Shilshole tunnel work resumes as next phase of Ship Canal project gets underway

Construction is ramping back up in Ballard as crews begin the next phase of tunneling for the Ship Canal Water Quality Project following the end of the FIFA World Cup construction moratorium along Shilshole Avenue NW.

The Ship Canal Water Quality Project is a Seattle Public Utilities and King County project to reduce polluted stormwater and sewage overflows into the Lake Washington Ship Canal, Salmon Bay, and Lake Union by capturing and storing them in a new underground tunnel during heavy rains.

According to Seattle Public Utilities’ August construction update, utility work to install the Ballard pump station discharge pipe has resumed southeast of 24th Avenue NW along Shilshole Avenue NW. The pump station will pump stormwater and sewage stored in the project’s underground tunnel into pipes leading to King County’s West Point Wastewater Treatment Plant in Magnolia near Discovery Park for treatment.

During regular work hours, one lane of traffic in each direction will generally remain open, though drivers may encounter lane shifts and flaggers directing traffic through the work zone.

The project also reached a milestone last month with the completion of the first phase of tunneling. This month, tunnel boring machine “Margo” is beginning the second phase of tunneling beneath NW 56th Street. The machine is expected to reach the intersection of 28th Avenue NW and NW 56th Street later this year.

As tunneling continues, Seattle Public Utilities says contractors will begin strictly enforcing no-parking zones along NW 56th Street starting in August. The restrictions are intended to ensure crews have access to monitoring points and underground structures while tunneling is underway.

Traffic control measures will remain in place at the intersection of 24th Avenue NW and NW 56th Street, with one northbound lane and one southbound lane maintained.

At 28th Avenue NW and NW 56th Street, crews completed excavation of the diversion structure and poured the concrete base last month. The next phase includes preparing pipe connections and readying the site for the arrival of the tunnel boring machine. The breakthrough at that location is expected before the end of the year.

Work also continues at the Ballard pump station. Inside the facility, crews are pouring concrete for floors and walls and installing rails for the internal crane system. Outside, construction continues on the tower’s exterior walls, along with steel and roof decking installation.

During construction, neighbors can expect:

• Trucks transporting materials to and from the site.
• Construction-related noise, vibration and equipment.
• Periodic temporary noise variances for specific work activities.
• Vehicle, pedestrian and bicycle detours.
• Increased traffic as drivers adjust to detour routes.

Seattle Public Utilities says contractors will continue monitoring noise, vibration and dust to remain within permitted limits and will use measures such as covering truckloads, washing vehicle tires and watering work areas when needed.

Featured photo: Rendering of future Ballard Pump Station / Seattle Public Utilities