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• Roadside Borrow Area Drainage North Portal Haul Road No. 2 Drainage into Coal Canyon Calculation Rational and Results Summary Rational: Calculated using SEDCADT"' 4 for Windows Areas, slopes and flow paths obtained from electronic media. ~1 LJ • The soil map, Exhibit 23 shows the soil type as 66 - "Torriorthents, Warm-Rock Outcrop" and 4 "Barx Clapper complex". Generally the soil samples for this and other disturbance areas indicates the soil is sandy to silty loam (Tab Section 9) which equates to a "B" soil group. Clapper has a published soil group of "B" in Table B-1 of Peak Flows in Colorado. The following CN's were used in the calculations: Roadside Borrow Area 64 - B soil group, sage-grass with 20% cover. 86 - B soil group, fallow, bare soil. Used for topsoil piles, ponds and reclaimed slopes. North Portal Haul Road 89 -Curve No. Used in Appendix 13-1 for road ditches. 10 year 24 hour storm event of 1.4" used for all run-off calculations The ditch layout and sizing for the Roadside Borrow Area are presented on Exhibits 6C and 26. The ditch segments, "O" & "P" were designed the same based on the largest of the three drainage areas. Ditch sizes are shown on Exhibit 26 and on pages 14-6-108 & 109. The North Portal Haul Road No. 2 V-ditch flows into Coal Canyon on a 2H:1 V slope at the location where the dip section was removed. The ditch is located immediately south of Coal Canyon and North of Excel's dozer shed and fueling station. Ditch layout and size are presented on Exhibit 6C and on pages 14-6-115 & 116. The SEDCAD ca 117 were preparF presented is true Icul~b a ~fi~~~,grmation presented on pages 14-6-103 through 14-6- ~ ~,,tf~~nonth of September 2002, and the information ;d °c~`r° ~ °~,ro~`trect to~~°f3i~st of my knowledge and belief. ;~+%° Jas Eoaver, P.E. t5ate ~st~re,~t~~essional Engineer rado No. 19230 14-6-103 (New 09/02)