Tunnel Expert Assails Choice of Equipment

The two machines now digging subway tunnels in North Hollywood are wrong for the job because they increase the risk of ground slumping, a leading expert said Thursday--even as evidence appeared that the Metropolitan Transportation Authority is bickering with its subway contractor over blame for sinking damage to more than a dozen buildings there.

“I have said from Day 1 that I didn’t like the way the Lankershim [Boulevard] tunnels are built,” said Dan Eisenstein, a civil engineering professor at the University of Alberta.

Eisenstein, appointed by MTA board director and Los Angeles Mayor Richard Riordan to lead an independent review panel of tunneling experts, said that the type of excavating machine being used in North Hollywood is rarely used anywhere in the world on sandy soil, such as prevails in the San Fernando Valley.

The machine allows too much subsidence at the surface and demands expensive grouting to harden the ground ahead, Eisenstein said he told an MTA board meeting Thursday.

John J. Adams, the MTA’s deputy executive officer for construction, said that if the agency was “deciding on the job today,” a different type of machine would have been chosen. But there was little American experience three years ago with more efficient “earth balance” tunneling machines now in common use, Adams said.

Eisenstein did not directly link the tunneling for the MTA’s Red Line 60 feet beneath Lankershim Boulevard to the damage plaguing more than a dozen businesses on the street above--sinking floors, cracking walls and burst water mains. Whether the tunneling caused the damage is still at issue.

But in a separate action, The Times obtained a copy of a letter to the MTA from the firm doing the actual tunnel digging, the Obayashi Corp., complaining that the MTA is trying to blame the company for damage to the surface buildings. The company in turn blamed the MTA.

In the March 27 letter, Obayashi project manager Carl Linden wrote:

“After the owners of structures located along Lankershim Boulevard have complained of cracks and sinkages, the authority has begun assigning responsibility and blame to Obayashi, when actually the onus lies within the authority’s own organization.”

Adams said he could not comment on the letter.

A spokesman for Obayashi, one of the world’s 10 largest construction firms with annual revenues of $14 billion, said the company could not reply directly to questions because the MTA orders contractors not to speak to the news media.

The assessment of blame is critical, because the repair bill for the damaged structures could escalate to millions of dollars.

In a timely example of the potential for runaway costs, on Thursday morning MTA director and Los Angeles County Supervisor Zev Yaroslavsky visited the El Sombrero nightclub on Lankershim Boulevard, which has the worst reported damage on the street.

Wednesday, Yaroslavsky had announced that the MTA--without conceding responsibility--was willing to pay to repair a 15-inch slump in the nightclub’s floor, estimating the bill at about $20,000. Thursday, however, he said the agency might have to pay as much as $100,000.

A number of El Sombrero’s neighboring businesses have joined a $2-billion lawsuit against the MTA filed by property owners in Hollywood who allege the MTA’s tunneling there also caused damage to their buildings.

Eisenstein said the ground subsidence problem in both places could have been largely avoided by using modern “earth-balance” tunneling machines, popular in Europe and Canada.

Although they cost twice as much as the $2.5-million open-face shield model used by the MTA’s contractor, the more expensive machine would have reduced the need for grout by 90%, Eisenstein said.

To date, that would have saved $17 million of the $19 million in unexpected grouting costs the MTA reports the project has incurred, with less than half of the work completed.

“If we were deciding on the job today, of course we would have chosen an earth-pressure balance machine,” Adams said. “But three years ago, there was little experience with this type of machine in the United States.”

Grout--a substance pumped into soft ground to create a firm surface through which to dig--has caused much of the inconvenience to business owners on Lankershim Boulevard. The chemical and silicate cocktail is mixed 24 hours a day on the street with a deafening roar and injected directly into holes in the pavement by truck-mounted machines that block curbs for a quarter-mile at a time.

It rises in a fine white cloud of powder that settles faster and wider than diligent MTA crews can clean. Business owners complain that the noise, lack of parking and dust have scared off customers.

Through March 1, the tunneling project was 367 days behind schedule because of repeated halts to stop and grout. The latest 24-hour halt occurred Wednesday after a half-inch ground settlement was discovered outside the First Interstate Bank building in the 4400 block of Lankershim. Previous to that, work had stopped for 10 days of grouting March 10 after the sinkage of the nightclub was discovered.

Interviews with business people along the two-block stretch of Lankershim found that more than three quarters had suffered floor, wall or water-pipe damage within a month of the time Obayashi dug two tunnels that will ultimately carry northbound and southbound trains under the street.

“They are destroying my business and I feel helpless,” said Al Siegel, who has run Al’s Discount Furniture in the 4900 block of Lankershim Boulevard for 30 years.

“Last year, we did $5 million here. This year, we’ll be lucky to do half that. They close down Lankershim all weekend. I have six salesmen on the floor looking at each other. They can’t believe this is Al’s Furniture.”

Three business owners, in fact, assert they have been forced out of business:

* The owner of Toyota of North Hollywood, whose car lot has been blocked for 18 months by huge chemical grout tanks, closed his Mazda dealership in that location in mid-March.

* Co-owners of Cousins Country Cafe said the noise, dust and floor cracks forced them to close two months ago.

* The owner of El Sombrero said she has already lost $100,000 and expects to be closed another two months. Speaking of the repairs the agency has promised, she said: “I appreciate everything you’re doing, but how am I supposed to keep my bills up and how am I supposed to eat in the meantime?”

Blue Shaw, owner of the Blue Saloon, said the MTA had broken promises to him to mitigate the problems that construction work caused his bar by paying half his advertising bills. The agency made payments for 13 weeks and then stopped, saying money for that program was exhausted, he said.

“They’re liars, cheats and thieves,” Shaw said. “They’re trying to be concerned for a short time so they can continue doing what they’re doing.”

According to engineering sources with inside knowledge of the subway project, Obayashi originally proposed five different versions of a tunnel-boring machine meant to combat ground settlement of the kind the business owners complain of.

Those designs included a movable hood and a movable “breasting table” that would have allowed miners to control the area’s loose, sandy soil slipping at the tunnel face, the sources said.

Slipping sand creates voids in the space between the tunnel and the surface. Over a period of time, ranging from a few days to a few months, the voids fill with dirt slumping from the surface. Brittle iron water pipes can then break when the structures above them sink by as little as half an inch, experts say.

Water escaping from the broken pipes then lubricates the loose soil, helping it slide faster. When dirt supporting a building washes away, the structure’s walls and floor can crack or sink.

But the firm of Parsons-Dillingham--which oversees the North Hollywood subway construction project for the MTA--rejected or modified all those designs, sources said. That left Obayashi with a so-called open-faced shield equipped with a fixed hood and a fixed breasting table--the type Eisenstein condemns.

The MTA management team favored that machine, which is now being used in the tunnel, because it would cost less, allow geologists to inspect soil during the digging process, and speed up digging, the sources said.

With that machine, miners stand on the breasting table in front of the shield, softening up the dirt ahead with jackhammers called “spaders.” Rocks rain down on their hard hats, and work often stops when miners are forced to duck falling boulders.

Eisenstein recommends that the MTA in the future buy its own “earth-balance” shield machines, which exert pressure against the top of the tunnel face, preventing surface sag.

“In tunneling, either you change the ground to suit the technology that you have, or you select the technology to suit your ground,” Eisenstein said in an interview. “The contractor at Lankershim has gone for the first alternative, resulting in a machine that is cheaper to build and maintain, but which ends up costing the tunnel owner more in the long run because it requires extensive ground treatment.”