Here are ten good questions that could be asked about decommissioning any heap leach pad. I copy them from the Proposed Carmacks Copper Mining Project, Yukon Environmental Assessment Act, Additional Information Requirements.

It is recommended that the proponent prepare supporting documentation on the proposed conceptual heap decommissioning plan... This work should include, but is not limited to, the following considerations:

  1. Discussion of the methods of testing done on the spent ore;
  2. Presentation of all data generated from the tests;
  3. Interpretation of test results, geochemical modelling, and discussion of the feasibility of detoxification of the spent ore, time estimates for how long it will take to detoxify the heap and implications of precipitate formation;
  4. Details of leach rinsing and detoxification procedures including volumes, scheduling, duration, and factors that indicate when rinsing and detoxification will cease;
  5. Design criteria and preliminary design for the closure treatment system;
  6. Discharge effluent quality that protects the aquatic resources in the surrounding environment, and sludge disposal;
  7. A discussion of the risks and uncertainties associated with the conceptual plan;
  8. A evaluation of possible failure modes, contingencies in place, and an evaluation of any risks or uncertainties;
  9. Description of ongoing or planned studies, objectives, and scheduling; and how study results will be incorporated into the heap decommissioning plan; and
  10. Activities to be implemented in the case of a temporary closure including criteria to define when temporary closure constitutes permanent closure and final reclamation measures are to be implemented.

The heap leach in question is described briefly in the Project Description and Environmental Assessment Report, Carmacks Copper Project, June 2005.

After mining ceases, site infrastructure will be dismantled and removed from the site. Where appropriate, slopes on the waste rock storage area and heap will be recontoured, covered with stock piled overburden material, and revegetated. Roads and disturbed areas will be decompacted, scarified and revegetated. When leaching is no longer economic, an evaporative transpiration soil cover will be installed. The heap will be rinsed for approximately two to three years with water and then neutralized. In situ biological treatment will be undertaken in the heap to assist in stabilization of metals. Active water treatment using conventional lime treatment will be used to reduce the heap solution inventory. Once heap effluent performance standards are achieved, a long-term passive treatment (infiltration gallery) is proposed for final closure.

This report also provides a long description of the proposed heap leach pad. It is worth reading if you are interested in heap leach pads. Other documents also readily available on the Yukon Government website, that you may want to read include:

Carmacks Copper Project Additional Information Requirements

Carmacks Copper Project Description and Environmental Assessment Report

Carmacks Copper Project Description and Environmental Assessment Report Volume 2

Carmacks Copper Project Consultation Document

Carmacks Copper Project - Notice of Minister's Track Decision

Carmacks Copper Project - Track Report

Carmacks Copper Project - Draft Comprehensive Study Report