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Mr.M. Scott Mansholt—CEMC Third Quarter 2005 Groundwater Monitoring and Sampling Report October 25,2005 US Can-Welty Road,Vernalis,CA Page 5 of 6 detected in wells MW-2 (150,000 gg/L, 170,000 gg/L with silica-gel cleanup),MW-3 (6,700 gg/L, 6,700 gg/L with silica-gel cleanup), and WFSMW-I (170 jig/L). No PAHs were detected in the groundwater samples collected from MW-4,MW-5, and WFSMW-1. Several PAHs were detected in groundwater samples collected from wells MW-2 and MW-3. Groundwater analytical results are presented as Tables 2 and 3. A petroleum hydrocarbon distribution map is presented as Figure 4. A copy of the laboratory analytical report is presented as Attachment B. QUARTERLY ABSORBENT SOCK REPLACEMENT An oleophilic(petroleum-absorbing) sock has been installed in well MW-1 due to the presence of SPO observed in the well. The absorbent sock has been monitored and replaced as necessary on a quarterly basis. Beginning in the fourth quarter 2005, SAIC will weigh the sock to determine the volume of SPO absorbed and whether the sock needs replacing. QUALITY ASSURANCE/QUALITY CONTROL (QA/QC) 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 QC analyses,a trip blank(QA-T)was submitted to the laboratory and analyzed in accordance with SAIC's standard procedures. No potential cross-contamination was indicated by the trip blank. No THPd,TPHg,BTEX, or PAHs were detected in the laboratory blank sample. One PAH was out of specification for the matrix spike sample percent recovered. Some surrogate QC sample analyses were out of specification. The laboratory considers the sample results acceptable and useable. CONCLUSIONS AND RECOMMENDATIONS The third quarter of groundwater monitoring at the site was completed between July 21 and 27, 2005. Groundwater elevations from the on-site wells indicate that groundwater flow has been historically consistent to the northeast at an approximate gradient of 0.03 ft/ft. TPHg was detected in one well,MW-2, at 310 gg/L. No BTEX was detected in any of the groundwater monitoring wells sampled. TPHd was detected in wells MW-2 (15,0000 jig/L, 17,0000 gg/L with silica-gel cleanup),MW-3 (6,700 jig/L, 6,700 gg/L with silica-gel cleanup), and WFSMW-I (170 gg/L). No PAHs were detected in the groundwater sample collected from wells MW-4,MW-5, and WFSMW-1. Several PAHs were detected in groundwater samples collected from wells MW-2 and MW-3. SPO observed in well MW-2 during the second quarter monitoring event accounts for the high concentrations of TPHd this quarter. SPO was observed in well MW-1 during both the second and third quarter monitoring events. The oleophilic sock in MW-I will be monitored quarterly and replaced as necessary. Based on the monitoring and sampling results, it appears that the petroleum hydrocarbons are stable and not migrating laterally. SAIC will continued quarterly monitoring and sampling of wells MW-1 through MW-7 for a minimum of one hydrogeologic cycle(ending first quarter 2006)as recommended in the approved workplan dated March 10,2004.