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Sinkhole Delays Seattle Tunnel Project

Wednesday, January 20, 2016

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Bertha has stopped digging again, but this time it’s not the machine tunneling under the new State Route 99 in Seattle that’s causing the delays.

Washington Gov. Jay Inslee ordered Bertha—which is digging the underground portion of the Alaskan Way Viaduct Replacement Project—to stop digging after a sinkhole opened up Jan. 12 behind the large drilling machine, the Seattle Post-Intelligencer reported.

The newest delay came after the drilling machine was taken out of service for repairs in 2013 and just had returned to work on Dec. 22. The PI reports that Bertha had dug only about 150 feet when digging stopped again on Jan. 12.

Sinkhole Opens

“I want to remind everyone that replacing the viaduct is critical to public safety,” said state Secretary of Transportation Lynn Peterson in a press conference. “The tunneling work must proceed, but it must proceed safely.”

Photos: WSDOT

Seattle Tunnel Partners said the 35-foot-wide sinkhole would not be “dire” to the Alaskan Way Viaduct Replacement project, which already has been delayed more than two years.

Seattle Tunnel Partners (STP), the design-build firm in charge of digging the nearly 2-mile tunnel, said the 35-foot-wide sinkhole would not be “dire” to the project.

“The sinkhole is an unfortunate event, but isn’t something that is unique or something that wasn’t anticipated,” STP project manager Chris Dixon told the PI.

Dixon went on to say that the walls built in the ground to isolate the tunnel from the viaduct during the shallow portion of the dig protected the viaduct from issues around the tunnel, such as the sinkhole.

However, Dixon also could not provide a cause for the sinkhole. He told the PI that the group would manually check soil samples moving forward.

Gov. Inslee said during the press conference that he expected a full report on the cause of the sinkhole. He also said he would “aggressively” hold STP accountable for public safety issues.

By Tuesday (Jan. 19), WSDOT had not posted any further updates to the project’s website.

Project Background

As reported previously, the replacement project focuses on the 2-mile-long elevated double-deck road originally built in the 1950s. Damage from a 6.8 magnitude earthquake in 2001 led to the need to stabilize and repair the structure and restrict heavy vehicle traffic.

Most of the existing bridge deck has been replaced with new roads, and the viaduct itself will be replaced by the tunnel.

Bertha went out of commission in December 2013, when dirt got into a bearing and caused the machine to overheat, and was returned to service in December 2015.

The 1.7-mile-long tunnel is expected to boast an inside diameter of 52 feet (15.8 meters), allowing it to hold the planned double-deck roadway.

Bertha went out of commission in December 2013, when dirt got into a bearing and caused the machine to overheat. The seal system was damaged after Bertha had dug only 1,000 feet.

STP continued work at the future tunnel portals. The drill was returned to the access pit in August, but work to reconstruct the front shield and reconnect wires, hoses, cables and pipes was not completed until Dec. 23, 2015, a deadline they met.

Lawsuit Filed

Meanwhile, STP and Hitachi Zosen, their insurers, and Washington state are in a legal dispute over who will be responsible for repairing Bertha, according to Reuters.

STP filed a $143 million insurance claim, but the insurance company is fighting that issue in court. In October, the state’s transportation department sued the contractors, Reuters said. The state said it estimated that delays had cost the state about $78 million.

The entire $1.35 billion tunneling project is expected to be complete by April 2018.


Tagged categories: Contractors; Lawsuits; North America; Program/Project Management; Project Management; Roads/Highways; Tunnel

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