The Coyote Percolation Dam Replacement Project will help protect the water supply, groundwater basins and wildlife in Coyote Creek once Valley Water finishes building the Anderson Dam tunnel in 2024.
This tunnel will help control the amount of water released during storms from Anderson Reservoir to Coyote Creek. Water could be released at nearly five times the rate during major storms or emergencies.
To make sure the creek can safely handle the increase, Valley Water will replace the existing steel flashboard dam at the Coyote Percolation Pond with an inflatable rubber dam. The dam would be quickly raised when water levels into the creek are low and lowered to allow higher water flows to pass safely.
Construction to start on new inflatable dam at Coyote Creek
Valley Water will install a new inflatable rubber dam at Coyote Creek to replace the current steel dam. The work is anticipated to begin in mid-May and continue through 2024. There will be noise and dust typically associated with construction. Valley Water will make every attempt to minimize these impacts. All construction staging areas are within Metcalf Park on Valley Water or Santa Clara County property. Traffic control will be used where necessary.
The inflatable dam will make it easier for Valley Water to quickly control the amount of water released during storms from Anderson Dam to Coyote Creek. Steel dams can take between one to two weeks to remove and install. Rubber dams can inflate and deflate in about 45 minutes. The new dam will also help keep the water at the Coyote Percolation Dam at levels necessary to recharge the groundwater basin.
October 2022 meeting information
Valley Water held a public meeting in October 2022 to update neighbors about the current design of the Coyote Percolation Dam Replacement Project. The project supports the Anderson Dam Seismic Retrofit Project’s construction of an outlet tunnel next to the dam, allowing more water to be released during a storm or other emergency.
Below is a recording of the meeting along with other materials shared at the meeting:
- Project presentation
- Meeting recording
- Project fact sheet
If you have questions about the project, please contact neighborhood liaison Tony Mercado at [email protected] or 408-630-2342.
The project is intended to improve operational functions at this site due to the changes taking place at Anderson Dam.
The Coyote Percolation Dam impounds water in the Coyote Percolation Pond, an in-stream pond in Coyote Creek just north of Metcalf Road. Operation of the Anderson Dam Tunnel would result in flows well beyond the safe operating capabilities of Coyote Percolation Dam, which is not rated to handle flows higher than 800 cubic-feet-per-second (cfs).
The maximum release capacity of 2,500 cfs (Anderson Dam Tunnel and existing outlet capacity combined) would overwhelm the Coyote Percolation Dam. Removing the dam to accommodate higher flows would further compromise Valley Water’s ability to recharge the groundwater basins.
To protect against potential risks to groundwater recharge and water supply reliability for the Coyote Valley and South San Jose residents in the Santa Teresa area, Valley Water will replace the existing flashboard dam with an inflatable bladder dam that could quickly be raised when inflows are low to help with percolation and then lowered to allow higher flows to pass safely.