SITE INFORMATION AND CORRESPONDENCE

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Mr.M. Scott Mansholt—CEMC Third Quarter 2006 Groundwater Monitoring and Sampling Report October 25,2006 Vernalis Pump Station Page 4 of 5 criteria is presented on field data sheets), groundwater samples were collected. The groundwater samples were decanted into laboratory provided bottles. The samples were placed into laboratory-provided bottles that were labeled, sealed, and placed immediately into an ice-cooled container for delivery to Lancaster 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. GROUNDWATER ANALYTICAL RESULTS The groundwater samples from MW-6,MW-7, and MW-7 field duplicate were analyzed for the following constituents: • TPHd(C107-C25),using U.S. Environmental Protection Agency(EPA)Method 8015B and TPHd with silica-gel preparation for samples with detectable concentrations of TPHd using EPA Method 801513; • TPHg(C6—C12),using EPA Method 801513; • BTEX using EPA Method 826013; and • PAHs using EPA Method 8270C Selected Ion Monitoring(SIM). The groundwater analytical results are summarized and compared with the RWQCB Region 2 Environmental Screening Levels(ESLs)and the numerical State WQOs in Tables 2 and 34. Analytical results exceeding the most conservative ESL and/or WQO are highlighted in Tables 2 and 3 in bold-type font. No TPHg,BTEX, or PAHs 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 at low concentrations in the samples from MW-7 (62 gg/L; <50 gg/L with silica-gel cleanup) and MW-7 field duplicate sample(52 gg/L; <50 gg/L with silica-gel cleanup). It should be noted that TPHd were detected at a concentration of 36µg/L in the method blank(laboratory quality assurance/quality control [QA/QC] sample); therefore,the TPHd detection at MW-7 may be attributed to cross-contamination from the laboratory. A petroleum-hydrocarbon distribution map is presented on Figure 4. A copy of the laboratory analytical report and the data usability summary are presented as Attachment B. 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 third quarter of 2006,the sock was weighed but not replaced, and 5 ounces(approximately 0.05 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. 5 Based on SAIC's evaluation, all analytical 4. The ESLs(provided as a reference)are a tool based on conservative standard exposure factors for initial human health and the environment screening-level evaluations of analytical results. The WQOs are defined by the Porter- Cologne Act as"the levels or limits of water quality constituents or characteristics which are established for the reasonable protection of beneficial uses of water or the prevention of nuisance within a specific area." 5. SAIC,2006. Quality Assurance and Quality Control Sample Collection,Handling,and Analysis. January (Updated).