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-12- • \J V. Surface water Hydrology (2.04.5, 2.04.7, 2.05.3(4), 2.05.6(3, 4.05) The Roadside and Cameo mines are located in the Colorado River drainage. The Colorado River divides the permit area into east and west portions. Tributaries to the Colorado River which flow through the permit area include Coal, Jerry, Cottonwood and Rapid Creeks and an unnamed drainage which crosses the northern portion of the permit area. The Colorado River is the only perennial stream which flows through the permit area. Rapid Creek and Cottonwood Creek are intermittent during most years, but do flow continuously during wet years. In addition, reservoirs on Cottonwood and Rapid Creeks, at the headwaters, artifically increase the duration of flows when water is released. Coal Creek, Jerry Creek and the unnamed drainage are all ephemeral streams. Coal Creek is the only stream to pass through the disturbed area near the Cameo mine. She only other surface water body within the permit area is the U.S. Government Highline Canal. The canal carries Colorado River water down the west side of Debeque Canyon, with syphons under the channels of Coal Creek and Jerry Creek. Locations of all surface water bodies are shown in Exhibit I7 in the permit application. A11 surface runoff from disturbed areas is routed through one of several sediment ponds. Eight sediment ponds have been built at the Cameo and Roadside mines. In addition to the sediment ponds, there is one collection ditch, and six diversion ditches which control runoff. All water discharged from the permit area, either from the sediments tion ponds or from mine dewatering processes, will enter the Colorado River. A11 pond and ditch designs were checked using Soil Conservation Service "Peak Flows" methods, for compliance with the design standards in Rule 4.05. A11 the ponds are designed to contain the runoff from a 10-year 29-hour runoff event and three years sediment accumulation, as determined by the universal soil loss equation. She principal and emergency spillways of five ponds are designed to route flow through corrugated metal pipes. Three ponds are designed with pumps as the principal dewatering mechanism. The principal spillway designs include a manually operated gate and are to be located directly above the three-year sediment storage Ieve1. Likewise, the pumps in the two ponds without principal spillways will be located above the three- year sediment storage level. The emergency spillways are designed to pass the 25- year, 24-hour peak flow without a head. The outflow below the spillway is to be riprapped where necessary to control erosion. The applicant, however, has not submitted evidence that the sediment ponds were constructed as designed. Therefore, the following stipulation is necessary: STIPULATION No. 1 NO LATER THAN JANUARY I5, 1983, THE PERMITTEE MUST SUBMIT TO THE DIVISION A STATEMENT FROM A REGISTERED PROFESSIONAL ENGINEER CERTIFYING THAT THE SEDIMENT PONDS PRESENTLY CONSTRUCTED HAVE BEEN BUILT ACCORDING TO THE APPROVED PLAN. CERTIFICATION OF THE REMAINING PONDS SHALL BE SUBMITTED IMMEDIATELY FOLLOWING CONSTRUCTION IN ACCORDANCE WITH RULE 4.05.6(7). ,~ _ AIZ ditches will pass the 10-year, 24-hour storm while maintaining 0.3 feet oP freeboard as determined by Mannings equation. None of the ditches, as designed, should attain erosive velocities. In the steeper portions where high velocities are attained, corrugated metal flumes and energy dissipators are used. All culverts associated with the ditch system are designed to pass the 10-year, 24-hour peak flow.