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Stockton Propeller Sampling and Analysis Plan 3.7 Groundwater Well Development and Sampling Monitoring well development will be done by first surging and water withdrawal with a bailer and pump. Development will continue until a total of approximately 100 gallons is purged, good water flow is noted, and pH and conductivity measurements stabilize.The pre-and post-development depth-to- water in each well will be measured and recorded. Prior to sample collection,the depth to water will be measured and approximately three (3) well casing volumes will be purged. Samples will be collected using a disposable bailer,transferred to laboratory- supplied glass vials, and placed in an ice-chilled cooler. Groundwater samples will be analyzed in the field for pH, electrical conductivity,temperature, and oxidation reduction potential (ORP) with instruments operated and calibrated according to the manufacturer's requirements. Groundwater samples will be placed in laboratory-supplied containers and transported to an ELAP- certified analytical laboratory under COC procedures in iced coolers and analyzed for the same analytes as described for soil (see Section 3.4).Additionally, samples will also be analyzed for total coliform and e. coli (Presence/Absence) using Standard Method 9223B. A duplicate groundwater sample will be collected from one of the groundwater sampling locations and analyzed to assess precision as measured by relative percent difference (RPD). Further, an equipment blank will be prepared during field activities and analyzed to assess impacts to laboratory results, if any, from the use of field sampling equipment. Laboratory accuracy will be assessed by evaluating percent recovery (%R)from laboratory control samples (LCS) and LCS duplicates (LCSD). The GPS coordinates of each well location will be recorded and will be reported along with analytical laboratory results in electronic deliverable format (EDF)to GeoTracker. A California Professional Land Surveyor(PLS) will survey the location and elevation of each well relative to a known or assumed benchmark to allow comparison of groundwater elevations to estimate groundwater gradient and direction. 3.8 Groundwater Well Abandonment Upon completion of the site investigation, and remedial action if any, monitoring wells will be abandoned according to the San Joaquin County Well Standards current at the time of proposed abandonment. 3.9 Investigation Derived Waste IDW such as soil cuttings and wash and purge water will be contained in 55-gallon drums, labeled and left on site. Disposal of IDW will be based on analysis of applicable samples. 4 Site Investigation Report After applicable tasks in Section 3 are complete, results will be documented in a draft Site Investigation Report and submitted to Board staff for review. Upon completion of Board review,the report will be finalized and uploaded to GeoTracker.The report will include a description of wells and borings, groundwater depth and gradient, sample collection methods,the results of analysis of samples, and analytical laboratory data.The report will also contain the results of septic tanks samples collected in December 2021, and recommendations for additional work if applicable. Results from the analysis of samples collected from the septic tank will be compared to California Code of Regulations (CCR),Title 22,section 66261.22 (characteristic of corrosivity) and CCR, title 22, Section 66261.24 (characteristic of toxicity). Blankinship&Associates, Inc. Page 19 of 20 September 23, 2022 NES, Inc.