City Consultants Agree That the Viaduct Is Safe. What Does That Even Mean?

A vision of what might happen to the viaduct in the event of a strong earthquake. Hawk Krall

The whole point of building a deep-bore tunnel beneath Seattle is to help this city deal with scary fact that our 60-year-old, two-tiered highway along the waterfront is deteriorating—worrisomely. Back in 2008, former governor Christine Gregoire insisted that the sinking Alaskan Way Viaduct come down by 2012, no matter what.

Fast-forward to April of 2015, when state and now city officials are telling the Seattle City Council that the viaduct is actually safe.

Earlier today, the Seattle Department of Transportation released a report from CH2M HILL, a group of consultants the agency had hired to assess the viaduct’s structural soundness. After poring over 30 analyses, the consultants ended up generally agreeing with the state: The viaduct is safe.

Understandably, some council members were confused by what that meant for the future.

In this morning’s briefing with the Washington State Department of Transportation, Bruce Harrell asked whether WSDOT had determined any kind of “trigger” points in survey data that might suggest when the viaduct really, really won’t be safe anymore. WSDOT’s Todd Trepanier replied that no such triggers exist, and that there’s a whole host of monitoring and repair actions that the agency assesses and conducts instead.

Tom Rasmussen piped up and suggested that the viaduct “is so complex that there is no one thing that could happen that could say it has to be closed, other than, perhaps, an earthquake.”

“Well-stated,” Trepanier said.

(In other words, as Kathleen Richards noted a while back: “It’s ‘safe’—until it isn’t.”)

But Trepanier’s response didn’t quite cut it for other council members. Mike O’Brien tried asking from a different angle: Okay, even if there’s a “matrix of triggers” that inform viaduct safety, when would WSDOT be able to make a decision about when the viaduct is unsafe?

“It is more complex than anything that can be put into a decision matrix,” Trepanier said.

Upon further pressing, Trepanier said that the safety assessment had to do with demand-to-capacity calculations (which no one appears to have truly understood). Trepanier also referenced the progress in information-sharing between city and state accomplished by the CH2M HILL report. Yet, while the report did support much of WSDOT and its contractor’s work, it also flagged STP’s structural evaluation of the viaduct and suggested that more analyses be completed before tunneling resumes.

For example:

While the basic assumptions and the overall analysis approach appear to be reasonable, the review has raised questions regarding the structural modeling methods used in STP’s calculations. Most significantly, the method used by STP to account for inelastic action of the structural members and the procedure for applying anticipated structural settlements has been questioned. CH2M HILL has informed SDOT and WSDOT of these issues and is currently in contact with WSDOT and STP in the process of resolving them. Although the impact of these potential discrepancies is not yet clear, successful resolution of these issues will be critical to the validation of STP’s viaduct strengthening design.

When asked what that meant in English, SDOT spokesperson Marybeth Turner wrote in an e-mail that this section of the report is very much “in the weeds.”

Here’s more:

The City’s consultant, CH2MHill, is continuing to work with WSDOT and their contractor to fully understand the modeling that was done. Again, this does not cause immediate concerns about the structural capacity of the viaduct today, but we are recommending that additional work be done before tunneling resumes to determine whether additional strengthening is advisable.

Urban planner Cary Moon said that the report’s recommendations for studying risk areas were good ones. “But more importantly, the city and state should establish an independent core team to watch the new data like a hawk and focus only on the question of viaduct safety,” she wrote in an e-mail. “Regardless of what is happening with the tunnel progress, regardless of the political hit of having to admit failure, regardless of the cost liability question, regardless of the difficulty in assembling the funding for the transit and street improvements needed to get by without the viaduct.”

Here’s what else we learned from today’s WSDOT briefing:

• The city and the state are getting together at the end of the month to figure out who’s paying for what regarding the surface street along the waterfront.

• Matt Preedy, deputy program administrator for the viaduct replacement program, is leaving WSDOT for a construction management position at Sound Transit. He’s worked on the Alaskan Way Viaduct Replacement Program for eight years, and has been part of WSDOT for 23. (The Stranger’s two cents: We liked Preedy and thought he was helpful. Sucks for WSDOT.) He also dedicated his last Seattle City Council briefing to public transparency. “It kind of came home to me on that day when we brought the tunnel boring machine to the surface,” he said. Communicating with media was important, but the people he wanted to talk to most were regular bystanders on Jackson Street. “We work for WSDOT, but I live in this city, too,” he said, then thanked the city council for asking hard questions.