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Homestake 2015 Geotechnical Observations <br />Pitch Reclamation Project Indian Creek and Tie Camp Creek Rock Dumps <br />2. Tie Camp Rock Dump <br />a) "10400 - 10100" Level <br />Site Description: The Tie Camp Rock Dump was re -graded in 1994 following procedures <br />approved in the February 1994 Technical Revision. During 1995, minor, localized areas of <br />slope instability were noted, corrected, and reported in the 1995 Annual Geotechnical <br />Report. <br />2015 Observations: Piezometer TC10375 monitors the Tie Camp Rock Dump. In 2014, <br />water levels averaged 167.5 feet bgs, with a maximum observed seasonal fluctuation of 9.1 <br />feet between March and April. The maximum fluctuation was higher than the 2.4 feet <br />recorded in 2012, but well below the 2008 rise of 12.3 feet, when the site incurred heavy <br />snow pack. In 2015, the maximum fluctuation was 4.27 feet between March and June, with <br />an average depth to water from ground surface of 168.4 feet. The water level in December <br />was near the seasonal low having dropped by 3.9 feet by December. This is deemed a <br />normal and acceptable seasonal variation. <br />Field observations indicate that the repairs performed in 1995 were successful and no new <br />areas of surficial instability were observed from 1996 through 2015. In 2012, grading was <br />performed on the second and third benches from the top of the rock dump to control rill <br />erosion that had become apparent over the past couple of years due to the benches filling <br />with silt. This repair work was described in the 2012 Annual Reclamation Report. In 2016, <br />the surface conditions of the rock dump will be monitored closely after the spring snow melt. <br />3. Piezometers - 2015 General Comments <br />The water level behavior in the piezometer differs each year due to fluctuation in snow pack <br />and summer precipitation. As shown on Figures 3 & 4, the peak water levels in the rock <br />dump piezometers reflect the heavier snow packs of 2014 (32 inches) and approximately <br />25% less in 2015 (24 inches). The past two years the December water levels have not falling <br />back to seasonal lows due to heavier than typical late summer rains. Over all, the 2015 water <br />levels were lower than the 2014 water levels in all but one piezometer measurement, but still <br />showed a maximum differential following snow melt above the 2013 and 2012 <br />measurements. Following the dry conditions of 2001 through 2003, the seasonal variations <br />had increased in recent years as heavier snow packs had occurred, with 2012 being a <br />relatively dry year. The replacement of two piezometers in the Indian Waste Rock Dump in <br />2011 has alleviated siltation issues in monitoring the phreatic surface in the Indian Rock <br />Dump. We will continue to monitor and evaluate the cause and effect of any seasonal spikes <br />in the piezometric water levels, observe any changes in surface features of the rock dumps <br />and make repairs as needed. There continues to be no indication of concern related to slope <br />or foundation stability or elevated phreatic surfaces in either the Indian or Tie Camp Rock <br />Dumps. <br />Homestake Pitch Reclamation Project <br />2015 Annual Geotechnical Report <br />M -1977-004H R <br />Page 5 <br />January 9, 20165 <br />2015 AnnualGeotechnicalReportText_Final.doc <br />