PERMFILE48770

• Permit No: M2004061
• IBM Index Class Name: Permit File
• Doc Date: 11/17/2004
• Doc Name: Adequacy of the Geotechnical Stability Exhibit
• From: DMG
• To: DMG
• Media Type: D
• Archive: No

STATE OF COLORADO
DIVISION OF MINERALS AND GEOLOGY f/
Department of Natural Resources
1313 Sherman St., Room 215
Denver, Colorado 80203
Phone: [phone]
FAX: [phone]

DATE: November 17, 2004
TO: / Kate Pickford
FROM: 1/ Allen Sorenson ~~

RE: Adequacy of the Geotechnical Stability Exhibit, Linke Construction Inc.,
Cottonwood Quarry, File No. M-2004-061
COLORADO
D C V I S I O N O E
MIN SRALS
GEOLOGY
REC LAM ATION•NIN ING
SAFETY•ECIENCE
Bill Owens
Governor
Russell George
Executive Director
Ronald W. Cattany
Division Director
Natural Resource Trustee
Ouarrv Blasting Considerations
A blasting analysis and recommendations prepared by Revey Associates, lrlc. is included in the
Geotechnical Stability Exhibit. The permit application refers to the Revey report as a "blasting plan," and
it is stated that the "blasting plan...will be followed by the operator." The DMG takes this statement to
mean that all of the recommendations in the Revey report will be followed by the operator, and will be
enforceable permit conditions. This is acceptable for all of the qualitative and most of the quantitative
recommendations contained in the Revey report. However, DMG will require that the operator
specifically commit to the following three conditions for blasting operations:
1. Maximum 1000 pound charge weight detonated per 8-millisecond delay. Required reevaluation of
blasting controls if structures are erected closer to the quarry than the current closest structure,
which is 3800 feet away.
2. Minimum drill hole stemming height equal to the sum of 15 drill hole diameters.
3. A record for each blasting event will be prepared and preserved by the operator, and will be
provided to the~MG within a reasomable time period~3ponziemand. -An example of a blasting
record form is attached to this memo. The blasting records prepazed by the operator must, at a
minimum, include all of the information contained in the example form, with the exception of the
seismic data and seismographic information. Since the operator has selected the scaled distance
equation method of compliance, measurements using a seismograph are not necessary at this site
at this time. In addition to the information from the example form, the operator must prepaze a
sketch to include with the record for each blast showing the blast pattern, including delays, and a
cross section of a typical loaded hole.
Highwall Stability
The permit application proposes to quarry the site into the ridge to the north of the starting point by
developing 40 foot wide by 40-foot high benches. Quarry bench development will progress to the north
finally leaving a total of ten benches at the end of the life of mine. There is some ambiguity in the permit
application that must be clarified prior to application approval. The language in the application, for the
most part, indicates that the 40'x 40' benching (overall slope of 1:1) will be maintained throughout the
life of the operation. However, the statement in Exhibit D, on page 9 of the application, that the "plan is
to mine that slopes at their final rate adjacent to any structure which will eliminate any chance that these
Office of Office of Colorado
Minced I and Rcrlamatinn Arlive and Inactive Mines Geolo¢ical $uNev