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29 January 2024 AdvancedGeo <br /> Project No. 23-7523 An Employee-Owned Company <br /> Page 5of8 n � <br /> three feet above the ground surface within the breathing zone. Indoor/outdoor air <br /> sampling locations are depicted in Figure 2. <br /> The sampling inlet on each canister was connected to a mass flow controller containing <br /> a particulate filter. The flow controllers were calibrated at the laboratory to a flow rate of <br /> 12.5 ml/min for collection of air samples over an 8-hour period. Each canister's initial <br /> vacuum was measured and recorded to ensure the initial vacuum was greater than <br /> 25 inches of mercury (in/Hg). Upon Summa canister retrieval, the vacuum measurements <br /> were recorded to ensure the final vacuum was below 5 in/Hg. <br /> Initial vacuum measurements were recorded from each Summa canister between <br /> 29 in/Hg and 29.5 in/Hg, while final vacuum measurements were recorded between <br /> 2 in/Hg and 4 in/Hg. <br /> The air samples were transported under chain-of-custody procedures to EAT, a California <br /> ELAP-certified laboratory. The indoor air samples were analyzed for VOCs in accordance <br /> with EPA Method TO-15 (Appendix B). <br /> 2.4. BORING ABANDONMENT <br /> Following sample collection, each boring was permanently sealed to prevent vertical <br /> migration of potential contaminants. Soil borings were abandoned by backfilling with <br /> Portland cement from the total depth to surface grade and patched to match the <br /> surrounding surface. <br /> 3.0. FINDINGS <br /> The soil and soil-vapor sample results are summarized in Tables 1 and 2, respectively. <br /> Indoor air sampling results are summarized in Table 3. The laboratory reports (MAI Work <br /> Order No. 2401576; Eurofins Lab ID Nos. 2401188A, 2401188B, and 2401195), QA/QC <br /> reports and chain of custody forms are included in Appendix B. <br /> The following is a summary of the soil and soil-vapor analytical results from this <br /> investigation. <br /> 3.1. ANALYTICAL RESULTS OF SOIL SAMPLES <br /> • The soil profile generally consisted of dry sandy silt or silty sand mixtures from near <br /> surface grade to 30 feet bsg. <br /> • Organic vapors were detected at concentrations ranging from 0.2 to 0.4 parts per <br /> million volume (ppmv). <br />