Upload
rosaline-malone
View
219
Download
0
Embed Size (px)
Citation preview
TERRAMIN AUSTRALIA LimitedTERRAMIN AUSTRALIA Limited
Angas Zinc Angas Zinc ProjectProject
Tailings Storage Facility Tailings Storage Facility Overview 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: Angas Zinc Project: Tailings storageTailings 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”
THE TSF DESIGN PROCESS
TSF GuidelinesTSF 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
TSF - designTSF - 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 -TSF -The TestworkThe 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 - TSF - Tailings Handling OptionsTailings 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 thickened tailingsAdvantages 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
TSF - Thickened tailingsTSF - Thickened tailings
• Wheaton River’s, Peak Mine - Cobar
Thickened tailingsThickened tailings
• Wheaton River’s, Peak Mine - Cobar
Water management
TSF - Water TSF - Water ManagementManagement
TSF - Water management: TSF - Water management: Water from TSF to PlantWater from TSF to Plant
TSF - Water managementTSF - 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 DesignTSF Design
Risk Analysis
TSF-Risk AnalysisTSF-Risk Analysis
TSF location & detailTSF location & detail
QuickTime™ and aTIFF (LZW) decompressor
are needed to see this picture.
TSF construction: base layerTSF construction: base layer
TSF options- detailTSF options- detail
• Proposed Design Option: Decant well
TSF DesignTSF 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 layersTSF Closure: capping layers
TSF ClosureTSF Closure
TSF ClosureTSF 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 ModellingFlood Plain Modelling
TSF placement to meet outcomesTSF 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 Tailings Storage Facility SummarySummary
• 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