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Brusca File No. 137-002 Page 3 December 2, 2019 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 November 2019 soil gas samples collected from SGMW1 and SGMW2 did not contain methane at a concentration above the laboratory reporting limits of 0.00024% and 0.00025% for these samples, respectively. Methane concern at the site is not indicated by November 2019 data. The soil gas samples collected from monitoring wells SGMW1 and SGMW2 in November 2019 contained chloroform at concentrations above the laboratory reporting limits. The SGMW1 sample also contained a low concentration of toluene. To evaluate the significance of the concentrations of these VOCs detected in the soil gas samples (p articularly w ith 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) and Environmental Screening Levels (ESLs) published by the San Francisco Bay Regional Water Quality Control Board (SFBRWQCB). The applicable screening values for chloroform and toluene are shown on Table I along with the analytical data from the soil gas monitoring well s. 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 attenuation factor of 0.03 to simulate the attenuation that could occur from soil gas to the indoor air environment. As shown on Table I, the concentration of toluene det ected in the November 2019 soil gas sample SGMW1 and the concentration of chloroform detected in sample SGMW2 do not exceed the listed commercial/industrial agency screening values considered and, as such, are not considered a concern. The soil gas sample collected from SGMW1 contained 190 ug/m3 chloroform which exceeds the screening level considered (18 ug/m3). The source of the chloroform detected in the SGMW1 sample is unknown. Chloroform occurs naturally in certain settings, although anthropogenic sources are responsible for much of the chloroform in the environment. A common anthropogenic source of chloroform in the environment is the discharge of chlorinated drinking water. It is possible that the detected chloroform in soil gas at the SGMW1 location is attributable to landscape irrigation in the area of SGMW1 utilizing municipal water. Nonetheless, it is our opinion that the elevated concentration of chloroform detected at the SGMW1 location would not represent an unacceptable vapor intrusion health risk at the onsite warehouse building, due to the distance to the building and the nature of floor slab system associated with the building. As mentioned above, the soil gas screening levels considered were developed using an attenuation factor of 0.03, which most certainly is excessively conservative considering that the floor slab for the onsite warehouse building is seven inches thick and is