technical report on the nechalacho deposit, thor lake project ...

• Phase 2 (Ongoing) – The Phase 2 raise to the Tailings Basin should be scheduled for
year four onwards. The Phase 2 raise may be completed in three sequential one metre
raises to the embankment.
• Water Basin – Based on preliminary water balance modelling, construction of the water
basin is proposed to be completed during year one of operations.
Tailings Delivery and Distribution
Tailings slurry will be pumped from the proposed Hydrometallurgical Plant Site to the Tailings
Basin via insulated tailings delivery pipelines located along the existing access road alignment.
One pipeline will be installed for initial production while a second pipeline will be installed before
year four to account for the increased throughput.
Distribution pipelines will be placed around the east, south and west sides of the Tailings Basin.
Tailings deposition to the basin will consist of single end-of-pipe discharge from the tailings
deposition pipeline to reduce icing concerns during the winter months. During the entire
operations 100% of the tailings solids will be pumped to the Tailings Basin at a slurry
consistency of 20% solids by weight. Tailings discharge will be rotated between deposition
locations to develop a relatively flat tailings beach sloping towards the north and maintain a
supernatant pond in the northern portion of the Tailings Basin. A Polishing Pond receiving
treated flows will be constructed to the north side of the Tailings Basin if monitoring and
testwork indicate that it is required.
Basin and Embankment Construction
The Tailings Basin will be a square paddock with dimensions of approximately 1,200 m by 1,200
m. The Polishing Pond will be rectangular with dimensions of approximately 1,200 m by 300 m.
Both basins will be situated on the existing historic tailings surface.
It is assumed that historic borrow areas in close proximity to the Hydrometallurgical Site remain
from previous Pine Point Mine Operations (EBA, 2009) could be reopened to supply granular
material for the construction of the embankments if required. The existing tailings material is
expected to be relatively well drained near surface.
In order to keep the Hydrometallurgical tailings and process fluids separate from the historic
tailings, it is proposed that the basin will be lined with a geomembrane. The geomembrane will
be laid on a prepared and graded subgrade following excavation of sand and gravel cover and
historic tailings for berm construction. An underdrain system consisting of a series of perforated
CPT pipes surrounded in drainage gravel will be placed under the geomembrane to monitor the
performance of the lined basin. The geomembrane will be covered on the upstream slopes of
the containment berm with a cover layer of historic tailings followed by riprap (separated with a
Technical Report 43-101 – March 13, 2011 Page 18-49
Prepared by Avalon Rare Metals Inc.