PERMFILE41795

• Permit No: M1980244
• IBM Index Class Name: Permit File
• Doc Date: 8/1/2005
• Doc Name: geotechnical analyses
• From: cripple creek and victor gold mining company
• To: dmg
• Media Type: D
• Archive: No

Cripple Creek & Victor Gold Mining Company July 21, 2005
Timm C. Comer -2- 053-2399
Project Background
The SGOSA facility is situated within the upper reaches of Squaw Gulch, a natural ephemeral
drainage. The gulch is characterized as being a "v" shaped drainage valley with side-slopes ranging
from 20 to 30 degrees. The bottom of the valley is relatively flat with grades between 1 and 5 percent.
Groundwater within the confines of the gulch is non-existent as the entire area is drained by historic
mine drainage tunnels and ancillary historic underground mine workings.
In early February 2005 CC&V mine personnel observed surface cracks developing along the crest of
the SGOSA. As a result of these observations, the crest area of the SGOSA was temporarily closed to
haul truck traffic and- surface prisms and extensometers were established to monitor movements.
Figure 1 presents a plan map showing the SGOSA facility, location of surface prisms, extensometers,
and surface cracks.
Site visits were conducted by Golder persotmel (geotechnical engineers) on March 3~ and March 24~'
to visually inspect the surface cracks and general condition of the facility. Photographs from the
Mazch 24'" inspection are presented in Appendix A. The results from the site inspections indicated
that the SGOSA facility was in a stable condition. The observed surface cracking was considered a
normal response to settlement of the thick overburden fill placed at angle of repose slopes. The
observed surface cracks were curvilinear and generally parallel to the current crest of the SGOSA
facility. No signs of distress or bulging were noted along the toe of the SGOSA facility.
GEOTECHNICAL ANALYSES
Geotechnical analyses were conducted for the SGOSA to confirm the observed conditions at the
facility. The analyses included an evaluation of the surface prism data, a slope stability analysis of the
current SGOSA confie ration, and a settlement analysis. The results of these analyses are presented
in the following sections.
Data Evaluation
The SGOSA data that was provided to Golder by CC&V included:
• Site surface topography maps showing the location of surface cracking; and
• Site survey-data from-nine prisms located on the surface of the SGOSA facility.
Figure 2 shows the total displacement vectors from prisms D4-[ through D4-9 along with the mapped
surface cracks. The displacement vectors were calculated as:
V=,IDXZ+~YZ+pZ
The vectors were then normalized and plotted in Figure 2, with the maximum displacement oF5.9 feet
occurring at prism D4-3. The total displacement vectors show movement of the SGOSA converging
along [he primary axis of Squaw Gulch. The calculated vertical strain at the prism locations ranges
between 0.1 to 1.1 percent. Overall, this pattern of movement and surface cracking is considered
typical for self-weight settlement of uncompacted fill.
i^OSVi99~0a00~SGOSd S~abErelOT_105',OSi2i99.MWRCpdoc Golder Associates