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Brusca File No. 137-002 Page 3 is May 2, 2018 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 April 2018 soil gas sample collected from SGMW1 contained a very low concentration of methane (0.00022%) which is well below levels of concern. The soil gas sample from SGMW2 did not contain methane at a concentration above the laboratory reporting limit of 0.00022% for that sample. Methane concern at the site is not indicated by April 2018 data. The soil gas samples collected from monitoring wells SGMW 1 and SGMW2 in April 2018 did not contain any of the tested VOCs at concentrations above the laboratory reporting limits, except that the SGMW1 sample contained very low concentrations of carbon disulfide and benzene (17 micrograms per cubic meter [ug/m3]) and 4.7 ug/m3, respectively). To evaluate the significance of the concentrations of carbon disulfide and benzene detected in the soil gas sample collected from SGMW 1 (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 Levels (RSLs) published by the US Environmental Protection Agency (USEPA), Screening Levels (SLs) developed by the California Department of Toxic Substances Control (DTSC) Office of Human Health and Ecological Risk (HERO), and Environmental Screening Levels (ESLs) published by the San Francisco Bay Regional Water Quality Control Board (SFBRWQCB). The applicable screening values for carbon disulfide and benzene are shown on Table I along with the analytical data from the soil gas monitoring wells. The published RSL and DTSC SL values are for indoor air VOC concentrations. For use in the screening evaluation for the subject site, the indoor air RSL and DTSC SL values have been adjusted by an attenuation factor of 0.001 to simulate the attenuation that could occur from soil gas to the indoor air environment. As shown on Table I, the concentrations of carbon disulfide and benzene detected in the soil gas sample from SGMW 1 are well below the commercial/industrial agency screening values considered, and, as such, are 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 April 2018. 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 April 2018 monitoring event (as well as all previous soil gas monitoring data) do not indicate elevated concentrations of