The SR99 tunnel in Seattle, Washington, is two miles long and carries two traffic lanes plus a safety shoulder in each direction. It replaces the seismically vulnerable Alaskan Way Viaduct.
It was built using a record-breaking tunnel boring machine, Bertha, which was out of action for two years while repairs took place (link opens in new tab).
Celebratory events were held this weekend.
“This is a game changer,” said transportation secretary Roger Millar. “Our number one goal was to remove a vulnerable structure from our highway system. Along the way we reshaped a major transportation corridor that is a key component of the mutlimodal transportation system we and are partners are building for the Puget Sound region.”
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