Hidden behind Chicken Ranch Beach is a marshy acre of state land, bisected by a channel of stagnant water and overgrown with invasive acacias. The channel is contaminated by a mysterious natural source and, during high tides and rains, it spills bacteria-tainted water onto the popular beach. 

“I always call this the bomb crater of Inverness,” said Tom Gaman, chair of the Tomales Bay Watershed Council Foundation, gesturing to the distressed pocket of wetland.

Local conservationists have been looking for a way to repair the troubled waterway for decades. Last week, the council secured a $249,000 California State Coastal Conservancy grant to cover the design and environmental review of a project targeted at filtering and diluting the unhealthy water through an expanded tidal wetland adjacent to the beach.

With help from neighboring landowners, the State Lands Commission, Marin County Parks and Supervisor Dennis Rodoni, Mr. Gaman said he believes his group can harness the state funds to mount a focused and broadly beneficial restoration project that will finally remedy the persistent water quality problems at Chicken Ranch.

The high fecal coliform bacteria counts originate in Channel B, the festering pool of groundwater that occasionally flows into the bay. DNA source testing conducted in 2015 and 2018 ruled out human waste as the source, nearby septic systems are in good condition and there are no clear polluters upstream. Instead, hydrologists have speculated there may be a subterranean bacterial “hotspot” that seeps into the channel.

To carry out the restoration plan, contractors will excavate a new wetland that will be intermittently fed by Third Valley Creek, using the resulting soil to fill in Channel B. They will also uproot the acacia trees and plant native wetland vegetation to reduce sedimentation and contamination.

Though the root cause of the contamination may remain unknown, the wetland’s many natural filtering functions will help ameliorate it, Mr. Gaman said. “It will be an improvement,” he said. “Really, it’s irrelevant what the source is at this point.” 

Chicken Ranch Beach and its surroundings have been shaped by decades of human intervention, creating a confusing patchwork of land ownership and a jumble of drainage channels. The beach was once a spit at the mouth of a brackish lagoon into which Third Valley Creek drained from Mount Vision. The namesake poultry operation was run by the Cavalli family on its shore at the turn of the century. 

In 1953, the Pacific Telephone & Telegraph Company dredged the floor of Tomales Bay to lay an underwater cable from Millerton Point to the R.C.A station on the peninsula, and used the resulting silt to fill in the cove, creating a low-lying triangular parcel between Sir Francis Drake Boulevard and Camino Del Mar. 

The beach and the flood-prone adjacent private properties were the subject of numerous lawsuits in the ensuing decades. In 1971, a dispute over a marina plan at Chicken Ranch led to the landmark California Supreme Court decision Marks v. Whitney, which defined tidal lands as public one year before the California Coastal Act enshrined access to beaches. 

Later, a dispute over inundation led neighbors Kathryn and Gerry Cirincione-Coles to take matters into their own hands and dig channels in the wetland, provoking legal action by the coastal commission. After a 1990 settlement, the small pocket of wetland between the beach and the Cirincione-Coles’ home became state land, and the county government was left liable for any future flooding. A series of storms in the late 1990s further reshaped the landscape. 

The road to restoring the wetland has been long, and already saw one abortive attempt funded by the coastal conservancy. In 2008, the agency granted the watershed council $108,000 for the beginnings of an ambitious plan to overhaul the beach and much of lower Third Valley Creek. But the plan languished. County officials were reluctant to champion it because they feared liability. The Cirincione-Coles lawsuit 20 years earlier had dragged on and made the county legally responsible for flooding on the property because its staff had permitted the home. 

“That’s a common concern for local government,” said Michael Bowen, the coastal conservancy’s project manager for the restoration. “‘If we touch it, then we own the problem.’”

Supervisor Rodoni, who has advocated for the restoration since taking office in 2017, said the first project also bit off more than it could chew. “I think the first plan was a little bit overly ambitious,” he said. 

But a change in private ownership has created a more friendly environment: Robert Weltman and Janice Butler, who own the former Cirincione-Coles property, wrote a letter of support for the watershed council’s project. The new plan, covering a much smaller area, is more contained and cost-effective. The county will still be responsible for protecting the property from flooding, but years of storms and the wetland’s smaller footprint have assuaged drainage concerns, Mr. Gaman said. 

The council expects the project plans and the environmental review—likely a mitigated negative declaration under the California Environmental Quality Act because of the benefits to habitat—to be finished within a year, at which point it can search for a contractor to begin construction. The cost estimates could be high—as much as half a million dollars—but state agencies are flush and grant opportunities are plentiful. Mr. Bowen said the coastal conservancy would “absolutely” have grants available to cover construction costs, and it has an interest in seeing the project completed expeditiously. 

He expressed excitement that the long-delayed wetland restoration was closer to materializing than ever. Though the coastal permit process and potential appeals could pose unforeseen obstacles and the construction could incur new costs, the environmental benefits would be worth the money. 

“What is a saltmarsh worth?” Mr. Bowen asked. “It’s worth a lot to me.”