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Brusca File No. 137-002 Page 3 April 1, 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 March 2020 soil gas samples collected from SGMW1 and SGMW2 did not contain methane at a concentration above the laboratory reporting limits of 0.00023% and 0.00024% for these samples, respectively. Methane concern at the site is not indicated by the March 2020 data. The soil gas samples collected from monitoring wells SGMW1 and SGMW2 in March 2020 did not contain any of the tested VOCs at concentrations above the laboratory reporting limits, except for chloroform. As shown on Table I, the concentrations of chloroform detected in soil gas wells SGMW1 and SGMW2 were 24 micrograms per cubic meter (ug/m3) and 34 ug/m3, respectively. To evaluate the significance of the concentrations of chloroform detected in the soil gas samples (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 for chloroform are shown on Table 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 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 concentrations of chloroform detected in the March 2020 soil gas monitoring well samples slightly exceed the screening level considered (18 ug/m3). The source of the chloroform detected in the soil gas monitoring wells 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 the soil gas monitoring wells is attributable to landscape irrigation in the areas of the wells utilizing municipal water. Nonetheless, it is our opinion that the slightly elevated concentrations of chloroform detected at the soil gas monitoring well locations 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 underlain by a 12-inch section of cement treated subgrade. Given the