Coal sludge impoundments are the most common and cheapest method of disposing of preparation plant waste. The coarse refuse (or waste rock and clay) is used to construct a massive dam behind which the coal sludge is pumped. The dams and impounded slurry or sludge are often euphemistically referred to as "ponds," but "toxic lake" is the accurate name, as coal sludge impoundments can store billions of gallons of liquid coal waste. Coal companies usually build these dams in the heads of hollows (valleys), close to their coal processing plants. Most impoundments are not lined in any way. When an impoundment fills up with fine slurry particles and is abandoned, the remaining water is pumped off and the slurry is "capped" with a layer of coarse refuse. Nobody knows how long it takes for an impoundment to dry out completely or how long they continue to leech heavy metals.
|Marfork Coal Co.'s (Massey Energy) massive Brushy Fork impoundment near Whitesville, WV, is designed to hold 9 BILLION gallons of sludge.|
There are hundreds of coal sludge impoundments throughout the country with over 110 in West Virginia alone. Impoundments range in size from tens of millions of gallons to billions of gallons. In West Virginia alone, impoundments are permitted to contain over 100 billion gallons of slurry.
Coal sludge impoundments have been around in some form since mining began. The first impoundments were relatively small and largely unregulated. Even after the Aberfan Distaster in Wales in 1966 where over 100 school children were killed by a coal waste pile failure, impoundments received little scrunity in the US. It wasn't until 1972 when a sludge impoundment failed in Buffalo Creek, WV killing 125 and leaving thousands homeless that impoundments were truly regulated. Impoundments are now monitored by both the DEP and the Mine Safety and Health Administration.
Despite the regulations and the coal industry's insistance that impoundments are "the most heavily engineered structures that anybody builds", impoundments have continued to fail. In 2000 in Martin County, KY, slurry from an impoundment "broke through" into abandoned underground mines below it. Over 300 million gallons spilled, destroying the town of Inez and polluting the Big Sandy River. Since the Buffalo Creek Disaster and the regulations of impoundments, there have been at least 16 spills of over one million gallons and countless smaller spills.
Spills and catastrophic failure aren't the only things to worry about with a sludge impoundment in your backyard. Impoundments are designed to leech a certain amount and the effects on local groundwater are not well-known. In one case in Clinton County, Illinois, seepage from a coal sludge impoundment polluted the 10,000-acre Pearl Aquifer contaminating local drinking water.
One increasingly popular alternative to coal sludge impoundment is slurry cells. Slurry cells are smaller pits built from coarse refuse. These cells are quickly filled, capped with refuse, and new cells built on top of them. Slurry cells limit the potential for catastrophic failure since they hold a lot less slurry at one time. However, the potential for smaller spills and long term water contamination is just as high.