tailings pond

Modern mining operations in the United States are required to contain and treat their waste piles because of the toxic cocktails they contain: zinc, copper, mercury, cadmium, lead, and other heavy metals are commonly present, along with the acids of cyanide and sulfur that are used in slurry extraction processes. The resulting dammed depressions are not ponds in any sense dreamed of by Thoreau at Walden, but rather, immense puddles of suspended pollutants. The hazards of holding volumes of poisonous fluids above ground are obvious: foundation seepage, seasonal flooding, or structural collapse will release the concentrated toxins into groundwater or the receiving watershed.

Barbara Kingsolver