The Hetch Hetchy Water System delivers an average of 222 million gallons of high-quality drinking water per day to 2.6 million people in the San Francisco Bay Area. The system also generates enough clean, reliable hydropower annually for the Modesto and Turlock irrigation districts, City of San Francisco facilities and services, and newly constructed homes and businesses in the redeveloped San Francisco Shipyard.
The Hetchy Capital Improvement Projects (HCIP) are a $949 million, multi-year group of capital projects to upgrade numerous upcountry water transmission, hydroelectric generation and power transmission facilities essential to continued reliable delivery of both water and power. The approximately 30 projects, varying in scope and complexity, address necessary work on water transmission, hydroelectric generation and power transmission facilities in Tuolumne, Mariposa, Stanislaus, San Joaquin and Alameda counties. Construction of some HCIP projects began in 2012, with the entire set of projects scheduled for completion by 2026.
Mountain Tunnel Improvements
This past winter we completed the following two projects to ensure continued operation of the Mountain Tunnel in the Sierra foothills. The tunnel has transported water from Kirkwood Powerhouse to Priest Reservoir since 1925, and is a critical link in our Hetch Hetchy Regional Water System.
|The original Mountain Tunnel construction began in 1918.
||The Tunnel underwent a thorough inspection in early 2017.
Mountain Tunnel Adits and Access Improvements
To meet water delivery goals, the Mountain Tunnel must be capable of returning to service within three months in the event that water service is interrupted. Since quick entry into the tunnel by construction crews and equipment would be essential, we widened and improved certain adits (connecting entry tunnels) and access roads to minimize the time required to return the tunnel to service. An emergency restoration plan is now in place, and we installed new instruments to enhance the existing monitoring system that continually checks for changed conditions in the tunnel.
Mountain Tunnel Inspection and Repairs
In early 2017, we made a thorough inspection of the 19-mile tunnel to update a previous 2008 condition assessment, and our team repaired approximately 7500 linear feet of concrete lining containing large and deep defects that required urgent repair.
In early 2019 another winter shutdown of the tunnel is scheduled to complete other urgent repairs that time did not permit during the last shutdown. The urgent lining repairs are necessary to keep the most significant defect from continuing to worsen and possibly precipitate a lining collapse that would compromise flow and water quality in the tunnel before long-term Mountain Tunnel Improvements are completed in 2026.
Mountain Tunnel Long-Term Improvements
Planning for long-term improvements has been completed, and a decision was made in Summer 2017 to forego a new bypass tunnel and make permanent lining repairs to the existing tunnel instead. The 2017 inspection and condition assessment findings determined that the existing tunnel is still in sound structural condition, despite the numerous lining defects. The City's selection of the Rehabilitate Alternative as the Preferred Project for implementation affirms the feasibility of simply repairing the existing tunnel for another 100 years of service life. Project design and environmental review has commenced, and both phases are anticipated to be completed at the end of 2019. Construction is scheduled for 2020 through 2026.
Cherry Dam outlet works
Cherry Dam Outlet Works
The outlet facilities at Cherry Dam have reached the end of their service life at nearly 60 years old. The stream release assets must be in working conditions to meet U.S. Department of Interior’s stream flow requirements, but requirements cannot be met at low lake elevations. The 66-inch valves will be replaced in order to operate the dam safely during storm conditions and heavy inflows to Cherry Lake. The valves are critical for maintaining maximum carryover storage and meeting SFPUC water supply objectives. The scope of work includes replacement of the stream release valves and associated piping as well as the low level outlet 66-inch hollow jet valves. Construction began June 2016 and is expected to end in May 2018.
Update on Cherry Lake Access and Recreation
Valvehouse maintenance work will impact public access and recreation to Cherry Lake for up to eight weeks starting in September 2017. Read more about the repair work here.
O’Shaughnessy Dam Outlet Works
The O’Shaughnessy Dam Outlet Works consists of several subprojects. The objective of the O’Shaughnessy Dam Outlet Works Project is to rehabilitate the drum gate and the release system from O’Shaughnessy Dam. The Outlet Works consists of six slide gates, seven needle valves and a single butterfly valve; valves are due for upgrades due to age and to meet safety compliance.
O’Shaughnessy Dam Drum Gate Automation is one of several subprojects, and we reached substantial completion of the construction phase for this subproject in December of 2016. The next subproject, the O’Shaughnessy Dam Outlet Works—Access & Drainage Improvements, is in the planning phase.
Site work at Moccasin Yard
Moccasin Yard—New Shops/Office Buildings
The Hetch Hetchy Water and Power shops and buildings are original and vary from 45 to 80 years in age. The primary objective of this project is to build a 10,000-square-foot combined-function complex consisting of a plumbing shop, vegetation management shop, right-of-way shop, electronic technician shop, lockers, shower facilities, and break room. Construction began in July 2016, and we expect completion in February 2018.
Holm Powerhouse Rehabilitation and Kirkwood Oil Containment
Rehabilitation of the Holm Powerhouse equipment seeks to extend the operational life of the powerhouse at least 20 years, reduce maintenance costs and reduce the likelihood of unplanned outages due to equipment failure of older equipment. Oil Containment upgrades at both Holm and Kirkwood powerhouses are intended to avoid noncompliant discharges to the environment and to meet regulatory standards for treatment of oily water. Construction is estimated to begin in fall 2017 and end in spring 2019.
Warnerville Substation Rehabilitation
Warnerville Substation is being upgraded to meet regulatory and safety requirements. This project will address major renewal and replacement of the switchyard components. Work includes correction of grounding issues, fence replacement, disconnect switch replacement, and improvement of the grading in the switchyards. Construction is estimated to begin in fall 2017 and end in February 2019.