Evaluation of Groundwater Supply Alternatives Within Bernal Subbasin

Zone 7 Water Agency – Hansen Park Test Well Summary and Production Well Design Recommendations 9 Zone 7 Water Agency December 2025 Blank Well Casing – Stainless steel was selected for the blank casing. Stainless steel will provide superior corrosion resistance and well longevity while meeting DDW standards for NSF 60 certification. The blank well casing shall be 24-inch I.D. by 3/8-inch wall ASTM A-778 Type 304L stainless steel. Well Screen – Stainless steel, louvered well screen was selected to maximize well open area and efficiency, and for compatibility with the blank well casing. The 24-inch I.D. well screen will be constructed ASTM A- 778, Type 304L stainless steel with a slot size of 0.080-inch. At a design capacity of 4,200 gpm, the screen will have a theoretical inlet velocity of 0.0346 feet/second. Accessory Pipes - A 2-foot-long, stainless steel sounding port shall be installed on the well casing from 297 to 299 feet bgs. A 2-inch, Schedule 40, Type 304L stainless steel sounding tube shall be connected to the sounding port and installed to a depth of 297 feet bgs. A 3-inch, Schedule 40, BSP gravel fill tube shall be installed to a depth of 280 feet bgs. Gravel Envelope – Based on the sieve analysis of selected formation samples (Figure 7), a 6 x 9 graded gravel envelope material was selected for use in this well. The gravel chosen is 5.1 times larger than the finest formation sample (515-520 feet bgs) at the d70 (cumulative percent retained) value. The 0.080-inch screen slot size will retain over 90 percent of the gravel material. The gravel envelope will be placed from 262 to 775 feet bgs. A two-foot, fine sand transition seal will be placed from 260 to 262 feet bgs. Annular Seal – The deep annular seal will ensure that only groundwater from the targeted intervals will enter the well structure. The annular seal shall consist of “10.3-sack” sand/cement grout and shall be placed from a depth of 260 feet bgs to the ground surface. Based on recent projects of similar size and scope, LSCE’s preliminary Engineer’s Estimate for the well construction, development, and testing is approximately $2,000,000. Items such as water supply for drilling, fluid and cutting disposal, development water disposal, material and equipment storage, sound attenuation, working hours and site security and safety that may affect the cost of well installation and testing will need to be addressed in the final specifications before bidding. Alternate Well Design Considerations Well design recommendations were based on direction to maximize well yield. The recommended well design includes screens placed opposite each zone identified in the test well borehole below a depth of 300 feet. Development of well capacity estimates assumed that each zone screened in the test well would be targeted for completion in a production well. The projected yield of the proposed Hansen Park Well constructed as recommended above is between 4,200 and 3,400 gpm, depending on long term and seasonal water level variations and a conservative well efficiency value as discussed in the TM (attached). Based on dynamic flow testing conducted in the test well, the bottom three zones (605 - 755 feet) in the well contribute 15% of the total well yield or between 647 and 524 gpm of the projected yield of the production well. In contrast, the upper two zones in the production well would contribute 85% of the well yield, or 3,553 to 2,876 gpm. The estimated cost to drill, construct, and test the production well as recommended above is $2,000,000, which equates to $2,545 per foot for a 775 foot well. The estimated cost to construct a well that targets