Subway Tunnel Repair Bill May Rise Sharply

Metropolitan Transportation Authority board members this week allocated $2.5 million to shore up nearly half a mile of a subway tunnel under the Santa Monica Mountains--the first payment on a repair bill that could dramatically increase, according to documents recently released by the agency.

It was the first indication of the cost of an embarrassing construction mishap in which parts of the tunnel shrank four to six inches in a tricky section of soft shale, trapping a giant digging machine about 220 feet below homes in the Cahuenga Pass.

The cost could more than double if the MTA accepts an analysis commissioned by the excavation contractor that concluded that the area’s rock was up to 10 times weaker than the agency’s engineering consultants had told miners to expect.

The analysis, by highly regarded geologist Ronald E. Heuer of Illinois, found that while the MTA contract called for rock in the area to have a compressive strength of at least 1,000 pounds per square inch, it actually appeared to have a strength of only 100 to 300 pounds per square inch.

“These materials are more like ‘soil,’ rather than ‘rock,’ ” he wrote in his report. He added: “In my judgment, the tunnel driven to date could not be adequately supported” by methods specified in MTA contract documents.

*

Although there were minor cave-ins almost daily in June, according to Metro Rail records, digging did not halt until July 8 after miners discovered that expanding ground had severely buckled five of the 4-inch-wide metal ribs supporting the excavation.

Indiana-based contractor Traylor Bros./Frontier-Kemper ultimately was forced to replace 44 of the support ribs with stronger, 6-inch-wide ribs, according to records. To keep the tunnel safe, records show that the contractor had to spray thousands of cubic yards of costly fiber-enhanced concrete onto the walls and roof.

Traylor Bros. was also instructed to take the extra precaution of strengthening the tunnel’s walls by drilling dozens of staple-like metal dowels into them, the records show.

*

In many places, miners have also doubled the number of ribs supporting the excavation--installing the metal beams every two feet rather than every four feet as called for in the tunnel’s design specifications.

Documents released with the appropriation last week indicate that the repairs were not limited to a 180-foot section of the tunnel, as announced by officials during the summer, but instead will cover 2,450 feet.

Metro Rail officials said they have not yet completed an investigation into the cause of the problem. If the contractor is found to have caused the mishap by failing to support the tunnel properly, it will be ordered to pay and will be responsible for the $2.5 million allocated so far just for materials.

If MTA engineering is found to have been at fault, then taxpayers will have to foot the bill. In addition to the $2.5 million, the MTA would then have to pay the contractor for costs associated with delay.

Industry experts peg the amount at $40,000 a day over a minimum of six weeks. Also, agency documents say the MTA would have to pay the contractor for repairs and modifications to its tunnel-boring machine.