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and TPH-g,TPH-MO and TPH-D discreet surface samples will be collected at two randomly selected locations. 6.2.2 Background Subsurface Soil Sampling Four(4) CAM 17 metals background soil samples will be collected on Site at five feet bgs. These samples will be collected from the sidewalls of an excavation made by a backhoe or other similar excavation equipment. These samples will be collected and transported in the same manner as other soil samples collected at the Site as described in Section 6.3.1. 6.2.3 QA/QC Samples As per the PEA Manual, QA/QC samples will be collected according to Table 3 below. Table 3:QA/QC Sampling Constituent Number of Number of QA/QC Location Samples Collected Proposed Samples Lead 42 2 Random OCP's 34 2 Random Arsenic 24 1 Random *Other proposed samples in this workplan(i.e. PCB's,TPH's)do not have a large enough sample group(n)to create a statistically significant data set. These QA/QC samples will be unrecognizable to the lab and will be collected, stored, transported and analyzed in a manner consistent with the collection of Site samples as described in Section 6.3.1. 6.2.4 Site Soil Gas Samples Due to the nature of the Site being above the Harte Gas Field as described in Section 3.2.1, three on Site soil vapor samples (SVS's) borings will be made. Two borings will be made on-Site nearest the former off-Site gas wells, one in the northeast corner and one in he southeast corner of the Site. The other boring will be made near the on-Site domestic water well. All of these locations have been discussed previously with DTSC project managers. Soil vapor samples will be collected at five and 15 feet bgs and analyzed for methane and hydrogen sulfide. All sample collection and analysis will be completed with guidance from the DTSC's Advisory on Active Soil Gas Investigations (DTSC, January 28, 2003). The borings will be advanced using a Strataprobe®percussion hammer (direct push method) with a sample barrel fitted with a 3 inch long screened expendable air sampling tip. (See Appendix A, Figure 29). The soil gas sampling tip will be advanced to the target depth, opened, and the sample tubing purged of ambient air with a vacuum pump. Before collection of samples, the sampling apparatus will equilibrate for 30 minutes. Methane samples will be collected in 6-liter Summa Canisters with gauges and will be checked for vacuum seal integrity before sample is collected. After the samples are collected, the Summa canisters Preliminary Environmental Assessment Workplan Proposed Podesta Ranch Elementary School December 4,2006 Page 11 of 27