(Corrects paragraph 4 to read $2 billion is the cost of the
tunnel portion of the project rather than the total cost of the
project, in paragraph 9 corrects weight of machine to 8,000-ton
By Tom James
SEATTLE, April 5 Bertha, one of the world’s
largest boring machines, will cut through a thick concrete wall
at midday on Tuesday if all goes according to plan, completing
the most difficult phase of building a highway under the heart
of downtown Seattle.
Reaching open air through 5 feet (1.5 m) of concrete is a
major step in one of the most ambitious American municipal
projects in recent years. Once complete, 2 miles (3 km) of
Highway 99, an elevated roadway along a densely populated
waterfront, will be rerouted to run beneath the city of 650,000
A sinkhole, a two-year delay and a $480 million claim by
contractors have challenged the $3.1 billion project since it
began in June 2013.
The underground highway, the tunnel portion of which was
budgeted at $2 billion, was initially expected to be completed
by the end of 2015 and has been widely compared with Boston's
16-year "Big Dig" tunneling project, which suffered through cost
overruns, design flaws, worker fatalities and other problems.
“It’s like shoving a five-story building through the ground
under downtown Seattle,” project director Chris Dixon said at a
Monday news conference.
Seattle’s tunnel will be among the world's largest, about
seven times the size of one in a typical subway, Dixon said.
After emerging into a large open-air pit a few blocks from
Seattle’s Queen Anne neighborhood, Bertha will be cut into
pieces and hauled away over several months.
The 57-foot (17 m) wide borer made by Japan's Hitachi Zosen
Corp cost $80 million and was the largest in the world
when tunneling started in 2013.
As engineers make plans to break down the 8,000-ton
(7,260-metric ton) machine, work to fill the tunnel with a
double-decker roadway has already begun. State planners hope to
have the first car travel through the tunnel in early 2019.
While the project’s $3.1 billion price tag is comparatively
small - the Big Dig's is estimated at $22 billion - progress was
complicated by plans to dig beneath some of the most tightly
packed neighborhoods in downtown Seattle.
Bertha overheated and stalled partway through the project in
December 2013, putting completion into doubt. Tunneling was
delayed two years as engineers dug a 120-foot (37 m) access pit
to make repairs.
(Editing by Lisa Von Ahn)