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City of San Anselmo

Challenging San Anselmo: Flood Control

In 2020, San Anselmo’s L’Appart Resto restaurant and adjoining business structures were torn down to make way for a county flood control called the “San Anselmo Flood Risk Reduction Project” (SAFRR). As Chef Olivier and other merchants departed to open businesses elsewhere, millions of dollars in purchase and resettlement costs changed hands. The building’s slab concrete foundation, called “BB2,” remained in the bed of the San Anselmo Creek--a FEMA Regulatory Floodway.

In 2014, San Anselmo and Marin County signed a Funding Agreement with a “Do No Harm” clause resembling the Federal Emergency Management Agency’s (FEMA) ‘no-rise’ requirement that prevents authorization of projects that cause adverse impacts. But the SAFRR project failed to develop mitigation for at least 20 properties that will suffer increased flooding caused by the project.

In 2021, FEMA joined impacted property owners to remind SAFRR proponents that FEMA “no-rise” requirements applied: a FEMA permit was required for completion of the SAFRR project, certifying that the work will cause “no impact” and “no changes” to the base flood elevations.

Seeking to evade the time and costs to come up with a permanent solution to address the FEMA requirement, SAFRR proponents suggested San Anselmo develop a ‘temporary baffle’—a concrete construction in the creek bed to keep flooding at the current level by replicating the flow constriction of BB2 after BB2 is removed… at a cost of $4.2 million.

The $4.2 does not include the cost of removing the temporary baffle structure from the creek bed in the future. The $4.2 does cover demolition of the current plaza and daylighting a small section of the creek, bank stabilization, and vegetation. However, with added permits, a required EIR modification, consultants, and staff time, installation of the temporary baffle results in a potential $5 million in development, removal, and construction costs to keep conditions the same as they were before BB2 was removed.

This new concrete work would prevent flood remediation upstream and downstream of the baffle for as long as it is in place. But San Anselmo could decide to retain BB2 rather than construct and then later remove the District-proposed baffle. Estimates for that strengthening of the existing BB2 slab are $60-80,000.

The expected lifespan of the new ‘temporary’ baffle is up to 30 years, allowing time to develop and fund the required mitigation for impacted homeowners, which is estimated at $7-10 million, of which the now District has $3 million. At one Flood Control Advisory Board Zone 9 meeting, there was conjecture that during the lengthy period the baffle structure remains in the creek, some homeowners might die and leave conservation easements on their properties, thus lessening the cost of mitigation.

Ross had planned to replace the Winship Bridge before construction of the San Anselmo project because that bridge, upstream, affects flood flows and mitigation of SAFRR-impacted properties. However, that project is unfunded because Caltrans Highway Bridge Program funds, essential for the planned removal of the Winship Bridge, have been withdrawn for an indefinite period of time.

Liability is expensive, too. Along with the loss of flood remediation, San Anselmo may lose its CRS flood insurance 15% discount. And, when the County Flood District bought the remaining slab foundation, BB2 became “in danger of collapse”, transferring to the town and its taxpayers the liability that formerly belonged to private landowners.

Meanwhile, the remaining concrete deck (BB2) has become a favored gathering place; a piazza filled with people enjoying the outdoor space. SAFRR’s proposal destroys the existing plaza to install a concrete baffle that replicates BB2 in form and function but does not provide public recreational space. The replacement plaza is narrow and impacted by San Anselmo Avenue’s traffic and the small section of the newly daylighted creek.

The funding grant for this flood remediation project expires on 12/31/22. The grant, which was originally intended for Memorial Park, has been repurposed and extended for years. However, it may not be extended to fund replication of a major flood flow constriction: the temporary concrete baffle.

As it stands, the Marin County Board of Supervisors, flush with taxpayer money, voted unanimously on April 12, 2022, to proceed with funding the design and peer review of the proposed baffle before the Flood Control Advisory Board’s April 25th meeting.

Interested parties would be advised to make their concerns known.