Laserfiche WebLink
I18 August 1997 <br /> • AGE-NC Project No 95-0128 <br /> Page 3 of 4 <br /> I in VW-1 at concentrations as high as 1,100 ppb (toluene), and MTBE was detected at a <br /> concentration of 2,200 ppb <br /> Tertiary butanol was detected samples collected from monitoring wells MW-6 and MW-7 at <br /> concentrations of 1,100 ppb and 300 ppb, respectively <br /> I TPH-g,TPH-d and BTE&X were not detected in monitoring wells MW-1 through MW-3 However, <br /> MTBE was detected in the sample collected from monitored well MW-2 at a concentration of 12 <br /> ppb These hydrocarbon and MTBE concentrations are not thought to be representative of the upper <br /> ground water zone as the tops of the screened intervals in these wells are 10 feet to 14 feet below the <br /> top of the saturated zone <br /> Analytical results EPA methods 8015 and 8020 for ground water samples are summarized on Table <br /> 2 -Analytical Results of Ground Water SanTples The laboratory report (MAI Laboratory ID 78961 <br /> Ithrough 78968), QA/QC report and chain-of custody are included as Appendix B <br />� . 4.0. CONCLUSIONS AND RECOMMENDATIONS <br /> 41 CONCLUSIONS <br /> The following conclusions were drawn from the results of this quarters investigation <br /> • The highest concentration of detected dissolved hydrocarbons quantified as TPH-g and <br /> overall BTE&X compounds are now located in the vicinity of monitoring well MW-5, <br /> located at the northeast corner of the site, down-gradient of the formes UST excavation <br /> • Concentrations of hydrocarbons (and MTBE) decreased in vapor well VW 1 between April <br /> and July 1997 It is probable that well MW-7 is near the western, up-gradient edge of the <br /> dissolved TPH-g and BTE&X plume <br /> • The increased concentrations of dissolved hydrocarbons in well MW-5 may be an indication <br /> that the dissolved petroleum hydrocarbon plume is not stable and is migrating northward off <br /> the site Because of the probable movement of the hydrocarbons off-site, it is likely that the <br /> PHS-EHD will require additional down-gradient wells to assess the lateral extent of the <br /> dissolved hydrocarbon plume The distribution of TPH-g concentrations in the assessed <br /> portion of the plume, ignoring data from MW-1, MW-2 and MW-3 for reasons stated above, <br /> is depicted in Figure 4 - Dissolved Hydrocarbon Concentrations <br /> • <br /> Advanced GeoEn-,iron mental Inc <br /> I <br />