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III IIIIIIIIIIIIIIII <br />999 <br />STATE OF COLORADO <br />DIVISION OF MINERALS AND GEOLOGY <br />Department of Natural Resources <br />1 J13 Sherman St., Room 215 <br />Denver, Colorado 80?03 <br />Phone: 13031 866-3567 <br />FAR: IJ03) 832-8106 <br />March 29, 1996 <br />Mr. Brian D. Gontarek <br />Environmental Engineer <br />The Pittsburg & Midway <br />P.O. Box 6518 <br />Coal Mining Company <br />Englewood, Colorado 80155-6518 <br />J RE: Edna Strip Mine (C-80-001) <br />Technical Revision 34 <br />Dear Mr. Gontarek: <br />I~~~~ <br />DEPARTMENT OF <br />NATURAL <br />RESOURCES <br />Ray Romer <br />Governor <br />lames S. Lochhead <br />Executive Director <br />Michael 8. Long; <br />Drvrsion Director <br />The Division has completed a review of your response to our letter concerning TR 34. As a <br />result of that review, we have the following questEOns and comments. <br />1. P&M's response to our concern regarding drainages (running parallel to the slope) <br />indicated there were only two drainages across the slope. The 1viSlOn agrees that the <br />portions of the South Collection DLtch and the Lower Moffat Road Ditch are <br />appropriate, and should perform well for water collection purposes. However, based on <br />observations at numerous sites, we believe that the points at which water is directed into <br />near 90° turns will not be stable. Please provide adequate information to demonstrate <br />long term stability at those points, or lessen the sharpness of the turns. <br />Downdrain #4, at the lower end, runs parallel to the sloppe. It does not appear that this <br />configguuration is approximate original contour, or will be stable, as reqquued by Rule <br />4.05.3(1)(e). In reviewing Exlubit 3.4-5, the bottom cross-section depic[s a fairly <br />significant departure from original contour. It would appear that if P&M extended <br />Downdrain #4 directly downslope, rather than across the contour, this portion of the <br />reclaimed pit area might be closer to the premine configuration. <br />2. P&M provided designs for Downdrain #3 and Downdrain #4. We have the following <br />comments on the designs: <br />Downdrain #3 <br />a. Please rovide additional information on the proposed channel liner (Landlokl~"' <br />ECRMp450), that confirms its ability to sustain the predicted flow velocity of 11.01 <br />fps. <br />Downdrain #4 <br />b. In the Downdrain #4 drainage area, the topsoil being redistributed on this is <br />coming from the Moffat area stockpile, and is not live-handled rotocleared topsoil. <br />As such, the Division believes a curve number of 91 would be more appropnate. <br />