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iiiiiiiiiiiiiiiiiii <br />999 <br />DEPARTMENT OF NATURAL RESOURCES <br />Oevla M. Ge4nee, EceanM Olneelor <br />MINED LAND RECLAMATION DIVISION <br />DAYIDC.~NELTON, Dlraetor <br />Ricnerd D. Lamm <br />Gwemor <br /> <br />DATE: June 7, 1984 <br />T0: Gregg R. Squire <br />FROM: P. C. Saletta p . ~ <br />RE: Carbon Junction Mine; As Built on Sed. Pond No. 2; Minor Revision - <br />Fili Underdrain <br />As per your request I have reviewed the above items. <br />Concerning the "As Built" on Sediment Pond No. 2, I find the analysis <br />adequate and acceptable. However, in order to function as design~d the <br />dewatering device outlet should be reduced to an area of 0.067 ft <br />(D=3.5 in.) or slightly less, as calculated. The operator's consultant . <br />(Pencor) has suggested reducing the area by welding a 1/8" metal bar across <br />the existing 4 inch orifice. This would be a satisfactory and practical <br />approach to decreasing the orifice size. The dewatering device should allow <br />for a detention time of 24 hours or greater in order to ensure that effluent <br />standards would be met, thereby minimizing the possibility of any future <br />problems. <br />In regard to the Minor Revision for the Fill Underdrain, I requested this <br />information to verify if the original design for the underdrain would carry <br />the drainage from overlying fill material. The methodology used applies <br />calculations and equations from the CTL Thompson Report for OSM Engineering <br />and Desi n Manual for Dis osal of Excess S oil. If the underdrain is <br />insta a as eslgne 1 show a equate y carry drainage from the overlying <br />fill. The calculations submitted by Pencor verify that the design is adequate. <br />If you or the operator have any further questions or comments please contact <br />me. <br />/ph <br />Doc. No. 1900 <br />423 Centennial Building, 1313 Sherman Street Denver, Colorado 80203 Te1.130z) 868-3567 <br />