PERMFILE105259

• Permit No: M1997054
• IBM Index Class Name: Permit File
• Doc Date: 1/16/1998
• Doc Name: REVIEW OF THE PARKDALE PROJECT APPLICATIONS FN M-97-054
• From: DMG
• To: LARRY OEHLER JAMES STEVENS
• Media Type: D
• Archive: No

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DIVISION OF MINERALS AND GEOLOGY
Department of Natural Resources
1 313 Sherman St., Room 215
Denver. Cobrado 80203
Pfione. 1}p3f 8663567
FA\: 1703) 832-8106
January 16, 1998
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DEPARTMENT OF
NATURAL
RESOURCES
Roy Ramey
Governor
From: lames Dillie ~ ~~,
dames 5 Lochhead
E>,ecutive D~reclar
Re: Review of the Parkdale Project Application, File No. M-97-054 Michael B. Long
Division Direaur
At your request, I reviewed the revised (amended) permit application regarding stability of the quarry
highwalls and the potential adverse affects of blasting activities on nearby structures.
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OF COLORADO
To: Larry Oehler, James Stevens
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Pursuant to the requirements of Rule 6.5, the operator is required to submit sufficient documentation
(engineering analyses, etc.) to demonstrate to the Division's satisfaction that the mined highwalls will not
experience slope failure during, or after, cessation of mining and reclamation activities, and that the
blasting activities will not adversely affect off-site structures.
The operator did not submit sufficient data to complete a thorough evaluation of highwall stability or
adverse blasting effects in the original application. The revised application, however, contains sufficient
engineering data to adequately complete a thorough stability analysis of the quarry highwalls and to
estimate potential adverse affects of blasting.
The operator collected two samples of unweathered granite within the proposed quarry area. The
samples were sent to the Depattment of Mining Engineering, Colorado School of Mines in Golden,
Colorado where they were prepared and tested for various rock properties including; density, confined
and unconfined compressive strength, cohesion and internal friction angle. Cohesion was determined to
be 475 kPa (equal to 9,792 pounds per square foot), the internal friction angle is 52.5 degrees and
granite density is 2.69 grams per cubic centimen[er (about 167 pounds per cubic foot).
The operator used Galena Slope Stability software to determine factors of safety (FOS) for the highwalls.
Assumptions in the program input included a 0.15 seismic coefficient. The minimum FOS reported by
the opera[oris 2.5. The Division, using SB-Slope software and the above noted data, calculated a
minimum FOS of 3.37 for the overall highwall slope and 8.09 for each mined bench. The higher the
FOS the less likely a slope failure will occur. The Division concurs with the operator; the highwall
configuration, as proposed, will result in a long term stable rock face which has a low probability of
slope failure even under moderate pseudostatic conditions (moderate seismic event).
The operator submitted sufficient data to demonstrate to the Division's satisfaction that blasting activities
will not adversely affect off-site areas. As originally proposed, the operator chose to use scaled distance
formulas to establish safe ground motion and airblast conditions at the site. The scaled distance (Ds) is a
fundamental relationship between distance (in feet) from the blast to [he structure and the maximum
explosive charge weight in pounds per 8 milisecond (ms) delay period.
After extensive testing, the Office of Surface Mining Reclamation and Enforcement (OSMRE)