FOLSOM — The City of Folsom is moving ahead with a critical infrastructure project that will replace decades-old valves at the Willow Hill Reservoir dam, following unanimous approval from the Folsom City Council on August 26. The project, known as the Willow Hill Dam Valve Replacement Project, is the final component of the city’s Water System Rehabilitation Project No. 1, which has already seen major upgrades across the community’s water system.
The Environmental and Water Resources Department recommended approval of Resolution No. 11438, which adopts the Initial Study and Mitigated Negative Declaration (IS/MND) required under the California Environmental Quality Act (CEQA) and authorizes the project.
“This project is about ensuring the long-term safety and reliability of one of our city’s key water assets,” Yasutake shared in his staff report presented to Folsom Council. “The valves at Willow Hill Dam have reached the end of their serviceable life, and replacing them is not only necessary to meet state safety requirements but also essential for the ongoing protection of our water system and the community it serves.”
The Willow Hill Reservoir, located at 321 Barnhill Drive, sits within the 43-acre Willow Hill Reservoir Community Park. The project site spans about 18 acres at the southern edge of the reservoir, adjacent to Folsom High School, Prairie City Stadium, Iron Point Road, and residential neighborhoods. This location makes the reservoir and dam not just an infrastructure facility but also a familiar backdrop for the surrounding community.
The project will replace both upstream and downstream valves at the Willow Hill Dam, as required by the Division of Safety of Dams (DSOD). Work will involve demolition of the existing valve structures, installation of a new upstream slide gate valve and downstream isolation valve, construction of a fenced raised landing with valve operator infrastructure at the top of the dam, and the addition of rip rap and armoring to strengthen the dam face. If necessary, a cured-in-place pipe will also be installed within the existing underground outlet pipe to extend its life.
Construction is expected to begin in August 2026 and last about six months, with three months allocated to lowering the reservoir water level and three months for the construction itself. Work will occur during daytime hours on weekdays and Saturdays, in compliance with the city’s noise ordinance. To facilitate construction, a 130-foot-long coffer dam will be temporarily installed, and portions of the park pathways along the dam will be fenced off. Staging areas will be located northwest of the dam, and access may come from multiple points including Barnhill Drive, Blossom Rock Lane, Prairie City Road, and a Folsom High School parking lot.
To comply with CEQA, the city prepared an Initial Study and Mitigated Negative Declaration to evaluate environmental impacts. The study determined that potential effects on biological resources, cultural resources, geology and soils, and tribal cultural resources could all be mitigated to “less than significant.”
“The environmental review confirmed that, with the proper mitigation measures, the project will not result in any significant impacts,” Yasutake explained. “That allows us to move forward confidently with a project that is vital for public safety while also being environmentally responsible.”
Part of that process included consultation with Native American tribes with ancestral ties to the project area. The City of Folsom sent invitations to Wilton Rancheria, the Ione Band of Miwok Indians, and the United Auburn Indian Community in February 2025. Wilton Rancheria initially requested consultation but later determined it had no further comments, and the consultation formally concluded in March 2025.
Other regulatory agencies will also play a role before construction begins. These include the U.S. Army Corps of Engineers for Clean Water Act Section 404 authorization, the Central Valley Regional Water Quality Control Board for a Section 401 Water Quality Certification, and the California Department of Fish and Wildlife for a Lake and Streambed Alteration Agreement.
Environmental analysis also looked at potential impacts to the community. The project will temporarily alter views with construction fencing and equipment, but the report concluded there would be no long-term impact to the park’s scenic character. Noise will be limited to standard construction hours, and no new light or glare will be introduced. Sensitive receptors, including nearby homes and Folsom High School, were considered in the air quality review, and construction emissions were determined to be below significant thresholds.
Funding for the Willow Hill Dam Valve Replacement Project is already secured within the city’s Fiscal Year 2025–26 Capital Improvement Budget under the Water System Rehabilitation Project No. 1. The project is fully supported by the city’s Water Fund and does not require additional revenue sources.
“Investing in these infrastructure upgrades is essential to keep Folsom’s water system safe and reliable,” Yasutake said. “By staying ahead of issues like this, we’re protecting our community’s future.”
The Willow Hill project represents the final major improvement under Water System Rehabilitation Project No. 1, which has also included the replacement of the waterline serving Black Miner’s Bar and rehabilitation of the Rainbow Bridge waterline. Once construction contracts are bid and awarded, the city will return to council for approval of the agreement.
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