Crews Work to Shore Up Rail Tunnel : Fire: Engineers hope to reopen downtown section of the Hollywood Freeway by Monday. The blaze below is still smoldering.

As fire smoldered for a second day in an unfinished downtown Los Angeles subway, engineers struggled Saturday to shore up the gutted underground tunnel in hopes of reopening the Hollywood Freeway by Monday morning’s rush hour.

State engineers visually inspected the freeway above the burned-out Metro Rail tunnel and judged it to be structurally sound. The roadway--one of Los Angeles’ most heavily traveled arteries--was closed early Friday amid fears that the partially collapsed tunnel underneath it would cave in.

Officials cautioned that the freeway, part of U.S. 101, will not be reopened until workers finish building braces designed to prevent the tunnel from caving in further.

“We are trying very hard to see if we can open up the freeway by Monday morning,” said Steve Leung, traffic systems chief for Caltrans. A decision is not expected until tonight.

The separate, elevated El Monte busway that runs alongside the freeway will be opened to auto traffic on Monday, officials said.

Fire officials said Saturday that they have found no evidence of arson but are continuing to investigate what caused the fire to erupt in an uncompleted section of tunnel.

Sources said a crew may have been working with welding equipment several hours before the fire. Earlier this year, a small fire in the same tunnel complex was caused by sparks from welding, according to Metro Rail officials.

Saturday night, about 43 hours after the fire began, it continued to smolder in a 200-foot southern section of the tunnel. Firefighters decided to let the fire burn itself out.

When the northern end of the tunnel cooled down and was deemed safe to enter, repair work began beneath the freeway.

Enduring stifling heat, construction workers erected 12-foot sections of aluminum scaffolding to shore up a 250-foot portion of the charred tunnel. Wooden timbers and steel beams were added to hold the tunnel roof in place.

It was a painstakingly slow process. By Saturday night, only a short section of the tunnel had been shored up by a small crew that worked methodically. An ambulance and four rescuers waited nearby.

The construction is a temporary, emergency measure designed to strengthen the tunnel so it will withstand the weight of freeway traffic above, officials said.

“The entire tunnel will have to be reconstructed,” said Al Perdon, assistant general manager for the Southern California Rapid Transit District. “What we are building right now is a temporary structure to allow traffic to be restored to the freeway. . . . (The tunnel is) a big hole in the ground that has been burned out.”

Perdon said the enormous steel bands that encircle the tunnel were distorted and twisted by the heat, but retained their strength.

The section of tunnel beneath the freeway, he said, did not cave in because soil surrounding it had been injected with chemical grout that bonded the dirt. Grouting was not used along the section of tunnel that collapsed because it runs beneath a largely deserted maintenance yard, Perdon said.

Officials emphasized that the safety of construction crews and potential motorists would not be compromised. They added that they want to complete the repair work as quickly as possible.

“We’ve got to get this freeway open,” an engineer close to the project said. “That’s everybody’s major concern.”

The stretch of freeway that is closed, a segment known as “the slot” between Mission Street and the four-level interchange, averages 210,000 vehicles a day and is a principal link into the heart of downtown Los Angeles.

“We’re targeting for Monday, but we’re not going to push the workers,” Perdon said. “Our first concern is safety. . . . If we can open the freeway Monday, we will. If we can’t, then we won’t.”

Dave Roper, deputy director of Caltrans, said that if the freeway is not reopened on Monday, the elevated, single-lane busway will be used for all traffic, buses and cars.

Fire officials, discounting speculation that the blaze was started by transients, said in a news conference Saturday that investigators have not found evidence of arson. They said the investigation is continuing.

“Nothing that we have right now would lead us to believe that it’s an arson fire,” city Deputy Fire Chief Reynaldo Rojo said. “It’s very slow. . . . Arson work is detective work.”

No one was working in the tunnel when the fire erupted about 1:50 a.m. Friday, officials said. A crew in an adjacent tunnel discovered the fire and escaped unharmed.

In addition to interviewing that crew, investigators said they plan to talk with members of another crew that had been working earlier in the tunnel that burned. This crew had finished its shift hours before the fire erupted.

Sources told The Times that the crew may have been working with welders while installing a plastic lining used to keep toxic fumes out of the tunnel.

Earlier this year, a small fire in the same tunnel complex was caused by sparks from welding, according to Metro Rail officials.

Dan Ford, the Metro Rail’s senior engineer for construction safety, said on Friday that a “very small fire” earlier this year in the same tunnel complex was started “as a result of a welding operation.”

In that case, he said, the embers smoldered for awhile before bursting into flames, even though workers had followed proper safety procedures and washed the welded area with water to extinguish any sparks after they finished work.

But, he said, “there was no operation during the day (Thursday) that could account for this fire.”

Other sources said that workers who finished their shift late Thursday afternoon had been installing the plastic liner that blocks gases and moisture from entering the tunnel. As part of that work, the sources said, some welding does occur.

Fire and Metro Rail officials said there was no indication of what caused the fire, whether it was welding or some other source.

“I’ve got a team working on this asking all these questions,” said Neil Peterson, executive director of the Los Angeles County Transportation Commission. LACTC took over management of Metro Rail from the RTD last week.

The fire represented the most serious setback to construction of the $1.4-billion, 4.4-mile Metro Rail subway system, a project already months behind schedule and millions of dollars over budget. But officials downplayed any effect the damage to the tunnel would have on the start-up date of the subway system.

The tunnel that burned will not be for passenger traffic, but will be used to carry empty trains between Union Station and a maintenance yard beside the Los Angeles River.

The smoke that billowed from the tunnel was moderately toxic. Scientists at the Air Quality Management District who monitored it said the levels of chromium and arsenic late Friday reached 20 times the safety exposure levels prescribed by the federal Occupational Safety and Health Administration.

Since then, the levels have droped off to well below permitted levels, said AQMD spokesman Tom Eichorn.

At the height of the fire early Friday, flames had engulfed nearly 750 feet of the tunnel, which runs from Union Station, under the Hollywood Freeway and to a maintenance yard at the intersection of Center and Commercial streets. Several hours into the fire, a middle portion of the tunnel, about 150 feet long, caved in, dividing the tunnel into northern and southern sections.

Fire in the northern section was extinguished Friday afternoon. Fire continued to smolder at the southern end of the tunnel Saturday evening. Smoke floated out of the blackened tunnel’s portals, and twisted metal was visible.

“Technically it’s out, but it’s still smoldering,” Battalion Chief Tom Curry said as he surveyed the site. “There are little pockets of fire down in there.”

Firefighters worked to pump out chocolate-colored water. But they did not venture inside the tunnel, in part out of fear that the burning sections might yet collapse. Instead, they kept vigil outside the southern mouth of the tunnel to prevent the fire from spreading.

Deputy Fire Chief Rojo said the fire, limited mostly to heavy, slow-burning timbers that line the tunnel, would burn itself out. “There is no reason for us to risk anyone’s life,” he said.

Times staff writer Tracy Wood contributed to this story.

Repairing The Tunnel Temporary repairs to shore up 250 feet of the Metro Rail tunnel under the Hollywood Freeway. 1. The damage The fire destroyed the wood timbers between the steel ribs. The wood is completely gone. The goal of the repair effort now under way is to shore up the tunnel to prevent future collapse. 2. Temporary repairs In the center of the tunnel, a 12 foot by 12 foot aluminum brace (with diagonal cross bracing) will be installed every 1.5 feet down the tunnel. Steel beams will be placed on top of the aluminum braces. And large wood timbers will be installed above that to hold the dirt lining of the tunnel in place. Steel ribs and timber lagging, installed in four-foot sections, support the circumference of the tunnel. 12-inch-thick concrete liners are used as the finished construction surface. A 1/8-inch-thick, high-density polyethylene plastic liner is used on the inside walls to protect against methane gas seepage Section of Metro Rail tunnel currently being repaired to allow reopening of Hollywood Freeway (101) Section of tunnel that collapsed Source: Southern California Rapid Transit District