FLORIDA DEPARTMENT OF ENVIRONMENTAL PROTECTION Division of Environmental Assessment and Restoration, Bureau of Watershed Restoration NORTHWEST DISTRICT • PENSACOLA BASIN Final REPORT Nutrient TMDLs North Escambia Bay (WBID 548AA) Judges Bayou (WBID 493B) Bayou Chico (WBIDs 846C and 846) Dissolved Oxygen TMDL Judges Bayou (WBID 493A) Douglas Gilbert June 7, 2013 FINAL TMDL Report: Pensacola Bay Basin; North Escambia Bay (WBID 548AA), Judges Bayou (WBID 493B), Bayou Chico (WBIDs 846C and 846) (Nutrients); Judges Bayou (WBID 493A) (DO); June 7, 2013 Acknowledgments This analysis could not have been accomplished without significant contributions from staff in the Florida Department of Environmental Protection’s Bureau of Watershed Restoration and Northwest District Office. Light detection and ranging (LiDar) data provided by the Northwest Florida Water Management District allowed for the refinement of basin delineations in the Judges Bayou watershed. Modeling support was provided by Tim Wool with the U.S. Environmental Protection Agency (EPA) Region 4 and Tetra Tech under contract with the EPA. Editorial assistance was provided by Jan Mandrup-Poulsen and Linda Lord. Map production assistance was provided by Ronald Hughes. For additional information on the watershed management approach and impaired waters in the Pensacola Bay Basin, contact: Stephen Cioccia, Environmental Consultant Florida Department of Environmental Protection Bureau of Watershed Restoration Watershed Planning and Coordination Section 2600 Blair Stone Road, Mail Station 3565 Tallahassee, FL 32399-2400 [email protected] Phone: (850) 245–8618 Fax: (850) 245–8434 Access to all data used in the development of this report can be obtained by contacting: Douglas Gilbert, Environmental Manager 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 protected] Phone: (850) 245–8450; Fax: (850) 245–8536 ii Florida Department of Environmental Protection FINAL TMDL Report: Pensacola Bay Basin; North Escambia Bay (WBID 548AA), Judges Bayou (WBID 493B), Bayou Chico (WBIDs 846C and 846) (Nutrients); Judges Bayou (WBID 493A) (DO); June 7, 2013 Contents Chapter 1: INTRODUCTION ____________________________________________ 1 1.1 Purpose of Report _______________________________________________ 1 1.2 Identification of Waterbody ________________________________________ 1 1.2.1 Bayou Chico _______________________________________________ 1 1.2.2 Judges Bayou ______________________________________________ 1 1.2.3 North Escambia Bay _________________________________________ 1 1.3 Background ____________________________________________________ 4 Chapter 2: DESCRIPTION OF WATER QUALITY PROBLEM __________________ 5 2.1 Legislative and Rulemaking History _________________________________ 5 2.2 Information on Verified Impairment _________________________________ 5 2.3 Summary of Verified Impairments __________________________________ 6 2.3.1 Bayou Chico (WBIDs 846 and 846C) Impairments __________________ 6 2.3.2 Judges Bayou (WBIDs 493A and 493B) Impairments ________________ 7 2.3.3 Escambia Bay (WBID 548AA) Impairments ________________________ 8 2.4 Summary of Verified Period Data ___________________________________ 9 2.4.1 Bayou Chico Watershed (WBIDs 846A, 846B, 846, and 846C) Data ____ 9 2.4.2 Middle Pensacola Bay Watershed (WBID 548D) Data ______________ 19 2.4.3 Judges Bayou Watershed (WBIDs 493A and 493B) Data ____________ 20 2.4.4 North Escambia Bay (WBID 548AA) Data ________________________ 29 Chapter 3. DESCRIPTION OF APPLICABLE WATER QUALITY STANDARDS AND TARGETS ____________________________________________ 45 3.1 Classification of the Waterbody and Criteria Applicable to the TMDL ____ 45 3.2 Applicable Water Quality Standards and Numeric Water Quality Target ____________________________________________________ 45 3.2.1 Nutrients _________________________________________________ 45 3.2.2 Chlorophyll ________________________________________________ 46 3.2.3 Nitrogen Total as N (TN) _____________________________________ 46 3.2.4 Phosphorus Total as P (TP) __________________________________ 46 3.2.5 DO Freshwater ____________________________________________ 47 Chapter 4: ASSESSMENT OF SOURCES ________________________________ 48 4.1 Types of Sources _______________________________________________ 48 4.2 Potential Sources of Nutrients in the Impaired Watersheds ____________ 48 4.2.1 Point Sources _____________________________________________ 48 iii Florida Department of Environmental Protection FINAL TMDL Report: Pensacola Bay Basin; North Escambia Bay (WBID 548AA), Judges Bayou (WBID 493B), Bayou Chico (WBIDs 846C and 846) (Nutrients); Judges Bayou (WBID 493A) (DO); June 7, 2013 4.2.2 Municipal Separate Storm Sewer System Permittees _______________ 52 4.2.3 Land Uses and Nonpoint Sources ______________________________ 52 4.2.4 Population ________________________________________________ 64 4.2.5 Septic Tanks ______________________________________________ 64 4.2.6 Sediment Nutrient Release ___________________________________ 71 Chapter 5: DETERMINATION OF ASSIMILATIVE CAPACITY_________________ 72 5.1 Determination of Loading Capacity _________________________________ 72 5.2 Overview of Modeling Process ____________________________________ 74 5.2.1 Mechanistic Models _________________________________________ 74 5.2.2 Model Development _________________________________________ 75 5.3 TMDL Development Process ______________________________________ 78 5.3.1 Bayou Chico (WBIDs 846 and 846C) ___________________________ 78 5.3.2 Judges Bayou (WBIDs 493A and 493B) _________________________ 86 5.3.3 North Escambia Bay (WBID 548AA) ____________________________ 87 5.4 Critical Conditions/Seasonality ___________________________________ 105 Chapter 6: DETERMINATION OF THE TMDL _____________________________ 106 6.1 Expression and Allocation of the TMDL ___________________________ 106 6.2 Load Allocation (LA) ___________________________________________ 108 6.2.1 Bayou Chico (WBIDs 846 and 846C) __________________________ 108 6.2.2 Judges Bayou (freshwater) (WBID 493A) _______________________ 108 6.2.3 North Escambia Bay (WBID 548AA) and Judges Bayou (marine) (WBID 493B) _____________________________________________ 109 6.2.4 Alabama ________________________________________________ 109 6.3 Wasteload Allocation (WLA) _____________________________________ 109 6.3.1 NPDES Wastewater Discharges ______________________________ 109 6.3.2 NPDES Stormwater Discharges ______________________________ 110 6.4 Margin of Safety (MOS) _________________________________________ 111 Chapter 7: NEXT STEPS: IMPLEMENTATION PLAN DEVELOPMENT AND BEYOND ________________________________________________ 112 7.1 Basin Management Action Plan __________________________________ 112 7.2 Next Steps for TMDL Implementation _____________________________ 113 References 116 Appendices ________________________________________________________ 121 Appendix A: Background Information on Federal and State Stormwater Programs ________________________________________________ 121 iv Florida Department of Environmental Protection FINAL TMDL Report: Pensacola Bay Basin; North Escambia Bay (WBID 548AA), Judges Bayou (WBID 493B), Bayou Chico (WBIDs 846C and 846) (Nutrients); Judges Bayou (WBID 493A) (DO); June 7, 2013 Appendix B: Bayou Chico (WBIDs 846 and 846C) and Middle Pensacola Bay (WBID 548D) Data Tables/Figures (Separate Document) ______ 122 Appendix C: Judges Bayou (WBIDs 493A and 493B) Data Tables/Figures (Separate Document) _______________________________________ 122 Appendix D: Pensacola Bay (WBIDs 548AA, 548AC, 548B, 548GA, 548GB, 548H, 548C, 548D, 548E, and 915) Data Tables/Figures (Separate Document) _______________________________________________ 122 Appendix E: Pensacola Basin TMDL Model Results: Bayou Chico (WBIDs 846 and 846C) and North Escambia Bay (WBID 548AA) Figures/Tables (Separate Document) __________________________ 122 Appendix F: Pensacola Basin TMDL Public Comments and Department Reponses: Bayou Chico (WBIDs 846 and 846C), Judges Bayou (WBIDs 493A and 493B), and North Escambia Bay (WBID 548AA) (Separate Document) _______________________________________ 122 v Florida Department of Environmental Protection FINAL TMDL Report: Pensacola Bay Basin; North Escambia Bay (WBID 548AA), Judges Bayou (WBID 493B), Bayou Chico (WBIDs 846C and 846) (Nutrients); Judges Bayou (WBID 493A) (DO); June 7, 2013 List of Tables Table 2.1. Verified Impaired Segments (Nutrients and DO) in the Pensacola Bay Basin _______________________________________ 6 Table 2.2. Assessment Results for Bayou Chico (WBIDs 846 and 846C) ________ 6 Table 2.3. DO Assessment Results for Judges Bayou (Freshwater) (WBID 493A) ___________________________________________________ 7 Table 2.4. DO Impairment in Judges Bayou (Freshwater) (WBID 493A) _________ 8 Table 2.5. Nutrient Impairment in Judges Bayou (marine) (WBID 493B) ________ 8 Table 2.6. Nutrient Assessment Results for North Escambia Bay (Marine) (WBID 548AA) ____________________________________________ 9 Table 2.7. Summary of Annual Average Data for Middle Pensacola Bay (WBID 548D) ____________________________________________ 20 Table 4.1. Point Sources in the Escambia Bay Basin (Florida) _______________ 50 Table 4.2. Classification of Level 1 Land Use Categories in the Bayou Chico Watershed, 2009–10 _________________________________ 54 Table 4.3.