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5 Gardno° <br /> San Joaquin County Environmental Health Department ATC <br /> March 6,2013 Shaping the future <br /> Indoor Air Risk Assessment <br /> A tiered evaluation will be cc nducted using the laboratory analytical data. The soil vapor data will be compared to <br /> the values listed in Table E of the Tier 1 ESLs as published by the San Francisco Bay Regional Water,Quality <br /> Control Board (SF RWQCB) in November 2007 and Table 2 of the California Human Health Screening Levels <br /> (CHHSLs) published by the California Environmental Protection Agency(CAL EPA) in January 2005. If any of the <br /> analytes of interest 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 Emissions to Indoor Air Risk <br /> Assessment as appropriate for Residential Exposure Scenario for High Permeability(Sandy) Soils, version 1.0 <br /> (2005). Analytes of interest detected above laboratory method detection limits from vapor sampling will be inputted <br /> into the model to evaluate the Hazard Quotient-for carci ogens and non-carcinogens: For the purpose of this <br /> indoor air risk assessment, Cardno ATC will assume th building is slab on grade. Cardno ATC will compare <br /> Hazard Quotient Ratios to conservative and action lev s established by the SF RWQCB and evaluate if additional <br /> 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 include a description <br /> of field activities, laboratory analytical data in tabular form, boring logs, site plans, laboratory report sheets, a <br /> comparison of soil vapor analytical data to the RWQCB San Francisco Bay Region ESLs and CHHSLs, and any <br /> additional modeling if necessary. The report will include the inventory of potentially interfering chemicals found in <br /> the office as described above and a diagram of the interior of the office building including doorways, chemical <br /> storage areas, and an indication of the direction of the prevailing winds in the site vicinity. <br /> Projected Schedule <br /> Once approval of this workplan has been received, Cardno ATC will confirm a schedule for drilling activities. <br /> Cardno ATC will notify SJCEHD at least 48 hours prior to beginning any field activities.:The summary report will be <br /> submitted to SJCEHD approximately 45 days after the completion of all field activities. <br /> i <br /> www.cardnoatc.com <br /> i <br />