GEOLOGIC CONSIDERATIONS FOR UNDERHAND CLOSED BENCHING(UCB) AT THE LUCKY FRIDAY MINE

The Lucky Friday Mine, located in Mullan Idaho, is experiencing increased productivity despite challenges posed by working at greater depths. This is a direct result of the implementation of a new mining method called Underhand Closed Benching(UCB). This bulk mining method for a narrow-vein ore body is reliant on a closely spaced pre-production drilling program to delineate the vein position ahead of the mining front. This requires a three-fold increase in core hole density from the historic norms. This data increase allows for improvements to geologic, resource, and vein modeling. By refining orebody geometry and vein composition the optimal mining corridor can be selected.

Planning for the UCB method incorporates the work of Technical Services and Mine Operations staff leveraging a wide range of disciplines. This discussion will cover changes in ore control methodology, better controlled site seismicity, and increased mine productivity.