An impoundment is a structure used for storage of mining or mineral processing wastes. Impoundments are generally constructed in natural basins or by building embankments (or dam-like structures.) Impoundments can incorporate both "coarse" (large particles like rocks) and "fine" (small particles like sand and silt) refuse. The coarse refuse is often used to create the embankment, which then holds the fine refuse dam which then holds the fine refuse. Fine refuse is often pumped to the impoundment as a slurry (i.e., water + fine particles). As the fine particles settle, the objective is to recycle the clear water back to the mine or processing plant to re-use.

Figure: An impoundment is like a big pond used for waste disposal and water recycling. (Note: "refuge" in the figure should be "refuse")