Hammer Creek Headwaters Alternate Restoration Plan Lebanon County, Pennsylvania Prepared by: Accepted by EPA April 26, 2021 TABLE OF CONTENTS EXECUTIVE SUMMARY......................................................................................................................................................................................... 1 INTRODUCTION ...................................................................................................................................................................................................... 1 Table 2. Aquatic-Life Impaired Stream Segments in the Hammer Creek Headwaters Subwatershed per the 2018 Final Pennsylvania Integrated Report ....................................................................................................................... 3 Figure 1. Hammer Creek Headwaters Subwatershed. .............................................................................................. 4 Figure 3. Example stream segments illustrating upper Hammer Creek’s potential as a trout fishery ...................... 6 Table 3. Existing NPDES-Permitted Discharges in Hammer Creek Headwaters Subwatershed. ............................... 7 ARP APPROACH ....................................................................................................................................................................................................... 7 SELECTION OF THE REFERENCE WATERSHED ....................................................................................................................................... 8 Figure 4. Ontelaunee Creek Subwatershed. .............................................................................................................. 9 Table 4. Comparison of the Impaired (Hammer Creek Headwaters) and Reference (Ontelaunee Creek) Subwatersheds. ....................................................................................................................................................... 10 Table 5. Existing NPDES-Permitted Discharges in the Ontelaunee Creek Subwatershed and their Potential Contribution to Sediment Loading. ......................................................................................................................... 11 Figure 5. Example stream segments in the Hammer Creek Headwaters Subwatershed with heavy sediment deposition. .............................................................................................................................................................. 13 Figure 6. Example agricultural practices in the Hammer Creek Headwaters Subwatershed that may result in excessive sediment loading ..................................................................................................................................... 14 Figure 7. Example stream segments in the Hammer Creek Headwaters Subwatershed with obvious bank erosion and potential legacy sediment accumulations........................................................................................................ 15 Figure 8. Example buffered headwater and mainchannel stream segments in the Ontelaunee Creek reference subwatershed. ......................................................................................................................................................... 16 Figure 9. Example agricultural practices in the Ontelaunee Creek Subwatershed that may lead to excessive sediment loading. .................................................................................................................................................... 17 COMPARISON OF FINE SEDIMENT DEPOSITS IN THE IMPAIRED AND REFERENCE WATERSHEDS .......................... 18 Figure 11. Sediment sampling reach within the Ontelaunee Creek Subwatershed................................................. 20 Figure 12. Mean (+/- sd) depth of fine sediment deposits in pools of the Hammer Creek (impaired) and Ontelaunee Creek (reference) subwatersheds. ....................................................................................................... 21 Figure 13. Mean (+/- sd) proportion of sampling points dominated by <2mm (sieve size) deposits within riffles of the Hammer Creek (impaired) and Ontelaunee Creek (reference) subwatersheds. ............................................... 21 HYDROLOGIC / WATER QUALITY MODELING ....................................................................................................................................... 22 Figure 14. Riparian buffer analysis in the Hammer Creek Headwaters Subwatershed ........................................... 25 Figure 15. Riparian buffer analysis in the Ontelaunee Creek reference subwatershed .......................................... 26 CALCULATION OF THE ALLOWABLE LOADING RATE ....................................................................................................................... 27 ii Table 6. Existing Annual Average Loading Values for Ontelaunee Creek Subwatershed, reference ...................... 27 Table 7. Existing Annual Average Loading Values for the Hammer Creek Headwaters Subwatershed, impaired . 28 Table 8. Annual Average Allowable Loading for the Hammer Creek Headwaters Subwatershed ......................... 28 CALCULATION OF THE SOURCE LOAD ALLOCATIONS ...................................................................................................................... 28 CALCULATION OF THE UNCERTAINTY FACTOR AND SOURCE LOAD ............................................................................................... 29 CALCULATION OF THE ADJUSTED SOURCE LOAD ...................................................................................................................... 29 Table 9. Source Load, Loads Not Reduced and Adjusted Source Load as Annual Averages ................................... 29 CALCULATION OF SEDIMENT LOAD REDUCTIONS BY SOURCE SECTOR ................................................................................. 30 Table 10. Sediment Load Allocations for Source Sectors in the Hammer Creek Headwaters Subwatershed, Annual Average Values ....................................................................................................................................................... 30 CONSIDERATION OF CRITICAL CONDITIONS AND SEASONAL VARIATIONS ......................................................................... 31 AN ANALYSIS OF POSSIBLE BMPS ............................................................................................................................................................... 31 Figure 16. Proposed physical BMPs in the Hammer Creek Headwaters Subwatershed. Note that other BMP opportunities may exist in other areas and it is not intended to limit physical BMPs to only those opportunities shown on this map. ................................................................................................................................................. 33 Table 12. Cost analysis of BMP opportunities. All costs are reported as dollars. .................................................... 34 Figure 17. Estimated total annualized cost per pound of sediment removed per year for BMPs. .......................... 35 AGRICULTURAL EROSION AND SEDIMENTATION CONTROL PLANS ............................................................................................... 35 CONSERVATION TILLAGE .................................................................................................................................................... 36 COVER CROPS .................................................................................................................................................................. 37 CONVENTIONAL RIPARIAN BUFFERS ...................................................................................................................................... 37 PRECISION GRASS FILTER STRIPS .......................................................................................................................................... 39 Figure 18. Drainage networks within the Hammer Creek Headwaters Subwatershed. .......................................... 40 Figure 19. Drainage networks with flowlines and land use. ................................................................................... 41 Figure 20. Key drainagesheds with proposed precision grass buffers..................................................................... 42 Table 13. Contribution of sediment from each drainageshed to the subwatershed total and predicted % sediment removal by the precision buffers for the 1-yr and 5-yr storms. ............................................................................... 43 Table 14. Sediment reduction credit for installing 50-foot wide (or 15m) tall grass buffers on each side of the drainagelines as shown in Figure 16. ...................................................................................................................... 45 STREAMBANK STABILIZATION/STREAM RESTORATION .............................................................................................................. 45 Figure 21. Proposed comprehensive stream restoration site (NHD flowline shown as orange dates) in the Hammer Creek Headwaters Subwatershed. .......................................................................................................................... 47 GRAZING LAND MANAGEMENT ..........................................................................................................................................