SAN DIEGO -- Construction was scheduled to begin Wednesday to replace the nearly 70-year-old Trestles Bridge near San Onofre State Beach along the border of Orange and San Diego counties.

The $12 million project is expected to be completed in early 2012, according to the San Diego Association of Governments.

"Like most people who use this beautiful beach, we will be sad to see the wooden trestles taken down," said Gary Gallegos, executive director of SANDAG. "But decades of use, vandalism, salt air and fires have worn down the bridge, and it has reached the end of its useful life."

The project calls for the removal of the northernmost segment of the wood trestle bridge and a reinforced concrete structure installed in its place, according to SANDAG.

SANDAG officials said the project is intended to improve safety and reliability on the nation's second-busiest rail corridor.

The iconic Trestles Bridge, which was built in 1941, is known for much more than accommodating rail traffic between Los Angeles and San Diego. It also inspired the name of one of Southern California's preeminent surfing spot, Trestles, which is located just offshore in front of the crossing.

Access to the beach will be maintained during the project, according to SANDAG.

The project was financed through federal economic stimulus funds and will create about 150 jobs, according to SANDAG.