The Foothills Nature Preserve Dam (Boronda Lake Dam), is an earthen dam that retains water within Boronda Lake for recreational purposes, but it can also serve as a water source for wildland fire fighting. The lake makes Foothills Nature Preserve a community treasure, and means that it comes under State regulations for dam safety.
The State of California classified the dam as a "High" hazard, requiring the City to have an Emergency Action Plan that identifies the hazard, incorporates an inundation model, shares roles and responsibilities of potentially impacted jurisdictions and agencies, and more.
An inundation study completed in 2022 shows potential areas of significant flooding to include land immediately downstream of the dam, at the confluence of Buckeye Creek, and within the footprint of the Foothills Nature Preserve maintenance facility buildings. Flooding in these areas is generally constricted by topographic features such as steep adjacent slopes or man-made features like an existing berm at the Ranger's Workshop. Depths were estimated to reach up to 6 feet, and up to 3 feet within the central meadows of Los Trampas Valley.
The study also shows that potential dam breach flows greater than 1 foot in depth may continue to the confluence of Buckeye Creek with Los Trancos Creek. It also extends downstream to the confluence at Los Trancos Creek and San Francisquito Creek, with flows continuing to slightly before the intersection of San Francisquito Creek and State Route 82 (El Camino Real) in Palo Alto and Menlo Park. Properties adjacent to Los Trancos Creek and San Francisquito Creek could potentially be impacted by the downstream flow of water.