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17 June 2008 AGE-NC Project No. 99-0637 Page 5 of 7 On 31 August 2004,in-situ ozone injection began at the,site. Between 31 August 2004 and 31 May 2005 the generated ozone was piped into nine injection wells (OW-1 through OW-9) at a pressure of approximately 8 to 9 psi for an approximate duration of 2 hours. After completing the circuit of injection into the nine ozone wells, the ozone injection ceased for a mechanical hiatus of 2 hours prior to re-initiation. Between 31 May 2005 and 23 January 2006, ozone was injected into OW-1 through OW-9 at apressure of approximately 8 to 10 psi for an approximate duration of 1 hour,with a 1-hour mechanical hiatus prior to re-initiation. Between 23 January 2006 and 23 February 2007, ozone was injected into wells OW-2, OW-4, OW-5, and OW-6,at a pressure of approximately 9 to 12 psi for an approximate duration of 1 hour. Between 23 February 2007 and 26 June 2007, ozone was injected into wells OW-1 through OW-9, at a pressure of approximately 8 to 13 psi, for an approximate duration of 1 hour, with a 1-hour mechanical hiatus prior to re-initiation. The ozone injection system operation was terminated on 26 June 2007. The ozone injection system was operational for approximately 952 days between 31 August 2004 and 26 June 2007. Ozone remediation field data is presented in Tables 7 and 8. 5.0. ASSESSMENT OF HYDROCARBON-IMPACTED SOIL AND GROUND WATER Quarterly ground water monitoring has been ongoing at the site since April 2 00 1. TPH-g has only been detected three times since April 2001.TPH-g was detected at a concentration of 85 gg/1 in well MW4 in April 2002, and at concentrations of 110 µg11 and 300 µg/1 in well MW5 in January and April 2002, respectively. Their have been no other detections of TPH-g in any of the other ground water samples collected at the site since sampling beganAdditionally,TPH-d and BTEX(benzene, toluene, ethylbenzene, and total xylenes) compounds have not been detected above minimum laboratory reporting limits in any of the ground water samples collected from the site since sampling ; began. MTBE has been detected intermittently in samples collected from wells MW1 and MW2, at concentrations as high as 18 µg/l; however, MTBE has Inot been detected in the samples collected from wells MW1 and MW2 since February 2006. MTBE was detected each quarter between April 2001 and February 2005 in the samples collected from wells MW4 and MW5, at concentrations ranging from 76 gg/1 to 12,000 µg/l. Between May 2005 and November 2006 MTBE was detected intermittently in the samples collected from wells MW4 and MW5, at concentrations ranging from 4.1 µg/1 to 200 µg/l. MTBE has not been detected since INovember 2006 in wells MW4 and MWS. MTBE was detected each quarter between January 2002 and February 2005 in samples collected from wells MW6 and MW9,at concentrations ranging from 1.0�tg/1 to 160µg/l.MTBE has not been detected since February 2005 in wells MW6 and MW9. Graphs of MTBE concentrations over time in wells MW1, MW4, MW5, MW6, MW9, and MW10 are presented in Appendix B. ! Advanced GeoEnvironmental,Inc.