PERMFILE72133

• Permit No: C1996083
• IBM Index Class Name: Permit File
• Doc Date: 5/12/2003
• Doc Name: Intro and Sections 1 thru 5 and 7 thru 8
• Section_Exhibit Name: Volume VII Geotechnical Studies
• Media Type: D
• Archive: No

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TECHNOLOGIES INC
October 10, 1996
96 Sourh Zuni Street
Denver, Colorado 80223-1292
Telephone: [phone]
Facsimae: 1303) 744-0210
Mr. Peter A. Stauch ~i ~ ~ ~' !, T ; i f t~3S
Momson Knudsen Corporation
7100 East Belleview Avenue, Suite 300
Englewood, Colorado 80111
Subject: Additional Geotechnical Study, Evaluation of the Stability of the Reclaimed
Slopes, Bowie No. 2 Mine, Bowie, Delta County, Colorado
Job No. 5002-60-2655.02
Dear Mr. Stauch
Introduction; At your request, we have conducted an additional geotechnical study of the
proposed reclaimed slopes for the purpose of determining the stability of the reclaimed slope
configurations and to provide recommendations regarding the restoration of the slopes to their
pre-mining configurations. The additional work was in accordance with our revised proposal,
dated August 13, 1996. This study was done in conjunction with other additional work related
to the surface facilities at the mine. Laboratory data from samples from the borings related to
the surface facilities as well as data from our Preliminary Geotechnical Study (Job No. 5002-60-
2655.01) was used in this study.
Site and Subsurface Conditions: As we understand the project one aspect of the reclamation
plan for the mined area will consist of returning the cut and fill slopes associated with the
surface facilities to their pre-construction configurations. Most of the substantial cut and fill
slopes were in the area of the proposed benches and these areas were the focal point of our
study. In general, the cut and fill slopes in these areas are at slopes of approximately 2H:1V,
while the original slopes were at inclinations of approximately 3H:1V. Two cuts were analyzed
for stability after reclamation. Tltese slopes are in the area of the stockpile bench (Section A-A)
and the portal bench (Section B-B). These areas were determined to have the largest cuts and
were therefor determined to represent the most critical slopes. The stability analysis was
conducted based upon the assumption that the reclaimed slopes would be constructed as
recommended in this letter.
As presented in our previous study, the predominant subsurface materials were described as
ancient landslide deposits of very stiff to hard, slightly moist, lean clay with gravel and scattered
to numerous small to very large rock fragments (CL-GC), overlying shale or interbedded
sandstone and shale or coal. In addition to the borings associated with the previous study, an
additional boring (8-24) was made in the area of the proposed fan bench. The subsurface
conditions encountered in this boring consisted of approximately 55 feet of lean clay with gravel
overlying interbedded sandstone and shale. Moisture content, density, particle size gradation
and Atterberg limits conducted on samples of the soil from Boring 24 were consistent with the
lean clay with gravel described in our original study.
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