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Cripple Creek & Victor Phone (719) 689-2977 <br />Gold Mining Company Fax (719) 689-3254 <br />PO Box 191 <br />100 N Yd <br />/ANGLOGOLD ASNANTI Victor, CO 80860-0191 <br />ANGLOGOLD ASHANTI (COLORADO) CORP. <br />week during the injection program. If, during the injection program, the survey data indicates a total vertical <br />displacement rate of 1-inch per week or greater, then injection activities should be terminated and the injection <br />pressures revised. <br />In accordance to the AMEC letter dated 17 December, 2009, the Factor of Safety (FoS) for the Valley Leach <br />Facility (VLF) will remain at or greater than the minimum acceptable value of 1.5 as long as the injection <br />guidelines presented in the letter are followed. The injection guidelines are: <br />1. The injection wells should be located a minimum of 20 feet from the crest of any ore benches. Only wells that <br />will have deep (+100 feet) injection depths can be located closer than 20 feet from the bench crest; <br />2. Injection pressures in the upper 70 feet should not exceed % of the overburden pressure. Higher injection <br />pressures can be used for depths greater than 70 feet, but should not exceed the overburden pressure; and <br />3. Injection pressures should always be closely monitored and controlled to avoid any local instabilities. <br />3. Electrical Resistivity Characterization and Monitoring <br />Figures 1 and 2 show the positions of the nine HJ wells along the westernmost edge of the 9925' elevation of <br />Phase 2. Also shown are the positions of seven additional bore holes distributed over the HJ target area. As part <br />of CC&V's commitment to monitoring the HJ project and ensuring the safe stable operation of the VLF, these <br />holes are will be used to install a network of subsurface electrodes that will be used to monitor solution profiles <br />during injection events using electrical resistivity techniques. <br />HydroGeophysics Inc. (HGI), a geophysical firm specializing in resistivity monitoring, has been contracted to work <br />in concert with MRS during the injections. As the saturation of the pore space is increased during the injection, <br />the electrical resistivity of the heap decreases. Hence, by monitoring the resistivity between various <br />combinations of electrodes it will be possible for HGI to determine the preferred flow directions at each <br />injection depth as well the proximity of these flow paths to the surface of the VLF. <br />HGI has previously demonstrated the benefits of electrical resistivity characterization and monitoring in support <br />of the HJ process at Newmont, (Rucker, 2009a; Rucker et al., 2009b) establishing very close ties to Metal <br />Recovery Solutions (MRS) that have continued through the commercialization of HJ. HGI will use the subsurface <br />electrodes in conjunction with a network of surface electrodes deployed on the surrounding areas to track the <br />migration of fluid during each injection event. Since the data is gathered in real time, if HGI determines that <br />solution migration paths are not as desired it will be possible to relay this to MRS operators so that immediate <br />action can be taken. <br />As shown in Figures 1 and 2 the network of subsurface electrodes installed in the monitoring bore holes will <br />surround injection wells labeled H1-2, HJ-3, and HJ-4. The numeric designation in the well ID denotes the <br />position of the well in the target area rather than the treatment order - the aforementioned will actually be <br />treated first. Data generated from injections in these wells will provide an avenue to reconcile physical <br />operations with analytical relationships and establish a robust baseline to ensure complete process control <br />during stimulation of subsequent wells.