Seattle’s Alaskan Way Tunnel: Everything You Need to Know
The Alaskan Way Viaduct replacement tunnel, officially known as the State Route 99 tunnel, is a 1.76-mile-long bored tunnel that carries State Route 99 under downtown Seattle, Washington. Opened in February 2019, it replaced the aging Alaskan Way Viaduct, a double-deck elevated highway that was vulnerable to earthquakes.
The tunnel was designed to improve traffic flow and waterfront access in Seattle, while also reducing the risk of structural failure in the event of a major earthquake. Let’s delve deeper into the tunnel’s history, construction, and impact on the city.
History and Need for the Tunnel
The Alaskan Way Viaduct, built in the 1950s, had become structurally unsound and posed a significant safety risk. It was particularly susceptible to damage from earthquakes. After years of debate and planning, the decision was made to replace the viaduct with a tunnel. This decision aimed to maintain SR 99’s transportation capacity while freeing up the waterfront for redevelopment.
Construction and “Bertha”
The tunnel was bored by a massive tunnel boring machine (TBM) nicknamed “Bertha.” The Alaskan Way Viaduct replacement tunnel project experienced significant delays due to Bertha breaking down several times during the digging process. Repairs and unexpected obstacles added years to the project timeline and millions to the overall cost. Despite the challenges, Bertha successfully completed the tunnel bore in 2017.
The Tunnel’s Features and Operation
The Alaskan Way Tunnel is a double-deck tunnel, with two lanes of traffic in each direction on separate levels. It has no exits or entrances within the downtown core. This design helps improve traffic flow by reducing congestion. Safety features include ventilation systems, fire suppression equipment, and emergency exits. A toll was initially implemented to help pay for the tunnel’s construction, but it was eliminated in 2021.
Impact on Seattle and the Waterfront
The opening of the Alaskan Way Tunnel and the subsequent demolition of the viaduct have significantly transformed Seattle’s waterfront. The removal of the viaduct has opened up new opportunities for waterfront development, creating pedestrian-friendly spaces and improving access to Elliott Bay. While the tunnel has helped to improve traffic flow, it’s important to note it is still a route that can experience congestion at peak times.
Frequently Asked Questions
How long is the Alaskan Way Tunnel?
The Alaskan Way Tunnel is 1.76 miles long.
Why was the Alaskan Way Viaduct replaced with a tunnel?
The Alaskan Way Viaduct was structurally unsound and vulnerable to earthquakes. The tunnel was chosen as a replacement to ensure a safer and more reliable transportation route.
Is there a toll to use the Alaskan Way Tunnel?
No, the toll on the Alaskan Way Tunnel was removed in 2021.
What happened to Bertha, the tunnel boring machine?
After completing the tunnel, Bertha was partially dismantled. Some parts were recycled, and some were kept for historical purposes.
How has the tunnel impacted Seattle’s waterfront?
The tunnel’s construction and the removal of the viaduct opened up the waterfront for redevelopment, creating new public spaces and improving access to Elliott Bay.
Summary
The Alaskan Way Tunnel is a crucial piece of infrastructure that has transformed Seattle’s transportation landscape and waterfront. While its construction was fraught with challenges, it now provides a safer and more efficient route for SR 99 traffic under downtown Seattle, freeing up the waterfront for redevelopment and improved public access.
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