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22 November 2023 AdvancedGeo Project No. 23-7523 An Employee-Owned Company Page 4 of 7 Q W closed after reaching 2 to 6 inches' mercury (Hg). The final pressure and time were recorded. The sampling ports on the sampling canisters were then capped with brass endcaps and the canisters were placed in a dry container (room temperature). Following sample collection, organic vapor in the wells was measured using a PID. Soil-vapor samples were labeled with sample ID, project name, date, time, and samplers' initials. The samples were logged on a chain-of-custody form and placed into dry containers. The soil-vapor samples were logged on a chain-of-custody form and delivered to Eurofins Air Toxics, LLC, (Eurofins), a California Environmental Laboratory Accreditation Program (ELAP)-certified analytical laboratory. Soil-vapor samples were analyzed for the following chemical constituents: • VOCs in accordance with EPA Method TO-15. • Helium in accordance with ASTM D1946M. 2.3. SUB-SLAB WELL INSTALLATION AND SAMPLING On 30 October 2023, sub-slab vapor implants SS-7 and SS-8 were installed in each of the two suites (306 and 308 North Ham Lane; Figure 1). The sub-slab soil gas implant was installed by drilling a 5/8-inch diameter hole completely through the foundation slab. Once the slab was penetrated approximately 1-to 2-inches into the underlying soil to form a void, the drill bit was removed, and the borehole was cleared. The slab thickness was measured and a 5/8-inch Vapor Pin® with silicone sleeve was inserted flush into the 5/8-inch drilled hole using a dead blow hammer to tap it into place and form an air-tight seal between the silicone sleeve and the slab. A protective plastic cap was placed on the Vapor Pin® to prevent vapor loss and it was allowed to re-equilibrate before sampling. 2.4. BORING ABANDONMENT Following sample collection, each boring was permanently sealed to prevent vertical migration of potential contaminants. Soil borings were abandoned by backfilling with Portland cement from the total depth to surface grade and patched to match the surrounding surface. 3.0. FINDINGS The soil and soil-vapor sample results are summarized in Tables 1 and 2, respectively. The laboratory reports (MAI Work Order No. 2310030 and BSK Associates report No. AGK0458; Eurofins Lab ID No. 2307097A and 2307098A), QA/QC reports and chain of custody forms are included in Appendix B. The following is a summary of the soil and soil-vapor analytical results from this investigation.