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Mr.M. Scott Mansholt—CEMC Third Quarter 2005 Groundwater Monitoring and Sampling Report October 25,2005 Vernalis Pump Station,Vernalis,CA Page 5 of 6 GROUNDWATER ANALYTICAL RESULTS Groundwater samples were collected on July 19, 2005 from wells MW-2,MW-3,MW-4,MW-5, MW-6, and MW-7. All samples were collected using a bailer, and laboratory-provided bottles were filled directly from the bailer. The bottles were labeled, sealed, and placed immediately into an ice-cooled chest for delivery to Lancaster Laboratories, Inc. (Lancaster),under SAIC chain-of- custody protocol. Lancaster is a California State-certified laboratory(ELAP#2116). The samples were analyzed for the following: • TPHd: C10—C25 using Environmental Protection Agency(EPA) Method 8015M and TPHd with silica-gel preparation for samples with detectable concentrations of TPHd using EPA Method 8015M; • TPHg: C6—Clo,using EPA Method 8015M; • BTEX using EPA Method 8260B; • PAHs using EPA Method 8270C SIM. No TPHg or BTEX were detected in any of the groundwater monitoring wells sampled. TPHd was only detected in well MW-7 (240 gg/L, 64 gg/L with silica-gel cleanup). No PAHs were detected in the groundwater sample collected from MW-2,MW-3,MW-4, and MW-5. Low concentrations of some PAHs were detected in samples from MW-6 and MW-7. 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 sample analysis, one field QC sample was analyzed for this event in accordance with SAIC's standard field procedures. The field QC sample collected was a trip blank(QA-T). No indication of potential cross contamination was identified in the sample analyses. No indication of potential cross-contamination was indicated by the trip blanks. No THPd, TPHg,BTEX, or PAHs were detected in the laboratory blank sample. The surrogate quality control samples fall within acceptable range. The laboratory considers the sample results acceptable and useable. CONCLUSIONS AND RECOMMENDATIONS The third quarter of groundwater monitoring at the site was completed on July 19, 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. SPO was observed in well MW-1 during the third quarter monitoring event. No TPHg or BTEX were detected in the groundwater. TPHd was only detected in well MW-7 (240 µg/L, 64 gg/L with silica-gel cleanup). No PAHs were detected in the groundwater sample collected from MW-2,MW-3,