Implication of the permafrost on hydrogeological conditions and on mine environment controls: case of the Amaam Coking Coal Project in north-eastern Russia

 

The Amaam Coking Coal Project is located in the extreme north-east of Russia, near the Arctic Circle and comprises the following key components; a large scale open cast mine producing premium coking coal, a sea port, and road and rail connection from the mining areas to the port. In this environment, two main groundwater systems within the project area have been identified: a shallow groundwater regime above the permafrost zone made of an active layer aquifer and post-glacial alluvial deposit aquifer(s), and a deep groundwater regime beneath permafrost made of deep bedrock aquifer(s). Within these regimes, fresh to brackish groundwater is anticipated to occur within Quaternary and post glacial unconsolidated sediments, weathered and fractured bedrock and deep bedrock formations containing the coal seams. Although the project is located within a widespread permafrost region, it is understood that the low-lying areas adjacent to surface water bodies, rivers and lagoons, are unfrozen throughout the year, and therefore lie in a talik area (or unfrozen grounds encountered within the permafrost zone). The intermediate bedrock aquifer(s) within the flood plain taliks may be hydraulically connected to the deep bedrock aquifer(s) and fractures / faults present in these areas can potentially conduct surface waters into the various water-bearing strata during seasonal thawing if not acting as groundwater barriers. Although the surface-groundwater coupling is not fully understood, the following likely changes to the groundwater conditions resulting from the mine development may include: potential changes to groundwater flow; changes to groundwater quality; changes to surface water / groundwater interactions; and changes to geotechnical conditions. Preliminary estimates of potential groundwater seepage into mine areas are in the range of 2,000 to 55,000 m3/d. Most of this flow is anticipated to originate from the unconsolidated Quaternary deposits. Refinement of these estimates will occur following a better appreciation of the thickness of permafrost and the location and thickness of talik areas. The hydrogeology of the Project is therefore substantially controlled by the permafrost characteristics and its spatial and temporal distribution.