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City of Pleasanton Water Quality Division's Report on Water Quality Relative to Public Health Goals 2022 June 2022 -Page 5 of 8 Guidelines Followed The City of Pleasanton utilized the Association of California Water Agencies(ACWA) guidelines for preparing this PHG report. Currently there are no state guidelines available for preparing PHG reports. Best Available Treatment Technology and Cost Estimates Both the USEPA and DDW adopt what are known as Best Available Technologies (BATs), which are the best-known methods of reducing contaminant levels to the MCL. Some costs can be estimated for such technologies. However, since many PHGs and all MCLGs are set much lower than the MCL, it is not always possible nor feasible to determine what treatment is needed to further reduce a constituent downward from an MCL to or near the PHG or MCLG, many of which are set at zero. Estimating the costs to reduce a constituent to zero is difficult, if not impossible,because it is not possible to verify by analytical means that the level has been lowered to zero. In some cases, utilizing certain treatments to try and further reduce very low levels of one constituent may have adverse effects on other aspects of water quality. CITY OF PLEASANTON PHG COMPLIANCE Water Sources Zone 7 Water Agency provides approximately 80% of the water to the City of Pleasanton. About 50%of the water delivered to Pleasanton water customers is treated surface water(with 50% groundwater, generally in the summer months) purchased from Zone 7 of the Alameda County Flood Control and Water Conservation District. Zone 7 provides water to Tri-Valley water retailers and agricultural customers, as well as providing flood control and groundwater management to the Valley. Zone 7 sells treated surface water to the City of Pleasanton and three other larger water retailers in the Tri-Valley area who then distribute this water to their respective water customers. The remainder of Pleasanton's water supply comes from groundwater pumped from wells owned and operated by the City. One major source of the imported surface water delivered and treated by Zone 7 comes from the State Water Project(SWP). This water originally comes from the Feather River, where it is stored behind the Oroville Dam before being released into the Sacramento River/San Joaquin Delta. This water is transferred to the South Bay Aqueduct(SBA)and then flows 45 miles to the Tri-Valley area. The second source of surface water delivered and treated by Zone 7 is a combination of local surface water and imported SWP water stored in Lake Del Valle, located just south of Livermore. Lake Del Valle is owned and operated by the State Department of Water Resources (DWR)as a water supply reservoir and for flood control and recreation. Zone 7 operates two water treatment plants to treat all sources of surface water. Water from these plants does undergo several stages of filtration before it is disinfected and then delivered to the City and other valley retailers. 5