SITE INFORMATION AND CORRESPONDENCE

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I I Mr. M. ScottMansholt—CEMC Fourth Quarter Groundwater Monitoring and Sampling Report and 2005 Annual Summary December 22,2005 Vernalis Pump Station, Vernalis,California Page 5 of GROUNDWATER MONITORING AND SAMPLING MONITORING On October 18,2005, depth to water(DTW) was measured in wells MW-1, MW-2, MW-3, MW-4, MW-5, MW-6, and MW-7 using a hydrocarbon/water interface probe. DTW in these wells ranged from 33.71 feet below top of casing (bloc) in MW-6 to 37.42 feet btoc in MW-5. The approximate groundwater flow direction beneath the site is to the east-southeast at a calculated gradient of approximately 0.001 feet/foot (ft/ft). Cumulative DTW measurements, groundwater elevations, and SPO thickness measurements are presented in Table 1. A map showing the potentiometric surface is presented on Figure 3. Field data sheets are included in Attachment A. SAMPLING Following DTW measurements, groundwater samples were collected from wells MW-2 through MW-7 on October 18, 2005. Wells MW-2, MW-3, and MW-4 were not purged due to the low volume of water in the well casing. Wells MW-5, MW-6, and MW-7 were purged of approximately four casing volumes using a 2-inch disposable polyethylene bailer or a low-flow submersible pump. In these wells, pH, specific conductance, dissolved oxygen, turbidity, and temperature water-quality parameters were recorded. After water-quality parameters stabilized (i.e., a minimum of three consecutive readings with values within 10 percent for each parameter), groundwater samples were collected. 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 Groundwater samples were collected on October 18, 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 or by a low-flow submersible pump using new polyethylene tubing through which groundwater was extracted. 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: CIO—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—Ci0, using EPA Method 8015M; • 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. TPHd was only detected in well MW-7 (620 pg/L; 270 pg/L with silica-gel cleanup). No PAHs were detected in the groundwater sample collected from MW-4 and MW-5. Low concentrations of some PAHs were detected in samples from MW-2, MW-3, 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.