This is a most interesting story of the world's largest tunneling machine that is working on redesigning Seattle's downtown. With completion of the tunnel, the redevelopment on the waterfront, and a revitalization of this part of the city, while improving traffic flow. So while not directly car related, it is an astonishing piece of modern engineering.
Building a new State Route 99 through Seattle
In summer 2013, the world’s largest-diameter tunneling machine began a historic journey beneath downtown Seattle. Its purpose: dig a tunnel to replace the SR 99 Alaskan Way Viaduct, a double-deck highway that has spanned the downtown waterfront for more than half a century.
The machine’s task sounds straightforward enough, but the story behind it is complicated. It begins with an earthquake in 2001 that damaged the viaduct and led to a decade of debate about how to replace the structure. The story's conclusion is unfolding now, as we at the Washington State Department of Transportation, along with our agency partners, build a new SR 99 corridor through Seattle that includes:
- A two-mile-long tunnel beneath downtown Seattle.
- A mile-long stretch of new highway that connects to the south entrance of the tunnel, near Seattle’s stadiums.
- A new overpass at the south end of downtown that allows traffic to bypass train blockages near Seattle’s busiest port terminal.
- Demolition of the viaduct’s downtown waterfront section in 2016.
- A new Alaskan Way surface street along the waterfront that connects SR 99 to downtown.
The tunnel will change the way traffic uses SR 99 in Seattle. Drivers approaching the tunnel from either direction will face a choice depending on their destination: use the tunnel to bypass downtown or exit to city streets and head into downtown. At the tunnel’s north end, downtown access will be similar to today, with on- and off-ramps near Seattle Center. From the south, new on- and off-ramps will connect SR 99 to downtown via the new waterfront street.
Halfway there
Half of the viaduct is already gone, demolished and replaced by our crews at the south end of downtown, near Seattle’s stadiums. Completed on budget and one year ahead of schedule, this new section of SR 99 connects to the remaining viaduct along the waterfront to keep SR 99 traffic moving until the tunnel opens in late 2015.
Tracking Bertha, the SR 99 tunneling machine
On July 30, Bertha, the world's largest tunneling machine, began digging the SR 99 tunnel beneath downtown Seattle. To make it easier to track her progress, we’ve divided the tunnel route into 10 zones. Each zone has something about it that makes it interesting, such as a certain soil type or a noteworthy location beneath the city. The map shows the entire tunnel route. The machine is currently located in zone 1. A full description of all the zones can be found below. Click the menu bar listed below to view each zone.
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