MTA Halts Tunneling to Study Sinkage

Subway tunneling beneath the Hollywood Freeway near Universal City was temporarily halted Tuesday while Metropolitan Transportation Authority engineers attempted to determine what has caused three spots to sink slightly more than a level permitted by Caltrans.

MTA officials characterized the problem as a minor setback.

“This is not a serious situation,” Charles Stark, MTA project manager, said at a news conference. “We’ll hopefully have it resolved in a day or so. There are no structural problems or any possibility of structural problems on this freeway.”

Ray Hinton, permit engineer for the California Department of Transportation, said he wanted to “assure motorists that the freeway is absolutely safe.”

Three of the 200 points surveyed on the edge of the freeway near Lankershim Boulevard have slightly exceeded the 3.5-inch subsidence limit Caltrans set in a permit to the MTA, transit officials said. None of the spots exceed 3.8 inches of subsidence. Each of the spots is about the circumference of an automobile.

The average settlement of all 200 points is about one inch.

Ahmad Habibian, manager of technical services for the American Society of Civil Engineers, said the Caltrans limits are merely “warning lights.”

“The threshold is always set at a very comfortable level,” he said. “It doesn’t mean that there’s a serious problem.”

But state Sen. Tom Hayden, a frequent critic of the MTA, on Tuesday called for an independent assessment by the federal government into why the freeway has sunk much more than anticipated.

Hayden (D-Santa Monica) said in a statement: “The MTA is so obsessed with rushing this project along regardless of any other considerations because they want to make it irreversible before the courts can rule on whether they have violated environmental laws.”

MTA board member and Los Angeles County Supervisor Michael Antonovich, another subway critic, said the latest problems confirm his belief that the transportation agency should stop digging and build a light-rail system along the Hollywood and Ventura freeways.

Excavation in the San Fernando Valley’s loose, sandy soil has been plagued with sinkage problems. Contractors have attempted to firm up the ground ahead of digging machines by injecting it with an epoxy-like substance called chemical grout. But the expensive, time-consuming measure has met with limited success.

The first signs of excessive surface settlement occurred last year after a machine had dug 200 feet north of Chandler Boulevard. Work stopped for months while the machine was modified and $19 million in chemical grout was ordered.