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E 05 May 1997 AGE-NC Project No 95-0112 Page 5 of 14 1 TPH-g was detected in the vapor sample collected in February 1997 at a concentration of 560 j.cg/l Organic vapor measurements ranged from 76 ppmv to 106 ppmv during the first quarter of 1997, a decrease from previous quarters Field data is included on Table 2 Analytical results of all vapor ' samples are summarized in Table 3 The laboratory reports(MAI, sample I D No 73903)and chain- of-custody form for the February 1997 sample are included in Appendix C Analytical results of soil vapor samples were used to calculate the mass of hydrocarbons removed and determine efficiency of the SVE unit The extracted hydrocarbons during each time frame are sunnnarized on Table 4 Mass calculations for the first quarter of 1997 are discussed in Section 5 2 Calculation methods are included in Appendix D ' 32 IN-SITU AIR SPARGING From 17 to 19 May 1995, borings SWA and SW-2 were advanced at the site to depths of 73 5 feet and 75 feet, respectively, and completed as in-situ air sparging wells with five feet of slotted PVC casing Hydrocarbons were detected in soil samples collected at a depth of 50 feet bsg in boring SW- ' • 1 and at depths of 40 and 50 feet bsg in boring SW-2 Analytical results are summarized on Table 1 Boring logs are included in Appendix A ' The IAS system, installed concuriently with the SVE system, utilizes a compressor-driven EnviroSparge system and provides air to the subsurface through two IAS infection points Air sparging was initiated on 16 August 1995 The Envirosparge system delivered between 5 and 7 cfin ' of air to sparging wells SW-1 and SW-2 during the daytime on one hour cycles The sparging unit was not operated during the night due to noise concerns and the proximity of residences to the site Furthennore, the sparging unit was not operational between 31 October 1995 and 02 Pebruary 1996 ' and again for most of June 1996 due to mechanical difficulties Following the non-detection of hydrocarbons in the January 1997 ground water monitoring event, sparging was discontinued on 07 ' Febi uary 1997 ' 33 REMEDIATION PROGRESS SOIL SAMPLING Soil samples were collected from the area of remediation in March 1996, July 1996 and February ' - 1997 Sampling performed during March and July 1996 were discussed in Quai tel ly Reports for April and September 1996 Confirmation sdmpling performed in February 1997 is discussed below 1 i i