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Ms Mary Meays Page 3 August 12, 1996 Former Tank Site #1 As observed in Table 1, as in previous sampling rounds,TPH(gasolme) was detected at only one site (MW-5, 2 4 mg/1) Diesel was reported at low concentrations (0 180 mg/l and 0 440 mg/1) in both samples for which it was analyzed As in previous sampling events, BTEX compounds were only detected in the sample collected from MW-5 Benzene (0 590 mg/1), ethylbenzene (0 033 mg/1), and total xylenes (0 019 mg/1) were detected at concentrations consistent with past sampling events Toluene was not detected in any of the wells As presented in Table 1, these TPH and BTEX detections are similar to those associated with recent sampling events Former Tank Site #2 As observed in Table 2, as in past sampling events, TPH(gasoline and diesel) and BTEX detections only occurred in samples collected from MW-1A and MW-2A The highest concentrations were associated with the sample collected from MW-1A, which is located in the immediate vicinity of the former tank In this sample, TPH(gasoline) and TPH(diesel) were detected at concentrations of 5 1 mg/l and 0 8 mg/l, respectively Benzene (12 mg/1), toluene (0 030 mg/1), ethylbenzene (0 180 mg/1), and total xylenes (0 130 mg/1) were also detected in this sample These TPH and BTEX detections are similar to those associated with recent historical monitoring events REMEDIATION APPROACH Catellus has evaluated several options for remediation of TPH-impacted ground water at the West Weber sites to address PHS/EHD's stated opinion that additional ground water remediation will be required Catellus believes that the minor impacts to ground water do not necessarily warrant remediation, particularly in view of the limited uses of the shallow aquifer However, Catellus recognizes PHS/EHD's concerns regarding protection of ground water quality and is willing to perform limited additional remediation to address this stated concern and accomplish closure Based on site conditions and the nature and extent of impacted ground water, Catellus has determined that enhanced bioremediation is the preferred remediation approach, should remediation ultimately be required Bioremediation is an aerobic process that metabolically transforms organic compounds (i e , hydrocarbons) to harmless by-products (i e , CO2, water, and biomass) using micro-organisms Oxygen Release Compound (ORC) bioremediation is an enhanced insitu bioremediation process by which oxygen is delivered to the impacted aquifer This remediation technology requires that the aquifer has sufficient amounts of nutrients such as phosphorus, nitrogen, and hydrocarbon to support the micro-organisms The significant reduction in