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Homestake 2016 Geotechnical Observations <br />Pitch Reclamation Project Indian and Tie Camp Rock Dumps <br />2. Tie Camp Rock Dump <br />"10400 -10100" Level <br />Site -Description: The Tie Camp Rock Dump was regraded 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_ As described in the 2012 Annual Reclamation Report, grading was performed in <br />2012 on the second and third benches from the top of the rock dump to control rill erosion <br />due to the benches filling with silt_ <br />2016 Observations: Piezometer TC10375 monitors the Tie Camp Rock Dump. In 2016, the <br />maximum fluctuation was 6.01 feet between February and April, compared with a rise of 4.27 <br />feet between March and June 2015_ The average depth to water in 2016 was 167.5 feet bgs <br />compared with 168.4 feet in 2015 and 167.5 feet bgs in 2014. Maximum seasonal <br />fluctuations were higher in 2014 (91 feet), and 2008 (12.3 feet) when heavy snow pack was <br />observed. <br />Field observations indicate that the repairs performed in 1995 and grading in 2012 were <br />successful and only small areas of surfiicial instability were observed from 1996 through <br />2016. In 2017, the surface conditions of the rock dump will be monitored closely after the <br />spring snow melt, <br />3. Piezometers - 2016 General Comments <br />The water level behavior in the piezometers differs each year due to fluctuation in snow pack <br />and summer precipitation. As shown on Figures 4 and 5, the peak water levels in the rock <br />dump piezometers reflect the heavier snow pack in 2014 (31 inches) and approximately 25% <br />less in 2015 (23 inches) and 2016 (20 inches). In 2016, the water levels in the rock dumps <br />fell back by late summer compared with water levels in the previous 2 years that fell back to <br />the normal levels in late fall due to heavier than typical late summer rains. Overall, the 2016 <br />water levels are comparable to 2015 when compared with the 2014 water levels in all but <br />one piezometer measurement, but still show a maximum differential following snow melt. <br />The piezometers in both rock dumps will be monitored and evaluated closely in 2017 to <br />determine the cause and effect of seasonal spikes in the piezometric water levels, to observe <br />changes in surface features of the rock dumps, and make repairs as needed. There <br />continues to be no concern related to slope or foundation stability or elevated phreatic <br />surfaces in either the Indian or Tie Camp rock dumps. <br />Homestake Pitch Reclamation Project Page 5 <br />2016 Annual Geotechnical Report December 31, 2016 <br />M-1977-004HR 2016 AnnualGeotechnicalReportText Final.doc <br />