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it ! 16 December 2005 • AGE-NC Project No 98-0465 ! I" Page 3 of 6 , ' Wells MW-1 through MW-4, and wells MW-2 through MW-7 on the adjacent site were used to model ground water flow direction and calculate the gradient The ground water flow direction was inferred generally towards the northeast at the former UST location,the flow across the site and the adjacent Sanchez site ranges from northwesterly to northeasterly (See Figure 3) The hydraulic ' gradient was determined to be 0 002 feet/feet(ft/ft)across the majority of the site,including the UST T location, and 0 003 ft/ft or at the northeast corner of the site Figure 3 Illustrates the contoured ' ground water elevations as measured on 15 July 2005 t ' 3 2 ANALYTICAL RESULTS OF QUARTERLY GROUND WATER SAMPLES L BTEX compounds were not detected at concentrations at or above the laboratory reporting limits in ' any of the ground water samples TPH-g was detected in the ground water sample collected from MW-1 at a"concentration of 350 µg/1 ' MTBE was detected in samples collected from MW-1 and MW-3 at concentrations of 350 µg11 and 12!µg/l,respectively While the contaminant level detected In MW-1 rose significantly from the last quarterly monitoring event(see Table 1), no other monitoring well showed this increase No other ' . fuel oxygenated compounds were detected in the ground water analysis at or above laboratory detection limits ' Analytical results of groundwater samples are summarized in Table 1 The laboratory report(CTEL Project No CT214-0507091), quality assurance/quality control report, and chain of custody forms ' are included in Appendix E Documents confirming the upload of laboratory electronic deliverable format (EDF) files and depth to"water measurements to GeoTracker are included in Appendix F I ! 4.0. CONCEPTUAL SITE MODEL The site is located on essentially flat land that is developed into a convenience store and fueling facility,the majority of the ground surface is covered by asphalt'(Figure 2) Based on data collected ' to date from soil borings and monitoring well installations,AGE developed a conceptual site model for the release,migration and distribution of the contaminants in the subsurface,which was included in the 2°d,Quarterly Monitoring Report 2005 1 Site assessment activities to date identified the area where subsurface soil appears to be impacted by petroleum hydrocarbons, soil is impacted at the former UST location and appears to be confined to the former UST pit/over excavation area Laboratory analysis of soil samples collected from beneath the former USTs detected total petroleum hydrocarbons quantified as gasoline and diesel ' Advanced GeoEnvironmental,Inc 1 f I }