Laserfiche WebLink
Response: Colowyo has chosen not to change the swell factor to 15% at this time and <br />has revised all calculations to reflect the permitted swell factor of 20%. At such time in the <br />future when Colowyo deems it prudent to change the permitted swell factor, the requested <br />additional information and justification will be provided. <br />3. Colowyo has proposed to change the swell factor for the South Taylor Pit from 20% <br />to 15%. It has been stated (but not documented) that this change in swell is due to the <br />change in mining method from the dragline(s) to the truck/shovel operation. Since the <br />majority of the South Taylor operation is a truck/shovel operation, it would follow that the <br />swell factor for the entire South Taylor Pit would be affected by the change in swell factor, <br />not just the excess spoil fills. Based on this decrease in swell factor, the overall amount of <br />material from the entire pit will experience a decrease in swell. <br />The South Taylor Pit Box-Cut area encompasses approximately 500 acres (Map 23A). <br />Based on Figure 2.04.6-313 - Generalized Stratigraphic Column-South Taylor, Colowyo is <br />planning on Mining to the G8-Seam, which would put the pit floor approximately 513.5 feet <br />below the original ground surface. In the currently approved permit, Colowyo will remove <br />approximately 103 million cubic yards from the box-cut (60 million yards in permanent fills <br />and 43 million yards in the temporary overburden stockpiles). This volume is given in loose <br />cubic yards and is based on a swell of 20%. The bank volume, based on this 20% swell, <br />would be approximately 85.8 million yards. If, in fact, the swell factor for the South Taylor <br />Pit box-cut area is decreasing to 15% this would lead to a total (swelled) volume of 98.7 <br />million cubic yards of spoil moved out of the pit. This is a decrease in spoil of <br />approximately 4 million cubic yards of spoil material. <br />In TR-81 Colowyo is proposing to increase the size of the permanent fills in the South <br />Taylor Pit area by approximately 10.3 million yards. Colowyo is also proposing to decrease <br />the swell factor from 20% to 15%, leading to a decrease in loose spoil of approximately 4 <br />million yards. The overall result of these two actions would be to decrease the amount of <br />material going back into the South Taylor Pit by approximately 14.3 million yards. Based <br />on these observations the Division believes that it would be more appropriate to decrease <br />the size of the South Taylor Fills rather than increase their size. A further increase in the <br />size of these fills would lead to a further decrease in the final topography in the South <br />Taylor Pit. This decrease will be further amplified by the truck/shovel material that will be <br />direct hauled to the pit as mining progresses. <br />Pursuant to Rule 1.04, excess spoil is, by definition "...material not necessary to <br />achieve the approximate original contour..." Please provide the Division with a <br />detailed justification why the additional 10.3 million yards of spoil material (in <br />addition to the decreased spoil of 4 million yards due to the decreased swell factor) <br />meets the definition of excess spoil and is not required to meet AOC, keeping in <br />mind that the Division has already granted Colowyo a variance in AOC for steep <br />slope mining and will not grant a further variance without good cause. <br />Response: The spoil volumes were recalculated for this submittal to reflect the permitted <br />of 20% swell factor. Other changes within this submittal, including the reduced mining <br />limits, disturbance footprint, and postmining topographic surface revisions have changed