The tailing dam should be located where the slope of the ground enables the pulp to be retained with the minimum length of artificial embarkment, since its height has got to be raised at frequent intervals as the basin becomes full. The area enclosed has to be large enough to allow for the settlement of the solid material, including the finest slime, at the maximum rate of inflow, so that clear water can be continuously decanted off and pumped back to the plant.
In the case of a new dam being established, an embarkment of earth or masonry is normally first constructed to the height of a few feet, but subsequently the tailings deposited in the basin are utilized to raise it. This is usually done by hand, on a small scale. The dam is usually divided into 2 sections, and while 1 section is being filled, the wall of the other is raised a metre or two with material excavated from the edge of the basin.
If the large part of the tailing is coarse and granular, the wall can be built by direct deposition from the pulp as it enters the dam without the need for excavation. A launder to carry the tailing is placed for the purpose a few metres above the embarkment along its entire length, and holes are bored in the side of bottom at short intervals to direct a series of streams of pulp inside the inner edge of the existing wall. The coarse portion of the tailing settles where it falls in a series of conical piles, which eventually become large enough to join up, forming a continuous wall.
The fines flow into the interior of the dam where they settle, and clear water is drawn off at the far end through a decanting pipe. When the wall reaches the level of the bottom of the launder, the pulp is turned into a new one erected for the purpose at a higher level, the old launder being removed and used again.
