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Mr.M. Scott Mansholt—CEMC Third Quarter 2006 Groundwater Monitoring and Sampling Report October 25,2006 US Can-Welty Road Page 3 of 5 Since 2005, a sheen has been observed in well MWA, and a petroleum odor or sheen has been observed in MW-2. TPH as diesel-range organics(TPHd)have been detected in wells MW-3 and WFSMW-1 at concentrations of up to 6,700 and 240 micrograms per liter(gg/L),respectively. No dissolved-phase TPH as gasoline-range organics(TPHg) or benzene,toluene, ethylbenzene, and total xylenes(BTEX)have been detected in the groundwater from the site wells. TPHg and TPHd were detected in the separate-phase oil(SPO) from well MW-2 in 2005. Low levels of polynuclear aromatic hydrocarbons(PAHs)have occasionally been detected in groundwater from MW-2,MW-3,MW-5, and WFSMW-l. GROUNDWATER MONITORING AND SAMPLING MONITORING On August 16, 2006 depth to groundwater was measured in wells MW-1 through MW-5 and WFSMW-1 using a hydrocarbon/water interface probe. Depth to groundwater in these wells ranged from 31.59 feet below top of casing(btoc)in MW-5 to 35.82 feet btoc in MW-4. The approximate groundwater flow direction beneath the site is to the east at a calculated gradient of approximately 0.001 ft/ft. Cumulative depth-to-groundwater 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 depth-to-groundwater measurements,wells MW-5 and WFSMW-1 (duplicate sample also collected)were purged on August 16,2006,using the regulatory approved low-flow minimal drawdown method. A low-flow submersible pump with dedicated polyethylene tubing was used. During the purge process,pH, specific conductance,temperature, oxygen-reduction potential, turbidity, and dissolved oxygen water-quality parameters were recorded. After water-quality parameters stabilized(stabilization criteria is presented on field data sheets), groundwater samples were collected. Wells MW-3 and MW-4 were not sampled due to insufficient groundwater recovery for sample collection in the wells. Laboratory-provided bottles were used to preserve the samples. 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). No samples were collected from wells MW-1 and MW-2 due to the presence of SPO in these wells and the presence of petroleum-absorbing(oleophilic) socks. Field data sheets are included as Attachment A. GROUNDWATER ANALYTICAL RESULTS The groundwater samples from WFSMW-1 and MW-5 were analyzed for the following constituents: • TPHd(CIO--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 802113; and • PAHs using EPA Method 8270C selected ion monitoring(SIM).