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Page 3 January 24,2025 Brusca File No. 260-004 Additional Groundwater Monitoring Well Workplan substantially higher than previously detected in the wells.' Further, NAPL was detected in all three groundwater monitoring wells, with the greatest NAPL thickness being measured in monitoring well MW3 situated to the west and most distant from the former UST location. The fourth quarter 2024 groundwater monitoring results indicate variable NAPL conditions that may be transitory/seasonal and may be attributable to seasonal variations in irrigation pumping, particularly from an irrigation well situated about 1,000 feet westerly of the former UST location (see Plate 2). We understand that irrigation pumping from this westerly well was unusually high during the late summer and fall of 2024 due to hot and dry weather conditions. Upon review of the fourth quarter groundwater monitoring results, the CVRWQCB issued a letter dated January 16, 2025 that includes the requirement to install an additional groundwater monitoring well between well MW3 and the mentioned westerly irrigation well.' ADDITIONAL GROUNDWATER MONITORING WELL INSTALLATION General/Planned Location Three groundwater monitoring wells (identified as MWI, MW2, and MW3) currently exist at the site. As requested by the CVRWQCB, an additional groundwater monitoring well (MW4) is planned to be installed between well MW3 and the westerly irrigation well; the planned location of MW4 is shown on Plate 2. The groundwater well installation activities will be performed by a C57-licensed contractor. Permitting and Utility Clearance Prior to installation of the groundwater monitoring well, the necessary well permit will be obtained from the San Joaquin County Environmental Health Department (SJCEHD). Prior to drilling for well installation, the well location will be marked, and Underground Service Alert will be contacted to clear the location of underground utilities. Well Installation The planned groundwater monitoring well will be constructed within a minimum eight-inch diameter boring drilled with a truck-mounted drill rig using hollow-stem augers. The boring for the groundwater monitoring wells will extend to a total depth of 80 feet (about ten feet below the shallow groundwater level). Soil samples will be collected at five-foot depth intervals to the total depth of 80 feet for lithologic characterization. Drilling and well installation will be performed under the direct supervision of a Professional Geologist from our office who will log and classify the materials encountered. Construction of the additional groundwater monitoring well will be identical to the existing groundwater monitoring wells at the site. Two-inch diameter Schedule 40 PVC casing will be s Brusca Associates, Inc.; "Fourth Quarter 2024 Groundwater Monitoring, Anderson Barngrover Ranch Property, 14290 East Comstock Road,Linden, San Joaquin County,California";December 30,2024. 9 CVRWQCB; "Request for Work Plan and Evaluation of Risk to Supply Wells; Anderson Barngrover Ranch, 14290 East Comstock Road, Linden, San Joaquin County; Case#392009, Global ID#T10000020864"; January 16, 2025.