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COLC'SJYO COAL COMPANY L. P. 5731%State Highway 13 Meeker, Colorado 81641 (970)824-1572 (970) 824-1598 FAX James A. Kiger Senior Environmental Engineer July 1, 1999 Mr. Byron Walker Environmental Protection Specialist Colorado Division of Minerals and Geology 215 Centennial Building 1313 Sherman Street Denver, Colorado 80203 LIi~~~iiii~iiiiiuiii //- I~viiiivvVL1, ~ .Energy Coloa-yo CoalConr~any L,P. ' :~~0 RECE{VED .lUL 0 61999 Division of Minerals & Gedo~I Re: Colowyo Coal Co. L.P., (C-81-019), Minor Revision No. 51, Response to CDMG April 16, 1999 Adequacy Letter. Dear Mr. Walker: The following information is provided in response to the Division's April 16, 1999 adequacy letter for MR-51. Item 1. - TR's vs. MR's -- Colowyo's intention regarding the permitting process for stockponds was a two phase process. The first step was initiated by TR-38. Our intention was to provide the basic design criteria for a regulated facility (the stockponds) through this initial TR process. Once the initial design criteria, construction procedures and as-built certification criteria were established for these regulated structures through the initial TR process, subsequent stockpond construction would be accomplished through the MR process. The second step (the MR process) is consistent with Rule 1.04(73) because we are dealing with "minor alterations in the location of facilities" rather than a "design change for a regulated structure." Through the MR process we are simply providing additional such facilities throughout the reclaimed area following the design criteria established in TR-38 rather than proposing any design changes to facilities. MR-45 was submitted and subsequently approved by the Division consistent with this procedure. We, therefore, request the Division reevaluate it's position that future submissions be processed as TR's. We believe that for the addition of new stockponds, with designs which do not substantially vary from the TR-38 criteria, the use of minor revisions to add new sites is appropriate and allowed by regulation. Item 2 -Non-Erosive spillways - Item 3 - 25year. 24-hour Precipitation Event Item 5 -Adequate Freeboard -- Utilizing SEDCAD 4 for Windows we have analyzed the capability of the spillways to handle the flow from a 25-year, 24-hour precipitation event without erosive velocities. Additionally, we have looked at the freeboard of the spillways when flowing at a design depth. The SEDCAD runs are attached for your information and may be placed into Permit Exhibit 7 as an addition to Item 11, Small Depressions/Tanks. Although the stockponds are designed to be constructed with a minimum 8 foot wide spillway, for the purposes of the spillway demonstration we used a 4 foot width for an added level of conservatism. The flow information is summarized on the following table.