Searsville Dam has lost over 90% of its original water storage capacity as roughly 1.5 million cubic yards of sediment have filled in the reservoir. It poses an impassable barrier to steelhead attempting to migrate to historical spawning grounds mostly upstream of the current dam site in the San Francisquito Creek watershed. While a few steelhead have been seen spawning below the dam in past years, they can no longer access the high-quality habitat above the dam, and resident fish upstream cannot emigrate to San Francisco Bay and the Pacific Ocean.
The sediment trapped behind the dam and what to do with it presents the biggest obstacle to dam removal. Simply removing the dam and letting all the sediment move downstream would compromise existing flood control features in a heavily urbanized and modified watershed. This could increase the risk of catastrophic flooding for dense, high-value real estate downstream of Stanford’s campus.
Removing Searsville Dam represents an important opportunity to significantly increase spawning and rearing habitat for federally threatened Central California Coast steelhead in an anchor watershed that is necessary for recovery of the species.
Stakeholders have been working to identify feasible opportunities to allow fish passage at Searsville Dam for over a decade, with several independent consultant reports but no clear path forward to show for it. Complicating the situation is the significantly altered watershed downstream of Searsville, where the existing channel of San Francisquito Creek can no longer safely pass flows downstream without flooding neighboring cities. Significant investments in replacing undersized culverts and other barriers at road crossings have been made already, but more infrastructure improvements would be required for miles downstream to allow sediment and streamflows to move out to San Francisco Bay without backing up floodwaters onto densely populated urban areas.
Searsville has been a contentious subject for Stanford University and those paying attention to steelhead and salmon issues in the Bay Area for decades. The challenge of balancing flood risk and fish passage, the very low abundance of steelhead on the Peninsula, and the extremely high cost of any potential solution makes finding a path forward difficult. Stanford has committed to presenting their internal fact-finding on the fish passage possibilities at Searsville Dam to external stakeholders and the National Marine Fisheries Service once they have selected a preferred alternative. However, this has not happened despite several years of waiting.
A possible option is to punch a hole in the bottom of the dam to slowly meter out the reservoir’s sediment from the reservoir over a period of years, gradually moving it downstream to San Francisco Bay. Sediment is badly needed in the bay to reinforce marshlands impacted by sea level rise. After a period of time, a second project phase of stream restoration and eventual removal of the dam itself would begin to allow steelhead unimpeded access to historical habitat upstream in the watershed.
Whether it’s that option or another, a solution is needed. The high cost of dam removal, insurance liability coverage, and the hesitancy of Stanford University and the surrounding communities to enter into serious dam removal conversations has created difficult challenges and has slowed the progress.
Corte Madera Creek, San Francisquito Creek Watershed
1892List of Stakeholders
Beyond Searsville Dam Coalition
California Department of Fish & Wildlife
National Marine Fisheries Service
Joint Powers Authority
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