Long Term Performance of Dry Cover Systems for Reactive Mine Waste
Symposium Rouyn-Noranda 2002
Dry cover systems are commonly used at various mine sites around the world to prevent and control acid rock drainage. The primary purpose of these covers is to minimize further degradation of the receiving environment following closure of the waste impoundment by minimizing the influx of water and oxygen into the waste. Dry covers can be simple or complex, encompassing single or multiple layers of native soils, non-reactive tailings and/or waste rock, geosynthetic materials, and oxygen consuming organic materials.
The long-term performance of a dry cover system is controlled by the final properties of the cover materials once they are in equilibrium with in situ and site specific climate/vegetative conditions. It is expected that these properties and site specific conditions may change over a long period of time. The long-term performance of dry covers is being examined in a research study funded by the International Network for Acid Prevention (INAP). The objective of the study is to identify the key properties affecting the long-term performance of cover systems and the physical, chemical, or biological processes that cause the changes in these key properties. The research study has included input from site personnel on the processes affecting cover performance at their specific mine sites. A literature study was also completed to characterize the physical, chemical, and biological processes identified. Field performance monitoring was used to identify changes in the key material properties at a total of five mines sites in Canada, the United States, and Australia. The data was then analyzed to determine which of the physical, chemical, or biological process (or combination thereof) caused the change in the key material property.
This paper will provide background to the processes influencing the long-term performance of dry covers and document field-testing at the case study sites.