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Mr. Jeff Baker - 3 - 17• February 2011 Stockton Terminals Technical 0mittee attributed to mechanical malfunctions. The STTC estimates that historically, about 10,200 pounds of ozone have been injected, and 3,370 pounds of hydrocarbons have been destroyed. The STTC monitors the OS system using an array of six remedial observation (RO) wells, two midpoint wells, and four trigger wells. A contingency plan is triggered if the concentration of BTEX, MTBE or TBA in any of these compliance wells exceeds the termsdescribed in the Revised Contingency Plan (Appendix L of the:Annual Report). During the fourth quarter, benzene concentrations exceeded the default 0.5 Ng/L compliance level in all four trigger wells (OW-2A, OW-2B, OW-4A, OW-413) for the first time. The STTC characterizes the detections as spurious. The Revised Contingency Plan requires the compliance level to be exceeded for three consecutive quarters before remedial actions are required. Therefore, no actions are necessary at this time. STTC member company Tesoro is conducting two pilot studies of remedial technologies. A 1-year, D-zone oxygen injection (01) pilot study proposed in the 27 January 2009 Pilot Study Work Plan and Revised Contingency Plan commenced on 25 January 2011. Instead of injecting oxygen, Tesoro is using a passive source of oxygen, the Waterloo EmitterTM (WE), a down-hole apparatus which is connected to pressurized pure oxygen. Tesoro anticipates that oxygen will be delivered via the WE at a rate of about 3.64 liters per day. Baseline groundwater monitoring was conducted for dissolved oxygen/ oxidation reduction potential(DO/ORP) and biodegradation parameters during November and December 2010 in TS/MW-3DR and TS/MW-4D. Quarterly groundwater monitoring data from TS/MW-2D, TS/MW-3D, TS/MW-3DR and TS/MW-4D represented baseline contaminant data. Bio Traps®deployed in TS/MW-2D, TS/MW-3DR, and TS/MW-4D in November 2010 were retrieved and analyzed. The results of the baseline monitoring are summarized in the 27 January 2011 Oxygen Injection Pilot Study Status and Implementation Report (Report). The results of baseline monitoring show that benzene, TPHg, and TPHd are the principal contaminants of concern in TS/MW-2D, TS/MW-3D, TS/MW-3DR and TS/MW-4D. There are minor concentrations of toluene, ethylbenzene, and xylene. Maximum concentrations of benzene, TPHg, and TPHd in baseline monitoring are 5,300 pg/L, 9,800 pg/L, and 2,800 pg/L, respectively, in TS/MW-3DR. These concentrations are consistent with historical results. Table 3 of the Report compares redox parameters observed in the center (TS/MW-3DR) with the fringe (TS/MW-4D) of the OI pilot study plume. The concentration ratios of electron acceptors to reduction products of nitrate/nitrite and sulfate/sulfide were low to non-detect in both wells. The respiration byproduct and ferrous iron (Fe ll) and the macronutrient orthophosphate were non-detect. Carbon dioxide (CO2), alkalinity and methane concentrations were higher in TS/MW-3DR than TS/MW-4D, providing evidence of higher microbial respiration in the center of the plume. The high concentrations of the waste product methane in both TS/MW-3DR and TS/MW-4D correlate with the absence of more thermodynamically efficient electron acceptors and suggest that biodegradation may be occurring via methanogenisis using CO2 as the electron acceptor. The BioTrap data indicate that the highest biomass and