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PRELIMINARY STUDIES CURTIS L. MILLER III III III III IIII III 507 Park Avenue ENVIRONMENTAL PERMITTING CSM EM '60 (303) 275-2533 DRILLING & BLASTING MINING CONSULTANTS Canon City, CO 81212 HAULAGE 2R January 1987 ~(r. Gregg Squire MLR D, 423 Cetnennial Bldg. 1313 Sherman St. Denver, CO 80203 Dear Gregg: File No. C-037-81 FEQ 2 i°87 At your request, I enclose a revised East pit longitudinal drainage profile showing a 50 ft. transitional 5% channel between the 20% channel at the ext- reme south end of the pit and the 1% channel throughout the remainder of the pit. Also provided are sketch X-sections of the triangular 20% channel, the trap- ezoidal 5% channel, and the triangular 1% channel. The 20% channel will be 4.5 ft. wide X 1.5 ft. deep, and lined with 6" to 12" rip-rap. The first 20 ft. of the trp)nsitional 5% section will be a hydraulic jump basin at least 15 ft. in diameter,%3 ft. deep, lined with 24" or larger rip-rap,. The remaining 30 ft. of the 59e channel will be 10 ft. wide at the top Q ft/. wide at the bottom, and 1.5 ft. deep_ l~in~with 12"+ rip-rap. U The 1% channel will be 8 ft. wide X 2 ft. deep, lined with up to 6" rip-rap. Data used for the calculations of these channel dimensions are: Maximum 10 yr. precipation event = 2.8 in./ 24 hr. Area of drainage basin upstream of the east pit = 35 ac. @ 6% avg. slope. Area of east pit and central ridge reclamation area = 42 ac. Runoff velocity = 11.73 fps. Minimum freeboard = 0.4 ft. Runoff volume = 14.93 cfs. Maximum side slope = 2:1 (tannings N-= 0:03 Calculations to develop channel sizes were based on proceedures in "Applied Hydrology and Sedimentology for Disturbed Areas", authored by Barfield, lJarner, and Haan, published by the Oklahoma Technical .Press. Rip-rap for the channel bottoms will be derived from granitic boulders and cobbles included in the Verdos Colluvium overlying the coal measures in the area. It is felt necessary to extend larger 12" cobbles into the 1% section from the 5% transitional section for approximately 10 - 15 ft.