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<br />2.05.3(4) <br />(4) Ponds, Impoundment and Diversions <br />(a) A general plan and detailed design plan for each sediment <br />pond, water impoundment and diversion proposed to be constructed <br />within the permit area. <br />Figure 2.05.3(4)(a)-1 and Map 2.05.3(4)-2 are taken from <br />Grand Mesa Coal Company's former permit #77-232 to identify the <br />present drainage system for the mine site. <br />The size of the existing pond was checked with an air photo <br />taken September 20, 1982 and found to have a water volume of <br />2.16 a.f. compared to the design volume of 2.61 a.f. The storm <br />event used in this design was a 2.4" 10-year 24fhour storm. <br />Closer interpolation of the charts gives a 2.2~ storm as used in <br />this permit application on page 101. Using this new storm event, <br />the required volume for water storage is calculated using the SCS <br />runoff formula: <br />,oe~~ `~aws r+o.ss <br />,,,rte /J Q = Runoff in inches <br />Inc <br />P = Accumulated precipitation (2.2") <br />S = (1000/CN) - 10 <br />f <br />Q(CN 74)• = 0.45" <br />Q(cN sa = 1.13"~ ~' <br />Storage Volume = Q x area = (0.45 x 1..783) + (1.13 x 23..34 <br />( 12 <br />Storage Volume = 2.26 a.f.-~ <br />In addition to being short on runoff volume, mine inflows were not <br />included. The calculated maximum mine inflow for the Red Canyon <br />#1 Mine was taken from the Kaman Tempo Hydrologic Report (page 50, <br />Appendix H), 26.1 gpm. / The additional water storage volume <br />REVISED August 21, 1984 <br /> <br />96a <br />