REP34549

• Permit No: C1981047
• IBM Index Class Name: Report
• Doc Date: 9/3/1986
• Doc Name: QUARTERLY BENCH STABILITY MONITORING FILE NO C-81-047
• From: MLRD
• To: BLUE RIBBON COAL CO
• Permit Index Doc Type: STABILITY REPORT
• Media Type: D
• Archive: No

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DEPARTMENT OF NATURAL RESOURCES
David H. Getches, Executive Director
MINED LAND RECLAMATION DIVISION
DAVID C. SNELTON, Diroctor
Richard D. lemur
Governor
September 3, 1986
Larry M. Reschke, P.E.
Project Engineer
Blue Ribbon Coal Company
P.O. Box 1352
Palisade, Colorado 81526
Re: Quarterly Bench Stability Monitoring, File No. C-81-047
Dear Mr. Reschke:
A ~~.6\ ~e R- badr>-
Jim Pendleton, our geotechnical specialist, has reviewed your mine bench
stability results for the last month of the first quarter of 1986 and the
second quarter of 1986. Mr. Pendleton noted a discrepancy between the results
for March 27 and June 26 and has these comments. For the past several years
the monitoring reports have demonstrated normal consolidation, with the
settlement rate decreasing over time. This report documents movement at five
of the eight monuments. However, for the first time, four of these stations
appear to have undergone a rise of between .02 feet and .09 feet in
elevation. Two monuments which exhibit .09 feet of rise are installed along
the crest of the fill. Therefore, I doubt that these monuments are exhibiting
rise due to a rotational bench movement. The summer season eliminates the
possibility of a freeze/thaw problem. I suspect that an error entered the
surveying due to an inaccuracy in setting up on the control point, to some
movement of the control point, or to the establishment of a new control
network, necessitated by the reclamation activities at the Blue Ribbon Mine.
Because of the importance of verifying little or no movement within the
reclaimed mine bench Blue Ribbon Coal Company should investigate the survey
inaccuracy and resolve this matter by either a re-survey of the subsidence
monuments or a re-survey of the control points used in the original surveys
and adjust the measured elevations of the monuments, as needed, for the March
27 and June 26 results. The re-survey may be conducted at the same time as
the subsidence survey for the 3rd quarter, if this has not already been done.
If the 3rd quarter survey has already been done, then the 2nd quarter results
re-survey should be conducted prior to October 1 and results forwarded to the
Division as soon as possible.
423 Centennial Building, 1313 Sherman Street Denver, Colorado 80203 Tel. [phone]