Evaluation of Groundwater Supply Alternatives Within Bernal Subbasin

REGIONAL GROUNDWATER FACILITIES PROJECT FEASIBILITY STUDY 7 Zone 7 Water Agency December, 2025 existing regional third party wells. A detailed discussion of test results, derivation of production rates, and methodology for estimating the performance of each well site under dry, average, and wet year conditions is provided in Appendix A, B, and C. Testing at Tennis Park indicated some of the highest potential yields among the three sites. Step- drawdown and constant-rate testing suggested an estimated production capacity ranging from 3,400 to 5,100 gallons per minute (gpm), depending on hydrologic conditions during dry, average, and wet year conditions. Hansen Park test well data showed similar favorable results, with sustainable yields in the range of 3,400 to 4,200 gpm. At Del Prado Park, pump testing demonstrated lower estimated yields of approximately 1,300 to 1,900 gpm. As discussed in Appendix C, the reduced performance at this site is believed to be largely attributable to different aquifer conditions near the edge of the groundwater basin and to a lesser extent, test well drilling construction issues (e.g. extended well development time). Table 1 summarizes the estimated production well flow rates at each of the three candidate sites. Table 1. Estimated Groundwater Production for Three Test Well Sitesa Test Well Site Design Flow Rate (gpm) Design Flow Rate (MGD) Tennis Park Drought Year Conditions 3,400 4.90 Average Year Conditions 4,250 6.12 Wet Year Conditions 5,100 7.34 Hansen Park Drought Year Conditions 3,400 4.90 Average Year Conditions 3,800 5.47 Wet Year Conditions 4,200 6.05 Del Prado Park Drought Year Conditions 1,300 1.87 Average Year Conditions 1,600 2.30 Wet Year Conditions 1,900 2.74 a Estimated production flow rates are based on exploratory test well drilling and aquifer testing conducted for this Study. Values represent preliminary planning-level estimates under drought-year, average-year, and wet-year hydrologic conditions, and are intended for feasibility-level evaluation only. Final design flowrates and overall project yield will likely vary from preliminary estimates and cannot be determined until final installation of full-scale production wells. These results confirm that multiple high-capacity wells can be developed to reliably meet Zone 7’s project objective of 7,000 AFY which includes an allocation of 3,500 AFY to meet the City’s GPQ. In combination, all three candidate sites are estimated to provide a design capacity of 8,100 to 11,200 gpm, which equates to an annual production range of roughly 9,800 to 13,550 AFY, assuming 18-hr daily runtimes. Several combinations of these wells as project alternatives are therefore capable of producing the minimum AFY targets required, and these configurations are carried forward as project alternatives for detailed evaluation in later sections of this Study.