Viaduct, City Council share that sinking feeling

Some on the Seattle City Council feel WSDOT left them in the dark about tunnel-related settling of the Alaskan Way Viaduct.
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Bertha's stalled, the Viaduct's sinking and Mike O'Brien's hopping mad.

Some on the Seattle City Council feel WSDOT left them in the dark about tunnel-related settling of the Alaskan Way Viaduct.

On Friday, The Seattle Times reported that the Alaskan Way Viaduct had sunk 1.2 inches as the construction team responsible for the Highway 99 tunnel project "struggled to prevent risky soil settlement." The story about the viaduct sinking came as a complete shock to Seattle City Council members who, despite receiving a PowerPoint presentation regarding the tunnel from the Washington State department of Transportation (WSDOT) only days before, had not been informed that Highway 99 and Pioneer Square buildings had shifted. On Monday afternoon, WSDOT was back before the City Council to explain. 

The Times’ story came out a day before the one-year anniversary of Bertha’s stoppage. The $2 billion tunnel project has been plagued by an ongoing string of problems: broken seals behind the cutterhead, an overheated main bearing, fears (ultimately groundless) about endangering potentially significant archeological deposits and now this sinking. Tunneling was supposed to be wrapping up about now. Instead, Bertha has carved out just over 1,000 feet (or 10 percent) of the waterfront tunnel. The project is already more than a year behind schedule, and Bertha is still stalled, and awaiting repair.

Any evidence of a sinking viaduct would be cause for concern, but initial reports in The Seattle Times suggested that the elevated highway had sunken uniformly, which causes little structural stress. Immediately following the Times’ article, the Washington State Department of Transportation (WSDOT) emailed out a "public update" assuring that “some settlement was expected during tunnel construction,” and promising “no new damage to the viaduct.”

But in a second story, published on Monday, Dec. 8, the Times suggested that the viaduct settlement was not even, which would put the highway at risk for the kind of twisting and stress that could result in permanent damage. Despite that report WSDOT, in Monday's special meeting with the City Council, maintained that the highway had in fact settled uniformly, is safe for driving and will not close.

The discrepancy between the two accounts has the City Council confused, mad and worried.

WSDOT apparently registered the sinking of the viaduct in late November. They did not report it because, according to the department’s representatives, they wanted to be sure that they were in fact seeing settlement and not just some malfunction in their monitoring systems. “We saw the anomaly just before Thanksgiving,” said viaduct replacement project manager Todd Trepanier, “but it was not confirmed [as settlement] until Thursday [Dec. 4th].”

Councilmember Mike O’Brien, a strong tunnel opponent from the outset, did not accept this explanation from WSDOT. “We made it abundantly clear that transparency is going to be critical for us, for me, for the public," said O'Brien. "When they saw that they were settling ... at the bare minimum they should have said ‘we want to give you a heads up, we see some data.’ If they want to analyze the data more, fine. But let us know, as opposed to us reading about it in The Seattle Times.”

O'Brien's frustration was amplified by the fact that WSDOT had given a presentation to the council only days before the first Times story ran. During the presentation, WSDOT representatives spoke only of the excavation, never mentioning any potential settlement concerns. “I don’t know what’s going through their mind that they would give a presentation and not even talk about the settling,” said a clearly upset O’Brien.

WSDOT representatives apologized — but only for not sending the project update prior to the release of the first Times article. Their explanation? A malfunction stopped their e-mail notification from going out. WSDOT reps did not apologize for withholding information from City Councilmembers in late November when they first became aware of a potential settling issue, or during their presentation.

According to O’Brien, poor communication between the Council and WSDOT is nothing new. In March O'Brien, fellow councilmembers Tom Rasmussen and Jean Godden and Seattle Mayor Ed Murray sent a letter to WSDOT asking for information regarding safety thresholds and contingency plans for the tunnel project. WSDOT's response, according to O'Brien, was unsatisfying. “I don’t feel confident that I’m getting the information that I need,” he said.

When asked how worried he was about the viaduct, O'Brien replied: “I don’t know how worried I should be. But do I know that someone’s looking out for this? My confidence has been shaken.”

WSDOT's appearance before the Council on Monday was, mostly, a display of the frustrating divide between the politicians and structural engineers. Councilmembers Sally Clark, Sally Bagshaw, Tom Rasmussen, Kshama Sawant and O’Brien hammered the WSDOT representatives for some kind of benchmark that will determine if and when the city should shut down the viaduct. The answer from WSDOT was, largely, “It’s complicated.”

The viaduct has already been labeled unsafe. Indeed, the whole tunnel project was propelled by its un-safety. After the 2001 Nisqually quake, the viaduct sunk about five inches and cracked in many places. At the time, the threshold for total closure of the roadway was set at six inches. The most recent settling puts portions of the highway below that six-inch threshold.

Councilmember Godden wondered why that finding doesn't force an immediate closure of the viaduct. Tom Moore, a WSDOT structural engineer who has worked on the viaduct, explained that different parts of the highway were reinforced in different ways. So while the threshold for closure may well be six inches for some sections, it may be a larger or smaller number for other sections. And there are other factors, including the speed with which the viaduct settled. The faster it settled, the more damage it absorbs. If it’s any comfort, Moore said, he walks under the viaduct every day.

The solutions ahead are, as expected, complicated. The main cause of the current sinking is the groundwater being pumped out of the Bertha's excavation pit. As workers dig the pit, surrounding water puts pressure on the shaft. If workers don't remove some of the water, the pit could be crushed. So while removing water is likely causing the soil to settle, not removing it may lead to dangerous conditions for workers in the pit.

For now, WSDOT is monitoring the viaduct and the Pioneer Square neighborood on a daily basis. If the settling stops, the pit excavation can continue; if not, WSDOT engineers will need to figure out how to shut off the groundwater pump.

Considering his lack of faith in WSDOT, Mike O’Brien did not rule out shutting down the highway regardless of WSDOT's assurances. O'Brien also recognized the potential danger to the Pioneer Square neighborhood as a whole, and seemed willing to consider additional precautions to protect the area if necessary.

Former Governor Christine Gregoire said the viaduct would be down by 2012. The whole tunnel boring project was scheduled for completion by December 2015. None of that has happened. WSDOT's Moore calls the viaduct safe for now, but "is not built to last for another 75 years."

Considering Mike O’Brien's skepticism about the tunnel ever being completed, all of a sudden, 75 years doesn’t look so far off.


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About the Authors & Contributors

David Kroman

David Kroman

David Kroman is formerly a reporter at Crosscut, where he covered city politics.