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Mr.M. Scott Mansholt—CEMC First Quarter 2006 Groundwater Monitoring and Sampling Report April 10,2006 Vernalis Pump Station Page 4 of 5 • BTEX using EPA Method 826013; and • PAHs using EPA Method 8270C SIM. SPO was present in MW-1, and therefore no sample was collected from this well. No TPHg or BTEX were detected in any of the groundwater monitoring wells sampled. No TPHd were detected in MW-5 or the field duplicate sample from MW-6. TPHd were detected in wells MW-2 (120 µg/L; 67 gg/L with silica-gel cleanup),MW-3 (930 gg/L; 950 µg/L with silica-gel cleanup), MW-4 (290 gg/L; 150 gg/L with silica-gel cleanup),MW-6 (95 gg/L; <50 gg/L with silica-gel cleanup), and MW-7 (480 gg/L; 170 gg/L with silica-gel cleanup).3 No PAHs were detected in the groundwater sample collected from MW-2, MW-3,MW-4,MW-5, and MW-6. Low concentrations of some PAHs were detected in the field duplicate sample from MW-6 and the sample from MW-7. All detected PAHs were below their respective Preliminary Remediation Goals (PRGs)for direct exposure to tap water.4 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 PETROLEUM-ABSORBING(OLEOPHILIC) SOCK REPLACEMENT An oleophilic sock has been installed in well MW-1 due to the presence of SPO observed in the well. The sock has been monitored and replaced as necessary on a quarterly basis. During the first quarter of 2006,the sock was weighed but not replaced, and four 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 (QA/QC) All field procedures were conducted in accordance with SAIC's Quality Assurance and Quality Control Sample Collection, Handling, and Analysis 5procedures. No sample was received by the laboratory outside of acceptable temperature or pH limits. In addition to routine laboratory QC sample analysis, four field QC samples were analyzed for this event in accordance with SAIC's standard field procedures: a trip blank(QA-T), a rinsate blank(QA-R), a duplicate(MW-6D), matrix spike (MW-5MS), and matrix spike duplicate(MW-5MSD). No indication of potential cross contamination was identified by the trip blank analyses. A trace concentration of naphthalene(0.011 gg/L)was detected in the rinsate blank. However, naphthalene was detected only at MW-7, and this well has consistently had low detections of naphthalene. The groundwater samples do not appear to have been affected. No THPd,TPHg, BTEX, or PAHs were detected in the laboratory blank sample, and the lab control sample/lab control sample duplicate(LCS/LCSD)recoveries were within the QC limits for the laboratory compliance quality control. The surrogate spike recoveries for the LCS/LCSD associated with the TPHd analysis with silica-gel cleanup were outside the QC limits for the surrogate quality control. However,the surrogate recoveries for the project samples associated with the TPHd analysis with silica-gel cleanup were within the QC limits, and the data was reported. The surrogate recoveries associated with all other analyses were within the QC limits. The MS/MSD results(collected from MW-5 on January 25,2006)were outside the acceptable ranges for several PAHs. Upon further inquiry,the laboratory indicated that the MS/MSD samples were 3. The surrogate spike recoveries for the LCS/LCSD for TPHd with silica gel-cleanup analysis were outside the QC limits. Since the surrogate spike recoveries for the project samples were within the QC limits,the date is reported. 4. The PRGs are risk-based tools for evaluating potential exposure risk to human health at the screening level and for establishing preliminary cleanup goals. 5. SAIC,2006. Quality Assurance and Quality Control Sample Collection,Handling,and Analysis. January (Updated).