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1 <br /> 09 May 2005 <br /> AGE-NC Project No 97-0301 <br /> Page 5 of 6 <br /> • Generally,a steep downward vertical gradient was observed from wells MW-8,MW-9,and <br /> MW-12 and between the Second Water Zone, Third Water Zone, and Fourth Water Zone, <br /> near neutral vertical gradients were observed between the First Water Zone and the Second <br /> ' Water Zone in the southern portion of the site (Figure 3) <br /> • Analysis of ground water samples collected from MW-1 and MW-7 suggest the dissolved <br /> plume is comprised of TPH-g, BTEX, and 1,2-DCA The core of the First Water Zone <br /> dissolved gasoline plume appears to be currently distributed near the location of wells MW-1 <br /> and MW-7, and contained within network of wells consisting of MW-2, MW-3, MW-4, <br /> MW-6, M A' MW-1 A, MW-11A, and MW-12A (Figure 5)N <br /> • TPH-g was detecteU f r the first time at well MW-9A, and may suggest a slight shift in the <br /> plume towards the southeast <br /> i • Substantial concentrations of dissolved TPH-d and TPH-k have previously been detected in <br /> water samples collected from wells MW-1 and MW-7, indicating a limited distribution of <br /> ' TPH-d and TPH-k in the area assessed However, for the sixth consecutive quarterly <br /> monitoring event,TPH-d,TPH-k,and TPH-mo were not detected from any of the twenty-six <br /> water samples analyzed }2pI 1�5 <br /> • BTEX and 1,2-DCA concentrations in ground water samples MW-1 and MW-7 were a <br /> substantially above their respective Maximum Contaminant Levels in drinking water <br /> 10 Very low concentrations of MTBE,TAME, and TBA have been detected at wells �l, <br /> MW-1, MW-2, MW-3, MW-4, MW-6, and MW-7, indicating that there is only a minor <br /> impact of these components <br /> • Based on the past six quarterly ground water monitoring events,the lateral and vertical extent <br /> of dissolved petroleum hydrocarbons appears to be limited to First Water Zone wells MW-1 <br /> and MW-7 at the site and approximately 50 feet east of the site <br /> ' SA. RECOMMENDATIONS <br /> Based upon data collected during the 4`h Quarter 2004, AGE recommends <br /> • Continued groundwater monitoring utilizing wells MW-1 through MW-12,the first quarter <br /> 2005 ground water monitoring event was performed on 15 March 2005 <br /> • If applicable,conduct future ground water monitoring events concurrently with the Cal-Tank <br /> Lines site (3105 South El Dorado Street) <br /> • Continued quarterly depth-to-water measurements in all monitoring wells at the site, but <br /> ireduced ground water sampling frequency at wells MW-2,MW-3, MWA and MW-6 from <br /> Advanced GeoEnnronmental,Inc <br />