SITE INFORMATION AND CORRESPONDENCE

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Mr. Jeff Baker Stockton Terminals Technicommittee 2 • 16 June 2010 As shown in Tables D-1 through D-4, during the first quarter 2010, the highest COC concentrations generally occurred in A zone wells in the BP aboveground tank (AGT) area. In the deeper zones, maximum concentrations were encountered on the Tesoro property. The highest concentrations of TPHg and TPHd were in AR/MW-8A and AR/MW-10A, at 94,000 micrograms per liter (pg/L) and 210,000 pg/L, respectively. The highest concentration of benzene was detected in TO/WC-26 at 9,700 pg/L, The highest concentrations of MTBE and TBA were detected in AR/MW-50 at 9,700 pg/L and 7,800 pg/L, respectively. Groundwater at the BP facility is polluted with MBAs. BP believes the pollution originates from a November 2008 fire suppression foam release. The water quality to 10 well casing volumes from wells containing MBAs before objective (WQO) for MBAs is 500 pg/L, To address the concentrations, BP over-purges up sampling. BP describes over-purging as the process of removing 10 well casing volumes from a monitoring well prior to sampling. Table 6 shows that the maximum MBAs detection was 1,900 pg/L in AR/MW-9B. Until the fourth quarter 2009, there were 17 wells in Which MBAs was ever detected at or above 500 pg/L. During the first quarter 2010, this number increased to 22. MBAs concentrations exceeding 500 pg/L were observed for the first time in AR/MW-5B, AR/MW-50, AR/MW-8C, AR/MW-9B, AR/MW-10C, AR/MW-11C, and AR/MW-21 C. In the fall of 2004, the STTC began operation of two ozone sparge (OS) systems to clean up groundwater pollution migrating downgradient from the Site. The system is comprised of 57 A zone and 16 B zone wells connected to two 2 pounds-per-day (lbs/day) ozone generators. The OS system is divided into two portions. The west system is downgradient of Tesoro, and the east system is downgradient of BP. During the first quarter, the STTC estimates that the east system and west system had ozone sparge run times of about 90 and 75 percent, respectively. Run time difficulties are attributed to system malfunctions and maintenance activities for recent system upgrades. The STTC estimates that historically, about 8,500 pounds of ozone have been injected and 2,800 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 decreased from 49 pg/L to 44 pg/L during the first quarter. 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 First 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 would trigger installation of another ozone sparge array east of the trigger wells that include OW-2A, OW-4A, OW-26, and