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II. BACKGROUND <br />2.01 Mine Plan Amendments and Technical Revisions <br />Mine Plan Amendments Nos. 3 and 4 revised the approach to slope design at the Morrison <br />Quarry with the implementation of the Observational Method throughout the quarry. These <br />Amendments carried over in Amendment No. 5. The significant changes presented in these <br />Amendments were a reconfiguration of the east side of the Central Quarry to address slope <br />instabilities in that area and the provisional change in slope inclinations elsewhere to as steep <br />as O.SH:1V based on evaluations of preliminary slopes established at 1H:1V. As a condition <br />of the Amendments, the steeper slopes and revised configuration could be implemented only <br />in accordance with specific, predetermined steps outlined in the Observational Method. <br />Conditional approval of the Amendments required annual reporting of geotechnical data, <br />slope stability evaluations, and current mine conditions in areas where steeper slopes were <br />utilized, or where unusual conditions were encountered. <br />Technical Revision No. 3 modified the mine plan of,the Central Quarry_by allowing mining <br />from Bench A (el. 6453 feet) down to$ehch E (el. 6253) to be excavated with 30 ft benches <br />and 50 fr highwalls. <br />2.02 Observational Method <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, in which some areas aze poorly exposed and difficult to <br />characterize. This method establishes baseline conditions during initial evaluations. <br />Observed initial conditions are then compared with the baseline for analyses. As a required <br />condition of permit approval, annual geotechnical reports are presented to provide the <br />opportunity for periodic regulatory review of geotechnical conditions relating to mining <br />activities. <br />The Observational Method is applicable to any slope in the quarry, except the west side of the <br />Central Quarry, which is steeper than IH:1V. <br />G:\PROlECTS\20200 Morrison Quarry\008\2002\2002 geotechnical adder~dum.da <br />