PERMFILE132325

• Permit No: C1996083
• IBM Index Class Name: Permit File
• Doc Date: 8/22/2003
• Doc Name: Section 9
• Section_Exhibit Name: Volume VII Geotechnical Studies
• Media Type: D
• Archive: No

J.E. Stover & Associates
Terracon Project No. 65995058
June 3, 1999
The boring data presented by Maxim and Lambert shows the subsurface soils at the locations
of the proposed facilities generally consists of lean clays with gravel. Based upon field
penetration testing, these clay soils have very stiff to hard consistency. The materials have
been described as having numerous gravel to cobble to boulder sized fragments of sandstone.
In the upper elevations of the project near the mine portal, the clay materials associated with
the ancient landslide appear to directly overly bedrock. Near Highway 133 at the south end of
the proposed surface facilities, the clays were encountered over deposits of sands and
gravels. The sand and gravel soils are apparently alluvial in origin associated with deposition
in the Gunnison River flood plain. Based upon field penetration testing of the sands and
gravels, these materials can be characterized as having dense to very dense relative density.
Geotechnical profiles for the stability analyses have been based upon boring data from the
referenced explorations of the site by others. For the proposed Transfer Bench, borings 10
and 11 completed by Lambert have been drilled at this location. Based upon subsurface
conditions logged in these test borings, supplemented by boring data shown in the Maxim
. reports, it appears that the clay soils extend to depths of approximately 75 to 85 feet beneath
the existing ground surface at the proposed location of this structure. Sandstone bedrock of
the Mesaverde formation is indicated by Maxim below the clay soils at these depths.
Groundwater was not encountered in the borings drilled to shallow depths for this structure.
For the proposed Coal Stockpile Pad, borings 2 through 5 completed by Lambert have been
drilled at this location. Based upon subsurface conditions logged in these test borings,
supplemented by boring data shown in the Maxim reports, it appears that the clay soils extend
to depths of approximately 15 to 28 feet beneath the existing ground surface at the proposed
location of this structure. Alluvial sand and gravel soils were generally encountered below
these depths in the test borings. Groundwater was not encountered in the borings drilled to
shallow depths for this structure.
Lambert apparently drilled no specific borings at the location of the proposed sedimentation
pond. Boring data is indicated by Maxim at Ponds C and B (i.e. borings 1 and 2). These
borings indicate zero to 30 feet of clay soils overlying the alluvial sands and gravels. However,
because of the surface elevations of these borings and the existing ground surface located at
the proposed pond site, we anticipate that subsurface conditions will consist of clay soils
overlying the sands and gravels beneath the downstream berm. Based upon proposed grades
and excavations, the sand and gravel stratum is anticipated to be exposed in a portion of the
. pond bottom and in the cut slope forming the inside northern face of the structure
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