Twin Oaks Reservoir Tank No. 2 - The largest pre-stressed tank in the world!

Vallecitos Water District originally planned to construct twin 33mg tanks at the Twin Oaks Reservoir site. The first 33mg tank was constructed beginning in 1998 and completed in early 2001. However, due to updates to the District's Master Plan, it was determined that additional storage beyond the planned 33mg was going to be needed. IEC completed a planning study and alternative analysis to maximize storage on the existing site. The study recommended construction of a 40mg circular prestressed concrete tank on the site for a combined reservoir capacity of 73mg. When complete, the tank will be 40 feet high with an inside diameter of 432 feet making the total capacity 40 million gallon. The tank will include 249 miles of pre-stressed wrapping strand, 22,950 CY of concrete, and 575,000 pounds of steel. The project will be constructed in three phases: mass grading, reservoir construction and final site improvements. When the third phase is complete, the reservoir will be completely buried and landscaped, concealing it from the surrounding community. In combination with the Twin Oaks Reservoir No. 1, an existing 33 MG tank on the same site, this project will complete the ultimate master plan for storage facilities on the Twin Oaks site, having an overall water storage capacity of 73 MG.