SITE INFORMATION AND CORRESPONDENCE

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Mr. Shelby Lathrop - 2 - 16 November 2007 Former Tosco Bulk Terminal No. 100 ._ (TPHg), di-isopropryl ether (DIPE), ethyl tertiary butyl ether (ETRE), and tertiary amyl methyl ether (TAME). However, concentrations of these constituents are significantly diminished. Most recently, TBA, TPHd, and MTBE have had the highest concentrations. During 2007, A- zone well MW-2 contained the maximum TBA concentration of 670 micrograms per liter (pg/L). TBA was also detected in the B-zone at 82 pg/L in MW-21 B and in the C-zone at concentration of 46 pg/L in MW-22C. Downgradient well MW-20 had the maximum MTBE concentration at 15 pg/L, and downgradient well MW-18C had the maximum TPHd concentration at 97 pg/L. Concentrations of TPHg, TPHd, MTBE and TBA, which were once detected at thousands of pg/L in source area wells MW-14 and MW-8, were largely non-detect in these wells in 2007, with the exception of TPHd and MTBE which were detected below their respective water quality objectives (WQOs). The proposed Pilot Study will consist of injecting oxygen into nine A-zone (IP-1 to IP-9) and three B-zone (IP-10 to IP-12) injection points to enhance the biodegradation of residual CDCs. Oxygen injection is proposed for a 60-day period using bottled oxygen at a rate of about 13 pounds (lbs) per well per day. The objective will be to maintain dissolved oxygen levels at 10 milligrams per liter (mg/L) or greater. Groundwater monitoring to characterize baseline, source area, downgradient and C zone conditions is proposed from eight groundwater monitoring wells (MW-2, MW-8, MW-10, MW- 14, MW-16, MW-17B, MW-19C, and MW-20). The baseline monitoring analyte list will consist of field parameters including dissolved oxygen (DO) and ferrous iron, select metals including chromium, TPHg TPHd, oxygenates, select nutrients, methane, biochemical oxygen demand (BOD), chemical oxygen demand (COD), and heterotrophic aerobic bacteria plate count. Following initiation of the test, groundwater monitoring for this list of analytes will be conducted from these eight monitoring wells at 60 days, three months, and six months. Prior to and immediately subsequent to oxygen applications, for the first five days, DO concentrations will be measured in the field in monitoring wells MW-2, MW-8, MW-14, MW-16, MW-17, MW-19C, MW-20, and piezometers P1 through P6. ConocoPhillips proposes to review pilot test monitoring results with Regional Water Board staff after the initial 60-day test of oxygen injection capacity to assess whether the application frequency and/or oxygen application rate should be adjusted to more or less than the anticipated 13 Ib per day rate for the remainder of the 60-day test. Based on discussions with Regional Water Board staff, ConocoPhillips will determine whether an additional 60-120 days of application are appropriate. If concentrations of analyzed constituents are observed in excess of baseline concentrations, ConocoPhillips proposes to reduce or cease oxygen injections based on discussions with Regional Water Board staff. ConocoPhillips will submit a remedial implementation start-up report within four weeks of initiating oxygen injections and summary reports and after collection of the three-month and six-month samples. If little or no change to groundwater quality is evident, ConocoPhillips will propose in their summary report to continue to implement the oxygen injection events. Our comments are provided below. 1. Regional Water Board staff concur with implementation of the Pilot Study as proposed by ConocoPhillips. Please provide 48 hours notification prior initiation of the test and submit a