Rail bridge near Oceanside

Contractors are rebuilding parts of a new concrete railroad bridge over the Santa Margarita River on Camp Pendleton. (Don Bartletti / Los Angeles Times / May 1, 2013)

Sections of a new $40.6-million bridge near Oceanside that will serve one of the busiest rail corridors in the nation are being torn out and rebuilt due to flaws in the concrete.

Officials for the San Diego Assn. of Governments, which is funding the project, said the contractors are replacing about 500 feet of the 755-foot span over the Santa Margarita River and a nearby tidal marsh.

David Hicks, an association spokesman, said the work will cost about $3 million and delay the opening of the bridge by about a year. He added that the contractors have filed an insurance claim.

The new structure is being built adjacent to Interstate 5 in the southwest corner of the Camp Pendleton Marine Corps Base north of Oceanside.

Once completed in 2014, the span will replace an aging steel bridge that now handles about 70 freight and passenger trains a day from Amtrak, Metrolink, the Coaster and the Burlington Northern Santa Fe Railway Co.

The rail route links Los Angeles and San Diego and is the second busiest intercity line in the country. The construction is not interfering with current train traffic.

Hicks said the contractors decided to rebuild the bridge because tiny cracks spread through the superstructure after wooden braces that supported concrete molds fell down before the material had properly set.

The damage, Hicks said, might allow water to enter the concrete and degrade the structure, reducing its life span of 100 years. Builders suspect that marine worms bored into the wooden braces, weakening them.

Hicks said the bridge's piers and footings, which extend 220 feet below the river bottom, were unaffected and do not need to be replaced.

The project is being built by a joint venture that includes the Flatiron Construction Corp. and the Herzog Contracting Corp. 

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