San Rafael, CA – The San Anselmo Flood Risk Reduction Project (SAFRR), which will improve public safety and protect residential and business properties along Fairfax and San Anselmo Creek in the Ross Valley, is progressing to the final design stage.
This bridge and the structure above it often impede flow of San Anselmo Creek during storms.
The region, referred to as Flood Control Zone 9
(FCZ9), has been inundated by flooding for many years. The San Anselmo project would result in a net reduction in flooding for about 530 parcels during chronic flood events that have a 10 percent chance of occurring any given year. In addition to reducing the frequency and severity of flood events, the Marin County Flood Control District expects to implement multiple environmental enhancements as part of SAFRR.
In September 2018, the Flood District Board certified the project’s environmental impact report and recommended moving forward with design and construction. On January 8, the Board will consider awarding a $1.24 million services contract to Stetson Engineers. The San Rafael-based firm will lead a team comprised of staff from local companies to deliver the engineering and design work. The team includes GEI Consultants, ESA, Inc., Oberkamper and Associates, Inc., Abey and Arnold Associates, and walls land+water, LLC. The Board meeting will be held at the Marin County Civic Center, Suite 330, 3501 Civic Center Drive, San Rafael.
The design work will primarily consist of three components: (1) the design of a basin to divert and temporarily store floodwater at the former Sunnyside Nursery site at 3000 Sir Francis Drake Boulevard, located about a mile north of downtown Fairfax; (2) the removal of a building at 634-636 San Anselmo Avenue in downtown San Anselmo, a structure that partially obstructs the flow of San Anselmo Creek; and (3) various flood mitigation measures on downstream private properties that may see a rise in water surface due to the removal of the San Anselmo building.
To manage costs through the design phase, the District has split the intended contract into two phases. The anticipated $1.24 million contract will solely cover the first phase, delivering the engineering and design work needed to secure permits for the three components and develop an operations and maintenance manual for the basin.
This first phase also plans to address flood mitigation measures that could be needed for up to 11 homes in Ross that, following the removal of the building in downtown San Anselmo, may experience an increase in water surface elevation during 25 and 100-year flood events. Based on the assessment, flood risk measures will be designed to meet each property’s conditions. Any potential flood mitigation improvements would only be implemented after the impacted landowners are in agreement with the proposed mitigation.
Following completion of phase one and pending the second phase’s budget negotiations, Stetson Engineers may continue with the second phase. If a budgetary agreement for phase two cannot be reached, the District may seek additional competitive proposals. The second phase will deliver the final contractor bid package of construction plans, project specifications and cost estimates along with environmental permits.
The preliminary cost estimate for SAFRR is $19.3 million, which includes the San Anselmo Avenue building purchase. The flood mitigation project is funded by a $8.7 million state grant and $10.6 million in local funding coming from FCZ9 funds. In November 2018, the Board authorized the acquisition of the building and tenant relocation for the businesses in the building is now underway.
The design and permitting are anticipated to be complete by fall 2019. Construction of the nursery site would be started first and, in summer 2020, construction work would progress to downtown San Anselmo. Learn more by visiting the Ross Valley Watershed program website.