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COLOWYO COAL COMPANY L.P. 5731 State Highway 13 Meeker, Colorado 81841 (970)824-1572 (970) 824-1598 FAX James A. Kiger Senior Environmental Engineer May 7, 1999 Mr. Byron Walker Environmental Protection Specialist Colorado Division of Minerals and Geology 215 Centennial Building 1313 Sherman Street Denver. Colorado 80203 III IIIIIIIIIIIIIIII /~ nennecott /~ . Ener9Y , , -- ., Colfoaryo CoalCompanyL.P, `;~'~ RECEIVED MAY 10 1999 Division of Minerals 6 Geology Re: Colowyo Coal Co. L. P., (C-81-019) Request for Technical Revision No. 48 Modification to the West Pit Fill Postmining Topography Dear Mr. Walker: Attached, please find a request for Technical Revision No. 48 to the Colowyo Coal Co. L.P., Permit C-81-019. TR-48 provides for a modification to the West Pit Fill Postmining Topography. Much of the information contained in this application was discussed during our meeting with you in our office on April 21, 1999 while you were onsite for an inspection. As the Division is aware, many of the natural hillslopes located along Taylor Creek periodically exhibit instability due to inherent, localized geologic conditions. As a result small, surficial rotational failures unexpectantly occur along these natural hillslopes. As you know a couple of years ago one such failure occurred above the east flank of the East Taylor Pond. While the pond embankment has not been placed into jeopardy, we have had to reconsider the postmining topography to insure the long term stability of the area. In addition, careful review of the post mining topography in the vicinity of the east Taylor pond also indicated we needed to correct a computer generated mapping error. The 102 dragline is scheduled to walk into the West Pit in the fall of 1999. By January, 2000 the dragline will have completed Cut 1 and will walk to the spoil side of the pit. In doing so it will ramp up to near the East Taylor Pond. At this time the dragline will remove the slide material and reshape the hillsides near the slide. The relocation and flattening of these postmining _ contours reduces the amount of backfill spoil material which would have otherwise been dumped into this area. To make up for the resultant "loss" of dump capacity in this portion of the West Pit Fill (approximately 1.24 mm LCY) we are proposing to compensate by extending the footprint of the Fill to the northeast. Please see the revised Map 19 -Postmining Topography and Exhibit 191b - West Pit Fill Design for details of this change. To attain this revised topography, we also propose to place an additional 3.96 mm LCY of material into the West Pit Fill. Please see the revised Permit page 2.05-36 for a summary of the location of the excess spoil from the Colowyo operation. After revising the Mining and Fill Limits of the West Pit to correspond with As-Builts, Colowyo proposes to place a total of 21.3 mm LCY into the West Pit Fill leaving 9.6 mm LCY to be placed throughout the remainder of the