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at the north end of the lease where alluvial sediments exist <br />• within the Terror Creek drainage area (Morrell Cow Camp). <br />The occurrence of ground water within the Mesaverde <br />Formation is limited to occasional accumulations of <br />localized, perched water in more pervious, lenticular beds <br />such as sandstones. The study area is a potential recharge <br />area. <br />The ground water conditions are dealt with in detail in <br />Section 3. 3. <br />2.9 LANDSLIDES <br />The areas underlain by the Mesaverde Formation are <br />known to contain landslides, mudflow deposits, potentially <br />unstable areas, areas of rockfall, and other features that <br />can generally be classified as stability problems. GEO-FIYDRO <br />(1983) has shown that major stability problems in the <br />tesaverde usually occur along the valley sides where the <br />formation dips into the valley; at the location of the <br />proposed lease, the formation dips several degrees into the <br />mountain (toward the north). The probablity of slope <br />stability problems in such geologic conditions is much more <br />limited. The North Fork Gunnison River north slope, where <br />the surface facilities of the Orchard Valley Mine are <br />• located, is a classical example of such conditions; the <br />slope is relative very stable. <br />The stability conditions of the valleys of several <br />north-south trending tributaries of the North Fork (East <br />Roatcap Creek, Stevens Gulch and two unnamed creeks east of <br />Stevens Gulch) are strikingly different. Large landslides <br />have developed on both sides of these tributaries. They were <br />first identified by Junge (1978) as shown on Plate 8. In <br />addition to his stud y, GEO-HYDRO inspected the lease area to <br />assure that no other important instability features are <br />present within the proposed lease area. <br />The inspection a•as performed during early June, 1983; <br />because of adverse climatic conditions, it was not possible <br />to inspect al l the area as the access roads were muddy and <br />sometimes interrupted by sloughs or larger landslides. The <br />inspection cannot be regarded as a definitive evalua*_ion of <br />all landslides in the area; such a detailed evaluation is <br />clearly outside the scope of the subsidence study. <br />L <br />-9- <br />