Repairs in Downtown Subway Nearly Done : Transit: MTA believes it has corrected problem of thin tunnel walls. But questions linger about the work.

More than 2,000 tons of concrete material has been pumped to repair defective subway tunnels already open to passengers in Downtown Los Angeles, and engineering specialists say the work is nearly complete.

The repairs began in March after tests verified that numerous areas of the tunnels were built with concrete walls thinner than designed, were cracked or were leaking water.

“With the work that’s been under way, I think we will come out with what we intended to purchase” when the tunnels were constructed, Franklin E. White, chief executive officer of the Metropolitan Transportation Authority, said in an interview. “The bottom line is, if we paid for it, we want it.”

But questions have emerged regarding the tunnel construction and the scope of the recent tests and repairs performed for the MTA.

Some areas of the tunnels were not examined for concrete thickness, records show. And water entering the tunnels near Union Station was not sampled--although previous tests had found the area to contain the highest concentrations of corrosive, hydrogen sulfide along the subway route.

Transit officials hoped that the recent repairs would put to rest what White has called a “painful chapter” for the subway, which opened to passengers in January, 1993.

The Times reported in August, 1993, that sections of the concrete tunnels between Union Station and Pershing Square were built as thin as 4.87 inches--compared to the minimum designed thickness of 12 inches.

White appointed a panel of outside specialists in the fall of 1993 to examine the structures. The panel concluded in February that despite the deficiencies the tunnels would remain safe if the filling of voids in the concrete and other recommended repairs were performed.

Over the next eight months, the nation’s newest subway was converted into a construction site.

During the late night and early morning, crews of seven men mixed thousands of bags of cement with water and other materials, then pumped it into the tunnel crowns to fill the air voids.

By day, the compressors went silent, but chalky grout that streamed from the tunnel walls onto the tracks can still be seen.

While the tunnel repairs were under way, other problems confronted transit officials: Sinkages occurred along Hollywood Boulevard, several miles away, damaging buildings and forcing a halt to the excavation. Citing displeasure with the project’s construction quality, the Clinton Administration took the extraordinary step Oct. 5 of suspending $1.6 billion in future funding. The funding was restored Nov. 10 after the MTA dissolved its construction subsidiary, ousted the subsidiary’s president and made other organizational changes.

Meanwhile, the FBI and the inspector general of the U.S. Department of Transportation pressed their investigations of the project. “The efforts we have ongoing with the subway will continue,” said Lawrence H. Weintrob, deputy assistant inspector general for auditing.

People familiar with the inquiries say investigators are examining, among other things, the construction of the tunnels, including the installation of a protective plastic liner that has failed to shield the subway Downtown from water and potentially toxic and explosive gases.

The subway project’s chief inspector has told a review panel that the liner was at times installed negligently, records show. The Times also reported in May that gas intrusions throughout the subway have forced the use of ventilation fans on hundreds of occasions.

White negotiated an agreement earlier this year requiring one tunnel builder, Tutor-Saliba Corp., to perform the repairs on 1.8 miles of the subway at no expense to taxpayers. But now, eight months after the work began, Tutor-Saliba is threatening to seek payment for some of its costs.

“It appears that our commitment to be a good corporate citizen has been taken advantage of,” said company President Ronald N. Tutor in a letter this month to White. Tutor criticized the MTA for forcing his company to fill air voids at scores of locations, many of which had not been identified before the work began.

“We feel that this has been a research project at our expense,” Tutor wrote. “This MUST stop!” Tutor told White he would inform him of the amount he is seeking from the MTA when the repair costs are totaled.

Tutor declined in an interview to estimate how much his company has spent on the repairs. Based on the price of the grout material and typical labor costs, experts estimated that the work to date has cost up to $1 million.

Tutor-Saliba and a joint venture partner built the twin tunnels between Union Station and Pershing Square and excavated the site for the Civic Center station for $89 million, or 45% over the competitive bid.

Some of the concrete-based grout material used for the recent repairs was pumped into large cavities between the outside of the tunnel shell and the surrounding soil. If left unfilled, engineers say, the cavities could contribute to water-intrusion problems or settlement of ground surfaces.

The grout also has filled extensive air voids, of up to 3 3/4 inches deep, within the crowns of the tunnels.

The voids, running many feet along the tunnel, apparently have served as “channels” for water coursing through the structures, according to Edward J. Cording, the chief engineering specialist retained by the MTA.

“Anything done to control the water is going to enhance the long-term structural capacity” of the tunnels, said Cording, a professor at the University of Illinois. “We’re trying to minimize the deleterious effects of ground water, both on the concrete lining and on its (rods of steel) reinforcement.”

The voids were supposed to have been filled with grout during construction.

Other problems have arisen at the cross passages, which link the twin tunnels and house pumping and electrical equipment. The passages have cracks and have experienced water leakage. Records show that concrete grout has been pumped to fill air voids, of up to 15 inches, found above the roofs of the cross passages.

On July 5, workers performing the repairs at a cross passage near Civic Center “discovered that the roof concrete was only 5 1/2 inches thick,” according to an inspection report. Specifications called for the roof to be built at least 12 inches thick.

The 2,033 tons of concrete-based grout used thus far to repair the subway is the equivalent of 104 loaded, full-sized cement trucks. That is enough grout to add a 1-inch coating to 1.1 miles of the entire 18-foot, inner diameter of the tunnels.

“They’ve certainly done a lot of work out there,” Cording said.

A parallel independent review undertaken for the MTA concluded early this year that the supervision of the original construction--provided by Parsons-Dillingham, the transit agency’s inspection management firm--fell short of “acceptable industry practice.” Parsons-Dillingham has helped inspect the recent repairs at no cost to the MTA and has agreed to pay the $1.4 million cost of the outside reviews.

Ultrasound tests conducted for Cording’s panel found that along one point of the tunnel wall, 460 feet, or 9% of the length of that tunnel, was thinner than the design-specified 12 inches of thickness, according to records.

Interviews and thousands of pages of public records also show that:

* The Cording panel did not test water coming into the tunnels within 600 feet--or the length of two football fields--of Union Station. It is in this area that past studies have found the highest concentrations of hydrogen sulfide, which can eat away concrete and its reinforcing steel.

Yet officials have emphasized that the water collected for the Cording panel’s review was not highly corrosive. “The level of hydrogen sulfide is very low, in terms of affecting the structure,” John M. Hanson, an engineer and one of Cording’s co-panelists, said in February.

In response to inquiries from The Times, Cording said last week that he had been unaware that water samples were not taken from areas where the highest concentrations of hydrogen sulfide would be expected.

“The intent is not to omit that first 600 feet (of tunnels leading south from Union Station), as far as I’m concerned,” Cording said, adding that he still hopes to collect samples from the area.

The concentrations of hydrogen sulfide are important because the subway tunnels were designed and built with a type of concrete that is more vulnerable to corrosion than the more costly material originally envisioned by transit officials.

Also eliminated from the design for cost reasons were water stops, devices intended to confine water that intrudes. Officials had altered the type of concrete and deleted the water stops based on their hope that the 1/8-inch-thick plastic liner would provide a barrier to both gas and water.

* The Cording panel did not study the potential performance of the tunnels at a Downtown location where other engineers have said it is more vulnerable to damage from a major earthquake. In the area, about 860 feet southwest of Union Station, the tunnels pass from firm soil into water-saturated, loose ground near Spring Street. The Cording panel also did not measure with ultrasound the tunnel concrete thickness through this area.

An engineering report prepared for Los Angeles transit officials in 1984 warned of the danger posed at this location and noted that the tunnel design did not address the matter.

“Some settlement of the soil is likely to occur (and) differential dynamic motions of soil and rock will develop during the earthquake,” said the report by Lindvall, Richter & Associates.

John F. Hall, a professor at Caltech who specializes in earthquake engineering, said recently that he agreed with the Lindvall Richter analysis. The Cording panel, he said, should examine the tunnels’ crossing of the contrasting soils.

“This is something that should have been looked at,” said Hall, who reviewed the earthquake projections compiled by the Cording panel. “I don’t think there’s any question of that.”

Cording said he believes the added work is unnecessary because the panel’s consultants examined how the tunnels would perform under a range of other earthquake scenarios.

“There is no explicit analysis of the contact between the two (soil) materials,” Cording said, but he added: “I think they looked at it (the tunnel’s overall seismic performance) on the conservative side.”

One of the consultants responsible for the recent examinations said that about 60% of the total length of the tunnels was tested for thickness with ultrasound. Cording said his intention had been to test with ultrasound any area of the tunnels where thin concrete or other anomalies were suspected.

* Officials have not decided how to address cracks observed at the connections between the tunnels and the electrical rooms.

Last February, Cording and his colleagues noted the potential for danger in the event of an earthquake:

“Under larger ground motions, it is possible that a several-inch-thick, possibly unreinforced part of the wall formed by the cracking at the connection between the cross passage and the tunnel could separate. It is recommended that procedures for limiting such a separation or other local damage at these junctions be investigated.”

In an interview last month, Cording said the MTA’s design engineers, headed by the firm of Parsons Brinckerhoff, had advised him that repairs were not necessary. But when asked more recently whether repairs are needed and if so, who would pay for them, Cording said:

“I’m not ready to really discuss that. I think it’s really a separate item as to whether (Tutor-Saliba) does that, or whether (the MTA) pays for that, or whether it’s not done.”

Tutor, when asked about the matter, said Friday: “We’re not doing any more work.”

Repairing the Subway

Numerous areas of the Downtown Los Angeles subway between Union Station and Pershing Square were built with concrete thinner than the design called for. Also, extensive air voids in the crowns of the tunnels have acted as channels for ground water that has penetrated the structures. After the problems with the thin concrete were disclosed in The Times last year, repairs were ordered. Here is a look at how the work has been done.

1) Tests showed that much of the concrete is thinner than the specified 18 inches in the crown and 12 inches in the walls.

2) To fill the gaps in the crown, grout was pumped through hoses and steel tubes from inside the tunnel.

3) Cavities were also found between the outside of the tunnel and the surrounding soil. They have been filled from within the tunnels, using longer pipes to pump the grout. More than 2,000 tons of grout has been used in the repairs.

Source: Metropolitan Transportation Authority