Bertha's scheduled maintenance stop
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Bertha Demo Period Done, Resumes Mining

The Bertha tunnel boring machine has resumed chewing away beneath Seattle after a ‘suspension for cause’ order from WSDOT shut it down in January following two safety incidents. The BTM began tunneling with some conditions […]

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Bertha TBM Begins Moving

WSDOT reported that Bertha has slowly began moving again. It must tunnel through 20 feet of unreinforced concrete with its broken seal to break through into the rescue shaft. Once that happens, the repairs to […]


Malcolm Drilling's clamshell bucket taking a scoop out while excavating the access pit
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Update on Access Pit for Repairing Bertha TBM

There hasn’t been much to report recently for the Alaskan Way Viaduct Tunnel Project in Seattle. As you probably know, Bertha has not advanced since about December of 2013 after drilling through an abandoned steel […]


SR 99 tunnel concept
Available Resources

Seattle breaks ground on S.R. 99 tunnel

FHWA Director Mendez was on hand last month as WSDOT broke ground on the SR 99 tunnel, also known as the Alaskan Way Viaduct Replacement Tunnel. The project is expected to cost upwards of $2B […]


Seattle tunnel cross-section
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Seattle tunnel will go under 158 buildings

The tunnel replacing the Alaskan Way Viaduct (SR-99) will pass beneath 158 existing structures requiring an extensive program of vibration and settlement monitoring as well as some remediation. Of the 158 buildings, WSDOT identified 20 […]