30-Day Closure Of Highway 12 Begins In Sonoma County

SONOMA COUNTY, CA — As part of the Sonoma and Hooker Creek bridge replacement project, Caltrans was slated to close a section of Highway 12 between Madrone Road and Agua Caliente Road starting Tuesday, Sept. 5, and continuing for up to 30 days.

During this time, the Hooker Creek Bridge will be demolished and rebuilt. The bridge is located northwest of the city of Sonoma in the "Springs" area of Sonoma County, named for Agua Caliente, Fetter Hots Springs and Boise Hot Springs.

Local traffic will be allowed to go as far as the closed bridge, while through traffic will be detoured around the closed bridge via Madrone Road, Arnold Drive and Agua Caliente Road.

Unlike the Sonoma Creek Bridge, a steel bridge strong and flexible enough to accommodate at least one lane of traffic during its replacement, the Hooker Creek Bridge is composed of concrete and is too brittle to be demolished in stages — thus it cannot accommodate traffic during its replacement, according to Caltrans.

Bridge Scour

Both the Sonoma Creek and Hooker Creek bridges were victims of bridge scour, a process where fast-flowing water whirlpools around the bridge columns, eroding the creek bed that supports the bridge footings and columns. The structural integrity of such bridges can, over the years, become strained to the point where replacement is the best solution.

In the case of the Hooker Creek Bridge — at post mile 33.3 between Cavedale Road and Rancho Bonita Way — the bridge has seen minimal improvements since its opening in 1900. Only guardrail and new pavement have been added over the years. Except for the yellow and black-striped paddle signs, most motorists would have little idea they were traveling over a bridge. The creek itself is often invisible, shrouded by the canopy of nearby trees. Nevertheless, Hooker Creek is an attractive, if humble bridge, a turn-of-the-20th Century concrete arch structure about 24 feet long.

Hooker Creek Bridge location on Highway 12:

During the construction period of up to 30 consecutive days, Caltrans will remove the existing 36-foot-wide Hooker Creek bridge and replace it with a 44-foot-wide precast/pre-stressed slab-type structure. The new structure will be 41.5 feet long — replacing the existing 24-foot-long bridge.

On Highway 12 near Kenwood, nighttime lane closures are expected to continue at Sonoma Creek Bridge until the remaining section of the bridge replacement is completed.

Visit the Caltrans webpage for the State Route 12 Hooker Creek and Sonoma Creek Replacement Project for more information.