Rubble from the Alaskan Way Viaduct demolition will be put to good long-term use, filling the now-decommissioned Battery Street Tunnel in Seattle as part of the process of eliminating the former underground portion of State Route 99 in the city.
The decommissioning of the 3,140-ft-long tunnel, with work led by contractor Kiewit, has coincided with the demolition of the Alaskan Way Viaduct ever since the opening of the new State Route 99 tunnel under downtown Seattle. Initial work inside the Battery Street Tunnel included crews cleaning the tunnel of decades’ worth of automobile exhaust and removing the tunnel’s mechanical and electrical systems.
Crews will continue to install sewer lines and conduct other utility work, but this month the contractor has also started trucking in concrete rubble from the viaduct demolition and sending it into the tunnel, using funnels on Battery Street as a way to fill the tunnel. Crews removed the steel rebar from the viaduct rubble and crushed the concrete into baseball-sized pieces.
Inside the Battery Street Tunnel, crews will compact the concrete fill using a vibrating roller, work that will last at least three months as crew fill up to about 7 ft from the top of the tunnel.
Expect to see trucks dumping fill material through a specialized funnel on Battery Street during weekdays, while crews work on the vibration compaction work at the same time. Funnels and other construction equipment will be stored on Battery Street when not in use and those near the area may feel the vibration during the working hours.
Owner Washington State Dept of Transportation says the tunnel, similar to the Alaskan Way Viaduct, is seismically vulnerable and decommissioning it improves surface mobility by allowing three blocks of surface streets to be rebuilt into a two-way surface street with four-way intersections and bus lanes.
Once the Alaskan Way Viaduct closed in early 2019, the new State Route 99 alignment no longer required a run through the 1950s-built Battery Street Tunnel. Any new or continued use of the tunnel would have required prohibitively expensive renovations, so closing the tunnel allowed improvements in mobility throughout the area, says WSDOT.
WSDOT expects the work in the area to last into late 2020, including the filling of the tunnel and sealing of its entrances and then street restoration along Battery Street, including sidewalk improvements, new curb ramps, street lighting and more.
During the filling process, the lower half of the tunnel will receive the crushed concrete from the viaduct, trucked into the tunnel or poured in through grates in the roadway above. The top half of the tunnel will be filled with concrete pumped in from the surface.
Follow Tim Newcomb on Twitter at @tdnewcomb.