Highway 37 and the San Pablo Baylands

San Pablo Baylands from above

Photo courtesy of Sonoma Land Trust

State Route (SR) 37 is a 21-mile highway that runs from Highway 101 in Novato to Highway 80 in Vallejo, crossing Marin, Sonoma, Napa and Solano Counties. It runs through the ecologically rich San Pablo Baylands, which provide important wildlife habitat including a principal stop on the Pacific Flyway migration corridor that supports millions of migrating waterfowl and shorebirds. Many partners have invested over $600 million in acquisition, restoration and enhancement of roughly 30,000 acres of the San Pablo Baylands to advance the goals set by the ecological restoration community.

Car stuck on flooded highway

Photo courtesy of The Press Democrat

As flooding in February 2017 that closed the highway revealed, SR 37 is highly vulnerable to both near-term flooding and permanent inundation due to sea level rise. The road is also severely congested, particularly along a two-lane segment from Highway 121 in Sonoma County to Mare Island in Solano County.

In 2015, the transportation authorities and elected officials of Marin, Sonoma, Napa and Solano counties formed the SR 37 Policy Committee to develop an expedited funding, financing and project implementation strategy for the reconstruction of SR 37 to withstand rising seas and storm surges while improving mobility and safety along the route. With approval from Caltrans and in collaboration with the four county transportation authorities, the Metropolitan Transportation Commission (MTC) initiated a Design Alternatives Assessment to evaluate design alternatives for the highway, focusing on the middle segment from Highway 121 to Mare Island (Segment B).

SR 37–Baylands Group 

Wetlands and bridge

Photo courtesy of Ducks Unlimited

In June 2017, in response to the acceleration of plans to redesign and rebuild SR 37, the Sonoma Land Trust convened a group composed of North Bay wetland land managers, ecological restoration practitioners, and other stakeholders interested in the conservation and restoration of the San Pablo Baylands. The group, now known as the SR 37–Baylands Group, reached consensus that the redesign of SR 37 represents both a major opportunity and potential threat to North Bay ecosystems, particularly in light of future sea level rise.

The Conservancy is providing regional leadership to the SR 37–Baylands Group through a technical assistance grant to Sonoma Land Trust under the Conservancy’s Climate Ready Program. The purpose of this project is to ensure that the redesign of SR 37 is compatible with and advances the ecological restoration and conservation goals for the San Pablo Baylands and improves the climate resilience of both the built infrastructure and natural ecosystems.

Vision of the SR 37 – Baylands Group:


Integrate infrastructure improvements for SR 37 with existing and future habitat planning, conservation and restoration to ensure healthy ecosystem function and resilience to landscape scale change of the San Pablo Bay.


Sonoma Baylands Map

Map of Restoration to Date and Planned


Work to Date

The SR 37-Baylands Group has produced a white paper and provided comments on a draft Corridor Improvement Plan that was released in September 2017. To ensure that the highway redesign is aligned with the conservation and restoration goals for the region, members of the Baylands Group have advised MTC on the design of the Resilient 37 Environmental Workshop Series, a process to gather input from representatives of the SR 37-Baylands Group, environmental regulatory agencies, environmental advocacy groups, recreation and public access representatives, and transportation agencies. This workshop series began on October 27, 2017 and is expected run through August 2018.

Input from the SR 37-Baylands Group will inform both MTC’s high-level Corridor Improvement Plan for the entire highway, as well as its more detailed Design Alternatives Analysis focused on the segment from Highway 121 to Mare Island. The Transportation Authority of Marin is funding a smaller study of the segment from Highway 101 to Highway 121 (Segment A). The SR-37 Baylands Group has stated that although the planning for the new design may be done in segments, it is essential that planning for the corridor be North Bay-wide to capture the breadth of ecological processes in the region, including the contribution from upland habitats, rather than focusing solely on the area immediately adjacent to the SR 37 corridor.

Bayland Group Documents

Related Information


Sonoma Baylands Map

Map of Ecological Connectivity

The redesign of Highway 37 presents an opportunity to restore ecological connectivity that is restricted by the current highway, This includes

  • hydrologic connectivity (blue arrows) needed to support wetland processes, such as sediment transport to enable marshes to keep up with sea level rise;
  • reconnection of major tributaries (Napa River, Sonoma Creek, Novato Creek, Tolay Creek, and Petaluma River) to the tidal wetlands (brown arrows) to facilitate sediment transport and enable marsh migration into upland areas;
  • connections among tidal marshes currently separated by the highway (green arrows) needed to restore a broad, continuous swath of habitat; and
  • connectivity needed by wildlife (gray arrows) that are currently unable to cross the road.

For More Information:

Jessica Davenport

Project Manager

State Coastal Conservancy


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