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07 May 1999 • AGE-NC Project No 95-0104 Page 7 of 8 • Dissolved petroleum hydrocarbons were not detected in properly screened wells MW-1 and ' VW-1 • The January 1999 monitoring event reported samples from wells MW-1, MW-6 and VW-1 ' to contain substantial dissolved petroleum hydrocarbons However samples from these same wells did not contain concentrations of dissolved petroleum hydrocarbons above laboratory reporting limits during the April 1999 monitoring event I • A substantial decrease in dissolved petroleum hydrocarbons was observed from well MW-5 between the January 1999 and April 1999 ground water monitoring events TPH-g decreased from 630µg/1 to 120µg/l, BTEX constituents decreased from concentrations as high as 130 µg11 to non detect levels Based upon data collected between March 1999 and April 1999 SVE/lAS pilot test,AGE concludes • The SVE/lAS pilot test was operational for 590 hours • Flow rates ranged from 20 to 78 standard cubic feet per minute (scfin) at 0 15 to 2 15 inches • of water of differential pressure • The induced vacuum stabilized at approximately 0 75 inches of water during the pilot test I • Hydrocarbon vapor field measurements ranged as high as 3,760 ppm at the beginning of the pilot test and were recorded as low as 650 ppm near the end of the pilot test (Table 4) • TPH-g was detected in vapor samples collected from VW-1 at concentrations ranging as high as 11,000 µg/1 • BTEX compounds were detected in vapor samples collected from VW-I at concentrations up to 810,ugll Concentrations of benzene were encountered from VW-I at concentrations ranging between 2 8 µg/l and 15 µg/1 I • The mass of hydrocarbons extracted from VW-1 between 18 March 1999 and 16 April 1999 was calculated to be approximately 81 gallons of petroleum hydrocarbons (Appendix E) • Based on mass/volume calculations of impacted petroleum hydrocarbon soil remaining at ' the site (Revised Corrective Action Plan - January 1997, dated 18 February 1997), the apparent volume yields approximately 300 gallons remaining in impacted soil at the site Based on calculating the removal of 81 gallons of petroleum hydrocarbons (Appendix E), then 590 hours of SVEAAS operation effectively removed approximately 27 percent of soil petroleum hydrocarbon impact at the site • As noted in the Revised Corrective Action Plan-January 1997, dated 18 February 1997,the theoretical radius of influence of VW-1 is approximately 20 feet, and all of the known Iimpacted soil lies within 15 feet of VW-1, VW-1 is adequately screened and placed to Advanced GeoEnvironmental,Inc