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LMS solo, Soil Gas Investigation Work Plan Raymond Investment Corporation May 24,2006 Page 4 IV based on site-specific lithologic information, in accordance with the Advisory. The soil/building interface is anticipated to exist between 5 and 16 feet bgs in the proposed soil gas sampling area due to I" the building basement footprint. Therefore, soil gas sampling will be conducted at three depths in each boring, near the soillbuilding interface. The soil gas samples will be collected by qualified technicians and analyzed by Excelchem Environmental Laboratories in Roseville, CA. 4 The historical laboratory analytical data indicate that ethyl benzene, xylenes, gasoline, diesel, and mdthyl tertiary-butyl ether (MTBE) have been detected in soil samples collected at the Site. Based on the fact La that the UST was used for petroleum hydrocarbon storage and the historical laboratory analytical results, the chemicals of potential concern in soil gas include benzene,toluene, ethyl benzene,m,p and o-xylene, (BTEX),naphthalene, and MTBE. Wha* 16*p-t J;tLd— 1 L. \'? The general sample locations; sample types, constituents, and analytical methods are listed in Table 1, below. The proposed soil boring locations are shown in Figure 3, Appendix A. Ir. Table 1---Samples and Anal ses Location Depths Matrix Number of Constituents Methods 1 La I Samples 5 3 sample locations along 6, 11 16 feet BTEX 8260E-or TO-15 ti north and west sides of bgs Gas 9 Naphthalene, 8260B or TO-15 V building MTBE BTEX:Benzene(B),Toluene(1),Ethylbenzene(E),rn,p-Xylcne and o-Xylene(X) Le 3.2.2 Sampling Procedure A direct-push drilling method will be used to reach the desired sampling depth. Soil gas samples will be collected in gas-tight, laboratory supplied SUMMA canisters in accordance with the Advisory to protect the integrity of the samples. Prior to use at each soil gas sample location, all sampling equipment will be decontaminated in the field with a solution of laboratory-grade, non-phosphate detergent and deionized water and then rinsed twice. At least one duplicate sample will be collected and analyzed for the same constituents as its primary counterpart. 3.3 LABORATORY ANALYSES Excelchem Environmental Laboratories in Roseville, CA, a California certified laboratory, will conduct the analyses. Samples will be analyzed for BTEX, MTBE, and naphthalene at detection limits sufficient to perform the human health risk assessment. ' 4.0 REPORTING A Soil Gas Risk Assessment Report will be prepared for submittal to the SJCEHand CRWQCB �" D describing the results of the investigation. At a minimum the report will include: (1) an executive summary, (2) introduction, (3) Site description, (4) background information, (5) apparent problem statement, (6) environmental setting, (7) sampling activities and results, and (8) conclusions and �' recommendations. The Johnson and Ettinger model for subsurface vapor intrusion into buildings and current DTSC vapor intrusion guidance spreadsheets will be used to evaluate human health risk from soil �N gas concentrations. LA IV 4� L �1� CONDOR