drystacking

Drystacking, or dry stacking tailings, is a tailings management method used in mining in which filtered tailings are dewatered to a relatively dry, granular material and deposited as a stack in a designated area rather than as a continuous slurry in a conventional tailings dam. The approach aims to reduce water use, minimize seepage, and improve the stability and recoverability of tailings storage.

The process typically involves filtering or filtering-plus-thickening to remove most of the free water from tailings. The dewatered material is then transported to a deposition site and laid down in layers or lifts. Each lift is compacted and graded to promote drainage, and runoff and seepage are managed with engineered drainage systems. The deposit is designed to remain stable under local climatic and seismic conditions, with ongoing monitoring for settlement, slope stability, and wind or water erosion.

Advantages of drystacking include reduced water consumption and enhanced structural stability compared with conventional slurry tailings dams. It can lower the risk of catastrophic dam failure, reduce long-term water management liabilities, and facilitate land reclamation and potential reuse of the tailings storage area after closure. Drystacking can also improve time-to-reclamation and may reduce environmental and social licensing constraints in some jurisdictions.

Challenges and limitations include higher capital and operating costs for filtration infrastructure, energy requirements, dust control and fugitive emissions, and the need for suitable topography and climate. Not all ore types are amenable to filtration and stacking, particularly fine- and clay-rich tailings. The method requires careful geotechnical design, robust water and dust management, and adherence to tailings governance standards and regulatory requirements.