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

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thus a specific gravity for <strong>the</strong> tailings solids high in gypsum c<strong>on</strong>tent has been estimated<br />

at 2.40.<br />

• Dry Density: Given a final solids c<strong>on</strong>tent or pulp density of approximately 65% by weight<br />

(and a void ratio of 1.3 <strong>the</strong> calculated final average settled dry density for <strong>the</strong> tailings in<br />

<strong>the</strong> TMF is 1.05 t/m 3 . A slightly lower or c<strong>on</strong>servative density value of 0.9 t/m 3 has been<br />

selected for <strong>the</strong> pre-feasibility design.<br />

It is understood that tailings test work will be completed in later stages of study to c<strong>on</strong>firm <strong>the</strong><br />

tailings parameters.<br />

Currently no geochemical testing has been completed <strong>on</strong> tailings samples. It is understood that<br />

testwork will be completed in later stages of study to c<strong>on</strong>firm <strong>the</strong> tailings geochemical<br />

parameters.<br />

Tailings Management Facility Design<br />

The design basis and criteria for <strong>the</strong> HTMF are based <strong>on</strong> Canadian standards for <strong>the</strong> design of<br />

dams. In particular, all aspects of <strong>the</strong> design of <strong>the</strong> HTMF have been completed in compliance<br />

with <strong>the</strong> following documents:<br />

• Canadian Dam Associati<strong>on</strong> (CDA) Dam Safety Guidelines (CDA 2007)<br />

• The Mining Associati<strong>on</strong> of Canada (MAC) Guide to <strong>the</strong> Management of Tailings Facilities<br />

(MAC 1998)<br />

The principle objective of <strong>the</strong> HTMF design is to ensure protecti<strong>on</strong> of <strong>the</strong> envir<strong>on</strong>ment during<br />

operati<strong>on</strong>s and in <strong>the</strong> l<strong>on</strong>g-term (after closure), and achieve effective reclamati<strong>on</strong> at mine<br />

closure. The pre-feasibility design of <strong>the</strong> HTMF has taken into account <strong>the</strong> following<br />

requirements:<br />

• Permanent, secure and total c<strong>on</strong>finement of all tailings solids within an engineered<br />

facility<br />

• C<strong>on</strong>trol, collecti<strong>on</strong> and removal of free draining liquids from <strong>the</strong> tailings during operati<strong>on</strong>s<br />

• The inclusi<strong>on</strong> of m<strong>on</strong>itoring features for all aspects of <strong>the</strong> facility to ensure performance<br />

goals are achieved and design criteria and assumpti<strong>on</strong>s are met<br />

The c<strong>on</strong>structi<strong>on</strong> will be scheduled to ensure that <strong>the</strong>re is always sufficient storage capacity<br />

available in <strong>the</strong> facility to avoid overtopping. The embankment raising schedule will provide<br />

sufficient freeboard to safely accommodate <strong>the</strong> supernatant p<strong>on</strong>d and Envir<strong>on</strong>mental Design<br />

Storm event, combined with wave run-up. An emergency overflow spillway is included to pass<br />

<strong>the</strong> Inflow Design Flood event.<br />

Technical Report 43-101 – March 13, 2011 Page 18-47<br />

Prepared by Aval<strong>on</strong> Rare Metals Inc.

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