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' 07 Se . ptember 1999 AGE-NC Project No 95-0104 Page 7 of 8 Iof water of differential pressure (Table 4) • The induced vacuum stabilized at approximately 0 80 inches of water during the pilot test ' (Table 4) • PID field measurements were recorded at an average 322 25 parts per million (ppm) at the ' beginning portion of the July-August 1999 SVE/IAS pilot test and were recorded at an average 260 ppm near the end portion • A trend of declining PID field measurements is noticeable between the March-April PID ' field measurements and the July-August PID field measurements • TPH-g was detected in soil gas samples collected from VW-1 at concentrations ranging between 3,400 4g/l and 310 pg/l (Table 3) • BTEX compounds were detected in soil gas samples collected from VW-1 at concentrations up to 100 77 µg/1 Concentrations of benzene were detected in one soil gas sample collected from VW-I at a concentration of 16 ug/l (Table 3) • The volume of hydrocarbons extracted from VW-1 between 18 March 1999 and 16 April lie 1999 was calculated to be approximately 18 36 gallons of petroleum hydrocarbons (Appendix E) • Based on mass/volume calculations of total impacted petroleum hydrocarbon soil remaining at the site (Revised Coi rective Action Plan - January 1997, dated 18 February 1997), the apparent volume yielded approximately 300 gallons of impact remaining ii. the soil at the site AGE estimated that operation of the SVE/IAS system has removed 81 gallons of petroleum hydrocarbons in Quarterly Report-April 1999, dated 07 May 1999, factoring in the removal of the additional 18 36 gallons of petroleum hydrocarbons, then the SVE/IAS system has effectively removed approximately 99 36 gallons, or approximately 33 percent of petroleum hydrocarbons impacting soil at the site • As noted in the Revised Corr ective Action Plan -January 1997, dated 18 February 1997, the theoretical radius of influence of VW-I is approximately 20 feet, and all the known impacted I soil lies within 15 feet of VW-1, VW-1 is adequately screened and placed to address all known impacted soil 6.0 RECOMMENDATIONS Based upon the results of this investigation, AGE recommends • Continued operation of the SVE/IAS pilot test to provide immediate protection to nearby drinking water wells and to provide enough effective remediation such that additional active Adimrced GcoEmrronmcn1A1,inc