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3.0 FIELD ACTIVITIES The Additional Subsurface Investigation scope included the advancement of four borings (131 through 134) and the installation of two temporary sub-slab soil gas probes (SS-5 and SS-6) to facilitate the collection and analysis of soil, groundwater, and/or soil gas samples, as well as the collection and analysis of four indoor air samples (IAQ-1 through IAQ-4) and one ambient air sample (AMB-1). Refer to Table 1 for a summary of the borings, sampling schedule, and laboratory analyses for this investigation. 3.1 Preparatory Activities Prior to the initiation of fieldwork, Partner completed the following activities. 3.7.1 Utility Clearance Partner delineated the work area with white spray paint and notified Underground Service Alert (USA) to clear public utility lines as required by law at least three business days prior to drilling activities. USA issued ticket number 2023070400098-000 for the project. In addition, Partner subcontracted with Ground Penetrating Radar Systems (GPRS) on July 6, 2023 to clear boring locations of utilities. GPRS systematically free-traversed each proposed boring location with a Radiodetection model RD7000 electromagnetic induction (EM) equipment unit with line-tracing capabilities, and a GSSI model SIR-3000 ground penetrating radar (GPR) unit. The data was interpreted in real time for evidence of utility lines and/or other subsurface features of potential concern. Based on the findings of the GPR survey, no subsurface utilities were identified within the proposed boring locations. 3.1.2 Permitting Prior to drilling, Partner secured Permit Number WP0044567 from the San Joaquin County Environmental Health Department for the sampling activities. Refer to Appendix B for a copy of the permit acquired for this investigation. 3.1.3 Health and Safety Plan Partner prepared a site-specific Health and Safety Plan,which was reviewed with on-site personnel involved in the project prior to the commencement of drilling activities. 3.2 Drilling Equipment On July 6 and 7, 2023, Partner subcontracted with Environmental Control Associates (ECA) (State of California Water Well Drilling Contractor License Number 695970) to provide and operate drilling equipment. Under the direction of Partner, ECA advanced borings 131 and B2 with a truck-mounted Geoprobe Model 6610 direct-push rig and borings B3 and B4 with a limited-access Geoprobe Model 54LT direct-push rig. Additionally, ECA installed temporary sub-slab soil gas probes SS-5 through SS-6 with a hand-held rotary hammer drill with a 'h-inch drill bit. Sampling equipment was decontaminated between sample intervals and boring locations to prevent cross-contamination. 3.3 Sample Locations Borings 131 and B2 were advanced on the west and east exteriors of the former dry cleaning facility (Suite 308A), respectively. Borings B3 and B4 were advanced in the southeast and northeast interior areas of the Additional Subsurface Investigation Report PARTNER Project No.23-400162.14 July 31,2023 Page 4