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~; -,. ~% ARCO Coal Comp Perm ils an mplia nce Group 555 Seventeenth Street Mailing Address: Box 5300 Denver, Colorado 00217 Telephone 303 575 7500 ~~I ~II~I~II~~~~~~~~ (~ ~ ` n 999 CEP ~ u 1981 September 30, 1981 Mr. Tom Cillis Reclamation Specialist Mined Land Reclamation Division State of Colorado 1313 Sherman Street Denver, Colorado 80202 Dear Mr. Gillis: In regard to Stipulation PIo. `~ "Prior to placement of drainage culverts, ARCO Coal Company shall submit to the Division by September 30, 1981 a revised design for .Pipes 10 and 11 which provides sufficient flow capacity to prevent ditch overtopping". The following explanation will clear up the concern over these culverts. Pipes 10 and 11 are shown on Drawings 9 and 7 of Exhibit 3.l.l.D. The invert elevation of elevation of this culvert is 6121.00 and is located at Station 8 + 32 of the access road. Drawing N14 shows that the centerline of the road is at elevation 6124.9. It would appear that there is only 48" of freeboard which conflicts with Table 7 of Exhibit 3.3.1.A which requires 61" of freeboard. It is important to note, however, that this portion of the road is on a curve and is therefore "superelevated". Since the centerline of the road is 61211.9 and has a 3o cross slope normally, the elevation of the northermost shoulder is 6124.5. To determine the elevation of the southernmost shoulder of the road at that station, one must determine a factor "E". E = 0.0075 x Degree of Curvature = 0.0075 x 8.8067° = 0.066 The elevation of the superelevate shoulder is determined as follows: Elevation of South Shoulder = Elevation of north shoulder plus E x Width of Road = 6124.5 + (0.066)(24') = 6124.5 + 1.584 = 6126.1 Feet •RCO Coel Company ie • Dirialpn of •Venl¢Rlc nlle lO Company fJINED LAND RECLAMATION Colo. Dept. of Natural Resources 1`'~ h~~' v S P' 35 which reads ,~aco.a:or