PERMFILE46063

• Permit No: C1982056
• IBM Index Class Name: Permit File
• Doc Date: 5/21/2004
• Section_Exhibit Name: Exhibit 07e-8 PR6 Railroad Evaluation Final Report
• Media Type: D
• Archive: No

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SubTerra, Inc. Twentymile Coal Company 6/19/2003
PR6 Rail Line Evaluation
1. Introduction
This report presents the results of our evaluation of subsidence along Union Pacific's Energy Spur
to the Twentymile Mine in Routt County, Colorado, due to mining in the Northem Mining District,
Panels 17 through 18 Right. SubTerra, Inc. previously prepared an evaluation of potential
subsidence impacts (SubTerra, Inc., 2000) due to mining Panels 12 through 16-Right; this
evaluation was submitted and permitted under PR5. Panels 12 through 14-Right have since been
extracted and Panel 15 will be started in 2003. Panel 15-Right will be the fourth of seven longwall
panels that have and will sequentially subside the Energy Spur in the Northern Mining District.
The actual and predicted cumulative effects of all seven longwall panels are presented in this
report for completeness.
The layout of the Northern Mining District in relation to the Energy Spur is shown in Figure 1. Coal
from the Twentymile mine is hauled down track along the Energy Spur across a mined out area in
the Eastem Mining District and then across the seven panels in the Northern Mining District. As it
crosses the last three panels (16-Right through 18-Right) it also crosses Fish Creek and its AVF.
As shown on Figure 1, crossings occur over Panels 17-Right and 18-Right. There are also iwo
areas over 16-Right and 18-Right where the Energy Spur is located on an embankment
immediately above Fish Creek.
1.1 Scope of Work
• The scope of work covered by this report includes evaluating the potential effects of subsidence
on the Energy Spur, outline planning for remediation associated with partial re-leveling of the track
during 15-Right and subsequent undermining, and a preliminary evaluation of the potential affects
of remediation on Fish Creek and its AVF. This work follows on from previous work covering
subsidence prediction, planning, and management of remedial activities when 9-Right, 8-Right, 7-
Right, and 6-Right in the Eastern Mining District and 12-Right, 13-Right, and 14-Right in the
Northern Mining District undermined the Energy Spur track.
Tasks included:
• Predicting subsidence due to 15-Right through 18-Right undermining of the track.
• Estimating the magnitude of subsidence effects on the Energy Spur track.
• Estimating the partial re-leveling requirements to maintain the track in a serviceable
condition for each phase of undermining. The criteria for serviceability were
determined from prior experience and discussions with Energy Spur personnel.
• Evaluating whether track re-elevation would require extending culverts that allow Fish
Creek to pass beneath the Energy Spur at two locations.
• Evaluating whether track re-elevation would require filling in Fish creek's AVF at two
locations where the track is located on an embankment immediately above the AVF.
Subsidence Prediction included extending the predictive model to include the new longwall panels,
especially the area including the Energy Spur track.
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