viaduct replacement

Cascadia-Arup Report: Deep Bore Tunnels @ $200M-$700M Per Mile

A report titled “Large Diameter Soft Ground Bored Tunnel Review” has just been released by the transportation think tank Cascadia Center and global engineering and consulting firm Arup. It strongly suggests that a new state cost estimate for a deep bored tunnel of approximately two miles to replace the aging Alaskan Way Viaduct could be greatly inflated. The state’s Alaskan Way Viaduct Stakeholders Committee (SAC) pegs the cost of the one-mile tunnel at $3.5 billion, but the Cascadia-Arup report surveyed deep-bored vehicle tunnels worldwide and found costs typically fall in the range of $200 million-$700 million per mile, for large diameter soft ground bored tunnels, created with assistance of a tunnel boring machine (pictured below at right). A Nov. 20 Read More ›