Our Sponsors:

Read more »

Our Members

Many thanks to Rebecca Bogard and Mary Shane some of our many supporters.

ALL MEMBERS »

Baby Bertha? Another tunnel-boring machine will soon start digging Seattle

"Brenda" is scheduled to begin digging a 3.4-mile stretch of Sound Transit light rail tunnel from Northgate to the University District in June.

Seattle will no longer be a one tunnel-boring machine town. While Bertha, the massive rig digging the Highway 99 tunnel sat idle under downtown in recent months awaiting repairs, a Sound Transit contractor has been quietly assembling a similar but smaller machine, which will soon begin tunneling at the north end of the city.

Unlike the oh-so-much-better-known Bertha, the machine on the Sound Transit job comes with a proven track record, having successfully completed other digs for the agency in recent years. The new Sound Transit project, known as the Northgate Link Extension, involves digging twin, 3.4-mile light rail tunnels beginning near NE 94th Street and First Avenue NE, and ending at University of Washington’s Husky Stadium. “Brenda,” the first machine set to launch, is scheduled to start mining in June. Another machine, known for now as TBM 2, is slated to begin digging the second of the twin tunnels sometime around October.

Workers are putting the final touches on Brenda, a 21-foot diameter boring machine. Photo: Bill Lucia. 

When the Northgate extension is completed, Sound Transit's Link light rail service will run all the way from NE 103rd Street to just beyond Seattle-Tacoma International Airport to S. 200th Street in SeaTac. The light rail currently runs from the airport to Westlake Station in downtown Seattle. The total budget for the Northgate extension is $2.1 billion. Including the aboveground portions, the new stretch of light rail track will run 4.3 miles. Sound Transit is planning to have tunneling completed by 2016 and the extended rail service operating by 2021.

Getting the project done will rely partly on Brenda. With a 21-foot diameter cutter-head, the machine looks like a pint-sized replica of Bertha. At 57.5-feet wide, Bertha is the world’s largest tunneling rig. But a damaged main bearing assembly has left the machine hamstrung after about 1,000 feet of digging. Bertha has barely moved since early December and will be partially unearthed to undergo repairs.

Hitachi Zosen Corp. manufactured Brenda and Bertha in Osaka, Japan and both machines use similar technology to chew through the earth.

Assembling Brenda has taken about three and a half months so far, according to Sound Transit's executive project director for the Northgate Link Extension, Don Davis. It should be completely put together in about one week, a spokesman for the agency, Bruce Gray, said Friday. After that it will be tested. The machine is currently parked across from a shopping plaza in Maple Leaf, just south of NE 100th Street, next to Interstate 5. A few blocks further south, near NE 94th Street, is a roughly 70-foot concrete headwall where Brenda will begin tunneling. 

On Friday, hard-hatted workers came and went from the rear of Brenda’s can-shaped forward shell. The sun shone on the freshly painted green-and-yellow cutter-head. Valve fittings were laid out on a shop rag, a worker cut a piece of metal with a torch, hoses hung down from the system that will be used to inject soil-conditioning grout in front of the machine as it mines forward. Extending rearward was Brenda's "trailing gear," which houses the operator cabin, parts of the electrical and soil conveyor systems and other support equipment. With the trailing gear, the machine is about 300-feet long.

The Northgate project will actually be Brenda's third trip underneath Seattle. In 2011 and 2012, the machine dug a pair of Link light rail tunnels from Broadway and East Denny Way in Capitol Hill to a location near Pine Street and Interstate 5 in downtown.

Each of the two tunnels was a segment of Sound Transit's University Link Extension, which will eventually connect the existing light rail service that ends at Westlake Station with the University District. The two tunnels Brenda mined were both about three-quarters of a mile in length. The first was completed in 134 days, according to Gray. After the machine finished the first drive it was trucked in pieces back to Capitol Hill and re-launched. The second tunnel took 96 days to dig. Jay Dee Contractors, Frank Coluccio Construction and Michels Corp., or JCM, the contracting consortium that constructed those tunnel segments, was also awarded the Northgate contract.


Like what you just read? Support high quality local journalism. Become a member of Crosscut today!

Comments:

Posted Sun, Apr 27, 9:41 p.m. Inappropriate

Mr. Lucia.

Maybe I am not tracking, but why did STP choose a 50' diameter boring machine in the first place? rather than two parallel tubes? and using smaller machines like the 21' diameter one you are discussing? (The numbers don't make complete sense so I must be misunderstanding some aspect.)

And as a solution to the current problem with Bertha, why not stop and use two parallel tubes?

Posted Sun, Apr 27, 9:55 p.m. Inappropriate

Are you kidding? That would require admitting that "mistakes were made."

louploup

Posted Mon, Apr 28, 8:46 a.m. Inappropriate

In order to fit three lanes into one tunnel (2 traffic lanes and one emergency lane with 14' clearance) you would need diameter somewhere near 40' (Draw yourself a circle and try this graphically.)

A 40' diameter tunnels has a cross section of about 1200 square feet. Two of them: about 2400 sf. A single 50' tunnel has a cross section of about 2000 sf.

So, two smaller bore tunnels would require more dirt removal and other costs than one. Secondly, 21' doesn't even come close to supporting three lanes and it would be questionable how much easier it would be to run a 40' machine rather than a 50' machine.

pragmatic

Posted Mon, Apr 28, 7:23 a.m. Inappropriate

From the story:

The University Link project, according to Gray, is between six and nine months ahead of schedule and roughly $108 million under budget.

Some context would be helpful here. That is only the most recent schedule, and only the most recent budget. Sound Transit's unaccountable board routinely extends schedules and increases budgets.

Sound Transit's plans for light rail from the airport up to the University District were hatched in the mid-1990's. The estimated budget the public approved in 1996 for the light rail tunnel that was going to run 4.5 miles from the convention center to 45th Avenue in the University district was $557 million. Sound Transit assured the public it would be operational in 2006.

Now the budget for just the 3.2 mile tunnel from downtown to Husky stadium is $1.9 billion. There is a separate, additional new budget for the tunneling north of there to Northgate: another $2.1 billion.

Here's the November, 2000 story in the Times about the first set of schedule delays and budget hikes by Sound Transit:

http://community.seattletimes.nwsource.com/archive/?date=20001118&slug;=4053733

-------------------------

November 18, 2000

Light rail ETA: one year late
By Brier Dudley
Seattle Times staff reporter

Light-rail service in Seattle will be delayed at least a year because of Sound Transit's problems securing an affordable tunneling contract.

Rail service from SeaTac to the University District was supposed to begin in November 2006. Now, it won't happen until late 2007 or perhaps even 2008.

"There's going to be a delay. We're talking about months of delay, no question," said Paul Bay, the agency's light-rail director.

When voters were asked to authorize the $3.9 billion system in 1996, they were told it would take 10 years to build a network that would include express buses and commuter trains as well as the light-rail system.

Yesterday, officials said it's worth waiting to be sure the project can be built without large cost overruns.

"I think the public's attitude would probably be, hey, if we have to take a little extra time to do this right, it's still better than not doing it at all," said state Transportation Secretary Sid Morrison, a member of Sound Transit's board.

On Thursday, the board suspended contract negotiations after learning that the lowest bid on its main tunnel was $171 million more than budgeted.

After two months of negotiations, the lowest bid from the chosen contractor, Modern Transit, was $728 million. Sound Transit had estimated the tunnel would cost $557 million.

The 4.5-mile tunnel would extend the downtown transit tunnel beneath First Hill and Capitol Hill and under Portage Bay to the University of Washington.

http://community.seattletimes.nwsource.com/archive/?date=20001118&slug;=4053733

-------------------------

Contrary to what this Crosscut puff piece avers, Sound Transit's megaprojects are not timely or delivered at a reasonable cost to the public.

Anyone want to discuss the regressive tax costs of the abusive financing plan, the one that no other transit system managers in the country utilize?

crossrip

Posted Wed, Apr 30, 10:43 a.m. Inappropriate

Crossrip,

Thanks for your comment.

I asked Sound Transit spokesman Bruce Gray to clarify his statement about the project being ahead of schedule and under budget. He said: "The U-Link project scope and schedule that’s being built today was set in July 2008 and we’re on track to come in under budget and ahead of that schedule."

Best regards,

Posted Wed, Apr 30, 4:52 p.m. Inappropriate

Thanks for your response, Bill.

Bruce Gray certainly is referring to the July, 2008 budget and timetable, and not the earlier figures.

It's worth noting that there have been a series of increasing cost estimates. Some of them are in my posting above. Another is this one, from the state auditor's October 2007 report:

http://www.sao.wa.gov/auditreports/auditreportfiles/ar1000005.pdf

Sound Transit has had “second-opinion” cost estimates performed for high risk and complex construction packages such as . . . the University Link ($1.5 billion). This approach supports best practices and efforts to mitigate cost overruns.

That is from page 51. Less than a year later the board increased the University Link budget to $1.9 billion.

crossrip

Posted Mon, Apr 28, 7:33 a.m. Inappropriate

Building two tubes was much more expensive than building one large tube, or that is what sold us at the time.

Rocky

Posted Mon, Apr 28, 12:26 p.m. Inappropriate

The 3-mile twin-tube Robertson Tunnel for Portland's Westside MAX light rail, with its single ZOO Station, opened in 1998 and cost $190 million. Accounting for inflation, the same tunnel today might cost $500 million. It's curious how things cost more in Seattle. Seattle's notorious "screw-up factor" probably doubles cost predictions.

Interesting article worth followups.
Is the UW to Capital Hill segment included in the 3.4 miles?

Wells

Posted Mon, Apr 28, 1:28 p.m. Inappropriate


Wow. Try a little harder, Wells!

1) Something that cost $190 million in 1998 would cost $275 million now due to inflation, not $500 million. Here's the calculator:

http://data.bls.gov/cgi-bin/cpicalc.pl

2) Is the UW to Capital Hill segment included in the 3.4 miles?

No, it is not. How could you possibly be confused about that?

crossrip

Posted Wed, Apr 30, 11:05 a.m. Inappropriate

The article highlights the completed segment between Capital Hill and Convention Place Station, but says next to nothing about the segment between Capital Hill and Huckster Stadium. Is that segment finished?

Wells

Posted Tue, Apr 29, 6:05 a.m. Inappropriate

What is the over-under on Bertha and Brenda becoming "Double Stuck"?

Cameron

Posted Fri, May 23, 8:51 a.m. Inappropriate

Brenda is 20' diameter.
Bertha diameter 58' near thrice.
Volume of tube 'departure'
from more or less solid settings,
predicts Brenda fine,
Bertha, given last name Wormtunnel.

"Bertha Wormtunnel"
(discussion of 'middle name' ongoing)
Seattle, the nation does NOT trust your engineers.
No way, jose nor your Gilroy Boys.
"Let's run high-speed trains through our own national
park. It's ours, we can do what we want with it"
(overheard in the valley)
Across the Columbia WsDOT NIXED
Marine Dr Interchange replacement.
NIET Wsdot commanded in 2011
after their first bridge design,
rejected as "structurally unsound"
Yet Marine Dr needing replacement most, by far.
Other WsDOT interchanges were cut later.
WsDOT NIXED ODOT Concept#1 Off-island Access 2010
NIET WsDOT commanded.NIET. NIX.
YOU may start worrying any time.

Wells

Login or register to add your voice to the conversation.

Join Crosscut now!
Subscribe to our Newsletter

Follow Us »