Evaluation of Groundwater Supply Alternatives Within Bernal Subbasin

Zone 7 Water Agency – Hansen Park Test Well Summary and Production Well Design Recommendations 1 Zone 7 Water Agency December 2025 1.INTRODUCTION Luhdorff and Scalmanini, Consulting Engineers (LSCE) have prepared this summary report documenting the hydrogeologic site investigation of Hansen Park in the City of Pleasanton and the construction and testing of the Hansen Park test well. The Hansen Park investigation was one of three site investigations conducted as part of the Regional Groundwater Facilities Project Feasibility Study, a joint project between Zone 7 Water Agency and the City of Pleasanton. Investigations and test well construction were also conducted at Del Prado Park and Tennis Park in the City of Pleasanton. The investigation of the Hansen Park site included drilling of an exploratory borehole to a depth of 770 feet below ground surface (bgs), construction of an eight-inch diameter test well completed to 766 feet bgs with five screen sections between 298 feet and 756 feet bgs, pump testing, flow profiling, and water quality sampling and analysis. This report also includes well production design and flow rate recommendations. 2.SITE SPECIFIC INVESTIGATION The primary purposes of the investigation of the Hansen Park site were to characterize subsurface lithology, characterize zonal water quality and flow characteristics, and collect the information necessary to design a sand-free and efficient well that could yield water in sufficient quantity and quality to meet project objectives. The Hansen Park site is located in the northwest corner of the park near the corner of Calle Ricardo and Hasen Drive in Pleasanton, CA (Figures 1 and 2). The Hansen Park test well was drilled and constructed by Nor Cal Pump and Well Drilling (Nor Cal) of Yuba City, California (CA C-57 License #908591). A copy of the permit for the drilling of the test hole and test well construction obtained from Zone 7 Water Agency is attached in Appendix A. A copy of the encroachment permit issued by the City of Pleasanton to work in the park is also included in Appendix A. Pump test development and pump testing was performed by North State Electric and Pump (North State) of Chico, California (CA C57 License #812678). A copy of the encroachment permit issued to North State by the City of Pleasanton is attached in Appendix A. Drilling commenced on March 18, 2025, and final well testing was completed on June 4, 2025. All work was conducted per project specifications and permitting requirements including traffic control, sound attenuation, and working hours unless variances were specifically granted by the City of Pleasanton. 2.1. Test Hole Drilling and Well Construction Nor-Cal drilled the test hole from ground surface to 770 feet bgs at a diameter of 8.75 inches using the direct rotary drilling method. Drill cuttings from the boring were collected at 10-foot intervals and described by LSCE Staff. Representative samples were collected in one-gallon resealable plastic bags and “chip trays”. A suite of geophysical surveys were conducted in the borehole (Appendix A) by Pacific Surveys of Claremont, California on March 21, 2025. Using the descriptions of the drill cuttings and the geophysical surveys, LSCE developed a lithologic log of the materials encountered in the test hole. The lithology encountered in the test hole and the geophysical logs are detailed on the attached test well as-