Evaluation of Groundwater Supply Alternatives Within Bernal Subbasin

Zone 7 Water Agency – Hansen Park Test Well Summary and Production Well Design Recommendations 3 Zone 7 Water Agency December 2025 After receiving approval of the test well design by Zone 7, reaming of the test hole to a diameter of 14.75 inches to a depth of 770 feet bgs began. During reaming operations, upper borehole stability and caving of formation materials were encountered. Drilling tools were removed from the borehole to prevent the drill stem and bit from being struck in the borehole. A caliper log was performed in the borehole which indicated the borehole was filled with formation materials and that the likely source of that materials were washouts above 100 feet bgs. In order to proceed with well construction, LSCE recommended to Zone 7 that a conductor casing be installed to a depth of 100 feet bgs and cemented into place to stabilize the upper formations. After receiving approval from Zone 7 for the installation of the conductor casing, Hogg Drilling (CA C-57 License #829276), working as a subcontractor to Nor-Cal, advanced a 30-inch diameter borehole to 100 feet bgs using the bucket auger drilling method. An 18-inch diameter conductor casing was installed to 100 feet and cemented into place with cement grout. After letting the seal material cure, Nor-Cal reamed the remaining pilot hole from 100 feet bgs to 770 feet bgs to a diameter of 14.75- inches with no further issues. A copy of the Well Completion Report is attached in Appendix A. 2.2. Well Development and Testing Initial development of the well was performed by open-ended airlifting from the bottom of the casing assembly, followed by swab/airlift development by Nor-Cal. Final developmental pumping was performed with a submersible test pump by North State. Starting on April 28, 2025, the drill string was installed to the bottom of the casing, and the well was airlifted open-ended. Between April 29 and May 5, 2025, a swab isolation tool was used to swab/airlift each well screen. The screened sections were swabbed/airlifted from the top screen section to the bottom screen section, and then from the bottom screen section to the top screen section over multiple passes. All fluids generated during airlift operations were contained and disposed of offsite by Nor-Cal. After airlift operations were completed, LSCE collected water samples from the well for analysis of volatile organic compounds (VOCs), fuel additives, semi-volatile organic compounds (SVOC’s), polycyclic aromatic hydrocarbons (PAHs), and metals listed in NPDES Permit No. CAG912002. A summary table of analytes and analysis results is included Appendix A. Only after the results of the water testing and discharge plan (Appendix A) were accepted by the City of Pleasanton, was water discharged to the City’s storm water system. North State installed a temporary submersible pump in the well on May 28, 2025, to perform pump and surge development of the well and to conduct well testing. Between May 28, 2025, and May 30, 2025, the well was developed at rates between 200 and 650 gallons per minute (gpm) Step Test Step testing was performed on June 2, 2025, and consisted of three (3) steps. The static water level in the well measured prior to testing was 25.50 feet bgs. The discharge rate, pumping duration, projected pumping water drawdown, and projected specific capacity of the test are included below in Table 2. The step test hydrograph is depicted in Figure 4.