ROADS/BRIDGES: Wash. Gov. orders a stop on all Bertha work due to massive sinkhole

Jan. 15, 2016

Work on Highway 99 in Seattle stopped when a sinkhole near the underground Bertha cutterhead was discovered

Washington Gov. Jay Inslee ordered Seattle Tunnel Partners (STP) to halt all tunneling activity at the $3.1 billion Alaskan Way Viaduct replacement project in Seattle after a 35-ft-long sinkhole appeared earlier this week.

The order to stop all tunneling work reflects a shift from the state’s hands-of-approach to the megaproject, which originally placed all construction in the hands of the STP. The state now has the right to intervene under a new contract-clause that allows it to suspend all work on a “failure to correct conditions unsafe for Project personnel ore the general public.”

Contractors filled the hole, which measured 35 ft long, 20 ft wide and 15 ft deep, with 250 cu yd of concrete-sand mix. However, the ground above the tunnel-boring machine Bertha is continuing to sink, according to the Washington State Department of Transportation (WSDOT).

The problem is limited to the area immediately around the machine, and has not spread to the nearby Alaskan Way Viaduct, said WSDOT spokeswoman Laura Newborn.

Tunnel-borer Bertha had only recently resumed activity. The governor wants STP to determine exactly how the sinkhole was created and assure the state that there will be no new sinkholes in the future. STP has implemented precautions, including manually checking soil quality.

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