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Transformer Oil Release Clean-up and Closure Report 1049 South Wilson Way, Stockton California 2.2.2 Phase 1 Verification Sampling and Results PG&E worked with Arcadis to develop a sampling grid (Figure 2) to guide the clean-up verification sampling of the approximate excavation area. The sampling grid was developed in accordance with the requirements established in 40 Code of Federal Regulations Part 761, Subpart 0 - Sampling to Verify Completion of Self-Implementing Clean-up and On-Site Disposal of Bulk PCB Remediation Waste and Porous Surfaces in Accordance With § 761.61(a)(6)). The sampling grid encompassed the impacted paved horizontal surfaces, which included areas of the asphalt-paved street (South Wilson Way), concrete-paved sidewalk (on the west side of South Wilson Way), and asphalt-paved parking lot (on the 1049 South Wilson Way property), plus a minimum 2-foot buffer around these impacted areas. The sampling was developed with consideration to the observed oil spill and droplets observed at the time of the oil release. The predominant wind direction recorded on July 27 and 28, 2021, was from the northwest, as shown on the wind rose diagram included as Appendix C. August 11, 2021 — Arcadis mobilized to the site with a PG&E representative to coordinate clean-up verification sampling of the spill. Arcadis collected six asphalt subsamples, designated BlA through B1 F, from areas of the asphalt- paved street where spilled oil was previously observed. These six asphalt subsamples were analyzed discretely. Four duplicate asphalt subsamples were also collected at the BlA, B1B, BlE, and BlF locations and analyzed discretely. In addition, the BlA through BlF subsamples were composited into a separate 6-point composite asphalt sample by the laboratory, which was identified as sample Bl-Comp and analyzed separately. Arcadis collected 32 asphalt subsamples from other asphalt-paved street and parking lot areas. These asphalt subsamples were then composited into eight samples for analysis, using a 4-point subsample grid for each composite. For example, subsamples were collected at 4-point grid locations AlA through AID; these four subsamples were then composited into a single sample at the laboratory, which was identified as sample Al-Comp. The seven other 4-point asphalt subsample grid locations were CIA through CID (analyzed as Cl-Comp), DIA through D1D (analyzed as Dl-Comp), ElA through El D (analyzed as El-Comp), HlA through H1D (analyzed as Hl-Comp), I1A through I1D, (analyzed as 11-Comp), J1A through J1D (analyzed as Jl-Comp), and KlA through KID (analyzed as Kl-Comp). Arcadis collected eight concrete subsamples from concrete-paved sidewalk areas. These concrete subsamples were then composited into two samples for analysis, using a 4-point subsample grid. The two 4-point concrete subsample grid locations were designated as FlA through Fl D (analyzed as Fl-Comp) and GlA through GlD (analyzed as Gl-Comp). The asphalt and concrete subsamples were collected from the surface of the pavement, using a rotary hammer with a chisel bit. Arcadis collected one wipe sample (W1) from a non-porous surface in the pipe of the storm drain. A duplicate wipe sample was also collected at this location. All samples were placed in ice-chilled coolers and transported under proper chain of custody protocol to Excelchem for PCB analysis by USEPA Method 8082. The analytical results are summarized in Tables 1 and 2. arcadis.com Stockton Release Closure Report 071362022 3