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CLEARWATER <br /> G R O U P <br /> Envrronmenta! Services <br /> well plugs The oxygen supply is connected to the individual wells and infusers via underground <br />' plastic tubing The oxygen feed pressures for the individual wells range between 3 5 psi and 5 0 <br /> psi Gas flow rate for each of the wells is 20 cc/min The wells were developed via standard <br />' surging and pumping practices, and "baseline" degradation parameters (i e , dissolved oxygen, <br /> redox potential, total iron, and ferrous iron) were measured in the field on water samples <br />' collected from the wells following the well development procedures Additional dissolved <br /> oxygen measurements were made in the remediation wells during the initial stage of system <br />' operation on September 24, 2004 Dissolved oxygen in the remediation wells were found <br /> increased from approximately 10 mg/L to concentrations on the order of 30 mg/L within the first <br /> two weeks of 1SOC system operation <br /> Dissolved Oxygen, ORP, Total and Ferrous Iron Field Testing <br /> Since the last sampling event on September 7, 2004, Clearwater measured various indirect <br /> geochemical indicators during the routine operations and maintenance of the iSOC oxygen <br /> infusion system The groundwater monitoring well and iSOC well data are included in Tables 4 <br /> to 5, respectively For October 7, 2004, dissolved oxygen concentrations ranged from 0 2 mglL <br /> in MW-1 to 3 5 mg/L in MW-5B In November 4, 2004, the DO ranged from 0 5 mg/L m MW-1 <br /> and MW-2 to 1 4 mg/L in MW-5B By December 7, 2004, the DO ranged from 0 1 mg/L in <br /> MW-3 to 2 7 mg/l in MW-5B It appears that monitoring well 5B has the highest levels of DO <br /> due to the proximity of the well to the 1SOC infection wells DO in the 1SOC wells reached a <br /> high of 39 7 mg/L to IW-7 on November 4, 2004 Slight decreases in DO in the iSOC wells in <br /> early October are associated with the depletion of the oxygen tanks or small leaks in the system <br /> New tanks were installed and new procedures were developed to better estimate oxygen tank <br /> tuse After installing new oxygen tanks, DO levels in the wells increased Dissolved oxygen <br /> levels in the iSOC treatment area are significant The observed DO concentration change over <br />' time for all the iSOC wells is presented in Figure 8 <br /> 4Q/04 Groundwater Monitoring Report 9 <br />