SITE INFORMATION AND CORRESPONDENCE

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Mr.M. Scott Mansholt—CEMC First Quarter 2006 Groundwater Monitoring and Sampling Report April 10,2006 Vernalis Pump Station Page 3 of 5 A sheen of SPO was observed in well MW-1. Dissolved-phase crude oil is indicated by total petroleum hydrocarbons quantified as diesel(TPHd) analyses. TPHd have been consistently detected in one well,MW-7, at concentrations ranging from 240 to 620 micrograms per liter (µg/L). No total petroleum hydrocarbons quantified as gasoline(TPHg) or benzene,toluene, ethylbenzene, and total xylenes (BTEX)have been detected in the groundwater from the site wells. Low levels of polynuclear aromatic hydrocarbons(PAHs)have been detected in groundwater from MW-2,MW-3,MW-6, and MW-7. GROUNDWATER MONITORING AND SAMPLING MONITORING On January 20,2006, depth to water(DTW)was measured in wells MW-2,MW-3, MW-4, MW-5,MW-6, and MW-7 using a hydrocarbon/water interface probe. DTW was not measured in MW-I because of the presence of an absorbent sock. DTW in these wells ranged from 34.3 feet below top of casing(btoc)in MW-7 to 38.39 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 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 Groundwater samples were collected from wells MW-2 through MW-7 on January 25,2006. Wells MW-2,MW-3,MW-4, and MW-5 were purged of approximately four casing volume of groundwater using a 2-inch disposable polyethylene bailer due to the low volume of water in the well casing. Wells MW-6 and MW-7 were purged of approximately three casing volumes using a low-flow submersible pump. During sampling of the 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. The matrix spike(MS)/matrix spike duplicate (MSD) samples collected from MW-5 were not adequately spiked by the laboratory and fell outside of the quality control(QC) limits. Therefore, along with the additional MS/MSD samples another groundwater sample was collected from MW-5 on March 16, 2006. No sample was collected from MW-I 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 January 25, 2006 from wells MW-2,MW-3,MW-4, MW-5,MW-6, and MW-7. MW-5 was re-sampled on March 16,2006 because the MS/MSD samples failed to meet QC requirements. Groundwater samples were collected using either a 2-inch disposable polyethylene bailer or a low-flow submersible pump using new polyethylene tubing through which groundwater was extracted. 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). The samples were analyzed for the following: • TPHd: C,o—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—Clo,using EPA Method 8015M;