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A diversion ditch was designed (Table 2.05.3-7) and constructed from the <br />base of Culvert No. 1 to a meadow located adjacent to the Yampa River. The ori- <br />ginal design proposed a ditch across the landowner's meadow, with runoff being <br />discharged directly into the Yampa River. This structure was relocated at the <br />request of the landowner in 1983 to divert water from the base of Culvert No. 1, <br />parallel to the terrace to the Ancient Yampa River Channel, to an area adjacent <br />to the landowner's grassed runway (Map 8). The ditch is designed to convey the <br />peak flow from the 100-year, 24-hour storm event (19.8 cubic feet per second). <br />The flow velocity from the 100-year, 24-hour storm is 7.6 feet per second <br />from Culvert 1 and is conveyed in a parabolic drainage channel that is approxi- <br />mately 5 feet wide, having a 10$ slope. When the discharged water enters the <br />Yampa flood plain, the 5-foot-wide drainage ditch is constructed on a 1~ grade. <br />The flow velocity in this riprapped ditch section is reduced to 3.6 fps. Since <br />• flow velocities are less than 4.0 fps, additional riprap and channel construc- <br />tion is not believed necessary since the water is released, at the suggestion of <br />the landowner, onto his pasture. <br />Sun Coal Company's ditch maintenance and monitoring commitments are <br />outlined in Section 2.05.6. <br /> <br />- 185 - (Rev. 5/86) <br />