Soil Settling Halts Seattle’s Highway 99 Project

December 11, 2014

Operations have stopped at downtown Seattle’s state Route 99 tunnel project as the soil beneath the Alaskan Way Viaduct is settling unevenly, according to Roads & Bridges magazine.

Crews have been excavating a pit to attempt to repair Bertha, the tunnel boring machine digging the tunnel. The machine is currently stuck underground. The uneven soil settling is attributed to the groundwater pumping occurring as Seattle Tunnel Partners digs an access pit to reach the machine.

According to Seattle Pi, Bertha dug 10 percent of the two-mile tunnel before it stopped a year ago.

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Source: Roads & Bridges