MEND 2.21.4 (Design, Construction, and Performance Monitoring of Cover Systems for Waste Rock and Tailings, 2004) is comprised of basic theory, laboratory site and field characterization methods, conceptual design and approach to numerical modelling, and field performance monitoring of test-scale and full-scale cover systems. Understanding the dynamics of the cover system is an important concept to grasp because it is the interface between the waste material and the environment. However, to evaluate the success of reclamation of an entire area, evaluation criteria need to be expanded on a larger scale, which leads to the development of the current manual, MEND 2.21.5.
The primary objective of this manual is to introduce design and monitoring guidelines for mine waste soil cover systems on a macro-scale, i.e. a watershed and landform-scale, and the challenges that arise due to the increased size and complexity. Design guidelines for covers on a macro-scale are largely governed by the same guidelines as for landform design (landform engineering). A key design issue for a newly reclaimed landscape is to create an initial condition so that the landscape follows a suitable trajectory of evolution both in terms of rate of change and end point. Background on the need for landform design and some general guidelines for landform design that also apply for cover design on a macro-scale are given in Section 2 of this manual.
One of the greatest challenges is the ability to predict and quantify what changes may occur that can potentially affect the integrity of a soil cover system. In order to meet or design for the expectations set, an understanding for the long-term behaviour of the system is necessary which lies in understanding the processes that lead to change. Macro-scale cover evolution, which is discussed in Section 3 of this manual, follows many of the same guidelines and is governed by the same processes as landform evolution. Long-term field performance monitoring of reclaimed sites becomes an important element to defining the critical trajectory by determining the associated mechanisms and processes that cause the landscape to evolve. Syncrude Canada Ltd. is introduced at the beginning of Section 3 as a case study to illustrate the challenges and lessons learned in terms of tracking the evolution / performance of some of their reclamation covers.
Macro-scale monitoring is a tool that is used to characterize conditions, processes, and interactions within a watershed to provide a systematic method to understand and organize ecosystem information. In so doing, watershed analysis enhances the ability to estimate direct, indirect, and cumulative effects of management activities and guide the general type, location, and sequence of appropriate future management activities. The majority of the monitoring methods presented in Section 4 of this manual were ‘fine-tuned’ years ago at a micro-scale level, and can be easily applied in the scope of a macro-scale cover monitoring program. Monitoring challenges are highlighted throughout Section 4 with examples from Syncrude Canada Ltd.
Detailed information related to the various surface and sub-surface hydrologic monitoring methods and instruments can be found in Appendix A.
The application of hillslope hydrology for design of watersheds to reclaim large mine waste storage facilities is relatively new. Hence, the information presented in this document should be viewed as a report on a “work in progress”. Research in this area is on-going with design methods yet to be fully developed and proven, which will allow them to be put into practice with confidence that a reclaimed watershed design will be sustainable over the long term.
