ARCHIVED REPORTS_THIRD QUARTER 2011 SITE STATUS, REMEDIAL SUMMARY, AND GROUNDWATER MONITORING REPORT

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Stantec L & M OPERABLE UNIT- THIRD QUARTER 2011 SITE STATUS, REMEDIAL SUMMARY, AND GROUNDWATER MONITORING REPORT Groundwater Monitoring and Sampling October 28, 2011 2.6.2.1 Quality Assurance/Quality Control Samples Duplicate sample QCDUP-6 was collected from L&M OU D-Zone well MW-69 during 3Q11 sampling event. A comparison of the samples is shown below. Analyte Sample # Sample # % Difference MW-69 QCDUP-6 TPHg (mg/L) <0.05 <0.05 0% TPHd (mg/L) 0.38 0.22 +/- 53.3% TPHo (mg/L) 0.092 <0.05 NA Benzene (mg/L) <0.0005 <0.0005 0% MtBE (mg/L) <0.0005 <0.0005 0% TBA (mg/L) <0.005 <0.005 0% 2.6.2.2 General Laboratory Notes The laboratory validation issues are consistent with the D-Zone quality assurance and quality control. Each set of issues corresponds directly with the denoted report. All laboratory reports are included in Appendix D. Validation issues with report number 78189: The MRL for chloromethane in well MW-70 was raised due to the presence of an interfering compound. Validation issues with report number 78203: The MRL for 1,1,2-trichloroethane was raised in samples collected from well MW-55 due to the presence of an interfering compound. Groundwater samples collected from well MW-55 were analyzed by EPA Method 8260B using bottles that contained headspace bubbles greater than 1/4 inch in diameter. 2.7 THIRD QUARTER 2011 SEPARATE PHASE HYDROCARBONS AND HYDROCARBON CONCENTRATION TRENDS 2.7.1 Shallow Zone The following sections summarize trends for detected petroleum hydrocarbons, fuel oxygenates, and observed SPH for shallow (A-Zone) groundwater beneath the Site. 2.7.1.1 Separate Phase Hydrocarbons Measurable SPH or SPH-sheen has historically been observed in shallow A-Zone wells MW-10, 2AMW-13, 2AMW-14, MW-19, and DPE-1 through DPE-13. Due to the quantity and viscous Iffidewater7W Stockton(P2A)\QMRs\2011\3Q11\3011 QSSR QRSR QMR Stockton_FINAL.doc 2.18