BOARD AGENDA MEMORANDUM
SUBJECT:Title
Receive an Update on the Pacheco Reservoir Expansion Project, Project No. 91954002 (Santa Clara County, Merced County, District 1).
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RECOMMENDATION:Recommendation
Receive information on the Pacheco Reservoir Expansion Project.
Body
SUMMARY:
The Pacheco Reservoir Expansion Project (PREP) will expand the storage capacity of the existing Pacheco Reservoir from 5,500 acre-feet (AF) to up to 140,000 AF to provide increased emergency water supplies, improved water quality, and ecosystem benefits. Project components include installation of a new dam on the North Fork of Pacheco Creek and appurtenances including outlet works and spillway; installation of a new pipeline between the existing Pacheco Conduit and the new dam; decommissioning of the existing dam with creek restoration; a new pumping plant; new power supply and other appurtenances; and improved site access.
Recent discussions regarding PREP's development of environmental documents, permitting timelines, field investigations, and design process have prompted necessary changes to the project scope and sequence of work. A combination of these factors contributed to the scope changes and the schedule forecast to complete the required project elements prior to construction phase.
In late 2021, the planning phase and 30% design was near completion, and the PREP Draft Environmental Impact Report (EIR) was released for public review. It identified the project preferred alternative as the upstream hardfill dam type with a 140,000 AF capacity, located approximately one mile upstream of the existing North Fork Dam. Upon the release of the PREP Draft EIR, the Department of Water Resources Division of Safety of Dams (DSOD) rejected the hardfill dam concept due to limited performance history and stated the earthfill dam type alternative remained a feasible option.
After receiving DSOD's request to change the dam type to earthfill, staff and consultants completed the co...
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