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<br />0033:~4 <br /> <br />The Dowds No.1 landslide consists of two parts: an upper apparently <br />stable one and a lower one which is active, but where movement is now slow. ,,'c: <br />Comparison of changes of water levels in the lower part with rates of movement r <br />will be possible in 1986 with the instrumentation installed in 1985. If these <br />movements correlate with water levels in the slide then a dewatering plan for <br />this landslide should be devised. <br /> <br />A preliminary study indicates that the major Whiskey Creek <br />1ands1ide/earthflow is currently stable with the exception of two local slide <br />areas adjacent to the Interstate highway, One is on the east lobe ~f the <br />major slide toe, the other is centrally located on the toe. The <br />instrumentation on this slide is designed to determine whether small <br />landslides immediately above the highway could be precursors to larger ones in <br />the main Whiskey Creek feature, Such larger landslides could be sufficient to <br />close the hlghway and possibly dam the Eagle River. <br /> <br />Introduction <br /> <br />( <br /> <br />At the request of several local officials and others, and after the <br />Colorado Division of Highways (CDOH) had experienced the partial loss of an <br />approximately 300-ft-10ng section of U,S. Highway 24 between Dowds Junction <br />and Minturn, renewed investigation of the 1andsliding problem that caused this <br />highway loss was initiated in late April 1985" The first on-site work was <br />conducted by CDOH. This work consisted of drilling five boreholes, installing <br />12 electronic distance measuring stations (EDM points), and diverting water by <br />ditching to keep, to the extent possible, snowmelt water out of the <br />landslide. As will be discussed subsequently, this first work investigated a <br />relatively small landslide (hereafter referred to as the "highway" landslide) <br />that is in reality a small component of a much 'larger feature (hereafter <br />referred to as the "intermediate" landslide) which is in turn a part yf the <br />very large older Meadow Mountain landslide shown on the location map, In <br />addition, continued instability of road cuts in three other landslides in the <br />general vicinity of Dowds Junction (Dowds No, 1. Dowds No, 2, and Whiskey <br />Creek landslides), which had not previously been carefully monitored and <br />studied by CDOH or CGS, prompted the cooperative study of 1 andslides in the <br />area by the two agencies. <br /> <br />(' <br />... <br /> <br />The 1 ocati ons of the 1 andsl ides. dri 11 ho1 es, EDM poi nts, and other <br />features on the location map should only be considered ~pproximate and <br />diagrammatic, This is because the scale of the map (1 :24,000) and the <br />generalized topography shown are too inaccurate to achieve this <br />properly, When the high accuracy topographic maps, the compilation of <br />which is in progress, are completed this problem will be resolved in a <br />final report. <br /> <br />- 2 - <br />