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an area of disturbance associated with the pit, the Pond 015 excavated <br />material stockpile area, and the area between ditch C27 and ditch D1W. <br />This area is shown on Map 2.05.3(3) -20. <br />4 <br />b.) The runoff curve number, CN, for Ditch C27 has been reduced from 79 to 76. <br />Please provide a rationale for the curve number selected, including the assumed <br />Hydrologic Soil Group and any other factors considered. <br />Response: Soil Group C was used with open space fair value of 79. A CN of <br />79 should have been used to calculate the Peak Runoff. Further, the correct <br />Time of Concentration value should be 0.368 which is shown in the TC <br />calculation on page Attachment 2.05.3(3) -1 -46. The Graphic Peak Discharge <br />was rerun with the correct Tc= .37 and a CN =79. The new Graphic Peak <br />Discharge Report has been inserted into Ditch C27 calculation and a new <br />page Attachment 2.05.3(3) -1 -46 is provided in this response. <br />c.) For Ditch C27 channel design, the As -Built Bed Slope is given as 2.04 %, while <br />the Design slope was given as 6.50% <br />Response: The ditch C27 slope (2.04 %) is the overall slope from the survey of <br />the ditch itself. <br />d.) The Channel Lining is now described as "Sandy loam noncolloidal ". During a <br />site inspection, the Channel was observed to be lined with materials of varying <br />characteristics, including fractured rock. Please verify that accurate materials and <br />values have been considered and selected for incorporation into the analysis. <br />Response: Ditch C27 was excavated through a range of materials as best <br />described as: "Rock" with a Manning's N = 0.035 - 0.040; "Natural Channel" <br />with a Manning's N = 0.030 - 0.035; "Earth, weeds /cobble bottom" with a <br />Manning's N = 0.030 -0.40. A Manning's N of 0.0325 is a reasonable number <br />to use for the As -Built Manning's N. An As -Built channel slope of 2.04% will <br />be used in the As -Built Design. The width of the As -Built Ditch C27 was also <br />checked and the bottom width is 3ft rather than 4ft, a new Ditch C27 design <br />was run. A new Attachment 2.05.3(3) -1 -47 is provided. <br />e) For Ditch D1W, which diverts "clean" water from the as- yet - unmined western <br />area of the permit, the Drainage area has been reduced- from 12.605 acres to 6.78 <br />acres. The text explains that this is due to the contributions of several different <br />sub - watersheds. (No response is needed.) <br />5. Attachment 2.05.3(3) -18- NPDES Permit <br />With TR -60, amended Discharge Permit No. CO- 0000213 has been provided for <br />inclusion in the permit as Attachment 2.05.3(30- 18.... "JUNE 30, 2013 ". Please <br />delete this date from the title; it does not appear to correlate with any dates associate <br />with the discharge permit, and is confusing and unnecessary. <br />Response: New Attachment 2.05.3(3) -18 title page is attached. <br />X: \Western Fuels Nucla \TR- 60 \TR -60 adequacy question #1 \TR -60 PRELIMNARY ADEQUACY RESPONSE <br />25AUG11.doc <br />