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1 Phase Q ESA —Work Plan 2222&2244 S.Airport Way, Stockton,California October 27,2017 Page 3 4.3 DIRECT PUSH BORING FIELD PROCEDURES Each borehole will be drilled using a drilling rig equipped with 8-inch hollow stem augers to a depth of approximately 40 feet below ground surface (bgs). All down-hole equipment will be steam-cleaned prior to use. A geologist will log the boreholes using the Unified Soil Classification System or equivalent method. A detailed geologic log will be prepared for each borehole. A minimum of four soil samples will be collected and retained for analysis of potential constituents of concern by a state licensed analytical laboratory described in Section 6 on the following page. Soil samples will be collected during drilling for soil identification and possible analysis every five feet using a split spoon sampler lined with brass or stainless steel tubes. At minimum, soil samples collected at depths of approximately 1.5-2 feet, 4.5-5 feet, 9.5-10 feet bgs, and directly above first encountered groundwater(approximately 27-29 feet bgs) will be retained for possible analysis. Additional soil samples from specific depths may be retained for laboratory analyses if observations in the field (such as discoloration, odor and/or PID readings) suggest the potential presence of contamination. The excess cuttings will be contained in metal drums and disposed of at an approved landfill following laboratory analyses. The four (4) soil borings described above will be converted to groundwater monitoring wells to investigate potential impacts to groundwater from the historical operation of the former dry cleaner and nearby gas stations. Groundwater monitoring wells will be installed at the upgradient and downgradient property boundaries to evaluate potential contaminant migration on, to, and off the subject property, as well as at the former dry cleaner location to evaluate potential impacts. Each monitoring well will be installed to a depth of approximately 40 feet bgs, based on the known depth to groundwater in the area (approximately 27-29 feet bgs). If groundwater is not encountered at a depth of 40 feet or less, the borehole will be deepened by 5 feet; and the procedure repeated until first water is encountered. The wells will be constructed with approximately 15 feet of screened PVC piping, with appropriate intervals of filter pack and annular seal. The screened interval and filter pack will extend approximately 3 to 5 feet above the anticipated static groundwater elevation to allow for investigation of potential free phase petroleum hydrocarbons. Each well will be completed at the ground surface with a locking, protective box flush with the ground surface. Monitoring well construction will be completed in accordance with the California Department of Water Resources Bulletin 74-90: California Well Standards/Monitoring Well Standards, as well as the San Joaquin County Well Standards. Each soil sample retained for laboratory analyses will be capped at each end with with Teflon® sheeting and plastic end caps. Soil samples will be labeled,placed in chilled coolers, and transported under chain- of-custody procedures to BC Laboratories(ELAP# 118 6) in Bakersfield, California for analysis. 5.0 MONITORING WELL DEVELOPMENT AND SAMPLING 5.1 PROCEDURE The wells will be developed no sooner than 24 hours after construction by surging,bailing and pumping. Development will continue until the discharge water is relatively clear to the unaided eye and the temperature, electrical conductivity and pH of the water have stabilized. Prior to use, all well-development equipment will be cleaned by washing in a solution of laboratory-grade, non-phosphate detergent and potable water, and double rinsing with potable water. The purged groundwater will be contained in drums and left onsite pending laboratory analyses. Well development records and groundwater parameter readings will be recorded during the field work. Monitoring wells will be purged and sampled a minimum of 48 hours after well development. Samples retained for laboratory analyses will be contained in laboratory supplied and cleaned glass containers. Each container will be filled to t �i^ CONDOR