Benthic TMDL for Stroubles Creek in Montgomery County, Virginia
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Benthic TMDL for Stroubles Creek in Montgomery County, Virginia Submitted by: Virginia Department of Environmental Quality Virginia Department of Conservation and Recreation Prepared by: Department of Biological Systems Engineering, Virginia Tech October 9, 2003 Revised October 16, 2003 Project Personnel Virginia Tech, Department of Biological Systems Engineering Brian Benham, Assistant Professor and Extension Specialist Kevin Brannan, Research Associate Theo A. Dillaha, III, Professor Saied Mostaghimi, Professor Rachel Wagner, Graduate Research Assistant Jeff Wynn, Research Associate Gene Yagow, Research Scientist Rebecca Zeckoski, Research Associate Virginia Department of Environmental Quality Jason Hill, West Central Regional Office, Roanoke George Devlin, West Central Regional Office, Roanoke David Lazarus, State Office, Richmond Virginia Department of Conservation and Recreation (VADCR) Mike Shelor, TMDL Project Coordinator, Richmond Dean Gall, Nutrient Management, Dublin Tom Roberts, Stormwater Management, Dublin For additional information, please contact: Virginia Department of Environmental Quality (VADEQ) Water Quality Assessment Office, Richmond: David Lazarus, (804) 698-4299 West Central Regional Office, Roanoke: Jason Hill (540) 562-6724 Saied Mostaghimi, BSE Project Director, (540) 231-7605 Email: [email protected] Table of Contents CHAPTER 1: EXECUTIVE SUMMARY.........................................................................................................1 1.1. BACKGROUND........................................................................................................... 1 1.2. SOURCES OF SEDIMENT............................................................................................. 2 1.3. MODELING ................................................................................................................ 3 1.4. BENTHIC TMDL FOR SEDIMENT ............................................................................... 3 1.5. PROJECTED FUTURE CONDITIONS ............................................................................. 5 1.6. TMDL REDUCTIONS AND ALLOCATIONS.................................................................. 5 1.7. REASONABLE ASSURANCE ........................................................................................ 7 1.8. PUBLIC PARTICIPATION............................................................................................. 7 CHAPTER 2: INTRODUCTION ....................................................................................................................8 2.1. BACKGROUND........................................................................................................... 8 2.1.1. TMDL Definition and Regulatory Information................................................. 8 2.1.2. Impairment Listing............................................................................................ 8 2.1.3. Watershed Location and Description ............................................................... 8 2.1.4. Pollutants of Concern ....................................................................................... 9 2.2. DESIGNATED USES AND APPLICABLE WATER QUALITY STANDARDS ..................... 10 2.2.1. Designation of Uses (9 VAC 25-260-10) ........................................................ 10 2.2.2. General Standard (9 VAC 25-260-20)............................................................ 11 CHAPTER 3: WATERSHED CHARACTERIZATION ..................................................................................13 3.1. WATER RESOURCES ................................................................................................ 13 3.2. ECOREGION ............................................................................................................. 13 3.3. SOILS AND GEOLOGY .............................................................................................. 13 3.4. CLIMATE ................................................................................................................. 14 3.5. LAND USE ............................................................................................................... 14 3.6. FUTURE LAND USE ................................................................................................. 15 3.7. WATER QUALITY DATA .......................................................................................... 16 3.8. BIOLOGICAL MONITORING DATA............................................................................ 17 CHAPTER 4: BENTHIC STRESSOR ANALYSIS........................................................................................22 4.1. INTRODUCTION........................................................................................................ 22 4.2. ELIMINATED STRESSORS ......................................................................................... 23 4.3. POSSIBLE STRESSORS .............................................................................................. 26 4.4. MOST PROBABLE STRESSOR ................................................................................... 36 CHAPTER 5: THE REFERENCE WATERSHED MODELING APPROACH ................................................38 5.1. INTRODUCTION........................................................................................................ 38 5.2. TMDL REFERENCE WATERSHED SELECTION ......................................................... 38 5.2.1. Comparison of Potential Watersheds ............................................................. 38 5.2.2. TMDL Reference Watershed Selection ........................................................... 40 5.3. TMDL MODELING TARGET LOADS ........................................................................ 40 CHAPTER 6: MODELING PROCESS FOR TMDL DEVELOPMENT...........................................................41 6.1. SOURCE ASSESSMENT OF SEDIMENT ....................................................................... 41 6.1.1. Surface Runoff................................................................................................. 41 6.1.2. Channel and Streambank Erosion .................................................................. 41 6.1.3. Point Source TSS Loads.................................................................................. 42 6.2. GWLF MODEL DESCRIPTION.................................................................................. 42 6.3. SUPPLEMENTAL POST-MODEL PROCESSING............................................................ 44 6.4. INPUT DATA REQUIREMENTS .................................................................................. 45 6.4.1. Climate Data................................................................................................... 45 Benthic TMDL for Stroubles Creek in Montgomery County, Virginia i 6.4.2. Land Use ......................................................................................................... 45 6.4.3. Hydrologic Parameters................................................................................... 47 6.4.4. Sediment Parameters ...................................................................................... 48 6.5. ACCOUNTING FOR SEDIMENT POLLUTANT SOURCES............................................... 49 6.5.1. Surface Runoff................................................................................................. 49 6.5.2. Channel and Streambank Erosion .................................................................. 49 6.5.3. Point Source.................................................................................................... 49 6.6. ACCOUNTING FOR CRITICAL CONDITIONS AND SEASONAL VARIATIONS ................ 51 6.6.1. Critical Conditions ......................................................................................... 51 6.6.2. Seasonal Variability........................................................................................ 51 6.7. GWLF MODEL PARAMETERS ................................................................................. 52 CHAPTER 7: THE BENTHIC TMDL FOR SEDIMENT ................................................................................54 7.1. BACKGROUND......................................................................................................... 54 7.2. THE STROUBLES CREEK BENTHIC TMDL............................................................... 56 7.3. SUMMARY ............................................................................................................... 60 CHAPTER 8: BENTHIC TMDL IMPLEMENTATION ...................................................................................62 8.1. STAGED IMPLEMENTATION ..................................................................................... 62 8.2. LINK TO ONGOING RESTORATION EFFORTS ............................................................ 63 8.3. REASONABLE ASSURANCE FOR IMPLEMENTATION.................................................. 63 8.3.1. Follow-Up Monitoring.................................................................................... 63 8.3.2. Regulatory Framework ................................................................................... 64 8.3.3. Stormwater Permits ........................................................................................ 65 8.3.4. Implementation Funding Sources ................................................................... 66 CHAPTER 9: PUBLIC PARTICIPATION.....................................................................................................67