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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 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-I 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. 7 GROUNDWATER MONITORING AND SAMPLING 7 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 '1 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-l. All samples were collected using a bailer, and laboratory-provided bottles were filled directly from the bailer. The bottles were labeled, r, sealed, and placed immediately into an ice-cooled chest for delivery to Lancaster Laboratories, 7 Inc. (Lancaster), under SAIC chain-of-custody protocol. Lancaster is a California State-certified laboratory(FLAP#2116). The samples were analyzed for the following: • TPHd: Cip-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; 7 • TPHg: C6-C10, 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 pg/L. No BTEX was detected in the groundwater samples. TPHd was