By Judy Horning
Known for its theme parks, sports teams and convention center, Anaheim, Calif., is the most populous city in Orange County and the 10th largest city in the state. Centrally located within Anaheim, the Linda Vista Complex is a vital water storage and pumping facility capable of providing up to one third of the city's water supply.
The Anaheim Public Utilities Department, along with the engineering firm Psomas, determined that the complex's existing 4-million-gallon (MG) concrete-lined earthen reservoir, constructed in 1935, had reached the end of its design life. The structure did not meet current seismic codes, which would require extensive rehabilitation. In addition, the pumping capacities would not meet future demands.
As part of Anaheim's long-range planning efforts, the Linda Vista Reservoir and Pump Station Replacement Project was designed to meet the objectives of increased system reliability and operational flexibility as well as the provision of adequate capacity for future expansion and growth. The first phase included the partial demolition of the existing reservoir and construction of a new 4-MG water storage reservoir plus the relocation of two booster pumping stations on a tight site in a busy industrial community.
After careful consideration of all the options, environmental impacts and long-term benefits, the project team determined that an AWWA-D110 Type-I circular, prestressed concrete tank from DN Tanks offered the optimal solution for water storage at the site. A Type-I prestressed concrete tank was a natural choice, as it offered the highest quality, lowest maintenance, proven seismic performance and an extended service life. It also allowed the reservoir to be partially buried to reduce the visual impact to the surrounding neighborhood. Upon completion, the tank was painted a two-tone earthy color and included architectural treatments such as vertical pilasters and horizontal bands.
DN Tanks was awarded the contract to build and prestress the new reservoir. With a capacity of 4 MG and a diameter of 148 feet, the reservoir's circular shape improved water quality and circulation. The tank floor, footings, columns, walls, and flat slab roof were all designed and constructed with concrete. The walls were constructed using cast-in-place concrete, and each wall section was poured full height, which eliminated horizontal jointing.
Given that the reservoir was located in California and the high probability that the tank might be subjected to high seismic forces during its service life, the new reservoir was built with a proven seismic design. Specialized anchored flexible seismic connections were incorporated at the wall base and top, similar to a base isolation detail, in order to maximize the ductility of the structure under a seismic event.
In addition, providing compression to the concrete corewall both vertically and circumferentially yielded an efficient structure to contain the large loads produced by the stored water as well as the subsequent backfill and design live loads. DN Tanks utilized the latest prestressing technology for the project. Due to hydrostatic, hydrodynamic, differential temperature and moisture loads on the wall, the reservoir wall was prestressed in two directions, both vertically and circumferentially.
Vertical prestressing utilized threadbars embedded in the wall, while circumferential prestressing utilized DN Tanks' prestressing machine to continuously monitor and provide accurate applied stressing force on the galvanized stand as it was applied to the tank corewall. Upon completion of prestressing, the strand was encased and protected with shotcrete.
Innovative design, construction and prestressing techniques were incorporated into the Linda Vista Reservoir and Pump Station Project to provide the community with safe and reliable water storage that will meet current and future capacity requirements and operational needs.
About the Author: Judy Horning is a marketing associate with over 21 years of experience researching and writing articles about water and wastewater storage tank projects for DN Tanks. DN Tanks is a specialist in the design and construction of AWWA D110 prestressed concrete tanks used for potable water, wastewater, chilled water, and other liquids.
DN Tanks is exhibiting at AWWA's ACE15 expo in Booth 1739.
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