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' H. BACKGROUND <br /> ' Mine Plan Amendments Nos. 3 and 4 revised the approach to slope design at the Morrison <br /> PP P g <br /> Quarry with the implementation of the Observational Method throughout the quarry. The <br /> ' significant changes presented in these Amendments were a reconfiguration of the East <br /> Highwall of the Central Quarry to address slope instabilities in that area and the provisional <br /> change in slope inclinations elsewhere to as steep as 0.5H:1V based on evaluations of <br /> ' preliminary slopes established at 1H:1V. As a condition of the Amendments, the steeper <br /> slopes and revised configuration could be implemented only in accordance with specific, pre- <br /> determined steps outlined in the Observational Method. Conditional approval of the Amend- <br /> ments required annual reporting of geotechnical data, slope stability evaluations, and current <br /> mine conditions in areas where steeper slopes were utilized,.or where unusual conditions were <br /> encountered. <br /> '• The Observational Method as described in Mine Plan Amendments Nos. 3 and 4, is a step- <br /> wise approach to slope design by which new information is regularly used to upgrade <br /> previous analyses. This method was utilized as a practical approach to designing slopes in a <br /> rock mass with variable conditions and which is in some areas poorly exposed and difficult to <br /> characterize. A key factor of the method is that baseline conditions are established during <br /> ' initial evaluations; observed conditions are then compared with the baseline. Annual <br /> geotechnical reports are presented as a required condition of permit approval and to provide <br /> the opportunity for regular regulatory review of geotechnical aspects of mining activities. <br /> ' According to permit conditions, the Observational Method is applicable to any slope in the <br /> quarry, except the East Highwall of the Central Quarry, which is steeper than an 80 ft <br /> 1 highwall and 80 ft bench configuration. The method also applies to the East Highwall if the <br /> slope is altered from the previously approved slope.configuration of 40 ft highwalls and 50 to <br /> 60 ft benches shown in the approved Amendments. In addition, CAMAS is applying the <br /> ' method to the approved slope configuration for the East Highwall to verify baseline design <br /> assumptions. <br /> ' 2 G:\PROJECTS\20200\002\96ANNRPT.WPD <br />