The Highway 101 interchange at Old Redwood Highway in norther Petaluma, completed earlier this year, was named last week as one of the North Bay’s top infrastructure projects of the year.
Caltrans awarded a bid to Ghilotti Construction Company to replace the two-land overcrossing at Highway 101 and Petaluma Hill Road, built in 1958, with a four-lane bridge that includes Americans With Disabilities Act–compliant pedestrian walkways and bicycle paths in both directions.
The new structure is higher and wider to accommodate today’s standard road shoulders and clearances, allowing for safer vehicle passage while also providing additional space for oversized trucks.
“It’s no easy task to replace an existing bridge as vehicles continue to use it,” said Dick Ghilotti, president. “We first built the southern section of the new overcrossing and switched traffic to the new portion. During this process, the former structure was demolished piece by piece so new sections could be built.”
The project included constructing new two-land north and southbound on- and offramps built 57 years ago, making it easier for merging traffic to enter and exit the highway. New sound walls were also built, and drought-tolerant plants were added to landscape areas near the bridge, access roads and ramps.
“This project not only helps to improve transportation in the North Bay, it also enhances the safety, mobility and livability for residents of Sonoma County,” said Caltrans Director Malcolm Dougherty.
The $41 million construction cost was paid with $4.6 million from Proposition 1B, the statewide transportation bond passed in 2006. Another $19.8 million came from Measure M funds, passed in 2004, along with $16.5 million in city of Petaluma funds. The project began with a groundbreaking ceremony on April 25, 2013. Work was completed by July 31, 2015.
“The Highway 101 corridor is our highest priority, and the completion of the Old Redwood Highway interchange project gets us closer to achieving our overall goal of completing three lanes in both directions all the way to the (Marin) county line,” according to David Rabbitt, Sonoma County supervisor and Sonoma County Transportation Authority director.
In addition, 18,600 square feet of stabilized earth retaining walls were constructed at seven different places around the interchange. A total of 164 concrete piles were driven deep in the earth for the new overcrossing, and 20 each of 120- to 130-foot-wide flanged, prestressed concrete girders were used. During construction, 3,430 cubic yards of structural concrete were poured into forms. At the same time, 4,000 linear feet of storm drain had to be trenched, laid and backfilled.
“It was ambitious,” said Caltrans District 4 Director Bijan Sartipi. “We built a new interchange in the same footprint as the old one, while still keeping the facility open to the public. There were many challenges along the way that had to be overcome, but now the community is benefiting from the new transportation options available for motorists, cyclists, and pedestrians.”