Conewago Creek Watershed Implementation Plan Update Plan Sponsors: Tri-County Conewago Creek Association Report Prepared by: January 2021 Contents Figures ......................................................................................................................................................... ii Tables .......................................................................................................................................................... iii Acronyms and Abbreviations .................................................................................................................... v Units of Measure ......................................................................................................................................... v 1. Introduction and Project Background ......................................................................................... 1 1.1 Previous Watershed Planning in the Conewago Creek Watershed ............................................. 1 1.2 Clean Water Act Section 319 Eligibility ......................................................................................... 3 2. Watershed Description .................................................................................................................. 4 2.1 Land use ........................................................................................................................................ 5 2.2 Soils ............................................................................................................................................... 8 2.3 Topography and drainage ........................................................................................................... 10 2.4 Population and Jurisdiction ........................................................................................................ 11 3. Water Quality ................................................................................................................................ 11 3.1 Water Quality Standards and Assessment Status ...................................................................... 11 3.2 Total Maximum Daily Loads (PSU 2001) ..................................................................................... 16 3.3 Water Quality Data ..................................................................................................................... 17 3.3.1 Department of Environmental Protection ........................................................................ 17 3.3.2 Dauphin County ................................................................................................................ 18 3.3.3 U.S. Geological Survey ...................................................................................................... 19 3.3.4 Conewago Creek Initiative ................................................................................................ 21 3.4 Key USGS Studies ........................................................................................................................ 22 3.4.1 SPARROW Modeling of the Northeast .............................................................................. 22 3.4.2 Spatial and Temporal Variability in Showcase Watersheds (Hyer et al. 2016) ................. 23 4. Pollutant Sources and Critical Areas ......................................................................................... 24 4.1 Sources of Phosphorus ............................................................................................................... 24 4.2 Sources of Sediment ................................................................................................................... 26 4.3 Critical Areas ............................................................................................................................... 28 5. Previous Water Quality Improvement Practices ....................................................................... 30 5.1 Federally Funded Practices ......................................................................................................... 30 5.2 Surveyed Practices ...................................................................................................................... 32 5.3 Ongoing Implementation Project – Conewago Creek Floodplain Restoration Site ................... 32 6. Management Measures to Meet TMDL Load Reductions ........................................................ 34 6.1 Modeling Load Reductions of Recommended Practices ............................................................ 34 6.2 Overall Load Reductions ............................................................................................................. 37 7. Funding and Technical Resources ............................................................................................ 38 7.1 Partners ...................................................................................................................................... 38 7.2 Estimated Costs .......................................................................................................................... 39 7.3 Funding ....................................................................................................................................... 43 i 8. Education and Outreach.............................................................................................................. 48 8.1 Existing Education and Outreach ................................................................................................ 48 8.2 Additional Education and Outreach Needs ................................................................................ 49 9. Schedule and Milestones ............................................................................................................ 49 10. Evaluating Progress and Adaptive Management ..................................................................... 53 11. Monitoring Plan ............................................................................................................................ 55 12. References .................................................................................................................................... 61 Appendix A – ATTAINS Impairment Listings ......................................................................................... 63 Appendix B – Water Quality Data ............................................................................................................ 78 Appendix C – Local Sponsor Watershed Issues and Concerns .......................................................... 82 Appendix D – BMP Practice Recommendations .................................................................................... 83 Appendix E – Model My Watershed Outputs........................................................................................ 109 Appendix F. Conewago Creek Monitoring Plan ................................................................................... 151 Figures Figure 1. Conewago Creek subwatersheds. .................................................................................................. 5 Figure 2. Land Use in the Conewago Creek Watershed (NLCD 2011). ......................................................... 7 Figure 3. Soils in the Conewago Creek Watershed (NRCS SSURGO). ............................................................ 9 Figure 4. Conewago Creek Watershed topography (USDA NRCS 2020). .................................................... 10 Figure 5. Category 4a streams in the Conewago Creek Watershed. .......................................................... 13 Figure 6. Category 4c streams in the Conewago Creek Watershed. .......................................................... 14 Figure 7. Category 5 streams in the Conewago Creek Watershed. ............................................................ 15 Figure 8. TMDL subbasins A and B in the Conewago Creek Watershed (Image from PSU 2001). ............. 16 Figure 9. Macroinvertebrate IBI scores in Conewago Creek Watershed (2012-2013 and 2019) ............... 18 Figure 10. Total phosphorus load and concentration in the Conewago Creek Watershed (USGS 2012 synoptic sampling). ............................................................................................................................ 19 Figure 11. TSS load and concentration in the Conewago Creek Watershed (USGS synoptic sampling). ... 20 Figure 12. Species richness and abundance in Conewago headwaters (figure from Kyler and Hill 2018). 21 Figure 13. Species richness and abundance for Hersey Meadows (figure from Kyler and Hill 2018). ....... 21 Figure 14. Fish species richness and abundance near the mouth of the Conewago (figure from Kyler and Hill 2018). ........................................................................................................................................... 22 Figure 15. Total phosphorus yield (kg/km2) SPARROW results for the Conewago Creek subwatershed... 23 Figure 16. Conewago Creek showcase watershed (Hyer et al. 2016). ........................................................ 23 Figure 17. Nonpoint sources of phosphorus in the Conewago Creek Watershed (Model My Watershed). ............................................................................................................................................................ 24 Figure 18. Nonpoint sources of phosphorus by subwatershed in the Conewago Creek Watershed