This is what Berthas 1,000-cubic-yard concrete cradle looks like. Cozy!
  • Washington State Department of Transportation
  • This is what Bertha's 1,000-cubic-yard concrete cradle looks like. Cozy!

Bertha's rescue pit may be finished, but Seattle Tunnel Partners still has a ways to go before they can extricate the broken bits and (maybe!) get the tunnel boring machine to work again. On Monday, state and city officials discussed how Bertha is supposed to chew her way out of the rescue pit, but after they did this interesting explaining something else tumbled out: plans for what will happen if the viaduct becomes too dangerous to stay open for business.

To recap Bertha's chewing plans: Todd Trepanier of the Washington State Department of Transportation told the council that 1,000 cubic yards of concrete had been poured into the bottom of the pit. That concrete will serve as a kind of cradle for the 2,000-ton parts of the machine that need to be pulled out over lubricated rails. Before that can happen, the broken tunneling machine is supposed to bore her way through 20 feet of concrete. If she can't, the contractor will go in from the other side with a giant jackhammer.

All of this, again, is happening 20 feet from the nearest viaduct bent. Seattle City Council Member Mike O'Brien asked Trepanier whether Bertha's rescue operation might compromise viaduct safety, but Trepanier said that the contractor's engineer of record did not anticipate any problems.

In the event that something does go awry, Seattle Department of Transportation director Scott Kubly presented plans for short- and long-term viaduct weight restriction and closure plans following WSDOT's presentation.

The city already has near-term plans in place to reroute traffic if the viaduct has to be closed or weight-restricted for up to one week. Kubly noted that the viaduct serves some 12 bus routes and 24,000 riders a day, and in the event of closure, those riders would likely be directed to new routes on First or Fourth Avenue. To transfer cars, Kubly said that SDOT's looking into how many buses the city would need and how to better manage the existing signal system.

"In the longer term, that’s when we really start looking at adding additional transit service," Kubly said.

The state already allocated money for downtown transit improvements while the tunnel was being constructed, but that's been spent.

"In order for planning for contingencies we need to think about how all our partners are dealing with a longer term closure—are there major capital projects that we would need to help mitigate the impact?" Kubly asked. "That would absolutely have a state package impact." (Meaning, it would likely require asking reticent Republicans in the sate legislature for money.)

Kubly said that he's hoping to have a plan on longer-term closures in place before the city issues a preliminary report on the viaduct in March.

The city might also have to replace a damaged 100-year-old water main that's settled along Western Avenue. Seattle would likely seek funding from the state for that project, and repairs could take a year.