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City of Pleasanton Final Water Supply Assessment Stoneridge Drive Specific Plan Amendment and Staples Ranch Project 1 0.40411412.01 aup«weon kI W5&doo 5 -1 4.0 Water Agency Background 5.0 Water Agency Background This section presents a discussion of Zone 7 Water Agency's service area in the Tri- Valley region. Also included is a discussion of the City of Pleasanton's service area. The Alameda County Flood Control and Water Conservation District (ACFCWCD) was established by the State Legislature in 1949 to solve problems of flooding, drainage, channel erosion, and water supply and conservation in Alameda County. Zone 7, one of the 10 active zones of the ACFCWCD, was established by popular vote of the residents of Alameda County in 1957 and encompasses the area comprising the southeastem portion of Alameda County. Zone 7's principal activities include water supply, water resources management, flood control, and groundwater basin management. Zone 7 regulates withdrawal and recharge of the underlying groundwater basin and functions as the water wholesale provider to the Tri- Valley area. Zone 7 distributes primarily potable (treated) water supplies to the cities of Pleasanton and Livermore, and to the Dublin -San Ramon Services District (DSRSD), CWSC of Livermore, and some unincorporated areas of the county and agricultural areas. Treated water deliveries are based on individual water delivery schedules from these four water retail agencies, submitted on an annual basis, but also forecasted over the future five -year period. Zone 7 also serves untreated water to the agricultural industries here in the Livermore Amador Valley. 5.1 Zone 7 Water Service Area The service area managed by Zone 7 (see Figure 3) encompasses 425 square miles of the Livermore Amador Valley, Sunol Valley, and portions of the Diablo Range. The boundary extends to the eastem portion of Alameda County. Located about 40 miles south -east of San Francisco, where 1 -680 and 1 -580 intersect, the service area remains in a state of rapid growth. Currently, Zone 7 serves 190,000 residents spread through the cities of Pleasanton, Livermore, Dublin, portions of San Ramon and residents in the unincorporated areas of Alameda County. On a larger scale, Zone 7's service area lies within the Alameda Creek Watershed. This watershed encompasses almost 700 square miles and extends in the east to Altamont Pass, west to Union City on the San Francisco Bay, north to Mount Diablo and south to Mount Hamilton. Major streams in the Alameda Creek Watershed include the Arroyo Valle, Arroyo Mocho, Arroyo Las Positas, Alamo Canal, and South San Ramon and Tassajara Creeks. Arroyo Valle and Arroyo Mocho both originate in the woodland forests of the Bumt Hills region of Santa Clara County above Lake Del Valle. These streams have the largest drainage areas within Zone 7's service area. In addition, both streams are components of Zone 7's groundwater recharge program. The Arroyo Valle flows into Lake Del Valle above Lang Canyon, then flows out below the Del Valle Dam and continues a journey westerly through a regional park on the southem border of Livermore and into Pleasanton. Its path continues southwesterly through the historic downtown region of Pleasanton and finally joins the Arroyo de la Laguna. The Arroyo Mocho remains a natural waterway flowing southwest through the oak woodlands east of Livermore. It then flows through the southem portion of Livermore, then out through the gravel mining area west of Livermore where it joins the Arroyo Las Positas at El Charro Road, just southeast of the Project site. The Arroyo Las Positas mainly flows westerly along 1 -580. The major tributaries of the Arroyo Las Positas include the Arroyo Seco, Altamont Creek, Cayetano Creek, Collier Canyon Creek, and