Dirk van Zyl

Professor, University of British Columbia, Canada

Mike Milczarek

President, GeoSystems Analysis, USA

Stephen Taylor

President, Picacho Associates, USA

 

Minimum 18, maximum 50 delegates
Regular 5100/5400 ZAR, Students 3600 / 3900 ZAR

 

Workshop Need

Water management to control surface water and reduce net infiltration into mine waste facilities is the most important issue for mine closure. Failure to properly design for surface water and net infiltration control can lead to erosion damage to cover systems and drainage channels and increased water treatment costs from excessive net infiltration and subsequent mine waste drainage. This workshop is designed to provide an integrated assessment of major closure water management issues across a variety of climatic environments and present standard and cutting-edge methods for surface water and net infiltration control systems. Participants will benefit from this short course through introduction to characterization, analysis and modeling tools to predict surface water dynamics and infiltration into cover systems as well as state-of-the art methods in measuring and monitoring flow through cover systems. Closure case studies from several different climatic environments will be presented.

Target Audience

The course is designed for scientists and engineers who practice in the areas of reclamation and mine closure to enhance participants’ general knowledge and provide tools for the design, modeling and monitoring of mine water management systems.

Short Workshop Programme

The workshop programme will consist of five sessions that will consist of:

Part I – Designing for Long-term Risk Management (Dirk van Zyl)
Part II – Surface Water Control Design (Taylor)
Part III – Material Characterization and Cover System Design (Milczarek and Taylor)
Part IV – Closure System Monitoring (Milczarek)
Part V – Closeout Session (All)

Extensive use of case studies and examples will be provided

Detailed Workshop Programme

Part I – Designing for Long-term Risk Management (Dirk van Zyl)

This introductory session will provide the water management considerations for mine closure. It is as much a mine life issue as it is a closure issue and these concepts will be emphasized using some case examples. Risk assessment and management are important aspects with respect to water management will be explored, considering surface water management, infiltration control, metal leaching considerations and control. This session will establish the framework for the rest of the short course.

Part II – Surface Water Control Design (Taylor)

This session will start with choosing design storms based on the property risk profile, regulatory requirements and individual design components’ risk profiles. The design storm review will cover standard methodologies with more modern methods that use large data sets gathered from weather radar. The design storm review will consider:

  • Probable Maximum Floods
  • 100-year 24-hour, and similar storms
  • Short duration storms for erosion design
  • Seasonal/ decadal variations appropriate for water storage, or water accumulation, and how to use this information in a water balance

We will then show how to use this information to design appropriate surface water
control structures required by closure design criteria to include:

  • Overall geometric layout; considering property and downstream constraints, topography, terrain, geology, storm-type, owner’s design philosophy; and the required hydrologic and hydraulic modelling.
  • Retention and detention basins
  • Steep down drains and spillways, comparing various channels and pipe designs
  • Conveyance Channels
  • Infiltration

We will consider a variety of construction materials, to include:

  • Soil, Rock (riprap), Concrete
  • Articulating concrete block
  • HDPE, PVC, EPDM, Bituminous, HydroTurf and other liners
  • Gabions
  • Indigenous solutions, e.g. Inca rock
  • HDPE, Steel, PVC and other drainage pipes

We will consider various imposed physical and environmental stresses, to include:

  • Wear, abrasion, and corrosion
  • Chemical reactivity (for both clean and impacted water)
  • Material creep
  • Settlement
  • Structural/ Slope failure
  • Leakage
  • Sedimentation

Finally, we will consider constructability, capital and maintenance costs, and robustness of the various alternatives. The session will include both theoretical and practical considerations and will present examples from the presenters’ experience.

Part III – Material Characterization and Cover System Design (Milczarek and Taylor)

This session will focus on appropriate field and laboratory methods to assess on-site materials for use in cover systems and also the use of geosynthetic liners to control net infiltration. Session topics will include:

  • Design objectives
  • Identification of borrow sources (quality and quantity); options for blending, use of mine waste rock, rock and tailings
  • Measurement of hydraulic properties of porous media
  • Effect of gravelly material on hydraulic properties
  • Recommended field and laboratory measurement tests
  • Use of models to assess cover system performance

Case studies will be presented for evapotranspiration covers in a variety of climates and the use of composite liner systems. A review of modeling vs actual performance at various sites will also be presented.

Part IV – Closure System Monitoring (Milczarek)

This session will focus on appropriate field methods to measure surface water runoff, surface erosion, net infiltration and the selection and design of appropriate monitoring systems depending on sites-specific conditions. Session topics will include:

  • Monitoring objectives
  • Design of lysimeters and instrument nests
  • Instrumentation for subsurface sampling and testing of solution, oxygen and temperature, water content and pressure potential
  • Geophysical measurements
  • Installation methods to ensure success
  • Data collection and analysis

Monitoring case studies will be presented for semi-arid deserts, cold deserts, high elevation and excess precipitation climates. Recommendations for instrumentation and monitoring approaches will be presented.

Part V – Closeout Session

This session will discuss new ideas and approaches not yet implemented and will allow
participants to discuss specific examples issues they may have.