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Appendix A-Sampling and Analysis Plan BSK Project E19-016-01F Stockton Metropolitan Airport(SCK) March 1, 2023 Stockton, California Page S Excess drilling returns will be containerized in 55-gallon drums or a roll-off bin, awaiting disposal. 4.3.3.Groundwater Sampling of Monitoring wells Before purging and sampling each monitoring well is opened and allowed to equilibrate to atmospheric conditions for approximately 30 minutes. Once the monitoring wells have been allowed to equilibrate, static dept-to-water measurements are collected with a water level meter to the nearest 0.01-inch and noted on the sampler's field log. A decontaminated submersible pump is lowered into the well with disposable, or dedicated tubing approved for PFAS sampling.The well is purged of at least three(3)casing volumes, or until parameters have stabilized, up to five (5) well casings. The following water quality parameters are considered as stabilization criteria measured after each well casing volume is removed while purging. • ±3%for temperature, • ±0.1 for pH, • ±3%for conductivity, • ±10 millivolts (mV) oxidation reduction potential (ORP), • ±10%for dissolved oxygen (DO) and, • ±10%for turbidity. If three (3) of the six (6) parameters bulleted above are within the tolerances specified, (i.e., ±3% for temperature, ±0.1 for pH, ±3 %for conductivity, ±10 millivolts (mV) oxidation reduction potential (ORP), ±10%for dissolved oxygen (DO) and, ±10%for turbidity)for three (3) casing volumes, the groundwater in the monitoring well casing is considered stabilized, and groundwater samples are collected for chemical analysis. If groundwater does not stabilize after five (5) well casing volumes have been removed, the groundwater in the monitoring well casing will be considered stabilized,and groundwater samples will be collected for chemical analysis. Once the monitoring well has been purged at least three (3) well casing volumes and water quality parameters have stabilized, the submersible pump and associated tubing is removed, and a disposable bailer is lowered into the monitoring well with a non-PFAS cable. A new disposable bailer is used at each monitoring well when collecting samples for chemical analysis. All reusable equipment used during purging and subsequent sampling would be washed with a non- phosphate detergent solution, and thoroughly rinsed with distilled water before and after each well is sampled. Groundwater and QA/QC samples including any duplicates and equipment rinsate samples are labeled and placed into a chilled cooler immediately following collection. Samples are then transported under chain of custody protocol to an ELAP approved laboratory for analysis. S�l � &I