List of Wastewater Facilities in the Weeki Wachee Spring Contributing Area ______66 Appendix C: Public Comment ______68
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SOUTHWEST DISTRICT • SPRINGS COAST BASIN FINAL TMDL Report Nutrient TMDLs for Weeki Wachee Spring and Weeki Wachee River (WBIDs 1382B and 1382F) James Dodson and Kristina Bridger Ground Water Management Section Division of Environmental Assessment and Restoration Florida Department of Environmental Protection June 2014 2600 Blair Stone Road Mail Station 3575 Tallahassee, FL 32399-2400 FINAL TMDL Report: Springs Coast Basin, Weeki Wachee Spring and Weeki Wachee River (WBIDs 1382B and 1382F), Nutrients, June 2014 Acknowledgments This analysis could not have been accomplished without significant contributions from Kirstin Eller, Edgar Wade, and Paul Lee in the Florida Department of Environmental Protection’s Water Quality Evaluation and Total Maximum Daily Loads Program, Ground Water Management Section. The authors also appreciate the assistance provided by the Southwest Florida Water Management District in obtaining information on historical studies and in their review of this report. Map production was provided by Ron Hughes in the Department’s Office of Watershed Services. Editorial assistance was provided by Linda Lord in the Department’s Watershed Planning and Coordination Section. For additional information on the watershed management approach and impaired waters in the Springs Coast Basin, contact: Terry Hansen Florida Department of Environmental Protection Watershed Restoration Program Watershed Planning and Coordination Section 2600 Blair Stone Road, Mail Station 3565 Tallahassee, FL 32399-2400 [email protected] Phone: (850) 245–8561 Fax: (850) 245–8434 Access to all data used in the development of this report can be obtained by contacting: Richard Hicks, P.G. Florida Department of Environmental Protection Water Quality Evaluation and TMDL Program Ground Water Management Section 2600 Blair Stone Road, Mail Station 3575 Tallahassee, FL 32399-2400 [email protected] Phone: (850) 245–8229 Fax: (850) 245–8236 Page ii of vii FINAL TMDL Report: Springs Coast Basin, Weeki Wachee Spring and Weeki Wachee River (WBIDs 1382B and 1382F), Nutrients, June 2014 Contents Chapter 1: INTRODUCTION _________________________________________________________1 1.1 Purpose of Report _________________________________________________________1 1.2 Identification of Waterbodies ________________________________________________1 1.3 Background ______________________________________________________________7 Chapter 2: DESCRIPTION OF WATER QUALITY PROBLEM ____________________________10 2.1. Statutory Requirements and Rulemaking History ______________________________10 2.2. Information on Verified Impairment _________________________________________10 2.3 Nutrients ________________________________________________________________11 2.3.1 Nitrate _____________________________________________________________11 2.3.2 Phosphorus _________________________________________________________12 2.4 Ecological Issues Related to Nutrients _______________________________________12 2.4.1 Algal Mats __________________________________________________________12 2.4.2 Other Ecological Issues ________________________________________________13 2.5 Monitoring Sites and Sampling _____________________________________________17 2.6 Rainfall and Temperature Data _____________________________________________19 2.7 Discharge Data ___________________________________________________________19 2.8 Monitoring Results________________________________________________________21 2.8.1 Nitrogen ____________________________________________________________21 2.8.2 Phosphorus _________________________________________________________25 Chapter 3. DESCRIPTION OF APPLICABLE WATER QUALITY STANDARDS AND TARGETS ______________________________________________________________26 3.1 Classification of the Waterbody and Criteria Applicable to the TMDL ____________26 3.2 Applicable Water Quality Standards and Numeric Water Quality Targets _________26 3.2.1 Nutrients ___________________________________________________________26 3.2.2 Outstanding Florida Water Designation ___________________________________27 Chapter 4: ASSESSMENT OF SOURCES ______________________________________________28 4.1 Population and Land Use in the Weeki Wachee Spring Contributing Area _________28 4.1.1 Population __________________________________________________________28 4.1.2 Land Uses __________________________________________________________28 4.2 Types of Sources __________________________________________________________32 4.3 Potential Sources of Nitrate in the Weeki Wachee Spring Contributing Area ____________________________________________________________________33 4.3.1 Wastewater and Stormwater Sources _____________________________________33 Chapter 5: DETERMINATION OF ASSIMILATIVE CAPACITY ___________________________42 5.1 Determination of Loading Capacity __________________________________________42 5.2 TMDL Development Process _______________________________________________43 5.2.1 Use of Site-Specific Information _________________________________________43 Page iii of vii FINAL TMDL Report: Springs Coast Basin, Weeki Wachee Spring and Weeki Wachee River (WBIDs 1382B and 1382F), Nutrients, June 2014 5.3 Setting the Annual Average Concentration for Nitrate __________________________48 5.4 Critical Conditions/Seasonality _____________________________________________49 5.5 Calculation of TMDL Percent Reduction _____________________________________50 Chapter 6: DETERMINATION OF THE TMDL _________________________________________52 6.1 Expression and Allocation of the TMDL ______________________________________52 6.1.1 Calculation of MDC for Nitrate for Weeki Wachee Spring and River ____________52 6.2 Wasteload Allocation ______________________________________________________55 6.2.1 NPDES Wastewater Discharges _________________________________________55 6.2.2 NPDES Stormwater Discharges _________________________________________55 6.3 Margin of Safety __________________________________________________________55 Chapter 7: NEXT STEPS: IMPLEMENTATION PLAN DEVELOPMENT AND BEYOND _____56 7.1 Basin Management Action Plan _____________________________________________56 References ______________________________________________________________________58 Appendix A: Background Information on Federal and State Stormwater Programs _____________64 Appendix B: List of Wastewater Facilities in the Weeki Wachee Spring Contributing Area _______66 Appendix C: Public Comment ________________________________________________________68 Page iv of vii FINAL TMDL Report: Springs Coast Basin, Weeki Wachee Spring and Weeki Wachee River (WBIDs 1382B and 1382F), Nutrients, June 2014 List of Tables Table 2.1. Verified Impaired Spring-Related Segments in the Weeki Wachee Spring Basin _________11 Table 2.2. Temperature and Precipitation at NOAA Station (Weeki Wachee - 089430), 1982– 2012 ___________________________________________________________________19 Table 2.3. Adjusted Annual Mean Discharge for Weeki Wachee River, 1917–2012 _______________21 Table 2.4. Nitrate and TN Concentrations for Weeki Wachee Spring, WBID 1382B, 2004–2012 _____23 Table 2.5. Nitrate and TN Concentrations for Weeki Wachee River, WBID 1382F, 2000–12 ________24 Table 2.6. TP Concentrations for Weeki Wachee Spring, 2004–2012 __________________________25 Table 2.7. TP Concentrations for Weeki Wachee River, 2004–2012 ___________________________25 Table 4.1. Percentages of Major Land Uses in the Weeki Wachee Spring Contributing Area in 2009 ___________________________________________________________________32 Table 4.2. Domestic Wastewater Facilities with Permitted Capacity over 0.1 MGD and RMFs in the Vicinity of Weeki Wachee Spring and River _________________________________35 Table 4.3. Potential Fertilizer Application Ranges for Selected Land Uses in the Weeki Wachee Spring Contributing Area __________________________________________________41 Table 5.1. SAV Occurrence during 1991 (adapted from SWFWMD 1994) _______________________47 Table 5.2. Yearly Average Nitrate Concentrations for Weeki Wachee Spring and River (2004– 12) ____________________________________________________________________50 Table 6.1. Daily Maximums for Target Nitrate Concentrations (mg/L) _________________________53 Table 6.2. TMDL Components for Weeki Wachee Spring and River ___________________________54 Page v of vii FINAL TMDL Report: Springs Coast Basin, Weeki Wachee Spring and Weeki Wachee River (WBIDs 1382B and 1382F), Nutrients, June 2014 List of Figures Figure 1.1. Major Geopolitical and Hydrologic Features in the Estimated Contributing Area of the Two Impaired WBIDs in Hernando and Pasco Counties ________________________2 Figure 1.2. Aerial Photograph of Weeki Wachee Spring and the Headwaters of the Weeki Wachee River (Department photo) ____________________________________________3 Figure 1.3. Named Springs and Impaired WBIDs in the Weeki Wachee Spring Area (Cave Conduit image courtesy of Karst Underwater Research) ___________________________4 Figure 1.4. FAVA Map in the Contributing Area for Weeki Wachee Spring and Weeki Wachee River (Arthur 2007) ________________________________________________________8 Figure 2.1. Archives Underwater Photo of Weeki Wachee Spring Shows Native Vegetation (Florida Archives photo) ___________________________________________________14 Figure 2.2. Archives Underwater Photo of Weeki Wachee Spring Shows Native Vegetation and Water Clarity (Florida Archives photo) _______________________________________14 Figure 2.3. Algae on Tape Grass