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Soil and Groundwater Investigation Report and Second Quarter 2005 Monitoring and Sampling,US Can-Welty Road October 2005 10.4 QUALITY ASSURANCE/QUALITY CONTROL All field procedures were conducted in accordance with SAIC's Quality Assurance and Quality Control Sample Collection, Handling, and Analysis procedures. No sample was received by the laboratory outside of acceptable temperature or pH limits. In addition to routine laboratory quality control(QC) analyses, a trip blank(QA-T)and equipment rinsate(QA-RB)were submitted to the laboratory with samples WFSMW-1 and MW-5. In accordance with SAIC's standard procedures,the trip blank was analyzed. No BTEX were detected in the trip blank. The laboratory control sample(LCS) and laboratory control sample duplicate(LCSD) appear to be within the LCS/LCSD limits. The matrix spike(MS) and matrix spike duplicate(MSD) also are within the MS/MSD limits and the relative percent difference criteria was within the acceptable range for either the LCS/LCSD or MS/MSD samples except for PAH compound(benzo[a]pyrene). The laboratory analytical report noted this PAH compound as "outside of specification." While not all of the laboratory QC parameters were within specification range,the information provided by these analytical results is considered useable. Laboratory QA/QC data from this sampling event are considered acceptable and the sample analytical data are considered valid. 11. DISCUSSION Based on the analytical results,the lateral extent of petroleum-affected soil at US Can—Welty Road appears to be delineated northwest to northeast of borings GMX-10 through GMX 12 by soil borings SB-13, SB-14, SB-15 and former borings GMX-6 and GMX-7. However,petroleum-affected soil does not appear to be delineated southeast of GMX-11, adjacent to the former OVP pipeline ROW. Affected soil in this area was encountered in boring SB-17,but not unexpected since it is adjacent to the former pipeline ROW and borders the former Vernalis Pump Station. Affected groundwater has been delineated by groundwater samples collected from wells WFSMW-1 and MW-5. Well MW-5 did not contain detectable concentrations of petroleum hydrocarbons and the groundwater sample from well WFSMW-1 did not contain detectable TPHg,BTEX, or MTBE. However,the groundwater sample collected from well WFSMW-1 contained TPHd at a concentration of 71 µg/L,below the water quality objective(WQO) of 100 gg/L. Although grab groundwater samples collected from soil borings SB-13 and SB-14 contained detectable TPHd at concentrations of 450 and 200 gg/L,respectively,these samples should be considered lesser quality and expected to be an order of magnitude higher in concentration than detected in the groundwater monitoring wells. Detectable concentrations of TPHg,BTEX, or MTBE were not detected in these grab groundwater samples. The grab groundwater sample collected from SB-17 contained 480 pg/L of TPHg, 150,000 gg/L of TPHd and 0.6 gg/L of benzene. The detection of dissolved-phase TPHg is likely an overlap of the diesel range organics based on the elevated concentration of dissolved TPHd detected. However,the presence of benzene in the grab groundwater sample from SB-17 could indicate a refined fuel plume is emanating from the former Union Oil Service Station, located north(cross gradient)of boring location SB-17. 12. SUMMARY/CONCLUSIONS The data collected during this and former subsurface investigations indicate that residual petroleum has mainly affected soil between 5 and 42 feet bgs in the vicinity of SB-17,MW-1, SB-1, SB-2, SB-3,B-1, B-4 through B-7(MW-2), GMX-3, GMX-8, GMX-1B,and GMX-12. In SB-17 lean clay and sandy layers below 37 feet bgs appear to be the most affected soil areas. In general,the depth of affected areas varies through the site. The lateral extent of petroleum-affected soil appears to be delineated towards the south,west,north,northeast, and east. However,the lateral extent of petroleum-affected soil southeast of the subject site has not been fully characterized adjacent to the former OVP ROW,which borders the 9 From Science to Solutions-