REP50830

• Permit No: C1996083
• IBM Index Class Name: Report
• Doc Date: 3/29/1999
• Doc Name: BOWIE 2 MINE GOB PILE GEOTECHNICAL FIELD & LAB STUDY PN C-96-083
• From: DMG
• To: JOE DUDASH
• Permit Index Doc Type: STABILITY REPORT
• Media Type: D
• Archive: No

STATE OF COLU1~vU
DIVISION OF MINERALS AND GEOLOGY
Departmem of Natural Resources
1313 Sherman St., Room 215
Denver, Colorado 80203
Phone: [phone]
FAY: (J03) 8328106
DATE: March 29, 1999

TO: Joe Dudash
1
v" ~-
FROM: Jim Pendleton
RE: Bowie No. ine G Pile - Geotechnical Field Sc Lab Study
rmit No: C-96-083)
DIVISION OF
MINERALS
GEOLOGY
RECLAMATION
MINING•SAFETY
Bill Owens
Governo.
Greg E Watcher
Ewecuove Director
Michael 8. Long
Division Director
I have reviewed the study report submitted by 1im 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 [o Mr. Stover for BRL. In response to your earlier
request for verification of compaction achieved within the lowest 20 Yeet 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 fee[ of GOB material, which was previously untested, using thin-walled shelby tubes and
California split spoon samplers. This study was performed in compliance with the proposed
methodology submitted by Mr. Johnson.
Lambert 6: Associates supervised the collection of samples in three bores within the Bowie #2
GOB pile. Samples were collected using thin-walled shelby tubes when possible, in order t~ I
minimize disturbance of the samples. When resistance proved too great for the relatively weak
shelby tubes, sample collection was completed using a thicker walled split barrel California
sampler. The thickness of the California barrel causes the sample to be more disturbed, which
can invalidate the density of the specimen. Lambert R Associates then completed laboratory
analysis of the collected specimens, including additional comparative Proctor analyses, and
finally prepared the report of the field and laboratory results.
Lambert & Associates report is brief but straight forward. The report includes a brief text, a
typical cross section of the pile, boring logs, Proctor analyses reports, and a tabular summvy of
the calculated density determinations (Figure 9). Borings #1 and #2, which are towards the back
of the pile penetrate a large upper thickness of properly certified GOB, and a portion of the
suspect lowermost 20 feet of GOB. Boring #3, located near the toe on the out slope of the GOB
pile, penetrates the lowermost 20.4 feet of GOB, the portion of the pile in question. As Figure 9
summarizes, the 7 tests completed in Boring #I and the 6 tests completed in Boring #2 each
determined the density of the GOB to exceed [he 90% relative compaction standard specification.
However. of the ten determinations completed within Boring #3, three were less than [he
specified 90% relative compaction (80%, 34% and 37%).