Bacteria TMDL for Piney Run Loudoun County, Virginia Submitted by Virginia Department of Environmental Quality May, 2004 (Revised) Piney Run Bacteria TMDL TABLE OF CONTENTS Executive Summary...................................................................................................................................... iii 1. Introduction .............................................................................................................................................. 1 2. Physical Setting ....................................................................................................................................... 2 2.1. Listed Water Bodies.......................................................................................................................... 2 2.2. Watershed......................................................................................................................................... 2 2.2.1. General Description.................................................................................................................... 2 2.2.2. Geology, Climate, Land Use ...................................................................................................... 4 3. Description of Water Quality Problem/Impairment .................................................................................. 8 4. Water Quality Standard ......................................................................................................................... 11 4.1. Designated Uses............................................................................................................................. 11 4.2. Applicable Water Quality Criteria.................................................................................................... 11 5. Assessment of Bacteria Sources........................................................................................................... 13 5.1. Bacteria Source Tracking (BST) ..................................................................................................... 13 5.2. Point Sources.................................................................................................................................. 14 5.3. Non-Point Sources.......................................................................................................................... 15 5.3.1. Humans and Pets..................................................................................................................... 15 5.3.2. Livestock .................................................................................................................................. 17 5.3.3. Wildlife...................................................................................................................................... 18 6. TMDL Development............................................................................................................................... 20 6.1. Load-Duration Curve....................................................................................................................... 20 6.1.1. Flow Data ................................................................................................................................. 20 6.1.2. Flow-Duration Curves............................................................................................................... 21 6.1.3. Load-Duration Curve ................................................................................................................ 22 6.2. TMDL .............................................................................................................................................. 24 7. Allocations ............................................................................................................................................. 26 7.1. Consideration of Critical Conditions................................................................................................ 27 7.2. Consideration of Seasonal Variations............................................................................................. 27 8. Implementation and Reasonable Assurance......................................................................................... 28 8.1. TMDL Implementation Process....................................................................................................... 28 8.2. Stage I Implementation Goal .......................................................................................................... 29 8.3. Link to Ongoing Restoration Efforts............................................................................................... 31 8.4. Reasonable Assurance for Implementation................................................................................... 31 8.4.1. Follow-Up Monitoring ............................................................................................................... 31 8.4.2. Regulatory Framework ............................................................................................................. 31 8.4.3. Implementation Funding Sources ............................................................................................. 31 8.4.4. Wildlife Contributions and Water Quality Standards ................................................................ 32 9. Public Participation ................................................................................................................................ 33 10. References .......................................................................................................................................... 34 Appendix A ................................................................................................................................................. 35 Appendix B ................................................................................................................................................. 44 Appendix C ................................................................................................................................................. 46 Appendix D ................................................................................................................................................. 48 Appendix E ................................................................................................................................................. 51 i Piney Run Bacteria TMDL LIST OF TABLES Table Exec-1. TMDL for the Piney Run watershed (cfu/yr) ......................................................................................iv Table 1. Impaired segment description (Piney Run) ............................................................................................... 2 Table 2. Climate summary for Lincoln, Virginia (444909) ....................................................................................... 6 Table 3. Land use in the Piney Run watershed ....................................................................................................... 6 Table 4. Fecal coliform data collected by DEQ on Piney Run ................................................................................ 8 Table 5. Applicable water quality standards........................................................................................................... 12 Table 6. Piney Run bacteria source tracking results (1APIA001.80).................................................................... 14 Table 7. VPDES point source facilities and loads ................................................................................................. 15 Table 8. Estimated fecal coliform production from humans and pets in the Piney Run watershed................. 17 Table 9. Estimated annual fecal coliform production from livestock in the Piney Run watershed .................. 18 Table 11. Estimated fecal coliform production from wildlife in the Piney Run watershed ................................ 19 Table 12. Average annual E. coli loads and TMDL for Piney Run watershed (cfu/yr) ........................................ 25 Table 13. TMDL and required reduction for Piney Run.......................................................................................... 26 Table 14. Average annual load distribution, reduction, and allowable load by source ..................................... 27 Table 15. Load Reductions and WQS Violation Rates ........................................................................................... 29 Table 16. Phase I Load Allocations (based on a 70% reduction) ......................................................................... 30 Table 17. Reduction Attained by Eliminating Anthropogenic Contributions...................................................... 30 Table E-1. Average annual E. coli loads and TMDL for Piney Run watershed (cfu/yr)....................................... 52 Table E-2. TMDL and required reduction for Piney Run ........................................................................................ 52 Table E-3. Average annual load distribution, reduction, and allowable load by source.................................... 52 LIST OF FIGURES Figure 1. Map of the Piney Run watershed .............................................................................................................. 3 Figure 2. Topography in the Piney Run watershed Figure 3. Major soil groups in the Piney Run watershed Figure 4. Land Use in the Piney Run Watershed