AASHTO Journal, 31 October 2014
Work to rescue and repair the world’s largest tunnel boring machine was suspended Oct. 23 on Seattle’s Alaskan Way Viaduct Replacement project, after diggers of an excavation shaft toward the stalled machine found shell material.
Initial reports said the discarded shells, found about 20 feet from the surface just days into the digging, could be evidence of indigenous tribes or early settlers along the shores of Elliott Bay. The Washington State Department of Transportation said the material “requires further evaluation and may indicate the presence of cultural materials,” but that “no artifacts or human remains were found.”
Later, state preservation officials were reported saying that “so far” the shells appeared to be from white settlers who removed oyster meat and left shell piles behind, and not from native tribes. However, the investigation was continuing and it was not clear how long the construction stoppage would last.
The Seattle Times said a signed agreement allows tribes to monitor state handling of unexpected artifacts, and that project staff notified at least six tribes, the state Department of Archaeology and Historic Preservation, and the Federal Highway Administration about the shell deposit.
WSDOT said its archaeologists were working with the other groups “to develop an investigative plan to determine whether the shell deposit observed in the access pit last week is of cultural significance.”
Meanwhile, the find has delayed by at least several more days an effort to rescue “Bertha,” the giant tunnel boring machine that overheated last December in an early phase of digging a $2 billion tunnel.
That is part of a $3.1 billion project to replace the 1950s-era viaduct that was damaged by a 2001 earthquake. The new highway was supposed to open in 2016, but the newspaper said the timeline is now about a year behind the contractor’s planned schedule.
The rescue plan was to dig a shaft down 120 feet to the head of the machine, so workers could remove the front end, lift it to the surface and make repairs. (A YouTube video by Seattle Tunnel Partners includes animation to show how that would be done. It runs about seven minutes.)
