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Site Inspection UFP-QAPP Addendum Stockton AASF, Stockton, California temperature blank will be placed in each cooler to ensure that samples are preserved at or below 4 degrees Celsius (°C) during shipment. Each sample will be collected into laboratory -supplied bottleware and submitted to the laboratory for analysis of selected parameters. Samples will be analyzed for PFAS by liquid chromatography tandem mass spectrometry (LC/MS/MS) compliant with Quality Systems Manual (QSM) 5.3 Table B-15. Additionally, one soil sample per AOI from a location in the source area will be analyzed for total organic carbon (TOC) (USEPA Method 9060A) and pH (USEPA Method 9045D). Additionally, up to one soil sample per AOI will be submitted for grain size analysis with sieve and hydrometer (American Society for Testing and Materials [ASTM] D-422) (i.e., clay content). The grain size analysis will be performed where extensive horizontal and vertical clay units are identified by the field geologist, if these conditions are encountered in the field. All sample containers will be PFAS free. The laboratory method detection limits (DLs) for these analytes are presented in Worksheet #15. Samples will be packaged on ice and transported daily via overnight commercial carrier under standard chain of custody (CoC) procedures to the laboratory (see SOP 3-04). QAPP Worksheet #17c Sampling Design and Rationale Temporary Groundwater Monitoring Well Installation and Grab Groundwater Samples Boreholes for temporary wells will be created using a Geoprobe® DT45 or DT60 dual -tube sampling system (or equivalent). Once the borehole has been advanced to the specified depth, the temporary well will be constructed using a 5 -foot section of 1 -inch Schedule 40 poly -vinyl chloride (PVC) screen with sufficient casing to reach ground surface. New PVC pipe will be used for each sampling location. The target screen interval for each location will be the top of the groundwater table, which is expected to be encountered no deeper than 35 feet bgs at Stockton AASF. The proposed well locations are shown on Figures 17-1. The target screen intervals and rationale for the sampling locations are described in Table 17-3. Table 17-3: Groundwater Sample Rationale and Proposed Screen Intervals Notes: A01= area of interest bgs = below ground surface A grab groundwater sample will be collected at each temporary well using a peristaltic pump with tubing that has been determined to be PFAS-free (i.e. high-density polyethylene [HDPE] or other PFAS-free material). If the peristaltic pump cannot generate enough hydraulic lift to bring the groundwater to the surface, groundwater samples will be collected using a PFAS-free bladder pump or other sampling device. Prior to sampling, the temporary well will be purged in order to remove sediment, to the extent reasonable, in an effort to minimize the turbidity of the sample (see SOP 3-37: Grab Groundwater Sampling Techniques for additional details). The degree of purging will be dependent on groundwater recharge within the well. If sufficient groundwater recharge is observed, the well will be purged until the turbidity is <_ 25 nephelometric turbidity units AECOM QAPP Worksheet #17 Page 6 of 10 AOI 1 5 Top of groundwater table, Five temporary wells proposed adjacent to potential or (est. 30-35) suspected release areas. AOI 2 2 Top of groundwater table, Two temporary wells proposed (one downgradient of, (est. 30-35) and one within, the suspected release area) Top of groundwater table, Three temporary wells proposed (two downgradient of AOI 3 3 (est. 30-35) the suspected release area and one within soil backfill area) Notes: A01= area of interest bgs = below ground surface A grab groundwater sample will be collected at each temporary well using a peristaltic pump with tubing that has been determined to be PFAS-free (i.e. high-density polyethylene [HDPE] or other PFAS-free material). If the peristaltic pump cannot generate enough hydraulic lift to bring the groundwater to the surface, groundwater samples will be collected using a PFAS-free bladder pump or other sampling device. Prior to sampling, the temporary well will be purged in order to remove sediment, to the extent reasonable, in an effort to minimize the turbidity of the sample (see SOP 3-37: Grab Groundwater Sampling Techniques for additional details). The degree of purging will be dependent on groundwater recharge within the well. If sufficient groundwater recharge is observed, the well will be purged until the turbidity is <_ 25 nephelometric turbidity units AECOM QAPP Worksheet #17 Page 6 of 10