The Federal Highway Administration has approved plans to replace the State Route 99 viaduct through downtown Seattle with a tunnel.
State transportation officials say the federal agency signed an agreement Tuesday to allow Washington state to begin final design and construction of the 1.7 mile bored tunnel to replace the two-level viaduct along Seattle's waterfront.
The highway administration decision ends a 10-year environmental review of the $2 billion project. Without unexpected problems or lawsuits, the tunnel is projected to open in 2015. A new promenade will run along the waterfront.
The federal announcement comes one week after Seattle voters gave their OK for the project.
