Subway Builder Fixing Water Leaks in Tunnel : Safety: Some fear that the structure’s longevity could be compromised. But MTA says it remains sound.

A contractor has been patching cracks in portions of the new Los Angeles subway tunnels to fix water leaks that some experts say could reduce the life of the steel-reinforced concrete structure.

Charles W. Stark, subway project manager for the Metropolitan Transportation Authority, said the repairs have been made over the past week out of concern for the “quality and appearance” of the 1.8 miles of tunnel between Union Station and Pershing Square. Stark said he is confident that the cracks resulted only from normal shrinkage and do not reflect structural weakness.

On Monday, an outside panel of subway experts is scheduled to begin a review of the tunnels on the Metro Rail project. The panel was named in response to a Times article in August reporting that numerous segments of the tunnel’s concrete walls are thinner than the design-specified thickness of 12 inches.

Contractor Ronald N. Tutor said the leaks result from faulty design, not the quality of construction by his company, Tutor-Saliba Corp. He said that even if the water corrodes the reinforcing steel in the concrete, the tunnels will remain strong.

Tutor said he voluntarily made the recent repairs at his own expense, even though construction was completed in 1991.

“There was leakage in there that I thought (the transit agency) should take care of and they thought they should take care of,” Tutor said. “But they didn’t have a budget to do it. . . . It bugged me that there could be leaks dropping on the cars.” He estimated his company’s costs to be about $5,000.

The three-member review panel will report directly to MTA Chief Executive Officer Franklin E. White and to agency Chairman Richard Alatorre, who is a Los Angeles City Council member. White has directed the review panel to examine the structural soundness of the tunnels and the quality of supervision during construction.

MTA engineering staff and its construction management consultants have said they believe the structures are safe and sound.

Transit commissioners who were contacted said they hoped that the review panel, in addition to examining the concrete thickness, would assess any effect of the water leaks on the tunnel’s durability. The 4.4-mile Red Line subway, built at a cost of $1.45 billion, was intended to hold up for at least 100 years.

“I think they ought to look at anything that might have an impact on public safety and the quality of the construction and the oversight of the construction,” said Zev Yaroslavsky, a Los Angeles City Council member who is Mayor Richard Riordan’s designee to the MTA.

Yaroslavsky had asked engineering staff at an MTA meeting last month about the nature and extent of concrete cracking in the tunnels, but he said he has received no response.

Transit officials declined in interviews to identify how many leaks and cracks have been grouted during the past few days and said the information would be provided in the coming week.

Stark said the cracks being grouted are leaking water. Stark also said the cracks have been mapped, so that officials can monitor changes over time and after earthquakes.

A tour of the tunnels early last month, led by five transit officials and including a Times reporter and photographer, found cracks up to one-eighth of an inch wide and at least a dozen areas that leaked. In a handful of locations, water was flowing, rather than merely seeping, into the tunnel. An MTA spokeswoman, Stephanie Brady, said the locations were among those that might be grouted by Monday.

Officials say they do not know precisely how much water is leaking into the tunnels. But the tunnels were designed to prevent serious leakage.

At an extra cost to taxpayers of about $2 million a mile, the tunnels and stations were wrapped with a specially designed membrane of thick plastic to keep out water and explosive methane gas, which occurs in parts of underground Los Angeles. Contract specifications call for water leaks not to exceed 1/10th of a gallon per hour for any 100 linear feet of tunnel.

Records show that the most severe tunnel leaks have been in the structures between Union Station and the Civic Center station. But the transit agency is still faced with unresolved questions over whether the design, the quality of construction or some other factor is to blame.

Among those who want the independent panel to review any structural and safety implications of the leaks is C. Thomas Williams, environmental controls supervisor on Metro Rail from 1985 to 1989, who participated in the decisions six years ago that led to installing the plastic membrane.

Williams said the leaks show that the plastic membrane is being breached. “The tunnels are leaking, and that means the (membrane) is not holding,” he said. “And that is allowing highly corrosive water in, to attack the concrete and the rebar,” the rods of reinforcing steel that help the concrete withstand the bending during a major earthquake.

A consultant for the transit agency found in 1986 that ground water around Union Station contained hydrogen sulfide, a highly corrosive agent that had damaged pumping equipment at the site. “Materials or equipment exposed to these ground-water conditions for even short periods of time may require protection in order to prevent damage,” the firm’s report said.

Ultrasound testing conducted in August, 1992, for the transit agency found cracks “at a few locations” that extend through the concrete liner.

The cracked areas “did not have a significant reduction of strength,” according to a report by the firm that conducted the testing. However, the report noted that cracks “become a predictor of future deterioration” and “provide permeation of ground water to the rebar.”

The rods of steel would gradually swell as they corrode, structural engineers said, and eventually cause surrounding concrete to crack and crumble.

Frieder Seible, a professor of structural engineering at the UC San Diego, said the effect of the corrosion on the reinforcing steel poses concern regarding the long-term durability of the tunnel.

“I think it’s certainly something that should be looked at” by the review panel, said Seible, who led a team of structural experts retained by the California Department of Transportation to investigate the flattening of an elevated freeway in Oakland caused by the 1989 Loma Prieta earthquake.

Referring to the water intrusion within the subway tunnels in Los Angeles, Seible said: “It’s not something that will necessarily cause a major problem in the near future, but long term, certainly” it is a concern.

Stark, the subway project manager, said he was unaware that studies had found elevated levels of salts and hydrogen sulfide in the ground water. He said the transit agency has not conducted tests to identify the corrosiveness of the water that is leaking into the tunnels.

“I don’t believe it’s a concern at this point,” he said. “I don’t believe the water coming into the tunnels here is any more corrosive than water going into any other subway tunnel” in the nation.

However, Stark added: “We’ll talk to our design people and see if they think (testing) is necessary.”

According to interviews and records, the ground water extracted during subway construction at Union Station and its adjacent tunnels was so high in contaminants that a treatment plant was erected temporarily.

And hydrogen sulfide remains in the ground water at Union Station. The Catellus Development Corp., which is building an underground parking garage there, has to treat contaminated water removed from the site before discharging it into the Los Angeles River, according to Alex Fu, an engineer with the California Regional Water Quality Control Board.

Williams also said he is concerned that the subway’s plastic membrane may be failing to keep out methane gas. “If the membrane allows water in--it can allow gas in,” Williams said. “This review committee must address the situation of the membrane, the water and the gas.”

Twice in the last month, Los Angeles city fire crews have responded after tunnel sensors detected rising levels of methane. One incident interrupted northbound train service for about 45 minutes Oct. 1, when elevated levels were detected in a tunnel on the north side of Union Station that is used for transferring trains to the yards; the other event occurred the early morning of Sept. 24 between the Civic Center and Union Station, during hours when the system was not providing passenger service.

Both times, the subway’s ventilation fans flushed the gas out well before it was near any level of danger, said Robert Aaron, a city fire battalion chief.

Stark said the two alarms resulted from the highly sensitive methane detection equipment and that the gas levels posed no danger.