REP26798

• Permit No: C1980007
• IBM Index Class Name: Report
• Doc Date: 3/1/1981
• Doc Name: REPORT PRELIMINARY DESIGN RECOMMENDATIONS INITIAL WASTE ROCK PILE MT GUNNISON COAL MINE SOMERSET CO
• Permit Index Doc Type: STABILITY REPORT
• Media Type: D
• Archive: No

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The site lies in a Zone 1 area of the seismic risk map
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corresponds to possible minor damage and corresponds to in-
' tensities V and VI on the Modified Mercalli intensity scale.
It was estimated by Donovan et al (1976) that an effective
' peak acceleration of about 0.05 g has a 90 percent probability
of not being exceeded during a 50 year period. Under these
conditions, a design acceleration of 0.05 g appears to be
reasonable. A horizontal earthquake acceleration of 0.1 g
appears to be unrealistically severe.
Safety factors remain substantially above 1.0 for all
' compositions of waste pile constructed at 1 (v) 2.25 (h),
even under earthquake loadings which are considered un-
' realistically severe.
' Based on the results of our stability analyses, our
knowledge of the type of material which is expected to be
t incorporated into the pile, the conservative values of shear
strength parameters used, and the character and location of
the pile, we consider that a tentative design slope of 1.0
2
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e at ~
(v) 2.
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this time. This slope angle should be reviewed subsequent to
' the additional geotechnical and ground water monitoring,
sampling, and testing. It should also be reviewed after the
composition of the pile is more accurately established. '

4.2 PILE CONFIGURATION

The width of the base of the waste rock storage pile will
not exceed approximately 200 feet due to space limitations at
the storage area site. Since the recommended slope angle for
the pile is less than 1.0 (v) 2.0 (h), the height of the
'

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