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i <br /> '3 <br /> 15 November 2000 <br /> • AGE-NC Project No 95-0142 <br /> Page 2 of 9 _ <br /> • On 9 and 10 February 1994, ground water monitoring wells MW-1, MW-2 and MW-3 were <br /> installed at the site In November 1994, monitoring well MW-4 was installed at the site <br /> • On 13 June 1995 three soil probe borings were established at the site On the 14 and 15 June <br /> 1995 soil vapor samples were obtained from the site Significant mass of hydrocarbons were n <br /> detected in soil and vapor samples analyzed <br /> • On 25 and 26 September 1995, four soil borings were drilled at the site, borings VE-1, VE-2, <br /> VE-3 and VE-4 were completed as dual-screened soil vapor extraction wells <br /> • On 24 April 1997, soil boring MW-5 was advanced at the site <br /> • On 22 May 1998, four soil probe borings (ASB4 to AS137) were advanced at the site <br /> Hydrocarbon impacted soil was encountered to a depth of 60 feet bsg ' <br /> • On 04 November I998, a deep ground water monitoring well, MW-6 was installed on-site <br /> On 10, 11 and 12 of January 2000, two down gradient, deep ground water monitoring wells, <br /> MW-7 and MW-8, were installed on-site Hydrocarbon impacted ground water was detected <br /> in well MW-6, installed in the former UST area <br /> A total of 18 ground water monitoring events have occurred at the site Soil and ground water on the <br /> site have'been impacted with petroleum hydrocarbons The horizontal extent and stability of the <br /> petroleum hydrocarbon-impacted soil and ground water has been documented <br /> In Corrective Action Plan -November 1995, dated 15 November 1995 (CAP), AGE recommended <br /> implementation of soil vapor extraction in conjunction with in-situ air sparging for remediation of <br /> the petroleum hydrocarbon-impacted soil and ground water at the site At the time the CAP was <br /> prepared, ground water extraction was generally not viewed as an effective and cost efficient method <br /> of ground water remediation, but has gained more favor recently, due to reduced treatment and <br /> disposal costs, as a method to address impacted ground water where air-sparging may not be <br /> controllable or effective Since the approval of the CAP in December 1995, the local and regional <br /> ground water elevation has risen significantly and has maintained an elevation approximately 25 feet <br /> below surface grade (bsg) Also, the vertical extent of hydrocarbon-impacted soil and ground water <br /> has been more fully assessed since the CAP was developed The mass of adsorbed hydrocarbons now <br /> known to be within the saturated zone is significant Recent evaluation of soil and ground water <br /> below 50 feet bsg has documented significant concentrations of dissolved hydrocarbons that must <br /> be satisfactory mitigated to achieve site closure At this time, adsorbed hydrocarbon concentrations <br /> are known to extend to 80 feet bsg, where low concentrations suggest that 80 feet bsg is close to the <br /> 4 <br /> adsorbed plume margin <br /> AGE believes that the sustained increase of ground water elevation will significantly decreased the <br /> potential effectiveness of the proposed SVE/IAS treatment system to address impacted soil and <br /> • Advanced CeoEnvironmental,Inc <br /> F <br />