2023-04-19_PERMIT FILE - C1981010 ‎(97)‎

• Permit No: C1981010
• IBM Index Class Name: Permit File
• Doc Date: 4/19/2023
• Doc Name: pages 4-1 to 4-100
• Section_Exhibit Name: 4.0 Protection of the Environmental & Public Resources
• Media Type: D
• Archive: No

Disposal sites will be selected on a cut by cut basis for each pit to ensure the
depth of disposal is at least ten feet less than the depth to the maximum poten-
tial water table. 2iezometric surfaces within the pits will be evaluated during
future studies and disposal criteria may be modified to reflect this information.
Figure 4.3-22 depicts a situation where a backfilled pit cut has filled with water
until the water level reaches the elevation of the pit crest at its northern end.
At this point, the water will escape by a spring or seep. In actuality, the water
table may mound and somewhat exceed the pit crest elevation. The maximum poten-
tial extent of this mounding can be mathematically predicted.
A flow line passing from a more porous material (backfilled spoils) to a less por-
ous material (contiguous undisturbed geologic strata) will obey the law of inci-
dence and refraction given by:
K, tan a,
K tan a2
where K = gpd/ft.2
+ t +t++ +{+ F+
++ ++
} +++ ..
++ +
+a1 1+ }
+ + +
+ $}+ ++ +
+ +, +
K, > kz
Therefore, springs or seeps will only develop at .the north end of the pit cuts
where the recharge amount exceeds the conducting capacity of the high wall face.
7-8-82
4-98
potential ground water level in the lower
ends of the pits on the basis of topo-
graphy and the pitch of the coal. Figure
4.3-22 provides a
conceptualization of
this determination. As is evident from
the figure, spoil
trough disposal is
•
acceptable closer to the north end of the
pits than is spoil
bench disposal. In
turn, spoil bench disposal can be safely used closer to the lower
end of the pits
than bottom of the pit disposal can.
Disposal sites will be selected on a cut by cut basis for each pit to ensure the
depth of disposal is at least ten feet less than the depth to the maximum poten-
tial water table. 2iezometric surfaces within the pits will be evaluated during
future studies and disposal criteria may be modified to reflect this information.
Figure 4.3-22 depicts a situation where a backfilled pit cut has filled with water
until the water level reaches the elevation of the pit crest at its northern end.
At this point, the water will escape by a spring or seep. In actuality, the water
table may mound and somewhat exceed the pit crest elevation. The maximum poten-
tial extent of this mounding can be mathematically predicted.
A flow line passing from a more porous material (backfilled spoils) to a less por-
ous material (contiguous undisturbed geologic strata) will obey the law of inci-
dence and refraction given by:
K, tan a,
K tan a2
where K = gpd/ft.2
+ t +t++ +{+ F+
++ ++
} +++ ..
++ +
+a1 1+ }
+ + +
+ $}+ ++ +
+ +, +
K, > kz
Therefore, springs or seeps will only develop at .the north end of the pit cuts
where the recharge amount exceeds the conducting capacity of the high wall face.
7-8-82
4-98