Situated atop high coastal peaks and along ridge lines cresting above canyons with expansive views of the Pacific Ocean, Rancho Cielo Estates in Rancho Santa Fe, CA, features over 500 custom luxury residential home and estate sites. This San Diego County residential land preserve stretches over 1,740 acres.
In order to accommodate residential expansion and to supplement the storage capacity in the pressure zone, the Olivenhain Municipal Water District, Encinitas, CA, recently completed the construction of a 2.5-million-gallon prestressed concrete water storage tank. The “Berk” reservoir, named after one of the district’s past directors, has the capacity to supply water to the Rancho Cielo Estates project, as well as the surrounding service area.
Owned and operated by the Olivenhain Municipal Water District, the tank will allow further development within the Rancho Cielo Estates project as well as increase the amount of water available within the district’s boundaries for use during emergencies.
A drought or major earthquake could interrupt water supply in the area for an extended period and some local communities could be without water for a few days. The new storage tank is part of a system of reservoirs, interconnected pipelines and pumping stations designed to make water available to the region in the event of an interruption in imported water deliveries.
Located near the award-winning Olivenhain Dam and Reservoir, the “Berk” tank, itself an award winner from the San Diego chapter of ASCE, was built in the hills of Rancho Santa Fe. One constraint complicating the construction process was the rugged terrain leading to the jobsite. The access road was laden with large sharp rocks that destroyed several truck tires during construction. In addition, construction vehicles were hampered by the steep slope of the road.
The 2.5 MG strandwrapped, prestressed concrete tank is made entirely out of concrete with an inside diameter of 120 ft and a water depth of 30 ft. The tank features a highly reinforced floor, post-tensioned corewall, and a column-supported two-way flat slab roof. Designed to meet or exceed the ANSI/AWWA D110 and ACI 350 standards, the tank was designed and built by DYK Inc. in accordance with the district’s standards.
Innovative construction procedures and practices were used during the wall construction. In order to avoid horizontal joints and prevent leakage, the 10-inch-thick core walls were poured full height in small lifts through special openings from the inside of the wall forms. The use of poured-in-place concrete enhanced the quality and placement of the concrete. In addition, the form openings allow proper concrete consolidation and inspection.
Post-tensioning was accomplished by tensioning high-strength steel threadbars for the vertical direction and circumferentially with machine-applied galvanized 7-wire strand. To protect and bond the circumferential prestressing strand, a 1½-inch-thick shotcrete covercoat was applied to the tank exterior in an automated process.
With the large residential developments and increased population in the Rancho Santa Fe area, the completion of the water storage tank is a vital contribution to the well being of the surrounding community by providing a safe, reliable water supply to accommodate both recent and future growth.
The combined efforts of personnel from the Olivenhain Municipal Water District and the following firms were instrumental in making this project a success: DBE/Psomas, Carlsbad, CA, consulting engineer; Infrastructure Engineering Corp., Poway, CA, construction manager; and DYK Inc., El Cajon, CA, general contractor.
