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V <br /> ATC Associates Inc. <br /> YVATC <br /> 1117 Lone Palm Avenue,Suite 201 <br /> Modesto,California 95351 <br /> 60 209-579-2221 <br /> fax:209-579-2225 <br /> ASS O C I ATE S INC. <br /> V <br /> pg/m3, and 37 pg/m3) that exceeded the residential CHHSL for benzene, but not the <br /> commercial/industrial CHHSL for this constituent. None of the remaining analytes detected <br /> 4" exceeded their respective ESLs or CHHSLs. Maximum concentrations of the analytes detected <br /> along with corresponding ESLs. and CHHSLs are tabulated below. Copies of the ESLs and <br /> CHHSLs used for the Tier 1 evaluation are provided in Appendix C. <br /> 6' ESLs-Shallow Soil Shallow Soil Gas <br /> Gas Human Health <br /> Maximum Screening Levels Screening Levels <br /> Compound Concentration Location (pg/m3) (pg/m) <br /> (pg/M3) Tier 1 Com arison Vapor Intrusion <br /> Residential Com/Ind Residential Com/lnd <br /> Land Use Land Use Land Use Land Use <br /> 60 Freon 12 1.4E+01 SG-3 -- -- <br /> Acetone 9.2E+02 SG-4 6.6E+05 1.8E+06 -- -- <br /> Methylene Chloride 3.6E+00 SG-1 5.2E+03 1.7E+04 <br /> 6d Carbon disulfide 6.2E+01 SG-2 -- -- -- -- <br /> MTBE 6.4E+00 SG-1 9.4E+03 3.1 E+04 4.00E+03 1.34E+04 <br /> Benzene 6.3E+01 SG-1 8.4E+01 2.8E+02 3.62E+01 1.22E+02 <br /> 6' Toluene 2.1 E+02 SG-1 6.3E+04 1.8E+05 1.35E+05 3.78E+05 <br /> Tetrachloroethene 2.2E+01 SG-1 4.1 E+02 1.4E+03 <br /> Ethylbenzene 3.5E+01 SG-1 9.8E+02 3.3E+03 Postponed' Postponed' <br /> m,p-Xylene 1.1E+02 SG-1 2.1 E+04 5.8E+04 3.17E+05 8.87E+05 <br /> o-Xylene 3.1 E+01 SG-1 2.1 E+04 5.8E+04 3.15E+05 8.79E+05 <br /> 4-Ethyltoluene 5.7E+00 SG-1 -- -- -- -- <br /> L" 1,3,5- 7.1 E+00 <br /> Trimeth (benzene SG-1 -- -- -- -- <br /> 1,2,4- 2.0E+01 SGA -- -- -- -- <br /> �+ Trimeth (benzene <br /> 1. Calculation of a screening number for the chemical has been postponed until the toxicity <br /> criterion currently being developed by OEHHA is published as a final document. <br /> w <br /> Tier 2 Evaluation <br /> Modeling was conducted to assess the potential for vapor intrusion to 'indoor air space and <br /> applicable risks using the highest reported concentration of each constituent detected in the <br /> `0 vapor samples. Computerized spreadsheets sourced from the DTSC titled Vapor Intrusion <br /> Guidance Interim Final dated December 2004 and modified February 4, 2009, were used for <br /> this exercise. The indoor vapor intrusion exposure scenario was applied for clayey soils with a <br /> 6F slab-on-grade foundation. Default values for the observed soil type were included in the <br /> modeling process. The soil vapor sampling depth was four to five feet bgs. Sub-concrete slab <br /> soil vapor sample collection beneath the foundation of the existing restaurant building was not <br /> part of the proposed activities during this vapor assessment. Vapor intrusion modeling was <br /> r`. performed to estimate the cumulative risk from vapor intrusion to indoor air(carcinogen) and the. <br /> hazard index from vapor intrusion to indoor air (non-carcinogen). The incremental and <br /> S:1Environmenta11625771Reports\2011 Soil Gas.doc 6 ATC Associates Inc. <br /> 4r <br /> L <br />