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Antonia Vorster -3- 16 February 2011 <br /> The ozone sparge system was discontinued on 15 August 2006 due to a very low rate <br /> of destruction of contaminant mass and formation of unwanted compounds including <br /> bromodichloromethane and dibromochloromethane in ground water due to naturally <br /> occurring bromine reacting with ozone. <br /> Extent defined: Yes <br /> Threat to Groundwater: Site remedial activities have removed the threat to groundwater <br /> quality. <br /> Threat to Human Health: <br /> • Vapor Intrusion Hazard: Soil vapor sampling near the source area and Johnson- <br /> Ettinger vapor intrusion model indicate there are no pollutants that pose a vapor <br /> intrusion hazard. <br /> • Dermal Contact Hazard: There is not a dermal contact hazard at the site. <br /> Summary: <br /> Based on these evaluations we concur with the determination by Georgia-Pacific that the site <br /> does not have residual concentrations of contaminants that pose either a threat to water <br /> quality, human health, or the biota. <br /> • The source of contaminants of concern has been removed. <br /> • Soil and ground water contaminants at the site have been adequately characterized. <br /> Dissolved phase contaminants have diminished to safe levels, continue to diminish, and <br /> are not migrating. <br /> • No water wells, drinking-water aquifers, or other sensitive receptors are likely to be <br /> impacted. <br /> • The site presents no significant risk to human health or the environment. <br /> • A Public Notice fact sheet was circulated to local residents, City of Tracy officials and <br /> San Joaquin County officials. No comments were received. <br /> Figures <br /> California Environmental Protection Agency <br /> 2d Recycled Paper <br />