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Mineral Resources in the Republic of Serbia – 8th Annual Conference 13 November 2018
Environmental Protection Challenge: Managing Mine Waste Richard Elmer, Knight Piésold Consulting, London
Introduction
Common Challenges
Design Considerations
Examples: Olovo Mine - Bosnia
Cononish Mine - Scotland
Managing Mine Waste
Introduction
Introduction About Knight Piésold
Overview
• Established in 1921 • Offices in 15
countries • Over 850
professionals • Re-established in
the UK in 2013
Industries
• Mining • Power • Water Resources • Infrastructure • Oil & Gas
Tailings
• Designing Tailings Management Solutions Since the 1940’s
• Over 500 Tailings projects in the last 20 years
KP London
• Dedicated team of geotechnical engineers
• In 5 years: • Over 50 mines /
projects • 40 client
organisations • 30 countries
Managing Mine Waste
Managing Mine Waste
Mine Waste (Tailings)
Space – Projects often have limited space to accommodate tailings. Each project looked at individually to create optimum space saving solutions
Cost – Staged approach to spread the cost i.e. low CAPEX and higher OPEX for when finance is more available during production
Contamination Risks – Designs for the safe storage of mine waste according to local requirements and international best practice on all facilities
Mine Waste as an Afterthought – Often mine waste is only considered at a very late stage in the process. However, without a safe mine waste storage facility there is no mine.
Common Challenges
Managing Mine Waste
Mine Waste (Tailings)
Standards: ICOLD, ANCOLD, CDA, EU Waste Directive, local requirements BAT
Location: decision based on engineering (eg topography, water return requirements), environmental (eg sensitive receptors, climate) and economic factors (eg distance from plant, CAPEX, OPEX)
Site characterisation: ground investigation including geotechnical and hydrogeological
Tailings characterisation: physical (eg PSD, SG, consolidation, compaction) and geochemical (eg potential acid generation, metal leaching)
Capacity: Life of Mine requirements (typically 10 to 25 years); staged raise to spread cost; 3D modelling (eg Muck3D, AutoCAD Civils 3D)
Deposition modelling: distribution pipeline sizing and routing; spigot spacing (Muck3D)
Design Considerations
Managing Mine Waste
Mine Waste (Tailings)
Confining embankment design: material source, zonation / filter relationships; raise design; drainage
Seepage and stability: eg Slide, Slope/W, FLAC - including static / pseudo static & liquefaction assessment
Lining design: regulatory requirements, permeability requirements, drainage – hydrogeological risk assessment
Surface water management: diversion channels; seepage collection and treatment
Operation: OMS manual, instrumentation (eg piezometers, survey, inspection / audit)
Closure design: progressive restoration, wet or dry storage, monitoring, innovative designs, post closure use eg grazing, photovoltaics, parkland
Design Considerations (Cont.)
Examples
Managing Mine Waste
Small Scale Stacked Tailings
Small scale Cerussite Mine in Bosnia, LoM 15 years, approximately 2.2MT Tailings expected.
Located in a narrow valley with boundary constraints
Ground water supplies the local town of Olovo
Geology is Karst Limestone with visible solution features on the surface
Olovo Lead Mine, Bosnia and Herzegovina
Small Scale Stacked Tailings
Options study looked at a conventional tailings slurry with dam, filtered tailings “dry” stack, and a combination
Assessed lining of facility (clay vs HDPE or combination)
Small scale site investigation to assess the karst nature
Stacked filtered tailings chosen for final design based on environmental stability, restoration options and aesthetics.
Olovo Lead Mine, Bosnia and Herzogovina – Options
Managing Mine Waste
Small Scale Stacked Tailings Cononish Gold Mine, Scotland
Gold mine located in Scotland, UK
– Small output - 36,000 tpy
– LoM 16 years, total tailings 0.5 Mt
Sensitive location - in a national park
Previous design:
– Conventional cross-valley TMF
– Slurry tailings
– Downstream water collection pond
– Significant river diversion
– High CAPEX
Managing Mine Waste
Small Scale Stacked Tailings Cononish Gold Mine, Scotland
Stacked Tailings Concept
Revised concept using moraine shaped filtered tailings stacks
Sympathetic to the existing landscape during construction and closure
Avoids watercourse diversion - 30 m standoff from water courses, catchment
runoff intercepted and diverted (upstream of stacks)
- rainfall on stacks captured and stored in settlement pond
- water discharged to meet current standards Initial basal drainage layers Geotextile separator Filtered tailings placed in 300 mm layers and
compacted to 95% OMC Provides a cost effective solution to the project
Managing Mine Waste
Managing Mine Waste
Filtered stacked tailings not just for major projects in dry climates
Cost and environmental advantages for small scale operations in sensitive locations
Minimises need for expensive surface water management
Spreads cost of tailings management through life of mine as a continuous process (not big steps in costs for initial dams and subsequent raises)
Can be higher cost per tonne of tailings, but cost is spread
Appeals to regulators – amendable to progressive restoration
Opportunities for small scale narrow vein high grade mining in remote locations as a low cost tailings solution
Conclusions
