2016-11-23_PERMIT FILE - C1981008A

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h. All principal spillways will have 2 seep collars installed within the dam which will be at least 2x the pipe diameter. All dam fill will be compacted around the seep collars and principal spillway pipe to 90% of the maximum dry density of the fill material. i. The emergency spillways will be a rip -rap lined trapezoidal channel of 10 feet bottom width and 2:1 side slopes. j. Attachment 2.05.3(3)-15 demonstrates that the given materials on site have been tested for suitability in constructing pond embankments and that the long term slope safety factors exceed 1.3 in all cases, given the pond design parameters outlined above and in the Attachment. For this reason, no individual slope stability analyses are presented for the ponds. Pit dewatering may occur year round or during portions of a year. The dewatering process will be a sporadic operation -controlled, occurrence depending on various factors which may include the location of the pit inflows, the location of standing water in the pit, or the location within the pit of the overburden and coal removal operations. When pit dewatering is required, the anticipated dewatering rate will be in the range of one to two cubic feet per second or less. Prior to Pond 011 being built, all pit dewatering discharges were directed to Pond 007, which was the main pond for the western portion of the permit area. Direct pit pumping into Pond 011 now occurs. These procedures have been applied for in New Horizon's NPDES Permit, which is similar to Permit CO -0000213 for Ponds 007, 008 and 009. The revised NPDES Permit is enclosed in Attachment 2.05.3(3)-18. Mine pit dewatering was transferred from Pond 011 to Pond 013 in June 2011. These changes are reflected in the amended NPDES permit. The mine pit dewatering shifted from Pond 007 to Pond 011 in June 2008. Pit dewatering will have an insignificant impact on Pond 011. The flow rate of one to two cubic feet per second or less compared to the designed 25 -year, 24-hour peak inflow rate of 33.5 cubic feet per second is not significant. This is demonstrated in detail in Attachment 2.05.3(3) 2.05.3(3)-14 POND 11 ENGINEERING AND HYDROLOGIC DESIGN. Ponds 009, 012, 013, 015, 016, and 018 will be maintained until: 1. The disturbed areas are reclaimed and the vegetation success requirements of Section 2.05.4(2)(e), revegetation are met. Page 2.05.3(3)-14 January 2016 (TR -70)