Highway 37 and the San Pablo Baylands

San Pablo Baylands from above

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 to advance the goals set by the ecological restoration community.

Car stuck on flooded highwayAs 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 (DAA) 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 bridgeIn 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: Integrate, Don’t Mitigate

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.


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, an effort 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. Completion of the Corridor Improvement Plan, including the DAA focused on Segment B, is scheduled for spring of 2018. 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.

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