ARCHIVED REPORTS_TEMPORARY SOIL GAS PROBE PERMIT APPLICATION PACKAGE

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' 6 SOIL GAS SAMPLING The soil gas sampling will be conducted in accordance with the DTSC draft document entitled ' Advisory-Active Soil Gas Investigations, dated March 2010. 6.1 PRE-FIELD ACTIVITIES Prior to the commencement of field activities, Miller Brooks will verify that all proper underground utility clearances will be conducted. The proposed sampling locations will be identified using ' white paint, and the Underground Services Alert (USA) will be notified at least 48-hours prior to initiation of field activities. The appropriate permits from the San Joaquin County Environmental Health Department will also be obtained by Miller Brooks prior to the implementation of field ' activities. In addition, the DISC will be notified at least 10 days prior to the implementation of field activities. ' 6.2 SAMPLING RATIONALE The soil gas survey at the Site will be used to evaluate the potential for VOCs affect future on- Site industrial workers. As discussed above, previous investigations have detected VOC impacts within isolated shallow soil samples and in some groundwater samples. The entire site will be excavated to approximately 2 to 3 ft bgs in depth. The soil gas sampling will focus on VOC ' sources within the shallow subsurface of the soil. After reviewing analytical results from the supplemental site assessment, the DTSC ' recommended sampling areas of known impact (UST-1, MW-2, MW-3, and Wash-1). In addition, the recommended sampling frequency suggests that four sampling points will be placed around MW-2 and MW-3 extending approximately 25 ft in each direction; three sampling points ' will triangulate around the area identified as Wash-1; and one additional sample will be located northwest of UST-1. After the excavation and subsequent soil confirmation samples have been ' collected from the bottom of the excavation, each soil gas sample will be collected at approximately 5 ft bgs from the bottom of the excavation at each proposed location. The proposed soil gas sampling locations are illustrated on Figure 4. 6.3 SAMPLE COLLECTION AND ANALYSIS Miller Brooks proposes to use TEG- Northern California, Inc (TEG) to install the temporary soil gas ' probes and collect the samples. The samples will be subsequently submitted to H&P Mobile Geochemistry's (H&P) off-Site laboratory in Carlsbad, California to analyze the soil gas samples. TEG has developed an SOP for soil gas sampling procedures which includes the probe ' construction and insertion, soil gas sampling, and the appropriate field QA/QC procedures. H&P has also developed an SOP for the TO-15 laboratory analysis. Copies of the SOPS are provided in Appendix A.