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limited to 15% of the material placed per lift. This will help to ensure sufficient compaction of <br /> tailings is achieved. <br /> A large portion of the Revenue TSF is located in an active avalanche path. The avalanche paths <br /> that impact the site are shown on Map C-6. Due to the avalanche threat, grading and compaction <br /> of the lifts on the Revenue TSF is only performed during the summer and fall (i.e., June through <br /> November). Haul trucks will transport tailings or waste rock to the Atlas TSF during the winter <br /> months. The TSFs will be regraded into the necessary lifts each summer. <br /> Monitoring wells are placed on the north (downhill side) of each TSF as shown on Map G-1. <br /> These groundwater wells are sampled quarterly for field parameters and a water chemistry suite <br /> analysis. More detail about groundwater sampling may be found in Exhibits G and U. The results <br /> of these tests and their evaluation will be incorporated in the DRMS Annual Report. Also, <br /> sample test data from any sediment pond discharges associated with the Atlas TSF will be <br /> evaluated in the Stormwater Annual Report. <br /> Dozers will compact the tailings/waste rock in 12" lifts to a 94%maximum dry density. A <br /> secondary compactor will be used, if needed to achieve the proper compaction. Quality control <br /> density samples of the compacted materials will be conducted using a field density instrument <br /> every 100 tons of tailings that are placed. As described in the Mine Plan and the Reclamation <br /> Plan (Exhibit E),the piles are graded to slopes that are no steeper than 3H:IV. A slope stability <br /> analysis of the worst-case tailings pile was performed as part of the Amendment 1 application. A <br /> copy of this analysis also was provided as Attachment 3 to TR-15. <br /> Based on the apparent stability of the existing un-reclaimed waste rock pile slopes in the area, a <br /> detailed slope stability analysis was not performed on this material under the original design. <br /> Many of these older mines have slopes as steep as 1.2H:1V compared to the 3H:1V proposed <br /> minimum slope of the Revenue and Atlas TSFs. The existing Revenue TSF has maintained <br /> slopes of approximately 1.1H:1.OV for over 120 years with no signs of slope instability. This is <br /> due to the blasted rock having extremely angular pieces,which are prone to being stable at steep <br /> angles due to the inherent angle of friction of this material. The internal angle of friction of this <br /> material is approximately 45 degrees. Since the waste rock has very little fine material,the water <br /> seepage through is expected will have no effect on the stability of the pile since there is no <br /> cohesion in this waste rock, only internal angle of friction. A slope stability analysis was <br /> submitted as Exhibit T to Amendment 1, which presents a slope stability analysis using <br /> commonly accepted circular failure equations and material parameters for both the Revenue TSF <br /> and the Atlas TSF. The analysis indicates that the waste embankments have a calculated safety <br /> factor above 1.3,using conservative strength parameters,which constitutes an adequate design. <br /> Geotech on slope stability on tailings produced by the Revenue Mill will be redone by a private <br /> consulting firm once the mill is producing tailings. <br /> Map C-IA shows the avalanche path that covers a large portion of the Revenue TSF. The Atlas <br /> TSF is located in an area that is lower risk from avalanches whereas the Revenue TSF area is in a <br /> high-risk area for avalanche activity. A plan has been incorporated to safely trigger these <br /> avalanches using an experienced contractor. <br /> Revenue Mine <br /> Amendment 02 D-18 <br /> Updated August 2022 <br />