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Quarterly Report-Third Quarter 2007 4 PACIFIC CAR H 4405 Pacific Avenue,Stoc California PREPARED FOR: Mr.Jerry Castro 7PACIFIC CAR WASH 10 January 2008 AGE-NC Project No.96-0229 Page 5 of 6 mean sea level(Table 2). • First Zone ground water flow direction at the site inferred a net ground water flow towards the northeast at an average hydraulic gradient of approximately 0.004 ft/ft(Figure 4). • Second Zone ground water flow direction at the site inferred a net ground water flow direction towards the east at an average hydraulic gradient of approximately 0.006 fuft (Figure 5). • The most intense TPH-g-impacted ground water was reported in the area of wells MW-2 and more severe at MW-6 (down-gradient), at concentrations as high as 80,000 µg/1. The dissolved TPH-g plume appears to be delineated in all directions,and is confined by wells MW-4,MW-5,MW-7 through MW-12,MW-16 and MW-18(Figure 6). • The most intense MTBE-impacted ground water was reported in the area of well MW-10A (screened 23-43 ft)at a concentration of 83 pg/l(Table 3).MTBE was also reported from wells MW-6 and MW-10B(screened 50-55 ft) this quarter.MTBE was not detected in any other sample analyzed this quarter.The MTBE plume appears to be defined in all directions (Figure 7). • Concentrations of 1,2-DCA were detected in the samples collected from wells MW-1, MW-2,MW-3,MW-6,MW-7,MW-10A,and MW-1 OB(Figure 8).The dissolved 1,2-DCA plume appears to have migrated down-gradient at least to the areas of wells MW-3, MW-7 and MW-10,but not beyond the areas of wells MW-9,MW-12 and MW-16.The vertical extent appears to be defined on-site by multilevel well MW-13(A-D)and off-site to the northeast by multi-level well MW-17(B-C). 5.0. RECOMMENDATIONS Based upon data collected during September 2007,AGE recommends: • Continued quarterly ground water monitoring and sampling of selective monitoring wells at the site.A quarterly ground water monitoring event(fourth quarter 2007)was performed at the site on 28 December 2007 and a report of findings is forthcoming.The first quarter 2008 ground water monitoring event has tentatively been scheduled to occur in March 2008. Reduction of the sampling frequency at wells MW-4 MW-5 and MW-12 through MW-18 (wells with at least four consecutive events with no detection of petroleum contamination) from quarterly to annual;annual sampling of these wells will be Performed during the first uarter of each year - Ad—cel GeoEnAronmenul,Inc. MM JOAO M CO�A soE.E. Andmommik _ on APPMW two aMwW tnftM r A owe": A�InMMr - � diffff��MMS