The focus of this presentation is to outline the development of Washington State’s first bioassessment TMDL. Under section 303(d) of the Clean Water Act and supporting regulations (40 CFR 130.7), states are charged with developing a list of impaired and threatened waters requiring a Total Maximum Daily Load (TMDL). Impaired waters are those not meeting one or more of the applicable Water Quality Standards, including designated uses, narrative criteria and numeric criteria. If biological assessment indicates a waterbody is impaired, the waterbody is included on the state’s section 303(d) list and prioritized for TMDL development. The Soos Creek watershed has Category 5 listings for temperature and dissolved oxygen and the upcoming draft Water Quality Assessment will have three Category 5 listings for bioassessment. The goal of this TMDL is to protect the aquatic life uses through implementation of allocations that address temperature, dissolved oxygen and aquatic health impairments in the basin. The aquatic life uses being protected include the five species of Pacific salmon (Chinook, coho, chum, pink and sockeye), steelhead and cutthroat trout, and a diverse benthic macroinvertebrate community consisting of long-lived and pollutant intolerant species. The Clean Water Act calls for an integrated strategy to restore the physical, chemical, and biological integrity of surface waters. Bioassessment will enhance the DO and temperature TMDLs and provide an important tool to measure improvements in the aquatic life use. This innovative aquatic health TMDL consists of selecting a target B-IBI score to fully support beneficial uses and develop hydrologic allocations and achievable implementation measures within the Soos Creek watershed. The purpose of this presentation is to talk about the process, challenges, approaches and solutions used to develop the first bioassessment TMDL in Washington State
