Pulacayo Project Feasibility Study - Apogee Silver

Pulacayo 1 000 t/d Phase I Feasibility Study - NI 43-101 Technical Report
090644-3-0000-20-IFI-100
owns. Once all the broken ore has been removed from the stope, it will be filled with
cemented backfill, as recommended in the Backfill Section of this report.
Historic mining has left voids throughout the planned operation. The voids that have been
identified are flagged in the block model and tend to be located along the high grade portions
of the ore body. This risk of encountering them will be mitigated by implementing an
exploratory drilling program (cover drilling) ahead of production. This will allow for evaluation
of ground conditions and the quality of the deposit prior to mining.
The information obtained from this exercise will: verify and identify the location and width of
the previously mined areas (voids); determine if the voids are filled with old waste material;
allow an economic estimation of the mineralization in each block to ensure that the area is
profitable to mine; allow planning for the extraction of each stoping block to be made based
on ground conditions; allow planning to prevent ore losses by backfilling voids that are
located adjacent to stoping blocks; and put in suitable measures to minimize dilution and
ensure the safety of people in the case where stoping blocks are located next to voids that
are filled.
There are several possibilities of void condition that could be encountered:
They could be completely empty, or partially filled with material that has caved
from the sidewalls of the stope. If such a void is encountered, it would need to be
filled with cemented backfill in order to safely mine adjacent areas.
They could be filled with water and mud. In such a case, it is almost certain that
the mud would have settled and solidified at the bottom of the void. In such a
case, the water would need to be drained through cover drilling holes. Once this
has been achieved, the void would need to be filled with cemented backfill as
recommended in the Backfill Section of this report.
If the void is filled with loose material, it will not be safe to remove the waste due
to the risk of losing equipment. In such a case, a pillar would need to be left
around the void before mining adjacent areas.
A potential risk to the project is a deficit in backfill material in the early years on the mine. The
problem will worsen if a large number of unplanned and unfilled voids are encountered. To
reduce the risk of having a deficit of fill material, the mine will have to use development waste
and/or waste rock from a borrow pit on surface. The waste rock will have to be combined with
cement as recommended in the Backfill Section of this report.
16.2.3 Mine Access
The shrinkage stopes will be accessed via the San Leon tunnel, which is an existing haulage
that was holed through the mountain during historic mining. The tunnel has a width and
height of 2.5 m and a total length of about 1.57 km. The long hole stopes will be accessed via
a 4 m (h) x 4 m (w) decline ramp system that will be developed from surface to allow rock to
be trucked out of the mine. The ramp system will be developed at an inclination of 8 degrees
from the horizontal and it will comprise the east decline ramp and the west spiral ramp.
Figure 16.3 shows the decline ramp system and Figure 16.4 shows the designed mine
layout.
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