Math was wrong in bridge accident

TACOMA — A ship carrying deck sections for the new Tacoma Narrows bridge hit the old bridge last week because engineers miscalculated the height of the underside of the old bridge, the state's project manager says.

The ship had 16 deck sections stacked 135 feet above the water level. The bridge builders thought it would glide under the sidespan of the old bridge with 36 feet to spare. But temporary scaffolding on top of the deck sections hit the underside of the bridge and toppled over Friday.

No one was hurt, and there was no damage to the existing bridge, said Linea Laird, project manager for the state Department of Transportation.

Laird said that because the elevation error was used in all calculations for the complex 4 ½-month deck-lifting process, everything has to be rethought, from the timing of lifts to the length of anchor chains used to keep the ship in position.

"A lot of things have to be reconsidered and re-evaluated," she said. "There's no sense in being shortsighted at this point. The important thing is to get it right."

Laird said she does not expect the setback to further delay the $849 million bridge project, which already is three months behind schedule.

In May, the bridge builders told the state the opening would be delayed until at least July 2007.

When the new bridge opens, all traffic will be shifted temporarily to the new bridge so retrofitting work can begin on the existing 1950 span.