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Storage.
Several stockpile areas will be installed. The Run-of-Mine (ROM) stockpile will be
located upstream of the PUG Feed Hopper to accommodate mine schedule and ore type to be
crushed. The crushed ore will be stockpiled by grade (high grade and low grade) upstream of
the PUG Facility to accommodate unplanned downtime. The Low Grade Ore Stockpile will be
used for storage of the stockwork and low grade ore, and will have a capacity of 5.8 million tons
of stockwork and low grade ore. The environmental behavior of the low grade ore, which may
be stored on-site for longer periods of time, will be assessed as part of the on-going
geochemical characterization work.
Controls.
The PUG Plant will be semi-automated. All equipment and stream flows will be
automated and primarily controlled from the control room. Local controls will be installed where
required. Laboratory technicians will manually perform chemical analyses such as rare earth
product element distribution and tailings elemental distribution. Measurements such as pH will
be automated, but a constant manual validation of the instruments will be required to ensure the
proper processing of the rare earths. A data historian system connected to the distributed
control system will enable the collection of data centrally from across the plant.
Process.
The PUG process is designed to produce a rare earth oxide pre-concentrate by a
sequence of crushing, washing, screening, solid/liquid separation, magnetic separation, gravity
classification, and dewatering. PUG pre-concentrate will be sent to the Hydromet Plant for
further processing.
The run of mine ore from Bull Hill and Whitetail resource areas will be stockpiled by grade and
mineralization (high grade and OxCa) prior to the crushing circuit. The stockpiles will be
individually reclaimed to feed the plant through the dump hopper. The feed will be transferred
from the hopper to the open circuit jaw crusher by a vibrating grizzly feeder. An electromagnet
will be installed at the end of the crusher discharge conveyor to remove tramp metal, which may
damage downstream equipment. The crusher discharge will be screened on a vibrating screen.
The oversize material, which contains a low TREO grade, will be transferred to the Low Grade
Ore Stockpile or the Waste Rock Facility. The screen undersize will be sent to the crushed ore
stockpile. The stockpiles will have a capacity of at least 24 hours of PUG operation. Reject rock
from the grizzly screen will be trucked to the Waste Rock Facility. Moisture content of reject
material destined for the Waste Rock Facility will range between 3 and 10 percent. Any water
from the Waste Rock Facility will be collected in the underdrain for storage in the sediment
trapping pond as shown on Figure 1 (Appendix D).
The high grade crushed ore will be reclaimed from the stockpile by two belt feeders and
conveyed to the secondary crusher, operating in open circuit. Depending on the ore type, the
screen undersize will either feed directly to the thickener or to magnetic and/or gravity
separators to remove gangue minerals. The screen oversize will also feed to gravity and/or
magnetic separators to remove gangue minerals. The cleaned products are fed directly to the
thickener while all gangue minerals are filtered and disposed in the Waste Rock Facility.
Recycled water is returned to the process.
The PUG pre-concentrate thickener is used to recover water and increase slurry density to 50
percent w/w (weight basis) before filtering. The underflow will be pumped to the press filters to
further decrease the pre-concentrate moisture to 20 percent w/w. The pre-concentrate will be
hauled to the Hydromet Plant by truck.
4.5.4.4 Storm Water Control
A Technical Memorandum which conceptually describes hydrology and hydraulics of the Mine
Area is provided in Appendix D. Figure 1 in Appendix D shows the Watershed Management
Plan for the Bull Hill Mine with typical surface water channel cross sections shown in Figure 4.5-
