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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 5.9.1 TPHg Concentrations of TPHg are generally detected on the L&M OU property and on the Water Front Towers' parking lot. Based on data collected historically and during 1Q12, 2Q12, and 3Q12, the TPHg plume was delineated to the south, southwest, west, and northwest. During 4Q12, the TPHg plume was delineated to the south only. 5.9.2 TPHd Concentrations of TPHd are sporadic across the D-Zone wells. During the 1Q12, 2Q12, and 3Q12, the TPHd plume was delineated, except to the east. During the 4Q12, the TPHd plume was delineated. 5.9.3 TPHo Concentrations of TPHo are sporadic and at relatively low concentrations across the D-Zone wells. During the 1Q12, 2Q12, and 4Q12, concentrations of TPHo are detected in two distinct areas of the Site, on the Water Front Towers' parking lot including MW-55, and south of the Delta View Apartments. On the Water Front Towers' parking lot and MW-55, the TPHo plume was generally delineated to the south, during 1Q12 and 2Q12. During 4Q12, the TPHo plume was delineated, except to the north. To the south of the Site, the TPHo plume was delineated to the north only. During the 3Q12, the TPHo plume was not delineated. 5.9.4 Benzene Concentrations of benzene are detected on the eastern section of the Water Front Towers' parking lot and sporadically in well MW-71. Based on data collected historically and during 2Q12 and 3Q12, the benzene plume was delineated, except to the north and east. During the 1 Q12 and 4Q12, the benzene plume was delineated to the south, southwest, and west. 5.9.5 MtBE Concentrations of MtBE are detected on the northern portion of the L&M OU property, mainly in well MW-55. Based on data collected historically and during 2012, the MtBE plume is delineated. 5.9.6 TBA Concentrations of TBA are detected in the northern portion of the L&M OU property and on the eastern section of the Water Front Towers' parking lot including well MW-71. Based on data collected historically and during 2012, the TBA plume is delineated, except to the north and east. 5.10 2012 ARSENIC TRENDS In accordance with the MRP for the Site, groundwater sampling for the presence of arsenic was only required during the 3Q12. Arsenic concentrations in selected A-Zone wells within the hydrocarbon plume and within perimeter wells were evaluated for historical trends on an annual basis during the 3Q12. During 3Q12, A-Zone arsenic detectable concentrations ranged from I:\Tidewater\TW Stockton(P2A)\QMRs\2012\4Q12-Ann ual\4Q12 and Annual QSSR QRSR QMR Stockton_FINAL.doc 5.7