PERMFILE131380

• Permit No: C1981041A
• IBM Index Class Name: Permit File
• Doc Date: 6/16/2003
• Doc Name: TOC to Appendix 20-3
• Section_Exhibit Name: Tab 20 Subsidence Survey Monitoring & Control Plan
• Media Type: D
• Archive: Yes

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TABLE 4. Factors of safety for retreat pillars under and adjacent
to Ute Water Co. surface facilities.
3rd East Physical Properties (@ = 48.80; ~o 782 psi)
Depth Retreat Pillar Sizes (ft)
ft 12x80 14x80 I6x80 18x80
200 2.03 2.38 2.73 3.08
250 1.87 2.20 2.52 2.84
300 1.77 2.07 2.38 2.69
ALL Coal Physical Properties (~ = 47.2°; °~o = 783 psi)
200 1.92 2.25 ~ 2.58 2.91
250 I.76 2.07 2.37 2.68
300 1.66 1.94 2.23 2.52
20 x 80
3.43
3.17
3.00
3.24
2.99
2.81
Tributary area 50 x 100 ft.
Physical properties for O.to 1000 psi confinement.
Underlined values are for recommended pillar sizes at specified depths.