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1 <br />' 06 October 2005 <br /> AGE-NC Project No 01-0827 <br />' Page 2 of 7 <br />' Environmental Health Department (EHD) by letter 11 July 2005 <br /> 2 1 OZONE SPARGE SYSTEM OPERATION <br /> The ozone-sparging(OS)system has operated at the site since July 2003,the system was monitored <br />' and serviced at regular Intervals throughout the quarter The OS system consists of an ozone <br /> generator,which produces ozone-rich air at a minimum of 10 standard cubic feet per minute(scfm) <br /> and a pressure of 20 pounds per square Inch This ozone-nch air is delivered to wells IAS-1 through <br />' IAS-3 and well OZ-1 via a subsurface network of 3/8-Inch polyethylene tubing <br /> Because the infected ozone will eventually break down to dissolved oxygen(DO), a DO meter was <br />' utilized at each monitoring well during the monitoring events to determine the effectiveness of ozone <br /> sparging During the third quarter sampling event, DO and/or oxidation/reduction potential (ORP) <br /> in ground water wells adjacent to the IAS wells were measured prior to purging the wells,during the <br />' well purging,and after the wells were purged Dissolved oxygen values from the three wells sampled <br /> (MW-6, VW-2D, and VW-5D) generally remained stable in the shallow wells during sampling, a <br /> decrease of DO was observed in the deep monitoring well MW-6 during the purging process <br />' Negative ORP values Increased in the monitoring wells near ozone infection wells during the purge <br /> process (Appendix B) <br />' Generally, sampling concentrations have declined in ground water wells since remediation system <br /> startup in July 2003 <br /> IOn 09 October 2001, three soil probe borings (P-1 through P-3) were advanced at the site to <br /> determine if soil has been impacted by methyl tertiary butyl ether(MTBE)potentially released from <br /> three former USTs The field work was conducted as outlined in the Phase II Site Assessment Work <br /> Plan dated 05 October 2001 <br /> 22 DRILLING ACTIVITIES <br /> Soil probe boring B 18 was advanced utilizing a van-mounted Geoprobe 5400 equipped with <br /> 1 125-inch diameter probe rods with an attached 2 15-Inch diameter soil sampler,using"direct push" <br /> technology <br /> 2 2 1 Soil and Ground Water Sample collection <br /> Discrete soil samples were collected at 5-foot intervals, beginning at 15 feet bsg, to the total depth <br /> • <br /> Advanced GeoEnvironmentai,Inc <br />