Total Maximum Daily Loading
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FINAL 7/8/08 FLORIDA DEPARTMENT OF ENVIRONMENTAL PROTECTION Division of Water Resource Management, Bureau of Watershed Management NORTHEAST DISTRICT • LOWER ST. JOHNS BASIN TMDL Report Total Maximum Daily Load for Nutrients for the Lower St. Johns River Dr. Wayne Magley and Daryll Joyner Watershed Assessment Section Bureau of Watershed Management Florida Department of Environmental Protection 2600 Blair Stone Road, MS 3555 Tallahassee, FL 32399-2400 June 2008 FINAL TMDL Report: Lower St. Johns Basin, Lower St. Johns River, Nutrients Table of Contents ACKNOWLEDGMENTS ................................................................................................ IV 1. INTRODUCTION ........................................................................................................ 1 1.1 Purpose of Report ............................................................................................ 1 1.2 Development of the TMDL ............................................................................... 1 1.3 Revision of the TMDL ....................................................................................... 1 1.4 Identification of Waterbody ............................................................................. 2 2. STATEMENT OF WATER QUALITY PROBLEM ...................................................... 6 2.1 Verified Nutrient Impairment of the LSJR ...................................................... 6 2.2 Other Indications of Nutrient Impairment ....................................................... 7 3. DESCRIPTION OF APPLICABLE WATER QUALITY STANDARDS AND WATER QUALITY TARGETS ................................................................................. 9 3.1 Classification of the LSJR and Criteria Applicable to the TMDL .................. 9 3.2 DO Criterion ...................................................................................................... 9 3.3 Nutrient Criterion ............................................................................................ 10 4. DETERMINATION OF CURRENT LOADING ......................................................... 12 4.1 Types of Sources ........................................................................................... 12 4.2 Background .................................................................................................... 12 4.3 Permitted Point Sources ................................................................................ 14 4.3.1 Inventory of Point Sources ................................................................. 14 4.3.2 Estimating Point Source Loads .......................................................... 16 4.3.3 Municipal Separate Storm Sewer System Permittees ...................... 16 4.4 Nonpoint Sources .......................................................................................... 17 4.4.1 Pollution Load Screening Model ........................................................ 17 4.4.2 Atmospheric Deposition ..................................................................... 18 4.4.3 Sediment Flux ...................................................................................... 19 4.5 Loading Inventory .......................................................................................... 19 5. DETERMINATION OF ASSIMILATIVE CAPACITY ................................................ 21 5.1 Use of Modeling .............................................................................................. 21 5.2 Models Used ................................................................................................... 21 5.3 Model Setup .................................................................................................... 24 5.4 Model Calibration ........................................................................................... 24 5.5 Model Results Used To Determine Assimilative Capacity .......................... 25 i Florida Department of Environmental Protection FINAL TMDL Report: Lower St. Johns Basin, Lower St. Johns River, Nutrients 6. DETERMINATION OF THE TMDL .......................................................................... 29 6.1 Expression and Allocation of the TMDL ....................................................... 29 6.2 Load Allocations ............................................................................................ 31 6.3 Wasteload Allocations ................................................................................... 31 6.4 Aggregate Loads and Pollutant Trading ...................................................... 31 6.5 Margin of Safety ............................................................................................. 32 6.6 Seasonal Variability ....................................................................................... 33 7. NEXT STEPS: IMPLEMENTATION PLAN DEVELOPMENT AND BEYOND ........ 34 7.1 Basin Management Action Plan .................................................................... 34 REFERENCES .............................................................................................................. 36 List of Figures Figure 1. The Lower St. Johns River .................................................................... 3 Figure 2. Ecological Zones of the Lower St. Johns River Basin ....................... 4 Figure 3. Waterbody Identification Numbers for the Main Stem of the LSJR ....................................................................................................... 5 Figure 4. Data Collection and Monitoring Stations of the External Load Assessment.......................................................................................... 13 Figure 5. TN Loading to the LSJR by Source Category ................................... 20 Figure 6. TP Loading to the LSJR by Source Category .................................... 20 Figure 7. Model Cells for the LSJR Modeling .................................................... 22 Figure F1. Accuracy of Model DO Predictions for Acosta Bridge ..................... 56 Figure F2. Accuracy of Model DO Predictions for Dames Point ........................ 57 Figure G1. Comparisons of Model Predictions Versus Measured Values for Chlorophyll a at Racy Point ................................................................ 59 Figure G2. Comparisons of Model Predictions Versus Measured Values for Chlorophyll a at Watson Island .......................................................... 59 Figure G3. Accuracy of Model Predictions of Average Annual Chlorophyll a for the Freshwater Section.................................................................. 60 Figure G4. Accuracy of Model Predictions for Chlorophyll a Percent Exceedances for the Freshwater Section .......................................... 60 List of Tables Table 1. Verified Impaired Segments of the Main Stem of the LSJR ............... 7 Table 2. Permitted Wastewater Facilities Discharging to the LSJR ............... 15 Table 3. Modeled Variables Included in the CE-QUAL-ICM Model ................. 23 Table 4. Starting Point TN and TP Loads for Point Sources .......................... 27 ii Florida Department of Environmental Protection FINAL TMDL Report: Lower St. Johns Basin, Lower St. Johns River, Nutrients Table 5. TMDL Components for the Freshwater Portion of the LSJR ........... 30 Table 6. TMDL Components for the Estuarine Portion of the LSJR .............. 30 Table D1. Summary of Loads to the Lower St. Johns River, 1995. All values in metric tons per year. ........................................................................... 49 Table D2. Summary of Loads to the Lower St. Johns River, 1996. All values in metric tons per year. ........................................................................... 50 Table D3. Summary of Loads to the Lower St. Johns River, 1997. All values in metric tons per year. ........................................................................... 51 Table D4. Summary of Loads to the Lower St. Johns River, 1998. All values in metric tons per year. ........................................................................... 52 Table D5. Summary of Loads to the Lower St. Johns River, 1999. All values in metric tons per year. ........................................................................... 53 List of Appendices Appendix A: The LSJR TMDL Executive Committee ............................................... 38 Appendix B: Eutrophication Defined ........................................................................ 39 Appendix C: Basis for LSJR Water Quality Targets ................................................ 40 Appendix D: Estimated Loads to the LSJR, 1995–99 .............................................. 48 Appendix E: Description of State and Federal Stormwater Programs .................. 54 Appendix F: Examples of DO Calibration Figures for the Water Quality Model ... 55 Appendix G: Examples of Chlorophyll a Calibration Figures for the Water Quality Model ....................................................................................... 58 Appendix H: Responsiveness Summary to Public Comments on Draft TMDL of 2003 .................................................................................................. 61 Appendix I: Annual Average Chlorophyll a Values and TSIs for the LSJR Main Stem ...................................................................................................... 75 Appendix J: Allocation Spreadsheets for the Freshwater and Estuarine Portions of the LSJR ..........................................................................