REP00888

• Permit No: C1996083
• IBM Index Class Name: Report
• Doc Date: 7/2/1999
• Doc Name: BOWIE 2 MINE GOB PILE STABILITY ANALYSIS NOV CV-99-004 PN C-96-083
• From: DMG
• To: JOE DUDASH
• Permit Index Doc Type: STABILITY REPORT
• Media Type: D
• Archive: No

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999
STATE OF COLORADO
DIVISION OF MINERALS AND GEOLOGY
Department of Nalurol Resources
131 3 Sherman $t., Room 215
Dem'er, Colorado 80203 DIVISION O F
Phone. [phone] MINERAL S
FAk: 1303)83?-81 U6 6c
GEOLOGY

DATE:
July 2, 1999 -- _- RECLAMATION
MINING•SA FETY
\
TO: Joe Dudash -, l Bill Owens
/
_- Governor
T
~ ~'I L Gres E. Walther
FROM: i
Jim Pendleton a E*ecunve Ducclor
_ ~ ~ At¢hael 8. Loos
Division Director
RE: Bowie No:~2 Nline. Gdb Pile Stability Analysis (re: NOV CV-99-004)
` --(Permit No: C-96-083)
I have reviewed the study report submitted by Jim Stover, P.E., consultant to Bowie Resource
Limited (BRL) for their Bowie No. 2 Mine. This study was prepared by Norm Johnston, P.E. of
Lambert & Associates. Inc., subcontractor to Mr. Stover for BRL. This study was prepared to
fulfill one of the abatement requirements placed upon NOV CV-99-004.
In response to your earlier request for verification of compaction achieved within the lowest 20
feet of the GOB pile, Mr. Stover submitted a proposed methodology prepared by Mr. Johnston of
Lambert & Associates last December. Norm Johnston recommended sampling the density of the
in-place lowermost twenty feet of GOB material, which was previously untested, using thin-
walled shelby tubes and California split spoon samplers. This study was performed in
compliance with [he proposed methodology submitted by Mr. Johnson and submitted to the
Division in February of this year. The material densities determined to exist during the earlier
study were used to determine the appropriate remolded densities to test in developing material
strengths for use in completion of this stability analysis. As in the earlier study, I concur with
Mr. Johnston's methodology.
Lambert & Associates report is brief but straight forwazd. The report includes a brief text, a
typical cross section of the pile, and a summary of the stability analysis computer runs. The
analysis concludes that the pile does attain a slope stability static safety factor in excess of 1.5 if
several construction standards are observed:
(1) The surface diversion drainage system is maintained and the subsurface underdrains are
extended beneath the pile footprint as the pile grows upslope. Both of these conditions
were included within the approved plan and are required by regulation. Lambert &
Associates based it's selection of drained condition strength parameters and pore
pressures upon these assumptions.
(2) Lambert & Associates also based it's conclusions upon "...an intimate and competent
contact between the GOB fill material and the natural support material which include the