State Route 37, a low-lying commute route that skirts the northern edge of San Pablo Bay, is both traffic-choked and increasingly flooded due to sea level rise. Sitting atop a precarious levee that confines an immense but compromised marsh complex, Dr. Fraser Shilling of the UC Davis Road Ecology Center has observed, “the highway has the dubious distinction of constricting both traffic and tidal flows.” The project considers a new future for this highway as an elevated scenic byway, creating an iconic “front door” to a vast ecological open space previously known to few. Accessible to cyclists, runners, kayakers, campers, and fishermen, the Grand Bayway will become a Central Park with more 21st century sensibilities for rapidly expanding North Bay communities.
ABOUT The Grand Bayway
The project encompasses an area larger than San Francisco. It spans from Highway 37 and Mare Island to the south, across vast wetlands in varying states of recovery or inundation, to the Carneros wine county in the north. At the western edge is Sears Point Raceway sitting at the base of Cougar Mountain and to the east is the Napa River and the border of the city of American Canyon. The area has very limited access by foot or vehicle and, in fact, is easier to visit by boat on the tidal sloughs that interlace the marshes. As these areas have been manipulated for human use over the last 150 years, they have frequently been diked off from bay waters and tidal fluctuation. Highway 37 sits atop one of these levees. Large areas of the San Pablo Baylands were converted to agriculture in this way. Cut off from tidal exchange and watershed runoff, they gradually subsided due to soil depletion from farming and lack of natural sediment deposits – similar to what we see in the Mississippi Delta. Some zones are now 7-8 feet below sea level and the entire area is at risk of becoming open water and losing much of the ecological function and recreational value.
The project proposes to resolve the transportation problem of Highway 37 by designing a scenic causeway elevated on columns 20 feet high, allowing tidal flows and marsh migration to return to a natural condition. These same principles operate whether in the current Southern Alignment or moved to an alternative Northern Alignment, skirting the edge of stable uplands. The causeway is designed with the same ambition and flair as other iconic bay crossings but based on 21st century sensibilities for the natural environment and diverse transit types, not just vehicles. Rather than broad concrete platforms on a forest of columns, this design is based on the principles of scenic byway design, curving to open views over the Bay and marshes and oriented to natural landmarks. Lane directions as well as the Bay Trail are “unspooled” and flow independently like the sloughs they traverse, creating access to open space below. This level of investment in design and visibility for an ecological “Central Park” will return major value for the region, its identity, and its future. A great mobility loop will encompass the open space involving pedestrian and bike routes collocated with an excursion train using an existing freight line. Visitors will arrive at a variety of historic train stop ghost towns such as Buchli and Wingo, revived for cultural education using narratives of those who have lived with these lands in the past. The huge baylands complex is of course inextricably linked to the resolution of the highway. To prepare for rising sea levels, the project proposes to create an ecological laboratory working strategically with streams and diked sloughs to incrementally re-engage sediment deposits and cultivate biodiversity though various means including “sediment trains,” hyper-accretion gardens, and floating wetlands.
Typical of San Francisco Bay in general, San Pablo Bay is structured by parallel rocky, fault-generated ridges and soft alluvial lands between them where water collects and flows. We’re facing decades if not centuries of both coastal flooding and seismic liquefaction of soft ground – one incremental by nature, the other instantaneous. But current settlements in California are only 150 years old. We have a very short and rather unprepared track record. Flat and compliant, shoreline marshes and mud flats have been an easy place to construct infrastructure – highways, railroads, airports, and refineries. This project is about adapting our lives and our infrastructure within these fertile and biologically diverse lands frequently degraded by marginal human uses and unstable fill. These lands are also the home for many people including some of the most disadvantaged neighborhoods in the Bay Area who frequently have no voice in their own future. Shoreline communities and infrastructure are at the front line of sea level rise and seismic challenges throughout the Bay Area and around the entire Pacific Rim. City and regional leaders need a plan, not just for how to patch flooding problems, but for how to grow their cities along their shorelines by putting much more focus on people, habitat and healthy connections with the Bay.