ARCHIVED REPORTS_XR0008139 - Laserfiche WebLink

Home Browse Search

17 November 1999 AGE-NC Project No 95-0128 Page 6 of 7 • The MTBE concentration in the up-gradient well, MW7, was 38 4g/l, slightly greater than the concentrations detected to samples from the deeper-screened wells • The decline of dissolved hydrocarbon concentrations in samples from MW6 and VW1, coupled with more than an order-of-magnitude increase in the samples from MW4 and MW5 compared to the March 1999 monitoring event are consistent with a shift of ground water flow direction from northwesterly in March 1999 to northeasterly in July 1999 Based on results of the 27 October 1999 investigation AGE concludes • All properly screened wells on site yield ground water samples that have been impacted by detectable concentrations of various BTEX compounds with the exception of MW7 All Iproperly screened wells also yield water samples that have been impacted by detectable concentrations of TPH-g with the exception of MW6 and MW7 I • The three monitoring wells with deeper-screened intervals yield samples with detectable levels of various BTEX compounds and petroleum hydrocarbons, with the exception of MW 1 which does not contain detectable concentrations of petroleum hydrocarbons The deeper-screened monitoring wells do yield samples with low concentrations of MTBE The sample from monitoring well MW3 was also Impacted by a low concentration of TBA The data suggests that vertically downward migration of petroleum hydrocarbons is minor to insignificant, and also indicates that deeper hydrocarbon-impacted soil horizons are not significantly impacting the ground water with petroleum hydrocarbons This also suggests that the more significantly impacted ground water is confined to the upper twenty feet of the ground water column • The oxygenating fuel additive MTBE was detected In ground water samples collected from all the wells The lowest concentrations of MTBE (2 7 µgll and 10,ug/l) were detected in the 4 deeper-screened wells MW 1 and MW2, respectively Compared to the 68,ug/l to 230 µg11 MTBE detected in the properly screened wells in the core area and in the down-gradient area, the deeper concentrations are suggestive of minor vertical migration of MTBE • The MTBE concentration in the up-gradient well, MW7, was 11 ggll, slightly greater than the concentrations detected In samples from the deeper-screened wells • The order-of-magnitude decline of dissolved hydrocarbon concentrations in samples from MW6 and VW1, coupled with an order-of-magnitude increase in the sample from MW4 compared to the July 1999 monitoring event are consistent with a more easterly shift of ground water flow direction from July 1999 to October 1999 Advanced CeoEnveronmental Inc I