Page 270 - Advances In Productive, Safe, and Responsible Coal Mining

Sustainable coal waste disposal practices 249

Water supply well
Runoff (Make-up water)
Fresh water (optional)
impoundment
Wash plant supply water
Runoff Coarse coal refuse embankment
ROM
coal Coal Coal slurry
preparation
impoundment
(wash) plant
Runoff or dewatered
Clean FCPW fill
coal
Sedimentation Coal stockpiles
impoundment
Thickener
Mine water
supply well
(dust control)
Mine
dewatering Slurry
well dewatering
Alternative slurry facility
processing strategies
Slurry impoundment decant water and runoff
NPDES discharge (periodic blowdown)—Possible discharge to a mixing zone
Fig. 13.1 Schematic of typical coal mine surface support facilities [9].

to the process of obtaining permits for constructing slurry impoundments, many mines
have turned to the disposing of FCPW in older abandoned mine workings such as
underground shafts and tunnels or the final cut of a surface mine. This has led to sta-
bility problems (e.g., reduced bearing capacity of clay strata below the coal seam) in
underground mines and groundwater contamination problems at both surface and
underground mines. Both problems arise from high water content in the FCPW.
Addressing that issue has been the focus of research on constructing monofill refuse
piles from a blend of CCPW and dewatered FCPW, which will be covered later in this
chapter.
The combined trends of mining thinner coal seams with larger, stronger, fully
mechanized equipment have increased the percentage of coal refuse to as much as
50% of the ROM product. These trends, coupled with more stringent regulations to
control air, water, and land pollution, have complicated the already challenging prob-
lem of disposing of coal refuse in a safe and environmentally acceptable manner. As a
result, backfilling, long considered cost prohibitive for coal mines, is becoming more
economically attractive [10]. Testing has concluded that if improved ground control is
the only reason for backfilling, coal refuse alone does not appear to be a suitable back-
filling material; however, if rising coal refuse disposal costs can be abated, then it
becomes much more attractive [11]. The authors believe that the greatest potential
advantage offered by backfilling is increased resource recovery, but this concept still
needs to be demonstrated in the field. This will also be discussed later in this chapter.