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L & M OPERABLE UNIT- FIRST QUARTER 2012 SITE STATUS, REMEDIAL SUMMARY, <br />AND GROUNDWATER MONITORING REPORT <br />April 30, 2012 <br />I:\Tidewater\TW Stockton (P2A)\QMRs\2012\1Q12\1Q12 QSSR QRSR QMR Stockton_FINAL.doc 4.1 <br />4.0 Soil Vapor Sampling <br />4.1 PREVIOUS SOIL VAPOR SAMPLING ACTIVITIES <br />Baseline, startup, and monthly soil vapor sampling results were presented in the report entitled <br />Soil Vapor Well Installation and Soil Vapor Extraction Start-Up Report for events prior to <br />October 2005. Monthly soil vapor sampling results for the October 17 and November 18, 2005 <br />sampling event were presented in the Fourth Quarter and Annual 2005 Site Status, Remedial <br />Summary, and Groundwater Monitoring Report. The DPE system was shut down for retrofit on <br />December 12, 2006, and restarted on May 31, 2007. <br />4.2 SOIL VAPOR SAMPLING FIRST QUARTER 2012 <br />On January 27, 2012, soil vapor samples were collected from 12 of the 15 soil vapor monitoring <br />points located in the adjacent Delta View Apartment complex (APSV locations) and on <br />undeveloped portions of the Site (UPSV locations). Soil vapor points APSV-2, APSV-4, and <br />APSV-5 were not sampled due to water infiltration in the sampling tube during 1Q12 sampling <br />event. Soil vapor point UPSV-4 was destroyed, in concurrence with the CRWQCB-CVR, during <br />fourth quarter 2006 due to its location which interfered with the installation of an additional <br />remediation system on Site. Samples were collected following guidance provided by the <br />California Department of Toxic Substance Control (DTSC) and Los Angeles RWQCB <br />Advisory - Active Soil Gas Investigations, dated January 28, 2003. Soil vapor analytical results <br />from this monitoring event are presented in Table 25 and Figure 35 and are summarized below. <br />Laboratory analytical reports for 1Q12 are provided in Appendix I. <br />4.2.1 Soil Vapor Sampling <br />A Transglobal Environmental Geochemistry-Northern California (TEG) mobile lab and a TEG <br />technician were used to collect and analyze soil gas on Site from 12 of 15 soil vapor points <br />(UPSV-1, UPSV-2, UPSV-3, UPSV-5, UPSV-6, APSV-1, APSV-3, and APSV-6 through <br />APSV-10) on January 27, 2012. In order to sample the soil vapor points, a syringe with a <br />gas-tight fitting was attached to the ¼-inch Teflon® tubing inlet at each soil vapor point. The <br />syringe was used to extract a purge volume of air based on the diameter and depth of inlet <br />tubing. The syringe was then used to collect an air sample and taken to the on Site mobile <br />laboratory for immediate analysis. Samples were analyzed for the following: <br />TPHg using EPA Method 8260B; and <br />BTEX compounds, fuel oxygenates (MtBE, DIPE, EtBE, TBA, TAME), and naphthalene, <br />using EPA Method 8260B. <br />Duplicate samples were collected from UPSV-3 and APSV-10 during 1Q12 event.