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Address 111 McInnis Parkway, San Rafael, CA, 94903, US
Phone 415-507-5000
Fax 415-507-5100

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Tunnelling under the city

For 60 years, the Alaskan Way Viaduct has been a fixture of the Seattle waterfront and a vital link in the State Route (SR) 99 corridor through the city. As the 20th century drew to a close, the double-deck highway structure was already showing its age. But in 2001, the 6.8 magnitude Nisqually earthquake sealed its fate, sinking sections of the viaduct several inches. After the earthquake, crews immediately stabilized the structure and everyone starting asking, “Now what?” Fast forward 12 years and we know the answer: a two-mile bored tunnel beneath Seattle 200 feet underground at its lowest point - connected to a mile of new highway in the southern end of the city. But getting to that answer took more than 90 design alternatives that included combinations of new elevated roads, surface streets, bridges and tunnels.