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• Culvert I <br />Use same design parameters as Road Drainage Ditch 1 <br />Peak flow = 0.51 cfs <br />Diameter required = 18-inch CMP minimum, with a minimum of 2 feet <br />compacted cover, and riprap protection at the inlet and outlet <br />Road Drainage Ditch 2 <br />Design Parameters: <br />Precipitation: <br />Use 10-year, 24-hour storm precipitation depth = 1.8 in <br />Land Use: <br />Undisturbed area =19.987 ac with CN = 63 (sagebrush - hyd. soil gp. C) <br />Road surface (gravel) = 0.698 ac with CN = 89 <br />Maximum road grade = 9.4 <br />Ditch length= 1,190 feet <br />Ditch design =triangular ditch with 3:1 side slopes (see Figure 2) <br />Ditch surface material is alluvial silts colloida) <br />Limiting ditch velocity = 3.75 fps <br />Results: <br />Peak flow = 0.64 cfs <br />Peak velocity = 3.62 fps <br />Culvert 2 <br />Use same design parameters as Road Drainage Ditch 2 <br />• Peak flow = 0.64 cfs <br />Diameter required = 18-inch CMP minimum, with a minimum of 2 feet <br />compacted cover, and riprap protection at the inlet and outlet <br />CERTIFICATION <br />I, Richard Spotts, state that the information presented in the Intake Shaft Facility <br />Access Road Drainage Ditch and Culvert Design Report for Peabody Energy <br />Twentymile Coal Company was prepared by me or by persons under my <br />supervision and is correct to the best of my know-edge and information. <br />Water & Earth Technologies, Inc. <br />Richard Spotts, P.E. <br />President <br />Principal Engineer/I-lydrologist <br /> <br />