United Taconite operations consist of an open pit truck and shovel mine where two stages of crushing occur before the ore is transported by rail, operated by CN, to the plant site.
The Thunderbird Mine North (TBN) and Thunderbird Mine South (TBS) are mined using conventional surface mining methods. The surface operations include:
• Overburden (glacial till) removal.
• Drilling and blasting (excluding overburden).
• Loading and haulage.
• Crushing and rail loading.
The Mineral Reserve is based on the ongoing annual average crude ore production of approximately 15.4 MLT per year (MLT/y) from TBN and TBS, producing an average of 5.1 MLT/y of wet pellets for domestic consumption.
The current LOM plan has mining for 51 years and mines the known Mineral Reserve. The average strip ratio is 1.1 waste units to 1 crude ore unit (1.1 strip ratio).
Within TBN, a previously mined out and backfilled area known as the Auburn pit will require a modified wall design to incorporate a wall containing both unconsolidated fill and in situ rock. The walls of the Auburn pit will align to an overall wall angle of 31°. In the unconsolidated fill, this is accomplished by the 36° angle of repose and 10 ft CB every bench. In the in situ rock, this is accomplished by the 70° BFA and 45 ft CB every bench. These configurations will allow for a uniform toe across the bench.
The final TBN pit is approximately 4.1 mi long along strike, ........
