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The main haul roads within the mine area will be <br />• within the drainage areas used to size the sedimentation ponds <br />and all runoff from the roads will be drained to these ponds <br />through ditches, culverts, and pumps. The roads will have main- <br />tained drainage ditches on both sides where possible and will be <br />crowned to facilitate quick drainage (see Cross Section, Figure 3). <br />Culverts will be a minimum of 18-inch diameter to safely pass <br />runoff from a 10 year 24 hour event. An 18 inch diameter culvert <br />will carry off flow of more than 7 cfs at a 5~ slope, which is <br />about the maximum flow for a 10 year 24 hour event in diversion <br />ditch D (7.2 cfs). Therefore, both haul road crossings of that <br />ditch will have 18-inch culverts. The culvert southeast of the <br />shop area and the culvert where the in-mine drainage passes under <br />the M&T road (as required) will also have at least 18-inch diameter <br />culverts even though their maximum flow will be considerably less <br />than 7 cfs for the 10 year 24 hour event. Culverts will be covered <br />to a minimum depth of one foot, and will be protected from plugging, <br />collapse or erosion at inlets and outlets with rock headwalls and <br />• riprap. <br />To gain access to Pit 2 the light duty road that <br />serves the M&T Incorporated oil well will be improved to haulroad <br />status as required under Section 4.03.1 of the Colorado Regulations. <br />These improvements will necessitate widening the road and replacing <br />the old culvert with a new one of sufficient size and length. <br />The total area drained by this culvert is approximately 193 acres. <br />Using a CN of 76 and 90 cfs/in runoff the resulting runoff for a <br />10 year 24 hour event is 90 X .23 = 20.7 cfs. These figures when <br />entered into Manning's Equation and reduced to find the diameter, <br />indicate a 30-inch corrugated culvert would be sufficient when <br />placed on a 18 slope. <br />• <br />-33- <br />