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Mr. Jeff Baker - 3 - 20 August 2009 Stockton Terminals Technica*mittee 0 quarter. The improved run times are attributed to recent system upgrades. The STTC estimates that historically, about 7,420 pounds of ozone have been injected and 1,476 pounds of hydrocarbons have been destroyed. The STTC monitors the ozone injection system using 12 A and S zone wells. A contingency plan is triggered if the concentrations of BTEX, MTBE or TBA in any remedial observation wells exceed compliance limits. Table 7 shows that the TBA concentration in RO well AR/MW-18B has increased from 9.7 pg/L to 36 pg/L over the last four quarters. These concentrations exceed the compliance limit of 6.6 pg/L. Pursuant to the terms described on Page 3 of the Revised Contingency Plan (Appendix K of the Second QMR), three consecutive exceedences of an order of magnitude greater than the compliance limit will trigger installation of a second ozone sparge array east of the RO wells. None of the concentrations measured so far has been an order of magnitude above the compliance limit. 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 trigger installation of a third ozone sparge array east of the trigger wells that include OW-2A, OW-4A, OW-2B, and OW-4B. During the second quarter, TPHd, which has displayed an increasing trend in monitoring wells OW-4B and OW-4C, was detected at 2,100 pg/L and 2,000 pg/i, respectively. However, TPHd is not on the list of constituents that trigger the contingency plan. STTC member companies Tesoro and BP are conducting or planning pilot studies. The 27 January 2009 Pilot Study Work Plan and Revised Contingency Plan (Work Plan) described the initial approach to conducting the helium-tracer, oxygen-injection pilot study at TS/MW-3D. The 13 April 2009 Response to RWQCB March 112009 Letter provided additional details, including a proposal to conduct monthly baseline groundwater monitoring consisting of biodegradation data and field parameters including dissolved oxygen (DO) for up to three months prior to initiating this pilot study. The 1 May 2009 Implementation Schedule for Oxygen Injection Pilot Study states that groundwater quality sampling would be conducted during May- However, a 4 August email informed Central Valley Water Board staff that the pilot study had been delayed about one month due to technical difficulties. Tesoro's 3 June 2009 May 1, 2009 Meeting Summary (Meeting Summary) clarifies that background sampling for the TS/RW-1 hydrogen peroxide pilot test will be conducted in four wells including TONT-3, TS-4R, TS/M-2, and TS-5 for hexavalent chromium, vanadium, and bromate. Sampling is scheduled to occur for at least three quarters prior to beginning peroxide injections. Although not discussed in the text, Appendix D of the Second QMR contains laboratory reports of the first quarter of background sampling. The results show that hexavalent chromium (Cr VI) is present in two of.the four wells at 21 pg/L and 44 pg/L. Vanadium concentrations ranged from 42 tag/L to 650 pg/L. Three of the four wells were sampled for bromide instead of bromate. TONT-3 was not sampled for this element. Bromide concentrations ranged from 290 pg/L to 1 ,100 pg/L. The Central Valley Water Board has not adopted a WQO for bromide. The California Public Health Goal (PHG) of 0.1 pg/L is the WQO for bromate_