2008-06-09_HYDROLOGY - C1996083

• Permit No: C1996083
• IBM Index Class Name: Hydrology
• Doc Date: 6/9/2008
• Doc Name: Stability Analysis of Hubbard Shaft Mud Pit
• From: J.E. Stover & Associates Inc
• To: DRMS
• Permit Index Doc Type: Prof Pond Certifications
• Email Name: JJD
• Media Type: D
• Archive: No

VA Yeh and 1
Consulting Engineers &
May 29, 2008
Mr. Collin Stewart, P.E.
Bowie Resources, Limited
P.O. Box 1488
Paonia, Colorado 81428
Inc.
Project No. 28-024B
Subject: Subsurface Investigation, Mud Pit Embankment, Hubbard Creek Shaft at Bowie
#2 Mine, Paonia, Colorado
Dear Mr. Stewart,
This report presents Yeh and Associates, Inc. subsurface investigation of the mud pit
embankment for temporary containment of drill fluid and spoils at the Hubbard Creek Shaft site
for the Bowie #2 Mine near 'Paonia, Colorado. Our scope consisted of a subsurface
investigation of the existing embankment and included drilling of exploratory borings along the
crest of the embankment, site reconnaissance and laboratory testing.
PROJECT DESCRIPTION
A mud pit was constructed at the Hubbard Creek Shaft site. Plans provided indicated a
pit volume of 1,467 cubic yards and a berm height of around 10 feet. Plans also indicated a
steep face or roadside profile with grades slightly steeper than 0.5H:1 V. Mud pit side profiles
indicated more gentle grades between 1.5H:1 V and 2H:1 V. The mud pit will be lined, and plans
indicated a maximum fluid level within 3-foot of the crest.
PURPOSE AND SCOPE
The purpose of our investigation was to explore and evaluate subsurface conditions of
the existing embankment materials.
Yeh and Associates' scope of services included:
• The drilling of exploratory, borings on top of the existing embankment.
Laboratory testing of selected samples obtained during the field exploration to evaluate
relevant physical and engineering properties of the soil.
SUBSURFACE CONDITIONS
Two test holes were drilled along the crest of the existing embankment. Subsoils
encountered consisted of silty, clayey fill underlain with sandy clay and clayey sand interlayered
with sandstone bedrock fragments (Figure 1). Fill depths encountered were 7 and 5 feet in
borings TH-1 and TH-2, respectively. Fill samples tested had 7 to 34 percent fines (material
passing the No. 200 sieve). Atterberg limit testing on the fill samples exhibited liquid limits of
non-liquid to 31 percent and plasticity indices of non-plastic to 15 percent. One natural clay
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