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Originally published December 14, 2014 at 6:08 AM | Page modified December 15, 2014 at 12:31 PM

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Guest: WSDOT explains the settling, liability and safety of the Highway 99 tunnel project

It’s up to the state and Seattle to ensure public safety along the tunnel route, and it is up to the contractor to fix Bertha and get the tunnel done.

Special to The Times


WE knew digging the world’s largest bored tunnel beneath Seattle wouldn’t be easy. That’s why the state Legislature chose a different approach in 2009 when it passed legislation that required the Washington State Department of Transportation to incentivize the contractor to encourage on-time delivery of the project while minimizing the potential for cost overrun. To accomplish this, WSDOT entered into a contract, which gave responsibility to the contractor to design and build the tunnel, including the tunneling machine. That placed the majority of the risk on the contractor.

It is incumbent on the state and the city to ensure public safety along the tunnel route, and it is up to the contractor to fix Bertha and get the tunnel done.

With the recent earth settlement near the repair site for Bertha, people are asking questions that are both timely and valid, including those in a Dec. 9 Seattle Times editorial.

At what point does the viaduct become unusable?

Our bridge experts have confirmed that the viaduct remains safe for day-to-day use. If we had any reason to believe it isn’t, we wouldn’t hesitate to close it. This does not change the fact that the viaduct remains vulnerable to earthquakes. That’s why it’s being replaced.

All structures are designed to withstand some settlement and we expected some on this project. It’s challenging to explain in general terms how any ground movement is acceptable. In the case of the viaduct, no one number represents an acceptable level — limits vary along the length of the viaduct based on ground conditions and the condition of the structure. How the ground settles is also important. A structure that settles uniformly is less likely to be damaged than a structure that settles unevenly.

If necessary, techniques could be used to strengthen the viaduct and keep it open to traffic until the new Highway 99 corridor is completed, including strengthening columns to provide additional support and reinforcing the viaduct’s foundation.

How viable now is the plan to get Bertha restarted?

We’re disappointed with Seattle Tunnel Partners’ progress to date, and we can’t guarantee it will meet its schedule milestones. A preliminary review showed its plan to restart Bertha would likely work. But an expert technical team is awaiting more information from the contractor once the machine is brought to the surface to provide us with feedback on STP’s plan.

The nature of our contract places the risk to resume mining squarely on STP. That’s why we denied the change order they submitted related to the tunneling stoppage, and why we believe that problems related to their repair efforts are not the responsibility of Washingtonians.

What are the other options if the 120-foot pit cannot be dug without destabilizing the viaduct?

There are other ways for STP to access the machine, both through the pit and through the tunnel. At its core, this is an engineering problem, one that can no doubt be solved. The current plan was simply chosen by STP for reasons of cost and expediency. If it changes course, deciding the best path forward — and assuming the risk associated with that choice — will be up to STP.

What is the state’s financial exposure in this tunnel contract?

The answer to this question goes back to the way this contract is structured. A design-build contract gives the contractor greater opportunities for reward if things go well, but it also requires the contractor to take on a greater share of the risk. As a result, the contract is perhaps the most important tool we have on this project: protecting taxpayers.

I would be remiss if I didn’t address the main issue raised by The Seattle Times editorial — that we’ve struggled to communicate with our partners. It’s been nearly five years since plans to replace the viaduct with a bored tunnel were announced. The focus then, as now, was on coordination. All of us are in this together — state, county, city and the Port of Seattle. We have to be. That’s the only way to make this vision, so long in the making, a reality.

Not including the countless meetings and both formal and informal communications with city officials and their staff, in the year since tunneling stopped we’ve sent 41 project updates to them as well as to state and local elected officials.

Even when challenges or misunderstandings arise, the truth is that we all want the same thing: safety for the public, protection for taxpayers and daylight for Bertha.

Lynn Peterson is secretary of the Washington State Department of Transportation.

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