The Washington State Department of Transportation (WSDOT) decided to give it more time when it comes to the Highway 99 tunnel.
Originally set in a highly aggressive schedule, which included a November 2015 deadline, the project now carries a November 2016 completion date after state officials met on May 27.
By pushing the timeline back 360 days, WSDOT is expecting bids to come in lower, and the calendar cushion also will give the winning contractor the time needed to deal with an extremely complex project.
The design for the Highway 99 tunnel calls for a 56-ft-wide hole underneath downtown Seattle, which will require the world’s largest-ever boring machine. Taking the drilling at a slower pace will allow for more deliberate soil removal, because an error while executing that task could cause ground settlement that threatens building foundations. WSDOT believes 37 buildings located on or near the proposed tunnel could be affected by soil settlement.
The contractor also will have to construct a 30-ft roadbed each way, two 11-ft lanes and shoulders 2 and 6 ft wide.
Bids are due in October, and the finalists are AWV Joint Venture, Seattle Tunneling Group and Seattle Tunneling Partners. The project could cost as much as $1.09 billion.
One drawback in pushing back the completion date of the Highway 99 tunnel is requiring an extra year of use out of the Alaskan Way Viaduct. The structure, built in 1953, was a victim of the 2001 Nisqually earthquake, and Washington Gov. Chris Gregoire declared the viaduct a hazard that had to be taken down by 2015. WSDOT said the structure will be inspected quarterly and will be reinforced if necessary.
“It’s a trade-off. Time is money,” Transportation Secretary Paula Hammond told The Seattle Times. “What’s important is to get the project started now so we can minimize the risk of inflation and cost pressures.”
