A $500 million project on flood-prone Highway 37 could get a boost clearing some environmental hurdles under a new Assembly bill.

The project, which aims to ease traffic and fortify wetlands between Sears Point and Mare Island, is constrained by short construction windows to accommodate protected species such as the salt-marsh harvest mouse and the California clapper rail, among others.

Assembly Bill 697 would enable planners to seek an “incidental take permit” from the California Department of Fish and Wildlife to relieve some of those environmental restrictions to avoid delays, as long as adverse impacts to protected species are fully mitigated.

“Incidental take” means wound, kill or otherwise harm a fully protected species listed by the California Endangered Species Act during construction activity.

The bill was introduced by Assemblymember Lori Wilson, a Democrat from Suisun City in Solano County.

“Proceeding without the authority created by AB 697 would significantly delay delivery of the improved SR 37 corridor,” a memorandum from Wilson’s office says.

Work windows would shrink to an estimated 10 to 12 weeks per year compared to six to seven months, the memo says.

“Drivers would face longer construction delays, and costs would increase substantially,” it says. “From an ecological perspective, the short work windows would result in an increase of the number and overall duration of project related disturbances to the fully protected species, which would be expected to have a greater adverse impact on species and habitat.”

The Metropolitan Transportation Commission, one of the agencies leading the project in partnership with Caltrans, voted to support the bill on Wednesday.“The highway is plagued with heavy commute congestion with no public transit options,” Andrew Fremier, the commission’s executive director, wrote in a staff memo, explaining why the project needs to advance as planned. “Idling vehicles not only contribute to the climate crisis and poor air quality but also threaten the sensitive habitat nearby.”

Highway 37, used by about 40,000 commuters daily, has frequent flooding that has forced closures spanning several days. Caltrans says sea-level rise could regularly inundate the highway by 2040.

The project covers a 10-mile stretch of the highway. The project will widen and lengthen the Tolay Creek Bridge and add a carpool lane in each direction in an effort to reduce traffic congestion.

The carpool lane will be toll free, but drivers traveling alone will pay a toll.

The project also will restore a 3.5-mile section of degraded tidal salt marsh, called Strip Marsh East, to help protect against sea-level rise and flooding while creating habitat.

In 2023, the Legislature passed Senate Bill 147, which authorized the California Department of Fish and Wildlife to issue incidental take permits for certain projects in transportation. However, the bill does not apply to projects that would widen highways. The Highway 37 effort does not qualify for the permits under SB 147 because it adds a lane in each direction.

AB 697 was introduced to make an exception for the Highway 37 project.

A policy committee composed of officials from Marin, Sonoma, Napa and Solano counties and officials from transportation agencies has been meeting regularly to report progress on the project planning.

At a March 6 session of the committee, Kevin Chen, assistant director of the Metropolitan Transportation Commission, said planners aim to find a construction manager this spring and have plans ready for construction starting in 2026.

He thanked Wilson for introducing the bill.

“This is going to be very critical for us to be able to move the project efficiently without very significant delay as well as as cost increase,” Chen said.

Ultimately, planners say, the entire highway will need to be elevated, an effort costing billions of dollars.

The Metropolitan Transportation Commission’s widening project is an interim strategy.

That’s been a sticking point for critics who say planners should not spend $500 million on an interim strategy.

San Rafael resident Kate Powers, a board member of the Marin Conservation League, said environmental impacts have not been fully evaluated.

The effects of fill hauled in by work trucks, and the associated greenhouse gas emissions from the back-and-forth vehicle trips, are not quantified in the reporting.

Powers said the organization does not support AB 697 for this reason and urged officials to pursue the full buildout of the elevated highway.

“We feel it’s the right thing to do,” Powers said.

Officials reiterated concerns about the fairness of the proposed tolls on the highway.

The plans for a toll structure would affect those traveling west to work, raising questions about commitments to equity. The toll structure would be just east of Highway 121 in Sonoma County.

Chen said staff members are taking another look to potentially identify a better tolling location, as well as to develop toll discounts for those with financial needs.

Andrea Source, the mayor of Vallejo and member of the State Route 37 committee, said residents of her city are tolled in two directions out of the county already.

“I’m hopeful that we can have those real conversations about who’s traveling this highway, and how do we make sure that they’re not disproportionately being forced to pay for it,” Source said.