A bridge collapse in Oakland, Calif. that collapsed part of a freeway bridge could happen to some bridges in Washington State.

The disaster happened when a gasoline tanker truck caught fire after hitting part of the bridge.

That fire was burned hot and long enough to weaken the steel girders that held it up.  Amazingly, no one was killed.

KING

The double-deck I-5 Ship Canal Bridge could be in danger of collapse if an intense fire were to burn on the lower deck.

The incident was not unlike a case in Tacoma in 2002 when a railroad tank car full of Denatured Alcohol caught fire under State Route 509, but the result was far different.  Even with more fuel burning, the steel rebar inside was covered by concrete.

"Essentially, the concrete covering that steel is an insulator," said Harvey Coffman, a bridge preservation engineer.

"It prevents the heat from getting to it."

The Washington State Department of transportation is responsible for 3,000 bridges statewide.  Eighty percent of them are concrete, but that still leaves 20 percent made from steel.

One bridge of concern for this type of fire is the dual level I-5 Ship Canal Bridge in Seattle.

A fire on the express lanes on the lower part of the bridge could potentially weaken steel that holds up the main upper deck.

"The location of the fire makes a difference," says state bridge engineer Jugesh Kapur. "If it's on top, it's probably less damaging than it is from the bottom.  The ship canal bridge, if you have a fire on the lower level, you could have extensive damage if it's not put out quickly."