Lake Mary Regional TMDL For Mercury in Fish Tissue Upper Lake Mary, Lower Lake Mary, Soldiers Lake, Soldiers Annex Lake, and Lower Long Lake Little Colorado River Watershed Coconino County Arizona Department of Environmental Quality June 16, 2010 Open File Report #OFR 10-02 Lake Mary Regional TMDL Page Intentionally Left Blank Page i Lake Mary Regional TMDL Acknowledgements: EPA Region 9 for funding support via Clean Water Act Section 104(b)(3) grant monies. Malcolm Pirnie for data analysis and modeling support. Paul Gremillion and his students for sediment core collection and analysis and lake bathymetry development. Amanda Fawley and Jennifer Hummer for project design and sampling in all weather. Jason Sutter, Debra Daniel, and Linda Taunt for review, edits and insight. Page ii Lake Mary Regional TMDL Table of Contents List of Tables................................................................................................................... v List of Figures.................................................................................................................. v List of Acronyms..............................................................................................................vi I. EXECUTIVE SUMMARY.............................................................................................. 1 II. INTRODUCTION AND PROBLEM STATEMENT ....................................................... 3 A. Description of TMDL Process.................................................................................. 3 B. Clean Water Act Section 305 (b), 303 (d) and significance ..................................... 3 III. WATERSHED CHARACTERIZATION ....................................................................... 4 A. Description of Study Area........................................................................................ 4 Figure 1. Vicinity Map (adapted from Malcolm Pirnie, 2006)1. Upper and Lower Lake Mary ................................................................................................................ 5 1. Upper and Lower Lake Mary................................................................................ 6 2. Soldiers and Lower Long Lake Complex.............................................................. 6 3. Background Lakes ............................................................................................... 7 B. Climate .................................................................................................................... 7 1. Upper and Lower Lake Mary................................................................................ 7 2. Soldiers and Lower Long Lake Complex.............................................................. 8 C. Hydrology................................................................................................................ 8 D. Geology................................................................................................................. 12 E. Land Cover/Vegetation.......................................................................................... 12 IV. DATA COLLECTION & DATA SUMMARY .............................................................. 12 A. Fish Tissue Sampling ............................................................................................ 13 B. Lake and Tributary Sampling ................................................................................ 14 1. Thermal Stratification ......................................................................................... 15 2. Dissolved Oxygen .............................................................................................. 15 3. Mercury .............................................................................................................. 15 4. Other Water Quality Constituents....................................................................... 15 5. Correlations Between Constituents.................................................................... 16 C. Lake Sediment Results ......................................................................................... 16 1. Mercury .............................................................................................................. 17 2. Other Sediment Constituents ............................................................................. 17 3. Correlations Between Constituents.................................................................... 17 D. Watershed Sub-surface and Surficial Soil Results................................................ 18 E. Runoff and Stream Flow Results........................................................................... 20 V. SOURCE ASSESSMENT ......................................................................................... 23 A. Atmospheric Deposition ........................................................................................ 23 B. Summary of Lake Coring Study............................................................................. 25 Page iii Lake Mary Regional TMDL C. Watershed Source ................................................................................................ 27 VI. MERCURY CYCLING AND SITE CONCEPTUAL MODEL ..................................... 28 VII. MODEL DEVELOPMENT ....................................................................................... 31 A. Watershed Hydrologic and Sediment Loading Model............................................ 31 B. Runoff and Groundwater Inputs ............................................................................ 32 C. Solids in Runoff..................................................................................................... 33 D. Lake Hydrologic Model.......................................................................................... 34 E. Mercury Cycling Model.......................................................................................... 35 F. Mercury Bioaccumulation Estimation..................................................................... 36 VIII. TMDL CONSIDERATIONS.................................................................................... 37 A. Numeric Targets.................................................................................................... 37 B. Narrative Targets................................................................................................... 37 C. Critical Conditions ................................................................................................. 37 D. TMDL Targets ....................................................................................................... 38 IX. LINKAGE ANALYSIS............................................................................................... 38 X. INITIAL MODELING RESULTS ................................................................................ 40 A. Watershed Runoff and Sediment Yield ................................................................. 40 B. Lake Hydrology ..................................................................................................... 41 XI. MODEL REFINEMENTS ......................................................................................... 43 A. Mercury Loads....................................................................................................... 43 B. Model Simulated Lake Water Column Total and Methyl-mercury.......................... 46 C. Model Forecasts of Fish Tissue Concentrations in Response to Decreases in Anthropogenic Mercury Loads.............................................................................. 47 D. Modeling Summary ............................................................................................... 48 XII. TMDL CALCULATIONS.......................................................................................... 51 A. Fish Tissue Criterion and Trophic Considerations................................................. 51 B. Load Reductions ................................................................................................... 52 XIII. CONCLUSION....................................................................................................... 53 XIV. IMPLEMENTATION PLAN .................................................................................... 54 XV. PUBLIC PARTICIPATION ...................................................................................... 55 REFERENCES.............................................................................................................. 57 Page iv Lake Mary Regional TMDL List of Tables Table 1. LMR Lakes ....................................................................................................... 4 Table 2. Summary of Fish Tissue Data ........................................................................ 13 Table 3. Comparison of Water Quality Between Lakes................................................ 16 Table 4. Average Lake Sediment Mercury Concentrations .......................................... 17 Table 5. Surface Soil/Sediment Collected During Runoff............................................. 18 Table 6. Sub-surface Background Soil Data ................................................................ 19 Table 7. Total Mercury in Runoff as Suspended Solids................................................ 22 Table 8. Average Tissue Concentrations, Water Column and Sediment Methyl-mercury, and BAFs ..............................................................................................................