The countdown is on as Bertha, the SR 99 tunneling machine, mined into the 10th and final zone of the 9,270-foot tunnel drive this week. With 1,294 concrete tunnel rings installed in the ground behind her, Bertha is less than two blocks from the disassembly pit where her journey will end.How is the interior of the tunnel shaping up? And how is Bertha doing? It’s probably best if we show you. Click below to join Program Administrator Joe Hedges on a 360-degree tour of the project. Move your smartphone up and down to move around the tunnel. Or, if you’re on a computer, grab the picture with your mouse for a 360-degree view of the work that’s happening out of sight, underneath Seattle.Looking aheadIt’s still too early to predict when Bertha will reach the disassembly pit. Seattle Tunnel Partners’ most recent schedule shows that tunnel boring is slated to end in May, but mining rates will continue to vary based on maintenance needs and ground conditions.There’s still plenty of work to do after tunnel boring is complete. STP will begin disassembling the tunneling machine soon after the cutterhead breaks into the pit. They will remove the machine in small pieces and haul them away by truck, a process that will take several months.Meanwhile, crews will continue building the double-deck highway inside the tunnel. This work is completed in different stages, as shown in our weekly interior structures report. The roadway deck is now at the southern edge of Pike Place Market, or nearly 50 percent complete.Crews are also installing mechanical, electrical and plumbing systems that must be completed before the tunnel can open to traffic. This is a big job that is scheduled to last well into 2018.As construction continues, WSDOT and STP will begin an extensive commissioning program. This involves a series of thorough inspections, tests and quality verification procedures to ensure the tunnel systems are functioning properly.Based on STP’s schedule, the tunnel is projected to open in early 2019. Progress updates are posted on Mondays and Thursdays at our Follow Bertha page. You can also follow Bertha on Twitter @BerthaDigsSR99.— more —
Seattle Tunnel Partners resumed mining today after conducting additional survey work to verify Bertha’s position and to make necessary adjustments to complete the tunnel drive. Crews performed routine inspections and maintenance while mining was stopped, including the replacement of cutterhead tools.As of this afternoon, Bertha was tunneling north toward the intersection of Denny Way and Sixth Avenue North, less than 1,000 feet from the disassembly pit.STP stopped mining on Feb. 28 after survey data indicated the tunneling machine may be several inches off the tunnel alignment. Three independent surveys confirmed the 57.5-foot machine was approximately six inches off alignment.STP designers made a slight change to the tunnel alignment between the machine’s current location and the end of the tunnel drive. Adjustments are common during tunneling, including on this project. STP made a similar adjustment to correct Bertha’s course after the machine mined out of the access pit following repairs.Crews steer Bertha (links to YouTube) based on information they receive from its onboard guidance system. The system is now set to the new tunnel alignment.— more —
Seattle Tunnel Partners has temporarily stopped mining to prepare Bertha, the SR 99 tunneling machine, for the final 1,000 feet of the 9,270-foot tunnel drive.Crews stopped mining yesterday to verify Bertha’s position along the tunnel route before making their final push to the disassembly pit. Recent surveys show that Bertha may be several inches off of the tunnel alignment. STP is conducting additional survey work and will make adjustments as needed to complete the tunnel drive.Adjustments are common during tunneling, including on this project. STP made a similar adjustment to correct Bertha’s course after crews mined out of the pit that was used to access and repair the machine.Crews will continue to perform routine maintenance on the machine for the next several days. They plan to resume mining next week.According to STP’s most recent schedule, Bertha will arrive at the disassembly pit in May. The pit is located approximately 960 feet north of the cutterhead’s current location beneath Denny Way and Sixth Avenue North. Mining rates will continue to vary based on maintenance needs and soil conditions.Crews successfully mined under the final building of the tunnel drive earlier this week. Bertha has traveled a total of 8,310 feet and built 1,270 of 1,426 concrete tunnel rings.— more —
Clean air is a critical element of a safe and well-functioning tunnel. In the new SR 99 tunnel, a complex system of fans will push and pull air into and out of the tunnel to ensure fresh air during routine operations and in emergencies.
The first element of the tunnel’s ventilation system is the very traffic that uses it. Vehicles traveling through the tunnel will act like pistons, pushing fresh air into the tunnel. But when that piston effect needs a boost, the tunnel will turn to … more