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(, iii iiiiiiiiiiiuiii <br />999 <br />DEPARTMENT OF NATURAL RESOURCES <br />David H. Gelche0. Executive Director <br />MINED LAND RECLAMATION DIVISION <br />DAVID C. SHELTON, Director <br />Richard D. Lamm <br />Governor <br />March 30, 1984 <br />Mr. Dave Smaldone <br />Director of Engineering <br />Chimney Rock Coal Company <br />P. 0. Box 2679 <br />Colorado Springs, CO 80901 <br />Dear Dave: <br />This letter is in regard to our telephone conversation of March 22, 1984 <br />concerning sediment pond dewatering. I am enclosing two drawings showing <br />typical dewatering devices. Both are single hole devices, however the <br />system is more er'fective if several holes are spaced along the riser going <br />upward, smaller to larger. Dewatering time is computed using orifice flow <br />as shown on pages 229 and 230 in Applied Hydrology and Sedimentology for <br />Disturbed Areas by Barfield, Haan and Warner. The flow for each hole in <br />a mu ti-hole system needs to be computed keeping in mind that as the water <br />level is lowered below each hole, it is no longer contributing to the flow. <br />The head is figured to be half the distance from the highest functioning <br />hole to the maximum level that the water can reach before either the pipe <br />flows or the next highest hole functions. The head needs to be refigured <br />each time the water level drops below a hole and it ceases to function. <br />The volume divided by the total flow rate will give you the time. <br />If you have any further questions, I will be glad to answer them. <br />Sincerely, <br />r <br />/, ~ / ~, l /N ./ lr .. <br />. 'VC/ <br />Anne Baldrige <br />Reclamation Specialist <br />cc: Greg Squire <br />AB/nm <br />Enclosure <br />423 Centennial Building, 1313 Sherman Street Denver, Colorado 80203 Tel. (303) 866-3567 <br />