REP11191

• Permit No: C1996083
• IBM Index Class Name: Report
• Doc Date: 11/10/1998
• Doc Name: BOWIE 2 MINE GOB PILE RESPONSE TO DIVISION ISSUES PN C-96-083
• From: DMG
• To: JOE DUDASH
• Permit Index Doc Type: STABILITY REPORT
• Media Type: D
• Archive: No

STATE OF COLUiv-~~v
DIVISION OF MINERALS AND GEOLOGY
Department of Natural Resources
1311 Sherman Si., Room 215
Denver, Colorado 80203
Phone: [phone]
FAX: (303)A32-8106
DATE: November 10, 1998
r~\
~I
TO: Joe Dudash
FROM: Jim Pendleton
RE.: Bowie No. the G Pile -Response to Division Issues
mit No: C-96-083)
~~~~~
DEPARTMENT OF
NATURAL
RESOURCES
Roy Romer
Governor
dames 5. Lochhead
Executive Director
Michael B. Lonp
Division Director
I have reviewed the response to comments letter submitted by Jim Stover, P.E., consultant to
Bowie Resource Limited (BRL) for their Bowie No. 2 Mine. In his September 28, 1998 letter,
Mr. Stover responds to issues forwarded by the Division on September 3, 1998.
Proctor Comparison (Item tk2)
Nonn Johnston, P.E. of Lambert & Associates, geotechnical consultant to BRL advised Mr.
Stover that there was no reason to be concerned with relative compaction results in excess of
100"/0. 1 concur that it is not uncommon to determine field densities of up to 1 15% of proctor
standards. however, in my experience, results which rouinely exceed 1 15% of the Proctor
optimum dry density are unlikely. Results exceeding 115% of optimum dry density suggest that
the Proctor was performed on a soil which is not representative of the material being tested. I do
not consider Mr. Stover's response adequate to resolve my concern stated irl our previous
adeyaucy letter.
1 reiterate my earlier recommendation [hat BRL be regwred to develop an acceptable
methodology for verifying that the proctor standard being applied during a compaction test is
appropriate for the materials being inspected. The brute force approach is to perform a proctor
analysis every time a compaction testing is performed. That approach is expensive and time
consuming, and normally unnecessary. Often, if concem exists on [he part of the engineer in
charge of the inspection, a sieve analysis may serve to determine mechanical similarity of the
standard and the tested specimen. If the materials are shown to be similar in gradation, fine
content, and visual constituency, [hey can be assumed to be representative. In some cases,
however, it materials aze variant because of source variation or amendment, numerous proctors
may need to be completed.
Another common cause of compaction test inaccuracy is failure to properly analyze the
constituency of the sample tested. Modern nuclear density testing standards are commonly
misapplied. The nucleaz probes measure the average density of a sphere approximately one foot