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 nonsaleable 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 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 - 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 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 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
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
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