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Stantec L & M OPERABLE UNIT- FOURTH QUARTER AND ANNUAL 2012 SITE STATUS, REMEDIAL SUMMARY, AND GROUNDWATER MONITORING REPORT Summary of 2012 Annual Monitoring and Sampling February 1, 2013 historically and during 2012, the TPHg plume was generally delineated to the north, northwest, west, and southwest. 5.8.2 TPHd Concentrations of TPHd are generally detected on the L&M OU property, Delta View apartment property, and on the Water Front Towers' parking lot. Based on data collected historically and during 1Q12 and 4Q12, the TPHd plume was generally delineated, except to the southeast during 4Q12. During 2Q12 and 3Q12, the TPHd plume was delineated to the north and northwest only, respectively. 5.8.3 TPHo Concentrations of TPHo are sporadic and at relatively low concentrations across the C-Zone wells. During the 1Q12, the TPHo plume was delineated to the south and southeast, except for a minor detection in well MW-67. During the 2Q12, TPHo was not reported at concentrations at or above the laboratory MRL, except for two detections south of the Site in wells MW-66 and MW-67. During the 3Q12, the TPHo plume was delineated, except to the south. During the 4Q12, the TPHo plume was delineated to the northeast and east, except for a detection in well MW-64. 5.8.4 Benzene Concentrations of benzene are generally detected on the northern portion of the L&M OU property, and sporadically on the Water Front Towers' parking lot and on the southern section of the Delta View apartment property. Based on data collected during 2012, the benzene plume was generally delineated, except to the east and several detections around well MW-66 to the south of the Delta View Apartments. During the 1Q12, concentrations of benzene were detected in the northern section of the Water Front Towers' parking lot, in well MW-63. 5.8.5 MtBE Concentrations of MtBE are generally detected on the northern portion of the L&M OU property, and seldom on the Water Front Towers' parking lot. Based on data collected historically and during 2012, the MtBE plume is delineated, except to the east. During the 1Q12, concentrations of MtBE were detected in the northern section of the Water Front Towers' parking lot, in well MW-63. 5.8.6 TBA Concentrations of TBA are mainly detected on the northern portion of the L&M OU property. Based on data collected historically and during 2012, the TBA plume is delineated, except to the east. 5.9 D-ZONE ISOCONCENTRATION TRENDS Deep D-Zone isoconcentration trends are discussed below. Figures from the 1Q12, 2Q12, and 3Q12 are provided in Appendix K. I:\Tidewater\TW Stockton(P2A)\QMRs\2012\4Q12-Ann ual\4Q12 and Annual QSSR QRSR QMR Stockton_FINAL.doc 5.6