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' Homestake Mining Company 2018 Geotechnical Observations <br /> Pitch Reclamation Project Indian and Tie Camp Rock Dumps <br /> 10525- 10725" Level <br /> Site Description: Identical to that of past reports for 1996 through 2017. The minor overlap <br /> between this level and other bench designations reflects the original bench configuration. <br /> 2018 Observations: Piezometers IC10600 and IC10525 are used to monitor subsurface <br /> water in this area. During the 2018 high-flow sampling event the water level in IC10525 <br /> increased by 2 feet compared to the 2017 event. Historically this location shows a rise in <br /> water level of 7 to 9 feet. The small rise in the water level during 2018 is attributed to the <br /> low levels of winter snow pack. The water level measurement during the 2018 low-flow <br /> ' event was consistent with the measurement in 2017. <br /> "10650- 10780" Level <br /> Site Description: Identical to that of past reports for 1996 through 2017. <br /> 2018 Observations: Visual inspection of the area revealed no evidence of settling or <br /> slumping of the rock dump material. The drainage channels are functioning as designed. No <br /> ' piezometers are in this area. <br /> "10800" Level <br /> ' Site Description: Identical to that of past reports for 1996 through 2017. <br /> 2018 Observations: Visual inspection of the area in 2018 revealed no evidence of settling or <br /> slumping of the rock dump material and the drainage channels are functioning as designed. <br /> The drainage on the western side of the upper portion of the Indian Rock Dump,just above <br /> the sericite stockpile, where the rock dump intersects native ground, underwent minor <br /> ' erosion prior to 2012. A low gradient diversion ditch, was built in 2012, allowing water from <br /> the channel to be diverted and dispersed at lower velocities. Boulders were placed above <br /> the steep section of the channel and rip-rap was placed below the boulders as energy <br /> dissipaters, such that flow velocities are reduced and sediment retention is enhanced. <br /> Observations in 2018 indicate that this repair continues to minimize erosion in this area. <br /> 2. Tie Camp Rock Dump <br /> Similar to Indian Rock Dump, the Tie Camp Rock Dump is separated into bench levels <br /> corresponding to ground surface elevation. The Tie Camp Rock Dump was regraded in <br /> 1994 following procedures approved by the Division in Technical Revision #1 in February <br /> 1994 (Division 1994). In 1995, localized areas of slope instability were corrected and <br /> reported in the 1995 Annual Geotechnical Report(HMC 1996). The Tie Camp Rock Dump <br /> ' has one piezometer at an elevation of 10,375 feet as discussed below. <br /> "10100-10400"Level <br /> ' Site Description: Identical to that of past reports for 1996 through 2017. <br /> 2018 Observations: Piezometer TC10375 monitors subsurface water in the Tie Camp Rock <br /> Dump. In 2018, the water level was 2.8 feet lower than 2017 during high-flow, due to less <br /> ' precipitation in early 2018 than early 2017. The water level measurement during low-flow <br /> monitoring in 2018 was 1.4 feet lower than low-flow in 2017, but the level remained <br /> consistent throughout 2018 (Figure 3). <br /> Pitch Reclamation Project Page 5 <br /> 2018 Annual Geotechnical Report <br /> M-1977-004HR <br /> 1 <br />