Seattle Tunnel Partners: Almost the proud owners of the world’s largest tunneling machine

Posted on Dec 5 2013 11:55 AM

It’s been more than two years since our contractor, Seattle Tunnel Partners (STP), inked a deal with Hitachi Zosen Corp. to buy Bertha, the world’s largest tunneling machine.

Since then, the machine has been designed, manufactured, assembled, tested, given a name, disassembled, packed, shipped across the Pacific Ocean, transported to the launch pit, reassembled, tested again, celebrated by a crowd of 5,000 and launched into the soils beneath Seattle.

Even though Bertha has now dug 1,000 feet, she still technically belongs to Hitachi. STP’s contract with Hitachi was structured this way to give crews the opportunity to work with Hitachi’s experts during this critical first phase of tunneling. Now that the machine has made significant progress, it’s almost time for Hitachi to hand STP the keys to Bertha.  

That hand-off should happen sometime in the next week, after the machine digs far enough to install the tunnel’s 200th concrete ring. The change of ownership won’t mean much to crews or Bertha – digging is digging, no matter whose name is on the machine’s title.

Still, it’s worth noting the change as a reminder of the precautions we’re taking to minimize risk as we build the tunnel. Another thing worth noting: Bertha’s dig is now 10 percent complete.

Bertha’s progress as of Dec. 5
Total distance traveled: 1,000 feet     
Number of rings installed: 147
Depth (to the top of the machine): 60 feet 

Previous updates

Nov. 25, 2013 update -- Bertha has much to be thankful for as she nears South Jackson Street

Nov. 14, 2013 -- Bertha takes on the complexities of King Street

Nov. 7, 2013 -- Several days at the dentist: new teeth will give Bertha more bite

Oct. 30, 2013 -- Bertha begins her week of scheduled maintenance

Oct. 24, 2013 -- Bertha closing in on King Street