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Water Supply 4 Zone 7 of the Alameda County Flood Control and Water Conservation District (Zone 7 Water Agency) provides wholesale water to the Tri-ValIey area and also regulates withdrawal and recharge of the underlying groundwater basin. Zone 7 currently has three sources of water: State Water Project water from the South Bay Aqueduct, surface runoff collected in the Del Valle Reservoir, and local groundwater. In addition to water stored in the local groundwater basin, Zone 7 has acquired additional out-of-basin groundwater storage to help supply its service area during droughts. The State pumps State Water Project water from the Sacramento-San Joaquin Delta via the California Aqueduct, conveys it to the Valley via the South Bay Aqueduct, treats it at the Patterson Pass and Del Valle Water Treatment Plants in Livermore, and then sends it to Pleasanton via the Zone 7 Cross Valley and Vineyard Pipelines. Zone 7 stores water from the South Bay Aqueduct and from local runoff in the Del Valle Reservoir. Zone 7 uses this water to replenish groundwater supplies through release into the Arroyo Del Valle and Arroyo Mocho. Several sub-basins in the Tri-Valley area contain groundwater, the most important of which are located in the west-central area of the Valley where the major Zone 7 and City wells are located. Zone 7 distributes its water supplies to cities and unincorporated areas based on individual water delivery schedules. Acting as a water wholesaler, it sells water to PIeasanton, which as a retailer operates and maintains the water pumping, distribution and storage system to deliver this water to homes and businesses. In a typical year, Zone 7 provides Pleasanton with approximately 75- 80 percent of its water. The remainder is pumped through City-owned wells in accordance with a pumping schedule approved by Zone 7. The groundwater, pumped from City- and Zone 7-owned wells, is disinfected (using chloramines - a combination of chlorine and ammonia) and pumped into the City's water system generally during the summer months to meet peak-usage periods. PIeasanton fluoridates all water supplied to its customers at all times ofthe year. Pleasanton's annual groundwater entitlement is 3,500 acre-feet. This amount is fixed by contract with Zone 7, which acts as the regional groundwater basin manager for the Tri-Valley area. The entitlement is subject to negotiation when the City's contract with Zone 7 is renewed, although the City does not anticipate that future-pumping limits will change significantly. Thus, as the City grows, it will rely more on Zone 7 for the bulk of its water supply. Table VI-2 summarizes existing and projected annual water demand. Zone 7 projects that it can supply sufficient water to meet the City's future water needs, assuming that the State Department of Water Resources supplies approximately 75 percent of Zone 7's contractual allocation and that other planned and contracted water sources supplement this supply. These additional sources include more imported surface water, water transfers, out-of-basin groundwater storage, water conservation, water recycling, and enhanced conjunctive use of the groundwater basin. Zone 7 has purchased additional groundwater storage to enhance the reliability of water supply during drought periods. 4 Camp Dresser & McKee, Inc., for the City of Pleasant on, Water Distribution System Master Plan Update, November 2004. VI-IO