Method of excavating a tailings lagoon

Abstract

A method of dewatering a tailings lagoon retained by a dam comprising: excavating an excavation hole in the tailings lagoon; allowing water from surrounding tailings to enter the excavation hole; and pumping water in the excavation hole out of the excavation hole and discharging beyond a toe of the dam. Also disclosed is a method comprising: excavating a channel in a tailings lagoon from a shore of the tailings lagoon and floating a pontoon in water in the channel from the shore along the channel,wherein: excavating involves breaking down solid tailings in the tailings lagoon into a slurry using water and removing the slurry using a submersible slurry pump mounted on the pontoon.

1 . A method comprising:
 excavating a channel in a tailings lagoon from a shore of the tailings lagoon and floating a pontoon in water in the channel from the shore along the channel, wherein:   excavating involves breaking down solid tailings in the tailings lagoon into a slurry using water and removing the slurry using a submersible slurry pump mounted on the pontoon.   
     
     
         2 . The method of  claim 1 , wherein:
 during the excavating the water for breaking down the solid tailings is supplied by the pontoon.   
     
     
         3 . The method of  claim 2 , wherein:
 the water supplied by the pontoon is at least partly water extracted from the channel by the pontoon.   
     
     
         4 . The method of  claim 1  wherein:
 during the excavating water is provided to the pontoon from a shore of the tailings lagoon. 
 
     
     
         5 . The method of  claim 1 , wherein:
 water is supplied to the channel during excavation from beyond the tailings lagoon.   
     
     
         6 . The method of  claim 1 , wherein:
 the amount of water contained in the slurry (density) is controlled to be a certain level.   
     
     
         7 . The method of  claim 6 , wherein:
 the amount of water contained in the slurry is controlled by varying the depth below the pontoon of the slurry pump.   
     
     
         8 . The method of  claim 6 , wherein:
 the amount of water contained in the slurry is controlled by varying the flow rate of water used in breaking down solid tailings.   
     
     
         9 . The method of  claim 6  wherein:
 the amount of water contained in the slurry is controlled by varying a flow rate of water provided to the slurry pump and discharged by the slurry pump. 
 
     
     
         10 . The method of  claim 6 , wherein:
 the removed slurry travels from the slurry pump to a discharge point along a pipe and the amount of water contained in the slurry in the pipe is controlled by varying the amount of water added to the pipe at a position between the slurry pump and the discharge point.   
     
     
         11 . The method of  claim 1 , wherein:
 the pontoon is controlled remotely from a shore of the tailings lagoon.   
     
     
         12 . The method of  claim 1 , wherein:
 a water jet propels the pontoon along the channel.   
     
     
         13 . The method of  claim 1 , wherein a plurality of water jets on the pontoon control the pontoon directionally. 
     
     
         14 . The method of  claim 1 , wherein the removed slurry is reprocessed to remove a material contained in the slurry. 
     
     
         15 . A method of dewatering a tailings lagoon retained by a dam comprising:
 excavating an excavation hole in the tailings lagoon;   allowing water from surrounding tailings to enter the excavation hole; and   pumping water in the excavation hole out of the excavation hole and discharging beyond a toe of the dam.   
     
     
         16 . The method of  claim 15 , wherein:
 a pontoon floats in water in the excavation hole and supports equipment used for the step of pumping water.   
     
     
         17 . The method of  claim 15 , wherein:
 before excavating the excavation hole, the pontoon is floated along a channel in the tailings lagoon to the location at which the excavation hole is to be excavated using the method of  claim 1 .   
     
     
         18 . The method of  claim 15 , wherein:
 dewatering is localised to tailings adjacent the dam.