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0 <br /> CLEARWATER <br /> G R O U P <br /> Enalronm enf¢1 s'rices <br /> which takes into account the observed mass loss (contaminant decay rate), however, <br /> volatilization has been demonstrated to account of only 5% of benzene mass loss at a site with <br /> relatively favorable conditions for this process2 <br /> (Advection is responsible for the off-site migration of contaminants in concentrations below the <br /> detection limit To evaluate the extent of a plume attenuated through advection, the dissolved <br /> constituents are assumed to move at the same velocity as the groundwater (i a no retardation) <br /> Using the hydraulic conductivity of the water bearing zone, average hydraulic gradient, and <br /> average effective porosity, an approximate volume of hydrocarbons moving off site at <br /> concentrations at or below the detection limit can be estimated using Darcy's Law However, <br /> this process typically accounts for a relatively small percentage of apparent contaminant mass <br /> loss at most sites <br /> INJECTION WELL AND iSOC SYSTEM INSTALLATION <br /> During the current quarter, Clearwater oversaw installation of twelve remediation wells (IW-1 <br /> through IW-12) and an oxygen-infusion system ("iSOC") on the site The wells were developed <br /> via standard surging and pumping practices, and "baseline" biological monitoring field tests (i e , <br /> dissolved oxygen, redox potential, total iron, and ferrous iron) were performed on water samples <br /> collected from the wells following the well development procedures Additional dissolved <br /> oxygen measurements were made in the remediation wells at the time of the initial system <br /> inspection on September 24, 2004 Refer to Table 5 for the bio-monitoring data <br /> The iSOC oxygen infusers were installed in each of the remediation wells and are connected to a <br /> central regulated oxygen gas supply The iSOC units are suspended in each well, approximately <br /> 0 5 feet above the bottom, using plastic-lined cord, which is hung from the well plugs The <br /> oxygen supply is connected to the individual wells and infusers via underground plastic tubing <br /> Proceedings of the Conference on Petroleum Hydrocarbons and Organic Chemicals in Ground Water NGWA/API <br /> ZChiang,C Y et al (1989) Aerobic Biodegradation of Benzene,Toluene,and Xylene in a Sandy Aquifer-Data <br /> Analysis and Computer Modeling Groundwater Vol 27,No 6,p 823-834 <br /> ZB178C/3rdQtr 2004 Monitoring Rpt 8 October 8,2004 <br />