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--_-_ _ III1111111111111111 ~ Development Consultants, Inc. October 8, 1990 ~ _ l' r6 ^~ Mc Larry Rouue^ (': ~ T 1 ~_ . _ , ) Colorado Mined Land Reclamation Division 215 Centennial Building lyi~,,.,s ~,z..-; 1313 Sherman Street Denver, CO 80203-2273 Reelarnsllot~ L:ivISI0f1 RE: Sedimentation Pond Certification Colorado Coal Mine No. 1 - Pond B -Permit No. C-81-024 Dear Mr. Rouuen Enclosed are 3 copies of certified as built design data for Sedimentation Ponds B and A, Ditch B-A, and Ditch CCMC #1 at Kaiser Steel Resources' Colorado Coal Mine No. 1. These data are based on surveys completed on September 6 and 27, 1990. As shown by the data, Pond B has a cumulative capacity of 9.7 acre-ft to the principal spillway invert. The 10-year, 24-hour event requires 8.5 acre-ft, leaving 1.2 acre-ft available for sediment. The ditch connecting Sedimentation Ponds B and A has been constructed as a "V" ditch, 20 ft. wide at the top and 33 inches deep. The emergenry spillway for Pond A has been enlarged to a width of 37 ft. with a depth of 12 inches below the ground level. In addition, Diversion Ditch CCMC #1, as described in TR No. 11, has been constructed. This ditch is also a "V" ditch. The upper stretch is 16 feet wide and 20 inches deep with a slope of 2 percent, and tttc lower stretch is 14 feet wide and 20 inches deep with a slope of 6 percent. The ditch was field located to minimize disturbance area, which required the grading (reclamation) of approximately 150 feet of the North Interceptor Ditch. This portion of the ditch picked up drainage from an undisturbed area, so taking it out of service does no[ impact the sedimentation control plan. The regraded portion of the ditch will be seeded this Fall. Should you have questions or need additional information, please do not hesitate to call. Very tru/yours, _ L K. M. Kolin Senior Engineer MK/ca Enclosures 5990 Greenwood Plaza Blvd. • Suite 104 • Englewood, CO 80111 (303)850-0930