2025 Urban Water Management Plan

Section 6 2025 Urban Water Management Plan Water Supply Characterization City of Pleasanton Public Draft | May 2026 6-11 EKI Environment & Water, Inc. Each Zone 7 retailer has an established GPQ 12 that matches the sustainable yield averages shown in Table 6-1. Sustainable averages are maintained by allowance of “carryover”, which is limited to 20% of the GPQ (i.e., 700 AFY for the City), when less than the GPQ is used in a year. A retailer must pay a “recharge fee” for pumping groundwater more than its GPQ and any carryover. The fee covers the cost of importing and recharging additional water into the Main Basin. This practice helps avoid repeating historical trends in over-drafting the Basin. Historically, Pleasanton pumped its own GPQ; however, the City stopped operating its production wells in 2022 due to PFAS in the groundwater supply. Pleasanton is working with Zone 7 to construct and begin operation of new wells outside of the known PFAS contamination plume. The new wells are expected to come online before 2030 and will allow Pleasanton continue pumping its full GPQ. In terms of the other Zone 7 retailers: Cal Water pumps its own GPQ; Zone 7 pumps DSRSD’s GPQ; and Livermore has not utilized its GPQ for many years. The balance of the natural sustainable yield is pumped for other municipal, agricultural, and gravel mining uses. 6.2.3.2 Zone 7’s Groundwater Pumping and Monitoring Strategy Zone 7's groundwater production for its treated water system does not use the natural sustainable yield from the Main Basin; instead, Zone 7 pumps only water that has been recharged as part of its artificial recharge program using its available surface water supplies. During high-demand periods, groundwater is used to supplement surface water supply delivered via the SBA. Groundwater is also used when the SBA is out of service due to maintenance and improvements or when Zone 7’s surface water treatment plants (WTP) are operating under reduced capacity due to construction, repairs, etc. Finally, Zone 7 taps into its stored groundwater under emergency or drought conditions, when there may be insufficient surface water supply available. Zone 7 also pumps groundwater out of the Main Basin during normal water years to help reduce the salt loading in the Main Basin in accordance with the Salt Management Plan. 6.2.3.3 Artificial Recharge and Groundwater Extraction by Zone 7 Before the construction of the SWP in the early 1960s, groundwater was the sole water source for the Livermore-Amador Valley. This resource has gone through several periods of extended withdrawal and subsequent recovery. The Main Basin was over drafted in the early 1960s when approximately 110,000 AF of groundwater was extracted. The Main Basin was allowed to recover from 1962 to 1983. It was during this era that Zone 7 first conducted a program of groundwater replenishment by recharging imported surface water via its streams or arroyos (“in-stream recharge” or “artificial recharge”) for storage in the Main Basin, supplying treated surface water to customers to augment groundwater supplies, and regulating municipal pumping by other users. Zone 7 actively manages the Basin under a conjunctive use strategy designed to balance natural recharge, artificial recharge, and groundwater extraction. Zone 7's operational policy is to maintain the balance between the combination of natural and artificial recharge and withdrawal or pumping to maintain groundwater levels above the emergency reserve storage, thereby preserving a reliable drought buffer. Artificial recharge operations provide the ability to store surplus imported and local surface water during wet periods for later recovery during dry conditions, enhancing overall supply reliability. This conjunctive use framework allows Zone 7 to adaptively shift between surface water and groundwater sources depending on hydrologic conditions, operational needs, and regulatory constraints. Figure 6-3 shows Zone 7’s artificial recharge and pumping from 1974 through 2025. 12 The Groundwater Pumping Quota was formerly referred to as the “Independent Quota” in the original Municipal and Industrial Water Supply Contract between Zone 7 and each retailer.