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The lengthy task of fixing tunnel machine Bertha will delay the Highway 99 tunnel project an additional nine months, so it won’t open to traffic until August 2017, a tentative schedule says.

Seattle Tunnel Partners (STP) gave that estimate in a chart the Washington State Department of Transportation (WSDOT) released Monday. The state cautioned that any timelines are strictly tentative, until the giant drill is running again.

Chris Dixon, STP project manager, insisted his group will finish the job, even if the team misses by 20 months its original goal to finish a year from now, and misses its second goal, to finish in November 2016.

“The state fully intends to stay the course and complete this job,” added Matt Preedy, the state’s deputy Highway 99 administrator.

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But there was also some good news Monday: The soil settlement in the historic Pioneer Square area is probably less than the 1.4 inches the WSDOT described last week, while no structural damage was found in examinations of 50 buildings.

A few showed “cosmetic damage,” such as doors and windows sticking, an official update said.

As of Monday, crews along the waterfront have excavated 90 feet of the 120-foot- deep-access vault, where a mammoth red crane will be used to lift and repair the front end of Bertha at the surface. The boring machine overheated and stalled just over a year ago, when grit penetrated the seals around the main bearing.

Dixon disclosed a new issue with the vault, in a teleconference Monday with news reporters.

A few of the vertical pilings, designed like a wall to contain concrete grout, have shifted out of plumb, making it difficult to inject “interstitial grout” to fill gaps between those and other pilings, to form a tight seal.

STP needs to create a snug fit so that the ring-shaped vault will reinforce itself against massive compression from groundwater and soil. That’s also a safety measure, as the 80-foot-wide vault contains no internal bracing.

Dixon said contractors will need a couple of weeks to remove the tilted pilings and add grout, so pit excavation resumes in January.

Traveler headaches

Each month of delay means that bus riders and drivers who enter downtown Seattle on Aurora Avenue North will keep suffering through the construction bottleneck over Mercer Street. The state and city say they can provide only two general lanes in each direction, because of the road geometry around the new tunnel portal, until the project is nearly finished.

Even in light of the August 2017 timeline, Preedy said there aren’t any engineering strategies being devised that could restore Aurora sooner to its full capacity, of two general lanes plus a bus lane each way.

Bertha’s predicament also aggravates the shortfall in state aid for transit to help people commute on the old Alaskan Way Viaduct past construction zones.

As of midyear, the WSDOT said it has authorized $32 million to date, mainly to help King County Metro Transit add 150 daily West Seattle, White Center and North End buses. Lawmakers have allowed WSDOT Secretary Lynn Peterson to supply transit funds through 2015 — but that now leaves some 20 months unfunded.

“Anything beyond that would have to be appropriated,” by the Legislature, said her spokesman, Lars Erickson.

Further spending might provoke bitter debate in Olympia, where lawmakers in 2009 passed a legally toothless but emotionally potent clause to make Seattle cover tunnel cost overruns.

The Seattle Department of Transportation is already planning to relieve crowding on the fast-growing Metro C Line bus in West Seattle with some of a new $60 car-tab fee city voters passed in November. Tapping even more city money to supplant lost state aid would be controversial.

Fear of dating

Just the Bertha repair job qualifies as a world-class construction project.

The giant red crane, a few feet from the old viaduct, will hoist the 2,000-ton front end of the machine, so its cutter head, bearing and other parts can be spread on the surface for repairs.

Workers will replace the bearing, add steel to stiffen the machine and open wider holes on the round cutterhead, so dirt will pour in rather than clog the original, smaller holes.

Even the spokelike mixing arms, which stir the muck just before it enters a conveyor system, will be lengthened.

The state emphasized Monday that any dates by the contractors are strictly tentative, considering that repairs haven’t started yet.

STP’s Dixon seemed to agree. After the machine restarts, it will stop again after two months and 500 feet, for final tests and adjustments, just before plunging beneath the viaduct. That’s a sensitive location because the elevated highway needed reinforcing, and the tunnel drill will then go under the old Western Building and the original Federal Building, not far from weak Pioneer Square soil.

“Another 500 feet, we’ll be post the TBM [tunnel boring machine] repairs and we will have a very good idea what the remaining schedule is for the completion of mining,” Dixon said. At that time, contractors can look for ways to install road decks faster, or save time on other late-stage work, he said.

Schedules are suspect enough that last week, Peterson didn’t even tell the City Council about an August 2017 scenario, even after contractors listed it in a Sept. 30 schedule update, which has since been posted on the tunnel website.

If contractors meet it, the new date would mark four years after Bertha began digging at Sodo, and five years after then-Gov. Chris Gregoire vowed to remove the quake-damaged viaduct. Half the structure was demolished in 2011.

Mike Lindblom: 206-515-5631 or mlindblom@seattletimes.com. On Twitter @mikelindblom