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

• Predicted Subsidence-Related Phenomena and Material Damage Which Would
Occur as a Result of Subsidence - 2.05.6 (6)(b)(i)(B&C)
Predicted subsidence impacts for the mining azea have been described in detail in the following
section entitled "Subsidence Prediction" 2.05.6 (6)(e)(i). Given the magnitude of the subsidence
projected in the above referenced section, the following outlines the material damage which could
result as a consequence of the projected subsidence.
Structures in the permit azea are described in Section 2.05.6 (6)(a)(i & ii). The discussions in
Section 2.05-6(6)(e)(ii)(A-C) and Section 2.05.6(6)(f)(iv)(A-D) include the "worse possible
consequence" to these structures, as well as mitigation commitments. There are no buildings
located in the Apache Rocks and Box Canyon permit revision areas.
There aze 13 stock ponds in or near the Apache Rocks permit revision azea and only one stock pond
in the Box Canyon-permit revision area. The stock pond embapkments aze not expected to be
impacted, however, the ponds will be monitored and any subsidence impacts mitigated by MCC per
the USFS agreement letter in Exhibit 19C.
The most significant surface impacts are expected to occur alonglthe precipitous slopes and cliffs
immediately north of the Minnesota Reservoir, along the flanks of West Flatiron, and in those azeas
within the influence of longwall mining where the overburden thickness is less than 400 feet. The
areas with overburden less than 400 feet include reaches of Gribble Gulch and Horse Gulch. The
minimum overburden thickness above mining in the Box Canyon permit revision azea is 500 feet.
In all of these azeas, the most severe hydrologic scenarios are as follows:
As discussed in Section 2.05.6, Depth of Surface (Tension) Cracks, development of cracks
as much as 200 feet deep above the chain and barrier pillars could divert intermittent surface
and/or spring flow into the more impermeable rocks in the overburden. The probability of
such surface cracks occurring is very small. For example, based upon MCC mining of
longwall panels to date, only a few surface cracks have been observed that aze considered to
be solely related to B-Seam mining. As discussed later, there are many "healing" and
"sealing" mechanisms that act to close surface cracks.
In the event that a surface crack opens and stays open, surface and spring flows that
encounter relatively permeable zones in the overburden will move downgradient and
reemerge as springs with subsequent discharge into either the Dry Fork or the North Fork.
WWE and Messrs. Rold and Dunrud have determined thafthere is virtually no potential for
a surface crack in the permit area to be deep enough to connect with a mine fracture zone.
In the extremely unlikely scenario in which this occurs, however, the implications would be
minor. If this scenario were to happen to the south of the drainage divide (in the Dry Fork
basin) the surface and/or spring flows would be dischargedi into the mine workings. Waters
collected within the mine workings would be treated, if necessary, to comply with the
• National Pollution Dischazge Elimination System (NPDES) pemut requirements and
pumped through a drill hole back into the Dry Fork basin, as specified in the water
2.05-IOS RevisedJurt. 1995 PR06; //96 RN03; Revised Nov. 1998 TR80; IN8 PR08;March 2005PR/1 ''^ !
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