Sonoma Valley to get roundabout at Highways 121 and 116 following state grant

A new traffic circle at the junction of Highways 121 and 116 south of the city of Sonoma is on track to reduce vehicle backups at the oft-congested intersection.|

A long-awaited solution to traffic snarls in the Sonoma Valley is coming in the form of a roundabout where Highways 121 and 116 meet, the result of a $19 million grant announced this week by state transportation officials.

The intersection currently served by a four-way stop with Bonneau Road has for a generation been a pinch point, as well as a source of frustration for local commuters and visitors to the city of Sonoma. Backups can stretch for miles on popular summer weekends, including when travelers from the greater Bay Area head to area wineries, Napa’s BottleRock music festival or an event at Sonoma Raceway.

“It’s a big nexus point, with people from Napa and Sonoma heading south to San Francisco and the broader Bay Area, and north to come visit Wine Country,” said Sonoma Mayor Logan Harvey. “I grew up in this community and that intersection has always been extremely difficult and traffic inducing. And it really doesn’t have to be.”

The California Transportation Commission agreed, approving at its Wednesday meeting the $19 million award funded by gas tax dollars through the State Highway Operation and Protection Program. Sonoma County’s transportation authority partnered with Caltrans and is chipping in another $5 million in sales tax revenues toward the estimated $24 million project to complete environmental review and design work, plus to make right-of-way acquisitions ahead of construction.

“The desire to have improvements at that intersection probably goes back two decades, if not more,” said Suzanne Smith, executive director of the county transportation agency. “It really is the gateway to Sonoma Valley for people coming in off Highway 37 or off of (Highway) 101, and … it’s just not a sufficient interchange by a lot.”

The project approval and environmental review were finished in spring 2018, setting up design of the roundabout and negotiating for adjacent property by 2022, when the state funding will be available. Construction is expected to begin in early 2023 and completed by the end of 2024.

“This project has been desperately needed for years and we were just waiting on funding coming forward,” said Supervisor Susan Gorin, who chairs the transportation authority and represents the Sonoma Valley. “The neighbors are excited about moving this forward and I am as well. We will get there, but we have to have patience a little while longer.”

The project and a portion of its cost was included in Measure M, the quarter-cent sales tax that voters passed in 2004. The local pot of transportation dollars has also gone to support and leverage outside grants for the Marin-Sonoma Narrows Highway 101 lane-widening project and repairs of the county’s roads, as well as funding for transit and bicycle and pedestrian pathways.

The transportation authority’s board of directors has been mulling early extension of the 20-year sales tax, because the measure’s last five years of revenues are already committed to other projects. The 12-member board represented by elected city and county officials will host a virtual meeting later this month to vote on advancing the renewal for the November ballot, but is expected to do so before making a final decision by August.

“This is why it’s so important to have a local tax measure for transportation,” Smith said. “There’s no way this project happens if we don’t do the preliminary work and partner with Caltrans to get the construction funds.”

The Sonoma Valley is already home to a roundabout, off Arnold Drive near the Hanna Boys Center, so residents are increasingly familiar with navigating the traffic flow device. The city’s mayor, who is also vice chair of the county transportation authority, said the transition should be relatively seamless once construction is finished after the two-year cycle.

“I’m excited for the project to be implemented and think there could be an adjustment period for people dealing with the roundabout,” Harvey said. “But I absolutely think it’s the right decision for that intersection and do believe it will improve traffic. I’m looking forward to driving it in the future.”

You can reach Staff Writer Kevin Fixler at 707-521-5336 or On Twitter @kfixler.

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