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<br />. <br /> <br />MEMORANDUM <br /> <br />COLORADO WATER CONSERVATION BOARD <br />DARIES C. LIlE <br />DIRECTOR <br /> <br />DATE: <br /> <br />December 9, 1997 <br /> <br />TO: <br /> <br />Alan Leak <br />WRC Engineering, Inc. <br /> <br />FROM: <br /> <br />Tom Browning <br /> <br />RE: <br /> <br />Weldona Mitigation Plan <br />Preliminary Design Criteria for Roadside Ditches <br /> <br />I have the following suggestions for preliminary design of the roadside ditches in <br />Weldona: <br /> <br />. . Capacity: Let's shoot for the 5-year storm event <br /> <br />. Flow velocity: Minimum = 2 fps, maximum = 5 fps <br /> <br />. Geometry: Triangular with max. side slope of 3H to IV <br /> <br />. Channel lining: Grass <br /> <br />. Longitudinal slopes: 0.4% to 2.5% <br /> <br />. Freeboard: Velocity head <br /> <br />. Roughness Coefficient: n = 0.045 +/- (assume unmaintained grass) <br /> <br />. Driveway Culverts: Design flow should not overtop driveway. Min. diameter of 12 <br />inches with F.E.S. <br /> <br />Please let me know if you have any comments or other ideas regarding this issue. <br />Thanks! <br /> <br />. <br /> <br />- -- ---=- <br /> <br />- - - - ~----- <br />