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' 28 May 1999 <br /> AGE-NC Project No 95-0128 <br /> Page 4 of 5 <br />' • TBA was detected in samples from MW3, MW4 and MW7 at concentrations of 18 ,ug/1, 25 <br /> Mcg/l, and 74 4g11, respectively <br /> • DIPE and ETBE were not detected In the ground water samples collected during the 22 <br />' March 1999 ground water monitoring event <br />' Laboratory results of water samples analyzed for petroleum hydrocarbons are summarized in Tables <br /> 2 and 3 The Iaboratory reports for the quarterly monitoring event (MAI Laboratory ID No 05622 <br /> to 05629) QA/QC reports and chain-of-custody form are Included in Appendix B <br /> 4.0. SUMMARY AND CONCLUSIONS <br /> 1 <br /> Based on results of this Investigation AGE concludes <br /> • All properly screened wells on site yield ground water samples that have been impacted by <br /> detectable concentrations of various BTEX compounds and, with the exception of MW7, <br /> petroleum hydrocarbons <br /> • The three monitoring wells with deeper-screened d Intervals yield samples with low <br /> t concentrations of various BTEX compounds and, with the exception of MW 1, by MTBE <br /> The sample from monitoring well MW3 was also Impacted by low concentrations of TAME <br /> and TBA The data suggests that vertically downward migration of petroleum hydrocarbons <br /> I is minor to Insignificant, and also indicates that deeper hydrocarbon-impacted soil horizons <br /> are not significantly impacting the ground water with petroleum hydrocarbons Phis also <br /> suggests that the more significantly impacted ground water Is confined to the upper twenty <br /> feet of the ground water column <br /> • The oxygenating fuel additive MTBE was detected in ground water samples collected from <br /> all the wells with the exception of MW I The lowest concentrations of MTBE (5 5 ugll and <br /> 33 µg/1) were detected In the deeper-screened MW2 and MW3, respectively Compared to <br /> the 44,ug/I to 3,200 yg/I MTBE detected In the properly screened wells in the core area and <br /> In the down-gradient area, the deeper concentrations are suggestive of minor vertical <br /> migration of MTBE <br /> • The MTBE concentration in the up-gradient well, MW7, was 48 ,ug/I, slightly greater than <br /> Ithe concentrations detected in samples from the deeper-screened wells <br /> • The order-of-magnitude decline of dissolved hydrocarbon concentrations In samples from <br /> MW4 and MWS, coupled with an order-of-magnitude Increase in the sample from VW1 <br /> Advanced GeoEnvironmental Inc <br />