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f SEC0R 1 E soil samples collected from MWA to MW-3 are at 11 feet bgs. All soil samples from MW-3 were non- detected (ND). TPHg was detected at 536 mg/kg at MWA at 11 feet bgs and at 6.49 mg/kg at MW-2, also at 11 feet bgs. Benzene and MTBE.were not detected in any soil samples from these wells. Toluene and xylenes were found in only one soil sample at MWA at 11 feet bgs (0.29 mg/kg and 2:25 mg/kg, respectively). The 21-foot samples at MW-1 and MW-2 did not have any chemical detections. Since groundwater was first encountered at 11 feet bgs at the Site, soil concentrations reported:at 11 feet bgs should be due to groundwater smear and not an indication of vadose zone soil impact. These results show that the extent of soil contamination at the Site is very limited, both vertically and laterally. Historical ' soil and groundwater data-from this investigation are presented in Table C-2 of Appendix C. 4 Groundwater Monitoring and Sampling L Quarterly groundwater monitoring activities have been conducted at the Site since June 2000." MW-3 is located about 15 feet cross gradient of the most impacted area of D-11PL-61ND4. MW-2 is located about 30 feet downgradient from D-21SD4. MW-1 is located about 30 feet downgradient from less impacted soil ' locations (D-4 and PL-2) Groundwater samples collected during the installation of MW-1 to MW-3 (June ' 2000), indicated the presence of only MTBE (45.4 micrograms per liter jpglL] and 16.6 pg/L at MWA and MW-2, respectively) and 1,2-dichloroethane (1,2-DCA) (2.34 pglL at MW-2). Other gasoline constituents such as TPHg and benzene, toluene,_ ethylbenzene, and xylenes (BTEX) were not detected in the June 2000 groundwater samples. Groundwater monitoring data to date (March 8, 2007) indicated that MW-1 reported the highest concentrations of TPHg (613 pglL on 9108100) and MTBE (170 pg1L on 6125101). Benzene,was'detected i only four times at MW-1, at 3.4 pglL on 3122101, 1.6 pglL on 9105106, 3.8 pg/L on 12107106, and 1.5 pglL on 3108107. MTBE was detected only twice at MW-1: 0.5 pg/L on 12/07/06 and 0.76 pg1L on 3108107,.at or near its detection limit of 0.5 pg/L: The highest levels of chemical constituents at MW-2 were reported on 9109102 (170 NgIL of TPHg, 14' pg1L of benzene, and 120 NgIL MTBE). Tert-butyl alcohol (TBA) (detected once at 28'pg/L on 9109102), ethanol (detected once at 170 pg1L on 5126105), 1,2-DCA (detected at 0.94 pg/L to 2.3 pglL from 6123100 to 3114103), and MTBE (detected at 0.69 pglL on 12/07/06 and 0.77 pg/L on 3108107) were also found at MW-2 in the past. Most constituents at MW-3 have been ND, except MTBE at very low levels (0.55 pg/L to 1.8 pg/L from 12/03/01 to 12106102), ethanol (detected once at 290 pglL on 5126105), 1,2-DCA(detected at 0.5 pglL to 0.89 pg1L from 12/03/01 to 3114103), and di-isopropyl ether(DIPE) (detected at 13 pglL on 12107106.and 10 pg/L on 3108107). Within the recent four monitoring events from 6115106 to 3108107, DIPE was detected twice at MW-3 ('I3 pg/L on 12/07/06 and:10 pg/L on 3108107); MTBE was detected twice at MW-2 (0.69 pglL on 12/07/06 - and 0.77 pg/L on 3108107) and at MW-1 (0.5 pglL on 12/07/06 and 0.76 pg/L on 3108107); and benzene was detected three times at MW-1 (1.6 pg/L on 9105106, 3.8 pglL on 12107106, and 1.5 pg/L on 3108107). These levels were below(MTBE) or slightly above (benzene)their respective maximum contaminant level (MCL)established by the State of California (13 pglL for MTBE and 1 pg1L for benzene) (RWQCB,2003). _ Historical groundwater analytical data tables are presented in Table C-3 of Appendix C. 4 i