2019-06-28_REVISION - M1977004 (9)

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Homestake Mining Company May 10,2019 Regular(112d)Operation Reclamation Permit Application Package In addition to the current network of inclinometers (198-1, 198-2, 198-3, IN-1, IN-2, and IN-3), older networks of inclinometers existed at Pitch Mine that were removed or destroyed during reclamation construction activities. These inclinometers include: • Inclinometers 194-1, 194-2, and 194-3 were installed by Golder, as reported by CNI (1995). A geologic cross section included in CNI (1995) (Drawing 01) shows the relative position of the inclinometers along a profile line (A-A') of the east wall slope. Maps showing the location of the inclinometers, records of inclinometer readings, and map showing the location of profile A-A' is not included in the copy of CNI (1995) reviewed for this assessment. A profile labeled A-A' is shown in CNI (1983) which extends from the North Pit lake northeast across the East Wall headscarp, but it is not clear if this is the same profile. Based on Drawing 01, Inclinometer 194-1 was installed on the lower half of the slope at a ground surface elevation of approximately10,650 ft to a depth of approximately 10,300 ft. Inclinometer 194-2 was installed on the upper half of the slope at a ground surface elevation of approximately 10,950 ft to an elevation of approximately 10,650 ft, and its position is included in the annual survey network as point 194-2 (See Table 3-3 and Drawing 3). Inclinometer 194-3 was installed near the crest of the slope at a ground surface elevation of approximately 11,090 ft to an elevation of approximately 10,790 ft. Records of inclinometer readings or documentation for when and why these inclinometers were abandoned were not encountered by BGC in any of the reports, records, and other documents reviewed as part of the study. • Inclinometers 1-1, 1-2, and 1-3 pre-date 194-1, 194-2, and 194-3. They were installed on the pre-mine topography of the North Pit's East Wall. Like 194-1, 194-2, and 194-3, their locations are not shown on maps reviewed as part of this analysis, but they are shown on the CNI (1995) profile (Drawing 01). Based on Drawing 01, Inclinometer 1-1 was installed near the crest of the slope at a ground surface elevation of approximately 11,090 ft to an elevation of approximately 10,680 ft. Inclinometer 1-2 was installed on the upper half of the slope at a ground surface elevation of approximately 11,000 ft to an elevation of approximately 10,700 ft. Inclinometer 1-3 was also installed on the upper half of the slope at a ground surface elevation of approximately 10,990 ft to an elevation of approximately 10,700 ft. Records of inclinometer readings or documentation for when and why these inclinometers were abandoned were not encountered by BGC in any of the reports, records, and other documents reviewed as part of the study. 3.4.2.3. Survey Point Network North Star Surveying Inc. (North Star) has periodically installed survey monitoring points at the Mine to monitor survey monument displacement and corresponding surficial ground movement. The current network of slope monitoring survey points includes a total number of 107 survey monuments established across the North Pit, South Pit, and IRD (Drawing 03). The survey monuments are constructed of rebar and fitted with labeled aluminum caps and are surveyed annually. This network was established in 1994 when 52 slope monitoring points were installed by Golder on the eastern slopes of the North and South Pits (AAI, 1999). These points replaced an older survey network that was installed and monitored while the mine was operating (HMC, EXHIBIT E-RULE 6.4.5(AMENDED RECLAMATION PLAN) Page 44 HOMESTAKE MINING COMPANY