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NUCLA PR NO. 2 <br /> (b. ) 2667.4 tons of sediment described on Attachment 13-G, page 9 was <br /> calculated by the SEDIMOT II computer run for the 10-year, 24-hour <br /> precipitation event (see Attachment 13-G, Addendum A) using the Modified <br /> USLE method. <br /> Comment: <br /> 14. When calculating required ditch size for the Nucla East area, the <br /> Division does not believe Peabody will get any flow with a 0% <br /> slope. Please specify the proposed minimum slope for ditches. <br /> Response: <br /> Attachment 13-G, page 13; Volume 11, Exhibit "13-16" , and Volume 12, <br /> Attachment 16-1, Exhibit "13-16" has been revised to include a minimum <br /> slope. <br /> Comment: <br /> 15. Has pond 007 sizing taken into account the effects of pit <br /> dewatering contributions? If not, please modify your sizing <br /> accordingly. <br /> Response: <br /> See question number 9 above. Pit dewatering will not significantly <br /> affect the sizing of Pond 007. Pit dewatering will be determined by <br /> operational constraints. Historically pit dewatering at Nucla is less <br /> than one to two cfs. This flow will drain into Pond 007 and accumulate <br /> in the dead storage area of the pond below the principal spillway. If <br /> the duration of the pit dewatering lasts long enough then as the water <br /> level in Pond 007 rises, flow will begin out of the principal spillway. <br /> As shown with the 10-year, 24-hour storm routing, adequate detention <br /> time is provided for the 81.5 cfs peak design inflow rate; therefore, <br /> adequate detention time is also available for a lesser flow of only one <br /> to two cfs. Again pit dewatering is controlled manually by operations <br /> personnel and the dewatering can be interrupted if Pond 007 is not <br /> functioning as designed. <br /> Comment: <br /> 16. Pond 007 is a very large pond, with a capacity of 31.26 acre-feet. <br /> This classifies it as a Mine Safety and Health Administration <br /> (MSHA) pond (20 acre-feet) and thus must receive MSHA approval <br /> prior to construction. Peabody should file for approval as soon as <br /> possible, and notify us of the lead reviewer on the project, so <br /> that CMLRD specifications can be included in the design. <br /> Response: <br /> Based on past discussion with MSHA personnel and other professionals in <br /> 21 <br />