_REVISION - M1980244 ‎(23)‎

• Permit No: M1980244
• IBM Index Class Name: Revision
• Doc Name: Appendix N
• From: Cripple Creek & Victor Gold
• To: DMG
• Type & Sequence: AM8
• Media Type: D
• Archive: No

Golder Associates Inc.
44 Union Boulevard, Suite 300
Lakewood, CO USA 80228
Telephone [phone]
Faz [phone]
April 19, 2002
Cripple Creek & Victor Gold Mining Company
P.O. Box 191
1280 State Highway 67
Victor, Colorado 80860
Attention: Mr. Ron Roberts
RE: Fine Shaft Backfill Specification
Dear Ron:
Golder
~Assoc~tes
Our Ref: 003-2203
Golder Associates Tnc. (Golder) has prepared this letter to address two recent failing gradations for Fine
Shaft Backfill (FSB). Golder conducted the two gradation tests in question on Apri14, 2002 for FSB used
to backfill UG-494 and UG-456. The results of the gradation tests are attached to this letter. As shown, the
FSB gradation is within the Golder specifications for this material, with the exception of the No. 40 sieve.
The Golder FSB specification at the No. 40 sieve is 20 to 50 percent passing. The results from the two
gradation tests show that the percent passing the No. 40 sieve is 15 percent and 16 percent, respectively.
The FSB material is used as aggregate sowce in the cemented rockfill for remediation of underground
• workings, such as shafts and stopes. The original gradation was developed following the general criteria
for concrete aggregate developed by the Bureau of Reclamation and from ow experience with other
similar backfilling projects.
The results from the FSB gradations indicate a slight increase in the medium sand particle size over the
original Golder specifications. Tests conducted by the Bweau of Reclamation have shown that concrete
strength does not vary significantly with variations in percent of sand content. Golder considers the
variation of sand content of 5 percent (from 20 percent passing to 15 percent passing) at the No. 40 sieve
as minor. Therefore, Golder wilt accept the FSB gradations attached to this Letter as suitable material for
producing cemented rockfill.
Golder appreciates the ongoing opportunity to provide engineering services for the Cresson Project.
Please contact the undersigned with any questions.
Sincerely,
GOLDER ASSOCL4TES INC.
F. Lupo, Ph.D.,P.E.
Sr. Project Manager
JL/bc
Cc: Bob Nichols, Golder
Greg Eddy, Golder
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