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Doc Date:12/1112001 <br />5/v STANDARD DITCH DESIGN <br />lflTRODUCTION <br />~-~ <br />s iz ~F7 y <br />III IIIIIIIIIIIII III <br />This paper is a guide to be used to select the proper sized ditch~fpr both <br />.BSul Roads and Access Roads at Utah.International's Trapper Mine. The office of <br />s~riface mining's final regulations have stipulated that all C1asa I and Class II <br />817aiis (Haul Roads and most Access Roads) use structGres such as. ditches to safely <br />pas$ .the peak runoff from a 10-year;' 24-hour precipitation event. (30 CFR 816:153 <br />(~ (1) and '30 CFR 816.163 (a) (1) ). The ditch desi.gna specified in this paper <br />4iE~~"in.compliance~with this regulation. <br />the'basic design covered in this paper is a V-shaped Ditch with 1:'1 side <br />aliip~s•and of varying depth. This design is capable.o.~ handling any 10-.year, <br />~2fi~`ttiiur peak runoffs encountered on the minesi[e and is much easier to construct <br />aSd•maintain than flat bottom ditches, particularly with the equipment available <br />aS~tbe minesite. <br />DE9~GN CRITERIA <br />The following are. the design criteria used in this paper: <br />- V-,shaped ditch, 1:1 side slopes <br />- £=aig area 10-year, 24-hour event - 1.7" <br />- Ii~drologic soil group type - curve 70 <br />- Sua~off for 1.7" of precipitation - 0.14" <br />- Dit4limum slope of ditch - 0.5% <br />- Factor of safety - 1.3 <br />- Cti=efficient of roughness - 0.030 <br />.Manning's equation was used to calculate the velocity of flow. This velocity <br />titaea~the cross-sectional area of the ditch will give the quantity of flow the <br />d7:Y6h.'can contain. <br />The ditch slope used in Manning's Equation was. assumed to be the minimum that <br />would ever. be used at the minesite. This is a very conservetiye assumptipn, but will <br />iit~ui'2 that afl of the ditches constructed in accordance to Ehis paper ar in <br />con¢[tiaace regardless of the ditch slope. <br />The following 'is a sketch of a typical V-shaped ditch and the equations used:, <br />D ~{ <br />y I <br />:/ <br />~j~~\ / ~ <br />~/; <br />S MantYfpg's Equation: (1) <br />V-y 1.486 R 2/3 S'~ <br />n <br /> <br />