SITE INFORMATION AND CORRESPONDENCE (2)

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Mr.M. Scott Mansholt—CEMC Fourth Quarter 2006 Groundwater Monitoring and Sampling Report and Annual Summary Report January 12,2007 Vernalis Pump Station Page 5 of 7 elevations ranged from 68.83 feet(MW-1)to 72.04 feet(MW-3)above mean sea level(MSL). 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 SPO thickness measurements are presented in Table 1. A map showing the potentiometric surface is presented on Figure 3. Field data sheets are included as Attachment A. SAMPLING Following depth-to-groundwater measurements,wells MW-3, MW-6, and MW-7 were purged using the regulatory-accepted, low-flow minimal drawdown method. Wells MW-2 and MW-4 were not sampled because the water volume in the wells was insufficient for sample collection. MW-5 was not accessible during sample collection and was not sampled. No sample was collected from MW-1 due to the presence of SPO in this well. 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. The groundwater samples were decanted 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-certified laboratory(ELAP#2116). GROUNDWATER ANALYTICAL RESULTS The groundwater samples from MW-3, MW-6,MW-7, and MW-6 field duplicate 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 8015B; • BTEX using EPA Method 8021B; and • PAHs using EPA Method 8270C Selected Ion Monitoring(SIM). The groundwater analytical results are summarized and compared with the RWQCB Region 2 Environmental Screening Levels(ESLs) and the numerical State WQOs in Tables 2 and 39;results exceeding the most conservative ESL or WQO are highlighted in bold-type font. No TPHg or BTEX were detected in any of the groundwater monitoring wells sampled. No TPHd or PAHs were detected in the groundwater samples collected from MW-3 and MW-6. TPHd were detected at a concentration of 130 gg/L in the sample from MW-7. Low PAH concentrations were detected in well MW-7 (fluorene at 0.010 gg/L and naphthalene at 0.027 gg/L,respectively). It should be noted that TPHd were detected at a concentration of 110 gg/L in the equipment blank sample; therefore,the TPHd detection at MW-7 may be attributed to cross contamination. A petroleum hydrocarbon-distribution map is presented on Figure 4. The data usability summary and a copy of the laboratory analytical report are presented as Attachment B. Please see Attachment B for details regarding data qualifiers. 9. The ESLs(provided as a reference)are a tool based on conservative standard exposure factors for initial human health and the environment screening-level evaluations of analytical results. The WQOs are defined by the Porter-Cologne Act as"the levels or limits of water quality constituents or characteristics which are established for the reasonable protection of beneficial uses of water or the prevention of nuisance within a specific area."