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i 07 November 2004 AGE-NC Project No 96-0232 Page 6of11 IOS consists of two, in-situ phases of treatment During the first phase of IOS treatment, ozone is generated and immediately pumped into groundwater through traditional air sparge wells,the ozone exits the air sparge wells through a stone of fine porosity,creating very small bubbles(microbubbles) that rise slowly through the water The slower the bubbles rise through the water the greater the amount of ozone transferred to the water As the ozone passes through the water, the third unstable atom detaches, and chemically reacts with impurities(i e MTBE) in the water, eventaully breaking the compound down into carbon dioxide and water During the second phase of IOS treatment, subsurface unreacted ozone will chemically degrade to dissolved oxygen,which will enhance the natural biodegradation process of residual contaminants Additional ozone infection literature is contained in Appendix C 4 2 2 Basic System Design Ozone infection wells are typically completed much like air sparge wells, the ozone infection wells are screened within the saturated zone and typically utilize a manufacturer-assembled macroporous • stone(sparge point)at the bottom of the well,the bottom sparge point is typically attached to the top of the well-head utilizing blank, Schedule 40 PVC well casing The ozone infection well-head is connected to an ozone generator usually with chemical resistant tubing An ozone generator is utilized to produce either gaseous or liquid ozone which will be infected into the subsurface via the above referenced microsparge points, producing `microbubbles' The `microbubbles' (approximately 50 micrometers) will be forced out into the surrounding saturated soil and react with the target analytes, producing carbon dioxide and water The frequency and duration of ozone infection periods will be be regulated at the ozone generator electrical control box Initially, operation of the ozone infection system will be based on the manufacturer's recommendations However, infection rates, frequency and duration are typically adjusted to compensate for site specific conditions The radius of influence of an ozone sparging well is dependent on site lithology and the depth of the sparging well Sandy soil types tend to produce a larger radius of influence, clayey soil types tend to produce a more limited radius of influence 4 2 3 Monitoring Activities Initial results and progress of IOS treatment should be monitored utilizing field measurements in nearby monitoring wells for dissolved oxygen (DO) and oxidation-reduction potential (ORP), and Advanced GeoEnvj ron mental,Inc