SITE INFORMATION AND CORRESPONDENCE

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Mr. Jeff Baker Stockton Terminals Technical Committee 3 31 August 2010 The Revised Contingency Plan also sets compliance limits consisting of the WQOs for BTEX and MTBE in four trigger wells located downgradient of the RO wells. Three consecutive exceedences of the WQO would trigger installation of another ozone sparge array east of the trigger wells that include OW-2A, OW-4A, OW-26, and OW-413. During the second quarter, BTEX and MTBE concentrations were not detected above their WQOs. Based on the groundwater monitoring data in the Second QMR, STTC concludes that (1) the overall hydrocarbon concentration trends in groundwater beneath and downgradient of the Site appear relatively stable to decreasing, (2) results from the ozone injection monitoring program indicate the East and West remedial systems are effectively mitigating off-site migration of petroleum hydrocarbons and (3) sampling in TS/MW-3D should be discontinued. STTC member company Tesoro is presently conducting two pilot studies of remedial technologies. A 1-year, D-zone oxygen injection pilot study proposed in the 27 January 2009 Pilot Study Work Plan and Revised Contingency Plan is being conducted at TS/MW-1 D. Instead of injecting oxygen, Tesoro will be using a passive source of oxygen, such as the Waterloo EmitterT^^ (WE), a down-hole apparatus which is connected to pressurized Pure oxygen. Tesoro commenced the study by conducting the TS/MW-2D helium-tracer study between June and October 2009. Based on these observations, injection wells TS/MW-3DR and TS/MW-4D were installed and developed during March 2010. TS/MW-3D was redeveloped on 3 June to remove sediment from the casing. The helium tracer test to confirm hydraulic communication between TS/MW-3DR and TS/MW-2D was conducted on 30 June 2010. Documentation of the tracer test and the well installations will be presented under separate cover. Based on the work plan, baseline groundwater monitoring was conducted for dissolved oxygen/oxidation reduction potential (DO/ORP), biodegradation parameters, and Bio Traps® in the month prior to beginning the study. Groundwater monitoring for the oxygen injection study will be conducted monthly during the first three months of the 1-year study and quarterly thereafter. Tesoro anticipates that oxygen will be delivered via the WE at a rate of about 3.64 liters per day. Tesoro is also conducting a hydrogen peroxide injection (HPI) pilot study at the southwest property boundary shared with Time Oil in the vicinity of TS-4R. Baseline ._,groundwater monitoring was conducted in four wells described by Tesoro as upgradient well (TO/T-3), treatment zone wells (TS-413, TS/M-2), and downgradient well (TS-5) for four quarters to determine baseline values for total chromium, hexavalent chromium, vanadium, bromide, and bromate. Injection of the hydrogen peroxide into treatment zone wells TS/RW-1 and TS-413 may mobilize these metals. Table 8 lists the laboratory analytical results of the baseline monitoring and the results of twice-monthly sampling following the first hydrogen peroxide injection that occurred on 23 March 2010.