PERMFILE52001

• Permit No: C1980007
• IBM Index Class Name: Permit File
• Doc Date: 6/2/2006
• Section_Exhibit Name: Exhibit 60B Subsidence Evaluation for the South of Divide Mining Area
• Media Type: D
• Archive: No

Subsidence Evaluatron For
Exhibit 60B South of Divide Mining Area Page 29
of the cabin (see Figures 7 and 8, of Exhibit 60D for details). The outside walls are of a wood,
board-and-batconstntction.
The foundation, which is of rock and mortar wnstruction (and an estimated 1 %: feet thick),
ranges from about 1 foot high in the back to 20 inches high in the front The roof is covered with
tin. The side windows, which measure 2 by 3 feet in outside dimension, are located in the
approximate center of either wall.
Estimated maximum ranges of vertical displacement (S,°), tilt (Mm), and horizontal tensile and
compressive strain (Em and -Em) in the cow camp cabin area are as follows, assuming 14 R of
coal is extracted (see Table 2, Exhibit 60B):
Sm=9-loft; Mm=2-5%; Em,-Em=0.8-3%.
A.s the longwall mining face moves westward within the area of mining influence of the cabin, a
subsidence wave-moving at about the same sate as the mining face- will pass beneath the
cabin, subjecting it to (1) tilt and strain, (2) then maximum vertical displacement, (3) then
relaxation of these effects, as the longwall mining face moves out of the area of mining
influence.
The cabin, though temporarily tilted until the longwall face moves out of the area of influence of
the cabin, is expected to remain intact during the subsidence episode, because it is small and
light, and of wood construction. However, cracks are expected to oceur in the foundation, in
response to the tilt and strain caused by the subsidence wave produced by the moving longwall
mining face below.
The cracks, which may reach a maximum temporary width of a fraction of an inch to perhaps 1
to perhaps I'/. inches, will likely close again when the longwall mining face moves out of the
area of mining influence of the cabin. A,ny cracks drat develop in the foundation, however, may
wntinue to be visible for the life of the foundation.
Cracks, of as much as 1 to perhaps 1'/a inches wide, are also expected to locally accm- in the Dry
Fork road near the Cow Camp and elsewhere during mining. The cracks will likely close again
once the longwall mining face moves out of the area of influence of the mad area.
12.0 IMPACTS BENEATH THE MINED E COAL SEAM

Based on mapping and observations by the author in the B Seam of the Somerset Mine, impacts
to the coal and rocks below the mined coal bed are expected to be limited to about one mining
thickness. There is no expected mining impact to the underlying D Seam because its tap
commonly occurs at a mining thickness below the base of the E Seam. Furthermore, impacts to
the floors of the mine workings are expected to be limited to the chain pillars, because the floors
of the longwall panels will be loaded with caved roof rocks and overlying strata before
deformation in the floor can occur.
831-032690 Wright Water Engineers, Inc.