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r.0/ ATC Associates Inc. <br /> 1117 Lone Palm Avenue, Suite 201 <br /> Modesto,California 95351 <br /> 209-579-2221 <br /> fax: 209-579-2225 <br /> AS SO C I ATE S I N C. <br /> ether (DIPE), tertiary amyl methyl ether (TAME), ethyl tertiary butyl ether (ETBE), 1,2- <br /> dichloroethane (1,2-DCA), and 1,2-dibromoethane (EDB) using EPA Method 8260B. — 14A)e' <br /> Additionally, selected vapor samples will be analyzed for methane by EPA Method 8015M and 4eeJ eg <br /> for oxygen and carbon dioxide by an appropriate EPA Method�tsing a gas chromatograph (GC) <br /> and/or a thermal conductivity detector(TCD). <br /> Soil samples will be immediately placed in a cooler with ice and delivered under chain-of- <br /> custody documentation to a State-certified analytical laboratory. Soil samples will be analyzed <br /> for TPHg by Method 8015; BTEX, MTBE, TBA, DIPE, TAME, ETBE, 1,2-DCA, and EDB by <br /> EPA method 8260B. <br /> Indoor Air Risk Assessment <br /> A tiered evaluation will be conducted using the laboratory analytical data. The soil vapor data ` <br /> will be compared to the values listed in Table 2 of the Tier 1 ESLs as published by the San <br /> Francisco Bay Regional Water Quality Control Board (SF RWQCB)in November 2007 and the <br /> California Human Health Screening Levels (CHHSLs) published by the California <br /> Environmental Protection Agency (CAL EPA) in January 2005. If any of the analytes of interest <br /> exceed the ESLs and/or CHHSLs, these analytes will be evaluated utilizing the Tier 2 Modeling <br /> program. ATC will use the Johnson and Ettinger Vapor Intrusion Model for Soil Vapor <br /> Emissions to Indoor Air Risk Assessment as appropriate for Residential Exposure Scenario for <br /> High Permeability (Sandy) Soils, version 1.0 (2005). Analytes of interest detected above <br /> laboratory method detection limits from vapor sampling will be inputted into the model to <br /> evaluate the Hazard Quotient for carcinogens and non-carcinogens. For the purpose of this <br /> indoor air risk assessment, ATC will assume the building is slab on grade. ATC will compare <br /> Hazard Quotient Ratios to conservative and action levels established by the SF RWQCB and <br /> evaluate if additional sampling and/or modeling is necessary. <br /> Report Preparation <br /> Upon completion of the soil vapor survey activities, a summary report will be prepared and will <br /> include a description of field activities, laboratory analytical data in tabular form, boring logs, <br /> site plans, laboratory report sheets, a comparison of soil vapor analytical data to the RWQCB San <br /> Francisco Bay Region ESLs and CHHSLs, and any additional modeling if necessary. <br /> Projected Schedule <br /> Once approval of this workplan has been received, ATC will confirm a schedule for drilling <br /> activities. ATC will notify SJCEHD at least 48 hours prior to beginning any field activities. The <br /> summary report will be submitted to SJCEHD approximately 60 days after the completion of all <br /> field activities. <br /> S:\Environmental\62605U2eports\2007 November.doe 5 <br />