Caltrans favors elevating Highway 37 to address flood risks

In an effort to protect Highway 37 from rising sea levels, a new state study calls for elevating the route onto a causeway within the next two decades.

Presenting its findings this month, Caltrans said its preferred solution is to build a 30-foot-high, four-lane causeway along the current alignment of the highway, a 21-mile corridor connecting Highway 101 in Marin County to Interstate 80 in Vallejo. The plan would include a pedestrian and bicycle path and might include an extension of SMART train service between Novato and Suisun City.

The announcement was celebrated by project proponents who say the causeway is the only way to adapt the highway to the threats from rising water and improve wetland habitats in San Pablo Bay.

“The bottom line is that a causeway as envisioned would ultimately facilitate the largest wetland restoration project in the West Coast while alleviating the traffic congestion,” said Tom Mumley, assistant executive officer of the San Francisco Bay Regional Water Quality Control Board. “It could potentially be a national example of how to work with nature to adapt to climate change.”

A final draft of the study is set to be released in December.

The causeway was one of nine alternatives Caltrans assessed in the nearly two-year planning and “environmental linkages” study. Other alternatives included relocating the highway farther north and building a causeway across the bay.

However, Caltrans said the causeway likely won’t be completed for another two decades and will come with a hefty price tag of $6 billion to $8 billion. Meanwhile, projections on rising seas show the road could be regularly inundated beginning in 2040.

“Of course, I will say there are a lot of unknowns right now,” Caltrans planner Chris Caputo said during a presentation of the study on Sept. 14. “We don’t have funding identified or secured. But none of that is going to stop the sea level from rising. That’s one of the main drivers for us.”

Built as a toll road in 1928 in an area once underwater before settlers diked and drained the wetlands, the highway now has flooding that can force road closures during high tides and storms.

But Caltrans and other transportation planners say existing traffic issues for tens of thousands of commuters on the highway also need to be addressed before the causeway is built. The agency is proposing a $430 million interim project to temporarily widen a 10-mile section of the highway between Sears Point to the west and Mare Island to the east. This section bottlenecks to two lanes, causing up to 70 minutes of extra travel time during peak morning commute hours.

Caltrans is proposing to place thousands of truckloads of fill on protected sensitive wetlands and wildlife refuges to temporarily expand the highway to add a carpool lane in each direction. An environmental review of the proposal is set for release in October or November, according to Caltrans spokesman Vince Jacala.

The proposal has prompted concern from some environmental organizations, wildlife managers and politicians for its impacts to wetlands. Rep. Jared Huffman, whose district includes Marin and part of Sonoma County, said that while he is pleased Caltrans chose the causeway as its preferred long-term fix, expanding the highway will prevent the causeway from ever being built.

“It’s like a split-personality disorder,” said Huffman, a Democrat who lives in San Rafael. “We finally have Caltrans and others to look at this the right way, but only in a conceptual 20-years-from-now context. In the meantime, they’re going to make it impossible to do this with this overbuilt, brand new four-lane freeway.”

Huffman said the disconnect with Caltrans will squander a “golden opportunity” to take advantage of once-in-a-generation funding through California’s $100 billion budget surplus and the recently passed $1 trillion federal infrastructure bill.

State Sen. Mike McGuire, a Democrat from Healdsburg, said commuters stuck in traffic want to see a fix as quickly as possible, but that conversations about the interim project are still ongoing.

“I continue to have a concern about the 20-year time frame that Caltrans is stating,” McGuire said of the causeway project. “So the bottom line is, I need to sit back down with Caltrans in order to narrow the construction timeline.”

Mumley said the interim project does include proposals to mitigate impacts to wetlands and projects to restore tidal influence on wetland habitat that has been cut off by the highway berm.

“That really pleases us that that is part of it,” he said. “We’re feeling pretty good about where things are.”

How these projects will be funded remains unclear. A bill by Sen. Bill Dodd, a Democrat from Napa, proposed to make Highway 37 a toll road to help pay for the interim and long-term projects. The bill did not make it through the Assembly committee review process this session.

Whether Dodd plans to reintroduce the proposal next year is unclear. His office said he has not finalized his legislative calendar.

More information about the study can be found at https://bit.ly/3LLLwQP