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CTL/THOMPSON, INC. <br />CONSULTING GEO7ECHNICAL AND MATERIALS ENGINEERS <br />May 6, 1995 <br />Colowyo Coal Company LP. <br />5731 State Highway 13 <br />Meeker, Colorado 81641 <br />Attvntlan: Mr. Jim IGger <br />Subject: Landslide South of West Plt Pond <br />ViClnfty o} West Pit Fxcesa Spoil Disposal Area <br />Colowyo Coal Mine <br />Moffat County, Colorado <br />Job No. 23,001 <br />Gentlemen: <br />At your request, our Mr. Gray vlsRed the Wast PR Pond on April 12, 1985 to <br />observe the slump movement which hsd occurred a few weeks previous to our visit. The <br />movement consisted of a slide located at the south aide of the Weat PR Pond; west of the <br />toe of the West Pit Excess Spoil Dlsposai Slta (FIfl. 1). Tha purpose of our visit was to <br />help evaluate conditions which may have contributed to the atide, determine if tho elide <br />attacted the stability of the sedlmentatlon pond embankment, and to formulate repair <br />recommendations. We previously observed conditions near the toe of the excess spoil <br />pile during Initial stripping _and drain Installation, which documented two small slides to <br />the southeast of'the current area of concern (Job No, 21,952, letter dated July 30, 1994). <br />This letter summarizes our observations of the current slide, aplnlons regarding possible <br />causes and recommendations for repair. <br />SITE CONDITIONS <br />The approximate location o} the elide Is shown on Fig. 1. A photograph of the <br />slide Is reproduced on Fig. 2. The slide is located at the south side of the detention pond <br />et the base o} a slope In an arse where topsoil was stockpiled. The depth of topsoil is <br />estimated to be about 1 to 5 feet In the slide area. The direction o} slide movement was <br />to the north. Ths slide appeared to be a lateral and downward movement wRh little <br />rotation with a near vertical head scarp. Nesr the head o} the s11de, a "slickensided" <br />claystone surface was visible at the base of the slide mass. The claystone dip direction <br />corresponded with the s11de direction. <br />Several seeps and small soil slumps have occurretl in the natural slope to the east <br />of the slide. This portion of the slope had previously been stripped to bedrock to <br />facilitate lateral drain construction to the West Pit underdraln, and topsoil placed to an <br />approximate depth of 1 s to 24 Inches. Tha slumps were relatively shallow and appeared <br />tv •lnvolve movement o} shallow surnclal soils and re-placed topsoil. <br />NOSdWOHl/110:A9 1N3S <br />