photo credit: Caltrans

 A portion of state Highway 12 will be closed for a month beginning Tuesday while crews demolish and rebuild a bridge in Sonoma County.

As part of the Sonoma and Hooker Creek bridge replacement project, Highway 12 between Madrone Road and Agua Caliente Road will be closed to take down and the rebuild Hooker Creek Bridge.

The bridge is located northwest of the city of Sonoma. Caltrans estimates that the project will take 30 days.

Through traffic will be diverted around the closed bridge via Madrone Road, Arnold Drive, and Agua Caliente Road, Caltrans said. Local traffic will be permitted as far as the closed bridge.

According to Caltrans, the Hooker Creek Bridge is made of concrete and is too brittle to be demolished in stages; therefore it is not safe to keep it open as crews take it down, unlike the Sonoma Creek Bridge, which is made of steel and strong enough to accommodate one lane of open traffic during construction.

Both bridges are victims of "scour," a process where fast-flowing water whirlpools around the bridge columns and erodes the creek bed. Over the years, the bridge's structural integrity can be strained enough that replacing it entirely is the best solution, the agency said.