Valve Installation for O'Shaughnessy Dam Drum Gate Automation

In 2008, the SFPUC adopted the Water System Improvement Program (WSIP), to repair, replace, and seismically upgrade the Hetch Hetchy Regional Water System. The Alameda Creek Recapture Project (ACRP) is one component of the WSIP. The Calaveras Dam Replacement Project (CDRP), another WSIP project, is designed to restore the historic storage capacity of Calaveras Reservoir. CDRP is currently in construction was completed in June 2019.

As a part of the regulatory requirements for future operations of Calaveras Reservoir when the new dam is completed, the SFPUC agreed to implement bypass and instream flow schedules for Alameda and Calaveras creeks, to be protective of Central California Coast steelhead below the Alameda Creek Diversion Dam (ACDD) and Calaveras Dam.

The ACRP would recapture water that will be released from Calaveras Reservoir and/or bypassed around the ACDD during future operations of Calaveras Reservoir. The recaptured water would maintain the historical contribution from the Alameda Watershed to the SFPUC regional water system, in accordance with the SFPUC’s water rights.

The proposed project would recapture a certain volume of water that would be released and bypassed at Calaveras Dam and Alameda Creek Diversion Dam. The recaptured water would be pumped from an existing quarry pit (Pit F2) in the Sunol Valley, downstream of the compliance points for the bypasses and releases below the ACDD and Calaveras Dam, respectively. The project would utilize the natural infiltration of water into the ground in the vicinity of Pit F2, and the recaptured water would be transferred to the SFPUC water system via either the San Antonio Reservoir or the Sunol Valley Water Treatment Plant. The recapture operation would be conducted within the SFPUC’s existing pre-1914 appropriative water rights.

The ACRP would require construction of several improvements in and around Pit F2. All construction activities would occur on SFPUC-owned property, and no construction would occur in the bed, bank, or channel of Alameda Creek. The proposed project components would include:

• Four turbine pumps mounted on barges that would float on the water surface of Pit F2 and be attached to the shore using a mooring system;
• Four flexible discharge pipelines extending from each turbine pump to a new pipe manifold located onshore;
• A new pipeline connection between the pipe manifold and the existing Sunol Pump Station Pipeline;
• Throttling valves and a flow meter;
• An electrical control building; and
• An electrical transformer and overhead power lines.

Operation of the ACRP is dependent on the instream flow schedules that will be implemented as part of the future operation of Calaveras Reservoir. The SFPUC used the Alameda System Daily Hydrologic Model (ASDHM) framework to estimate the volume of water the SFPUC would recapture. The volume of water bypassed and released, and subsequently available for recapture, would vary from year to year. The estimated average annual recapture volume is 7,178 acre-feet per year, with a range of 4,878 to 9,161 acre-feet per year. On average, the total annual volume of water that infiltrates into Pit F2 would exceed the volume of water recaptured.