Loading Analysis Plan and Supporting Data Acquisition Needed for the Stillwater River Basin Total Maximum Daily Load Development Ludlow Falls in the Stillwater River Watershed on March 13, 2013. Ohio EPA Technical Report AMS/2013‐STILR‐3 Division of Surface Water Assessment and Modeling Section January 2021 TMDL DEVELOPMENT | AMS/2013‐STILR‐3 Loading Analysis Plan – Stillwater River Basin January 2021 Table of Contents Introduction ................................................................................................................................................................................................................. 3 Aquatic Life Use .......................................................................................................................................................................................................... 3 Evaluation of Biocriteria ................................................................................................................................................................................... 3 Proposed Targets ............................................................................................................................................................................................... 16 Recreation Use .......................................................................................................................................................................................................... 16 Evaluation of Criteria ....................................................................................................................................................................................... 16 Proposed Actions ............................................................................................................................................................................................... 18 References .................................................................................................................................................................................................................. 20 Appendix A ................................................................................................................................................................................................................. 21 Appendix B ................................................................................................................................................................................................................. 30 Appendix C ................................................................................................................................................................................................................. 35 2 AMS/2013‐STILR‐3 Loading Analysis Plan – Stillwater River Basin January 2021 Introduction This document provides an overview of the information considered in proposing the strategy to address water quality impairments in the Stillwater River watershed. These recommendations are based on data collected as part of a biological and water quality study in 2013. A description of the project area, sites, data types and methods can be found in the Stillwater River Basin study plan document at epa.ohio.gov/Portals/35/tmdl/StillwaterRFinalStudyPlan_06052013.pdf. A summary of the study results can be found in the biological and water quality report at epa.ohio.gov/Portals/35/documents/Stillwater_River_Basin_TSD_2013.pdf. Sites in the Stillwater River watershed were assessed for aquatic life use, recreation use and water supply use. The attainment of aquatic life and recreation use is based on specific restoration targets. This document examines those targets and lays out proposals for addressing each impairment. Where appropriate, methods are outlined to develop total maximum daily loads (TMDLs) for specific pollutants. The Stillwater River watershed was previously assessed in 1999 and the results of that survey are published at epa.ohio.gov/portals/35/documents/Stillwater1999TSD.pdf . A TMDL report was developed based on the results in the first survey and published in 2004 (epa.ohio.gov/portals/35/tmdl/StillwaterTMDL_final.pdf). Subsequent to the 2004 report Ohio EPA decided to recompile the report at a finer resolution. The finer resolution gave results that were more reliable to predict the amount of pollution the watershed could assimilate while still maintaining water quality standards. The finer scale TMDLs were approved and published in 2009 epa.ohio.gov/portals/35/tmdl/StillwaterTMDL_final_aug09.pdf. Aquatic Life Use Evaluation of Biocriteria Attainment of Ohio EPA’s biocriteria are based on fish and macroinvertebrate scores, as measured by the Index of Biotic Integrity (IBI), Modified Index of well-being (MIwb) and Invertebrate Community Index (ICI). Numeric goals for those indices are codified in rule (Ohio Administrative Code (OAC) 3745-1-07, Table 7-1) for exceptional warm water habitat (EWH), warm water habitat (WWH) and modified warmwater habitat (MWH). The numeric criteria that apply to the Stillwater River watershed are shown in Table 1. The 1999 assessment evaluated 141 sites with 77 (55%) meeting the expectations for aquatic life use (ALU). The remaining sites were either in partial or non-attainment of the designated ALU. The attainment status for each site is shown in Table A1 and the scores for impaired sites are shown in Table C1. The basin was re-surveyed in 2013 and 96 sites were assessed, with 67 (70%) meeting the designated ALU. Again, the remaining sites were either in partial or non-attainment of the designated ALU. The attainment status for each site is shown in Figure 2 and scores for impaired sites are shown in Table B1. The reduction in sites between the two surveys was principally due to a reduction in sampling of small headwater sites (~<3.0 mi2). The purpose of sampling these sites in the earlier survey was to document the appropriate ALU designation. The recommendations made in the previous survey were incorporated into the water quality standards beneficial use designation rule OAC 3745-1- 21. 3 AMS/2013‐STILR‐3 Loading Analysis Plan – Stillwater River Basin January 2021 Table 1 – Biological criteria applicable in the Stillwater River watershed for aquatic life use designations. Biological Criteria for the Applicable Aquatic Life Use Biological Assessment Ecoregion Designations1 Index Method2, 3 EWH WWH MWH4 Headwater 50 40 24 IBI Wading 50 40 24 Eastern Boat 48 42 24 / 30 Cornbelt Wading 9.4 8.3 6.2 Plains (ECBP) MIwb Boat 9.6 8.5 5.8 / 6.6 ICI All5 46 36 22 1 Aquatic Life Use (ALU) designations: warmwater habitat (WWH); exceptional warmwater habitat (EWH); modified warmwater habitat (MWH) 2 The assessment method used at a site is determined by its drainage area (DA) for headwaters (<20 mi2) and the split between wading sites and boat sites being defined by the necessary sampling equipment, but generally sites with DA >500 mi2 being boat sites 3 MIwb not applicable to drainage areas less than 20 mi2 (headwater sites). 4 Biocriteria depend on type of MWH. MWH‐C (due to channelization) is listed first and MWH‐I (due to impoundment) is listed second. 5 Limited to sites with appropriate conditions for artificial substrate placement. AMS/2013‐STILR‐3 Loading Analysis Plan – Stillwater River Basin January 2021 Figure 1 – Map summarizing ALU attainment status in the Stillwater River watershed in 1999. 5 AMS/2013‐STILR‐3 Loading Analysis Plan – Stillwater River Basin January 2021 Figure 2 — Map summarizing ALU attainment status in the Stillwater River watershed in 2013. 6 AMS/2013‐STILR‐3 Loading Analysis Plan – Stillwater River Basin January 2021 Proposed Actions Ohio EPA considers many factors when deciding how to address impairments. For some projects, no TMDL is required. The sites within the watershed may be in attainment, or the impairment is being addressed by another program or entity so no further action by the Division of Surface Water (DSW) is necessary. Additionally, the cause of impairment may be natural (i.e., flow or habitat), in which case no action is required. For those needing a TMDL, the complexity of each impairment — including the primary origin of the pollutant, its delivery mechanisms and the waterbody kinetics involved — will determine the complexity needed in a model. Ohio EPA must also take into consideration ongoing efforts in the watershed, previous TMDL analyses, the questions to be answered by a model and the amount of effort required to complete the model. Depending on the method selected, the Agency may be required to return to the watershed and collect additional data, and it is possible the modeling approach may change. A summary of Ohio EPA’s preliminary modeling approaches is presented in Table 3. Watershed Updates The assessment detailed in this loading analysis plan was follow-up to a survey that was completed in 1999-2000 (Ohio EPA, 2001). The earlier assessment culminated in a final TMDL report published in 2004 (Ohio EPA, 2004) and revised in 2009 (Ohio EPA, 2009). The efforts resulted in total phosphorus (TP) TMDLs to address nutrient impairment and an analysis of habitat where channelization was a cause of impairment. The 2013 assessment mirrored the earlier conditions as far as the types of impairment but with incremental and statistically significant improvement (Ohio EPA, 2015). Given the existing TMDL for nutrients, mirrored impairment due to nutrients and positive progress