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f 1 28 January 2006 AGE-NC Project No 95-0121 Page 8 of 9 r 4.0. SUMMARY AND CONCLUSIONS The implications from first and second quarter 2005 environmental activities are as follows • The SVE unit operated for approximately 3,360 hours between 22 December 2004 and 11 May 2005, recovering an undeterminable yet minimal mass of hydrocarbons The SVE system was shut down on 11 May 2005, due to lack of detectable concentrations of hydrocarbon in all influent samples during the first and second quarters 2005,and as directed by an EHD letter dated 25 April 2005 f ' The net ground water flow direction for the area bound by wells MW-1 through MW-9 was inferred to range from the northeast to southeast,under a hydraulic gradient of approximately m' 0 001 ft/ft This is in accordance with previous ground water directions and gradients on-site 1 The core of the dissolved petroleum Hydrocarbon plume appears to be located at depths between 25 feet and 53 feet below surface grade (bsg) in the area of wells EW-1, MW-1 ' through MW-4 and MW-7 (Figure 4) The Iack of detectable hydrocarbons in sample collected from shallow soil vapor extraction wells suggest a successful remediation of the shallow soil at the site,except at vapor well VW-1 and VW-3,which are screened into lower ' hydrogeologic units (HU1 and HU2) and not within the vadose zone " • A review of current and previous ground water samples suggests the core of the plume is ' impacted by TPH-g, BTEX and the fuel additives MTBE and 1,2-DCA (Table 5) • The concentration of TPH-g in well MW-1 decreased between April 2000 and May 2005, ' the contaminants in the remaining wells have remained relatively stable, except for well EW-1 which increased between October 1999 to March and significantly during May 2005 BTEX compounds, MTBE and 1,2-DCA are present at concentrations exceeding the DHS' ' Maximum Contaminant Levels for these chemicals in drinking water E E • The lateral and vertical extent of dissolved petroleum hydrocarbons are not fully defined at the site, further lateral assessment may be warranted upgradient west-northwest of well ' MW-7 The dissolved plume is defined north of well MW-2 by CPT-4,north of well MW-4 by well MW-8 and north of well MW-4 by well located east of the site at the Vanco Truck Plaza and east of the site by well MW-5 (Figure 4) 5.0. RECOMMENDATIONS Based upon data collected during the first and second quarters 2005, AGE recommends • Continued performance of quarterly ground water mon itorin events The third quarter 2005 • g event took place on 29-30 September 2005, the fourth quarter event took place on E Advanced GeoEnviroomental,Inc