Laserfiche WebLink
The minimum depth that the undardrain material should ba placed is approximately 4 feet in <br />~~ the center of the draw. It is anticipated that runoff control dkches on the aurfacs should <br />transport rainwater away from the coal mine waste material so that infiltration and utilization <br />of the undardrain is minimized. Calculations relating to the undardrain is located in Appendix <br />C. <br />4.1.3 Heul Roads <br />A haul road will be eorrstructed similar to the dttarlt in the drawings. This road will serve two <br />purposes. First, it will provide public access to the Somerset Cemetery. Second, is will <br />provide access to the proposed coal mine waste bank. Because of its secondary use as an <br />aaess to the waste bank, it will be constructed as a haul road. The average grade has been <br />designed to be a maximum of 10 percent, consistent with Rule 4.03.1(31. On the outside of <br />the haul road wi0 be a small safety berth approximately 2 to 3 feet high. On the inside of the <br />haul road is a ditch sized to convey a 100-year, 24hour stone. On haul roads constructed <br />at 10 percent grades, a minimum ditch depth is 1 foot. The dhch side slopes should be <br />constructed at 2:1. Flow rates of water transported by the design storm will require scour <br />protection in the form of riprap. Riprap and filter material requirements are shown on Drawing <br />~ 95255-03, and are based an procedures devebped by the Office of Surface Mining IOSM, <br />• 19821. A plan and profile of this road is presented in Drawing 95255-05. <br />~~ <br />To keep runoff water which accumulates on the haul road whhin the haul road system a <br />corrugated metal pips ICMP) culvert or optional highway-grade corrugate polyethylene (PE) <br />pipe culvert will be needed below the haul road at the switchback at EI. 8.090 ft. It is <br />recommended that an 18-inch minimum diameter CMP be used for this culvert. This culvert <br />will convey the maximum 1•foot design depth from the haul roada with 8•inehes of dry <br />freeboard. Taking runoff through the switchback at an approximate 10 percent grade, the <br />culvert was calculated to transport water at 14.1 cfs, above the 3.9 cfs design flow rate for <br />the runoff eamd drtches. The culvert should bs covered with a minimum of 1-foot of cover. <br />Regular maintenance should be employed to keep haul road ditches and culverts clean. <br />Road•cuts in the upper portion of the haul road will primarily be done in bedrock. Because of <br />the competent nature of the outcrops and the existing road-cuts near the site, the road-cuts <br />for the haul roads ware designed to be at 1.SH:1 V slopes. Fills required as part of the haul <br />96266/1424.RPT Cod Mint W~tt~ Bank D~~ipr tar tM s~nbam CnNt MIrM <br />oato0w t sea wEStlec, rne. e <br />