Bertha hits new milestone in its journey under Seattle

Last week, Bertha hit the 60 percent completion mark, however, there is another statistic tunnel crews are noting.

The boring machine is now around the deepest point in its journey under Seattle. The top of the cutterhead is around 210 feet below the surface. That makes the bottom of the tunnel more than 265 feet down, according to WSDOT’s last check in.

WSDOT noted last week that tunnel crews are working roughly as deep underground as the towering condominium building above them on the surface.

Bertha breaks into zone 7 under Seattle

Bertha may not have been digging any deeper recently, however. As the boring machine moved forward over the past few months, it has moved relatively straight. The surface level above the machine, on the other hand, has risen much higher. Bertha will have to move upward soon, though, if it wants to meet up at its end goal near Denny Street.

Bertha is currently in zone 7, out of 10 zones. So far, the machine has moved forward 5,774 feet — out of the total 9,270 foot journey. That equates to 880 concrete tunnel rings. There will be a total of 1,426 rings constructed once the tunnel is completed.

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