RICHMOND — Shoreline erosion at Point Molate Beach could jeopardize a $6 million recreational trail project through Richmond and threaten historical artifacts. A $2 million city investment approved by the city council on Tuesday aims to find a solution.

For about a decade, the East Bay Regional Parks District and Richmond officials have envisioned expanding a section of the San Francisco Bay Trail, a 350-mile-long recreational route meant to circle the entire bay, along a 2.5 mile section of Richmond’s bayfront.

Once built, the new portion of the pedestrian and cyclists trail would stretch from the historic Winehaven District, once known as the largest pre-prohibition winery in the world before becoming a war-time fuel storage site, past the Chevron refinery to the Richmond-San Rafael Bridge.

With studies conducted and $6.5 million in funding from grants, tax dollars and legal settlements identified, the project was put out to bid. All that now holds up expansion is a crumbling section of Point Molate Beach that sits at the center of the future trail site.

“This is not a hypothetical risk. This is a current happening condition,” Deputy Public Works Director Robert Armijo said during the council meeting Tuesday.

Staff has proposed placing a cluster of large boulders, referred to as a revetment or riprap, on 150 feet of the beach stretch to create a buffer that would prevent future erosion of a 300-foot section of the bluff. The construction of foundation for 80 feet of the new trail would also be completed as part of the project along with swapping a failed 12-inch storm drain pipe with a new 24-inch concrete culvert.

The city had initially planned to repair the section with a $1 million grant from the Division of Boating and Waterways Shoreline Erosion Control Program, matching it with a $500,000 city contribution. But Armijo said staff recently discovered the grant was never awarded.

Growing construction costs, updated design plans and mitigation requirements imposed by the San Francisco Bay Regional Water Quality Control Board have caused the estimated project budget to increase to $2.5 million, the city said.

If the council did not agree to fund the bluff repairs, Armijo and Public Works Director Daniel Chavarria said the city runs the risk of losing grant funding for the Bay Trail expansion that needs to be spent by the end of this year.

“We are right now in the middle of the fire and we need to make a decision right now if we want to lose grants or keep them,” said Chavarria. “What we’re trying to do is save the Bay Trail project.”

Concerns about the potential unintended consequences of installing a revetment were raised by members of the public. Among those concerns are the potential erosion of other sections of nearby beaches, future expensive repairs of that damage and the loss of public access to a chunk of Point Molate Beach.

“Riprap does several things. It does stabilize the shoreline but at a terrible price,” said Sally Tobin, a Richmond resident and member of the Point Molate Alliance and the Richmond Shoreline Alliance. “This kind of damage is very expensive to repair and disrupts biodiversity.”

Without constructing some form of barrier, Armijo said other sensitive artifacts, including human remains from a sacred indigenous burial site and a historic Chinese fisherman camp, could be washed away.

Rerouting the trail could also damage a marsh the city built to offset impacts to other wetlands during a different project, Armijo said.

“With this plan, we are protecting those sites. If we don’t do this, then the bluffs that are currently holding onto these culturally sensitive sites … they will erode and they will go into the bay,” Armijo said.

Chavarria, Armijo and consultants working on the project were unable to answer initial questions about the broader impact of the project and other solutions considered but assured the council they could return before the project is put out to bid to provide more clarity.

Councilmembers agreed to allocate the funding but only with the requirement that staff return with a study session during which more information on the environmental impact of the revetment can be presented along with potential project alternatives.