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

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Design Basis<br />

The pre-feasibility level design of <strong>the</strong> HTMF has been based <strong>on</strong> an approximate mine life of<br />

18 years. The initial annual throughput of tailings from <strong>the</strong> Hydrometallurgical Plant will start in<br />

year <strong>on</strong>e at 1,000 dry tpd and increase to 2,000 dry tpd by year four of operati<strong>on</strong>s.<br />

Tailings and Water Management<br />

All tailings solids and fluids as well as impacted water from <strong>the</strong> Process Plant will <str<strong>on</strong>g>report</str<strong>on</strong>g> to <strong>the</strong><br />

Tailings Basin. The HTMF design includes a Water Basin (Polishing P<strong>on</strong>d). Excess water from<br />

<strong>the</strong> Tailings Basin will be treated (if necessary) and discharged from <strong>the</strong> Polishing P<strong>on</strong>d through<br />

a lined discharge channel to <strong>the</strong> northwest corner of <strong>the</strong> existing tailings facility where it will be<br />

discharged to <strong>the</strong> natural drainage. Ultimately, all water from <strong>the</strong> HTMF will return to Great<br />

Slave Lake.<br />

Decant pipeworks have been included in <strong>the</strong> pre-feasibility design to transfer water from <strong>the</strong><br />

Tailings Basin supernatant p<strong>on</strong>d to <strong>the</strong> Polishing P<strong>on</strong>d, and to transfer water from <strong>the</strong> Polishing<br />

P<strong>on</strong>d to a lined discharge channel where it will be discharged to <strong>the</strong> natural drainage.<br />

Capacity and Freeboard Requirements<br />

The capacity of <strong>the</strong> HTMF is based <strong>on</strong> <strong>the</strong> topographic c<strong>on</strong>tours, <strong>the</strong> embankment c<strong>on</strong>figurati<strong>on</strong><br />

and <strong>the</strong> <strong>project</strong>ed process plant throughput rates. The HTMF capacity and freeboard have been<br />

designed based <strong>on</strong> <strong>the</strong> following key points:<br />

• Storage of 5.6 milli<strong>on</strong> m 3 of tailings at a settled dry density of 0.9 t/m 3<br />

• Storage of process water and accumulated ice<br />

• C<strong>on</strong>tainment of <strong>the</strong> 1 in 25 year 24-hour Envir<strong>on</strong>mental Design Storm (EDS) event (57<br />

mm)<br />

• Minimum freeboard of 2.0 m for routing of <strong>the</strong> Inflow Design Storm (IDS) and wave runup<br />

• Emergency Overflow Spillway to c<strong>on</strong>vey <strong>the</strong> IDS<br />

Phased c<strong>on</strong>structi<strong>on</strong> of <strong>the</strong> HTMF is proposed as follows:<br />

• Phase 1 (Pre-producti<strong>on</strong>) – This will include c<strong>on</strong>structi<strong>on</strong> of <strong>the</strong> Tailings Basin<br />

embankments to an intermediate level (3 m below <strong>the</strong> final design crest) to provide<br />

c<strong>on</strong>tainment of tailings solids and supernatant water for <strong>the</strong> first three years.<br />

Technical Report 43-101 – March 13, 2011 Page 18-48<br />

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

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