The California Transportation Commission has unanimously approved $73 million in funding for a Caltrans project that aims to decongest Highway 37.

The commission voted on the allocation on Thursday afternoon in Sacramento. The funding is based on gas tax revenues collected as part of Senate Bill 1.

Marin County Supervisor Stephanie Moulton-Peters urged commissioners to approve the grant, saying commuters lose up to 90 minutes a day in slow traffic on the route between Marin and Solano counties.

“This corridor is essential for North Bay workers and families, including two of my own staff and several county department heads and many workers at the county,” she said.

The grant will support the $251 million phase 2 of a three-phase, $500 million project to renovate the highway. The state plans to widen a 10-mile segment from Sears Point to Mare Island to improve traffic flow.

The second phase of the project involves installing a tolled eastbound lane, widening the Sonoma Creek Bridge and raising the road in areas of frequent flooding.

Caltrans previously secured $153 million for phase 2, according to Bart Ney, an agency spokesperson.

The first phase of the project involves replacing the Tolay Creek Bridge, east of the Highway 37 and Highway 121 interchange, and extending an eastbound merge lane for a mile.

The funding approved Thursday is part of a package for the state’s Trade Corridor Enhancement Program. The commission also approved a total of $810 million in grants for 23 other transportation projects, including $80 million for a Highway 156 interchange in Monterey County and $62 million for widening a 5-mile segment of Highway 99 in Tulare County.

Beverley Newman-Burckhard, associate deputy director of the commission, said the Highway 37 project was eligible for TCEP funding because the corridor is a freight transportation route between Highway 101 and Interstate 80. She said about 25% of North Bay freight is transported on Highway 37.

An estimated 40,000 commuters use the highway every day to travel between Marin County and Vallejo, and the 21-mile corridor is notorious for its congestion. A few supporters of the highway project told the commission about the traffic issues.

Michael Pickens, a representative of Operating Engineers Local 3, said he travels on Highway 37 every day.

“It is vital that not only do we need safety improvements there, but to keep people from sitting 45 minutes to just go 2 miles on a piece of road,” he said.

Solano County Supervisor Mitch Mashburn told the commission that the traffic particularly affects low-income workers commuting to their jobs. Mashburn that 85% of the highway’s users earn below the Bay Area median income.

Commissioner Jason Elliott, reflecting on the affected commuters, said there is not enough housing in the Bay Area.

“I am not comfortable choking off their ability to get to their jobs,” he said.

Opponents of the project warned commissioners about the Caltrans forecast that the rising sea that will flood the highway by the 2050s. Zack Deutsch-Gross, policy director of the Oakland nonprofit TransForm, said the highway is projected to be underwater within 15 years of the project completion.

“We don’t believe that the interim project advances the long-term vision of the corridor or will reduce congestion for passengers who need it the most,” he said.

Doanh Nguyen, a deputy district director at Caltrans, addressed the concerns about the rising water. He said the forecast was based on a 2020 report by the California Ocean Protection Council that predicted segments of the highway could be flooded under 24 inches of water by 2050. He said a recent projection reduced the water level to 12 inches.

“Currently, based on the best available science that we have at this point, with the funding approved, we will be able to finish construction and realize the benefit for the corridor up to 2050,” he said.

Nguyen noted that the corridor won’t be under water, but rather there will be a higher frequency of flooding there.

With the funding approved, Caltrans needs to complete several steps before starting construction.

Justin Behrens, a deputy director for the state commission, said Caltrans must complete the project’s design and environmental review processes before returning to the commission to have the committed funds allocated.

Nguyen told commissioners that Caltrans aims to complete the phase 2 design plans in late 2026 and complete the construction by the fall of 2029.