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J e M i 1 28 April 1998 n AGE-NC-95-0103 ' Page 8 of 9 ! 1 1 ' from well MW-4 east of'the former gasoline USTs location Hydrocarbons were also detected at lesser concentrations in wells MWA, MW-3 and MW-5 Detectable concentrations hydrocarbons were not present in the samples collected from the off-site wells, ' MW-2 and MW-6 and no hydrocarbons were detected in newly installed well MW-7, east of well MW-4 • A reduction of the dissolved-phase hydrocarbon plume concentrations in the central portion of the site has occurred since the initiation of the remediation system Additionally, a reduction of hydrocarbon concentrations has occurred at the location of well MW-5 A slight decrease of hydrocarbon concentrations has occurred in the down-gradient well MW-3 during the last quarter A portion of the observed drop of dissolved hi drocarbons may be due to ground water being approximately 5 feet above the screened intervals of MW-1 through MW-4 r ' • DIPE was detected in water samples collected from MW-3 and MW-5, with a maximum concentration of 85 ppb in MW-5 MTBE was detected in samples collected from MW-1 and MW-4, with a maximum concentration of 55 ppb in MW-4 TBA was not detected in any groundwater samples this quarter Dunn g operation of the SVE system during this quarter, an estimated 65 gallons of gasoline E were removed from the site Since initiation of the SVE system an estimated-total of 381 gallons of gasoline have been removed E • I The'SVE system has removed a major portion of the hydrocarbons from the�adose soil zone in the SVE system's area of influence Soil contamination probably remains in saturated soil r in the core portion of the dissolved hydrocarbon plume ; J• Benzene concentrations in the extracted soil vapor has been reduced to concentrations bel ow r the detection limits of the soil vapor analytical method 8020 ! 11 1 I� 5.0. ' RECOMMENDATIONS , ased upon data collected over the quarter at site, AGE recommends the following ,1 stallation of additional IAS point or wells to stimulate remediation of impacted ground ' ater in the area of well MW-4 and the southeastern quadrant of the remediation area A E work plan for the installation of the sparge,points and costs have been approved 4 I ! u , 1 • perate of the SVE system drawing,vapors from the central portion of the site, which has ! ' emonstrated hydrocarbon-impacted soil vapor. The SVE should be operated for an J Y I Advanced GCOEnvironmental,Inc !I I