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ZZ <br /> �X> �c3 0 — <br /> CLEARWATER <br />• G R O U P I N C <br /> Environmental Services <br /> Dissolved Oxygen, ORP, Total and Ferrous Iron Field Testing <br /> Clearwater measured various indirect geochemical indicators during the routine O&M of the <br /> iSOC oxygen infusion system Durmg the January and February O&M events only the 1SOCTM <br /> system wells were monitored for levels of dissolved oxygen (DO), oxidation reduction potential <br /> (ORP), ferrous iron We 2+) and total iron (Fe) The groundwater monitoring program was <br /> adjusted during the fourth quarter of 2004 to include the quarterly collection of the geochemical <br /> data from MW-1 through MW-8 The geochemical data for all of the wells are summarized in <br /> Table 3 Monthly system and geochemical data are recorded on iSOCTM System Field <br /> Monitoring forms which are included (Attachment E). <br /> The average DO level observed in the iSOCTM wells during the two operations and maintenance <br /> (O&M) visits conducted on January 10`h and February 7, 2005, and during the first quarter <br /> groundwater monitoring and iSOCTM O&M event were 47 8 mg/L, 0 28 mg/L and 27 92 mg/L <br /> respectively The DO levels increased throughout the entire monitoring well network this quarter <br />. (Figure 10) The range of DO levels observed for the twelve iSOCTM system wells during the <br /> January O&M event have a similar distribution as the DO levels observed during the March <br /> O&M event (Figure 11) Though there is a fluctuation in DO levels from month to month, the <br /> changes in DO levels are within the normal range of natural variability The dissolved oxygen <br /> levels in the iSOCTM treatment area observed during the quarterly monitoring event are <br /> illustrated in the iso-contour map included (Figure 12) <br /> Oxidation-reduction potential (ORP) is a measure of the REDOX potential recorded in millivolts <br /> (mV) It measures the ability of hydrogen, and a large variety of organic and inorganic <br /> chemicals, to donate electrons It also measures other elements or compounds which are <br /> accepting electrons such as oxygen or terminal acceptors such as, nitrate, nitrite, sulfate, carbon <br /> dioxide, iron (III), manganese (IV) (Suthersan, 2002) The more negative the ORP value, the <br /> lower the DO levels indicating microaerophilic conditions Highly positive ORP values (+100 to <br /> +200 mV) are indicative of aerobic conditions. <br /> ZB178I 6 of 10 May 2006 <br />