SEATTLE - Crews have spent months working on the underground tunnel for the Link light rail, which will connect downtown Seattle to the University District near Husky Stadium with stations in between at Capitol Hill.
So far, the $1.8 billion project involved digging, drilling and 28,000 truckloads of dirt and rock crushed to make way for the light rail trains.
KIRO 7 Eyewitness News reporter Jeff Dubois toured inside of the underground tunnel to check out the progress on the next phase of the Central Link light rail system.
“It took about four or five months each,” said Brad Cowles of Sound Transit, who is overseeing the project. “You have got a 5,400-foot-long station, 60-feet wide, 80-feet deep. You could lay a 50-story building in here, basically.”
Cowles pointed out a massive pit, where the underground Capitol Hill station for the light rail trains will be.
During the construction, crews have had to work around the critical water and sewer lines, and the pipes carrying gas and electrical wires to thousands of homes and businesses on Capitol Hill.
“The opposite end over there, that’s where they came from the University of Washington,” Cowles told Dubois.
The tunnel has been completely dug, and wall panels have been placed using high-precision computers and lasers. Also, the cement floor has been poured.
Massive fans push oxygen down into the tunnel for ventilation for workers.
In the north tunnel, people will take the train from downtown Seattle up to Capitol Hill. It is a 5 percent grade, which is the steepest grade for a light rail. If the grade was any steeper, the train wouldn’t be able to climb the hill.
One of the biggest challenges and risks during the dig was under Interstate 5.
“And we’re right under I-5 right now, so your I-5, the mainline southbound, is running about 20 feet above the top of the tunnel here,” said Cowles.
According to Cowles, I-5 was the tightest clearance for the whole project, and any miscalculations could have caused sink holes or damage to the roadway.
During the construction, the tunnel boring machine, a loud, vibrating, mammoth-sized drill, rumbled right under commuters for about 96 hours in November 2011.
“It was very technical, very nerve-wracking. Only about 13 feet clear under the express lanes, and we had to keep the thing open to traffic,” said Cowles.
Engineers said the precision survey work that had been done was spot on, which cleared the section under I-5 without a problem.
Another critical part of the tunnel is at the lowest point directly under the I-5 express lanes, where everything will drain.
“It will handle any water, any leakage that comes through the tunnel, drip off trains, and in the unlikely event of a fire, to take care of any water that flows down here,” said Cowles.
Doorways are placed every few hundred feet on one side of the tunnel in case of an emergency. Passengers can get off one train, go through a passageway and be loaded onto another train.
There is still more work that needs to be done before passengers will be carried through the light rail tunnels.
Starting in March 2013, the trail rails will start being placed.
Sound Transit said the project is on budget and on schedule, but passenger service will not begin until late 2016.
According to Sound Transit, once the tunnels are complete, a trip from Husky Stadium to Westlake Center in downtown will take about six minutes and is expected to add 70,000 riders to the Link light rail system by the year 2030.