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1 <br /> Homestake Mining Company 2018 Geotechnical Observations <br /> Pitch Reclamation Project Indian and Tie Camp Rock Dumps <br /> Indian Rock Dump Inclinometer Installation <br /> Three inclinometers (IN-1, IN-2, and IN-3) were installed in August 2017 along a drainage <br /> ditch located approximately halfway between the 10000 level and the 10300-bench (Figure <br /> 2). The IN-1, IN-2, and IN-3 boreholes were advanced through waste rock into native <br /> ground to total depths of 63,138.5, and 25 feet below ground surface, respectively. The <br /> construction of inclinometers was completed using Slope Indicator®(SI) QC slotted casing. <br /> ' The borehole annulus was backfilled with 10/20 sized silica sand. <br /> Inclinometer readings were collected prior to and during operation of the Indian Rock Dump <br /> ' phosphate injection system (June through September). The data did not indicate any slope <br /> movement in this area related to the 2018 injection program (BGC 2019). <br /> "10370-10400" Level <br /> rSite Description: Identical to that of past reports for 1996 through 2017. <br /> 2018 Observations: The water level in Piezometer IC1037OR dropped by 2 feet in 2018 <br /> ' during the high-flow sampling event compared to the 2017 event. The water level also <br /> dropped in comparison to the low-flow sampling event in 2017, this time by approximately <br /> 6.5 feet. The lower water levels during both 2018 monitoring events can be attributed to the <br /> low levels of winter snow pack and low amounts of precipitation during the summer and fall. <br /> Piezometer IC10360 is also near Piezometer 10370R but does not intersect the Indian <br /> drainage. During high-flow and low-flow sampling an obstruction was encountered at <br /> approximately 155 feet below the well collar. IC10360 will be inspected in 2019 when site <br /> access is feasible. <br /> "10400-10600" Level <br /> Site Description: Identical to that of past reports for 1996 through 2017. <br /> 2018 Observations: Piezometer IC10440 was used to monitor subsurface water levels in <br /> this area of the rock dump until it became non-functional in 1996. Piezometer IC10525, <br /> which is also representative of this area of the rock dump, is described below in Section <br /> "10525— 10725" Level. <br /> 10600-10650"Level <br /> Site Description: Identical to that of past reports for 1996 through 2017. <br /> 2018 Observations: Piezometers IC10630 and IC10600 monitor subsurface water in this <br /> area of the Indian Rock Dump. The water elevation in Piezometer IC10630 rose by 15 feet <br /> during high-flow in 2018, which is consistent with rising levels measured from 2014 through <br /> ' 2017 (Figure 3). During low-flow monitoring, the water level was 1.6 feet higher in 2018, <br /> within the range of historical minimum and maximum measurements. <br /> As noted in previous reports, in October 2001, an obstruction was removed from Piezometer <br /> ' IC10600, which subsequently allowed it to be used for the collection of water level data. In <br /> 2018, the water level in Piezometer IC10600 lowered by 6.5 feet from the high-flow level in <br /> 2017. This measurement is within the range of historical minimum and maximum <br /> ' measurements. During the low-flow event in 2018 the water level was less than a foot lower <br /> than in 2017, consistent with other piezometers due to the low levels of precipitation during <br /> the summer months. <br /> Pitch Reclamation Project Page 4 <br /> 2018 Annual Geotechnical Report <br /> M-1977-004HR <br />