REV98699

• Permit No: C1982056
• IBM Index Class Name: Revision
• Doc Date: 4/28/2000
• Doc Name: ADDITIONAL REVIEW OF ADEQUACY RESPONSES TWENTYMILE COAL CO FOIDEL CREEK MINE PN C-82-056 PR PR-05
• From: DMG
• To: JANET BINNS
• Type & Sequence: PR5
• Media Type: D
• Archive: No

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STATE OF COLORADO
DIVISION OF MINERALS AND GEOLOGY
Deparlmenl of Natural Resources
1313 Sherman 51., Room 215
Denver, Colorado 80203
Phone: [phone]
FAX: [phone]
Date: April 28, 2000
To: Janet Binns
From: Dan Hemande~
Re: Additional Review of Adequacy Responses, Twentymile Coal
Company, The Foidel Creek Mine, Permit No. C-82-056,
Permit Revision No. PR-05
DIVISION OF
MINERALS
GEOLOGY
RECLAMATION
MINING•SAFETY
Bill Owens
Governor
Greg E. Walther
Executive Dvector
Michael B. Long
Division Director
I have reviewed, at your request, TCC's April responses to questions 17-21 from DMG's adequacy
letter of March 7, 2000. The TCC responses were dated April 10, 2000.
17. This item has been adequately addressed.
18. This item has not been adequately addressed.
The Division believes it has been given insufficient information with regazd to how subsidence
monitoring of County Road 33 can be used to confirm the predicted amounts of maximum
horizontal and vertical longwall mining-related subsidence deflection that will occur in the
Northern Mining District.
TCC has indicated in its response to DMG adequacy item no. 17 (above) that the maximum
subsidence expected from longwall panel 12R is expected to occur somewhere north of the
longitudinal axis of Panel 12R (rather than directly over the panel axis), due to a northwestwazd
coal seam dip. As County Road 33 does not precisely overlie Pane] 12R's longitudinal axis,
however, but rather overlies Panel 12R south of [he panel's longitudinal axis, it would appear
that the amount of longwall subsidence that will be observed along the county road will be less
than the maximum amount of subsidence that is expected to be seen in Panel 12R.
In addition, while the location proposed for the easternmost subsidence monitoring point on
County Road 33 (1000' east of the Panel 12R start room) appears adequate (as the point is near
the longitudinal axis of Panel 12R), County Road 33 begins veering off to the south from the
panel's longitudinal axis at an angle of approximately ]0°. It therefore appears that the
subsidence values obtained from the monitoring of County Road 33 will need some degree of
correction or extrapolation [o determine maximum horizontal and vertical deflection values, to
account for the fact [hat the monitoring stations established along County Road 33 will not be
situated along Panel 12R's longitudinal axis. II does no[ appear that a discussion of this
correction or extrapolation has not been provided, however.