The project is located near downtown Renton, south of the Cedar River and west of Interstate 405. The project area is approximately 3.17 acres, located entirely within the City of Renton Right-of-Way on Burnett Ave S and Williams Ave S between 2nd Street S and the Cedar River. S Tobin Street between Burnett Ave S and Williams Ave S. Burnett Ave S and Williams Ave S are located within the city’s Center Downtown area and are lined by various commercial businesses and other mixed-use properties and contain several other public and private utilities. The location is zoned CD–Center Downtown.
The existing roadways within the project area have concrete sidewalks, planters, curbs, and gutters. The current storm drainage system consists of catch basins, manholes, and mostly eight-inch diameter concrete conveyance pipes installed in the 1950s. A single 12-inch diameter concrete outfall conveys drainage freely from the project area to the Cedar River. There are no water quality or flow control facilities within the project area. Large storms increase the risk of flooding within the project area, particularly at the 95 Burnett S apartments. A predecessor to this project was the Renton Downtown Utility Improvements Project (DUIP) in 2018, which identified stormwater conveyance deficiencies in the downtown area.
At the outfall from the project area, the Cedar River is listed in the Department of Ecology’s 303(d) impaired water bodies as a Category 5 for pH, temperature, and dissolved oxygen and a Category 2 for mercury. The project area lies within the city’s Aquifer Protection Area Zone 1 for one-year capture, prohibiting infiltration as a water quality treatment option.
This project consists of storm drain system improvements to address known areas of flooding within the project area by upsizing existing undersized pipes in Burnett Ave S, Williams Ave S, and S Tobin St to meet the current city storm drainage design guidelines and address identified deficiencies in pipe condition and material. Additionally, the project will improve water quality in the Cedar River watershed by installing two modular wetland facilities within the public right-of-way, one in S Tobin St and one in Williams Ave S, that will provide treatment of stormwater runoff from over 12 acres of developed land. Sanitary sewer improvements are also planned within a portion of Burnett Ave S as part of this project to improve clearance from the proposed storm system and replace pipes that have reached their useful lifespan. Removal and in-kind restoration of asphalt surfacing, concrete sidewalks, and other surface features necessary to install the proposed improvements will also occur as part of the project.