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Workplan for PFAS Sampling and Analysis Project Number:60657245 3 PFAS Sampling and Analysis A Programmatic Sampling and Analysis Plan (PSAP) is included in Appendix A. The following sections discuss site- specific elements of the sampling plan for this facility. Sampling equipment used to collect samples has been selected or modified to consist of PFAS-free materials and components to the extent possible, to avoid introducing PFAS substances into the sample collection process. Field quality control (QC)samples will also be collected, as indicated in Section 9.1 of the PSAP(Appendix A),to evaluate potential cross-contamination introduced by the field equipment or procedures. 3.1 PFAS Sampling Locations and Rationale The sampling program has been designed to take advantage of the existing monitoring well network and eliminate ground disturbing activities at the facility during this preliminary investigation, if possible. The objectives for this sampling event are to investigate the presence of PFAS at the Site. Sampling locations are shown on Figures 3-1 and 3-2 and summarized on Table 3-1. The STTC currently oversees a group of monitoring wells across the two terminal properties.All STTC wells are presented in Figure 1-4. 3.1.1 Soil and Groundwater Sampling The objective of soil sampling is to identify potential usage areas where PFAS-containing materials may have reached the ground. As such,shallow soil sampling is generally limited to unpaved areas that could have been directly impacted by foam use(e.g., where AFFF could run or blow off the edge of a paved area). Two shallow soil samples will be collected at the East Annex at the locations shown on Figure 3-1. These soil sample locations are adjacent to concrete pads where foam is stored, even though there was no use from this stored foam. Soil samples are proposed because of the proximity to the storage locations, as compared to existing groundwater monitoring wells at the East Annex.The soil samples will be collected between 1 to 2 feet bgs. The objective of the groundwater sampling is to collect representative samples of groundwater from the selected existing monitoring wells for PFAS and geochemical analysis. The groundwater sampling program has been designed to utilize existing monitoring wells for this evaluation. This work plan adopts the low-flow sampling methodology currently used at the Site, which allows collection of groundwater samples without unnaturally altering or stressing the aquifer. Existing downhole sampling tubing will be removed prior to sampling, per the PSAP. There are four groundwater monitoring wells proposed for sampling on the West Terminal property(Figure 3-2). Two wells (TS-1 R and TS-4R) are upgradient, one well (TS-9R) is downgradient, and one well (SP-5) is cross-gradient, relative to foam storage S1. Upgradient well TS-4R, downgradient well TS-9R, and cross-gradient well SP-5 are proposed to evaluate the contained use area U1 at the West Terminal truck loading rack. Well TS-1R also serves as an upgradient site boundary sample. The four proposed wells create a perimeter around the known storage and use areas. Therefore, soil samples are not proposed for the West Terminal. Stormwater samples are also not proposed because the selected groundwater wells TS-1 R and SP-5 are located in areas where stormwater accumulates. Well SP-5 has not been sampled in the last five years and will be redeveloped prior to sampling. Table 3-1 lists the groundwater monitoring wells that will be sampled and soil sampling locations as well as the sampling rationale. Wells were selected to be near storage areas identified in Section 2.1 or are located upgradient of these areas to investigate if other PFAS sources were present. 3.2 Sampling Sampling methodology, including sampling procedures, equipment and containers, and discussion of analytical methods, method detection limits, reporting limits, and field quality control samples are included in the PSAP. Prepared for:Tesoro Logistics Operations LLC AECOM 8