The AANDC (Aboriginal Affairs and Northern Development Canada) Northern Contaminated Sites Program (NCSP) is responsible for remediation of contaminated sites on Crown land throughout the Canadian North. A significant percentage of the remediation liabilities faced by AANDC are associated with abandoned mines. Of these mine-related liabilities, a significant number involve the need to construct soil (earthen) covers over reactive tailings and waste rock.
AANDC anticipates that they will implement cover systems at some sites within the next two years. To do so they require additional information on key physical, chemical, and biological processes that affect long-term risk to these cover systems. The appropriate design and long-term effectiveness of earthen covers in cold regions is of central importance to AANDC, as well as to local and regional stakeholders.
The Mine Environment Neutral Drainage program recently completed a Phase 1 review of soil covers on mine wastes in cold regions (MEND 1.61.5a, 2009). Several dozen cold regions processes were identified as potentially important for earthen covers. These effects can develop slowly and may not be immediately evident, but could have significant influence on performance over the operating life of a cover system.
The immediate need of AANDC is for guidance on design of new cover systems at abandoned mine sites in cold regions. To this end, AANDC formed a Technical Advisory Group (TAG) comprised of experts in various fields important to cold region cover system design, to provide advice in the completion of this Guidance Document.
This Guidance Document outlines the current state-of-knowledge of soil cover system design in cold regions, the expectations of AANDC on how a cover system design should be conducted, and a summary of information AANDC expects to receive during the design process so that an informed decision can be made on the preferred design. The information presented in this document is intended to support development of designs associated with closure of abandoned mines, but will also be useful in developing closure plans for operational mines in cold regions.
This is a technical document that fits within the framework of sustainability, including socio-economic and socio-environmental aspects of mine closure. The target audience for this document is AANDC project managers and cover system design practitioners associated with closure and reclamation of mine sites in cold regions (In Canada, cold regions are generally considered those north of 60 degrees, though applicable to any location experiencing significant ground frost). Other groups, such as regulatory agencies, Aboriginal peoples, and non-governmental organizations (NGOs), may find this document of assistance during their review of a proposed design. It is intended to be a resource for guiding cover system designers in evaluating a wide range of possible solutions. AANDC encourages practitioners to consider that when all issues of long-term performance and liability are considered, the lowest cost option for a cold region cover system may not be the ‘best’ alternative.
This Guidance Document describes key attributes of cold regions and the associated challenges of cover system design in these climates. Cover system design is described beginning with an overview of the philosophy of cover system design, basic theory and fundamental concepts, available cover system design alternatives and their pros and cons, and presents a methodology for applying the tools required to meet cover design objectives. At the end of the document, three case studies are presented to illustrate the practical application of cover system design in cold regions.
