BELLEVUE, Wash. – Sound Transit has reached a five month earlier timeline on Bellevue on Friday.
The excavation of its 2,000 foot East Link Light Rail tunnel has been completed on its north portal, which tunnel builders call a "hole".
The method used differed significantly from Bertha, the giant tunnel boring machine used to tunnel the much longer, larger and deeper tunnel near Seattle's shores, which will replace the Alaskan Way viaduct.
Two excavators using a cutting tool with rotating iron teeth cut and dug a circle of 34-foot-wide tunnels at work 24 hours a day, seven days a week for about a year.
"The secret was that the ground was much better than anyone expected and the contractor worked really hard with our engineers and came up with ways to work faster," said Chad Frederick, Principal Construction Manager at Sound Transit.
The tunnel has a slope of 30 feet from its south portal at 112th Avenue NE and Main Street on the north portal north of Bel Levue Town Hall, and the peak runs between 12 to 34 feet below the surface.
"Part of the reason we chose this excavation method was because it could cope with supplies to the flatness of the tunnel as opposed to using the tunnel bore machine, like Bertha, which began much deeper," Frederick said.
He said the crew had no stalling problems as Bertha did early in his tunneling career.
Despite running five months ahead of schedule, Sound Transit CEO Peter Rogoff said it's too soon to tell if the project will go under budget.
"We always save money when things are ahead of schedule, especially in this environment where prices are rising on some of our other projects," Rogoff said. "It's a very competitive time for work and it can be expensive if we try to secure more contracts."
Rogoff said that Sound Transit was exercising its option to order additional cars in the face of increased passenger numbers by the time Eastlink opens in 2023 to trade.