Congratulations, Bertha; the tunnel continues - well, at least it will after they've finished changing its oil and such.
Bertha is making a big round tunnel. Round is good for tunnels, but not so good for roads. We like our roads flat. The tunnel is also going to have lanes going in opposite directions, just like any good highway. Instead of putting the lanes beside each other, one set will sit over the other set. Turning a round tunnel into a two story highway with flat floors takes a lot of work; and that work continues while Bertha gets a bit of pampering.
WSDOT produced a video that shows how much work is involved. As if pouring concrete a thousand feet up the tunnel a hundred feet below Seattle's downtown wasn't hard enough, there are ventilation systems to put in place, lights to install, all the basics of road construction - all while equipment, people, and materials have to shuttle up and back from Bertha. One datum that captures the size of the task: enough concrete will be poured in the tunnel to build nine stadiums. Imagine dig a hole big enough to build nine stadiums under Seattle's basements while leaving room for four lanes of traffic. Impressive.
· Bertha takes maintenance break after 3,088 feet [CS]
· Building a highway inside a tunnel [WSDOT]