SR-12 - Hooker Creek and Sonoma Creek Replacement Project

Caltrans will replace two bridges on State Route 12 in Sonoma County during a $13 million, three-year project scheduled to begin in the spring or summer of 2022.  

The Hooker Creek Bridge near Agua Caliente and the Sonoma Creek Bridge near Kenwood (not to be confused with a bridge of the same name on Route 37) were built in 1900 and 1922. Decades of rapidly flowing water during rainy winters have eroded the foundations and compromised the bridges' strength. 

Caltrans will first replace the Hooker Creek Bridge before beginning the replacement of the Sonoma Creek Bridge. 

Highway 12 spans both bridges as a two-lane road – one lane in each direction. During some phases of the project, Caltrans will conduct one-way traffic control or detour motorists around the construction site via nearby streets. 

 

Bridge Scour is the Problem

During winter rainstorms, Sonoma and Hooker creeks swell with run-off.  The tranquil waterways of summer and fall can morph into a winter torrent. In a process known as scouring, fast-flowing water strikes bridge columns or abutments, swirling rapidly around the fixed object, creating a vortex that erodes the creek bed and undermines the bridge. 

Over the years, the effects of scouring accumulate, weakening the bridge from the bottom upwards. Caltrans considered strengthening the bridges in place, but studies revealed more structural damage than was visible during onsite inspections, leading Caltrans to decide upon replacing the bridges as a better long-term and cost-efficient solution.

 

Hooker Creek Bridge

Hooker Creek Bridge is located at post mile 33.3 between Cavedale Road and Rancho Bonita Way. 

The bridge has not been improved much since being built 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 19th Century concrete arch structure about 24-feet in length.  

Caltrans will detour traffic around the bridge over city streets for about 30 consecutive days in 2022 to accommodate construction. The new bridge will take about a year-and-a-half to build, from spring/summer 2022 through fall/winter 2024.  

 

Sonoma Creek Bridge 

The Sonoma Creek Bridge lies at post mile 25.8 between Adobe Canyon Road and Hof Road. The bridge was built in 1922 and widening in 1950 and 1962. Like the Hooker Creek Bridge, the rebuild project will take about one-and-a-half years, starting in mid-to-late 2023.  

Caltrans wishes to minimize traffic disruption by completing most if not all of the Hooker Creek Bridge replacement before commencing construction on the Sonoma Creek Bridge. 

During a period of about 45 consecutive days, Caltrans will conduct one-way traffic control through the construction zone. 

      Hooker Creek Bridge, a stone arch bridge built in 1900

 

Further Details from the Environmental Report:

At the Sonoma Creek Bridge, the project would remove the existing 46-ft wide bridge, and replace it with a 51-ft wide precast/prestressed type structure. The new structure would be 63 ft long, replacing the existing bridge of the same length.

 At the Hooker Creek Bridge location, the project would remove the existing 36-ft wide bridge and replace it with a 45-ft wide PC/PS slab-type structure. The new structure would be 40 ft long, replacing the existing 24-ft long bridge.

 

                                              Sonoma Creek Bridge