2016-07-25_HYDROLOGY - M1980244 - Laserfiche WebLink

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■ There is no obvious cracking, bulging, or active raveling in the angle of repose waste rock slope above the seepage area. There is also no cracking that can be attributed to seepage-related instability on the platforms above the seepage area. ■ Waste rock exposed along the toe of the angle of repose outslope at the seepage areas is blocky and durable; some segregation occurred during placement, and waste rock along the base of the WRF is coarse and clean (free of fines). Seepage that exits at the toe of the waste dump is likely flowing freely through this coarse rock zone at the base of the waste dump. The seepage observed in this area is clear. ■ As observed along the crest of the seepage collection trench,there are no indications of displacement between the waste rock and the native foundation occurring at the toe of the waste dump. ■ No seepage is occurring from the waste rock higher up on the waste dump outslopes. ■ Topographic surfaces were generated for each LiDAR scan, and the surfaces were compared for relative displacements. The LiDAR scan area is shown in Figure 3. One method of comparison involved cutting profiles at the same locations on separate scans, and overlaying the profiles. As an example, Figure 4 shows profiles for the June 2 and July 7 topographic surfaces at location A-A'. There is no material difference between these profiles, indicating no displacement in the waste dump surface between these dates.This exercise was repeated for sections every 50 feet,for a total slope length of 500 feet, centered on the seepage area. Results for the other sections also indicated no material differences between the profiles. Slope Stability Analyses Slope stability analyses completed for permitting included an assumption that the waste rock, and the native materials immediately below the waste rock in the foundation were drained (i.e.,groundwater surface"deep" in the foundation,with no impact to waste dump stability).