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5 Workplan for Soil Gas Study—Subslab Sampling Cardno� 807 N. Hunter Street Stockton,California November 25,2014 ATC Shaping the Future • chloroethane • trichlorofluoromethane • 1,1-dichloroethene • 1,1,2-trichloro-trifluoroethane • methylene chloride • trans-1,2-dichloroethene • 1,1-dichloroethane • cis-1,2-dichloroethene • 1,1,1-trichloroethane • carbon tetrachloride • 1,2-dichloroethane • trichloroethene • 1,1,2-trichloroethane • 1,1,1,2-tetrachloroethane • 1,1,2,2-tetrachloroethane 4 HUMAN HEALTH RISK ASSESSMENT 4.1 CHHSL Screening Should it become necessary, Cardno will conduct a tiered evaluation using the laboratory analytical data. The soil gas data will be compared to the values listed in Table E of the Tier 1 ESLs as published by the San Francisco Bay Regional Water Quality Control Board (SF RWQCB) in November 2007 and the Table 2 California Human Health Screening Levels (CHHSLs) published in by the California Environmental Protection Agency (CAL EPA) in January 2005. If any of the analytes of interest exceed the ESLs and/or CHHSLs, these analytes will be evaluated utilizing the Tier 2 Modeling program. 4.2 Johnson and Ettinger Modeling Cardno will use the appropriate Johnson and Ettinger Vapor Intrusion Model based on subsurface soil encountered and property usage to estimate the cumulative risk of exposure to all applicable analytes of interest using site- specific data. Analytes of interest detected above laboratory method detection limits from vapor sampling will be inputted into the model to evaluate the Hazard Quotient for carcinogens and non-carcinogens. Analytes of interest not detected will be inputted into the model using the lowest applicable laboratory method detection limit. For the purpose of this indoor air risk assessment, Cardno will assume the building is slab on grade unless field data indicate otherwise. Cardno will compare Hazard Quotient Ratios to conservative and action levels established by the SF RWQCB and evaluate if additional sampling, modeling, and/or mitigation efforts are necessary. REPORT PREPARATION Upon completion of the soil gas study activities, Cardno will prepare a summary report which will include a description of the field activities, laboratory analytical data in tabular form, site plans, laboratory report sheets, a comparison of soil gas analytical data to the RWQCB San Francisco Bay Region ESLs, CHHSLs, and any additional modeling, if necessary. PROJECTED SCHEDULE Cardno ATC has tentatively scheduled field work for December 9, 2014 and will confirm that this date is acceptable with the SJCEHD prior to beginning any field activities. www.cardnoatc.com