PERMFILE44453

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

_ _ ._,
*, ~ III IIIIIIIIIIIII III
~ ` ]r -' `~F COLORADO
DIVISION OF MINERALS AND GEOLOGY
Depanmem of Natural Resources
1313 Sherman 51., Room 215
Denver, ColoraAo 80203
Phone~1303)866-3567
FAx: [phone]
January 16, 1998
To: Larry Oehler, James Stevens
From: James Dillie ~~;
Re: Review of the Parkdale Project Application, File No. M-97-054
I~~
DEPARTMENT OF
NATURAL
RESOURCES
Roy Romer
Governor
lames 5. Lochhead
Etecmive Director
Michael B. Long
Division Direc lur
At your request, 1 reviewed the revised (amended) permit application regarding stability of [he quarry
highwalls and the potential adverse affects of blasting activities on nearby structures.
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 [he
blasting activities will not adversely affect off-site structures.
The operator did not submit sufficient data [o 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 [o
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 Department 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), [he internal friction angle is 52.5 degrees and
granite density is 2.69 grants per cubic centintenter (about 167 pounds per cubic foot).
slope failure even under moderate pseudostatic conditions (moderate seismic event).
The operator used Galena Slope Stability software to determine factors of safety (FOS) for the highwalls.
Assumptions in the program input included a 0. l5 seismic coefficient. The minimum FOS reported by
the operator is 2.5. The Division, using SB-Slope software and the above noted data, calculated a
minimum FOS of 3.37 for [he 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 [he operator; the highwall
configuration, as proposed, will result in a long ternt stable rock face which has a low probability of
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 [o 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) front the blast to the structure and the maxintunt
explosive charge weight in pounds per 8 milisecond (ms) delay period.
After extensive testing, the Office of Surface Mining Reclamation and Enforcement (OSMRE)