Thin Subway Walls Pose No Risk, MTA Says

More than half a mile of tunnel walls constructed earlier this year along the Vermont Avenue subway line are thinner than originally designed, transit officials disclosed Friday, but a review team has concluded that the walls can still withstand a major earthquake.

The undersized walls span nearly 12% of the twin tunnels that run north-south from Hollywood down to Koreatown, a figure that alarmed some critics of the $5.8-billion subway. The problem is far more extensive than previously revealed, the new data shows.

But transit officials, facing what promises to be a grueling state Senate hearing Tuesday on a series of setbacks in the Los Angeles project, downplayed any potential hazards. And they said the construction problem had nothing to do with the spectacular June sinkhole that engulfed part of Hollywood Boulevard at the top of the Vermont leg.

“To say that the Vermont tunnels are safe is to understate just how safe they really are,” said Stanley G. Phernambucq, the Metropolitan Transportation Authority’s new construction chief.

MTA Chief Executive Officer Franklin E. White said in an interview that the shortcomings in the tunnels should not alarm the public because they fall within acceptable ranges. “In a tunnel of this length, it’s customary that some pieces are not going to be [the required] 12 inches thick, and there is no danger at all, no risk,” he said.

The MTA has been dogged by questions about thin tunnel walls since mid-1993, when it was disclosed that major segments of the now-open Downtown subway’s walls were built thinner than designed.

A panel of outside specialists at that time concluded that the Downtown subway would still be safe if needed repairs were made, as they later were.

But new questions arose six weeks ago after The Times disclosed that one segment of wall along the next major leg of the subway, the Vermont Avenue line, was as thin as 8.5 inches--or nearly a third thinner than specified under contract.

The latest disclosure came as the MTA withstood a barrage of attacks from Washington and Sacramento over construction and financial problems on the subway, one of the most expensive public works projects in U.S. history. The attacks already have threatened federal subway funding, and some politicians want to pull the plug on the project altogether.

But MTA officials, in a statement released Friday, said a quality-assurance team made up of project engineers has determined that the tunnel walling meets or exceeds earthquake design standards and should withstand “well in excess of any anticipated stresses.”

Under the multimillion-dollar contracts with the subway builders from the private sector, the tunnel walls are designed to be 12 inches thick. But that was not always the case along the more than 23,600 feet of walling that make up the Vermont Avenue tunnels, running between Wilshire and Hollywood boulevards, officials found.

In nearly 2,800 feet of tunnel--or 11.7% of the total footage--the walls were thinner than 12 inches because the tunnel itself was not aligned precisely on course during digging and the train track had to be rerouted to accommodate the problem, officials said.

Of that total, more than 700 feet of walling measured between nine and 10 inches, and the contractors had to go back and add double steel reinforcing to ensure the stability of the tunnel liner, officials said.

In an additional 398 feet, the walls were even thinner than nine inches, and the tunnel had to be re-mined altogether. It was during a re-mining operation in June near the intersection of Vermont and Hollywood Boulevard that the 70-by-70 foot sinkhole swallowed part of the street, although no official cause for the accident has been determined.

The remainder of the thin walling, between 10 and 12 inches thick, will be allowed to remain as is.

The findings appear to confirm concern raised in January by an inspector for the project’s construction manager, who warned that officials continued to pour concrete over most of Vermont Avenue without determining why a portion of the tunnel was much thinner than designed.

The inspector said the problem had been ignored for five months, and he asked skeptically whether officials had “not learned anything” from the thin walls along the Downtown line.

But MTA construction executive John Adams said Friday that lessons were in fact learned from the Downtown episode, as new oversight procedures were instituted to allow supervisors to better anticipate thin-wall problems. He said he was happy with the results.

“You come in with an ideal story where you say to yourself that if the tunnel is [dug] perfectly . . . you’re going to get 12 inches all around,” Adams said. “But that’s not the real world. . . . Construction is not a precise science.

Nonetheless, the MTA contracts specify tunnel walls of at least 12 inches, and Adams said all costs connected to fixing the lapses would be borne by the contractor that built the tunnels, the consortium of Shea-Kiewit-Kenny. He estimated that the re-mining operation cost between $600,000 and $1 million, with added costs for double-steel reinforcements.

Officials at SKK, fired last month from the remainder of the Hollywood project, could not be reached for comment late Friday. They are planning to sue the MTA over their billings.

Some MTA critics were reluctant to accept the agency’s assertions.

James Pott, a Long Beach engineer who served on the subway’s construction arm, characterized the agency’s explanations as “doublespeak,” saying that its assertion about the safety of the thin walls was “arguable at best.”

And community activist John Walsh, calling for an independent review of the problem, asked: “Why wasn’t it built according to specifications? . . . If they designed it at a certain number of inches, they must have done it for a reason. If it’s an inch less than they designed, it’s an inch less than safe. We’ll find out in the next earthquake.”