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'yJ iii iiiiiiiiiiiu iii 999 TIPTON AND KALMBACH, INC. a..E Pe ~. <crv,~.•L.su~ c .,o~ Ise awn R.,-oc :*~cn C~~NTON w. ,+EVRW G. Pn E51DENi E. R. NIGR[LL,ExEC. VICE RRESID ErvT v. G. DISNOP. VICE PR ESIO ENT O~J~ DE VTSC M.TREPSVPER J. R.TURN ER. SECRETGRT DENV ER,COLORADO 80202 R.,oNE r]o]i s•z~eoal May 5, 1981 Mr. Richard Atkinson Colowyo Coal Company 5731 State Highway 13 Meeker, Colorado 81641 Subject: Stability of the Spoil Fill in Streeter Gulch Dear Mr. Atkinson: C <b~C 1RTIP - DENVER Trv 910~6]1~29a0 On 27 April 1981 and 30 April 1981, I met wirli representatives of Colowyo Coal Company to discuss your proposed change of the configuration of the spoil fill in Streeter Gulch. On the afternoon of 30 April 1981, I accompanied representatives of Colowyo Coal Company (Messrs. McDonald, Brown and Atkinson) to t{ie offices of the OfFice of Surface Mining where representatives of the Office of Suiiace Mining and the Mined Land Reclamation Division were apprized of your proposed change. In this meeting, I stated that it was my opinion that the proposed change in con Figuration would have a minimal effect on the stability of the spoil fill. The purpose of this letter is to confirm this opinion. The configuration of the spoil fill as originally planned starts at a toe elevation of approximately 6588 feet and includes 30-foot wide benches at EI. 6700, EI. 6800, and EI. 6900. The slope between the benches is 3 horizontal on 1 vertical. The material to be placed above the bench at EI. 6900 was to be placed on a flatter slope to EI. 7100. The slope between EI. 6900 and EI. 7100, when measured in a plane that is continuous with the 3:1 slope between EI. 6588 and EI. 6900, was ro be approximately 6 horizontal on 1 vertical. The fill has been completed to this configuration From the roe ro EI. 6900. It is our understanding that the proposed chonge in the configuration is between EI. 6900 and EI. 7300. For the purposes of the stability analysis, the slope between EI. 6900 and EI. 7300, when measured in a plane that is continuous ~.vith the 3:1 slope between EI. 6588 and EI. 6900, is to be approximately 3 horizontal to 1 vertical. After odditionol study, you may determine that some additional berms are to be added which would tend to slightly flatten the slope. Fhe stability of the spoil Fill in Streeter Gulch is the subject of reports prepared by W. A. Wahler 8. Associates, Golder Associates, Inc., CTL/Thompson, Inc., and Tipton and Kalmbach, Inc. The latest and most comprehensive investigation v+as prepared for the Office of Surface Mining by CTL/Thompson, Inc., and the results are shown in a report entitled,