- The double-decker Highway 99 tunnel that runs through a portion of downtown Seattle is expected to open in early 2019, according to The Seattle Times.
- The southbound section of the tunnel, which is part of the $3.2 billion Alaskan Way Viaduct Replacement Program, is nearing completion, allowing crews to start work on the northbound deck. A concrete mixer truck and other vehicles were able to make the journey across the tunnel for the first time last week.
- The decks and walls for both northbound and southbound lanes should be ready in March. Other elements of the project, including lights, signals, ventilation and fire sprinklers, must then be installed and tested. The Times said WSDOT will soon choose a contractor to demolish what remains of the original viaduct in 2019.
Bertha, the tunnel boring machine (TBM) used to dig the 1.75-mile Highway 99 tunnel completed its work in April of this year, nearly 29 months behind the original completion date, after being sidelined by a December 2013 breakdown.
What caused the TBM failure is still a matter for the courts. The project also encountered additional delays when, just a month after Bertha restarted tunneling operations in December of 2015, WSDOT and Gov. Jay Inslee halted digging after a sinkhole opened up near Bertha. STP filled the sinkhole and soon thereafter received the green light to begin tunneling again.
Barring mechanical issues, TBM's have made tunneling more efficient and cost-effective. Officials with the New York City Metropolitan Transportation Authority told The Wall Street Journal that crews had to manually dig a 120-foot tunnel at a cost of nearly $1 million a foot, whereas a 3-mile tunnel completed by TBM's cost only $19,000 a foot.
But Tesla and SpaceX founder Elon Musk still believes there's room for improvement. Musk started his own tunneling operation, called The Boring Company, which, according to the serial entrepreneur, will use new technology to dig tunnels faster.
After some test digging near the SpaceX headquarters in Hawthorne, CA, the Maryland Department of Transportation has given Musk conditional approval to dig a hyperloop tunnel from Baltimore to Washington, DC. However, DC officials said they're still in preliminary discussions about the project.