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IT ' I6 I 18.'April 2003 , '4 ~'I ' k AGE-NC Project No 97-0333 � 'r I II � � I I 'IV I I 5 Ir I I 1 d' 4 Page 10 of111 Y t « Second Zone, Third Zone and the Primary Aquifer'Zone ground water flows were inferred ' to be towards'the north-northwest at approximate gradients of 0 003 ft/ft aor less (Figures 5, 6 an7)d li 1 ,, I �• Due to the glow ground water gradient at the site, small I vanations in ground water, 'i ;I measurements or changes of recharge/discharge of the local ground water could greatly I ' I"I :l. modify the Inferred ground water flow direction The highest on-site 'concentrations tof dissolved MTBE were detected in the'samples i �I Yj collected in the area of First Zone monitoring wells MW-2, MW-6, MW-7A and extraction I n well EW-1 at concentrations as high as 74,000 µg11 Lower concentrations of on-site MTBE G I were detected in water samples from First and Second Zone monitoring wells MW'1,MW-3, MW-4, MW-7 (B-C), 'MW-8 (A-C) and MW-9 (A-B), generally,! significant MTBE ,; I , o I I decreases were reportod In wells MW-1', MW-2, MW-3 and MW-6 (Figures 8 and 9, 4 Table 3) • Lower concentrations of off-site MTBE were (detected in!water samples from First and N ' ' Second Zone monitoring wells MW-10A,MW-fl(A-C),MW-12 land MW-13(A-B) • Concentrations of PCE and/or TCE have been detected in water samples collected from all , well locations associated with the Rainwater Car Wash investigation Minor to significant i PCE and/or TCE concentrnwere detected in 41 of 47'ground water monitohng wells located in Flrst'Zone,Second Zone,Third Zone and Primary Aquifer Zone Aquifers(Figures ' ' 10 and 11, Table 4) The highest concentration of dissolved,PCE;were detected in the I samples collected in the area of on-site wells MW-4 (First Zone)and MW-8 (B, C)(Second ! Zone) and offsite well,MW-12A(First Zone) at concentrations'as high as 2,700 µg/1, k' • PCE and TCE are chlorinated solvents often associated with dry cleaning operations Based on Figures 10 and 11 depicting PCE isoconcentrations in First Zone and Second Zone ' Aquifers; AGE interprets the PCE/TCE-plume to have originated from the dry cleaner's J I ' facility located immediately east of the Rainwater Car Wash ' {l ' ' Low concentrations of TPH-d,were detected at various wells during this ground water ' I monitonng lAGE suspect's that most of the detected TPH-d chromatogram may be due ` I l to the abundance of PCE/TCE peaks detected in the sample chromatograms and/or gasoline I a i interference ,i1L ,o t 7.0 I,I„RECOMMENDATIONS „! I Based upon data collected from the,site, AGE recommends II4 'I IIS I n I I I I Advanced GeoEnvironmental,Inc „ l I i i ilir ' 7I I II I If I,'y � f I IV S I I II IFI