Construction of a Dam - Step 1
To build a dam the engineers must first de-water the part of the river valley in which they wish to place the dam. This is usually achieved by diverting the river through a tunnel.
The tunnel is built through one side of the valley around the planned construction area. A series of holes is drilled in the rock. Explosives are placed in the drill holes, blasting takes place and broken rock is then removed. This procedure is repeated many times until the tunnel is completed. Diversion tunnels are often lined with concrete.
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