SITE INFORMATION AND CORRESPONDENCE

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Mr. Jeff Baker • -2 - • 11 March 2010 Stockton Terminals Technical Committee site. STTC recommends that monitoring wells on the nearby Kinder Morgan Energy Partners (KMEP) facility should also be resurveyed for consistency. Since 20 September 2002, the STTC has utilized Soakease"m separate phase hydrocarbon (SPH) removal socks in four wells to remove SPH. No measurable SPH or SPH sheen was observed in wells during the fourth quarter. As shown in Tables 6 and 7, during the fourth quarter 2009, the highest COC concentrations generally occurred in A zone wells in the BP aboveground tank (AGT) area and on the Tesoro property. The highest concentrations of TPHg and TPHd were in AR/MW-8A and TS/M-2, at 98,000 micrograms per liter(pg/L) and 280,000 pg/L, respectively. The highest concentration of benzene was detected in AR/MW-11 B at 9,200 pg/L. The highest concentrations of MTBE and TBA were detected in AR/MW-50 at 13,000 pg/L and 4,000 Ng/L, respectively. After increasing since 2001, the MTBE concentration in AR/MW-8A generally declined during 2009 from 9,000 pg/L in the first quarter to 6,600 pg/L in the fourth quarter. Groundwater at the BP facility is polluted with MBAs from a November 2008 fire suppression foam release. The water quality objective for MBAs is 500 pg/L. To address the concentrations, BP over-purges up to 10 well casing volumes from wells containing MBAs before sampling. Purge water is hauled offsite for treatment and disposal. In response to Central Valley Water Board staffs 8 October 2009 letter, BP increased the number of monitoring wells in which monitoring for MBAs is conducted from 29 to all 40 of the AR/MW monitoring wells. Table 6 shows that MBAS detections on-and off-site ranged from 120 pg/L to 960 Ng/L. BP's 28 September 2009 Work Plan for Interim Response (Work Plan) proposed to continue quarterly over-purge events in all on-site.monitoring wells where MBAs exceeds the water quality objective (WQO) of 500 pg/L until sampling results show MBAs is less than or equal to 500 pg/L for four consecutive quarters. BP describes over-purging as the process of removing 10 well casing volumes from a monitoring well prior to sampling. Previously, there were 12 wells that had MBAs above 500 pg/L. They were AR/MW-3A, AR/MW-5A, AR/MW-5C, AR/MW-6AR, AR/MW-8A, AR/MW-8B, AR/MW-11A, AR/MW-116, AR/MW-13A, AR/MW-13C, ARIMW-14B and AR/MW-23A, During the fourth quarter, MBAs in 14 wells exceeded 500 pg/L. However, BP purged only 10 wells. Previous MBAs concentrations in AR/MW-14B exceeded 500 pg/L. However, no monitoring or purging was conducted in AR/MW-14B during the fourth quarter because the well was inaccessible. AR/MW-5C had insufficient water. MBAs concentrations in AR/MW-1 C, AR/MW-18C, and AR/MW-22A ranged from 630 pg/L to 930 pg/L. However, these three wells were not over-purged. Of the 10 wells over- purged by BP, MBAs concentrations increased in four wells and decreased in six wells. 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 5 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