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Mr.M. Scott Mansholt—CEMC Second Quarter 2007 Groundwater Monitoring and Sampling Report July 26,2007 US Can-Welty Road Page 3 of 6 GROUNDWATER ANALYTICAL RESULTS The groundwater samples from MW-5 and WFSMW-1 were analyzed for the following constituents: • Total petroleum hydrocarbons quantified as diesel(TPHd) (Clo—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 8015B; and • Polynuclear aromatic hydrocarbons(PAHs)using EPA Method 8270C with selective ion monitoring. In Tables 2 and 3,the groundwater analytical results are summarized and compared with the RWQCB Region 2 Environmental Screening Levels (ESLs) and the numerical State Water Quality Objectives (WQOs);1 results exceeding the most conservative ESL or WQO are highlighted in bold-type font in the tables. TPHd were non-detect in MW-5 (<50 µg/L),but were detected in WFSMW-1 at a concentration of 630 gg/L, above the WQO and ESL of 100 micrograms per liter(gg/L). TPHd were non-detect(<50 gg/L) in this sample following silica gel-cleanup preparation. There were no other constituents detected above WQOs or ESLs. A petroleum-hydrocarbon distribution map is presented on Figure 4. The laboratory analytical report and data usability summary,as well as details regarding data qualifiers, are presented as Attachment B. The field sample collected from WFSMW-1 was split for analysis and submitted to both Lancaster and Chevron Energy Technology Company(ETC). ETC conducted a fuel-fingerprint analysis of the sample using gas chromatography with a flame ionization detector to confirm the presence of gasoline-range hydrocarbons and the lack of diesel-range hydrocarbons as observed in the first quarter 2007 fuel fingerprint-analysis results. The results of the ETC analysis show that the sample contained 40 gg/L of "iso-octane,"mono-aromatic (BTEX)compounds, olefins, and other gasoline constituents(Attachment B). No diesel-range hydrocarbons were detected. The approximate percentages of each carbon range detected were C6 at 19.8 percent, C7-C10 at 78.4 percent, C11-C14 at 1.7 percent, and C15+at 0 percent. These carbon-range percentages correspond well to the percentages observed in the first quarter 2007 fuel fingerprint-analysis results. QUARTERLY OLEOPHILIC SOCK REPLACEMENT In 2005, an oleophilic sock was installed in well MW-1 due to the presence of SPO in the well, and an oleophilic sock was placed in MW-2 due to petroleum odor detected from the well. The socks in MW-1 and MW-2 have been monitored and replaced as necessary on a quarterly basis. During the recent monitoring event,the oleophilic socks from MW-1 and MW-2 were replaced because they exhibited SPO staining. However,no measurable amounts of SPO were removed from either of these wells. A total of approximately 0.34 gallon of SPO has been removed since June 1999 from wells MW-2 and MW-2. SPO has not been detected in the other site wells. A summary of SPO thickness measurements is included in Table 1. 1. 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."