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<br />• <br /> <br />Assumptions and Explantion of Chart <br />Culvert Number "L" prefix refers to load-out area culverts <br />Other culverts are in mine area <br />Travel Length (pt) Furthest point from culvert within watershed <br />Elevation Change (pt) Elevation of furthest point - invert elevation of <br />upstream edge of culvert <br />Slope Elevation Change <br />Travel Length <br />Velocity ,From Figure 3.1, Reference No. 2 (TR-55) assuming <br />nearly bare ground <br />Travel Length 1 <br />Tc (hrs) Velocity x 60 sec x 60 min <br />min hr <br />Drainage (acres) From watersheds as shown <br />Rainfall 10-year - 24-hour storm = 1.8" <br />CN 89 - <br />65 - <br />sage <br />79 <br />area <br />medi <br />used for active mine or load-out area <br />used for undisturbed land (20% cover density <br />and grass - Figure 5-3, Reference No. 2) <br />Watershed to culvert L11 has some active <br />and some undisturbed. 79 was chosen as <br />3n CN <br />Runoff From Table 5-3, Reference No. 2, 1.8" rainfall <br />Cumulative Tc When watershed to a culvert includes several <br />culverts, the longest overland flow was used to <br />determine Tc <br />M133 <br />..~_ .s;,,.~. is ,.. ..aa.:,,.i...'.;'<A-.~'. y .: ~ <br />