2007-12-17_REPORT - M1977004

• Permit No: M1977004
• IBM Index Class Name: REPORT
• Doc Date: 12/17/2007
• Doc Name: 2007 annual geotechnical report
• From: Homestake
• To: DRMS
• Email Name: RCO
• Media Type: D
• Archive: No

Homestake
Pitch Reclamation Project
2007 Geotechnical Observations
Indian Creek and Tie Camp Creek Waste Rock Dumps
June. This rise was lower than the 2006 water level fluctuation of 7.4 feet. The 2006
reading was the greatest water level fluctuation since the repair work was completed in
1995. The water level began dropping back to its normal range the following month, a
condition similar to piezometers on the Indian Creek dump and deemed as an acceptable
seasonal variation. In 2007, we will continue to monitor closely the surface conditions of the
Tie Camp dump after the spring snow melt.
3. Piezometers - 2007General Comments
The 2007water level measurements continue to show the normal seasonal variations in the
depths to water (and therefore the thickness of the saturated zone at the base of the waste rock
dumps). Following the dry conditions of 2001 through 2003, the seasonal variations noted in
2007 were back in line with historic variations. The saturated zone under the dumps remains
thin and similar to previous years. Homestake will continue to evaluate the cause and possible
effects of the seasonal spikes in the water levels in some piezometers, and observe surface
features of the dumps. However, there continues to be no indication of instability in either of the
waste rock dump.
Table 1: Pitch Project - Depth to Water in Waste Rock Dump Piezometers [teet telow ground surtace at couar (bgsl]
DATE 10630 10600 10525 10440 10370 10360 10300 TC10375
Collar Elev. 10631.5 10603.8 11053.6 10440.0 10380.52 10373.4 10299.5 10373.0

1/9/2007
203.1
252.9
229.1
190.8
228.5
190.8 _
171.9
2112/2007 203.1 253.0 229.3 190.8 230.6 190.9 172.8
3/9/2007 203.2 253.0 229.4 190.8 231.7 191.0 173.0
4/4/2007 202.0 252.4 227.7 190.6 221.8 188.2 171.4
5/21/2007 202.0 243.6 220.3 ° 219.9 181.0 167,9
6/18/2007 202.1 247.6 221.6 220.4 185.4 169.2
7/20/2007 202.0 249.8 224.3 220.8 186.2 169.9
8/17/2007 202.0 252.1 225.8 ° 221.6 188.7 170.4
9/28/2007 202.0 252.7 226.7 ° 221.8 189.5 170.6
10/18/2007 202.0 252.7 228.2 ° 223.6 190.0 170.8
t 1 N 312007 202.0 252.2 228.6 224.3 190.3 170.8
12/11/2007 202.0 252.3 229.2 226.0 189.9 171.1
Avera a de th 202.3 251.2 229.1 190.7 224.3 188.5 170.8
2007Maximum
Differential
1.1 9.4
9.1
0.2 11.8
10.0
5.1
Homestake Pitch Reclamation Project Page 3
2007 Annual Geotechnical Report December 14, 2007
M•1977-004HR 2007ReportText .Final