Just three years after the first segment of the Metro Red Line was opened at a cost of $1.45 billion, the Army Corps of Engineers says the subway’s concrete walls are at risk of being eaten away by chemical-laced ground water.

The Corps blamed “poor construction practices,” but MTA officials immediately disputed the findings, saying the report overstates the potential for damage and problems to the system.

“If all the planets and the sun and the stars line up, we may have to replace in a few spots,” said Stanley Phernambucq, the MTA’s top construction officer.

“If we saw a problem, we would have to cut it out and put new cement in and epoxy it,” said Phernambucq, who joined the MTA less than a year ago from the Corps. “But the chances of a problem are one in a billion.”

The portion of the subway affected by the ground-water intrusion is the first 4.4 miles built – stretching from Union Station to MacArthur Park.

Corps engineers said in the report that there “may be a safety and maintenance problem that develops after as few as two to five years.”

“If adequate inspection and maintenance are performed, no catastrophic failure is expected due to chemical deterioration,” the report states.

But there likely will be “increased costs for repairs if the groundwater that is clearly in contact with the structure contains . . . high concentrations of chloride and sulfate.”

In addition to potential deterioration of the concrete walls, the Army engineers said there was potential for corrosion of the concrete’s reinforcing steel, depending on how well the walls are shielded from the ground water.

The report warns that in a worst-case scenario, the structure – which was supposed to have been built to last a century – could need significant repairs in 15 years. The subway opened in early 1993.

The 16-page study was commissioned by the U.S. Department of Transportation after revelations about thin, leak-prone tunnel walls, sinking portions of Hollywood Boulevard and other construction glitches surfaced.

The report actually was completed in April 1995 – two months before tunneling opened a sinkhole along Hollywood Boulevard – but has been revised several times since then.

“When issues come up, we go out and get additional expertise. We felt we needed it,” said Lawrence Weintrob, deputy assistant inspector general at the U.S. Department of Transportation.

“It’s known (MTA) has had lots of problems,” Weintrob said.

Phernambucq disputed the findings of the report, which was written by his former colleagues at the Corps’ materials testing facilities in Vicksburg, Miss.

He acknowledged that the agency conducts daily inspections of the tunnel walls, but said it believes that problems cited in the report won’t occur because concentrations of sulfates in particular are only a fifth of the original estimates used in the Corps’ study.

How big a problem it is remains an unresolved technical question as well as a political one between the MTA and the Army Corps.

MTA Board Chairman Larry Zarian said the report was “theoretical” and was done without site visits, though all the report’s findings are based on MTA information and studies.

“We believe they (the walls) are safe, we believe they’re done right and we believe there’s no reason not to believe that,” Zarian said.

Zarian said the report also was criticized by Federal Transit Administration officials, who differ with their own department’s Inspector General’s Office, during a March 27 appearance before Congress.

The officials could not be reached for comment late Wednesday afternoon.

Los Angeles County Supervisor Michael D. Antonovich, a board member and longtime subway foe, said the report’s findings deserved investigation by a grand jury.

“It appears to have been major graft, or major stupidity, in this project to have these consequences,” Antonovich said. “The system needs major rehabilitation decades sooner than anticipated. It’s a balloon payment of all these costs after construction is completed.”

The report points to several problems that may combine to dramatically weaken the strength and durability of the walls in some areas:

A plastic polyethylene tunnel liner, supposed to be impermeable, has torn in many places, leading to numerous leaks.

Those leaks allow water that can be very acidic, containing compounds of sulfur and chlorine that degrade concrete and steel.

The degrading effects could be worsened by the use of concrete “on a number of occasions” that was watered down to keep it from drying out before it could be poured.

Such watered-down concrete is dramatically more vulnerable to decay from sulfates, and its steel reinforcements are much more likely to corrode from chlorides, according to the report.

“Because of poor construction practices that occurred in some of the construction, the structure must be inspected more frequently than had this not occurred, resulting in higher costs,” the report says.

Excessively watery concrete was used only in relatively few spots, Phernambucq said, thus minimizing the potential vulnerability problems.

“What they did is bean-counted,” Phernambucq said of the Army engineers. “There was a small amount of (concrete) loads that fell out of specifications. There was never a strength problem with the concrete. It just blew out of proportion.”

Army engineers and other federal officials knowledgeable about the report declined public comment Wednesday.

In heated meetings in Washington, D.C., recently, MTA officials vigorously contested the study’s conclusions.

Responding to the Army Corps of Engineers report, a consultant to the federal government wrote March 22 that the study’s conclusions were “based on several worst-case condit`ions occurring simultaneously.”

Philadelphia-based Urban Engineers Inc. said, for instance, very little chloride was present in water samples and that cracks detected in the wall were “normal” and repaired by injecting grout.

Army engineers focused on ground water laced with sulfates, which are sulfur compounds naturally occurring in some soils. Exposure of the concrete to the sulfates became a hot issue for MTA officials when the plastic liner protecting the tunnel walls was found to be torn in places.

Of the 16 samples Army engineers studied, 15 contained enough sulfate concentrations to register a “moderate” on the worst-case scale. The water apparently had seeped into the tunnels in greater amounts because of rainstorms.