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2018-09-07_REVISION - C1981010 (2)
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2018-09-07_REVISION - C1981010 (2)
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Last modified
9/10/2018 12:45:54 PM
Creation date
9/10/2018 9:19:24 AM
Metadata
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Template:
DRMS Permit Index
Permit No
C1981010
IBM Index Class Name
Revision
Doc Date
9/7/2018
Doc Name
Adequacy Review
From
Trapper Mining Inc
To
DRMS
Type & Sequence
PR9
Email Name
RAR
Media Type
D
Archive
No
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Trapper Response to Comment 21: Ash pit cross-sections are enclosed as requested. Please note that <br />nowhere in the PR -9 Permit Application did Trapper state that "Excess Spoil" was to be hauled from N Pit <br />and taken to the Utility Waste Area. Trapper plans on removing 50 to 60 % of the N Pit boxcut material <br />with draglines and spoiling the material to the west of the boxcut. This material would be regraded into the <br />existing landscape, similar to historical dragline spoil boxcuts at Trapper. Approximately 40 — 50% of the N <br />Pit box cut material would be hauled with the truck and loader fleet to the Utility Waste Disposal Area (ash <br />dump) south of the N Pit boxcut area to assist with reclamation efforts there. The utility waste currently is <br />filling an area left between the dragline spoils to the south and a natural ridge to the north. The additional <br />truck and loader material from N Pit would be hauled to the Ash Dump and used to finish filling the area <br />between the dragline spoils and a natural ridge, and to create a "broader ridge feature" above the utility <br />waste footprint so that the requirement of not having a drainage fall within 50 feet of a Utility Waste <br />Disposal Area can be fulfilled. The material hauled from the boxcut would overlie areas of previous ash <br />disposal and provide fill material that would create positive drainage away from the ash placement area. <br />Trapper has never mentioned hauling this material to the "L" Pit Area as the current distance is 2.6 miles, <br />most of which includes a steep uphill climb with loaded trucks. This haul cycle would not be economically <br />viable for Trapper. <br />It appears that TMI considers oWhverburden from the box cut at Nighthawk <br />Pit as "excess spoil". <br />22. Please consider and discuss the possibility of utilizing this material to mitigate <br />the pre and post mining elevation difference in L pit cross section E1,441,000, <br />rather than creating excess spoil. (See adequacy question 24, below.) <br />Trapper Response to Comment 22: Trapper does not consider the spoil being removed from the N Pit <br />boxcut as "Excess Spoil" but rather additional spoil. On page 349 of the Trapper Permit there is a brief <br />discussion concerning Excess Spoil. The second sentence of that discussion states, "Also, boxcut material <br />generated during the permit period is not considered excess spoil (refer to section 3.5.4) and can be used <br />where it occurs to achieve the approximate original contour." Trapper's opinion is that this is exactly what <br />is taking place in that the material is being utilized to create a landform that conforms to AOC, and one that <br />helps create a post mine drainage that reduces the potential of surface water to infiltrate into the Utility <br />Waste Area. <br />23. Please, also provide the following specific cross section drawings for Nighthawk <br />pit: a. At E1,426,000 <br />b. At N409,000, across the middle of N pit <br />Trapper Response to Comment 23: The requested cross-sections are enclosed. <br />DRMS notes that on map M14A for the Lancaster Pit, the proposed elevation <br />delta when compared to the post mining M12 map is approximately 200 feet. <br />This appears to be a significant change in elevation. <br />24. For the Lancaster Pit, at cross section E1,441,000 please explain why the post <br />mining topography proposed is 200 feet lower than the topography of the <br />October 2016 survey and map (M3). <br />
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