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~w <br />iii iiiiiiiiiiiii iii <br />999 <br />STATE OF COLORADO <br />MINED LAND RECLAMATION DIVISION of ~a~ <br />Department of Natural Resources tip, ' a~ <br />N~ <br />1313 Sherman St., Room 215 ,~ ~ <br />Denver, CO 80203 ' ~^ ~ "' <br />303 8663567 ~.,~ 76 <br />Fn x: 303 832-8106 <br />Roy Romer, <br />Governor <br />Freo R. Banta. <br />Division Director <br />February 5, 1992 <br />Juan Garcia <br />Hydrologist\Engineer <br />Colowyo Coal Company <br />5731 State Highway 13 <br />Meeker, CO 81641 <br />RE: Colowyo Mine, Permit C-81-019 <br />Completeness and Adequacy Review <br />MR-19; Addition of Culvert Crossing to Goddard Diversion Ditch <br />Dear Mr. Juan Garcia: <br />The Division has received and reviewed Colowyo's application for a <br />minor revision to add a culvert crossing to the Goddard Loadout <br />Diversion Ditch. The application has been found to be complete at <br />this time. <br />The Division has identified the following adequacy concerns which <br />need to be addressed: <br />1. The Division concurs that the emplacement of two side-by- <br />side 24 inch diameter culverts will pass the ditch design <br />peak flow of 31 cubic feet per second. A headwater of 7 <br />inches is required above the 24 inch culverts to <br />accommodate the passage of the 31 cubic feet per second <br />of flow. <br />The ditch will have to be maintained at 31 inches in <br />depth or greater immediately above the culvert crossing. <br />2. The Division calculates that at full flow, the exit <br />velocity at the culverts will be 4.94 feet per second. <br />According to "Applied Hydrology and Sedimentology for <br />Disturbed Areas", the soil the ditch is constructed in <br />has a maximum allowable velocity (before erosion) of only <br />3.50 feet per second. <br />Please verify that outlet protection of the diversion at <br />the culvert outlets will be installed and how this will <br />be done. <br />