The inner-workings of the SR 99 tunneling machine Bertha are now fully visible from the camera above the pit where disassembly continues. The upper shield that surrounded Bertha is now gone – lifted and hauled away. Only a small portion of the cutterhead spokes remain. Next, Seattle Tunnel Partners plans to remove work-deck platforms, hydraulic systems, hyperbaric equipment and ring-building equipment. Remember, there’s 8,000 tons of machinery inside the disassembly pit and inside the north end of the tunnel. This brief time-lapse video shows what seven weeks of nearly non-stop work looks like as workers continue dismantling the five-story-tall tunneling machine.
Seattle Tunnel Partners continues to work around the clock as they disassemble the SR 99 tunneling machine near Seattle Center. The face of the machine has dwindled in size as most of the cutterhead has been removed.
Crews are also removing more pieces of the machine’s outer shield, exposing inner parts that weren’t previously visible from the pit. This includes the articulation jacks, which allowed the machine to change direction as it pushed beneath downtown Seattle.
As work on the machine continues in the pit, disassembly is progressing from inside of the tunnel as well. STP is dismantling the trailing gear and disconnecting temporary utilities and ventilation that were necessary for the machine’s operations. These pieces are being removed through the south end of the tunnel. The below photos show disassembly progress, both in the disassembly pit and in the tunnel. Disassembly progress can also be tracked through the construction camera.
An STP worker assists the crane operator with the removal of a piece of the tunneling machine.
Removing pieces of Bertha’s shield reveals the inner-workings of the tunneling machine.
A welder cuts a section of the shield for removal.
Crews are also disassembling the machine from inside of the tunnel.
May 2017 aerial view of the tunneling machine in the disassembly pit.
Inside the tunnel, crews are hard at work on more than just removing the trailing gear. STP has now completed 66 percent of the southbound roadway and the corbels (wall foundations) are approaching the rear of the tunneling machine. The latest report tracking interior structures progress can be found in the information box on the Bertha page of our website.
The Alaskan Way Viaduct Replacement Program is more than just the tunnel – it is 32 projects that together will replace the viaduct with a new tunnel, highway connections, and a new Alaskan Way surface street. This month contractor Interwest Construction completed the South Dearborn Street off-ramp bridge, the 24th completed project of the viaduct replacement program.
Completed on time and on budget, this remarkable little bridge won’t have an immediate effect on anyone’s commute. The bridge currently stands isolated in the construction zone to the west of CenturyLink field. When the SR 99 tunnel is nearing completion, crews will connect this ramp to northbound SR 99, turning it into a northbound off-ramp to South Dearborn Street. After the tunnel opens, drivers heading to the stadiums or downtown Seattle will take this ramp.
What makes this bridge special is the earthquake technology it contains. As we’ve profiled in the past, this bridge is the first in the world to pilot-test a method for making bridges earthquake resistant. Its design uses memory-retaining metal rods and bendable concrete composite so the bridge flexes when the ground shakes, then snaps back into its original shape once the shaking ends. This video explains how this new technology works:
This off-ramp is one of several ways the AWV Replacement Program is improving Seattle’s resilience in the face of earthquakes. The viaduct is susceptible to earthquakes, and replacing it is, first and foremost, a safety project. Tunnels are one of the safest places to be in an earthquake because of the way they can move with the shifting ground, and the SR 99 tunnel is designed with earthquakes in mind. This post from 2016 explains how the SR 99 tunnel is built to withstand up to a 9.0 magnitude earthquake.
In the disassembly pit near Seattle Center, work is continuing around the clock - cutting, lifting and removing heavy pieces of the SR 99 tunneling machine. As of yesterday, eight small spokes and the bulk of five larger spokes have been taken out of the disassembly pit. More than 50 percent of the iconic cutterhead has now been removed. These recent photos capture the progress:
More than half of the cutterhead's spokes are now removed
Welders use torches to cut through the cutterhead in preparation for removing a spoke
All eight small spokes and most of the large spokes have been removed
This piece of a cutterhead spoke, lifted to the surface, weighs 99,000 pounds
Inside the tunnel, crews are dismantling the tunneling machine from the south end
Back sections of the shield have been removed, with more lifts to come (view looks north)
Crews are also working inside the tunnel to remove the tunneling machine and other pieces of the tunneling operation no longer needed now that the tunneling portion is complete. Seattle Tunnel Partners is removing conveyor system components which had been used to carry the dirt underneath Seattle out to waiting barges. Temporary utilities, hydraulic lines and hoses are also coming out. And STP has started disassembling the back end of the trailing cars that carried all the equipment for tunnel-building. In all, eight thousand tons of equipment will eventually be removed from Seattle’s new tunnel to clear the path for building the rest of the double-deck road inside.
Seattle Tunnel Partners has started lifting pieces of the SR 99 tunneling machine Bertha’s cutterhead out of the disassembly pit near Seattle Center. To date, three of the cutterhead’s eight small spokes have been cut and lifted from the pit.
This new video shows how workers use torches to cut the 57.5-foot-wide cutterhead into pieces. More than 35 lifts will be needed to remove the cutterhead alone – which weighs more than 900 tons. The full disassembly process is expected to last up to five months.
With one last push from her thrust jacks, Bertha came to rest today in her final position within the disassembly pit near Seattle Center. Seattle Tunnel Partners began slowly moving the tunneling machine forward on April 13. You can watch the machine’s progress into the pit by scrolling back through the disassembly pit time-lapse camera.
Nowhere to go but up (and out)
With Bertha’s movement complete, crews will begin disassembling and cutting the machine into pieces for removal. Some pieces will be lifted from the disassembly pit by crane, while others will be taken out south through the tunnel. A new fact sheet in our Program Library gives a brief overview of what this work entails.
As Bertha moved into the disassembly pit, crews also began removing infrastructure within the tunnel that supported tunneling. More than 20 miles of pipe has to be removed, as well as the yellow ventilation duct and the conveyor belt.
Video: Bertha's final push
While the time-lapse camera linked above captures the view from above the disassembly pit, this video provides an on-the-ground perspective. Watch a condensed time-lapse of Bertha's two-week move into the disassembly pit (with a pause for a group photo of the workers who built the tunnel).