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Agreement No: WQC-2017-Tukwil-00158 Page 2 of 34 <br /> Project Title: Stormwater Outfall Water Quality Retrofit Design <br /> Recipient Name: City of Tukwila <br /> administers the clean-up efforts.The Green River is listed as impaired for dissolved oxygen and temperature and has a <br /> Total Daily Maximum Load (TMDL) plan to address causes of the thermal pollution.The Green-Duwamish River is also <br /> home to threatened Chinook salmon and bull trout, as well as other species of anadromous fish, resident trout and <br /> other aquatic species. <br /> The RECIPIENT has identified a number of storm drain outfalls that discharge untreated stormwater to the Green- <br /> Duwamish River. Of these outfalls, seven have been identified as candidate water quality retrofit project areas for <br /> feasibility and alternatives analysis.The seven selected sites are representative of a number of other untreated basins <br /> draining to the Green-Duwamish River; therefore,the findings of this analysis can be used as a template for cost <br /> effective design and construction of future retrofits with similar conditions and challenges in the same area.These <br /> challenges include flat topography with low-gradient pipes; outfalls within the tidal influence zone; and highly urbanized <br /> area with potential utility conflicts. <br /> The RECIPIENT will evaluate the seven outfall areas and prioritize them based on land use,total area treated, anticipated <br /> runoff pollution levels within areas treated, cost, availability of right-of-way,and utility conflicts. Based on the findings <br /> from the feasibility and alternatives analysis of the seven outfalls,the RECIPIENT will complete 90-percent designs for a <br /> minimum of four outfall sites. <br /> Overall Goal: (1,000 character limit, includes spaces) <br /> This project will help protect and restore water quality in Washington by reducing stormwater impacts from existing <br /> infrastructure and development. <br /> 20 <br />