LOCAL

5 Freeway tunnel reopens, evidence of inferno is erased

Disasters and AccidentsBuilding MaterialCalifornia Department of TransportationStarbucks Corp.

Tony Brake had seen tunnel fires before, and given the tower of black smoke and what he could see of the flames, he feared this one was going to be bad.

On a Saturday morning in July, a tanker truck carrying 8,700 gallons of gasoline flipped over, and the two-lane underpass connecting the northbound Glendale Freeway with the northbound 5 Freeway turned into a blast furnace.

If the tunnel — which supports the 5 Freeway — were to fail, the freeway would collapse. Traffic would be snarled for months, and for a region just emerging from a recession, the economic impact could be severe.

Brake, a senior bridge engineer for Caltrans, remembers walking through the tunnel two days after the fire. It looked as if it had been bombed. Crews had erected a bulwark running its length to support the ceiling, and the scorched walls were brittle and crumbling. A skeleton of rebar was laid bare.

At Friday's reopening of the tunnel, Brake stood amid a crowd of close to 50 fluorescently clad engineers, contractors and maintenance personnel, as politicians stood at a lectern and raised their voices against the freeway drone to praise the work.

"In California, we know how to make things happen when we need to," said City Councilman Mitch O'Farrell.

At about 10:30, an armada of Caltrans vehicles slowly traversed the tunnel and saw — nothing. All evidence of the inferno and the work that has defined Brake's life for the last six months had been erased.

Drivers too will notice little more than shiny guard rails, a new roadbed and signage, more than 200 LED lights and a coat of white paint that just might resist the efforts of local tagging crews.

For Brake, indifference is a sign of a success.

"After the work is done, no one really knows what we did," he says. "But that's OK. What is important is that we prevented a tunnel from collapsing, no one was hurt, the repairs were made, and we are able to move on."

Soon after Brake's initial walk-through, crews began searching deep into the walls for patches of concrete no longer able to hold up the freeway overhead.

Drills bit into the walls and ceiling, extracting up to 100 concrete samples, a process akin to taking a medical biopsy. The samples were injected with dyes that highlighted microscopic cracks, and they were placed in vises that compressed them to the shattering point.

Cameras snaked into small bore holes. A radar system analyzed swaths of the walls and the ceiling, and sensors recorded the sound waves of hammers struck against the surface of the tunnel.

When the results came in, Brake was relieved. The damage was not as bad as he had feared. Most troublesome were a series of outrigger beams on the north side of the tunnel. The beams had cooked in the fire, Brake thought, like chicken in a rotisserie.

Brake and two colleagues drafted a set of blueprints that specified the repairs. The design included 13 pages of structural work, one of the most complicated reconstructions that Brake had overseen.

By mid-November, demolition started on the compromised concrete.

Wearing a hard hat, yellow rain slicker and rain boots, with a blue bandanna over his face, Lance Higgins stood at a control panel of an ungainly, four-wheeled contraption with an articulating arm angled high against the side of the tunnel.

A machine, a Conjet Robot 363, "delivers 32 gallons a minute through a nozzle the size of a Starbucks' stir stick," Higgins said.

With the push of a button, the water pressure — about 18,000 pounds per square inch — tore at the brittle concrete, stripping off four inches and further exposing the rebar. Occasional rocks shot across the tunnel like bullets. Loud pops signaled the displacement of larger chunks.

The wall soon looked like a cliff at low tide, its mottled surface of aggregate dripping wet. A soggy rubble littered the roadbed.

Two weeks later, scaffolding rose against the east side of the tunnel. Men in jumpsuits, hard hats and ventilators moved along its three tiers.

One hefted a heavy rubber hose. Another directed a mist of concrete — a special mixture known as shotcrete — from the nozzle onto the wall. After a couple of passes, he had laid down a 4-inch-thick layer of concrete over the rebar.

Others followed with 4-foot-long screeds, drawing S's on the wall as they smoothed out an application of concrete.

Brake picked up a handful of the sticky gray paste. He pulled out small fibers, like hairs, that had been mixed in with the cement. "It reminds me of the straw that was placed in the mud bricks of ancient Egypt," he said.

The fiber, made of polypropylene, strengthens the concrete.

On the opposite wall, the concrete was smooth and moist like the surface of a swimming pool.

A week before the opening, crews wrapped the damaged outrigger beams with a carbon fiber fabric. Applied like fiberglass, the material was slathered with an epoxy resin that dried to the hardness of steel.

Caltrans is still calculating the costs, which Brake estimates will come to $9 million. The agency expects to be reimbursed by the Federal Highway Administration Emergency Relief Program.

According to Caltrans spokesman Patrick Chandler, the agency will also try to recover its expenses from "the responsible parties." In 2007, after a fire caused $11 million in damage to the truck bypass tunnel of the 5 Freeway near the 14 Freeway, the state recovered approximately $3 million.

As for the cause of the more recent accident, the California Highway Patrol conducted the investigation. According to the accident report, a subcontractor for G&G Transport started driving the tanker truck at 2 a.m., delivering fuel to a vendor in Ventura shortly before dawn, then returning to Gardena to reload.

The driver was headed to a Costco in Burbank, mapping his route with a GPS. He arrived in the tunnel at 10:35 a.m. when, according to the accident report, he heard an explosion "like a tire rupturing." Uninjured, he walked away from the scene.

The CHP will not release details about the accident other than stating that for undetermined reasons the driver made "an unsafe turning movement on the freeway." A CHP spokeswoman said the portion of the accident report that specifies cause is shielded from the public because it is the opinion of the investigating officer.

Brake is curious, however.

"I never got the full story, and I wish I had," he said. "Could there be something in the tunnel design that contributed to this accident, something that should be addressed? Is it a problem for this tunnel or is it something we should consider in other tunnels as well?"

The information could be useful as he looks ahead to his next project. In March he has to deliver plans for a renovation of three connector tunnels on the 210 Freeway in west Pasadena. By the end of the year, they too will be made over with new LED lights and white paint that just might resist the efforts of local tagging crews.

thomas.curwen@latimes.com

Copyright © 2014, Los Angeles Times
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