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24 January 1996 ; <br /> `AGE-NC Project No'95-01,14 <br /> I?age 5 of 6 ,Y <br />�,� ✓. - .r` r F r - 4' •E ' ! x i- '' �� C J ,- . t 1 ~ `k .x, !! <br /> The,ground water gradient in June 1995 were:calculated-to be:0:029 ft/fft flowin ,tfl the n <br /> direction(Figure 3 -Relative.Ground Water Eleyafiori,.Juiie 1995.).-'In December�1995,°the hydraulic <br /> ` gradient•nas,decreased•to 0.006-ftlft but tlhe flow_remained approximately to,thie'northerly'directian <br /> '(Figure 4 =-Relative Ground Xater.Eke afon,.December 1995). Calculated„gradients and flow. <br /> ' •di'recti'ons are relatively consistent withrevious'monitorin 'events. ' <br /> PETROLEUM HYDROCARBONT IMPACTED;GROUND WATER' <br /> During the June' 1995 sampling, TPH-st'0ddard..was detected ;in°MW-I, lNM-2"and MW 3.,av' <br /> concentrations of 130, 520'and.2,100•p.g/l (parts per billion:.ppb),.respectively,: No BT.E&X were <br /> -detected in any'of the samples.`AnalyticaI results of ground water"sanip]es,are siimmarized:in Table. ° <br /> t . , 3.:The laboratory report and chain-of-custody for the June 1995,samples.are incladed in°Appendix".,.," <br /> ppendix'. <br /> D. 3tiA QM l <br /> ' Q During the December 1995.,sampling event, TPI-1-stoddard was detected in MVV-1,•MW-2, and MW- a <br /> 3R.at concentrations of 160, 770 and 4,200 ppb, respectively. I3nt hydrocarbon compounds were, ; <br /> not 'detected -in the other ,samples' analyzed: Analytical 'results of,ground.water samples are' <br /> summarized in.Table 2. The laboratory report•and chain-of-custody for the be'cember'l995 samples <br /> are,included in Appendix E. <br /> 5.0. COMCLUSIONS'AND RECOMMENDATIONS <br /> 5.1:- HYDROCARBON-IMPACTED SOIL AND'RENIEDIATION <br /> No ' etroleum hydrocarbons were-detected'in soil samples collected during the'instnllation of.wells <br /> -3 MW-4 or MW-5. However,hydrocarbon4ni acted'soil remains in the area of the foriiier <br /> UST'excavation and near MW-3. Figure S is'a lithologic'cross-sections of impacted'soil,at'the site'. <br />- '; -,Additional .investigation ri�ay. be required between MW-3 and tlie.foimer .UST excavation to ' <br /> determine•the Iateral extent of impacted`soil <br /> I1 <br /> If remediation ofhydrocarbon=impacted soil is.required,_feasibility'studies,wiIl have`to'be•performed <br /> to determine the most cost=effective remedial.option:•-We recommend-he installation'of three soil <br /> vapor extraction:(SVE) wells at the site and performance of an SVE pilot test: Additionally, soil ,. <br /> ' samples collected during the iristallation of t_he'SVE wells should:under o micabiolo 'ical anal sis`!' ^`R, <br /> g g . y. : <br /> to,determine bioremediation feasibility. Upon completion of feasibility, studies, a Corrective Action_ <br /> Plan (CAP) should:be prepared <br />