Ready to Discuss Your Mine Closure

We’ve helped companies, governments, and NGO’s safely close mines. Let’s discuss the specifics of your project.

Get Started >

Performance Monitoring

Historically, one of the most common technologies used for evaluation of cover system performance has been water quality analyses of seepage discharged from mine waste storage facilities. Water samples are typically collected from collection ditches around the perimeter of a waste storage facility or from monitoring wells installed below or down-gradient of the site. While this approach empirically describes performance of a rehabilitated facility through monitoring of its cumulative effect at the base, it may take several tens of years before seepage water quality improves. This is due to the storage capacity in the waste material and the length of time it takes for the phreatic surface to equilibrate with local hydrogeologic conditions.

An eddy co-variance station measuring actual evaporation from the surface of a waste rock pile.Direct measurement of field performance is the state-of-the-art methodology for measuring performance of a cover system for reclaimed waste storage areas. This is the best method for demonstrating to all stakeholders that the cover system will perform as designed. For a full-scale cover system, a recommended minimum level of monitoring should include climatic conditions (for determination of potential evaporation rates), site-specific rainfall, cover material moisture storage changes, watershed or catchment area surface runoff, vegetation success, and erosion.

A ‘watershed’ approach to monitoring is preferred in order to gain a better understanding of cover system performance under site-specific conditions. The rationale for utilizing a watershed approach is such that it allows for the complexity and challenges of cover system performance monitoring, which are apparent given the scale increase of a cover system from a point-scale (e.g. a test plot) to a macro-scale (e.g. a watershed). Although most monitoring techniques used in point-scale cover system monitoring can be applied for macro-scale cover system monitoring, the extent of performance monitoring for a macro-scale cover system is much broader than that for a point-scale cover system. The performance monitoring and evaluation of a macro-scale cover system considers the temporal and spatial variability of the field measured datasets. The monitoring frequency (scale) for obtaining sufficient data, which is associated with spatial instrumentation and temporal data acquisition, must be understood in order to deploy a cost-effective monitoring system.

A large-scale lysimeter designed to measure net percolation rates from a cover system field trial.OKC has extensive experience in field performance monitoring to support mine closure planning studies. Our areas of expertise include:

  • Meteorology,
  • Actual evapotranspiration,
  • Surface runoff,
  • Interflow or lateral subsurface drainage,
  • Soil conditions (temperature, water content, pore-water pressure),
  • Distributed temperature sensing systems,
  • Field permeability assessments,
  • Net percolation (lysimeters),
  • Rates and controls of geochemical reactions,
  • Pore-gas chemistry and flux quantification,
  • Pore-gas and water isotopes,
  • Tailings settlement, and
  • Tailings dewatering (solids content and shear strength development).

This cover system field trial is instrumented with a climate monitoring station, soil moisture monitoring instrumentation, and two wind-shielded precipitation gauges.