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
(up to 70% by total weight), and the TSF in located in an arid climate (very low precipitation and
high evaporation, with a very high ratio of evaporation to precipitation); thus, the amount of water
available is limited. As such, it was determined that an engineered liner system such as a
geomembrane is not required for the TSF impoundment and that natural, geologic containment is
sufficient to properly protect the environment, both to Bolivian and International standards.
However, an additional barrier will be provided; cement - treated tailings (3%) will be placed as a
continuous cover over the entire base of the TSF area. This will perform better than the average
compacted clay barrier and when combined with the natural containment should provide excellent
containment.
The emergency pond, located immediately below the toe of the lowest TSF dike, will be lined with
1.5 mm thick high density polyethylene (HDPE) over and in direct contact with at geosynthetic
clay liner (GCL). The pond is being lined because it can develop important hydraulic heads,
which will be focused just below the toe of Dike 1, and therefore a very high level of containment
is warranted.
18.9.8 Starter Dikes & Dikes Raises
The TSF includes four separate dikes, each supporting the toe of the corresponding deposit.
These are located sequentially upstream from one another, within the same small valley and
numbered Dike 1 to Dike 4, from the lowest elevation working up gradient. The starter dikes
range in nominal height from 6 to 8 meters. The reason for four dikes are:
1) To allow initial filling of the valley floor,
2) To allow placement of cement-treated tailings (3%) along the entire bottom area, to act as a
seepage barrier,
3) To provide sufficient working area for the placement of cement-treated tailings to be used in
the construction of the subsequent raises to each dike,
4) To create a system of paddocks which will allow seasonal drying of the tailings, by moving
the discharge from one pond to the other at intervals to be determine based on the season
and nature of the produced tailings, and
5) To provide sufficient storage capacity in the early years, while the storage is principally in
the bottom of the valley (that is, very little capacity per meter of elevation gain).
As the TSF is filled with tailings the four separate impoundments will merge into one larger
impoundment, as depicted in Figure 18.5.
All four of the starter dikes will be constructed as part of the initial facility, and the four
impoundments filled with cement-treated tailings during the first 12 months of operation. Starter
Dikes 1 & 2 will be constructed with high quality, compacted structural fill; dikes 3 & 4 will be
constructed with random fill since they will be quickly supported by the downstream tailings and
do not form part of any permanent slope. Each dike will be raised about 4 meters at a time using
compacted, cement-treated tailings (3% Portland cement by dry weight). The volume created
between Dikes 1 & 2 (that is, the impoundment behind Dike 1) will be filled with non-compacted
cement-treated tailings for its entire depth (to the ultimate crest). The other 3 impoundments will
be filled with non-cement-treated tailings. As the crest elevation increases and the four separate
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