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Mr. Jeff Baker • -3- • 11 March 2010 Stockton Terminals Technical Committee 2009, the STTC estimates that the east system and west system had ozone sparge run times of 64 and 86 percent, respectively. Run time difficulties are attributed to system malfunctions and maintenance activities for recent system upgrades. The STTC estimates that historically' about 8,000 pounds of ozone have been injected and 2,600 pounds of hydrocarbons have been destroyed. The STTC monitors the ozone injection 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 RO well exceeds compliance limits. Table 7 shows that the TBA concentration in RO well AR/MW-18B increased from 31 pg/L to 49 pg/L during 2009. 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 Annual Report), 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 would trigger installation of another ozone sparge array east of the trigger wells that include OW-2A, OW-4A, OW-26, and OW-46. During 2009, TPHd, which has displayed an increasing trend in monitoring wells OW-4B and OW-4C, was detected at 1,200 pg/L and 1,300 pg/L, respectively. However, neither OW-4C nor TPHd trigger the contingency plan. STTC member companies Tesoro and BP have conducted pilot studies of remedial technologies on their respective terminals. BP's 29 October 2009 Helium Tracer Study for Biosparging Feasibility Report summarized the results of a two-day A zone biosparge feasibility study on the BP facility to evaluate communication between potential injection and monitoring wells. Based on the results of the study, BP opted to evaluate alternate remedial technologies, including the possible use of passive diffusers. The results of a modified version of the helium-tracer, oxygen-injection pilot study were summarized in Tesoro's 16 December 2009 Helium Tracer Study Report. Based on these observations, Tesoro recommends proceeding with the 1-year, D zone, oxygen injection pilot study proposed in the 27 January 2009 Pilot Study Work Plan and Revised Contingency Plan. Tesoro proposes to install two additional wells: replacement injection well TS/MW-3DR, screened from 110 to 115 feet bgs between TS/MW-3D and TS/MW-2D, and TS/MW-4D screened from 125 to 135 feet bgs. Instead of injecting oxygen, Tesoro recommends using a passive source of oxygen, such as the Waterloo Emitter TM, a down-hole apparatus which is connected to pressurized pure oxygen. Molecular oxygen is diffused, rather than sparged, directly into surrounding groundwater, with the goal of attaining maximum dissolved oxygen (DO) solubility. We concurred with Tesoro's proposal to proceed with the pilot study.