COMMITTEE AGENDA MEMORANDUM
Water Supply and Demand Management Committee
Government Code § 84308 Applies: Yes ☐ No ☒
(If “YES” Complete Attachment A - Gov. Code § 84308)
SUBJECT: title
Receive an Update and Discuss the B.F. Sisk Dam Raise and Reservoir Expansion Project; Recommend to the Board to Authorize Payment of up to $1,344,613 for Valley Water’s Share of Project Planning Costs.
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RECOMMENDATION: Recommendation
A. Receive an update and discuss the B.F. Sisk Dam Raise and Reservoir Expansion Project.
B. Recommend to the Board to authorize payment up to $1,344,613 for Valley Water’s share of Project planning costs.
Body
SUMMARY:
Valley Water has provided $3,444,063 to date to support funding the planning and development of the B.F. Sisk Dam Raise and Reservoir Expansion Project (Project). Additional funds will be needed on September 1, 2026 to continue into the next phase of planning work.
The U.S. Bureau of Reclamation (Reclamation) and the San Luis & Delta-Mendota Water Authority (SLDMWA), acting on behalf of six members, including Valley Water, are jointly developing the Project. This Project will raise the existing B.F. Sisk Dam by 10 feet and increase the storage capacity of San Luis Reservoir by 130,000 acre-feet (AF), of which 63,560 AF is currently reserved for Valley Water - an amount of storage larger than all of Valley Water’s reservoirs except for Anderson. This Project is separate and distinct from the B.F. Sisk Safety of Dams Modification Project (SoD Project), which is being undertaken by Reclamation and the Department of Water Resources (DWR) to address seismic risks of the existing dam and will not increase the storage capacity.
This memorandum summarizes progress on the Project since the last Committee and Board updates were given on this item in March and April 2025, respectively.
The Project is included in the Water Supply Master Plan 2050, approved by the Board in November 2025, as a part of the lower cost strategy to diversify storage and supply to ensure a sustainable water supply for the community.
Project Costs
At the April 8, 2025 Board meeting, Valley Water’s Board authorized funding of up to $2,241,883 for planning costs through February 2026 for up to 70 TAF of storage if space became available. The share of planning costs associated with Valley Water’s current participation level of 63,560 AF was $1,839,048. The amount supported progress on project management and planning advancements as outlined in this memorandum. Additional funding of $1,925,000 is needed to cover continued program management, planning, and design, including securing mitigation credits. Valley Water’s share is $1,344,613. Valley Water staff recommend that the Board authorize payment of $1,344,613 to cover Valley Water’s share of project costs through February 2027.
The capital cost estimate for the Project ranges from $847 million to $1,045 million, not including financing costs. The estimate includes an escalation rate compounded annually to the mid-point of construction and a 15% design and construction contingency. The cost estimate range reflects that there have been cost savings realized from recent design decisions for SR 152 as outlined above. However, it also accounts for the fact that other costs, such as the cost of securing required mitigation credits, are highly variable at this stage. Additionally, decisions on funding mechanisms have not yet been made and will begin in early 2027.
At Valley Water’s current participation level of 63,560 AF, Valley Water’s share of project costs ranges from $414 million to $512 million. A revised cost estimate reflecting the latest information from the completion of the 30% design stage is anticipated to be released by October 2026.
Contributed Funds Agreement and Spend Plan
In August 2025, a Contributed Funds Agreement between Reclamation and DWR was executed. This agreement allows public water agency participants, through SLDMWA, to contribute to the cost of the Project. It outlines the agreed upon share of Project costs as 70% Project members through SLDMWA and 30% as the Federal share through Reclamation and provides a mechanism for the transfer of funds to Reclamation. In August 2025, a Spend Plan between Reclamation and SLDMWA was also executed, enabling Reclamation and SLDMWA to track costs and funds expended and outline when funds will be transferred. It will be revised as needed to update cost estimates as Project design is refined.
SLDMWA Procurement Policy and Resolution for Collaborative Delivery
In August 2025, SLDMWA adopted a revised procurement policy to prepare for large projects such as this Project. The revised policy allows for consideration of alternative project delivery methods, such as a progressive design-build. “Design-bid-build” is the traditional approach, where the design and build processes are executed by separate contracts. Under a progressive design-build, one contractor serves as both the designer and the builder, which can enhance collaboration, improve cost and scheduling transparency, and reduce risks. The Resolution for Collaborative Delivery outlines how SLDMWA plans to design and construct Highway 152 modifications.
Highway 152 Construction
A major component of the Project involves modifications and protections to California State Route 152 (SR 152). SR 152 modifications include raising an estimated one-mile stretch of SR 152 that crosses Cottonwood Bay along an earthen levee by roughly ten feet and adding slope protection to the East Overlook Parking Area located approximately half a mile from the Cottonwood Bay crossing. Work is being designed and constructed by the California Department of Transportation (CalTrans). Project partners and CalTrans have been in close coordination and have confirmed the following updates to design criteria that will result in cost savings:
1. A previous design alternative included flattening slopes around the Cottonwood Bay embankment area to 3H:1V (a 3-unit horizontal distance for every 1-unit vertical rise) to increase seismic stability. In late 2025, further analysis of the seismology and the seismic requirements resulted in a redesign of the embankment modification that maintains the existing 2H:1V slope. This update significantly reduces the volume of material, construction time, and transport trips needed.
2. Materials were previously anticipated to be transported by barge and tugboat to the construction site to limit truck traffic on SR 152. The reduction in fill material required and the incorporation of additional design alternatives that will reduce traffic impacts made it feasible to transport materials via trucks.
A Final Design Standard Decision document is currently being circulated for signature by CalTrans. Additionally, a traffic effects analysis is being modified to reflect these changes and is estimated to be completed by the end of 2026.
Permitting and Mitigation
Compensatory mitigation is required by the U.S. Fish and Wildlife (USFWS) Service Biological Opinion (BiOp) and the California Department of Fish and Wildlife (CDFW) Incidental Take Permit (ITP). Reclamation and SLDMWA are in close coordination with these agencies to ensure protection and mitigation of the California Tiger Salamander, San Joaquin Kit Fox, and California Red Legged Frog. The Project is actively exploring options to satisfy these requirements, including the purchase of mitigation credits in one or more conservation banks. All permitting is anticipated to be completed by early 2028.
Schedule and Next Steps
Near-term work on the Project includes the completion of a Coordination Agreement; completion of the 30% design stage; review of conceptual design options for intakes and outlet works; continued permitting and mitigation identification; progress on the revised SR 152 design concept; and the development of a Finance Plan.
The Coordination Agreement is nearly finalized and anticipated to be completed this month. It is a mechanism that defines how Project partners and Reclamation will communicate, work together, and manage responsibilities. After the Coordination Agreement is complete, work on the Operations, Maintenance, and Replacement Agreement will begin. It is a mechanism for assigning responsibilities and costs associated with operations and maintenance aspects of the dam raise. It must be completed prior to the first delivery of any water into the facilities. The Management Agreement, signed in January 2025, outlined several follow-on agreements that need to be completed before the participation decision for the Project. These are the final two follow-on agreements.
The 30% design milestone is anticipated in August 2026. It provides more details and design refinements and will be the basis for a construction schedule and cost estimate revision by October 2026. Design work is anticipated to continue through mid-2028 prior to the start of construction. Construction of the dam raise is anticipated to be completed in 2034, though aspects of the SR 152 and intakes and outlet works construction may continue until early 2037.
The final participation decision for the Project is expected to occur before August 2028.
ENVIRONMENTAL JUSTICE IMPACT:
There are no environmental justice impacts associated with this item. This action is unlikely to or will not result in disproportionate impacts on any specific community(ies) relative to the general population from the implementation of this project. However, the B.F. Sisk Dam Raise and Reservoir Expansion Project addresses water supply equity by ensuring a cost-effective, high-quality supply is available for all of Santa Clara County, including disadvantaged communities.
ATTACHMENTS:
Attachment 1: PowerPoint
UNCLASSIFIED MANAGER:
Manager
Vincent Gin, 408-630-2633