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Homestake Mining Company 2017 Geotechnical Observations <br /> ' Pitch Reclamation Project Indian and Tie Camp Rock Dumps <br /> ' through waste rock into native ground to total depths of 63,138.5, and 25 feet below ground <br /> surface, respectively. The construction of inclinometers was completed using Slope <br /> Indicator®(SI) QC slotted casing. The borehole annulus was backfilled with 10/20 sized <br /> silica sand. <br /> Inclinometer readings were periodically collected during operation of the Indian Rock Dump <br /> phosphate injection system (August through September 2017). No slope movement was <br /> detected during or following injections. <br /> 2. Tie Camp Rock Dump <br /> Similar to the Indian Rock Dump, the Tie Camp Rock Dump can be separated into bench <br /> levels corresponding to ground surface elevation. The Tie Camp Rock Dump was regraded <br /> in 1994 following procedures approved by the Division in Technical Revision #1 in February <br /> ' 1994. In 1995, localized areas of slope instability were corrected and reported in the 1995 <br /> Annual Geotechnical Report (HMC 1996). The Tie Camp Rock Dump has one piezometer <br /> at an elevation of 10,375 feet as discussed below. <br /> 10400-10100"Level <br /> Site Description: The Tie Camp Rock Dump was regraded in 1994 following procedures <br /> ' approved by the Division in February 1994. During 1995, minor, localized areas of slope <br /> instability were noted and corrected as summarized in the 1995 Annual Geotechnical Report <br /> (HMC 1996). Grading was performed in 2012 on the second and third benches from the top <br /> of the rock dump to control rill erosion due to the benches filling with silt. Field observations <br /> ' indicate that the repairs performed in 1995 and grading in 2012 were successful and only <br /> small areas of surficial instability were observed from 1996 through 2017. <br /> ' 2017 Observations: Piezometer TC10375 monitors subsurface water in the Tie Camp Rock <br /> Dump. In 2017, the maximum water level fluctuation was 4.3 feet(between March and <br /> June), after the spring freshet. This rise in water level is similar to what was observed in <br /> 2015 (4.3 feet) but lower than the 6.0 feet rise observed in 2016. These recent observations <br /> ' are below the seasonal fluctuations observed in 2014 (9.1 feet)when heavy snow pack was <br /> observed. <br /> REFERENCES <br /> Colorado Department of Natural Resources, Division of Reclamation, Mining, and Safety <br /> (Division). Pitch Project, Permit No. M-1977-004, Technical Revision (TR-8)Approval. <br /> Letter to Bill Ferdinand from Dustin Czapla. May. <br /> Division. 2017a. Pitch Project, Permit No. M-1977-004, Technical Revision (TR-8)Approval. <br /> Letter to Holton Burns from Dustin Czapla. April. <br /> Division. 2017b. Pitch Reclamation Project Colorado Division of Reclamation, Mining, and <br /> Safety Reclamation Permit No. M-77-004HR Technical Revision#8 Addendum. Verbal <br /> ' Approval provided by Dustin Czapla during 2017 Site Inspection. June. <br /> Homestake Mining Company (HMC). 1996. Annual Geotechnical Report. January. <br /> Pitch Reclamation Project Page 6 <br /> 2017 Annual Geotechnical Report <br /> M-1977-004HR <br />