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TERRAMIN AUSTRALIA Limited

TERRAMIN AUSTRALIA Limited. Angas Zinc Project. Tailings Storage Facility Overview. Long presentation – may of necessity be a bit technical Why we need a Tailings Storage Facility (TSF) The Design Process Requirements Guidelines Testwork Tailings Handling method Water management

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TERRAMIN AUSTRALIA Limited

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  1. TERRAMIN AUSTRALIA Limited Angas Zinc Project

  2. Tailings Storage Facility Overview • Long presentation – may of necessity be a bit technical • Why we need a Tailings Storage Facility (TSF) • The Design Process • Requirements • Guidelines • Testwork • Tailings Handling method • Water management • Design selection • Closure • Location – Flood Plain

  3. Angas Zinc Project: Tailings storage • Mining & processing ore creates non-saleable by-products • “Tailings”- fine sand of the waste rock • Often combined with water • Stored close to site of processing • About 40% goes back underground as “cemented backfill” • However, need to design for “worst case”

  4. THE TSF DESIGN PROCESS

  5. TSF Guidelines • ANCOLD Guidelines used, no current Guidelines in SA. ANCOLD draws substantially from WA “Guidelines on the Safe Design & Operation Standards for Tailings Storage” but goes further in the area of dam design • PIRSA -EPA “Guidelines for the Management of Tailings” at the proposed Angas Zinc Project, Strathalbyn, SA

  6. TSF - design • Australian Tailings Consultants • TSF objective: • No contamination of natural water drainage systems, ground water, land and soils either on or off site during operation and indefinitely post closure caused by mine ore or waste material.

  7. TSF -The Testwork • Test pits • In-situ permeability testing. • Lab. testing of soils. • Geochemical & geotechnical testing of simulated tailings. • Impoundment layout & bank design - modeling. • Seepage analyses, assessment of groundwater impact & design of proposed mitigating measures. • Location, design & installation of groundwater monitoring bores. • Water mgt. both process & rainfall. • Proposals for TSF closure & rehabilitation***

  8. TSF - Tailings Handling Options Two Options: • Un-thickened tailings • Majority of TSF in Australia • Thickened tailings • Few places in the World using very high density tails deposition – used when water is scarce, ease of closure***

  9. Advantages of thickened tailings • Low water demand • No water pond to attract birds • Tailing surface crust stops dusting • Beach area dries rapidly allows early access. • Allows for progressive closure

  10. TSF - Thickened tailings • Wheaton River’s, Peak Mine - Cobar

  11. Thickened tailings • Wheaton River’s, Peak Mine - Cobar

  12. Water management

  13. TSF - Water Management

  14. TSF - Water management: Water from TSF to Plant

  15. TSF - Water management Summary • Divert all surface flows from surrounding area around the TSF • Dam design allows for the catchment of a 1:100yr 5 day storm event • No water pond on TSF

  16. The TSF Design Selection

  17. TSF Design

  18. Risk Analysis

  19. TSF-Risk Analysis

  20. TSF location & detail

  21. TSF construction: base layer

  22. TSF options- detail • Proposed Design Option: Decant well

  23. TSF Design Design Summary: • HDPE liner (base and cap) • Thickened tailings • Liner ensures TSF design requirement • Placement: beyond 1:100 ARI flood level • Footprint:15ha • World’s Best Practice

  24. TSF Closure

  25. TSF Closure: capping layers

  26. TSF Closure

  27. TSF Closure • Closure is important aspect for the longer term environmental considerations • Impervious cover liner • Earthworks – reshaping, topsoil • Rapid revegetation • Risk based closure plan used

  28. Flood Plain Modelling

  29. TSF placement to meet outcomes • 100m from 1:100 ARI flood plain • Flood modelling • Tonkin- Chris Purton: Senior Meteorologist

  30. Historic Rainstorms and Floods at Strathalbyn • The largest rainfall event in 145 years was the three day rainstorm ending 9am, 26 January 1941 – 217mm • The December 1992 monthly rainfall was 171.2 mm, which was the second highest monthly rainfall on record. The two-day total of 116 mm and the three-day total of 124 mm both had an ARI of just under 100 years

  31. Historic Rainstorms and Floods at Strathalbyn

  32. 1:100yr ARI Flood Plain

  33. 1:100yr ARI Flood Plain • Conclusion • Since the terrain rises steeply from the maximum indicated floodplain extent (without a bund) towards the proposed Tailing Storage Facility site, it is certain that the floodplain extent will not extend any further into the mining lease site than is shown in Figure 1.3

  34. Tailings Storage Facility Summary • Every TSF design has some unique issues • To design a TSF you must do a lot of standard tests to; • Tails characterisation ,sg, sizings, settling rates geochem., etc. • Soil characterisation geotechnical stability, permeability, etc • Seismic susceptibility • There is nothing out of the ordinary in the testwork required in the design for the TSF – follow the relevant codes • What is required is the first of its kind in the world

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