The Tunnel Boring Machine “MudHoney” has broken through on the Ship Canal Water Quality Project in Seattle, Washington, completing excavation of the storage tunnel. The machine which is an Earth Pressure Balance Machines (EPBMs) has tunneled 2.64miles (4.25km) from Ballard to Wallingford where it emerged in a flooded shaft to prevent groundwater flowing in. The shaft will be emptied and the TBM will be dismantled once it has installed the last few tunnel segments. Earlier this year, the remote-controlled TBM Bertha dug the conveyance tunnel, and concrete was injected around the shaft to prevent the flow of groundwater. For TBM MudHoney, however, the limited working space meant flooding the shaft was a better solution.

Along the 2.64miles tunnel path, there are five vertical shafts at Ballard, East Ballard, Fremont, Queen Anne, and Wallingford that will collect stormwater and sewage flows from each basin and send them approximately 39-82feet (12-25m) below ground into the new storage tunnel.

The conveyance tunnel under the Ship Canal connects the vertical shafts in Queen Anne and Fremont. As a last step, new pipes will be installed to connect the existing sewer systems to the new shafts.

Gall Zeidler Consultants (GZ) is responsible for the detailed design of the excavation and support of the two adit tunnels which connect the drop shafts at 11th Ave. and Fremont, to the bored tunnel. The design scope includes the temporary support measures for the openings in the segmental lining. GZ has also provided technical support as expert geotechnical/tunnel consultant, regarding a large boulder encountered by the TBM and the design of an intervention chamber to carry the necessary repair works of the damage caused to the cutterhead by the boulder.

For complete Tunnels Online article, visit this site. If you are interested in GZ’s involvement with the project, visit our project page.

Breakthrough of the TBM (Courtesy of tunnelsonline.info)