Watch: East Link Light Rail extension reaches milestone 5 months ahead of schedule
BELLEVUE, Wash. - Sound Transit reached a milestone five months ahead of schedule underneath Bellevue on Friday.
The method used was far different from Bertha, the giant tunnel boring machine used to tunnel the much longer, larger and deeper tunnel near Seattle’s waterfront that will replace the Alaskan Way Viaduct.
Two excavators, using a cutting tool with rotating iron teeth, took a cut and dig approach - carving out a circular 34-feet-wide tunnel while working 24 hours a day, seven days a week for roughly one year.
“The secret to it was the ground ended up being a lot better than anybody anticipated and the contractor worked really hard with our engineers and came up with ways to work faster,” said Chad Frederick, Principal Construction Manager with Sound Transit.
The tunnel has an incline of 30 feet from its south portal at 112th Ave NE and Main Street to its north portal just north of Bellevue City Hall, and the top runs between 12 to 34 feet below the surface.
“Part of the reason we chose this excavation method was because it could deal with utilities at the shallowness of the tunnel as opposed to using the tunnel boring machine, like Bertha, which started out much deeper,” said Frederick.
He said the crew didn’t run into any blocking problems like Bertha did early in its tunneling career.
Although they're running five months ahead of schedule, Sound Transit CEO Peter Rogoff said it’s too early to tell if the project will come in under budget.
“We always save money when things are ahead of schedule, especially in this environment where prices are going up on some of our other projects," said Rogoff. “It’s a very competitive time for labor and it can get expensive as we try to secure more contracts."
Rogoff said Sound Transit exercised its option to order extra train cars in light of increased ridership predictions. The hope is the cars will arrive by the time Eastlink opens for business in 2023.