Proposed total maximum daily load (tmdl) For Biochemical Oxygen Demand, Dissolved Oxygen, Nutrients and Unionized Ammonia In the Lake Okeechobee Tributaries Osceola, Polk, Okeechobee, Highlands, Glade, Hendry, Palm Beach, Martin, and St
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PROPOSED TOTAL MAXIMUM DAILY LOAD (TMDL) For Biochemical Oxygen Demand, Dissolved Oxygen, Nutrients and Unionized Ammonia In the Lake Okeechobee Tributaries Osceola, Polk, Okeechobee, Highlands, Glade, Hendry, Palm Beach, Martin, and St. Lucie Counties, Florida Prepared by: US EPA Region 4 61 Forsyth Street SW Atlanta, Georgia 30303 September 2006  
TABLE OF CONTENTS i 1 INTRODUCTION 1 1.1 Purpose of Report 6 1.2 Previous Studies in the Lake Okeechobee Watershed 6 1.3 Identification of Impaired Waterbodies 9 1.3.1 Lake Okeechobee Basin 9 1.3.2 Kissimmee River Basin 15 1.3.3 Fisheating Creek Basin 17 1.3.4 Caloosahatchee River Basin 22 1.3.5 L-8 Basin 22 1.3.6 Everglades Agricultural Area 23 2 STATEMENT OF WATER QUALITY PROBLEM 25 3 WATER QUALITY STANDARDS 26 3.1 Nutrient Criterion 26 3.2 Dissolved Oxygen Criterion 26 3.3 Biochemical Oxygen Demand Criterion 27 3.4 Unionized Ammonia Criterion 27
4.1 Basis and Rationale For Nutrient Targets 28 4.2 Nutrient Target Development 32
4.3 Nutrient Target Application 35 4.4 DO and BOD Target 36 4.5 Unionized Ammonia Target 37 5 WATER QUALITY RESULTS 39 6 SOURCE ASSESSMENT 48 6.1 Background Loads 48 6.2 Permitted Point Sources 48
6.3 Nonpoint Sources 52 6.3.1 Agriculture 52 6.3.2 Sediment 53 6.3.3 Septic Systems 54 6.3.4 Stormwater Runoff 54 7 DEVELOPMENT OF THE TMDL 54 7.1 Nutrient TMDL 55 7.2 Unionized Ammonia TMDL 61 7.3 BOD TMDL 61 8 TMDL ALLOCATION 61 8.1 Allocation 61 8.2 Load Allocation 68 8.3 Wasteload Allocations 68 8.4 Margin of Safety 69 8.5 Seasonal Variability 69 9 TMDL IMPLEMENTATION 69 REFERENCES 71 APPENDIX A: Water Quality Plots 74 Appendix B: Flow Records from DBHYDRO for WBIDs 3238 and 3238E 78 Appendix C: Derivation of WLA for Clewiston STP (FL0040665) 79 Appendix D: Calculation of Limiting Nutrient 83 Appendix F: Modeling Results of Natural Landuse Conditions 93 Appendix G. Rationale for Controlling Nitrogen in Impaired WBIDs 95 LIST OF TABLES Table 1. Planning Unit and Basin Group of Impaired WBIDs 2 Table 2. Comparison of SWIM Basins and Impaired WBIDs 7 Table 3. Summary of Total Phosphorus Loads Discharging into Lake Okeechobee 10 Table 4. Summary of Land Cover in Impaired WBIDs 18 Table 5. Existing Limiting Condition in Impaired WBIDs (based on TP and TN data) 31 Table 6. Summary of Nutrient and Unionized Ammonia Data for Impaired WBIDs 40 Table 7. Summary of DO and BOD Data in WBIDs Impaired For DO 43 Table 8. Permitted Wastewater Facilities Discharging in Impaired WBIDs 49 Table 9. Proposed Permit Limits for Clewiston WWTP (FL0040665) 50 Table 10. MS4 Permittees in the Drainage Basins of Impaired WBIDs 51 Table 11. Area and Inflows for Impaired WBIDs and LOPP Basins (Baseline Conditions) 56 Table 12. Summary of Existing Conditions for Total Nitrogen 59 Table 13. TMDL Components for Total Phosphorus 62 Table 14. TMDL Components for Total Nitrogen 65 Table 15. TMDL Components for Unionized Ammonia 67 Table 16. TMDL Components for BOD 67 Table 17. TP Allocations for LOPP Basins Expressed as Daily Loads 67 LIST OF FIGURES Figure 1. Location of Horseshoe Creek (WBID 1436) in the Upper Kissimmee River Basin 4 Figure 2. Location of Impaired WBIDs Below Lake Kissimmee 5 Figure 3. Control Structures and Sampling Stations in Lake Okeechobee 13 Figure 4. Taylor Creek and Nubbin Slough Basins 15 Figure 5. Location of WBIDs and Monitoring Stations Used to Calculate a Nutrient Target per Section 4.2.2 38 Figure 6. Distribution of Average TP Concentrations 45 Figure 7. Distribution of Average TN Concentrations 46 Figure 8. DO Distribution in the Area Surrounding Lake Okeechobee 47 LIST OF ABBREVIATIONS
SUMMARY SHEET
BOD (62-302.530(12)): Levels shall not be increased to exceed values which would cause dissolved oxygen to be depressed below the limit established for each class and, in no case shall it be great enough to produce nuisance conditions. DO (62-302.530(31)): Dissolved oxygen shall not be less than 5.0 mg/l. Normal daily and seasonal fluctuations above these levels shall be maintained. The water quality standard for DO also considers the definition of natural background and the directive not to abate natural conditions (62-302.200(15) FAC and 62-302.300(15) FAC). Nutrients (62-302.530(48)(a)): The discharge of nutrients shall continue to be limited as needed to prevent violations of other standards contained in this chapter. Man induced nutrient enrichment (total nitrogen and total phosphorus) shall be considered degradation in relation to the provisions of Section 62-302.300, 62-302.700, and 62-4.242, FAC. 62-302.530(48)(b) In no case shall nutrient concentrations of a body of water be altered so as to cause an imbalance in natural populations of aquatic flora or fauna. Unionized Ammonia (62-302.530(3)): Ammonia (unionized) levels shall be less than or equal to 0.02mg/l.
Nutrients: The TMDLs target both Total Phosphorus (TP) and Total Nitrogen (TN) based on three approaches as described in Section 4 of this report. Results of the three approaches indicate an appropriate TP target range between 70 and 90 ppb and a TN target between 1.04 and 1.3 mg/l. The averages of these values were selected as the target TP and TN concentrations and are equal to 77 ppb and 1.2 mg/l, respectively. The TMDL targets were developed to support the State of Florida’s narrative water quality standard for nutrients by not causing an imbalance in natural populations of aquatic flora and fauna and also to not produce or contribute to conditions that violate the State’s standard for dissolved oxygen. Control of both nutrients, N and P, in upstream waters provides additional assurance that excess productivity will remain in control, and avoids pollutant caused depressions of dissolved oxygen. The TMDL will ensure protection for aquatic life both in the tributary WBIDs, as well as not contribute to water quality impairments in the downstream waters of Lake Okeechobee and its subsequent drainage to the coastal estuaries of the St. Lucie and the Caloosahatchee. Dissolved Oxygen: TMDLs for dissolved oxygen are addressed through controlling nutrients. When BOD data are available and a correlation can be determined between DO and BOD, the TMDL targets BOD. Many of the impaired waterbodies have been channelized or are canals and it may be difficult to consistently meet the statewide DO standards even after controlling pollutant concentrations. In such circumstances calculating allocations would be targeted to achieve the natural background loading and natural instream pollutant concentrations in the waterbody. Any allowance of increased loadings beyond natural background would likely cause other than natural dissolved oxygen levels, which would not be a proper application of the Florida definition. Because the standard prevents abatement of natural conditions, the TMDL can provide an allocation, where necessary, that results in natural conditions. A site specific criterion needs to be established to target a condition other than natural concentrations of pollutants. BOD: A regression analysis correlating BOD to DO was developed to determine the BOD concentration necessary to maintain DO levels above the water quality standard (see the DO discussion above). Unionized Ammonia: The TMDL for unionized ammonia is based on the numerical criteria (0.02 mg/l) and an estimate of flow. Existing conditions are based on the 95th percentile concentration measured in the WBID.
Note: A daily TP concentration of 77 ppb should be achieved based on an annual average of the measured days recognizing natural variability; the WLA for WBID 3246 is equivalent to 0.96 lb/day.
lb/day = Mton/yr * yr/365.25 day * 2204.623 lb/Mton. Note: Achievement of the annual load would imply achievement of the daily load averaged through the year; therefore, implementation should target the annual load.
Note: The expressed daily TN load should be achieved based on an annual average of the measured days recognizing natural variability.
MS4 Allocations:
Note: When an MS4 covers more than one WBID, the largest percent reduction calculated for an impaired WBID is assigned to the MS4. The MS4 is responsible for controlling pollutant loads from the urban areas within its jurisdiction.
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lorida 1998 303(d) Listed Waterbody Information