The $2.2-million fire that gutted an unfinished section of Metro Rail subway tunnel two months ago probably was an industrial accident caused by a metal-cutting torch, the Los Angeles County Transportation Commission reported Wednesday.
The blaze that destroyed a 750-foot stretch of tunnel beneath the Hollywood Freeway July 13 was the third such fire in the same tunnel complex within 24 hours, said the report by a team of independent investigators. The other two fires were quickly extinguished.
The 70-page report concluded that a cutting torch probably scorched wooden timber lining the tunnel, and the wooden support smoldered for hours before bursting into flame and igniting a plastic lining in the tunnel.
The report was commissioned by the Rail Construction Corp., a subsidiary of the transportation board, which took control of the project in July. A city Fire Department investigation into the cause of the fire is continuing. Officials say they expect to release a report on the official cause of the fire in four to six weeks and declined to comment on what it will say.
Chief Davis Parsons said the conclusions of the county's independent investigators were "a plausible scenario, not necessarily something that couldn't happen."
Ed McSpedon, president of the county's rail corporation, said: "It is the professional opinion of the independent investigation team that the most probable cause was accidental and resulted from the use of a cutting torch."
He said that the torch is routinely used to smooth sharp edges on steel tunnel supports before a plastic lining is installed. The steel must be smooth so that the lining, which keeps gases such as methane from entering the tunnels, will not be punctured. The plastic then is covered with cement, making the finished product fireproof.
However, the report concluded that flammable wooden timbers and plastic liners were fire hazards and recommended that safer construction methods be used in the future.
McSpedon said that future construction on the $3-billion subway system linking downtown to the San Fernando Valley will use non-flammable, precast concrete instead of wooden supports on the inside of the tunnels.
The fire probably started in the timbers when a cutting torch flame or hot metal lodged in the wood, the report said. Then the plastic liner was placed over the timbers, concealing the embers. The fire could have smoldered for as much as 12 hours before bursting into the main tunnel about 1:40 a.m., long after workers had left for the day. Workers in an adjacent tunnel discovered the blaze. No one was injured.
Eric Carlin, project manager for the contractor Tutor-Saliba-Perini, said of the scenario described in the county's report, "It's possible, it's possible."
"It would have had to smolder for six or seven hours, which is an awfully long time," Carlin said, adding that he wanted to wait until the Fire Department has concluded its investigation before commenting more fully.
"The Fire Department is more qualified to investigate fires," he said.
A spokesman for the Southern California Rapid Transit District--which had responsibility for the subway construction until the week of the fire--said RTD officials wanted to review the independent report before commenting.
The report noted that four similar fires occurred in the same tunnel segment near Union Station, two of them in an adjacent tunnel within 24 hours of the destructive blaze.
A fifth fire in the tunnel broke out one week after the July 13 fire while workers were making repairs. All of the fires involved timbers and plastic liner.
The July fire broke out in a service tunnel under construction near Union Station as part of the first 4.4-mile segment of the subway system that ultimately will stretch for 17 miles. The first leg, from Union Station to the intersection of Wilshire Boulevard and Alvarado Street, is scheduled to open in January, 1994.
McSpedon said the independent investigation findings were released in advance of the Fire Department's official report because bidding is about to begin on the second stage of construction. He said he wanted to incorporate new fire safety specifications into the new bids.
The Metro Rail subway already is $135 million over budget and at least 18 months behind schedule. Any delay in beginning new construction could force the project even further behind schedule.
Among the recommendations of the independent investigators, which already have been implemented, was a requirement for a fire watch, 24 hours a day, at all construction sites.
At the time of the fire, according to the report, there was "no evidence" that the contractor was maintaining fire watches.
The report cited a profusion of sometimes overlapping or confusing safety regulations, including apparently conflicting fire-watch regulations. McSpedon said safety manuals will be overhauled to clearly define requirements and lines of responsibility.
Times staff writer Tracy Wilkinson contributed to this story.
How Metro Tunnel Fire Started An independent investigation by the Los Angeles County Transportation Commission says that a cutting torch accident was the most probable cause of a $2.2-million fire in an incomplete Metro Rail subway tunnel two months ago. Following is a likely sequence of events as described in the report. 1. A worker using an oxy-acetylene cutting torch works on the wall of the tunnel. 2. The initial hot spot develops in timber rails htat reinforce the tunnel structure. 3. Hot spot smolders undetected as membrance is added to tunnel wall. Hours later it burns through membranne and ignites as it mixes with combustible gases inside the tunnel. 4. Flames flash across the ceiling of the tunnel, enveloping the structure. Source: Southern California Rapid Transit District