Tunnel-project crew digs down in hopes of reaching pipe

The Seattle TimesJanuary 9, 2014 

Construction on the Highway 99 tunnel in Seattle is shown in this 2013 photo from the state Department of Transportation.

GREG PHIPPS — WSDOT

Crews on the Highway 99 tunnel project spent Wednesday drilling a second vertical shaft, in hopes of breaking and removing the steel pipe that has blocked tunnel-boring machine Bertha for a month.

The first 5-foot-diameter shaft was finished Tuesday, without hitting steel, said Laura Newborn, spokeswoman for the state Department of Transportation (DOT).

Because the machine is descending, any objects near the bottom of the 57-foot-diameter cutting face will be difficult to reach through straight vertical drilling, she pointed out. The top of the rotary cutter, at 60 feet below street level, is farther forward than the bottom half.

Bertha is buried near the central waterfront, approaching South Main Street. Later this year it’s supposed to dive under the old Alaskan Way Viaduct, on the way to South Lake Union.

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