The Searsville Dam was constructed in 1892 by Spring Valley Water Company. In the early 1900s, Stanford University purchased the dam and associated water rights to ensure adequate water supply for the University campus. For nearly 130 years, naturally occurring sediment has been piling up behind the dam and filling the reservoir, impacting the water supply and storage function of the reservoir. As of today, the sediment held behind Searsville Dam is so extensive that the Reservoir has lost 90% of its water storage capacity.
In 2011, Stanford University formed a faculty and staff Steering Committee to help evaluate options and ultimately recommend a course of action for the Searsville Dam and reservoir. To ensure that the study process had the benefit of a broad range of community perspectives and expertise, Stanford University invited a group of public agency representatives, non-government organizations and community members to be part of a Searsville Advisory Group. The Advisory Group provided input and recommendations for consideration to the Steering Committee and University leadership.
Together, the groups agreed any future project must address the following objectives: restore natural sediment processes and creek flows, restore fish passage while avoiding increases in flood risk compared to existing conditions, minimizing disruptions to ongoing teaching and research at the Jasper Ridge Biological Preserve, and protecting important cultural resources.
Stanford University, in collaboration with federal and state resource agencies, has developed an approach that restores the natural sediment process past the dam and restores fish passage past the dam giving fish access to the upper watershed.
The approach involves constructing a tunnel and gate at the base of Searsville Dam, allowing for the flushing of much of the accumulated sediment downstream to San Francisquito Creek and to San Francisco Bay. The tunnel opening will be sized to pass normal flows but constrict high storm flows, attenuating the peak flow rate downstream. Areas above Searsville Dam will be restored and managed to create a highly functioning confluence valley with riparian areas, meandering creeks, floodplain terraces and wetland areas supporting a variety of habitats and vegetation. The key project components include:
- A new tunnel and gate in the existing Searsville Dam structure
- Downstream sediment traps
- Pilot channels for re-establishing creeks
- New access roads and improved existing roadways
- Natural bank stabilization and re-vegetation
- San Francisquito Creek Pump Station modifications to increase its diversion flow capacity
- Felt Dam and Reservoir modifications to increase storage capacity
Phase 2: Multi-Year Flushing Phase
- Tunnel gate open at initiation of large storm events
- Sediment passes through tunnel during these events