PERMFILE41947

• Permit No: C1980007A
• IBM Index Class Name: Permit File
• Doc Date: 4/8/2005
• Section_Exhibit Name: 2.05 Operation and Reclamation Part 2
• Media Type: D
• Archive: Yes

West Elk Mine
I, effects at a longwall mine in northern West Virginia. They stated, "Streams over panels mined out
more than two years ago do not exhibit abnormally low stream floyv. This implies that subsidence
fractures over such older panels have closed or filled with sediment so that streamflow could have
recovered from any previous mining impacts."
To quantify the probability that any given channel in the Apache Rocks or Box Canyon permit
revision azea will encounter a surface crack, there are two basic methods that have been used to
calculate crack occurrence frequency. First, the total perimeter (length) of the mined longwall
panels, as of January 1997, (i.e, panels 1NW through 8NW) is 75~ 000 feet and the total observed
cracked length over the longwall panels (again, exclusively over the pillars) is 115 feet. This
translates into a probability of occurrence of 0.2 percent. The secohd approach is to recognize that
the total surface area of the development mining and chain/barti~er pillazs is approximately 344
acres, while the cracked surface area (104 square feet) is approximately 0.002 acres. This translates
into a probability of occurrence of 0.001 percent.
These calculated risk factors aze important because they enable a~determination of the frequency
with which any given channel is likely to experience a crack. Forlexample, there aze eight stream
channels in the Apache Rocks mining permit area representing 1~8 crossings of the chain/tamer
pillars. At any given crossing, the probability of encountering a crack is 0.2 percent.
Therefore, throughout the entire Apache Rocks mining azea, the combined probability of
encountering a surface crack is only 3.6 percent. Within the Box Canyon mining area, there are
seven stream channels representing four stream systems (i.e., Sylvester Gulch, Box Canyon, the
'• unnamed tributary west of Box Canyon, and an unnamed tributary', to Raven Gulch). These seven
stream channels cross chain barrier pillazs seventeen times. The resulting combined probability of
encountering a surface crack in this azea is 3.4 percent. These risk factors help to put the loss of
surface water due to surface cracking into perspective.
In the unlikely event that a channel does encounter a surface crack; the next questions are: (1) how
much water will be lost?, and (2) what is the significance of the water "loss"? As for question (1), it
is conservative to assume that a crack over a pillar will be 100 feet long, 50 feet deep and
conservatively, an average of 0.5 feet wide, for a total volume of 0.06 acre-feet. A loss of this
magnitude, even if it were to occur a number of times per yeaz, is riot significant. Furthermore, and
of perhaps greater importance, surface flows lost to cracks will still eventually return to the North
Fork (on the north side of the drainage divide) and to the Dry Fork;(on the south side of the divide),
so the water will not be lost to the system.
This analysis conservatively assumes that surface cracks which develop will remain open and that
they will not close with time. However, crack closure is, indeed, very likely. An important
mitigating factor regarding surface water loss into subsidence cracks is "healing" due to expansion
of the materials in the crack. To investigate this subject relative to the West Ells Mine, Mr. Rold
met with Mr. Pat Rogers and Mr. Jeff Hynes of the Colorado Geological Survey in January, 1995.
Both men are experts in the subject of swelling soils and Mr. Hynes is the Colorado Geological
Survey's principal expert on subsidence reseazch and evaluation.
I.
2.OS-l53 November 2004 PRI!