Costly Bay Trail segment proposed for southern Sonoma County

The estuary of Tolay Creek southeast of Petaluma offers refuge to a host of wildlife, including rare shorebirds and waterfowl and a species of endangered mouse that lives only in the salt marshes of San Francisco Bay.

But the tidal waterway, which widens as it drains into San Pablo Bay just south of where it crosses under Highway 37, also sits in the way of a key link in the 500-mile trail envisioned to one day circle San Francisco Bay. About 70 percent of the network is complete.

To span the creek and close the 0.8-mile gap between two existing trails, parks officials are proposing a foot- and bike path with a hefty projected price tag: $9 million to $14 million, depending on the design and alignment.

“It’s not a cheap endeavor,” said Ken Tam, planner with Sonoma County Regional Parks. “Where the trail alignment is located is actually in mud flats, and the materials to support a pier structure have to go very, very deep in the bedding to be sound. That increases the overall cost of the construction.”

The money could come from an proposed ballot measure in June that would increase in tolls on state-owned bridges in the Bay Area by $1 to raise an estimated $4.45 billion for transportation upgrades in the region. Up to $100 million could go to a long-delayed overhaul of Highway 37, where rebuilding costs are estimated at $1 billion to $4 billion.

The proposed Sears Point trail connector was endorsed as a parks priority last month by the Sonoma County Board of Supervisors after an initial study highlighting the recreational demand and obstacles associated with the project.

The connector would link the 2.5-mile Eliot Trail to the west and the 2.9-mile Tubbs Island Trail to the east. The trails and surrounding area exist within the San Pablo Bay National Wildlife Refuge, a focal point for extensive wetlands restoration work in recent years.

In 2015, in one of the most ambitious projects to date, a 140-year-old Sears Point levee was breached and over 1,000 acres of reclaimed hay fields flooded to recreate the type of wetlands that once ringed the bay. Walkers and paddlers can watch the tide rush in and out of the wetlands, attracting a variety of birds and aquatic life.

Any trail link would have to withstand or accommodate those same tides, as well as rising sea levels. Options include a walkway atop earthen fill, an elevated fiberglass boardwalk and a floating aluminum boardwalk.

The project could be designed to work with the overhaul of Highway 37 and was thus recommended for inclusion in the long-term plan for the highway corridor. Construction on the roadway isn’t slated to begin until 2030 under the current blueprint, meaning any work on the trail segment could also be far off.

“Part of that plan calls for a network of pedestrian access points, including the Bay Trail,” said James Cameron, the Sonoma County Transportation Authority’s director of projects and programming. “It’s a very logical connection, because it connects to the existing other couple miles. So that would be an excellent candidate and it’s competitive with each of the other Bay Area counties looking at those funds.”

The Bay Area bridge toll proposal going to voters, Regional Measure 3, would carve out $150 million to close critical gaps in the Bay Trail. The Sears Point connector could also be eligible for some share of the proposed Highway 37 funding.

“We know that the desire on Highway 37 is for it be multi-modal, and it has to be accessible to public,” said Sonoma County Supervisor David Rabbitt, the current president of the Association of Bay Area Governments, which is spearheading the wider Bay Trail project. “Obviously it’s more cost-effective to plan all of it at once and build it all at once, to get a discount of scale and scope on the project.

“It is a pretty unique landscape out there, and it has a lot of wildlife to enjoy those places along the way,” he added. “It would be a nice amenity. And we’d want to do it in a way that’s enjoyable - not next to the roadway with cars whizzing by at 60 miles per hour.”