ARCHIVED REPORTS_FIRST QUARTER 2007 GROUNDWATER MONITORING AND SAMPLING REPORT

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' Mr. M. Scott Mansholt—CEMC First Quarter 2007 Groundwater Monitoring and Sampling Report April 24,2007 ' Vernalis Pump Station Page 4 of 5 • TPHd(C,o—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; and • PAHs using EPA Method 8270C selective 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 3;5 results exceeding the most conservative ESL or WQO are highlighted in bold-type font. No TPHd or PAHs ' were detected at concentrations exceeding the most conservative WQO or ESL, except possibly 150 pg/L TPHd in MW-5 and MW-7,and several PAHs detected in MW-6. No PAHs were detected in the duplicate sample for MW-6 collected at the same time. It should be noted that TPHd were detected at a ' concentration of 110 µg/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. The groundwater sample from MW-5 was analyzed for General Minerals as suggested by the RWQCB during a semi-annual project meeting in August,2006. The results of the analyses are presented in ' Attachment C. Analyses of major dissolved-ion species (Na+, Ca 2+,K+,Mg2+, Cl-, S042-,HCO3-)were expressed by plotting relative concentrations on a trilinear diagram(Piper Diagram), and displaying the percentage composition of the cation/anion groups (Attachment C). As shown in Attachment C, the groundwater sample indicates that the water-bearing zone is not controlled by a specific ionic type.5 A cation-anion balance was conducted to validate the laboratory analysis. The percent error calculated from the charge balance for MW-5 is 2.7 percent. Less than 5 percent is considered an acceptable error ' for analysis.' QUARTERLY OIL-ABSORBENT(OLEOPHILIC) SOCK REPLACEMENT An oleophilic sock was installed in well MW-1 due to SPO observed in the well. The sock has been ' monitored and replaced as necessary on a quarterly basis. During the first quarter of 2007,the sock was weighed but not replaced. A summary of SPO thickness measurements is included in Table 1. ' QUALITY ASSURANCE/QUALITY CONTROL All field procedures were conducted in accordance with SAIC's Quality Assurance and Quality Control Sample Collection, Handling, and Analysis.8 Based on SAIC's evaluation,all analytical data are usable ' as qualified for the purpose of determining chemical concentrations in groundwater at the site. Qualified data with applicable reason codes are shown in Table B-1 of Attachment B. Unless noted otherwise,analytical data collected in support of this investigation are considered precise, ' accurate, representative, complete,and comparable, and they may be used for their intended purposes. CONCLUSIONS AND RECOMMENDATIONS The groundwater elevation ranged between 68.09 and 71.24 feet above MSL with a gradient predominantly towards the east at 0.001 ft/ft. Dissolved-phase TPHd concentrations have historically ' 5. 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." 6. C.W.Fetter, 1994. Applied Hydrogeology,Third Edition,Prentice Hall Inc.,p.421-3. 7. R.Freeze,J.Cherry, 1979. Groundwater,Prentice Hall Inc.,p.97. 8. SAIC,2007. Quality Assurance and Quality Control Sample Collection,Handling,and Analysis. April(Updated).