Project Description

City of Tacoma began construction of a large 60-inch diameter interceptor stormwater pipeline and a new outfall into the Thea Foss Waterway in fall 2021. This project will improve existing storm sewer system capacity, help reduce flooding events, and support future growth in the downtown area. The project is anticipated to be complete in fall 2022.

The City hired a design build team of James W. Fowler Co. and Kennedy/Jenks Consultants to design and construct this new stormwater pipeline. See the map below for the project area.

Project Goals

• Address flooding that occurs in the lower downtown area due to capacity limitations in the existing stormwater system.

• Provide stormwater conveyance capacity for future growth in the downtown area.

• Deliver project improvements that represent the “best value” to Tacoma’s surface water ratepayers.

• Mitigate construction impacts on the downtown community, including adjacent local businesses and the public.

Construction Update (February 16, 2022)

1147 Dock Street: Crews have completed installing the bracing needed to stabilize underground structures that will support installation of a new stormwater pipe. Crews also completed building the new outfall that will serve as a discharge into the Thea Foss Waterway. Construction will continue at this location until fall 2022 to install the stormwater pipe, backfill the soil, and permanently restore the area. Below is a picture of crews working at night to install a portion of the new outfall into the Thea Foss Waterway. Crews conducted outfall work at night to take advantage of the lowest daily tides which help crews keep the work zone dewatered.

Location of Project

Construction will occur in the downtown area along S. 19th Street, Jefferson Avenue, S. 17th Street Prairie Line Trail, S 15th Street and A St., and Dock Street. All work will be done within the city right of way. 

Construction Methods

Most of the sewer pipe will be installed using open-cut construction. In open-cut construction, crews dig from the surface to the pipe, depth, lay the pipe, then cover the pipe and restore the surface. 

There are a few areas that require a trenchless or “microtunneling” method. This method does not require digging from the surface to the pipe depth. Instead, two shaft are built on either end of the pipe. Then the pipe is installed using a hammer, auger, drill, or microtunneling machine. This method is only feasible in certain types of soils and conditions.

We expect to use trenchless construction in the following places along the stormwater interceptor pipeline:

• Under Dock Street
• Under the BNSF railroad tracks
• Under the Pacific Avenue / Link Light Rail crossing 

Construction Impacts

Construction will start in late October 2021 and take approximately one year to complete. During construction you can expect:

• Weekday work hours, 7 AM – 5:30 PM. Minimal night and weekend work.
• Construction noise, dirt, and vibrations
• Lane restrictions
• Full street closures. Local access will be maintained.
• Pedestrian detours
• Parking and delivery restrictions

Project Benefits

This stormwater improvement project is an important part of the underground network of pipes that help reduce flooding in and around the downtown area. The City is replacing this pipe in efforts to improve existing storm sewer system capacity, help reduce flooding events, and sustainably support future growth in the downtown area.

Contact Information

For additional information, call the project hotline at (253) 279-5509 or email the project team.