Board rules WSDOT should have given contractor more warning about pipe struck by Big Bertha before stall

Updated May 26, 2015

Big Bertha in repair pit WSDOT

In regard to the drilling of the new State Route 99 tunnel below Seattle, the Washington State Department of Transportation (WSDOT) has few friends left.

There remains disagreement between the department and the city of Seattle over who will pay to repair a water main damaged during the excavation of a repair pit for Big Bertha, the world’s largest tunnel boring machine, which stalled out while digging the tunnel after overheating in December 2013.

RELATED >> PHOTOS: Big Bertha’s 2,000-ton front end lifted to the surface. How the world’s largest tunneler was raised

And now, a dispute review board has ruled in favor of Seattle Tunnel Partners (STP), agreeing WSDOT should have given the contractor more warning about a large steel pipe hit by Big Bertha three days before it stalled, according to a report from the Seattle Times.

According to the report, “(STP) project director Chris Dixon said steel pieces damaged the bits on the rotary cutting face, leading Bertha to need more thrust than usual, sustain more friction and eventually overheat.”

Since January 2014, STP has contended that the pipe is the root cause to the machine’s overheating, putting it nearly two years behind schedule.

The steel pipe is 8 inches in diameter and 115 feet long. It was installed by the WSDOT in 2002 to measure groundwater during studies for the very Alaskan Way Viaduct replacement project Bertha was carrying out. The massive machine went down only one-tenth of the way through digging the 1.7-mile tunnel which will carry a double-deck highway.

While the pipe was mentioned in reference documents provided to all contractors bidding on the tunnel job, the board ruled that the geotechnical baseline report to describe soil conditions to STP was “silent” regarding the pipe.

The decision however isn’t binding and therefore doesn’t yet require WSDOT to pay the $125 million being sought by STP. The Times reports the WSDOT disagrees with the board decision and notes that “negotiations and lawsuits” over the discrepancy are likely.

In fact, WSDOT argues Bertha’s extensive downtime has more to do with shoddy craftsmanship by Japanese manufacturer Hitachi-Zosen than the pipe.

Water and sand clogging Bertha’s cutterhead openings brought the machine to a halt in January 2014, penetrating seven rubber seals meant to protect the main bearing.

In repairing the machine, crews will install 216 steel ribs and plates that will add 86 tons of reinforcement to the 7,000-ton machine’s drive block and cutter drive. Those repairs began March 31 when crews lifted Bertha’s cutterhead and body shield panels to the surface through a 12-story pit.

Crews hope to resume drilling in August.