Many of the man-made ponds for storing toxic sludge from coal mining operations have dangerously weak walls because of poor construction methods, according to the synopsis of a study for the Office of Surface Mining Reclamation and Enforcement obtained by The Washington Post.
Tests of the density of these impoundment walls showed flaws at all seven sites surveyed in West Virginia, with only 16 field tests meeting the standards out of 73 conducted, the 2011 report says.
Slurry, also known as coarse coal refuse, is what is left over once companies wash coal to enable it to burn more efficiently. Coal firms have disposed of this combination of solids and water in a few different ways: damming it in large ponds, depositing it in abandoned mines and using a dry filter-press process to compact it.
The Interior Department’s mining agency ordered the survey — which is in draft form and has not been publicly released — after its engineers noticed that companies were using coarse refuse that will not stay compacted except “within a narrow range” of moisture conditions, according to the synopsis. The conditions were not monitored and bulldozers were used to compact the soil, a task for which they are poorly suited, it added.