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SR-29/SR-221 junction interchange - Alternative 1 (copy)

This is one proposed option for Soscol Junction that would create a Highway 29 overpass with a roundabout underneath.

Napa County wants to spend $20 million in toll bridge hike money in part to improve three consecutive, congested Highway 29 intersections—Carneros Junction, Soscol Junction and Airport Boulevard.

The county is guaranteed the money for south county Highway 29 projects from last June’s voter-approved Regional Measure 3. Bay Area voters agreed to raise tolls $3 in phases on state-owned toll bridges by 2025 in return for congestion-busting projects.

On Thursday, the Napa Valley Transportation Authority Board of Directors approved a Plan A to spend the $20 million, as well as a Plan B backup. Plan A addresses that traffic-tangling triplet.

“Carneros, Soscol Junction and Airport we view as a linked system,” said Danielle Schmitz of the NVTA. “To maximize congestion relief on that system, we have to have the projects go concurrently or in some sort of close, successive order.”

Carneros Junction is where Highway 29 heads north toward the city of Napa and Highway 12/121 heads west toward Sonoma, near Stanly Ranch and a hilly pasture with black-and-white Dutch-belted cows.

The signalized, three-way intersection could end up with a permanent green light for northbound Highway 29 traffic. The trick is handling Highway 12/121 traffic that would periodically make left turns in front of it. Merge lanes would be added to separate the traffic streams.

Similarly, southbound Highway 29 traffic turning right onto Highway 12/121 could also have a permanent green light, with more merge lanes to separate traffic streams.

Two miles east is Soscol Junction, the signalized highways 29 and 221 intersection. Rush-hour backups can leave drivers on the Butler Bridge looking at the Grape Crusher statue longer than they might wish.

The proposed solution involves building a Highway 29 overpass with no signals. Underneath would be either one or two Highway 221 roundabouts to serve as on and off ramps and to regulate traffic heading to Soscol Ferry Road.

A mile east is the signalized Highway 29/Highway 12/Airport Boulevard intersection. One feature here is big backups as traffic waits in left turn lanes on southbound Highway 29 to enter Highway 12 heading east toward Jameson Canyon and Fairfield.

The tentative idea is to extend the left-turn lanes on Highway 29 back toward Soscol Junction, making them longer. Another possibility is synchronizing the lights at Airport Boulevard and South Kelly Road.

Finally, the NVTA wants to make Highway 29 intersection and other improvements in American Canyon.

But the $20 million in toll hike money won’t cover these projects and it’s not even close. Soscol Junction could cost $40 million, Carneros Junction $3 million and Highway 29/Airport $3 million.

Plan A for the $20 million spends $2.6 million on Soscol Junction, $3 million apiece on the Carneros and Airport intersections and $11.4 million on American Canyon projects. This assumes the NVTA successfully competes for state and other funding sources to cover most of the Soscol Junction costs.

Otherwise, the NVTA would revert to Plan B. Soscol Junction would receive $17.6 million, Carneros Junction $1.4 million and the Airport Boulevard intersection $1 million, with American Canyon projects receiving nothing.

“I would say Soscol is the priority,” NVTA Board member and county Supervisor Alfredo Pedroza said.

The NVTA in coming months will seek enough outside money to move ahead with Plan A. NVTA Executive Director Kate Miller said a travel behavior study underway shows that Highway 29 serves regional traffic passing through the Airport intersection, Soscol Junction and Carneros Junction.

“I think that’s a strong argument to say this is just not isolated to Napa,” Miller said. “This a regional corridor and we really need support in getting it done.”

Napa County can also compete with Bay Area counties for other Regional Measure 3 money for mass transit and trails. Imola Avenue park-and-ride lot improvements, a Vine trail connection from South Kelly Road to Napa Pipe and American Canyon transit improvements on Highway 29 are among the NVTA’s priorities.

Regional Measure 3 provides $100 million for Highway 37 that links Interstate 80 in Solano County with Highway 101 in Marin County. Napa, Solano, Sonoma and Marin counties are seeking solutions for this two-lane, congested road that scientists say faces flooding from sea level rise.

Working with the three other counties, the NVTA proposes that $15 million go toward improving the Highway 37/Fairgrounds Drive area in Vallejo, $27 million toward near-term improvements on the highway and $58 million toward environmental documents and study for long-term improvements.

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Napa County Reporter

Barry Eberling covers Napa County government, transportation, the environment and general assignments. He has worked for the Napa Valley Register since fall 2014 and previously worked 27 years for the Daily Republic of Fairfield.