The $898-million Gold Line light rail extension project in Los Angeles is proceeding full speed ahead, with Los Angeles County Metropolitan Transportation Authority officials hoping the toughest challenges are behind them.
One of two tunnels achieves breakthrough on Los Angeles Gold Line.
Two 1.7-mile-long, 21-ft-diameter twin tunnels were completed Dec. 9 for the project, featuring the first-ever use of a double-gasketed, convex-convex joint system to keep them functional in a seismic event. "To this point, the completion of the tunnels was the biggest challenge on the job," says Mike Aparicio, project manager with Eastside LRT Constructors, the joint venture builder. "Now, for the next two years our focus will be on the underground stations and the completion of the five miles of at-grade rail work."
LRT, comprising Washington Group International, Obayashi Corp. and Shimmick Construction Corp., was awarded a $600-million design-build contract in 2004 to construct the six-mile-long project. It is an extension of the Pasadena Gold Line, which runs 13.7 miles from Pasadena to Union Station in downtown Los Angeles. A joint venture of Traylor Brothers/Frontier Kemper led the $130-million tunneling subcontract.
When complete in late 2009, the project will link Gold Line passengers from Union Station to East Los Angeles — an estimated 17-minute trip. Along the way, the extension will traverse two bridges, head underground for two stations, then make six more stops before ending its run.
A portion of the rail alignment was mapped through an existing school. After wrangling with the school district for two years, Metro agreed last October to contribute $35 million to help Ramona Opportunity High School build a new $48-million campus. "This was one of the most significant risks to the project," says Rick Thorpe, chief capital management officer with Metro.
Thorpe says the new school will be funded by $12 million from the project budget, with the rest to come from the state-funded Transportation Congestion Relief Program (TCRP). A contract for construction of the school will be awarded sometime next summer, he says.
Another snafu occurred 18 months ago when tunnel crews discovered the skeletal remains of more than 50 people buried near the eastern portal. Thorpe says Metro is still working with the city to identify and relocate the bones. "The remains dated back to the 1800's," says Thorpe. "And they were in unmarked graves, so the chances of finding any relatives are very slim."
The project is currently about 50 percent complete, with 60,000 cu.-yds of concrete being prepared for the two underground stations and crews beginning at-grade station construction, as well as laying out a total of 14 miles rail track for welding.
By mid-2007, Aparicio said the project will be 60 percent complete, with architectural finishes going up at the underground stations and construction on all eight stations underway.
To dig the tunnels, Metro purchased two German-made TBMs at a cost of $10 million apiece. Weighing more than two million pounds each, the twin pressure-face machines pulled more than 300 feet of tunneling equipment through alluvial soil at a rate of four inches per minute, excavating 21-ft-diameter holes about 60 ft below grade.
In all, the earth-pressure-balance machines moved a total of 233,000 cu.-yds. of dirt.
"This project set a precedent that we can successfully tunnel in the LA basin with virtually no impact on the public," said Eli Choueiry, Metro project manager. "Nobody knew we existed."
Choueiry said tunneling was completed without any "settlements, deferring site conditions, damage to infrastructure, or community complaints of any significance."
"We tunneled under the I-5 Freeway with no problems whatsoever," he said. "The greatest amount of settlement at any one location was .3 inches. This may be a record in the US."