2008-04-15_REVISION - M1980244 ‎(195)‎

• Permit No: M1980244
• IBM Index Class Name: REVISION
• Doc Date: 4/15/2008
• Doc Name: VOL IV APP 7 Stability Evaluation for East Cresson & Squaw Gulch Overburden Storage Areas
• From: CC & V
• To: DRMS
• Type & Sequence: AM9
• Media Type: D
• Archive: No

`1~JC
SMITH WILLIAMS CONSULTANTS, INC.
2.0 Site Conditions
2.1 SGOSAE Foundation
The site conditions within the SGOSAE were investigated as part of previous Amendments to
MLRB Permit M-1980-244. The results of the site investigations are presented in CC&V (1998
and 2000) and Golder (1993). The data from the site investigations indicate that the SGOSAE
foundation is characterized as consisting of moderately dense, colluvial deposits ranging in
thickness from 0 to 15 feet, overlying competent bedrock. The colluvial materials generally
consist of gravel and sand in a silty clay matrix, classifying as GC, SC, ML, and SM under the
Unified Soil Classification System (USCS). In some areas, a thin (less than 6 inches) growth
media layer is present.
The SGOSAE foundation is mostly dry as the area is within the generally porous diatreme. The
SGOSA foundation contains numerous historic surface and underground mine workings;
however, the mine workings are not large enough to influence the global stability of the OSA.
In the location of the SGOSAE (see Figure 1), the natural foundation grades are approximately
15 to 28 percent.
2.2 ECOSA Foundation
The foundation of the ECOSA was investigated as part of the Phase 5 VLF extension by Smith
Williams and Water Management Consultants (2008). Site investigations within the ECOSA
area included excavation of 54 test pits and drilling 8 borings (which were completed as
piezometers).
Data from the site investigations indicate that the ECOSA foundation consists of approximately)
foot of growth media underlain with moderately dense clayey sands, clayey gravels, lean to fat
clays, and silty sands. These soils classify as GC, SC, CL, CH, and SM under the USCS. These
soils were underlain by fractured bedrock intercepted at depths ranging from 4 to over 20 feet.
No groundwater was encountered in any of the borings advanced in the ECOSA foundation.
There are only a few underground mine workings within the ECOSA. These workings are not
large enough to influence stability of the facility.
In the location of the ECOSA (see Figure 1), the natural foundation grades are approximately 10
to 15 percent.
S:IPROJECTS\1125C CC&V CRESSON OSA1H2 - DESIGN\OSA STABILITY FINAL REPORT V2.DOC 2