Figure 1:Looking at the hydraulically mined tailings
Introduction
The mine has three tailings dams that currently need to be moved for environmental reasons. Two of these deposits are located in a steep narrow valley with the third deposit being located on the side of a valley.
The use of hydraulic monitors is considered as the only economical option as blending of the coarse fraction with the middlings and fines allows pumping of the tailings. However, the tailings are mixed with rock deposited during the construction of the impoundment and the subsequent impoundment division to form road ways. A small amount of rock has deposited from avalanche scree from the steep valley sides. The rock will have to be removed by mechanical methods that have to work in dry conditions. This poses a problem for the hydraulic operation which can be solved by having two mining areas to allow mining, drying and then rock removal. Dredging of the material in the dams would cause damage to the mechanical equipment and pumps, also dry load and haul is considerably more expensive than hydraulic mining.
A production rate of 19,000 tonnes per day over an 8 month annual cycle is required to make the operation a success. Mining during the winter months poses hazards from avalanches, blizzards and freezing of pipelines and mechanical equipment (Cuevas, Jansson et al.).
During the mining operation the screened material is then pumped to a header tank almost 5 km away at a height elevation of 200 m. From the header tank the tailings are gravitational fed to a new tailings impoundment 50 km away. In the future mining of the saturated zone will pose a great challenge. Early indications show that floating equipment should be used to prevent a liquefaction event from occurring and risking the lives of the operators.
References
Cuevas, R., D. Jansson, et al. "Hydraulic Mining: An Alternative Solution."
Engels, J. and D. Dixon-Hardy (2004). Tailings disposal - Today's storage of high volumes of waste from mines. JKMRC Conference 2004, Brisbane, Australia.
