A new plan to excavate and restore a zigzagging freshwater wetland behind Chicken Ranch Beach in Inverness could eliminate the mysterious bacteria that appears at the popular beach during high tides and big rains. Hydrologists hired by the Tomales Bay Foundation say that by removing acacia trees, introducing native plant species and connecting the wetland to the nearby creek, the bacteria would be absorbed by the wetland before the water flows into the bay.
In a meeting last month, Sebastopol-based ecological restoration firm Prunuske Chatham, Inc. presented a rough design supported by the California State Lands Commission, Marin County Parks and the private property owners adjacent to the area. Residents mostly expressed support for the project, though a few voiced doubts about some of its potential components.
The project, which has been years in the making, would take place on a little more than an acre behind Chicken Ranch Beach. Ninety percent of the land is owned by the State Lands Commission, 9 percent is owned by the county and 1 percent is part of a beachfront property owned by Janice Butler and Robert Weltman.
The current design allows for the water to slowly pass through the excavated wetland over the course of days, a feature that hydrologists said would provide for a significant reduction in bacterial concentrations. Any bacteria not eliminated within the wetlands would be diluted by the higher-volume, cleaner flow of water in nearby Third Valley Creek.
Using the excavated sediment, hydrologists would fill the contaminated channel, known as Channel B, which intersects the beach. A proposed piece of the project that is not part of the final design would use excess sediment to create a berm on the beach that could help armor against rising seas.
In the wetland, new features like submerged logs, boulders and native vegetation could help create habitat for special-status species like northwestern pond turtles and California red-legged frogs. Although the endangered tidewater goby has not been spotted at Chicken Ranch, hydrologists say the project could establish a compelling habitat for the fish. The area could also support the saltmarsh common yellowthroat, a warbler and species of special concern.
Shrubs, grasses, ferns and trees like red alder, coast live oak, shining willow and arroyo willow would replace the forest of invasive acacias that covers over half of the project area.
A berm on the beach would help protect Chicken Ranch from storm surge, said Christopher Woltemade, a hydrologist with Prunuske Chatham. The highest part of the beach is six-and-a-half feet above sea level, and king tides can submerge the entire beach. A berm up to 3 feet high would significantly reduce flooding as sea levels rise. Mr. Woltemade said the berm would not stop brackish water from the bay entering the wetland, but that would not adversely impact the ecology.
Inverness Park resident Gordon Bennett took issue with applying sea-level rise projections to the bay and the idea of relocating sediment. He said Tomales Bay is already prone to sediment buildup and the county’s sea-level rise prediction model was not designed for estuarine shorelines, where sedimentation changes the effects of sea-level rise.
“I think the project as a whole has a chance of being successful, but adding this big component of suddenly doing sea-level rise mitigation is just an excuse to try and reduce the cost of disposing of the material they are going to excavate that would normally go to the landfill,” he said.
He said if the project designers want to keep the sediment dredged from the wetland onsite, they should do so in an area where it does not risk being deposited back into the bay.
Mr. Woltemade acknowledged that the area is a dynamic environment. “If we implement this project, it is still going to evolve over time. It will, as sea level rises, take on some [brackish] water and change vegetation. It will change some of the habitats and change the wetland, but it’s built into the design as an expected element. We would just start to see salt-tolerant plants evolve 20, 30 or 40 years down the line.”
Chicken Ranch Beach’s Channel B has faced bacterial pollution since at least 2007, said Tom Gaman, the chair of the Tomales Bay Foundation. That year, the Tomales Bay Watershed Council—a defunct organization that preceded the foundation—conducted testing that revealed bacterial levels that surpassed the state Department of Public Health’s swimming standards.
In 2015 and 2018, county DNA studies found that the bacteria came from a non-human source. Hydrologists speculate that there may be a natural subterranean bacterial hotspot that seeps into the channel. Mr. Gaman believes that when the previous property owners excavated a portion of the property to build a bed and breakfast, a subterranean hotspot was tapped, though there is no evidence of the bacteria’s origin.
Channel B failed to meet water quality standards twice in 2022. According to Arti Kundu, a project manager with the county’s Environmental Health Services division, the county stopped collecting biweekly samples from the channel last summer due to the consistent absence of water there.
In the early 1900s, Chicken Ranch Beach was a brackish lagoon fed by Third Valley Creek and Tomales Bay. Several projects by property owners, the county and a telephone company reshaped the landscape over the next century. In 2008, the Tomales Bay Foundation received a $108,000 grant from the California Coastal Conservancy to fund a 15 percent design for a restoration of the area. The design was ultimately nixed for being too pricey, and the county was reluctant to champion it after a lawsuit by the previous owners held the county legally responsible for flooding on the property because its staff had permitted the home.
In 2022, the foundation got a second Coastal Conservancy grant of $249,000 to fund an 80 percent design. The conservancy and the Tomales Bay Foundation are working to secure a $812,000 grant from the U.S. Fish and Wildlife Service to cover the remainder of the project, from permits to construction and native plant maintenance.
Prunuske Chatham hopes to get an exemption from California Environmental Quality Act review and begin construction in 2025. Construction would take just six weeks.