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• • iii iiiiiiiiniii iii <br />DEPARTMENT OF NATURAL RESOURCES <br />Davia tl. Getches, Executive Dire:.tor ti <br />P~d9~9~7 L,IAN®F~EGl..A4'~~~aT'C~~1 ®IV9~it~la8 ~ :~ ~, <br />DAVID C. SHELTON, Director ~ y4p•~:. ~~ ~ t <br />Richard D. Lainm <br />Governor <br />TO <br />Uan fr~athews <br />FROI~i: Candace Thompson ~ ~/ <br />DATE: October 10, 1984 <br />RE: Gear Coal Coiripany - 100 year -Flood Control Dike <br />The n value used to determine the 100 year flood depth in the mine area is <br />conservative, representing a d5pp riprap size of 0.5 feet. However, use of <br />an n value representiny a d5p of 2.0 feet gives only a 1 foot higher flood <br />depth. The permittee has allowed for 2.U feet of free board in the dike <br />design. so with the use of the more representative n value, 1.0 foot of free <br />board could still be maintained. Also, t~~e mine site is located at the inside <br />of a curve, sc. superelavation will tend to decrease flood depth at the mine <br />site. All ot.?~er factors appear to be representative. The desiyn of the dike <br />and sediment treatment 'Facility is approvable. <br />/fw <br />Dec. 4656 <br />423 Centennial Building, 1313 Sherman Street Denver, Colorado 80203 Tel. (30?) 866-3567 <br />