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Mr.M. Scott Mansholt—CEMC Second Quarter 2006 Groundwater Monitoring and Sampling Report July 11,2006 Vernalis Pump Station Page 4 of 5 Laboratories, Inc. (Lancaster),under SAIC chain-of-custody protocol. Lancaster is a California State-certified laboratory(ELAP#2116). No sample was collected from MW-1 due to the presence of SPO in this well. Field data sheets are included as Attachment A. GROUNDWATER ANALYTICAL RESULTS The groundwater samples from MW-5,MW-6, and MW-7 were analyzed for the following: • TPHd: Clo—C25,using U.S. 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 826013; and • PAHs using EPA Method 8270C SIM. No TPHg or BTEX were detected in any of the groundwater monitoring wells sampled. No TPHd were detected in the groundwater sample collected from MW-6. TPHd were detected in wells MW-5 (72 J gg/L;<50 µg/L with silica-gel cleanup),MW-7 (7 10 J µg/L; 52 J µg/L with silica-gel cleanup),and MW-7 field duplicate sample(550 J gg/L; <50 with silica-gel cleanupf Low concentrations of some PAHs were detected in the samples from MW-5,MW-6,MW-7, and the field duplicate sample from MW-7. All detected PAHs were below their respective Preliminary Remediation Goals(PRGs) for direct exposure to tap water.5 Groundwater analytical results are presented in Tables 2 and 3. A petroleum-hydrocarbon distribution map is presented on Figure 4. A copy of the laboratory analytical report is presented as Attachment B. Starting the second quarter 2006, laboratory analytical data are being qualified. Please see Attachment B for details regarding data qualifiers. QUARTERLY OLEOPHILIC SOCK REPLACEMENT An oleophilic sock has been installed in well MW-1 due to SPO observed in the well. The sock has been monitored and replaced as necessary on a quarterly basis. During the second quarter of 2006,the sock was weighed but not replaced, and 3 ounces(approximately 0.03 gallon)of SPO had been absorbed. A summary of SPO thickness measurements is included in Table 1. QUALITY ASSURANCE/QUALITY CONTROL All field procedures were conducted in accordance with SAIC's Quality Assurance and Quality Control Sample Collection, Handling, and Analysis. 6 Based on SAIC's evaluation, all analytical data are usable as qualified for the purpose of determining chemical concentrations in groundwater at the site. Data in this sample delivery group were qualified for low surrogate percent recoveries, field duplicate relative percent differences, and estimated concentrations reported between the 4. J=The analyte was positively identified;the associated numerical value is the approximate concentration of the analyte in the sample. 5. The PRGs are risk-based tools for evaluating potential exposure risk to human health at the screening level and for establishing preliminary cleanup goals. 6. SAIC,2006. Quality Assurance and Quality Control Sample Collection,Handling,and Analysis. January (Updated).