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 Design selection Closure Location – Flood Plain

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)

THE TSF DESIGN PROCESS

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

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.

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***

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***

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

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

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

Thickened tailings Wheaton River’s, Peak Mine - Cobar

Water management

TSF - Water Management

TSF - Water management: Water from TSF to Plant

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

The TSF Design Selection

TSF Design

Risk Analysis

TSF-Risk Analysis

TSF location & detail

TSF construction: base layer

TSF options- detail Proposed Design Option: Decant well

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

TSF Closure

TSF Closure: capping layers

TSF Closure

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

Flood Plain Modelling

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

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

Historic Rainstorms and Floods at Strathalbyn

1:100yr ARI Flood Plain

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

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