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STATE OF CC~II ~I~~I~~I~~~~~~I~ <br />MINED LAND RECLAMATION DIVISION <br />Department of Natural Resources <br />1313 Sherman St., Room 215 <br />Denver, CO 80203 <br />303 866-3567 <br />RA x: 303 832-8106 <br />OF'CprO <br />R~ . 9-y <br />~~' ~ O <br />. r.+ <br />re]6 <br />Roy Romer. <br />Governor <br />Fretl R. Barra. <br />Division Director <br />DATE: February 7, 1992 <br />T0: Steve Wathen <br />FROM: Joe Dudash <br />RE: Colowyo, Permit No. C-81-019, Minor Revision 19 <br />Addition of Culvert to Goddard Loadout Ditch <br />I have reviewed the hydrology material submitted by <br />Two side-by-side 24-inch diameter culverts can pass <br />as long as the ditch is at least 31 inches deep. A <br />needed, or seven inches above the two-foot diameter <br />flow. The operator should confirm that the ditch i~ <br />inches deep. <br />the operator for MR-19. <br />the peak flow of 31 CFS, <br />headwater of 31 inches is <br />culvert, to pass the <br />i this area is at least 31 <br />Energy dissipaters will be needed at the outlet of both culverts. At full <br />flow, the exit velocity is V = Q/A = 31 ft/sec 2 x 3.14 = 4.94 ft/sec. At <br />less than full flow, the velocity would be even higher since 'A' would be <br />smaller. According to "Applied Hydrology and Sedimentology for Disturbed <br />Areas," the maximum allowable velocity for the Pinelli loam at the loadout is <br />3.5 ft/sec. If riprap is used as the energy dissipater, the riprap should <br />have a proper bed and grading, and be constructed of angular rack material. <br />The riprap design parameters should be submitted by the operator before <br />construction. <br />Finally, if the fill around the two culverts will be loam, then inlet <br />protection to minimize erosion between the two culverts is advisable. <br />JJD/bjw <br />cc: Larry Routten <br />1217E <br />