Evaluation of Groundwater Supply Alternatives Within Bernal Subbasin

Zone 7 Water Agency – Hansen Park Test Well Summary and Production Well Design Recommendations 4 Zone 7 Water Agency December 2025 Table 2. Step Testing Results Duration (min) Average Discharge Rate (gpm) Projected 24-Hour Drawdown (ft) Projected 24-Hour Specific Capacity (gpm/ft) 120 356 7.5 47.5 120 466 11.5 40.5 120 622 18.5 33.6 Long-Term Constant Rate Test An 8-hour constant rate pumping test was performed on June 3, 2025, to determine well and aquifer characteristics. The static water level measured prior to testing was 24.50 feet bgs. The discharge rate, pumping duration, projected pumping drawdown, and projected specific capacity of the test are included below in Table 3. The long-term constant rate test hydrograph is depicted in Figure 5. Table 3. Long-Term Constant Rate Test Results Duration (min) Average Discharge Rate (gpm) Projected 24-Hour Drawdown (ft) Projected 24-Hour Specific Capacity (gpm/ft) 480 594 19.5 30.5 2.3. Water Quality Water quality samples were collected by LSCE personnel from a dedicated sample tap on the well discharge assembly on June 2, 2025, for Title 22 drinking water constituent analysis and for other constituents of interest. Water samples were collected and handled according to the Testing, Sampling, and Analysis Plan (Appendix A) prepared for the project and standard industry practice. The results of the water quality analysis show that for the constituents analyzed, only benzo-a-pyrene and iron exceeded the respective maximum contaminant levels (MCL) (Table 4). All other constituents were below their respective MCLs. Perfluorohexanesulfonic acid (PFHxS), which has a MCL of 10 ng/l, was detected at a concentration of 2.73 ng/l. Appendix B summarizes the results of the Title 22 sampling. Table 4. Exceedances of Drinking Water Maximum Contaminate Levels Analyte Units MCL Result Benzo-a-pyrene µg/L 0.2 0.5 Iron mg/l 0.3 0.54 According to the US Environmental Protection Agency, benzo-a-pyrene is a polycyclic aromatic hydrocarbon that is formed as a result of incomplete combustion of organic materials from sources such as combustion engines, incinerators, cooking, and smoke. LSCE reviewed water quality records for all of Zone 7’s, City of Pleasanton’s, and SFPUC’s (Pleasanton) drinking water wells and found no detections of benzo-a-pyrene in any well. Before water from the well could be directed to the City’s stormwater system, it was tested for a number of contaminants, including benzo-a-pyrene, to determine if the water met the