Bertha's trailing gear first into the pit

Last week, crews used a massive red crane to begin lowering the first large pieces of Bertha, the SR 99 tunneling machine, into the 80-foot-deep pit (pdf 485 kb) where she’ll start tunneling this summer. First up: the trailing gear, which will serve as Bertha's support system during tunneling by providing her with all of the equipment and materials she'll need to tunnel beneath downtown. The trailing gear accounts for much of the 326-foot-long machine's total length.

Crews started by lowering the 50-foot-tall, 400-ton section of trailing gear that houses Bertha's electrical systems. That piece was followed by a 750-ton section that includes storage tanks for soil conditioners, grout and other liquids needed during tunneling. It's also equipped with gear to bring in the curved concrete segments that will form the tunnel walls. A third piece of trailing gear will be lowered into the pit in the coming days.    

Reassembling Bertha’s 41 pieces and testing the completed machine will take two to three months. Crews from Hitachi Zosen, Bertha’s manufacturer, are assisting throughout the process. Bertha won’t officially become the property of Seattle Tunnel Partners, WSDOT’s contractor, until she’s successfully tunneled approximately 1,000 feet beneath Seattle.

Our construction cameras offer frequently updated photos of the action, and you can get regular updates from Bertha herself by following @BerthaDigsSR99 on Twitter. A full photo gallery of the machine is available on Flickr.