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28 August 2012 <br />AGE-NC Project No. 02-0926 <br />Page 3 of 3 <br />Shallow zone dissolved TPH-g, BTEX, 1,2-DCA, EDB and TAME are undefined to <br />the west of well MW-5 and to the east of boring B-6. The dissolved ground water <br />plume appears to be defined in all other directions. <br />The core of the plume appears to be centered around the former underground <br />storage tank area, surrounding well MW-5 and generally radiates towards MW-3 <br />south of the UST area. Dissolved TPH-g concentrations in well MW-5 have <br />increased since it the last monitoring event was performed on 16 May 2012. BTEX <br />constituents have also increased at the well MW-5 location; generally near the <br />former UST area. However, based on historic sampling results BTEX concentrations <br />appear to have significantly decreased as a result of air-sparging. It is likely that <br />increases in hydrocarbon concentrations can be attributed to the significant <br />adsorbed mass "drowned" beneath the water table, which desorbed following air- <br />sparge termination. <br />Hydrocarbon concentrations were reported for the first time in four monitoring <br />events in deep monitoring well MW-6. The reported concentrations are much lower <br />than concentrations in shallow impacted well MW-5 and should continue to provide <br />vertical definition to the underground storage tank area. Additional assessment of <br />does not appear warranted at this time. <br />5.0. RECOMMENDATIONS <br />Based on the conclusions presented in this report, AGE recommends continuation of <br />reduced ground water monitoring. A semi-annual monitoring event will be scheduled during <br />the first quarter of 2013. Further AGE-recommends approval of the recommendations to <br />prepare a corrective action plan and final remediation plan for the site. <br />6.0. LIMITATIONS <br />Our professional services were performed using that degree of care and skill ordinarily <br />exercised by environmental consultants practicing in this or similar localities. Findings were <br />based upon field measurements and analytical results provided by an independent <br />laboratory. Evaluation of the hydrogeologic conditions at the site for the purpose of this <br />investigation are made from a limited number of available data points (i.e. ground water <br />samples), and subsurface conditions may vary away from these data points. No other <br />warranty, expressed or implied, is made as to the professional interpretations, opinions, <br />and recommendations contained in this report. <br />Advanced GeoEnvironmental, Inc.