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I k v r.+ ? r u,�,%=,k r z• rK x- ti ,k�f+c It , `11 November 1998 ` , k 1 r , AGE-NC Pro}ect No 95-0121 a Page4of5 ' ' could greatly modify ground water flow direction 1 • The ground water surface elevation at the site continues to remain above the slotted screened j hydrocarbon concentrations irn samples intervals in wells MW-1 through MW-9 Therefore, y collected from these wells may `not be representative of concent-ations of dissolved petroleum hydrocarbon in shallow ground water on the site Well screen intervals are fisted ,r in Table 1 I II I I ` round water samples collected from MW-1 through MW_g • From May to August 1998, g , have not exhibited significant increases or decreases of dissolved petroleum hydrocarbon concentrations compared to the range of concentrations detected since February 1991 The greatest concentrations of dissolved petroleum hydrocarbons continues to be in the area of wells MW-1 through MW-4 and MW-7,,near the core of hydrocarbon-impacted soil in wells MV►i-i though MW- is depicted • The approximate distribution of dissolved TPH-g k lls MW-1 through MW- in Figure 4 The approximate distribution of dissolved benzene in wet N l9 is depicted in Figure 5 L y • orted that The laboratory rep samples collected from MW-1 through MW-4 and MW-7 may astle not have had typical diesel chromatographicpatterns,Eand hat the detected hydrocarbons historically,representatives may be Analytical Laboratory have suggested to AGE an the result of gasoline interference ' Concentrations of benzene detected in samples collected from MW-1 through MW-4 and • MW-7 were above the State of California Maximum Contaminant Level(MCL)for drinking t water of 10 ppb t Concentrations of toluene exceeded the MCL of 150 ppb in samples from wells MW-1,MW- • 2,MW-3 and MW-7, concentrations of ethylbenzene exceeded the MCL of 700 ppb in the samples collected from wells', MW-] MW-2 and MW-3 Concentrations of xylenes exceeded 4 the MCL of 1750 ppb in the samples collected'from wells MW-1 and MW-3 Utillzang EPA Methods 8260,the concentrations of MTBE detected from wells MW-1,MW- MTBE was ' r 2 and MW-5 ranged between 4 0 ppb to,120 ppb, utilizing EPA Method 8020, detected from wells MW-5, MW-6 and MW-9 at concentrations as high as 4 5 ppb tilizin EPA method 8260, concentrafions of TBA were detected in the ground water • U g sample collected from well MW-:1 at 300 ppb;,Concentrations of ETRE, TAME and D1PE were not detected above the laboratory reporting limits I t r 5{ Advanced GtoEniveronmental,Inc r , li , S I I 1 1