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_. POWDERHORN COAL COMPANY July 19, 1994 Ms. Erica S. Crosby Environmental Protection Specialist Colorado Division of Minerals and Geology 1313 Sherman Street, Room 215 Denver, CO 80203-2273 RE: N.O.V. C-94-014 Dear Ms. Crosby: iii iuiiiiiiiiii iii sss P.O. Box 1490 Palisetle, COlOratlO 87526 (309) 464-7951 Fax (909) 464-7181 RECFII.~F'4~ JUL 2 51994 L~fV'Si00 of P.1iIIBr~15 a c;r,~rooy. Attached please find a certification for the installation of Pond 11. Excavation of the pond and installation of rip-rap in the emergency spillway was completed on July 19, 1994. As discussed during your inspection, I am submitting additional information that I believe is pertinent to the subject N.O.V. The primary issue is the adequacy of sediment control. Our initial intention was to excavate the pond and haul the dirt away as borrow material. However, the extreme volume of rock encountered at the pond location jeopardized the completion schedule for the pile cover. Therefore, excavation of the pond was suspended when we believed that we had met the absolute sediment control volume requirements for the short term completion of the cover project. These requirements relate to the facts that the design 3 year sediment capacity would not be absolutely necessary during the 3 to 4 week delay in construction and the total design runoff capacity would not be absolutely necessary because less than 4 acres of the design 8.6 acre disturbance had been disturbed. The primary spillway was not an issue for this temporary condition because the pond was designed for pumped discharge. Installation of the emergency spillway was complicated by the need to develop the adjacent drainage channel. This will be discussed further in the following paragraphs. By not having the emergency spillway excavated, the effective capacity of the pond was greatly increased. I estimated that the increased capacity below a 1 foot freeboard was approximately 0.3 acre-feet or 75 percent of the actual design runoff capacity of the pond. Considering absolute capacity requirements, I believe that we would have contained at least a 25 year event. The second issue relates to the time pressure that we were under to complete the pile cover. O.S.M. Closure Order No. 94-020-370-001 (effective 6/29/94) allowed 30 days for completion with stiff daily penalties to terminate the pile cover violation before more drastic measures were taken against our operation. We felt obligated to meet the 30 day