REP01185

• Permit No: C1981018
• IBM Index Class Name: Report
• Doc Date: 12/16/1987
• Doc Name: INTERIM SUBSIDENCE MONITORING REPORT DESERADO MINE RANGELY COLORADO
• From: MLRD
• To: TOM GILLIS
• Permit Index Doc Type: SUBSIDENCE REPORT
• Media Type: D
• Archive: No

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STATE OF COLORADO

Roy Romer, Gove
DEPARTMENT OF NATURAL RESOURCES
MINED LAND RECLAMATION DIVISION
FRED R. BANTA, Director
DATE: December 16, 1987
T0: Tom Gillis (~
FROM: Jim Pendleton ~ / ,~.~~"'~'~--~
RE: "Interim Sub ence itoring Report, Deserado Mine,
Rangely, or
As you requested, I have completed a review of the above referenced report.
This report, prepared by Ruth Stinson, consultant to Western Fuels-Utah, Inc.,
presents the interim results of the aerial photographic subsidence monitoring
program underway at the Deserado Mine.
The report is clear and concise. An initial aerial photographic survey was
performed before mining had occurred in longwalled panel LW-1, in September,
1986. A grid control survey was completed for 20 monuments located within and
adjoining the areas of anticipated subsidence. Follow-up aerial photographic
and ground control surveys have been performed during May and September of
1987.
The report contains a number of significant observations concerning the
magnitude and character of subsidence observed above panel LW-1. The maximum
subsidence detected during the May survey was 4.32 feet, near the east end of
the panel within the area of least overburden thickness. Immediately above
the working face less than 0.5 foot of subsidence was measured in May. Within
400 feet from the working face, over the mined-out panel area, 4 feet of
subsidence was detected. Subsidence tapers to near zero at approximately
200 feet outside the mined panel's boundaries. The September, 1987 survey
determined that only minor residual subsidence had occurred in the six months
following the May survey, averaging less than 0.5 foot.
Ground control surveys were performed for 20 monument points within and
adjacent to the area of potential subsidence, in order to verify the accuracy
of the aerial photographic monitoring technique. Nineteen of those monuments
(95~) were accurate to within +/- 0.15 feet. One point (5~) was accurate to
within 0.26 feet. This accuracy is well within the original required accuracy
.specifications placed upon the permit approval by the Division.
The subsidence prediction included within the permit documents projected a
maximum vertical subsidence above longwall panel' LW-1 of 6.4 feet. The
maximum subsidence detected to date by the monitoring program is 5.5 feet.
Subsidence had been projected to extend approximately 400 feet outside the
mined panel boundaries. The actual limits of subsidence have been found to
extend less than 200 feet from the mined panel boundaries.
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423 Centennial Building, 1313 Sherman Street Denver, Colorado 80203-2273 Tel. [phone]