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Brusca File No. 137-002 Page 3 September 28, 2020 Murphy Parkway Property Soil Gas Monitoring SOIL GAS LABORATORY TESTING The soil gas samples collected from soil gas monitoring wells SGMW1 and SGMW2 were transported to a State-certified laboratory for analysis. Both soil gas samples were analyzed for methane, oxygen, carbon dioxide, and nitrogen by ASTM Method D1946. The samples also were analyzed for VOCs by EPA Test Method TO-15. The analytical laboratory results are summarized on the attached Table I, along with data from past monitoring. The laboratory reports, internal laboratory QA/QC data, and chain-of-custody documentation also are attached. RESULTS AND DISCUSSION As shown on Table I, the September 2020 soil gas samples collected from SGMW1 and SGMW2 did not contain methane at a concentration above the laboratory reporting limits of 0.00025% and 0.00024, respectively. Methane concern at the site is not indicated by the June 2020 data. The soil gas samples collected from monitoring wells SGMW1 and SGMW2 in June 2020 did not contain any of the tested VOCs at concentrations above the laboratory reporting limits, except that both samples contained low concentrations acetone and tetrahydrofuran. To evaluate the significance of the concentrations of acetone detected in the soil gas sample s (particularly with respect to the potential for vapor intrusion into indoor air spaces at concentrations that could be considered a human health concern), we have considered Regional Screening Level s (RSLs) published by the US Environmental Protection Agency (USEPA) and Environmental Screening Levels (ESLs) published by the San Francisco Bay Regional Water Quality Control Board (SFBRWQCB). The applicable screening values are shown on Tab le I along with the analytical data from the soil gas monitoring wel ls. The published RSL values are for indoor air VOC concentrations. For use in the screening evaluation for the subject site, the indoor air RS L values have been adjusted by an attenuat ion factor of 0.03 to simulat e the attenuation that could occur from soil gas to the indoor air environment. As shown on Table I, the concentrations of acetone detected in both so il gas samples are below the published screening levels, and as such, are not considered a concern. Screening levels have not been established for tetrahydrofuran; however, the tetrahydrofuran concentration detected in the soil gas samples are very low and is not considered a concern. SUMMARY AND CLOSING As described herein, our firm conducted monitoring/sampling of the two soil gas monitoring wells (SGMW1 and SGMW2) at the subject property in September 2020. The purpose of the soil gas monitoring program is to evaluate whether soil gas contaminants, including methane and VOCs, exist at the westerly margin of the property as a result of uncharacterized subsurface wastes that reportedly exist offsite to the west of the subject property. Data from the September 2020 monitoring event do not indicate concentrations of methane or VOCs in soil gas at the monitoring well locations that are considered a concern. The next monitoring event will take place in the fourth quarter of 2020.