State Route 99 Tunnell WA
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Description: State Route 99 Tunnel, also known as the Alaskan Way Viaduct replacement tunnel, is a significant infrastructure project in Seattle, Washington, designed to replace the aging and seismically vulnerable Alaskan Way Viaduct. Officially opened to traffic on February 4, 2019, the tunnel spans approximately 2 miles (3.2 kilometers) beneath downtown Seattle, providing a crucial north-south route for commuters and freight. The project, which cost around $3.3 billion, features state-of-the-art safety systems, including ventilation, fire suppression, and emergency exits. The tunnel's construction involved the use of "Bertha," one of the world's largest tunnel-boring machines, which faced several technical challenges and delays but ultimately completed its task, marking a significant engineering achievement and enhancing the city's transportation infrastructure.