAL COMMENTS
The following comments relate to multiple TMDLs where specific comments are provided below for each
of the TMDL documents.

1. The figures that show the WBIDs and also identify the "FDOT Local Roads" are not an accurate
   depiction of the roadways that FDOT is responsible for. Please isolate out those roads that are part
   of FDOT’s responsibility from those controlled by the Cities and Counties. In the alternative, simply
   identify roads as “Local Roads” in the legend.

    Response: Footnote will be added to all such figures to note that roads are for illustration purposes
    only and are not meant to be an accurate depiction of roadways for which FDOT is responsible.

2. The load reductions determined for the non-point sources, which include the WLA for the stormwater
   (under the MS4 permit) and the LA, have not been allocated but simply applied evenly between the
   WLA for Stormwater and the LA. Sufficient studies have not been completed to determine if an even
   distribution of the load reductions is justified, therefore some language acknowledging this should be
   put into both the TMDL documents and ultimately the rules to allow the ability to finalize (and
   therefore change the assigned reductions) under the BMAP. The concern exists that once the
   WLAstormwater percent reductions are put into the adopted TMDL document and the rule, the language
   in the MS4 permits would tie those reductions to the permit, and to not implement those reductions
   may put the permittees in violation. This also provides opportunities for third parties to challenge.
   [This comment applies to all TMDLs reviewed in which there was an WLA-MS4 allocation specified.]

    Response: In 2001, the Department submitted to the Governor and Legislature a document outlining
    the intended process for the allocation of loads under the TMDL Program. One key provision of the
    proposal was to level the “playing field,” such that once stakeholders had the opportunity to meet and
    discuss what steps needed to be taken and to get appropriate credit for those initiatives already
    completed, the specific allocations will be set by the agreements reached under the Basin
    Management Action Plan (BMAP). This process has been successfully used in several adopted
    BMAPs and has demonstrated the flexibility that remains after setting the initial reductions for
    stormwater-related allocations (LA and WLAsw) at identical levels.



                                                     17
Florida Department of Environmental Protection
  DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),



     The laws of Florida form the underlying basis for the initial equal allocations. In particular, Section
     403.067(6)(b) of Florida Statutes, states in part that:
Ms. Susan C. Moore
Maintenance Environmental Coordinator
Florida Department of Transportation

August 18, 2009
Page Two


     “Allocations may also be made to individual basins and sources or as a whole to all basins and
    sources or categories of sources of inflow to the water body or water body segments. An initial
    allocation of allowable pollutant loads among point and nonpoint sources may be developed as part
    of the total maximum daily load. However, in such cases, the detailed allocation to specific point
    sources and specific categories of nonpoint sources shall be established in the basin management
    action plan…”

    Additionally, each of the draft TMDL reports contains language in the NPDES Stormwater Discharges
    section in chapter 6 of the reports (repeated below) to address the issue of allocation between the
    WLA for stormwater and the LA portions of the TMDL.

    “It should be noted that any MS4 permittee is only responsible for reducing the anthropogenic loads
    associated with stormwater outfalls that it owns or otherwise has responsible control over, and it is
    not responsible for reducing other nonpoint source loads in its jurisdiction.”

3. In some of the TMDLs within the Source Assessment Chapter (Chapter 4), tables are provided for the
   calculation of loads to the system. These loads are not utilized within the TMDL but rather for
   information purposes on the potential contribution of various land use types. While the total load
   assigned to Highways was generally zero based upon zero area being assigned to that category, the
   EMC values listed in the table appear high. This will be important when the time comes for
   development of the allocation distribution. Between December 2004 and October 2007 roadway
   runoff water quality data were collected by Johnson Engineering for FDOT District 1 at four locations
   within District 1. Ten events were sampled for each of the four locations, with samples collected at
   both the inflows and outflows of existing stormwater treatment ponds. All collection, transfer, and
   handling procedures were conducted in accordance with FDEP Standard Operating Procedures and
   samples were analyzed by certified labs. Average values for TN and TP at the pond inflows were
   determined to be 1.17 mg/l and 0.158 mg/l, respectively. [It is perhaps noteworthy to observe that the
   highest average TN and TP values were measured at the first site sampled (i.e., samples collected
   between December 2004 and November 2005) which is also the site with the lowest percentage of
   impervious area.] Given the changes to roadway management practices that FDOT has undertaken
   over the past several years and the rigorous quality control used in these studies compared with the
   older studies, we believe that the numbers presented by Johnson Engineering are more
   representative than some of the standard EMC values being utilized. [This comment applies to all
   nutrient and DO TMDL documents reviewed where loading tables were provided].

    Response: A copy of the Johnson Engineering Study report was not included with the comments we
    received. If FDOT could provide the report to Mr. Eric Livingston (Bureau Chief for the Bureau of
    Watershed Restoration), it will be reviewed for incorporation into the stormwater database and use in
    estimation of transportation event mean concentrations (EMCs).

SPECIFIC COMMENTS
The following are specific comments that relate to the individual TMDL documents reviewed.




                                                      18
Florida Department of Environmental Protection
  DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),



TAMPA BAY BASIN
Alligator Creek and Alligator Lake (WBIDs 1574 and 1574A): DO and DO/Nutrients

1. The determination of the 47.5 TSI as the historical value was not adequately documented in the
   TMDL document. This provided the basis for the ultimate TSI target determined as 10 above that
   value with a 5 TSI set aside. Please provide documentation on how the 47.5 TSI background was
   determined.

    Response: The TSI refers to the trophic state index for lakes, which is based on Lake chlorophyll a,
    Total Nitrogen, and Total Phosphorus levels; individual TSI values are calculated following the
    procedures outlined on pages 86 and 87 of the State’s 1996 305(b) report, which are incorporated by
    reference into Rule 62-303, FAC. The specific calculation methodology for TSI has been included in
    the draft report.

    The historic minimum TSI value for Alligator Lake was determined by first calculating the individual
    TSIs as described above for the entire period of record. Within each year, seasonal mean TSIs are
    calculated; the annual average TSI is calculated as the average of the seasonal mean TSI values,
    subject to certain data sufficiency requirements as described in 62-303.350 (2)(a): Data must meet
    the requirements of paragraphs (2)-(4), (7), and (8) in Rule 62-303.320, FAC.

    Calculations of the annual average TSI values were performed according to the following:
    62-303.350 (2)(b): At least one sample from each season shall be required in any given year to
    calculate a Trophic State Indix (TSI) or an annual mean chlorophyll a value for that year (for the
    purposes of this chapter, the four seasons shall be January 1 through March 31, April 1 through June
    30, July 1 through September 30, October 1 through December 31), and 62-303.350 (2)(c): If there
    are multiple chlorophyll a or TSI values within a season, the average value for that season shall be
    calculated from the individual values and the four quarterly values shall be averaged to calculate the
    annual mean for that calendar year.

    Using data for all years for which data sufficiency was met with which to calculate an annual average,
    a five-year historic minimum was calculated subject to 62-303.350 (3): When comparing changes in
    chlorophyll a or TSI values to historic levels, historical levels shall be based on the lowest five-year
    average for the period of record. To calculate a five-year average, there must be annual means from
    at least three years of the five-year period.

    For Alligator Lake, the five-year period resulting in the minimum five-year annual average to be used
    as the historic minimum value for TSI of 47.5 was the five year period of 1994–1998.

Bishop Creek Tidal and Mullet Creek Tidal (WBIDs 1569 and 1575): DO/Nutrients

1. Some evaluation of what the percent reductions mean (in terms of allowable load) in relation to the
   loadings determined through the Tampa Bay TMDL/RA program should be performed. Significant
   effort went into determining loadings to be protective of the bay (and which most likely will be
   protective of the near bay areas) and local groups have gone through an extensive RA process to
   identify allowable loads. This needs to be accounted for in the TMDLs as they are using the bay
   targets as one basis. The TMDL targets which govern the TMDLs presented here focus on meeting
   DO criteria in the local waterbodies. The analyses showed that the targets needed to be protective of
   Chl a targets (set at bay levels) were less restrictive than the DO targets. As DO is a function of
   many factors (SOD, hydraulics/reaeration) as well as nutrients, before imposing additional reductions
   beyond those determined under the RA process, the level of study needs to be more comprehensive
   and take into account the other factors that impact DO.

Response: In the development of the Bishop Creek and Mullet Creek Tidal TMDLs there were two major goals. The
first goal, as is pointed out in the above comment, was to meet the individual waterbody DO requirements through
reduction of the determined causative pollutant (total nitrogen). The second was to ensure that the level of

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Florida Department of Environmental Protection
  DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),



protection determined for these creeks (which feed directly into Tampa Bay) was consistent with the previously
determined Tampa Bay chlorophyll-a target, i.e. the proposed total nitrogen level is appropriate to meet this goal.
Section 3.2.2 in the TMDL report has multiple references to both of these objectives. In addition, there was a final
step to make sure that both of these objectives were met when determining a final TN Target. The Department
agrees that several factors may contribute to low dissolved oxygen, including hydraulics and SOD, which contribute
to making a regression relationship difficult when involving only a few of the factors. Based on the information
available, the conclusion that total nitrogen is a major factor in the causing the depressed DO level remains. But
moving forward, the Department encourages stakeholders to collect additional data and increase their
understanding of how all factors contribute to the problem in a way that provides maximum protection for the bay
and these tributaries.


2. The analysis used one station with the highest TN concentrations in order to get the total reduction
   applied to the whole WBID, this doesn't make sense. If multiple stations exist then should use all to
   apply reductions as they apply to the whole WBID not just the location where the stations are.
   Assessments are done with all of the data for the WBID not just single stations.

    Response: The entire reference station analysis process was carried out based on a station-by-
    station basis, focusing only on the major sampling stations. The purpose in basing the reduction on
    the station with the highest annual median concentration (over the verified period) is to have the
    TMDL effective in elevating the “worst case” dissolved oxygen concentrations. This strategy
    introduces a reasonable margin of safety. It is important to remember that Bishop Creek and Mullet
    Creek sampling, as true with most surface water sampling, is composed of a limited number of
    discrete monthly grab samples over a period of time. Thus, to have a TMDL that at least reduces the
    highest annual TN median is not overly conservative. This is especially true for Bishop Creek Tidal
    and Mullet Creek Tidal, both of which had only a limited number of sample stations.

    In the case of Mullet Creek, only two stations represent the bulk of the samples (42 samples) taken
    over the verified period, and 60% of these samples came from sample station with the highest annual
    median TN. In the case of Bishop Creek, only two stations represent the bulk of the samples
    (54 samples) taken over the verified period, and 39% of these samples came from the sample station
    with the highest annual median TN. Thus, the stations with the annual high concentrations
    represented a significant portion of the total samples taken during the verified period.

Brushy Creek, Sweetwater Creek and Lower Rocky Creek (WBIDs 1498, 1516 and 1563):
DO/Nutrients

1. The 0.75 mg/L TN value is set in the upper reaches (non-marine segments) at 0.75 in order to be
   protective of the downstream uses. The value for the upstream WBIDs (1498, 1516) that would be
   protective of their uses using the same methodology and table for Freshwater Streams would be
   1.27 mg/L. There is no information or analysis to demonstrate that 100% of the nutrients from the
   upstream make it to the downstream segments and therefore this approach may be overly
   conservative for the upstream segments.

    Response: Recall that the estuary target, based on the reference method, would be 0.62 mg/L.
    A freshwater stream of 0.75 mg/L (that feeds into the estuary) is already less conservative than some
    might request, but is set at that level to permit a reasonable transition into the estuary WBID. Here,
    the limiting factor is the target for the estuary, which is also protective of Tampa Bay.

2. For Lower Rocky Creek some evaluation of what the percent reductions mean (in terms of allowable
   load) in relation to the loadings determined through the Tampa Bay TMDL/RA program should be
   performed. Significant effort went into determining loadings to be protective of the bay (and which
   most likely will be protective of the near bay areas) and local groups have gone through an extensive
   RA process to identify allowable loads. This needs to be accounted for in the TMDLs as they are


                                                        20
Florida Department of Environmental Protection
  DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),



    using the bay targets as one basis. The TMDL targets which govern the TMDLs presented here
    focus on meeting DO criteria in the local waterbodies. The analyses showed that the targets needed


    to be protective of Chl a targets (set at bay levels) were less restrictive than the DO targets. As DO is
    a function of many factors (SOD, hydraulics/reaeration) as well as nutrients, before imposing
    additional reductions beyond those determined under the RA process, the level of study needs to be
    more comprehensive and take into account the other factors that impact DO.

    Response: As noted in the above comment, several factors should be and were involved in
    establishing the target concentration for Lower Rocky Creek. These included meeting the nutrient
    limit of the receiving waterbody, Tampa Bay, as well as the load requirements of the Lower Rocky
    Creek itself. The reference method essentially provides a Total Nitrogen target that has been
    demonstrated to be achievable for estuaries in Tampa Bay. The RA target for Tampa Bay is
    considered in that the tributary target concentration is lower than the RA target. Factors such as SOD
    and hydraulics/reaeration have been implicitly considered by evaluating the nutrient concentrations in
    WBIDs in the similar geographic area that are not impaired for DO or nutrients (chlorophyll-a).

3. The high reductions in Lower Rocky Creek come from the data from year 2000. The 1.65 TN value
   for that year is significantly higher than all the other years (other highest year was 2002 at 1.15).
   Examination of the upstream data available in the report (Table 5.2b) does not indicate year 2000 as
   significantly higher than other years. As all of the data is not provided in the report to determine if this
   high value was the result of anomalous data, please provide an explanation for the levels of TN for
   that year, it does not seem consistent.

    Response: The annual median TN concentration of 1.65 mg/L is the annual median from a full year
    of data from the station with the most data. A single data point may be reason for concern about
    being too conservative, but it is felt that the highest annual median for the 7-year verified period is the
    worst case scenario that the TMDL needs to address. Furthermore, if during the implementation, the
    target concentration is achieved before the percent reduction is achieved, the percent reduction can
    be adjusted.


Bullfrog Creek Tidal Segment (WBID 1666A): DO/Nutrients

1. Some evaluation of what the percent reductions mean (in terms of allowable load) in relation to the
   loadings determined through the Tampa Bay TMDL/RA program should be performed. Significant
   effort went into determining loadings to be protective of the bay (and which most likely will be
   protective of the near bay areas) and local groups have gone through an extensive RA process to
   identify allowable loads. This needs to be accounted for in the TMDLs as they are using the bay
   targets as one basis. The TMDL targets which govern the TMDLs presented here focus on meeting
   DO criteria in the local waterbodies. The analyses showed that the targets needed to be protective of
   Chl a targets (set at bay levels) were less restrictive than the DO targets. As DO is a function of
   many factors (SOD, hydraulics/reaeration) as well as nutrients, before imposing additional reductions
   beyond those determined under the RA process, the level of study needs to be more comprehensive
   and take into account the other factors that impact DO.

    Response: The Department believes that the best way to move forward in restoring water quality in
    Bullfrog Creek is to establish the concentration-based TMDL and to calculate the source-specific
    allowable loads to the waterbody during the BMAP development process. The Tampa Bay Nitrogen
    Management Consortium is scheduled to submit to the Department a draft update of the Reasonable
    Assurance (RA) Plan for Tampa Bay by September 25, 2009. The RA plan will provide load
    allocations to individual entities discharging to the bay, which have not yet been completed. Up until
    this time, the total nitrogen loadings to Tampa Bay have been calculated and evaluated for each of
    the major bay segments, as these are the assessment units used for tracking progress in meeting the

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Florida Department of Environmental Protection
  DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),



    resource-based water quality targets. Preferably, the calculation of allowable loads to the smaller
    impaired water segments for which TMDLs have been developed, like Bullfrog Creek, would also be
    viewed for consistency at a larger scale, which would be completed after the review and approval of
    the updated RA plan, to ensure that consistent flow estimates and other assumptions are used in
    both processes.

    It is acknowledged that dissolve oxygen is influenced by a number of factors. We believe that the
    reference condition approach to establish the TMDL using observed water quality in Lower
    Hillsborough Bay, which is not impaired for nutrients and dissolved oxygen, is appropriate for
    addressing the nutrient and dissolved oxygen impairment in the adjacent Bullfrog Creek tidal segment
    at this time.

Coffeepot Bayou (WBID 1700): DO/Nutrients

1. The use of the minimum value (0.44) of the TN annual averages derived from the Bay measurements
   seems overly conservative. The reasoning is provided to account for uncertainty but both the target
   and reductions come directly from data, therefore there should be lower uncertainty. Should use
   either annual average maximum and compare to highest year, or do averages in bay during VP and
   averages in the bayou. In other TMDLs around the Bay the local bay Chl a target was used and a TN
   that was derived from averages was determined and then targeted (not the lowest). This would
   provide consistency with the Tampa Bay work and would provide a margin of safety as the tidal
   tributary would be targeting a Chl a set to return seagrasses to the Bay.

    Response: The DEP has revised the TMDLs to be consistent with other TMDLs developed around
    Tampa Bay and has removed the regression equations from the draft report. The revisions are
    discussed further below.

        Kept the Middle Tampa Bay CChl a target of 8.5 ug/L.

    We revised the target TN TMDL concentration to be consistent with the approach used in other
    TMDLs. The revision included using the average of the annual averages for TN in Middle Tampa Bay
    that correspond to years with corrected chlorophyll a concentrations less than 8.5 ug/L (years
    highlighted in table). This changed the TN TMDL from 0.44 (based on “lowest” annual average TN in
    the bay) to 0.63 mg/L.



    Annual Average Total Nitrogen and Corrected Chlorophyll a for Middle Tampa Bay WBID 1558C

                                          Year     TN        Cchla
                                          1995    0.75       10.25
                                          1996    0.67        7.09
                                          1997    0.73        7.92
                                          1998    0.78       12.78
                                          1999    0.63        7.63
                                          2000    0.88        5.82
                                          2001    0.82        8.33
                                          2002    0.74        6.12
                                          2003    0.48        8.36
                                          2004    0.46        7.58
                                          2005    0.45        8.15
                                          2006    0.46        5.71


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Florida Department of Environmental Protection
  DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),




                                       Average*     0.63

    The concentrations used to represent the levels of pollutants to reduce from were previously based
    on the average of all the data from the verified period, as this was consistent with the other TMDLs in
    the area, the previous concentrations of 0.93 mg/L TN and 3.31 mg/L BOD5 were retained.

        Reductions:
        Previous Draft TMDL
        TN ((0.93-0.44)/0.93)*100 = 52.7% (53%)
        BOD5 ((3.31-2.00)/3.31)*100 = 39.6% (40%)

        Revised draft TMDLs:
        TN ((0.93-0.63)/0.93)*100 = 32.2% (33%)
        BOD5 ((3.31-2.00)/3.31)*100 = 39.6% (40%)

    Percent reductions were rounded up to the next whole number as part of the Margin of Safety.

Cockroach Bay (WBID 1778): DO/Nutrients

1. The use of a target (based on the regression analysis) of 0.43 (near lowest annual average of the
   Bay) seems overly conservative, i.e. setting a standard in the Bay that is lower than that set for the
   Bay itself when you are targeting the came Chl a. Simplicity would dictate that one should use either
   annual average maximum (of the bay) and compare to highest year, or do averages in bay during VP


    and averages in the bayou. The MOS would then come from targeting a Chl a in the Bay at the level
    to restore seagrasses. The use of the lowest year values is also not consistent with other TMDLs
    developed for near bay tidal areas where the Bay Chl a targets were utilized (Bishop Creek and
    Mullet Creek).

    Response: The DEP has revised the TMDL as explained below.

    The regression equation has been removed from the determination of the draft TMDLs.
    The DEP retained the Middle Bay CChla target of 8.5 ug/L.

    The revision included using the average of the annual averages for TN in Middle Tampa Bay that
    correspond to years with corrected chlorophyll a concentrations less than 8.5 ug/L (years highlighted
    in table). This changed the TN TMDL from 0.43 mg/L to 0.54 mg/L. The same BOD5 concentration of
    2.00 mg/L was used a target for restoration. To be consistent with other TMDLs, the concentration to
    reduce from was calculated as the average of the TN and BOD5 data from the impaired WBID during
    the verified period. The TN value changed from 1.62 mg/L to 1.16 mg/L and the BOD5 concentration
    changed from 4.23 mg/L to 3.18 mg/L.




                                                    23
Florida Department of Environmental Protection
  DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),



    Annual Average Total Nitrogen and Corrected Chlorophyll a for Middle Tampa Bay WBID 1558B

                                                  TN        Cchla
                                       Year       (mg/L)    (ug/L)
                                       1995       0.71      8.09
                                       1996       0.49      4.65
                                       1997       0.51      6.43
                                       1998       0.47      10.37
                                       1999       0.40      7.06
                                       2000       0.77      5.58
                                       2001       0.77      5.70
                                       2002       0.66      3.73
                                       2003       0.43      6.05
                                       2004       0.42      4.55
                                       2005       0.41      4.42
                                       2006       0.38      3.08
                                       Average*   0.54

    * Average of annual averages that correspond to years with corrected chlorophyll a concentrations
    less than 8.5 ug/L.
        Reductions:

        Current Draft TMDL:
        TN ((1.62-0.428)/1.62)*100 = 73.6% (74%)
        BOD5 ((4.23-2.00)/4.23)*100 = 52.7% (53%)

    Revised TMDLs:
       TN ((1.16-0.54)/1.16)*100 = 53.5% (54%)


        BOD5 =((3.18-2.00)/3.18)*100 = 37.1% (38%)

    Percent reductions were rounded up to the next whole number as part of the Margin of Safety.

Cross Canal-North Tidal and Allen Creek Tidal (WBIDs 1625 and 1604): DO/Nutrients

1. Some evaluation of what the percent reductions mean (in terms of allowable load) in relation to the
   loadings determined through the Tampa Bay TMDL/RA program should be performed. Significant
   effort went into determining loadings to be protective of the bay (and which most likely will be
   protective of the near bay areas) and local groups have gone through an extensive RA process to
   identify allowable loads. This needs to be accounted for in the TMDLs as they are using the bay
   targets as one basis. The TMDL targets which govern the TMDLs presented here focus on meeting
   DO criteria in the local waterbodies. The analyses showed that the targets needed to be protective of
   Chl a targets (set at bay levels) were less restrictive than the DO targets. As DO is a function of
   many factors (SOD, hydraulics/reaeration) as well as nutrients, before imposing additional reductions
   beyond those determined under the RA process, the level of study needs to be more comprehensive
   and take into account the other factors that impact DO.

    Response: As noted in the above comment, several factors should be and were involved in
    establishing the target concentration for Cross Canal North. These included meeting the nutrient limit
    of the receiving waterbody, Tampa Bay, as well as the load requirements of Cross Canal North itself.
    The reference method essentially provides Total Nitrogen targets that have been demonstrated to be

                                                    24
Florida Department of Environmental Protection
  DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),



    achievable for streams and estuaries in Tampa Bay. The RA target for Tampa Bay is considered in
    that the tributary target concentration is lower than the RA target. Factors such as SOD and
    hydraulics/reaeration have been implicitly considered by evaluating the nutrient concentrations in
    WBIDs in the similar geographic area that are not impaired for DO or nutrients (chlorophyll-a).

2. The analyses used one station with the highest TN concentrations in order to get the total reduction
   applied to the whole WBID (M24-03) which is well upstream of the bay area, which is being targeted,
   this doesn't make sense. If multiple stations exist then should use all to apply reductions as they
   apply to the whole WBID not just the location where the stations are. Assessments are done with all
   of the data for the WBID not just single stations.

    Response: The entire reference station analysis process was carried out based on a station-by-
    station basis, focusing only on the major sample stations. The purpose in basing the reduction on the
    station with the highest annual median concentration (over the verified period) is to have the TMDL
    effective in elevating the “worst case” dissolved oxygen. This strategy introduces a reasonable
    margin of safety. It is important to remember that Allen Creek and Cross Canal North, as true with
    most surface water sampling, is composed of a limited number of discrete monthly grab samples over
    a period of time. Thus, to have a TMDL that at least reduces the worst highest annual TN average is
    not overly conservative.

    In the case of Allen Creek, ten stations represent the bulk of the samples (340 samples) taken over
    the verified period, averaging 34 samples each station. The highest 3 annual median concentrations
    for these 10 stations are 1.55, 1.52, and 1.47 mg/L. It is not overly conservative to base the required
    reduction on making sure the reduced load makes the worst station compliant every year over a
    seven year period. In the case of Cross Canal North, only five stations represent the bulk of the
    samples (139 samples with an average of 28 samples per station). The station with the highest
    annual medians had medians of 1.66, 1.61, 1.51 mg/L in years 2004, 2005, and 2003 respectively.


    It is not overly conservative to take the station with the highest annual median and base the TMDL on
    lowering this worst case level (rather than lowering an overall WBID median which may leave this
    station still failing to meet environmental standards).

Moccasin Creek Tidal, Lake Tarpon Canal and Lake Tarpon Canal (WBIDs 1530, 1541A and 1541B):
DO/Nutrients

1. Appears to be a mistake in the WLA percent reduction for the freshwater portion of Lake Tarpon
   Canal, it is listed at 47% but it should be 35.9% similar to the LA.

    Response: The TMDL document has been corrected. The 47% has been changed to 35.9%

2. The text under 6.6.2 is also wrong and does not reflect the calculations made in Section 5, these
   should be changed to be consistent.

    Response: The total nitrogen reductions indicated in section 6.6.2 were in error and have been
    corrected in the TMDL document.

HILLSBOROUGH RIVER
Trout Creek, Channelized Stream, Big Ditch and Two-Hole Branch (WBIDs 1455, 1483, 1469, and
1489): DO/Nutrients

1. The nutrient targets established for TN are far below the levels that should be set for these systems.
   The TN targets are set at 0.463 mg/L (although there is some confusion within the document as to
   what the true level utilized in the final reductions is). Adjacent waterbodies where numeric nutrient


                                                    25
Florida Department of Environmental Protection
  DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),



    criteria were set, i.e. freshwater streams, the TN targets were as high as 1.73 mg/L (Mustang Ranch,
    Tampa Bypass Canal).

    Response: A combination of the calibrated WAMView and WASP was used to simulate the
    assimilative capacity and then set site-specific targets of Chla, and TN for Trout Creek. As presented
    in the draft TMDLs report at pages 66, 70, and 73, the median and average TN targets for Trout
    Creek were estimated to be 0.453 mg/L and 0.614 mg/L, respectively. Moreover, the model
    simulated target (median) of TN corresponded to the median TN target (0.463 mg/L) obtained by the
    empirical relationship for Trout Creek. It should be noted that both methods were designed to meet
    the DO criteria at any time and any place on a daily basis. Therefore, given the consistency between
    the two independent methods as applied to Trout Creek, the Department considers that the target
    obtained from the empirical method is reliable for the Hillsborough River tributaries. More importantly,
    the TN target set up by both of these methods was considered as a site-specific target that may not
    be comparable to either a regional TN target or TN targets for nearby streams derived by less
    rigorous means.

    Additionally, care should be followed when comparing the TN target concentrations from one stream
    to another because dynamic hydrogeochemical processes are possibly different from one location to
    another. For example, one stream could respond quickly to DO depletion but not the other, and/or
    one system can be nutrient-limited but not the other. Without having detailed knowledge for each
    system, differences in the TN targets may reflect that one system has a greater assimilative capacity
    for TN than the other. More importantly, assimilative capacity of TN and TP, i.e., target
    concentrations, was determined as a result of the combined effects of BOTH TN and TP
    concentrations on biological communities (Chla) in a waterbody. Therefore, a simple comparison in
    TN target concentrations between waterbodies, while ignoring TP or other essential parameters, may
    be unreasonable.

2. Examination of the present status of the tables developed under the numeric nutrient criteria
   document released in June of 2009, identifies the 25th percentile for reference unimpacted stations
   for TN = 0.71 mg/L for this region of the State. The 75th percentile (which is the value typically used
   by EPA in developing targets from reference stations) is 1.41 mg/L. Florida has been looking at the
   90th percentile as the potential value to set for reference conditions, this would give a TN target of
   1.82 mg/L.

    Response: In the TMDL reports for the Hillsborough River tributaries, interpretation of the narrative
    nutrient criterion states:


              “The IWR’s numeric Chla threshold for rivers and streams is used 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 based on annual
             average Chla levels, these thresholds are not standards and need not be used
             as the nutrient-related water quality target for TMDLs. In fact, in recognition that
             the IWR thresholds were developed using statewide conditions, the IWR
             (Section 62-303.450, F.A.C.) specifically allows the use of alternative, site-
             specific thresholds that more accurately reflect conditions beyond which an
             imbalance in flora or fauna occurs in the waterbody.”

    The Department recognized that a regional scale TN draft numeric criterion target may not best
    represent the level at which the flora and fauna become balanced. For example, Mill Creek (WBID
    1542A), where percent anthropogenic land use was about 78.9% and percent DO exceedance was
    about 59.7% during the period of 2000-2007, was listed as impaired for DO and nutrients. In
    addition, the percent DO exceedance has increased over time since 1990, as shown in Figure 2.22 in
    the Mill Creek TMDL report. During the same period of observation, the median and average


                                                      26
Florida Department of Environmental Protection
  DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),



    concentrations of TN in Mill Creek were observed to be 0.90 mg/L and 1.17 mg/L, respectively. The
       th
    25 percentile of observed TN concentrations for this impaired waterbody was about
                                                                             th
    0.52 mg/L, much less than the regional value (0.71 mg/L) of the 25 percentile for reference
    unimpacted stations. Therefore, it is the Department’s position that a site-specific target should be
    utilized to better represent these unique stream conditions in the Hillsborough River system.

3. If more reasonable values were used for the targets the data would indicate a much smaller reduction
   or no reduction at all for this water body. Examination of the available data (only presented relative to
   the modeling results) showed TN annual average values around 1.0 mg/L which if more reasonable
   targets were utilized would not result in the need for reductions.

    Response: The use of calibrated models to develop TMDLs is a sound and scientific-based
    approach for those impaired waterbodies. The TN target was obtained from a two-step process:
    (1) whether to meet the DO criteria, and then (2) whether to satisfy site-specific Chla threshold. The
    median TN target of 0.465 mg/L for Big Ditch, Channelized Stream, and Two Hole Branch was set at
    a zero percent DO exceedance (on a daily basis, see Figure 5.21) and also satisfied the median
    Chla target of 1.07 ug/L (Figure 5.22). These values are comparable to those for Trout Creek
    (median Chla 1.22 ug/L), Mill Creek and Baker Creek (long-term average <2.0 ug/L).

4. It is clear that the model has some potential issues based upon the unreasonably low values of the
   "natural" TP and TN concentrations determined, the natural levels are as low as 0.1 to 0.3 mg/L.
   Prior to using the model for development of a TMDL it is important to make sure it is accurately
   simulating the watershed and receiving water conditions, the unrealistic projections for the "natural"
   TP and TN conditions is an indicator that something is wrong with the model, i.e. there are natural
   processes not being dealt with.

    Response: The model simulation for pristine conditions was only for reference purposes. All the
    proposed TMDLs for the Hillsborough River Basin tributaries were developed based on the calibrated
    model for existing conditions, not the natural conditions. The Department understands that
    concentrations of TN under the natural conditions could be questionable since there is no directly
    observed information available under these conditions.

    The existing conditions were calibrated first, prior to establishment of natural conditions. Without
    “acceptable” calibration under the existing conditions, it is the Department’s intention that model
    simulations for load reductions would not be pursued to develop the TMDLs.

    According to a study conducted for the contribution of TN discharged from Crystal Springs to the
    lower Hillsborough River (SWFWMD, 1999), Crystal Springs, along with Trout Creek, Blackwater
    Creek, and Cypress Creek, contribute a significant amount (10-100 cfs) of flow to the Hillsborough
    River. If spring waters are a significant contributor to streams in this Hillsborough River Watershed,
    “truly” natural concentrations of TN in headwaters of the river might be expected to be similar to those
    in pristine spring waters. For Crystal Springs, nitrate concentrations measured by USGS in the early
    1920s and late 1940s were about 0.1 mg/L and 0.2 mg/L, respectively (SWFWMD, 1999). Typical
    nitrate concentrations in Florida spring waters were also reported to be less than 0.2 mg/L in the early
    1970s (FDEP, 2008). A report also indicated that the natural or background concentration of nitrate
    in the Florida aquifer has been shown to be less than 0.01 mg/L (SWFWMD, 2001). Based on
    literature review, a “truly” pristine TN value is most likely much less than 0.1 mg/L in spring waters in
    the Hillsborough River watershed. Collectively, the natural, pristine TN value that might occur for
    spring-dominant headwaters of the Hillsborough River does not seem much different from the natural,
    background TN value simulated by the model for the watershed.

5. Presently, the TMDL targets dissolved oxygen levels in the streams above 5.0 mg/L at all times and
   all places. This may not be a reasonable assumption as to the “natural” conditions of the system.
   There are many systems in Florida where dissolved oxygen conditions naturally drop below the 5.0
   mg/L. The load conditions developed and the unrealistically low levels of “natural” TN and TP

                                                     27
Florida Department of Environmental Protection
  DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),



    concentrations in the streams for the natural condition may indicate that the 5.0 mg/L target for all
    times is unreasonable. Some discussion at least should be provided relative to the natural DO
    conditions in the stream.

    Response: It is the Department’s intention that DO in Florida streams meets the DO criteria of
    5.0 mg/L at all times and all places, unless it can be shown that values below 5.0 mg/L are a result of
    pollution (not pollutants) or a naturally occurring condition. Again, DO time-variations for natural
    background conditions in the TMDL reports is for only information purposes, providing a guideline of
    the DO variation below which DO variation under the load reduction conditions (TMDL conditions)
    should be. As EPA recommended for the Hillsborough River tributaries’ TMDLs reports, the DO
    excursion documented is only a 48 hour slight deviation which is well within the protective deviations
    allowed under EPA’s biologically based DO stressor models and within model measurement error
    and therefore is not considered significant in assessing compliance with the DO criteria.



Baker Creek, Mill Creek and Spartman Branch (WBIDs 1522C, 1542A and 1561): DO/Nutrients

1. The nutrient targets established for the TN and TP are far below the levels that should be set for
   these systems. The TN targets range from 0.244 to 0.269 mg/L. This level is below the nitrate target
   identified for springs of 0.35 mg/L. Examination of the present status of the table developed under
   the numeric nutrient criteria gives the 25 percentile for reference unimpacted stations at 0.71 mg/L.
   The 75th percentile (which is the value typically used by EPA in developing reference standards from
   reference stations) is 1.41 mg/L. Florida has been looking at the 90th percentile as the potential
   value to set which would be 1.82. For Total P the targets range from 0.084 mg/L up to 0.109 mg/L.
   These WBIDs are in the Bone Valley which based upon the present status of the numeric nutrient
   criteria has a 25th percentile of reference station values at 0.192, a 75th percentile (EPA uses) of
   0.574 mg/L and a 90th percentile of 0.674 mg/L.


    Response: In the TMDL reports for the Hillsborough River tributaries, interpretation of the narrative
    nutrient criterion states:

               “The IWR’s numeric Chla threshold for rivers and streams is used 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 based on annual
               average Chla levels, these thresholds are not standards and need not be
               used as the nutrient-related water quality target for TMDLs. In fact, in
               recognition that the IWR thresholds were developed using statewide
               conditions, the IWR (Section 62-303.450, F.A.C.) specifically allows the use of
               alternative, site-specific thresholds that more accurately reflect conditions
               beyond which an imbalance in flora or fauna occurs in the waterbody.”

    In developing a site-specific target for each waterbody, the Department primarily focused on the
    assimilative capacity (Chla) of each waterbody, instead of looking at concentrations (mass per
    volume) of TN and/or TP which can vary with flows different from stream to stream. As explained in
    Chapter 5 of the draft TMDL report, the IWR uses 50% above the historical chlorophyll a value as one
    measure of impairment in streams in case chlorophyll a data indicate that annual mean chlorophyll a
    values have increased by more than 50% over the historical values for at least two consecutive years.
    The historical Chla value for Baker Creek estimated from the data collected between 1992 and 1996
    was an average of 2.75 µg/L, and an additional 50% to the historical chlorophyll a value was
    calculated to be 4.1 µg/L. Therefore, the Department determined that the Chla target for nutrient
    assimilative capacity can be an in-between value obtained from the natural background Chla
    (1.53 µg/L) and 50% above the historical chlorophyll a value (4.1 µg/L). Once the target Chla was
    established for TMDL development for Baker Creek, the model was rerun with decreasing existing

                                                     28
Florida Department of Environmental Protection
  DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),



    watershed loads until the Chla target was met. Several scenario runs were made by reducing loads
    to meet the Chla target for Baker Creek. In addition, it should be noted that a selected load reduction
    that achieves the Chla target should meet the DO target (5 mg/L) at all times and all places in Baker
    Creek, Spartman Branch and Mill Creek as well (see Figures 5.34 and 5.35). Since Spartman Branch
    and Mill Creek are upstream of Baker Creek and influences downstream water quality, the
    Department has decided that the same load reduction for Baker Creek would be applied to all
    tributaries contributing to Baker Creek to meet the DO and nutrient criteria.

    Additionally, the Department recognized that a regional scale TN draft numeric criterion target may
    not best represent the level at which the flora and fauna become balanced. For example, Mill Creek
    (WBID 1542A), where percent anthropogenic land use was about 78.9% and percent DO exceedance
    was about 59.7% during the period of 2000-2007, was listed as impaired for DO and nutrients. In
    addition, the percent DO exceedance has increased over time since 1990, as shown in Figure 2.22 in
    the Mill Creek TMDL report. During the same period of observation, the median and average
    concentrations of TN in Mill Creek were observed to be 0.90 mg/L and 1.17 mg/L, respectively. The
       th
    25 percentile of observed TN concentrations for this impaired waterbody was about
                                                                             th
    0.52 mg/L, much less than the regional value (0.71 mg/L) of the 25 percentile for reference
    unimpacted stations. Therefore, it is the Department’s position that a site-specific target should be
    utilized to better represent these unique stream conditions in the Hillsborough River system.

2. A nearby WBID, which was not evaluated using the WAM model identified a TN target of 1.73 mg/L
   and a TP target of 0.415 mg/L (Mustang Ranch).



    Response: A combination of the calibrated WAMView and WASP was used to simulate the
    assimilative capacity to set site-specific targets of Chla for Baker Creek and Mill Creek. It should be
    also noted that the method was designed to meet the DO criteria at any time and any place on a daily
    basis. Therefore, the TN target induced by site-specific DO and Chla targets may not be comparable
    to either a regional TN target or TN targets for nearby streams derived by less rigorous means.

    Additionally, care should be followed when comparing the TN target concentrations from one stream
    to another because dynamic hydrogeochemical processes are possibly different from one location to
    another. For example, one stream could respond quickly to DO depletion but not the other, and/or
    one system can be nutrient-limited but not the other. Without having detailed knowledge for each
    system, differences in the TN targets may reflect that one system has a greater assimilative capacity
    for TN than the other. More importantly, assimilative capacity of TN and TP, i.e., target
    concentrations, was determined as a result of the combined effects of BOTH TN and TP
    concentrations on biological communities (Chla) in a waterbody. Therefore, a simple comparison in
    TN target concentrations between waterbodies, while ignoring TP or other essential parameters, may
    be unreasonable.

3. If more reasonable values were used for the targets the data would indicate a much smaller reduction
   or no reduction at all.

    Response: The use of calibrated models to develop TMDLs is a sound and scientific-based
    approach for those impaired waterbodies. The TN target was obtained from a two-step process:
    (1) whether to meet the DO criteria, and then (2) whether to satisfy site-specific Chla threshold. The
    median Chla target less than 2.0 ug/L for Baker Creek and Mill Creek are comparable to those for
    Trout Creek (median Chla 1.22 ug/L) and other Hillsborough River tributaries (1.06 ug/L).

4. It is clear that the model has some potential issues based upon the unreasonably low values of the
   "natural" TP and TN concentrations, prior to using the model for development of a TMDL it is
   important to make sure it is accurately simulating conditions, the unrealistic projections for the
   "natural" TP and TN conditions is an indicator that something is wrong with the model.

                                                    29
Florida Department of Environmental Protection
  DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),




    Response: The model simulation for pristine conditions was only for reference purposes. All the
    proposed TMDLs for the Hillsborough River Basin tributaries were developed based on the calibrated
    model for existing conditions, not the natural conditions. The Department understands that
    concentrations of TN under the natural conditions could be questionable since there is no directly
    observed information available under these conditions.

    The existing conditions were calibrated first, prior to establishment of natural conditions. Without
    “acceptable” calibration under the existing conditions, it is the Department’s intention that model
    simulations for load reductions would not be pursued to develop the TMDLs.

    According to a study conducted for the contribution of TN discharged from Crystal Springs to the
    lower Hillsborough River (SWFWMD, 1999), Crystal Springs, along with Trout Creek, Blackwater
    Creek, and Cypress Creek, contribute a significant amount (10-100 cfs) of flow to the Hillsborough
    River. If spring waters are a significant contributor to streams in this Hillsborough River Watershed,
    “truly” natural concentrations of TN in headwaters of the river might be expected to be similar to those
    in pristine spring waters. For Crystal Springs, nitrate concentrations measured by USGS in the early
    1920s and late 1940s were about 0.1 mg/L and 0.2 mg/L, respectively (SWFWMD, 1999). Typical
    nitrate concentrations in Florida spring waters were also reported to be less than 0.2 mg/L in the early
    1970s (FDEP, 2008). A report also indicated that the natural or background concentration of nitrate
    in the Florida aquifer has been shown to be less than 0.01 mg/L (SWFWMD, 2001). Based on
    literature review, a “truly” pristine TN value is most likely much less than 0.1 mg/L in spring waters in
    the Hillsborough River watershed. Collectively, the natural, pristine TN value that might occur for
    spring-dominant headwaters of the Hillsborough River does not seem much different from the natural,
    background TN value simulated by the model for the watershed.

5. Presently, the TMDL targets dissolved oxygen levels in the streams above 5.0 mg/L at all times and
   all places. This may not be a reasonable assumption as to the “natural” conditions of the system.
   There are many systems in Florida where dissolved oxygen conditions naturally drop below the
   5.0 mg/L. The load conditions developed and the unrealistically low levels of “natural” TN and TP
   concentrations in the streams for the natural condition may indicate that the 5.0 mg/L target for all
   times is unreasonable. Some discussion at least should be provided relative to the natural DO
   conditions in the stream.

    Response: It is the Department’s intention that DO in Florida streams meets the DO criteria of
    5.0 mg/L at all times and all places, unless it can be shown that values below 5.0 mg/L are a result of
    pollution (not pollutants) or a naturally occurring condition. Again, DO time-variations for natural
    background conditions in the TMDL reports is for information purposes only, providing a guideline of
    the DO variation below which DO variation under the load reduction conditions (TMDL conditions)
    should be. As EPA recommended for the Hillsborough River tributaries’ TMDLs reports, the DO
    excursion documented is only a 48 hour slight deviation which is well within the protective deviations
    allowed under EPA’s biologically based DO stressor models and within model measurement error
    and therefore is not considered significant in assessing compliance with the DO criteria.

In closing, we appreciate your continuing active interest in the Total Maximum Daily Load program, and
look forward to all the FDOT TMDL team members helping us to restore the designated uses in all of the
affected watersheds.

                                           Sincerely,

                                           Jan Mandrup-Poulsen, Administrator
                                           Watershed Evaluation and TMDL Section
                                           Florida Department of Environmental Protection



                                                        30
Florida Department of Environmental Protection
  DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),



D-2: Responses to Pinellas County Comments


                                                   August 27, 2009



Ms. Kelli Hammer Levy
Division Director
Watershed Management Division
Pinellas County Department of Environmental Management
300 S. Garden Ave.
Clearwater, FL 33756


Subject: Comments on the draft TMDLs for:
           • Alligator Creek (WBID 1574) and Alligator Lake (1574A) – Dissolved Oxygen (DO) and
             Nutrients
           • Cross Canal North Tidal (WBID 1625) – DO and Allen’s Creek Tidal (WBID 1604) - DO and
             Nutrients
           • Moccasin Creek Tidal (WBID 1530) and Lake Tarpon Canal (WBID 1541A and 1541B) – DO
             and Nutrients
           • Bishop Creek Tidal (WBID 1569) – DO and Mullet Creek Tidal (WBID 1575) – DO and Nutrient
           • Bishop Creek Tidal and Bishop Creek (WBIDs 1569 and 1569A) – Fecal Coliforms
           • Double Branch (WBID 1513) – DO and Nutrient


Dear Ms. Levy:

The Department has reviewed the County’s comments, in the July 20, 2009 letter, on the proposed June 2009
dissolved oxygen, nutrient, and fecal coliform bacteria TMDLs in the Tampa Bay Basin. We appreciate the time and
effort you and your staff put into reviewing these draft TMDLs. We have made edits to the draft reports and in
some cases revisions to the TMDLs as a result of your comments. By all working together in this way, the final
TMDLs will be improved. The following are our responses to the comments in the order presented in your letter.

Alligator Creek (WBID 1574) and Alligator Lake (WBID 1574A) – DO and Nutrients

    1. Alligator Lake is listed for DO impairment on the May 14, 2009 Verified List with Total Phosphorus
       listed as the causative pollutant, yet the TMDL is for Total Nitrogen (TN). Please provide
       additional information on this decision.

Response: The linkage to TP on the verified list was a result of TP exceeding the listing threshold concentration.
However, our review of the data during the development of the TMDL revealed that the lake is nitrogen limited.
The nutrient TMDL was established by reducing the annual average Trophic State Index (TSI) using the calculation
methodology for TSI incorporated by reference in Rule 62-303, Florida Administrative Code (FAC). This
methodology establishes the TSI based on the average of a nutrient-TSI and a Chla-TSI. The calculation of the
nutrient-TSI is based on the relationship between TN and TP. If the lake is nitrogen limited (ratio of TN/TP; less
than 10, as it is in Alligator Lake) TP is not included in the calculation of the nutrient-TSI. However, if during the
development of a Basin Management Action Plan (BMAP) for Alligator Creek and Alligator Lake it is decided by the
local stakeholders that the lake should be either co-limited for both nitrogen and phosphorus or phosphorus
limited, a TMDL for TP could be developed.



                                                          31
Florida Department of Environmental Protection
  DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),



Ms. Kelli Hammer Levy
Pinellas County Department of Environmental Management
August 27, 20009
Page Two


Examples:

These are just some examples of TP reductions required to have Alligator Lake co-limited or phosphorus limited.
The target TSI is a TSI less than 52.5.

A. If TN in the lake is at the TN concentration proposed for the creek in the original draft TMDL report of 0.86 mg/L
(current verified period annual average for the lake is 0.88 mg/L) and somehow only TP is reduced to make the
ratio of TN/TP = 20.0 (mid-range of co-limitation) the TP would need to be
0.043 mg/L (TN/TP ratio = 20 and TSI = 52.3). This would require a 72 percent reduction in TP from the verified
period annual average of 0.154 mg/L.

B. Same scenario except target for lake is TP limitation. TP would need to be reduced to
0.025 mg/L, resulting in a TSI of 52.2. This would require an 84 percent reduction in TP.

To achieve the target TSI of less than 52.5 by keeping the lake TN limited would require a TN concentration of 0.72
mg/L (concentration in current draft report of 0.83 mg/L was a mistake in that the TSI was only reduced to 55
instead of the target of 52.5).

 If the TN concentration in the lake is reduced as reductions in TP occur, then the TP concentration
required to meet a TSI of less than 52.5 goes down (in order to maintain the same ratio in TN to TP) and
the percent reductions go up over the scenarios presented above.

    2. Section 2.2, page 6, states that Alligator Lake is a small lake with high elevation, which is the
       reason for low DO in winter months. The citation listed for Guenther and Hubert is a study of
       small Wyoming reservoirs and not applicable to a coastal lake in Florida. Alligator Lake is an
       impounded marine embayment, 72 acres and less than 10 feet above sea level. Also, monthly
       mean DO values for Alligator Lake are inconsistent with IWR 35 data. Lowest averages occur
       during summer months. Please revise the associated table and graph as shown below.

Response: Revisions to the TMDL report have been made.

    3. Section 3.4 and section 5.1 state the approach for developing the DO TMDL in the lake is to
       address the nutrient reductions necessary to restore the lake and to reduce the BOD5 to the
       levels recorded in 1997 and 1998, where BOD5 (1.34 mg/L) and Chla
       (4.5 ug/L) were at period record lows. Was the BOD5 period low associated (i.e. same
       month and year) with the Chl-a low? Also, 1997 was classified as a strong El Niño year and 1998
       a moderate La Niña year according to the Oceanic Nino index (). This resulted in heavier than
       usual rainfall for those years where the normal average is 52 inches per year based on
       SWFWMD data. These atypical BOD5 and Chla results were artifacts of the heavy rainfall
       reducing the residence time of the lake. The average rainfall for the 1997-1998 period was 66.5
       inches. The graph below clearly shows the low chlorophyll grouping in 1997-1998.


Response: The Department appreciates this information. The final Chla target was based on achieving a Chla-TSI
of less than 52.5. Based on the TSI calculation methodology, a Chla of 11.8 ug/L results in a Chla-TSI of 52.3. The
referenced number of 4.5 ug/L was not used to develop the final TMDL. The TMDL report will be modified to

                                                         32
Florida Department of Environmental Protection
  DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),



reflect your information and to clarify how the final recommend Chla concentration was developed. The
Department has revised the recommended BOD5 TMDL from 1.34 mg/L to 2.00 mg/L as recommended and the
percent reduction has been recalculated.
Ms. Kelli Hammer Levy
Pinellas County Department of Environmental Management
August 27, 20009
Page Three


    4. Section 3.2.1 – The applicable Freshwater criterion for DO from the State Water Quality
       Standards is as follows:”Shall not be less than 5.0. Normal daily and seasonal fluctuations above
       these levels shall be maintained.” This document states the DO shall not be less than 4 mg/L.

Response: The Department appreciates this information. The language for the marine DO criterion was
inadvertently placed into the report and the correct language has been inserted. At no time was the marine
criterion used to either establish the impairment in Alligator Lake or to develop the draft TMDL.

    5. Section 3.5, page 11 – Which 5-year period was used to calculate the historic TSI? How do 5 TSI
       units equal the assimilative capacity of the lake, allocations for future growth, and the Margin of
       Safety (MOS)? A TSI increase of 10 points is equivalent to a doubling in Chla. Consequently a
       5 point increase in TSI would represent a 50% increase in chla. A 5 point margin of safety is not
       warranted according to the Chl-a graph above.

Response: The period used to calculate the annual average historic minimum TSI of 47.5 was the five year period
of 1994 – 1998. The MOS does not have a 5 TSI unit allocation. The individual allocations for assimilative capacity,
future growth, and MOS have not been separated at this time. The total allowable assimilative capacity is the 10
TSI unit increase over the historic TSI target of 47.5. As such, any years with a TSI over 57.5 would be considered
as exceeding the allowable assimilative capacity. There were multiple years during the verified period that
exceeded a TSI of 57.5 and the lake was listed as impaired for historic TSI. In order to restore sufficient assimilative
capacity that would allow some room for future growth, account for uncertainty, and provide for a MOS, the
Department has been establishing a 5 TSI unit reduction (50%) of the total allowable assimilative capacity as the
target for lake restorations. As stated above, this 50% reduction in Chla below the threshold for impairment
restores 50% of the assimilative capacity, allows for future growth and includes an implicit MOS. If in this case, the
local stakeholders believe that only restoring 50% of this historic assimilative capacity is
insufficient to account for all of these factors, the Department would be willing to establish the restoration target
at a TSI below 52.5.

    6. Section 3.6, page 11 and Section 5.1, page 23 – The Department states that the percent
       reduction for TN and Chl-a concentrations were calculated based on the highest annual mean
       concentration for the verified period. What is the basis for using the highest mean concentration
       versus the median value over the verified period? The median TN value for the year 2000 is
       0.92mg/L which shows that a small number of points have a significant impact on the mean. The
       long term median would be more representative of exiting conditions. Overall, there is
       inconsistency when using mean and median values which change from TMDL document to
       TMDL document.

Response: As the lake is impaired for both TSI and low DO, and the Department has linked nutrients to both of the
impairments, the final nutrient TMDL must address both impairments. Using the maximum verified period annual
means was an approach used to provide additional MOS to account for the uncertainty that achieving a TSI of 52.5
would restore both the historic trophic state and result in meeting standards for DO. However, the Department
agrees that consistency is important and has revised the concentrations that are reduced to be the average
concentration over the verified period instead of the worst-case year. This resulted in changing the 1.08 mg/L TN
value to 0.88 mg/L. The percent reduction changed from 24 percent to 19 percent.

                                                          33
Florida Department of Environmental Protection
  DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),




Ms. Kelli Hammer Levy
Pinellas County Department of Environmental Management
August 27, 20009
Page Four


    7. Table 3.1, and 3.2, pages 12 through 15 – The methodology include selecting sites with a
       Landscape Development Intensity Index (LDI) score of 2 or below. The documentation provided
       for the LDI indicates that it is a project that is still being researched and tested. Why is this
       methodology being employed to develop TMDLs? LDI scores of 1-2, as proposed, are located in
       areas without urban development – natural lands such as forests, recreational open space, and
       other natural lands. It is not clear what sites are included in each method for the reference
       targets. Please provide information on the reference site locations.

Response: Please note that the LDI-based reference method was not used in the direct determination of
the Alligator Creek TMDL, but was utilized for comparative purposes with the method that was used. The
reference method based on Department Assessments of “Impaired” vs. “Not-Impaired” provided more
conservative TN target concentrations and should provide stakeholders a greater level of confidence. The
Department-Assessment based reference sites for Tampa Bay Group 1 include Direct Runoff to Bay
(WBIDs 1603, 1609, and 1676), Big Bayou – Basin W (WBID 1709), Hillsborough Bay-Lower (WBID
1558D), Hillsborough Bay-Upper (WBID 1558E), Papy’s Bayou (WBID 1661G), Frenchmen’s Creek
(WBID 1709), and Bishop’s Harbor (WBID 1797B).

    8. Method 2 provides equal weight to each sample, which does not account for any seasonal
       variability. Method 4 does not specify if all 4 samples were collected in different seasons. There
       appears to be no relationship between tables 3.1 and 3.2. The numbers presented in the tables
       do not correspond to one another. Additionally, using method 2 results in an arbitrary TN
       concentration that is not linked to a TN load. What is the assimilative capacity of the lake?
       Without understanding the assimilative capacity of the lake and the loadings to the lake, a TMDL
       cannot be developed. There is a long term USGS gage on the main channel of the creek, water
       quality data for both the creek and the lake, and long term lake level data that can be used for
       such assessments.

Response: Although there was no requirement for a minimum number of samples for each season, one
observation was that the samples were generally spaced throughout the year to capture monthly
variations, whether there were 6 samples during a given year or 30+ samples during a given year. The
Department agrees that, if at all possible, it is preferable to observe and incorporate seasonal variation
into the target determination process.

The Department believes that the best way to move forward in restoring water quality in Alligator Creek is
to establish the concentration-based TMDL and to calculate the source-specific allowable loads to the
waterbody during the BMAP development process. The Tampa Bay Nitrogen Management Consortium is
scheduled to submit to the Department a draft update of the Reasonable Assurance (RA) Plan for Tampa
Bay by September 25, 2009. The RA plan will provide load allocations to individual entities discharging to
the bay, which have not yet been completed. Up until this time, the total nitrogen loadings to Tampa Bay
have been calculated and evaluated for each of the major bay segments, as these are the assessment
units used for tracking progress in meeting the resource-based water quality targets. Preferably, the
calculation of allowable loads to the smaller impaired water segments for which TMDLs have been
developed, like Alligator Creek, would also be viewed for consistency at a larger scale, which would be
completed after the review and approval of the updated RA plan, to ensure that consistent flow estimates
and other assumptions are used in both processes.

                                                    34
Florida Department of Environmental Protection
  DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),




    9. TN and Chla references chosen by the Department were based on average station medians, but
       the concentrations previously chosen to reduce from (see paragraph above) were annual means.
       Please explain the variability with regard to using mean versus median.
Ms. Kelli Hammer Levy
Pinellas County Department of Environmental Management
August 27, 20009
Page Five


Response: The annual “median”, which is less susceptible to influence by an outlier or uncharacteristic
high or low values, was used to characterize a given station. Although a minimum of 4 samples had to be
collected per year to assign a WBID station median, most stations included had over 15 samples. Once
we have determined the median concentration of a parameter for a given station, we have hopefully
mitigated the effect of extreme values for that station. The goal at this point was to provide equal weight
to all stations when calculating an “average median value” for a year. Thus, the average median value
was calculated as a straight arithmetic average, with no attempt to remove the impact of “extreme
stations.” In fact, at this point, high concentration stations were treated as “hot spots.”

    10. Table 3.2 presents Chla values in mg/L. The correct unit of measure should be ug/L.

Response: The draft report included the noted error and the TMDL document has been corrected.

    11. Section 4.2.1 refers to appendix C. No Total Nitrogen data are presented.

Response: The TMDL presently states that ‘water quality data can be found in Appendix C’. Appendix C
presently has flow, Nitrate, and Ammonia data for the City of Clearwater Master Reuse System. No TN
data were available at the time of this report.

    12. Table and Figure 4.1 – These facilities are not addressed in the load allocation.

Response: If a facility does not directly discharge into the surface water being assessed, no wasteload
allocation is determined. It is the understanding of the Department that the listed facilities do not
discharge into either Alligator Creek or Alligator Lake. The following text has been added to the TMDL to
clarify this point; “Please note that because the facilities listed in Table 4.1 do not discharge directly into
Alligator Creek or Alligator Lake, they will not be included as point sources in the TMDL and subsequently
will not receive a load allocation. They are supplied here for informational purposes only.”

    13. Runoff tables in Chapter 4 states that forests are 27%, wetlands are 9.8% and water is 3.8%
        impervious. Please explain. Effective rainfall is 55.95” but the average precipitation is 49.43.”
        Please explain. Please clarify if the two right-hand columns present annual data.

Response: The notation at the end of Table 4.4 referring to an effective rainfall of 55.95 inches per year
was an error and has been removed from the document. The impervious percentages were a hold-over
from a previous table and have been corrected with impervious percentages that match the landuse.

    14. Table 4.5 uses EMCs to calculate TN and TP loadings. Why were available flow and
        concentration data not used to calculate these loadings? Are the loadings based on actual
        rainfall data (available through SWFWMD)? These tables can be used as part of a larger study to
        target areas for further evaluation for source controls, but are not a demonstration of pollution.
        What was the purpose of this evaluation since the information was not used in the development
        of the TMDL? Additionally, there is an approved watershed plan for Alligator Creek including a
        water quantity and quality model.



                                                      35
Florida Department of Environmental Protection
  DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),



Response: The EMC data were used in Table 4.5 in an attempt to illustrate the relative contributions
from the different land uses. As you noted, it was not used in determining the TMDL. The rainfall is
based on gage data from local Tampa Bay stations available on the SWFWMD web site.


Ms. Kelli Hammer Levy
Pinellas County Department of Environmental Management
August 27, 20009
Page Six


    15. Section 5.1. See previous comments related to development of an assimilative capacity and for
                           nd
        estimating loads. 2 paragraph – please revise paragraph.

Response: The Department believes that the best way to move forward in restoring water quality in both
Alligator Creek and Alligator Lake is to establish a concentration-based TMDL based on achieving an
annual average trophic state of 52.5 in Alligator Lake and to calculate the source-specific allowable loads
to the waterbody during the BMAP development process. The Tampa Bay Nitrogen Management
Consortium is scheduled to submit to the Department a draft update of the Reasonable Assurance (RA)
Plan for Tampa Bay by September 25, 2009. The RA plan will provide load allocations to individual
entities discharging to the bay, which have not yet been completed. Up until this time, the total nitrogen
loadings to Tampa Bay have been calculated and evaluated for each of the major bay segments, as
these are the assessment units used for tracking progress in meeting the resource-based water quality
targets. Preferably, the calculation of allowable loads to the smaller impaired water segments for which
TMDLs have been developed, like Alligator Creek and Alligator Lake, would also be viewed for
consistency at a larger scale, which would be completed after the review and approval of the updated RA
plan, to ensure that consistent flow estimates and other assumptions are used in both processes. The
draft TMDL document has been revised to reflect this information.

    16. Section 5.1.1, page 24. Comparing an average BOD to a median BOD reference is a valid
        assessment. The paragraph states that an equal weight was given to each sample which does
        not account for seasonal variability. Also table 3.2 shows a reference BOD median target of
        1.63mg/L, not 1.67mg/L. Note that the laboratory Minimum Detection Limit (MDL) is 2.0mg/L.

Response: This TMDL document no longer has a BOD target. The points that you raise in the above
comment provide part of the reason and the BOD data are currently being reviewed.

    17. Section 5.1, page 24, states that the reference approach will be used to calculate a creek target
        BOD5. The target proposed is 1.67mg/L, while table 3.1 shows a reference BOD target of 1.63 for
        non-impaired freshwater Tampa Bay Tributaries. Table 5.2 shows a BOD TMDL for the lake of
        1.35mg/L but the lowest annual mean shown in 5.1 is 1.34mg/L. Which are the correct values for
        the lake and the creek? In any case, the targets are well below the 2.0mg/L MDL for BOD. Also
        the non-impaired reference BOD concentration found in table 3.2 is 2.5mg/L in freshwater creeks
        and 3.24mg/L in lakes. Please note that the Lake Tarpon Canal and Moccasin Creek Tidal Draft
        TMDL document mentions the laboratory detection limit of 2.0mg/L and accepts this BOD value.

Response: This TMDL document no longer has a BOD target. The points that you raise in the above
comment provide part of the reason and the BOD data are currently being reviewed.

    18. Table 5.2 also shows a lake target Chla value of 11.8ug/L. Please explain this number as well as
        the equation used to determine the percent reduction. What are the observed values? If TSI is
        met for the lake, TN and Chla targets should not be considered.




                                                    36
Florida Department of Environmental Protection
  DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),



Response: See also the responses to comments 1, 3, 5, and 6 for additional details. Since Group 1/Cycle 1, the
Department has been using a 5 TSI unit reduction from the threshold of impairment to establish the restoration
target for lakes that are impaired for TSI. In this case, the impairment threshold was a TSI of 57.5; a 5 TSI unit
reduction establishes a restoration target TSI of less than 52.5. The TSI calculation methodology is based on
calculating the average of a nutrient-TSI and a Chla-TSI. A chlorophyll a concentration of 11.8 ug/L is equivalent to
a Chla-TSI of 52.3.

Ms. Kelli Hammer Levy
Pinellas County Department of Environmental Management
August 27, 20009
Page Seven


Percent reduction is calculated as:

((number to reduce from – TMDL)/number to reduce from) * 100

The report will be modified to include this equation and a table of the numbers used.

Any given TSI can be achieved with a range of nutrient and Chla concentrations. If the desired TSI is not
linked to the desired nutrient and Chla concentrations the TSI value might be met, but undesirable
conditions could exist in the lake. For example, Florida has impaired lakes that have TSIs below the
threshold, but there is an imbalance in the flora or fauna of the lake and it is not meeting designated uses
due to either a dominance of blue-green nitrogen fixers, excessive macrophytes causing light limitation,
application of herbicides keeping the Chla at very low levels such that the nutrient-TSI is high, but the
Chla-TSI is low (and the average of the two meets the threshold), or some combination of factors. To
avoid situations such as these, the Department is publishing the concentrations of nutrients and Chla that
result in the desired TSI.

    19. Section 5.1.2 compares TN concentrations from the same day for Alligator Creek and Alligator
        Lake. This is not appropriate as it doesn’t take into account loading, residence time, or nutrient
        assimilation in the lake. What ratios are being used for the comparison of the creek versus the
        lake?

Response: The Department used the ratios to simply determine (over time) if the concentration of TN in the lake
was consistently less than the concentration in the creek. As these concentrations over-time are a reflection of the
end-points of the loading, residence times, and nutrient assimilation of each water body, the Department used
them to determine if it was reasonable to establish a higher nutrient TMDL for the creek than for the lake. As a
result of these comments and the County’s request to be consistent with other TMDLs, the Department has
established the same TN concentration (0.72 mg/L) for the creek as required to restore the downstream lake.

    20. Page 26 - The Department states there are not enough BOD data to use the ratio approach but
        still applies this method to determine target lake BOD concentrations. As stated it is not an
        acceptable method due to the lack of data.

Response: The Department has removed the BOD TMDL for the creek as not necessary and modified the BOD
TMDL for the lake to be 2.0 mg/L as suggested by the County.

    21. The entire analysis is based on concentrations when loadings should be the focus as stated on
        page 28 in the load allocation. No loads were presented, nor was an assimilative capacity
        determined.



                                                         37
Florida Department of Environmental Protection
  DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),



Response: As stated in response to comment 5 above, specific allocations of the assimilative capacity have not
been made at this time. The specific allocations will be established as a part of the BMAP process. As pointed out
in the draft document, TMDLs do not need to be expressed as loads. TMDLs can be and have been adopted as
concentrations in Florida.

    22. Page 29 - Please clarify the reference to Appendix A. Also please explain how a reduction in TN
        concentration (since no loads were calculated) would result in a DO concentration that matches
        targets.

Ms. Kelli Hammer Levy
Pinellas County Department of Environmental Management
August 27, 20009
Page Eight


Response: What was previously Appendix A has been removed and now Appendix A correctly refers to
Background Information on Federal and State Stormwater Program. The Department believes that the
best way to move forward in restoring water quality in Alligator Lake and Alligator Creek is to establish the
concentration-based TMDL and to calculate the source-specific allowable loads to the waterbody during
the BMAP development process. The Tampa Bay Nitrogen Management Consortium is scheduled to
submit to the Department a draft update of the Reasonable Assurance (RA) Plan for Tampa Bay by
September 25, 2009. The RA plan will provide load allocations to individual entities discharging to the
bay, which have not yet been completed. Up until this time, the total nitrogen loadings to Tampa Bay
have been calculated and evaluated for each of the major bay segments, as these are the assessment
units used for tracking progress in meeting the resource-based water quality targets. Preferably, the
calculation of allowable loads to the smaller impaired water segments for which TMDLs have been
developed, like Alligator Lake and Alligator Creek, would also be viewed for consistency at a larger scale,
which would be completed after the review and approval of the updated RA plan, to ensure that
consistent flow estimates and other assumptions are used in both processes.

    23. Page 30 – The BOD TMDL was improperly established. Please refer to the comment made
        above for page 26. Under Section 6.5 states that there will be a 28.6% reduction in TN loadings
        and 16.5% BOD loading reduction for Alligator Creek. No loadings were established.

Response: The BOD target and associated TMDL have been eliminated and this reference to BOD has
been removed. As pointed out in the draft document, TMDLs do not need to be expressed as loads.
TMDLs can be and have been adopted as concentrations in Florida.

    24. There are 5 layers of Margin of Safety (MOS) employed in the determination of this TMDL:
    • Restore numbers to period of record lows – which were atypical El Nino and La Nina years
    • IWR TSI target is 60. Historical Alligator Lake TSI is 47.5. IWR allows for a 10 point increase over
        period of record, which would give us a 57.5 target TSI. For MOS, Department arbitrarily picked
        52.5 as target TSI for Alligator Lake
    • Reference method used is the most conservative
    • Percent reduction is based on achieving the 52.5 TSI and the worst case scenario years.
    • While calculations show that Alligator Lake can handle an input of 1.10mg/L TN coming in from
        Alligator Creek, a margin of safety was used – the Department reverted back to the reference
        table value for freshwater creeks TN (which is incorrectly listed as 0.86mg/L and should read
        0.97mg/L)

    While Pinellas County understands the need for a margin of safety to ensure future compliance, using
    excessive margins of safety will result in percent reduction numbers that are not representative of
    actual conditions, but also cost-prohibitive and unattainable. Please see graph below which shows
    the Alligator Lake TSI has been improving over the verified period.

                                                        38
Florida Department of Environmental Protection
  DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),




Response: The reference TN was determined three ways, with the most conservative value of TN
selected (0.97 mg/L was one of the least conservative). It is correct that this approach provides a margin
of safety to the TMDL, but conservative decision making provides added assurance that the load
reductions will have desired impact.




Ms. Kelli Hammer Levy
Pinellas County Department of Environmental Management
August 27, 20009
Page Nine


Cross Canal North (WBID 1625) – DO; Allen’s Creek Tidal (WBID 1604) – DO and Nutrients

    1. Please check the table of contents. There are incorrect appendices listed.

Response: The Appendices listed in the Table of Contents has been revised to reflect the TMDL document
contents.

    2. According to the May 14, 2009 Verified List, adopted by Secretarial Order, Cross Canal North (1625) is
       impaired for both DO and Nutrients and Allen Creek Tidal (1604) is impaired for DO. The title of the
       document states the reverse. Additionally, the causative pollutant for Allen’s Creek per the
       May 14, 2009 Verified List is Total Phosphorous while a WLA was developed for TN. Please explain.


Response: The title of the TMDL document has been changed to reflect the correct listed WBID impairments.
The most recent assessment indicated that elevated TN, not TP, was the causative pollutant for the low
dissolved oxygen in Allen Creek. Included in this assessment was observation that the TN/TP ratio was almost
always below 10 (indicating TN to be the limiting pollutant) throughout the verified period.

    3. Data comments:
       Allen’s Creek – sites 19-08, 19-09 are located in the freshwater WBID of Allen’s Creek (1604B)
       and should not be considered in this TMDL. Site 19-10 is a freshwater site located within the tidal
       WBID. All of the readings at this site are below the accepted 2.17 salinity criterion. This site
       should be excluded from the tidal WBID. Site 19-02 has data available since 1991. Please
       reassess accordingly.


Response: A check of stations 19-08 and 19-09 indicated that these stations are part of WBID 1604B,
not WBID 1604, and the change will be made to the TMDL document and the IWR database. The
removal of these stations had no impact on either the assessment call for dissolved oxygen for WBID
1604 (it remains impaired) or the required percent reduction (which is based on results at another
station). A review of the salinity data at Site 19-10 revealed that it has been submitted to the Department
with erroneous latitude and longitude, thus explaining why it had low salinity in a region with higher
salinity. Our understanding is that Pinellas County has agreed to make necessary changes for future
data submittals. But the station, once moved, is still within the boundaries of the Allen Creek freshwater
segment. The salinity breakpoint between freshwater vs. marine is 2.7 ppt. Nevertheless, if a future
assessment indicates a freshwater station is located within the Allen Creek Tidal WBID, the Allen Creek
boundaries will be re-delineated as appropriate.


                                                    39
Florida Department of Environmental Protection
  DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),



Although Station 19-02 has data since 1991, for assessment purposes, only verified period data is used
(years 2000 through 2007). For the years 2000, 2001, and 2002, there are no data for station 19-02 in
the Florida STORET database.

    4. Cross Bayou - Site 21FLPDEM-24-02 was under construction and booms were blocking flow as noted
       in the field comments for 5/24/04. These readings should be removed from the Cross Bayou verified
       period data. Additionally, site 24-03 has been under construction since November 27, 2006 (per Sue
       Moore, FDOT District 7). There is an FDOT construction site impairing flow just upstream of the site.
       Data for this site should be removed since that date. Please reassess accordingly.

Response: Data from these stations were supplied to Florida STORET by Pinellas County. Neither comments
nor qualifiers were observed for this station (indicating that the data was not representative of normal ambient
conditions). If ambient water quality data submitted to Florida STORET is known to not have been

Ms. Kelli Hammer Levy
Pinellas County Department of Environmental Management
August 27, 20009
Page Ten


representative of ambient conditions, Florida STORET and FDEP Watershed Assessment Section should be
notified by the data provider. To ensure that unrepresentative data are not used in the assessment process,
please contact the FDEP’s Watershed Assessment Section. The TMDL percent reduction is a function of the
station and year with the greatest median TN concentration, and for Cross Canal North that is station 24-03.
But the high concentrations years at this sample station were 2003 (TN median=1.55 mg/L), 2004 (TN median =
1.66 mg/L), and 2005 (TN median = 1.61 mg/L). Based on the above comment which indicates construction
activities began on Nov. 27, 2006, the station’s elevated TN was not influenced by these activities. In fact, in
2006 the station 24-03 TN median was 1.2 mg/L.

    5. Section 3.2.2, page 11, refers to the Tampa Bay Estuary Program chlorophyll-a targets and applies the
       Old Tampa Bay target of 9.3ug/L to Allen’s Creek and Cross Bayou. This is not a relevant target as
       Chlorophyll-a targets were established for Tampa Bay to protect seagrass resources. It should not be
       applied to tidal creeks where chemical and physical variability, residence time, and color have effects
       on Chla not seen in the Bay. Also this target would be overly protective as it does not take into account
       the assimilative capacity of the Bay. Please refer to the Tampa Bay Estuary Program’s “Estimating
       External Critical Nitrogen Loads for the Tampa Bay Estuary: An Empirically Based Approach to Setting
       Management Targets” (1996) available in the 2002 Reasonable Assurance Plan documents and the
       2009 update (in press).

Response: The Department recognizes that the Old Tampa Bay Chla target of 9.3 ug/L, which was used as a
target for establishing the TMDL, was originally developed for Old Tampa Bay as a water quality target for
making resource-based management decisions for seagrass restoration. As the impaired tidal segments have
direct exchange of water with Old Tampa Bay, we believe that the bay chlorophyll a target is reasonable
information to consider for establishing a target in these areas. It must be emphasized here that the limiting
factor was not the Old Tampa Bay target, but the total nitrogen target for Allen Creek and Cross Canal North
was primarily determined through use of the reference method, which utilizes the average station median total
nitrogen concentrations in Class III estuary WBIDs ‘Not-impaired” in the Tampa Bay watershed.

    6. Table 3.2 – Are the numbers presented means or medians?

Response: For Table 3.2 the total nitrogen concentration is the annual median and the chlorophyll-a
concentration is an annual average (annual quarter concentrations given equal weight). The TMDL document
has been revised to indicate this.
                                                    40
Florida Department of Environmental Protection
  DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),




    7. The R2 values of the Chla-TN relationships show no valid relationship in Cross Canal North and only a
       weak relationship in Allen’s Creek. Using annual means in linear regressions needlessly removes
       variation in the analyses. If data could be correlated, for example collected on the same day or in the
       same season, then test for correlation and if so, then use the mean of the points. If independent then
       include in the regression as separate data points. The sample size used in many of the regression
                                                                                                             2
       analyses seems low, given the potentially high variability of water quality data. There should be r
       criterion or cut off points for using linear regressions in TMDL’s to set targets. In many field studies an
         2
       r = 0.70 is the criterion. 95% confidence limits for linear regressions should be included in figures and
       tables. The TN targets estimated from the regression should include upper and lower 95% confidence
       limits. The TN target should be a range, not a single number.




Ms. Kelli Hammer Levy
Pinellas County Department of Environmental Management
August 27, 20009
Page Eleven

                        2
Response: The low R for the regression relationship between TN and Chlorophyll-a is an indication that there
are several factors affecting Chlorophyll-a (in addition to Total Nitrogen, these include phosphorus, wind, light,
flow rate, etc.). By graphing annual averages rather than individual results (which was also attempted) it is
sometimes possible to dampen out the level of influence of these other factors. It is interesting to note that,
                                    2
although the regression equation R for these and other estuaries varied (from 0.1 to 0.6 in Tampa Bay
estuaries), the TN target remained consistent (between 0.9 and 1.0 mg/L). Never-the-less, the dominant factor
in determining these nutrient targets and TMDL was the reference condition, which placed the Allen Creek and
Cross Canal North TN target at 0.75 mg/L.

    8. The more conservative targets for Allen’s Creek are applied to Cross Bayou – This is an additional
       burdensome margin of Safety. The document states that Allen’s Creek and Cross Bayou are similar
       systems; however, Allen’s Creek is a natural tidal tributary system and Cross Bayou Canal is a linear
       man-made upland cut ditch.

Response: It is agreed that the two waterbodies have different hydraulics. The TMDL document is noting that
there is an array of conditions that the reference method took into consideration; i.e. station median
concentrations within several “not impaired” Class III estuaries were used to determine the target rather than
focusing on one type of water body. The goal is the establishment of a fair target that can be applied across a
range of hydraulic conditions.

    9. Table 3.3 – Where are the WBIDs used in this reference table? Why are Group 1 Tampa Bay Tributary
       Waters being compared to Tampa Bay open water WBIDs?

Response: The reference sites for Tampa Bay Group 1 include Direct Runoff to Bay (WBIDs 1603, 1609, and
1676), Big Bayou – Basin W (WBID 1709), Hillsborough Bay-Lower (WBID 1558D), Hillsborough Bay-Upper
(WBID 1558E), Papy’s Bayou (WBID 1661G), Frenchmen’s Creek (WBID 1709), and Bishop’s Harbor (WBID
1797B). As stated in the previous response the goal is the establishment of a fair target that can be applied
across a range of hydraulic conditions.

    10. Chapter 3 and Chapter 4 refer to Mullet Creek and Bishop Creek multiple times. Please correct.

Response: Two cases were found and corrected.

                                                     41
Florida Department of Environmental Protection
  DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),




    11. Figure 4.1 shows a “non-surface water discharge” at Clear Channel Outdoor, Inc. Please explain why it
        is showing on a figure presenting wastewater treatment plant facilities.

Response: The presence of Clear Channel Outdoor, Inc, (which does not discharge into surface water and
does not require or have a NPDES permit) in Figure 4.1 might be misinterpreted. Figure 4.1 will be revised with
Clear Channel Outdoor removed.

    12. Section 4.2.2 states that EMCs are used to calculate nutrient contributions. Why are available flow and
        concentration data not being used? They would provide a far more accurate representation than
        EMCs. What information was used from the Duncan study in Australia and how is it relevant to Pinellas
        County waters?

Response: Flow and concentration data from the watershed is not used because the intent of the exercise was
to attribute different loads to different landuses. The use of EMCs, which are concentrations associated with
land uses, was determined to be a better approach. Also, flow and concentration results are typically
incomplete because they are grab samples and spot measurements. Using a spreadsheet based on rainfall
Ms. Kelli Hammer Levy
Pinellas County Department of Environmental Management
August 27, 20009
Page Twelve


attempts to incorporate some higher loads that may more typically be associated with rainfall events, although
in a modest way compared to more complex models.

    13. Table 4.3a and 4.3b state that forests are 27%, wetlands are 9.8% and water is 3.8% impervious.
        Please explain. Effective rainfall is 55.95” but the average precipitation is 49.43”. Please explain.
        Please clarify if the two right-hand columns present annual data.

Response: Table 4.3a and 4.3b provide the incorrect impervious areas for land uses and the Tables
have been corrected in the TMDL document. The footnote referring to an effective rainfall of 55.95 is in
error and has been removed in the document.

    14. Section 5 – Assimilative capacity and loads were not determined.

Response: This is correct, the assimilative loads and capacity were not determined. The Department
believes that the best way to move forward in restoring water quality is to establish the concentration-
based TMDL and to calculate the source-specific allowable loads to the waterbody during the BMAP
development process. The Tampa Bay Nitrogen Management Consortium is scheduled to submit to the
Department a draft update of the Reasonable Assurance (RA) Plan for Tampa Bay by September 25,
2009. The RA plan will provide load allocations to individual entities discharging to the bay, which have
not yet been completed. Up until this time, the total nitrogen loadings to Tampa Bay have been
calculated and evaluated for each of the major bay segments, as these are the assessment units used for
tracking progress in meeting the resource-based water quality targets. Preferably, the calculation of
allowable loads to the smaller impaired water segments for which TMDLs have been developed, like
Cross Canal North and Allens Creek, would also be viewed for consistency at a larger scale, which would
be completed after the review and approval of the updated RA plan, to ensure that consistent flow
estimates and other assumptions are used in both processes.

    15. 5.2 - Nutrient data are available and should be used instead of EMCs.

Response: The use of EMCs, which are concentrations associated with land uses, was determined to
be a better approach. Also, flow and concentration data are typically incomplete because they are grab
samples and spot measurements. Using a spreadsheet based on rainfall attempts to incorporate some
                                                     42
Florida Department of Environmental Protection
  DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),



higher loads that may more typically be associated with rainfall events, although in a modest way
compared to more complex models.

    16. Section 5.3 states that the percent reduction calculation is based on the worst year median TN
        (maximum annual station median). This is not a fair representation of all site conditions and
        presents an undue burden to the permit holders. Flow and water quality data are available for
        assessing loads.

Response: The percent reduction is based on the sample station (with a substantial number of samples)
with the highest annual median concentration throughout the verified period. A single data point may be
reason for concern about being too conservative, but it is felt that the highest annual median for the 7
year verified period is the worst case scenario that the TMDL needs to address. Furthermore, if during
the implementation the target concentration is achieved before the percent reduction is achieved, we can
revise the percent reduction.

    17. 6.4 – Three margins of safety were used in the determination of this TMDL. Please refer to the
        comment in the Alligator Creek TMDL about burdensome and excessive margins of safety.
Ms. Kelli Hammer Levy
Pinellas County Department of Environmental Management
August 27, 20009
Page Thirteen


Response: Several methods were used to determine the target concentration. Choosing the most
conservative option at every point of decision should not be misconstrued to be compounded.

    18. Appendix A – Sample Stations and Median Concentration Data. This appendix is missing.

Response: This Appendix had been listed in error. Reference to Sample Stations and Median
Concentration Data has been removed from the document.

Moccasin Creek Tidal (WBID 1530) and Lake Tarpon Canal (WBIDs 1541A and 1541B) – DO

    1. Section 1.1- Why is the most recent Verified List, adopted by secretarial order on May 14, 2009, not
       being referenced?


Response: The date listed is in error and will be corrected to read May 14, 2009.

    2. Section 3.2.2 - This section refers to the Tampa Bay Estuary Program Chlorophyll-a targets and applies
       the Old Tampa Bay target of 9.3ug/L to Moccasin Creek Tidal and Lake Tarpon Canal. Please refer to
       the comment made above in the Cross Bayou and Allen’s Creek comments regarding the Estuary
       Program’s Chlorophyll-a targets. In addition, a marine Chla target should not be applied to the Lake
       Tarpon fresh WBID (1541A).


Response: The Department recognizes that the Old Tampa Bay Chla target of 9.3 ug/L, which was used as a
target for establishing the TMDL, was originally developed for Old Tampa Bay as a water quality target for
making resource-based management decisions for seagrass restoration. As the impaired tidal segments have
direct exchange of water with Old Tampa Bay, we believe that the bay chlorophyll a target is reasonable
information to consider for establishing a target in these areas.
It must be emphasized that the Total Nitrogen target for Lake Tarpon Canal and Moccasin Creek TMDLs were
primarily determined through use of the reference method, which focuses on determining a total nitrogen level
that is locally attainable and that meets the water quality requirements of these Class III estuaries.


                                                   43
Florida Department of Environmental Protection
  DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),



    3. Lake Tarpon marine and Moccasin Creek Marine data should not be paired as they are two entirely
       different systems. The Lake Tarpon marine receives influx from Lake Tarpon based on the SWFWMD
       control structure discharge. It is an upland manmade cut ditch. Moccasin Creek is a natural tributary
       system that largely drains residential land uses.

Response: The target concentration based on median station TN concentrations, is based on an array of
conditions, i.e. station median concentrations within several “not impaired” Class III estuaries were used to
determine the target rather than focusing on one type of waterbody. The goal is the establishment of a fair
target that can be applied across a range of hydraulic conditions.

    4. There are not enough points in the regression analysis presented on page 10 for the relationship to be
       valid. Invalid Chla targets should not be used to obtain TN concentration targets when there is no
       evidence of a valid relationship. See previous discussion, page 7, on regression analysis.
                                                                             2
Response: It is interesting to note that, although the regression equation R for these and other estuaries
varied (from 0.1 to 0.6 in Tampa Bay estuaries) and the data count is lower than preferable, the TN target
remained consistent (between 0.9 and 1.0 mg/L). Never-the-less, the dominant factor in determining these
nutrient targets and TMDL was the reference condition.

Ms. Kelli Hammer Levy
Pinellas County Department of Environmental Management
August 27, 20009
Page Fourteen


    5. Table 3.3 – What are the site descriptions and locations for the data presented in Table 3.3?
       Appendix A presents site locations for South Florida canal stations and are not applicable to
       urban stream systems. Please see example map and table of site location descriptions below. All
       of the stations except for one are classified as canals.

Response: At present there is not a separate category relative to urban canals, thus when developing
the reference WBIDs there was no intention to divide the WBIDs based on this category.

    6. Page 14 - Why were the TN targets for Tampa Bay and Tampa Bay Tributaries averaged?

Response: The original goal in determining reference concentrations was to determine a regional area
from which to obtain reference WBIDs that was geographically similar to those WBIDs for which TMDLs
were being assessed. Part of the exercise involved looking to determine if there was a substantial
difference in TN, TP, Chl-a, or other parameters in Tampa Bay (Group 1) vs. Tampa Bay Tributary (Group
2) WBIDs determined to be “Not Impaired” by Department IWR listing process. The average median
sample station nutrient concentrations from “not impaired” Tampa Bay Tributary WBIDs were observed to
be generally higher than the Tampa Bay WBIDs concentrations. These concentrations were averaged in
the case where the Tampa Bay estuary reference target could not practically be applied to a fresh
headwater stream. Note that in several TMDLs when a freshwater section empties into an estuary, the
lower estuary limits are applied to the freshwater portion to be protective of the estuary. In this case the
Freshwater target was set as the average of the Tampa bay TN reference and the higher Tampa bay
Tributary TN Reference.

    7. Section 4.2.1 – The Lake Tarpon Canal is owned, operated, and maintained by SWFWMD.
       SWFWMD should be listed as a responsible entity for both WBIDs 1541A and 1541B.

Response: The responsible entities refer to those municipalities or organizations in the MS4 permit as a
permittee or co-permittee. The SWFWMD is not listed in that role. However, if the SWFWMD or any
other entities need to become involved in the BMAP process, they will be invited to participate.


                                                     44
Florida Department of Environmental Protection
  DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),



    8. Table 4.3a, 4.3b and 4.3c state that forests are 27%, wetlands are 9.8% and water is 3.8%
       impervious. Please explain. Effective rainfall is 55.95” but the average precipitation is 49.43”.
       Please explain. Please clarify if the two right-hand columns present annual data.

Response: These values are in error and have been corrected in the TMDL document. The 55.95” in the
footnote has also been removed.

    9. Section 4.2.2 states that EMCs are used to calculate nutrient contributions and state that they
       demonstrate the source of TN pollution. As previously mentioned on page 4. Why are available flow
       and concentration data not being used?

Response: The EMCs are better able to illustrate those land uses responsible for what loads. If there is
continuous Tampa Bay data available, it might perhaps be possible to extract this information. Note, the
EMCs here are used to illustrate which land uses are responsible for what percentage of the load.

    10. Section 5.3 states that the percent reduction calculation is based on the worst year median TN
        (maximum annual station median). This is not a fair representation of all site conditions and
        presents an undue burden to the permit holders. Also the target TN is a concentration when TN
        loads should be considered.
Ms. Kelli Hammer Levy
Pinellas County Department of Environmental Management
August 27, 20009
Page Fifteen


Response: The worst case station permits the establishment of a TMDL that has assurance that all
stations on the WBID throughout most conditions will meet the set standards.

    11. Page 25 – the premise of the Chla target is without merit as explained before. In addition, marine
        standards should not be applied to the freshwater portion of the Lake Tarpon Canal. According to
        the IWR, the freshwater Chla target is 20ug/L; the marine target is 11ug/L.

Response: The target for the marine water is applied to freshwater because it is not practical to believe
that the nitrogen load will be reduced during the short residence time within the fresh water portion. It is
reasonable to expect that the marine segment is downstream of the freshwater section is not
disadvantaged by the burden that needs to be reduced as well as its own watershed loads.

Bishop Creek Tidal (WBID 1569) – DO; Mullet Creek Tidal (WBID 1575) – DO and Nutrients

    1. Please check the table of contents. There are incorrect appendices listed.

Response: This incorrect reference has been eliminated in the TMDL document.

    2. Section 2.2 – The Department states there were only enough data to calculate Chla averages for 3
       years, but 4 years are calculated. Please explain.

Response: The 3 has been changed to 4 years in the text.

    3. Page 8 – Mullet Creek annual average in 2002 is 15.05ug/L but table 3.1 shows 14.05ug/L. Looking
       into data for that year, the median chla for Mullet Creek is only 4.45ug/L. The average for the year is
       being skewed by data 2 points. Additionally, three readings that were coded as “I” do not appear in the
       IWR raw data.

Response: The Department IWR data indicates a 2002 chlorophyll-a concentration of 14.05 ug/L. It is
important to note that the Chlorophyll-a annual average is calculated as the average of the seasonal averages.
                                                      45
Florida Department of Environmental Protection
  DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),



But, regardless of whether the average is 15.05 or 14.05 ug/L, the result is an average above the threshold of
11 ug/L. It is agreed that only a few high values can thus have a great impact on whether a waterbody is or is
not impaired. Please feel free to direct additional questions or concerns about data used in impairment
determinations to the FDEP’s Watershed Assessment Section.

    4. Section 3.2.2 - This section refers to the Tampa Bay Estuary Program Chlorophyll-a targets and applies
       the Old Tampa Bay target of 9.3ug/L to Bishop Creek Tidal and Mullet Creek Tidal. Please refer to the
       comment made above in the Cross Bayou and Allen’s Creek (page 7) comments regarding the Estuary
       Program’s Chlorophyll-a targets.

Response: The Department recognizes that the Old Tampa Bay Chla target of 9.3 ug/L, which was used as a
target for establishing the TMDL, was originally developed for Old Tampa Bay as a water quality target for
making resource-based management decisions for seagrass restoration. As the impaired tidal segments have
direct exchange of water with Old Tampa Bay, we believe that the bay chlorophyll a target is reasonable
information to consider for establishing a target in these areas. It must be emphasized again that the Total
Nitrogen target for Bishop and Mullet Creek TMDLs were primarily determined through use of the reference
method, which focuses on determining a total nitrogen level that is locally attainable and that meets the water
quality requirements of these Class III estuaries.

Ms. Kelli Hammer Levy
Pinellas County Department of Environmental Management
August 27, 20009
Page Sixteen


    5. There are not enough points in the regression analysis presented on page 10 for the relationship to be
       valid. Invalid Chla targets should not be used to obtain Nitrogen concentration targets when there is no
       evidence of a valid relationship. See previous comments related to regression analysis on page 7.

Response: The eventual TMDLs for Bishop and Mullet Creeks (Tidal) were based more on the reference
conditions. The graphical TN vs. Chla and regression equations, with the weak coefficient of determination, R2,
were used as a tool to determine the maximum TN load that the estuaries could discharge without potentially
impacting the Tampa Bay Chl-a targets. This concentration, for most estuaries in the region, was between 0.9
and 1.0 mg/L. The target concentrations determined by the reference method was far below this potential limit.

    6. Table 3.4 - The BODs for both WBIDs does not exceed the state screening levels of 2.1mg/L and the
       non-impaired Tampa Bay and Tampa Bay Tributary BODs are 1.5 and 1.32mg/L. There is no valid
       relationship between Chla and TN. There is no demonstration that either BOD or Chla is the causative
       pollutant, consequently this TMDL should be dismissed.

Response: The TMDL document has been revised so that there are no longer any TMDLs related to BOD.

    7. Table 3.3 - What are the site descriptions and locations for the data presented in Table 3.3?
       Appendix A presents site locations for South Florida canal stations and are not applicable to
       urban areas. Please refer to the comment made about these site locations under the Moccasin
       Creek and Lake Tarpon Canal TMDL above (pages 8-10).

Response: The WBIDs represented in the reference sites represent an array of locations in the Tampa
Bay group of WBIDs.

    8. Section 4.2.1 – The responsible entity for Bishop Creek Tidal and Mullet Creek Tidal is Safety
       Harbor only.

Response: A shape file overlaying the WBID boundaries was used to determine which areas were in the
region of which co-permitee, but this method may prove imprecise. The TMDL indicates that entities are
                                                    46
Florida Department of Environmental Protection
  DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),



only responsible for those storm water systems which it owns/controls. If all such systems in Bishop
Creek Tidal and Mullet Creek Tidal are under the control of Safety Harbor, then Safety Harbor is the only
responsible MS4 party.

    9. Table 4.3a and 4.3b state that forests are 27%, wetlands are 9.8% and water is 3.8% impervious.
       Please explain. Effective rainfall is 55.95” but the average precipitation is 49.43”. Please explain.
       Please clarify if the two right-hand columns present annual data.

Response: This table is in error and the TMDL document has been corrected. The reference to 55.95”
has been removed.

    10. Section 4.2.2 states that EMCs are used to calculate nutrient contributions. Why are available flow and
        concentration data not being used? See previous comments related to this analysis on page 4.

Response: The loads calculated in Table 4.3a and 4.3b were used to illustrate the probable major
sources of total nitrogen. These loads were not used in the calculation of the TMDL. It is quite possible
that, during the BMAP phase of the project, it may be determined that another method of estimating load
(including the use of recent local EMCs collected under an array of rainfall conditions) is determined. The
use of EMCs is preferred in contrast to normal ambient data because it captures the loads associated
Ms. Kelli Hammer Levy
Pinellas County Department of Environmental Management
August 27, 20009
Page Seventeen


with storm runoff and most data collection schemes, unless specifically directed at storm flow or unless
continuous in nature, will miss this component of flow.

    11. Section 5.3 states that the percent reduction calculation is based on the worst year median TN
        (maximum annual station median). This is not a fair representation of all site conditions and
        presents an undue burden to the permit holders. Also the TN target is a concentration when TN
        loads should be considered.


Response: The TMDL is responsible for bringing all sites in the WBID under compliance, where compliance
includes daily and seasonal fluctuations. A strategy that focuses on only an average of all sites may still miss
bringing the sites with the most exceedances into compliance.

    12. According to the IWR, the freshwater Chla target is 20ug/L; the marine target is 11ug/L.

Response: The Chl-a thresholds listed in the IWR is a screening tool to determine if a waterbody should
be listed for nutrients, but the Chla target can be regional in nature. There are many examples of this in
south Florida, including Tampa Bay. The Department investigates each site based on present and past
local information in the determination of final target concentrations.

Bishop Creek (WBID 1569) and Bishop Creek Tidal (WBID 1569A) – Fecal Coliforms

     1. Section 1.1 states both the freshwater portion (WBID 1569A) and the tidal portion (WBID 1569) of
        Bishop Creek were deemed impaired for fecal coliforms on the most recent verified list. This is
        incorrect. Only the tidal portion of Bishop Creek was declared impaired on the May 14, 2009 Verified
        List. While Pinellas County understands that the WBID was recently split, and that data supports
        impairment for 1569A, WBID 1569 (tidal) was listed based solely on 2 months of data collected in
        2008, outside of the verified period, which violates the term of the IWR.



                                                     47
Florida Department of Environmental Protection
  DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),



        Again, Table 2.2 summarizes exceedances in both of these WBIDs through June 2008. This shows
        only two months of sampling occurred in WBID 1569. Impairment cannot be determined based on data
        from two months of sampling outside of the verified period.


Response: Bishop Creek (1569) was listed for fecal coliform impairment in Cycle 1 as a single WBID polygon.
The WBID was divided into 1569 and 1569A in the second cycle assessment and both newly split WBIDs
inherited the listing decision from the first cycle assessment. For the Department not to develop a TMDL for
any one of these two WBIDs, we need to have sufficient evidence to show that they are no longer impaired.
However, the second cycle assessment did not provide this kind of evidence. For the tidal influenced segment
of the creek, although we only have data from two months, fecal coliform counts in 4 out of 5 samples collected
during the two months exceeded the assessment threshold. That was a very large percent exceedance rate.
The upstream portion of the creek also showed strong evidence of fecal coliform impairment. Out of 40
samples collected during the verified period, 29 samples showed exceedance. Based on the Impaired Waters
Rule (Chapter 62-303.420(7)(b), water segments shall also be included on the verified list if scientifically
credible and compelling information provides overwhelming evidence of impairment. For the Bishop Creek tidal
area, the overwhelming evidence comes from (1) the water was verified for fecal coliform impairment in the first
cycle assessment; (2) the second cycle assessment showed very high percent exceedance rate, and (3) the
upstream portion of the creek was verified for fecal coliform impairment in the second cycle assessment. Based
on this information, the Department developed a fecal coliform TMDL for the tidal portion of the creek. It should
be noted that the fecal coliform impairments in the tidal portion of the creek is part of the impairment for the
entire creek. The Department is not trying to imply that the fecal coliform impairment for the tidal portion is only
Ms. Kelli Hammer Levy
Pinellas County Department of Environmental Management
August 27, 20009
Page Eighteen


caused by the drainage areas that discharge to the tidal portion of the creek. The impairment in the tidal portion
of the creek will be addressed through controlling the fecal coliform loads from the entire Bishop Creek
watershed. This will address the impairments in the entire creek, in both the freshwater and tidal segments.

     2. Section 4.2.1, page 10 – Safety Harbor is not noted as one of the permitted entities responsible in this
        watershed. The jurisdictional breakdown in the Bishop Creek WBIDs is as follows:
        WBID 1569 – 100% Safety Harbor
        WBID 1569A – 61% Safety Harbor, 27% Clearwater, 12% Pinellas County


Response: The Department agrees with the County and will include Safety Harbor as one of the MS4
co-permittees in the TMDL report.

     3. Why is 2008 SWFWMD land use information not being used?

Response: The percent reduction needed to address the fecal coliform impairment for Bishop Creek was
based on data collected during a period from 2001 to 2008. It is more reasonable to use the land use from a
year that falls in between 2001 and 2008. The 2008 land use represents conditions at the end of the
aforementioned period, but may not be the best land use to represent the entire period of record used for this
TMDL. This is why the South West Florida Water Management District (SWFWMD) 2008 Land Use Coverage
was not used for the TMDL.

     4. Page 13 – The Department uses fecal coliform studies conducted in New York, Baltimore and Seattle
        when local studies are available. See the study conducted in Stevenson’s Creek by Whitlock, Jones,
        and Harwood in 2002 (attached). This study showed that sources of fecal coliform bacteria can vary
        greatly in an urban watershed and concluded that wild animal feces were identified as the dominant

                                                     48
Florida Department of Environmental Protection
  DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),



         source when fecal coliform levels were high. This study was the basis for the USA today newspaper
         article written by Watson in 2002, referenced in this paragraph. The article presents facts about dog
         feces in various watersheds throughout the country and does not take into account Dr Harwood’s
         conclusions.

Response: Because the ultimate purpose of a TMDL is to address pollutant loadings from anthropogenic
sources, all the loading calculations presented in Chapter 4 of the TMDL report are intended to focus on
the relative contributions of fecal coliform loads from human and/or human related sources. We did
mention the possible contributions from wildlife (as indicated by published studies, including the one from
Whitlock, et al. 2002 mentioned in your comments). However, because we didn’t have the needed data
to calculate accurately the loading from wildlife, we did not include the wildlife loading calculation in this
TMDL report. If the County can provide us with wildlife data, we can include the load calculation in the
report. It should be noted though that all the loading calculations in Chapter 4 of the report are for the
purpose of comparing the relative contributions from different sources. These calculations only reflect the
possible loadings that are produced within the watershed. No transport attenuation or bacteria death rate
was taken into consideration in the calculation. Therefore, these loadings are not necessarily the
loadings that eventually reach the receiving water. The final TMDL calculations presented in Chapter 5
and summarized in Chapter 6 are based on the in-stream fecal coliform concentration, which are not
influenced by the loading estimates presented in Chapter 4.




Ms. Kelli Hammer Levy
Pinellas County Department of Environmental Management
August 27, 20009
Page Nineteen


     5. The number of dogs can be obtained from the Pinellas County Department of Animal Services.

Response: The Department would appreciate it if the County can provide us with contact information to obtain
the number of dogs in the Bishop Creek drainage basin. But again, quantifying the fecal loading from dogs is
only meant to compare contributions from different sources. The final TMDL is not influenced by the
calculation.

     6. Septic tanks, page 15 –2009 DOH septic tank shapefile was provided to the Department on 5/21/2009.
        This file shows 9 septic tanks located in WBID 1569A and none in 1569. Only one of those septic
        tanks is located within 50 meters of the creek (48.5m). According to page 15, most of the coliform
        from septic tanks should be removed within 50 meters of the drainage field. Additionally, there is no
        reference for the estimated annual septic tank failure rate of 3.5% based on a 5 year timeframe for
        discovery.

Response: The Department agrees to use the data provided by the County and will update the septic
tank load calculation. Again, re-calculation of the septic tank loading will not influence the final TMDL.

Estimating the annual septic tank failure rate based on a 5 year timeframe was cited from the following
document:

Watershed Management Model User Mannual, Version 4.1 (1998). Rouge River National Wet Weather
Demonstration Project. Wayne County, Michigan.

     7. Sanitary Sewer overflows, page 17 – Why is the Department not utilizing the State Warning Point
        database to determine SSO frequency and the resulting loads? SSOs should be attributed to the
                                                     49
Florida Department of Environmental Protection
  DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),



         correct Wastewater Treatment Facility’s permit, not the MS4 permit. Additionally, per Culver et al.,
         there is no basis for that 0.5% leakage rate.

Response: The Department will inquire about the State Warning Point database to get the data and
recalculate the loading results from the sanitary sewer overflow. Again, this will not change the final
TMDL for Bishop Creek.

     8. Section 5.1 – The percent reduction approach using only the values above the criterion is biased and
        not an accurate representation of real conditions. For example, consider two water bodies A and B,
        both have 200 data points. A has 20 exceedances and B has 200 exceedances. Calculating the
        percent reduction based on only the exceedances can result in equal or greater percent reduction for
        A. Clearly, this is not an equitable method as B should receive a higher percent reduction due to the
        larger number of exceedances vs total number of samples. This presents an undue burden to the
        permitted entities.

         Table 5.1 on page 21 proposes a 64% percent reduction. If all of the data are used, the percent
         reduction is 54%. Even with a 5% Margin of Safety, this is still well below the proposed 64%. The
         adopted TMDLs become rule and are integrated into MS4 permits. Pinellas County cannot accept a
         percent reduction number obtained from a technically non-defensible method.


Response: Using only the data exceeding the water quality criteria, to calculate the final percent reduction,
requires a lower percent reduction for the permitted facilities than if all the data were used. The Impaired
Waters Rule methodology verifies the fecal coliform impairment when more than 10% of the samples exceed
the state criteria (with 90% confidence level based on the binomial distribution). If we are to use all the data, we
Ms. Kelli Hammer Levy
Pinellas County Department of Environmental Management
August 27, 20009
Page Twenty

                                                                                               th
will only allow less than 10% of the samples to exceed the state criteria, which means the 90 percentile of all
the data will be used as the existing condition when the percent reduction is calculated. The resulting percent
reduction to achieve the fecal coliform target was more than 80%. When only the data that exceed the state
                                                                          th
criteria are used, we apply the median value of these exceedances (50 percentile) to represent the existing
condition in calculating the final percent reduction, which resulted in 64%. This places less of a burden on the
permitted facilities than using all the data.

     9. Section 5.1.1 - Five samples collected in a two month period does not qualify as “overwhelming
        evidence.”

Response: Please see our response to comment No. 1.

     10. Section 5.1.3 Seasonality – Why were rainfall and flow data not compared when they are both
         available?

Response: Gaged flow measurements began in August 2006 and a large amount of the data used in the
TMDL were collected prior to this time. An analysis of rainfall and flow data may be more useful to undertake
during the BMAP process when additional flow data are available.

     11. “Livestock with direct access to the receiving water could also contribute to the exceedances.”
        Section 4.2.2, page 10, states that “agriculture occupies less than 0.2% of the total land area of the
        Bishop Creek Watershed.” The only agricultural parcel in this watershed is a tree farm located near the
        bishop and mullet creek divide.

                                                     50
Florida Department of Environmental Protection
  DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),




Response: The statement, “Livestock with direct access to the receiving water could also contribute to the
exceedances during the dry weather condition” describes in general one of the possible explanations for high
fecal coliform counts under low flow conditions. It does not imply that this is the case for Bishop Creek.

     12. Additionally, please explain the exceedances’ “direct correlation with rainfall. “

Response: We will revise the language in the TMDL report to describe the relationship between fecal coliform
concentrations and rainfall more accurately.

Double Branch (WBID 1513) – DO and Nutrients

    1. Please check Table of Contents. Appendices refer to South Florida documents.

Response: The Table of Contents has been corrected.

    2. A Watershed Mgt plan is available with a complete model and recommendations for Double Branch.
       Please refer to :

Response: This tool may prove invaluable during the BMAP process when assigning individual load
allocations.

    3. Table 2.1 – Double Branch is classified as an estuary (3M) not a stream.

Response: This correction has been made to the TMDL document.
Ms. Kelli Hammer Levy
Pinellas County Department of Environmental Management
August 27, 20009
Page Twenty One


    4. Section 3.2.2, page 8, refers to the Tampa Bay Estuary Program chlorophyll-a targets. See previous
       discussion on page 7.

Response: Although the Total Nitrogen associated with Tampa Bay Chla targets was checked, the final target
for Double Branch was mainly a factor of the reference concentrations determined through use of the reference
waterbodies.

    5. Please refer Page 9 – The R2 of 0.149 does not show a valid relationship between TN and Chla. It only
       shows that 15% of the TN values are impacted by Chla. See previous discussion on page 7.

Response: Although Chlorophyll-a is influenced by multiple factors that prevent the observation of a greater
graphical or regression relationship, it was decided to present the relationship and coefficient of determination,
R2. Such is the case with environmental variables. The approach here was to determine the TN target through
this relationship to use as a guide related to whether the load introduced to the bay from these waterbodies
would be consistent with conditions in Tampa Bay. This process showed that the target, which was determined
through the reference method, was below the Chla based TN target. This was true when investigating several
estuaries flowing into the bay (in fact all investigations showed a TN target between 0.9 and 1 mg/L) which is
above the eventual Double Branch target.

    6. Table 3.3, page 10 – Where are the reference WBIDs located? Please provide site location information.

Response: The Department-Assessment based reference sites for Tampa Bay Group 1 include Direct Runoff
to Bay (WBIDs 1603, 1609, and 1676), Big Bayou – Basin W (WBID 1709), Hillsborough Bay-Lower (WBID

                                                      51
Florida Department of Environmental Protection
  DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),



1558D), Hillsborough Bay-Upper (WBID 1558E), Papy’s Bayou (WBID 1661G), Frenchmen’s Creek (WBID
1709), and Bishop’s Harbor (WBID 1797B).

    7. Page 12- Please explain the relationship between 5MGD and 12MADF of reclaimed water.
       This paragraph contains multiple undefined acronyms.


Response: The 12MADF and other acronyms related to the specific plant operation have been removed from
the TMDL document.

    8. Page 17 States that EMCs are used to calculate nutrient contributions. Why are available flow and
       concentration data not being used? See previous comments related to this analysis on page 4.

Response: The loads calculated were used to illustrate the relative contributions from major sources. These
loads were not used in the calculation of the TMDLs. It is quite possible that during the BMAP phase, it may be
useful to apply another method for estimating loads (including the use of more local EMCs collected under an
array of rainfall conditions).

    9. Page 20 – Loads are not being calculated, only concentrations. The reference to EPA 2000 is invalid.
       This document was created for the establishment of nutrient criteria in the xeric west, not to establish
       TMDLs in Florida.

Response: The Department believes that the best way to move forward in restoring water quality in Double
Branch is to establish the concentration-based TMDL and to calculate the source-specific allowable loads to the
waterbody during the BMAP development process. The Tampa Bay Nitrogen Management Consortium is
scheduled to submit to the Department a draft update of the Reasonable Assurance (RA) Plan for Tampa Bay
by September 25, 2009. The RA plan will provide load allocations to individual entities discharging to the bay,
Ms. Kelli Hammer Levy
Pinellas County Department of Environmental Management
August 27, 20009
Page Twenty Two


which have not yet been completed. Up until this time, the total nitrogen loadings to Tampa Bay have been
calculated and evaluated for each of the major bay segments, as these are the assessment units used for
tracking progress in meeting the resource-based water quality targets. Preferably, the calculation of allowable
loads to the smaller impaired water segments for which TMDLs have been developed, like Double Branch,
would also be viewed for consistency at a larger scale, which would be completed after the review and approval
of the updated RA plan, to ensure that consistent flow estimates and other assumptions are used in both
processes.

The reference method, outlined in the EPA document, has been used throughout the United States. The
document itself references sites around the US.

    10. Section 6.3, page 23 – No loading was calculated.

Response: The Department believes that the best way to move forward in restoring water quality in
Double Branch is to establish the concentration-based TMDL and to calculate the source-specific
allowable loads to the waterbody during the BMAP development process. The Tampa Bay Nitrogen
Management Consortium is scheduled to submit to the Department a draft update of the Reasonable
Assurance (RA) Plan for Tampa Bay by September 25, 2009. The RA plan will provide load allocations to
individual entities discharging to the bay, which have not yet been completed. Up until this time, the total
nitrogen loadings to Tampa Bay have been calculated and evaluated for each of the major bay segments,
as these are the assessment units used for tracking progress in meeting the resource-based water quality
targets. Preferably, the calculation of allowable loads to the smaller impaired water segments for which
                                                    52
Florida Department of Environmental Protection
  DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),



TMDLs have been developed, like Double Branch, would also be viewed for consistency at a larger scale,
which would be completed after the review and approval of the updated RA plan, to ensure that
consistent flow estimates and other assumptions are used in both processes.

The Department truly values the participation and time Pinellas County put into the review of the TMDL
documents and their involvement in the TMDL program. The attention and effort to this TMDL review is
evidenced by the quality and volume of comments submitted. The resultant TMDLs, as a result of the
review, will be significantly enhanced. We hope that our responses allay concerns about the TMDLs.
Please continue to feel free to communicate with the Department about the TMDLs. The Department
looks forward to a continued cooperative effort as we move forward in restoring surface water quality
during the BMAP process.

If you have any questions concerning our responses, please do not hesitate to contact me at (850) 245-
8448.

                                           Sincerely,



                                           Jan Mandrup-Poulsen, Environmental Administrator
                                           Watershed Evaluation and TMDL Section

ec: Jeff Greenwell
    Charles Kovach
    Terry Hansen




                                                        53
Florida Department of Environmental Protection
  DRAFT TMDL Report: Moccasin Creek Tidal (WBID 1530,) and Lake Tarpon Canal (WBID1541A, 1541B),




                        Florida Department of Environmental Protection
                            Division of Water Resource Management
                               Bureau of Watershed Management
                            2600 Blair Stone Road, Mail Station 3565
                                Tallahassee, Florida 32399-2400
                                   www2.dep.state.fl.us/water/


                                                 54
Florida Department of Environmental Protection

				
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