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Homestake 2006 Geotechnical Observations <br />Pitch Reclamation Project Indian Creek and Tie Camp Creek Waste Rock Dumps <br />localized areas of slope instability were noted, corrected, and reported in the 1995 <br />Annual Geotechnical Report. <br />2006 Observations: Visual observations indicate that the repairs performed in 1995 were <br />successful and no new azeas of surficial instability (slips) were observed from 1996 through <br />2006. Piezometer TC10375 monitors the Tie Camp Creek Waste Rock Dump. In 2006, <br />water levels averaged 170.5 feet bgs, with a maximum observed seasonal fluctuafion of 7.3 <br />feet in June. This was the greatest water level fluctuation since the repair work was <br />completed in 1995. The water level dropped back to its normal range the following month, <br />a condition similar to piezometers on the Indian Creek dump and deemed as an acceptable <br />seasonal variation. In 2007, we will continue to monitor closely the surface conditions of <br />the Tie Camp dump after the spring snow melt. <br />3. Piezometers - 2006 General Comments <br />The 2006 water level measurements continue to show the normal seasonal variations in the <br />depths to water (and therefore the thickness of the saturated zone at the base of the Waste <br />Rock Dumps). Following the dry conditions of 2001 through 2003, the seasonal variations <br />noted in 2006 were back in line with historic variations. The saturated zone under the <br />dumps remains thin and similaz to previous years. We will continue to evaluate the cause <br />and possible effects of the seasonal spikes in the water levels in some piezometers, and <br />observe surface features of the dumps. However, there continues to be no indication of <br />instability in either waste rock dump due to the phreatic levels. <br />Table 1: Pitch Project -Depth to Water in Waste Rock Dump Piezometers (feet below ground surface at collar (bgs)] <br />DATE 10630 10600 10525 10440 10370 10360 10300 TCi0375 <br />111312006 203.1 253.0 229.4 190.8 229.8 190.8 171.9 <br />211012006 203.2 253.0 229.4 190.8 230.2 190.9 172.1 <br />3/13/2006 203.2 253.0 229.4 190.9 230.7 191.0 172.1 <br />4/7/2006 203.0 252.6 227.3 190.9 231.3 191.1 173.1 <br />5/12/2006 202.9 251.5 222.9 190.2 220.5 182.4 165.8 <br />61912006 203.0 251.6 223.4 190.4 220.6 185.6 167.3 <br />7!1/2006 203.0 251.8 224.7 190.6 220.9 188.8 168.8 <br />812/2006 203.0 252.6 226.2 190.6 221.3 188.0 170.5 <br />9112/2006 203.1 252.7 226.8 190.7 222.1 188.8 170.8 <br />10110/2006 203.1 252.8 227.4 190.7 223.4 189.9 171.0 <br />1112812006 203.1 252.2 228.2 190.7 225.5 190.6 170.9 <br />12/14/06 203.1 252.8 228.9 190.7 226.1 190.8 171.7 <br />2006 Maximum <br />Differenlial <br />0.3 <br />1.5 <br />6.5 <br />0.7 <br />10.7 <br />8.7 <br />7.3 <br />Homestake Pitch Reclamation Project Page 3 <br />2006 Annual Geotechnical Report December 15, 2006 <br />M-1977-004HR 2006ReportText FINAL <br />