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Mr.M. Scott Mansholt—CEMC Third Quarter 2005 Groundwater Monitoring and Sampling Report October 25,2005 US Can-Welty Road,Vernalis,CA Page 4 of 6 event, site wells MW-1 through MW-4 and off-site wells WFSMW-1 and MW-5 were monitored for depth to water(DTW). SPO or hydrocarbon sheen was observed in MW-1 and MW-2. Wells MW-3 and MW-4 contained only limited quantities of water and were not sampled. Wells WFSMW-1 and MW-5 were the only wells sampled following DTW measurements. GROUNDWATER MONITORING AND SAMPLING MONITORING On July 21, 2005,DTW was measured in wells MW-2,MW-3,MW-4, and off-site well MW-5. DTW was measured in off-site well WFSMW-1 on July 27,2005. Using a hydrocarbon/water interface probe,DTW in these wells ranged from 31.98 feet below top of casing(btoc)in MW-5 to 35.65 feet btoc in MW-4. The approximate groundwater flow direction beneath the site is to the southeast at a calculated gradient of approximately 0.001 feet/foot(ft/ft). A DTW measurement was not collected from well MW-1 due to the presence of SPO. Cumulative DTW measurements, groundwater elevations, and product thickness 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,wells MW-2 through MW-5 were purged dry with a vacuum truck on July 18, 2005. The purpose of purging was removal of sediment in order to create a deeper water column from which to sample. On July 21, 2005, an additional four casing volumes of groundwater were purged from well MW-5 using a disposable polyethylene bailer. Four casing volumes were also purged from well WFSMW-1 on July 27, 2005 using a disposable polyethylene bailer. For wells MW-5 and WFSMW-1,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. Due to the low water levels, no water-quality parameters were recorded for wells MW-3 and MW-4. Field data sheets are included as Attachment A. GROUNDWATER ANALYTICAL RESULTS Groundwater samples were collected on July 21,2005 from wells MW-2,MW-3,MW-4, and MW-5, and on July 27,2005 from well WFSMW-1. 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—C,0,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. TPHg was detected in MW-2 at 310 gg/L. No BTEX was detected in the groundwater samples. TPHd was