2011-02-14_PERMIT FILE - C1980007A ‎(3)‎

• Permit No: C1980007A
• IBM Index Class Name: Permit File
• Doc Date: 2/14/2011
• Doc Name: SUBSIDENCE EVALUATION
• Section_Exhibit Name: Exhibit 60E Subsidence Evaluation for the South of Divide and Dry Fork Mining Areas
• Media Type: D
• Archive: Yes

Subsidence Evaluation for the
Exhibit 80E South of Divide and Dry Fork Mining Areas Page 30
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11.0 EFFECTS OF SUBSIDENCE AND MINE - INDUCED SEISMIC
ACTIVITY ON MAN -MADE STRUCTURES AND RENEWABLE
RESOURCES
Man -made structures and renewable resources in the South of Divide mining area basically
consist of 1) a reservoir (Minnesota Reservoir), 2) stock watering ponds, 3) streams (primarily
Dry Fork and the upper part of Lick Creek) and Deep Creek Ditch, 4) roads, and 5) local cabins.
Minnesota Reservoir, the ponds, and the Deep Creek Ditch diversion to Dry Fork serve the dual
purpose of being both man -made structures and containment structures for the valuable water
resources in the area. Based on annual subsidence observations in the Jumbo Mountain, Apache
Rocks, and Box Canyon mining areas since 1996, the following information is considered
appropriate for the South of Divide and Dry Fork mining areas.
11.1 Minnesota Reservoir
Minnesota Reservoir, which provides storage water primarily for irrigation, is located between
two landslides —one beginning at the north shore and the other beginning at the south shore. As
explained in Section 10.1.1 (above), landslide movement on Jumbo Mountain occurred during
unusually wet periods before mining began, during mining, and after mining and subsidence was
complete. The conclusions were that landslide movement occurs in response to ground
saturation and is not noticeably affected by subsidence and seismic activity produced by
longwall mining beneath, or near, landslide areas.
Both the landslides on Jumbo Mountain and those north and south of Minnesota Reservoir occur
in surficial material (loose rock, gravel, sand, silt, clay, and soil) and local bedrock outcrops.
Dunrud therefore expects that the mining of longwall panel E9 will not noticeably affect the
large landslide south of Minnesota Reservoir.
Mining of the nine longwall mining panels in the South of Divide and Dry Fork mining areas, as
currently planned (Map 1) will not affect Minnesota Reservoir. The reservoir is located outside
the area of mining influence, using an extremely conservative 45- degree angle of draw.
In order to verify and demonstrate the accuracy of predictions, based on the results of past
subsidence observations in the Apache Rocks and Box Canyon mining areas, three procedures
were implemented to monitor this structure prior to mining.
1. Conduct periodic aerial photo surveys of the landslides located north and south of the
reservoir, using the July 2004 photos as a baseline reference.
2. Install, and periodically measure, survey monuments strategically located on the dam and
on the north and south edges of the reservoir to monitor any movement prior to, during,
and after mining in the area.
3. Install seismometers in strategic places, such as in the dam area and toe areas of the
landslides, in order to detect vertical and horizontal ground motion prior to, during, and
. after mining, particularly during the mining of E -seam longwall panel E9.
831 - 032.810 Wright Water Engineers, Inc.