Tunnel Troubles

First portion of the subway, Segment 1, is open. The recent problems have occurred in Segment 2; federal funding for Segment 3 is in jeopardy.

A chronology of mounting problems with construction and management of the multibillion-dollar Los Angeles subway project:

1993

* Aug. 29: The Times reports that numerous areas of the subway between Union Station and Pershing Square were built with concrete walls thinner than specified.

* Aug. 30: The federal Transportation Department begins its study of the problem.

* Sept. 2: Transit officials discover that fewer than half of the ordered repairs of tunnel’s construction defects have been done. They also fire from the project a top construction management official.

* Sept. 3: U.S. expands a yearlong FBI investigation, naming U.S. attorney’s office to oversee probe of construction deficiencies.

* Sept. 15: MTA officials delay awarding of $45-million contract to build Vermont-Beverly station until tunnel’s structural soundness is verified.

* Sept. 22: MTA appoints panel of three specialists to assess the safety and durability of tunnels.

* Oct. 16: Water leakage caused millions of dollars in damage to the subway because a costly protective liner was poorly designed, installed and inspected, according to an MTA consultant’s report obtained by The Times.

* Nov. 15: Mistakes and problems add about $200 million to subway costs, Times reports.

* Nov. 16: Auditors say Tutor-Saliba, the biggest subway contractor in Los Angeles, has inflated expenses, according to a Times article.

* Nov. 17: Transit commissioners award two major contracts for $28.2 million and $44.9 million to contractor, Tutor-Saliba, pending a review of the contractor’s work on twin tunnels already completed.

* Dec. 21: Transit officials announce that 11% of subway tunnels have concrete that is thinner than the design specifications of 12 inches, but are confident that tunnels are structurally sound because of extra rods of reinforcing steel.

1994

* Feb. 23: Independent tunnel panel reports that it found lax enforcement of construction requirements, along with previously undiscovered areas of thin concrete, air pockets and missing reinforcing steel in the tunnel wall. But it says tunnels are safe.

* March 15: MTA halts tunnel work after a locomotive accident injures three workers.

* April 13: Transit officials acknowledge that nearly one-third of the subway tunnels under construction Downtown are misaligned and that some segments will need to be re-excavated.

* May 23: Methane and hydrogen sulfide gases are regularly entering the subway, The Times reports. The subway was built with the sensors inside the exhaust ducts, instead of inside the stations at the passenger platform level, as a committee of safety experts recommended.

* July 18: State launches safety probe after three workers are injured in a welding-related explosion beneath Vermont Avenue and 6th Street.

* Aug. 11: State and federal occupational safety officials issue citations for 80 alleged workplace hazards during Metro Rail construction.

* Aug. 18: Tunneling beneath Hollywood Boulevard is shut down after street buckles and sinks along nine blocks.

* Sept. 11: The Times reports that transit officials waited six months before ordering the contractor to stabilize the ground with grout, in order to save money.

* Sept. 21: MTA chief hires a Caltrans executive to review troubled Rail Construction Corp.

* Sept. 26: Inferior materials--wood wedges instead of steel struts--were used for the bracing of subway tunnels, The Times reports.

* Oct. 3: An outside analysis commissioned by the Los Angeles City Council criticizes construction and says tunneling contractor used inadequate tunneling procedures, including the failure to grout properly.

* Oct. 4: MTA executives issue a scathing condemnation of tunnel work from Hollywood to the Wilshire district.

* Oct. 5: The Federal Transportation Administration announces that federal funding for the Los Angeles subway will be withheld until all questions regarding the mounting problems with construction and management project are resolved.