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convey the water to the sedimentation pond. Exhibit 3.5-22, Sheet 1, shows <br />conceptualized locations for culverts on the regraded Moffat Area. The <br />regraded surface is used to assist in visualizing where appropriate locations <br />will occur. The actual placement of culverts will be determined by mine <br />personnel based on the actual field conditions. <br />It is anticipated that the final culvert locations will be synonymous <br />with the restored drainage basin channels. As such, prior to installing a <br />given culvert the watershed area serviced by the culvert will be calculated <br />and design parameters determined to ensure appropriate sizing of the culvert <br />from the design flow. Additionally, to minimize erosion the discharge from <br />culverts which flow onto reclaimed areas will be calculated to determine if <br />the discharge is sufficient, in terms of volume and velocity, to necessitate <br />construction of designed channels to carry the runoff downslope or if other <br />erosion control and energy dissipation methods aze more appropriate. <br />3.5.3.2 Design Criteria for Peak Flow Determination <br />Runoff from drainage areas to the culverts along the upper haulroad in <br />the Moffat Area which will serve as a postmining access road will be designed <br />using the computer modeled SEDIMOT II, developed by the University of <br />Kentucky, The model simulates the storm routing of a 10-year, 24-hour storm <br />event from the drainage area to the culvert. In order to simulate the storm <br />event the drainage area of the culverts will be divided into subwatersheds <br />according to the mining and reclamation sequence. Input parameters for each <br />subwatershed including area, hydraulic length and slope of the subwatershed, <br />hydraulic length and slope from the subwatershed to the culvert and curve <br />number will be determined. Of these parameters only the curve number is not <br />measured directly from a map. The curve numbers are dependent upon the soil <br />type, and the vegetation type and quantity found within the subwatershed. The <br />majority of the soils in the Moffa[ Area are hydrologic classification "B" and <br />"C". In order to simply calculations and since topsoil will combine several <br />soil types, all replaced topsoil will be assigned a hydrologic classification <br />"C". The designs and associated with the culverts to be placed along the <br />upper haulroad/access road will be kept on file at the Mine office for review. <br />Eor areas other than the Moffat Area, runoff from drainage areas to the <br />3.5-4 May 14,1993 <br />