Proposed Project The project includes two major components that were formerly separate projects. The plant expansion was included under the CUW-38101 Additional 40 mgd Treated Water Supply Project and the treated water reservoir (TWR) was included in the CUW-38102 Sunol Valley Treated Water Reservoir Project. The expansion is provided in response to the Delivery Reliability Level of Service (LOS) goal. The purpose is to increase the sustainable capacity (capacity with the largest unit out of service) to 160 mgd to meet the LOS goal of providing average day demand to the system during an outage of the Hetch Hetchy supply. The TWR is provided to meet the Water Quality LOS goal and is required in response to a California Department of Public Health compliance order. The project will significantly increase plant sustainable capacity and reliability, and system operational flexibility.
Description
The project primarily consists of:
- The expansion will increase the sustainable capacity to 160 mgd by adding a new flocculation/sedimentation basin and by retrofitting some of the existing filters.
- A single 17.5-million-gallon (MG) circular TWR will be constructed together with a new 3.5-MG rectangular chlorine contact tank on the northern portion of the existing plant site. Roughly 350,000 cubic yards of excavated material will be hauled to a disposal site north of the SAPS for disposal.
- New chemical storage and feed facilities for disinfection will be constructed including sodium hypochlorite and ammonia. New fluoride facilities are also provided.
- Construction of approximately 2,700 feet of 78-inch-diameter pipe will connect the new TWR to the existing plant discharge pipeline. This will include a tunneled crossing of Alameda Creek.
- Miscellaneous plant improvements will include a new emergency generator and improvements to the plant electrical system and substation, an upgrade of the instrumentation and controls, a new filter washwater recovery basin, improvements to the flow distribution structure and associated facilities, and improvements to the influent chemical mixing system.
Scope Refinements
The expansion portion of the project originally included construction of a new bank of filters and an entirely new, redundant pipeline connecting the SVWTP to the Alameda Siphons at the Alameda West Portal in addition to the facilities currently identified. Planning evaluations have determined that the plant can achieve the 160 mgd sustainable capacity without the new bank of filters. Also, the existing plant discharge pipeline has sufficient capacity to meet LOS goals, and a new seismically reliable effluent pipeline is not required for LOS goals since the SVWTP is not required to be in service within 24 hours of a major seismic event. Since the new filters and the redundant pipeline are not necessary for meeting the LOS goals, both have been deleted from the scope.
The TWR portion of the project originally included improvements to Calaveras Road at the intersection with the plant access road. Planning studies determined that the road improvements are not necessary for meeting LOS goals, construction access, or for safety, and the improvements have been deleted from the scope.
Finally, the previously anticipated TWR scope has been refined without adversely affecting compliance with the LOS goals. One 17.5-MG TWR instead of two 8.75-MG TWRs will be constructed; the size of the chlorine contact tank has been reduced from 5 MG to 3.5 MG; and a tunneled pipe crossing of Alameda Creek will be employed instead of a pipe bridge or a cut-and-fill pipe crossing.
Need more information?Contact Michele Liapes at (415) 554-3211 or via email at mliapes@sfwater.org
The San Francisco Public Utilities Commission proposes the construction of improvements to the Sunol Valley Water Treatment Plant that would increase capacity, delivery reliability and water quality. Read more
