Share story

By the time drilling resumes on Seattle’s Highway 99 tunnel, a light-rail dig across town will already be a mile in.

Sound Transit held a dedication ceremony Monday for tunnel-boring machine Brenda, which will depart Northgate to dig a southbound train tube in June.

The drill will pause at the Roosevelt and U District stations, then reach the University of Washington Station next to the Montlake Cut — a two-year journey through soft soil.

Another drill is to embark
in September to create the northbound tube just a few yards away.

This week, save 90% on digital access.

Eventually, the public will ride trains from Northgate to downtown in 14 minutes, bypassing the chronic traffic delays on Interstate 5, said transit-board member Paul Roberts, an Everett city councilman.

Standing before a green-and-gold-painted machine, state Rep. Jessyn Farrell, D-Seattle, mentioned lawmakers’ failure to pass a transportation plan to renovate the freeway next to her.

“The good news is that this equipment, right behind me, is an investment in mobility, in the I-5 corridor,” she said.

Train service on the mostly tunneled $2.1 billion Northgate Link extension is scheduled for September 2021.

Politicians tantalized the voters in 1996 with the possibility of Northgate trains by 2006, but the rail costs have doubled their ballot estimates. Sound Transit reorganized itself and produced realistic schedules.

Its projects are funded mainly through local sales tax, car-tab tax and long-term debt, while the federal government has committed $1.3 billion to date toward building Sound Transit’s $11 billion light-rail network.

The next segment is downtown to the University of Washington Station, in early 2016, then Seattle-Tacoma International Airport south to Angle Lake in late 2016.

Brenda, named for a tunnel supervisor’s wife, has already dug twice from Capitol Hill, beneath I-5, to Convention Place. Its bearing was replaced, and new cutting teeth installed, for reuse by the Jay Dee-Coluccio-Michels (JCM) team.

The cutting face is 21 feet, 1 inch across, or one-seventh the area of the stalled Highway 99 tunnel machine Bertha, at 57 feet, 4 inches across. Both machines were built by Hitachi Zosen in Osaka, Japan.

Bertha has been stalled since December and isn’t expected to resume drilling until next March, after its bearing is replaced.

During years of planning, UW officials worried that tunnel vibrations would disrupt experiments on campus — and as recently as 2011, transit construction sent tremors through Montlake homes.

Contractors will tackle those problems by using a rubber-tired vehicle instead of a supply train to carry the concrete segments from Northgate forward, and by modifying how Brenda’s hydraulic thrusters push it forward.

“We don’t expect there will be any vibrations when they’re tunneling under campus,” said Richard Chapman, UW associate vice chancellor for capital projects.

When the twin drills reach Husky Stadium, trains will already be arriving from the south. A separate chamber already has been built on the station’s north end so that crews can puncture the asphalt parking lot to retrieve the tunnel machines.

JCM used a similar strategy in 2012, when Brenda was hoisted to daylight alongside the Paramount Theatre.

Mike Lindblom: 206-515-5631 or Twitter @mikelindblom

Custom-curated news highlights, delivered weekday mornings.