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4 �� Cardno� San Joaquin County Environmental Health Department ATO January 2,2013 Shaping the Future leaks within the above ground vapor probe assembly. The"dust-off'spray will be sprayed into a plastic bag containing several cotton cloth rags. The rags will be placed adjacent to, but not touching, each portion of the sample apparatus, including the area where the Teflon tubing exits the ground.The volatilizing leak-check compound will be present in the air surrounding the sampling assembly in sufficient concentrations to be pulled into the sample container through any vacuum leaks that may be present. If windy conditions persist during field activities, a shroud assembly surrounding the tubing and sampling manifold may be used instead. Upon completion,the vapor probe will be removed and the boring will be backfilled/grouted with neat Portland cement from the boring terminus to ground surface. Indoor Air Study IS �J ♦':' r7"` -' `� l, `I %z � td i J )I.f e>-,F .-C-1— , Cardno ATC then proposes to collect one indoor and one outdoor vapor sample using time release certified clean summa canisters. The indoor sample will be collected in the occupied area of the commercial structure on the site. The structure is in constant use as a business office, so a filter point similar to those used for sub-slab or soil vapor — sampling will be employed to keep incidental dust and airborne particles from entering the sample container. The summa canisters will collect samples over a period of six to eight hours. The purpose of the indoor air analyses will be to evaluate the potential degradation of indoor air quality compared to both the outside air and the projections obtained from modeling soil gas vapor data and to identify any volatile organic compounds(VOCs) being emitted �ry,r<rpCL into the building. The outdoor sample will be collected approximately 100 feet away from the site structure in the J prevailing up-wind direction over a similar duration as the indoor sample The outdoor sample will provide a baseline for atmospheric concentrations of the identified analytes of con c�re h��I t ��' �� 1 �� _ t ,•�; rlE�� Sample Analysis ,Pp Soil vapor samples c Ilected from t I por pr es and indoor air study will be immediately transferred under W chain-of-custody pr edures to a onsi tate-certi ied laboratory. Each soil vapor sample will be analyzed using EPA Method TO-1 . Each soil vapor sample will al o be analyzed for the leak check compound,with a method /detection limit of less than 10 Ng/I. Each sample wiI be screened at the laboratory to evaluate for elevated / S concentrations. EPA Method 8260B may be employ d for some samples to prevent an elevated dilution factor, which would affect the limit of some of the mpounds. For Quality Assurance/Quality Control purposes, a minimum of one duplicate sample will be collected i mediately after the original sample from a selected vapor probe location.-Each soiivapor sample will be properly abeled and submitted under chain-of-custody procedures. Indoor Air Risk Assessment A tiered evaluation will be c ducted using the laboratory analytical data. The soil vapor data will be compared to the values listed in Table 2 of the Tier 1 ESLs as published by the San Francisco Bay Regional Water Quality Control Board (SF RWQCB) in November 2007 and the California Human Health Screening Levels(CHHSLs) published 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. ATC will use the Johnson and Ettinger Vapor Intrusion Model for Soil Vapor Emissions to Indoor Air Risk Assessment as appropriate for Residential Exposure Scenario for High Permeability(Sandy) Soils, version 1.0 (2005). 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. For the purpose of this indoor air risk assessment, Cardno ATC will assume the building is slab on grade. Cardno ATC will compare Hazard Quotient Ratios to conservative and action levels established by the SF RWQCB and evaluate if additional sampling and/or modeling is necessary. www.cardnoatc.com