Evaluation of Groundwater Supply Alternatives Within Bernal Subbasin

Page 5 57.2 gpm/ft times the available drawdown of 120 feet yields an interim well capacity calculation of 6,900 gpm. Applying a well efficiency factor of 50% yields a final lower-end well yield estimate of approximately 3,400 gpm (Table 4). Hansen Park Well Capacity Estimate The upper end well capacity estimate for the Hansen Park test well is summarized in Table 4. The average pumping rate of 594 gpm combined with a projected 24-hour drawdown of 19.5 feet yields a specific capacity of 30.5 gpm/ft. The April 2025 static water level of 24.5 feet below ground surface (bgs), combined with depth to top of first screen of 298 feet bgs, yields an available drawdown of 273.5 feet. Multiplying the specific capacity of 30.5 gpm/ft times the available drawdown of 273.5 feet yields an interim well capacity calculation of 8,300 gpm. Applying a well efficiency factor of 50% yields a final upper- end well yield estimate of approximately 4,200 gpm. The lower end well capacity estimate is based on the same specific capacity, top of upper well screen, and well efficiency calculations/assumptions as summarized above. However, the April 2025 static water level of 24.5 feet bgs was substituted with a drought year assumed depth to water of 75 feet bgs based on review of groundwater elevation contour maps for 2021 and 2022, which yields an available drawdown of 223 feet compared to 273.5 feet for the upper end well capacity calculation. Multiplying the specific capacity of 30.5 gpm/ft times the available drawdown of 223 feet yields an interim well capacity calculation of 6,800 gpm. Applying a well efficiency factor of 50% yields a final lower-end well yield estimate of approximately 3,400 gpm (Table 4). Table 4. Summary of Test Well Pumping Capacity Estimates tĞůů/ Proposed Top of Screen (ft bgs) 24-Hr Q/s (gpm/ft) ,ŝŐŚ Available ;ĨƚͿ Low Available ;ĨƚͿ Assumed Well Efficiency (%) ,ŝŐŚ Pumping Capacity (gpm) Low Pumping Capacity (gpm) Tennis Park 195 57.2 178 120 50 5,100 3,400 Hansen Park 298 30.5 273.5 223 50 4,200 3,400 Del Prado Park 170 16.2 153 105 75 1,900 1,300 Comparison to Existing Production Well Capacities A summary of pumping test data available from DWR WCR for other production wells in the general project area is provided in Table 5. The range of specific capacities for these existing wells ranges from 10 to 123 gpm/ft, compared to a range of specific capacities from 16 to 57 gpm/ft for the new test well sites. Thus, the new test well sites are consistent with existing sites in terms of specific capacity.