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AFS Response to DRMS Adequacy Review#2 September 14, 2021 <br /> #25 The Arcadis stability analysis does not address the fines material currently being stockpiled <br /> on-site or the proposed fines stockpile location for the Spur amendment area indicated on the <br /> revised Exhibit C-3 map. Please provide the following information regarding the on-site <br /> fines stockpiles: <br /> a. Please provide a geotechnical stability analysis for the current and proposed fines <br /> stockpiles pursuant to Rule 6.5. <br /> b. Please provide the material placement procedures for the current and proposed fines <br /> stockpiles pursuant to Rule 3.1.5. <br /> c. Please explain how the current and proposed fines stockpiles are/will be stabilized to <br /> prevent potential down gradient movement. <br /> d. Please provide parallel and perpendicular cross-sections for the current and proposed <br /> fines stockpiles at final reclamation. <br /> e. Please revise the Exhibit C-3 map to indicate the current fines stockpiles locations. <br /> AFS Response: Per our phone discussion (Joel Bolduc and Peter Hays) on September 13, 2021, <br /> the area referred to in the comment above as the "current fines stockpile"is the active mining <br /> area and is not an actual fines stockpile. The "proposed fines stockpile"referred to above and <br /> identified as the "Fines Stockpile Area" on Exhibit C-3 (revised August 2021) involves the <br /> filling of a low area. This low area that will be filled is surrounded by higher slopes, and there is <br /> no possibility of slope failure of the fill area. Thus, a geotechnical stability analysis, material <br /> placement procedures, and an explanation of how the stockpiles will be stabilized to prevent <br /> down gradient movement are not needed. See Attachment 4 for a cross-section of the"proposed <br /> fines stockpile". <br /> Also,per our phone conversation, the mining plan has been revised to reflect the change of the <br /> north area of the Existing Quarry from a reclamation slope of 3:1 (in 2002) to not exceed 2:1. <br /> See Attachment 1 for revised Exhibit D Mining Plan. In a related matter,the slope stability of the <br /> north slope is assured by mining the backside of the north dipping foliations of the north slope in <br /> a northerly direction to avoid planar failures. See Attachment 7 for the Evaluation of Mining <br /> Methods Walstrum Quarry (Revey, March 2002)previously submitted and approved by DRMS <br /> April 26, 2002. <br /> #27 The Division sent a copy of the Geotechnical Review Memo from Zach Trujillo dated August <br /> 31, 2021 to the Operator on September 2, 2021. Please respond to the adequacy concern in <br /> the memo. <br /> TR UJILLO SLOPE STABILITY COMMENT: When comparing the Division's slope profile to <br /> that of the provided profiles with the supplemental information, it appears that the angle of slope <br /> used for the low strength rock do not match. Using a 45-degree angle for the low strength rock, <br /> the Division's slope profile appears to be angled steeper than that which was provided with the <br /> supplemental information. When measuring the provided slope angles within AutoCAD, the <br /> maximum angle discovered was 40 degrees. This difference in a higher angle would result in the <br /> lower factor of safety as observed with the Division's results for the sensitivity analysis. This <br /> leads the Division to believe that perhaps there is a typo in Table 5 within the Exhibit and a <br /> lesser angle of slope was used for the sensitivity analysis to result in a factor of safety of 1.15 <br /> under pseudo-static conditions. <br /> Page 2 of 3 <br />