South Pacolet River Watershed Based Plan for Nutrient Load Reduction in Lake Bowen and Municipal Reservoir #1 Final Report March 2018 Table of Contents 1. Executive Summary ............................................................................................... 1-1 2. Watershed Management Plan Overview................................................................ 2-1 2.1 Overview .................................................................................................................................. 2-1 3. South Pacolet River Watershed ............................................................................. 3-1 3.1 Introduction .............................................................................................................................. 3-1 3.2 Hydrologic Characterization ..................................................................................................... 3-2 3.3 Demographic and Land Use .................................................................................................... 3-6 3.3.1 Land Use .................................................................................................................................. 3-6 3.3.2 Demographics ........................................................................................................................ 3-10 3.4 Regulatory Framework........................................................................................................... 3-11 3.4.1 Federal Clean Water Act and Upper Broad River TMDL ....................................................... 3-11 3.4.2 National Pollution Discharge Elimination System (NPDES) .................................................. 3-13 3.4.3 Surface Water Withdrawal ..................................................................................................... 3-13 4. Causes and Sources of Pollutant Load .................................................................. 4-1 4.1 Data Source and Inventory ...................................................................................................... 4-1 4.2 Water Quality Constituents of Interest ..................................................................................... 4-5 4.2.1 Nitrogen ................................................................................................................................... 4-5 4.2.2 Phosphorus .............................................................................................................................. 4-7 4.2.3 Sediment .................................................................................................................................. 4-7 4.2.4 Chlorophyll-a ............................................................................................................................ 4-9 4.2.5 Dissolved Oxygen .................................................................................................................... 4-9 4.3 Causes and Sources of Impairments ..................................................................................... 4-10 4.3.1 Sewer Infrastructure ............................................................................................................... 4-10 4.3.2 Non-Agricultural Fertilizer ...................................................................................................... 4-13 4.3.3 Development and Impervious Cover ..................................................................................... 4-14 4.3.4 Stream Erosion ...................................................................................................................... 4-16 4.3.5 Livestock Access to Surface Water ....................................................................................... 4-16 4.3.6 Atmospheric Deposition ......................................................................................................... 4-17 4.3.7 Soil Erosion ............................................................................................................................ 4-17 4.3.8 Lakeshore Alteration .............................................................................................................. 4-18 Spartanburg Water South Pacolet River WBP Final Report 4.3.9 Construction and Land Disturbance ...................................................................................... 4-20 4.3.10 Stakeholder Meeting .............................................................................................................. 4-20 4.4 Current Water Quality Conditions .......................................................................................... 4-23 4.4.1.1 Nitrogen Species .................................................................................................................... 4-26 4.4.1.2 Total Phosphorus ................................................................................................................... 4-29 4.4.1.3 Total Suspended Solids ......................................................................................................... 4-30 4.4.2 Lake Bowen and Municipal Reservoir #1 .............................................................................. 4-31 5. Load Reduction Identification ................................................................................. 5-1 5.1 Background Load Estimation ................................................................................................... 5-1 5.2 Monitored Load Estimation ...................................................................................................... 5-1 5.3 STEPL Load Estimation ........................................................................................................... 5-4 6. Management Strategies ......................................................................................... 6-5 6.1 Overview of Management Approaches.................................................................................... 6-5 6.1.1 Structural BMPs ....................................................................................................................... 6-8 6.1.1.1 Stream Restoration .................................................................................................................. 6-8 6.1.1.2 Vegetated Riparian Buffer ....................................................................................................... 6-8 6.1.1.3 Constructed Wetlands.............................................................................................................. 6-9 6.1.1.4 Bioretention / Rain Gardens .................................................................................................. 6-11 6.1.1.5 Downspout Disconnection ..................................................................................................... 6-11 6.1.1.6 Livestock Exclusion Fencing .................................................................................................. 6-12 6.1.1.7 Terracing ................................................................................................................................ 6-13 6.1.1.8 Enhanced Pasture Management ........................................................................................... 6-13 6.1.1.9 Rainwater Harvesting and Reuse .......................................................................................... 6-13 6.1.2 Non-Structural BMPs ............................................................................................................. 6-16 6.1.2.1 Residential Lawn Care ........................................................................................................... 6-16 6.1.2.2 Watershed Stakeholder and Homeowner Outreach .............................................................. 6-17 6.1.2.3 Septic Tank Management Program ....................................................................................... 6-17 6.1.2.4 Land Use Planning ................................................................................................................. 6-19 6.1.2.5 Land Conservation ................................................................................................................. 6-19 6.1.2.6 Forestry Land Management ................................................................................................... 6-20 6.2 Relative Load Reduction Efficiencies .................................................................................... 6-21 6.3 Costs and Benefits of Management Practices ....................................................................... 6-23 | Table of Contents i Spartanburg Water South Pacolet River WBP Final Report 7. Implementation ...................................................................................................... 7-1 7.1 Monitoring Plan ........................................................................................................................ 7-1 7.1.1 Overall Monitoring Schematic During Implementation ............................................................ 7-2 7.1.2 Stream Health .......................................................................................................................... 7-3 7.1.3 Lake Sedimentation ................................................................................................................. 7-3 7.1.4 Developed Area Stormwater Runoff ........................................................................................ 7-4 7.2 Financial and Technical