Bertha, the world’s largest tunneling machine, officially started her two-mile journey beneath downtown Seattle on July 30, 2013. Unlike her official dedication on July 20, a public event attracting more than 5,000 people, there were no crowds or hoopla surrounding the dig. Bertha arrived in Seattle on April 2, 2013 from Osaka, Japan.
On Tuesday afternoon, Bertha’s five-story tall cutterhead broke through the north wall of her 80-foot deep launch pit at the south end of downtown Seattle. Her ETA near the intersection of Sixth Avenue North and Harrison Street in South Lake Union is about 14 months. Crews working with the Washington State Department of Transportation (WSDOT) will slowly push forward to begin with, digging about six feet per day. But by the time Bertha is beneath downtown, she will be digging up to 35 feet per day.
The SR 99 runnel route is divided into 10 separate zones, each with its own unique underground landscape. In the first zone, crews strengthened or replaced fill soils dumped there by the city’s early settlers while building protected areas where they can inspect the machine.
The project was designed so there would be opportunities to test the machine and make sure Bertha is functioning properly before she arrives beneath downtown Seattle. As WSDOT administrator Linea Laird of the Alaskan Way Viaduct Replacement Program explained, “If Bertha was learning to ride a bike, the initial section would be her training wheels.”
Bertha is keeping in touch with her fans, updating her progress since December on Twitter, where she’s attracted nearly 5,000 followers. On Tuesday, she said she was ready to go: “About to start tunneling,” tweeted @BerthaDigsSR99. “I should say something profound, something Neil Armstrong-ish. Fortunately, I’m out of characters. Let’s dig.” The tunnel is scheduled to open to drivers in late 2015.
Milepost 31 Speaker Series – Tracking Bertha’s Progress Beneath Downtown Seattle
Join WSDOT’s monthly speaker series to learn what Bertha will encounter as she digs through eight different types of soil, passes beneath other tunnels, and digs as deep as 200 feet beneath downtown Seattle.
- Thursday, August 1, 2013
- 6-7 PM
- Milepost 31, 211 First Avenue South, Seattle
Milepost 31 is open Tuesday-Saturday, 11AM to 5 PM, and 8 PM on First Thursdays. Admission is free. After the talk, take in the First Thursday Art Walk in Pioneer Square. Free parking for First Thursday Art Walk patrons in Pioneer Square.