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”
Many audience members would be familiar with the problems associated with the Brukunga mine site in the region.
The environmental risk associated with storage of tailings is due to the presence of other metals in the ore body.
When rains flush through uncapped or poorly stored tailings high in iron-sulphides, reactions occur, and sulphuric acid is released to the environment.
Tailings are stored in a variety of ways: all are generally referred to as Tailings Storage facilities (TSF)

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. Australian Tailings Consultants TSF objective:
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 un-thickened tailings
Smaller footprint
No requirement for thickener
No requirement for flocculent
Simpler (& therefore cheaper) to operate.
No requirement for pneumatic pumping

10. 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
Particle segregation

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

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

13. Water management

14. TSF - Water Management

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

16. 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

17. The TSF Design Selection

18. TSF Design

19. Risk Analysis

20. TSF-Risk Analysis

21. TSF location & detail

22. TSF construction: base layer

23. TSF options- detail
Proposed Design Option: Decant well

24. 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

25. TSF Closure

26. TSF Closure: capping layers

27. TSF Closure

28. 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

29. Flood Plain Modelling

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

31. 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 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

32. Historic Rainstorms and Floods at Strathalbyn

33. 1:100yr ARI Flood Plain

34. 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

35. 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