REP05386 - Laserfiche WebLink

Home Browse Search

II. BACKGROiJND 2.01 Mine Plan Amendments and Technical Revisions Mine Plan Amendments Nos. 3 and 4 revised the approach to slope design at the Morrison Quarry with the implementation of the Observational Method throughout the quarry. These Amendments carried over in Amendment No. 5. The significant changes presented in these Amendments were a reconfiguration of the east side of the Central Quarry to address slope instabilities in that area and the provisional change in slope inclinations elsewhere to as steep as O.SH:1 V based on evaluations of preliminary slopes established at 1H:1 V. As a condition of the Amendments, the steeper slopes and revised configuration could be implemented only in accordance with specific, predetermined steps outlined in the Observational Method. Conditional approval of the Amendments required annual reporting of geotechnical data, slope stability evaluations, and current mine conditions in areas where steeper slopes were utilized, or where unusual conditions were encountered. Technical Revision No. 3 modified the mine plan of the Central Quarry by allowing mining from Bench A (El. 6453 feet) down to Bench E (El. 6253) to be excavated with 30 ft benches and 50 ft highwalls. 2.02 Observational Method The Observational Method as described in Mine Plan Amendments Nos. 3 and 4, is a step-wise approach to slope design by which new information is regularly used to upgrade previous analyses. This method was utilized as a practical approach to designing slopes in a rock mass with variable conditions, in which some areas are poorly exposed and difficult to characterize. This method establishes baseline conditions during initial evaluations. Observed initial conditions are then compared with the baseline for analyses. As a required condition of permit approval, annual geotechnical reports are presented to provide the opportunity for periodic regulatory review of geotechnical conditions relating to mining activities. The Observational Method is applicable to any slope in the quarry, except the west side of the Central Quarry, which is steeper than 1 H:1 V.