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002099 Summary April!May, resulted in up to 300 percent nrnmal snowpack in many areas of Colorado. Sudden warming in early June led to rapid snowmelt, groWld saturation, and several slope failures at Aspen Highlands, most noteably near the Moment of Truth Catwalk and Goldeo Barrel Trail. Continuous alluvial fans and debris fans at the base of the upper Aspen Highlands ridge indicate that the slopes above them have been subject to debris flows and debris avalanches. Under extreme precipitation, almost any colluvium in drainages fronted by an alluvial fan could be mobilized into a debris flow. In addition, rockfall hazards exist where steep bedrock cliffs occur immediately upslope of talus deposits, with downslope limits of these hazards varying according to the size of the rockfalls. Atypical bedrock ridges and troughs are found in the highest elevations of the ski area, and are inferred to result from slow, deep-seated gravitational spreading (sackung) of large parts of the mountain mass. Such deep-seated movemeots are expressed by venical movement along fault lines and by tensiooal opening of fissures. Gravitational spreading occurs in the Loge Peak, Olympic Bowl, and upper Highland Bowl areas. Soil and talus creep are not especially dangerous geologic hazards since they are slow and restricted to upper parts of colluvial or residual mantles. Surface development is relatively immune to damage by soil creep because foundation elements penetrate below the active layer. The soils at Aspen Highlands can be broadly classified into five groupings: I) deep alluvial soils developed on river floodplains, terraces, and on the rolling moraine and outwash landforms at the foot of the ridge; 2) soils developed on lateral moraine, alluvial fans, and debris fans: 3) soils developed on relatively thick colluvium on the slopes of the ridge crest below the Midway: 4) steep forested parts of ridge flanks with soils developed on thin rolluvium and residuum; and 5) soils developed on residuum on the very steep, rocky, unforested slopes near Highland and Maroon bowls plus rock outcrops and rubble land. Revegetation poteotial varies from high to limited and in areas of high surface erosion, some surface stabilization treaunent is needed to ensure regrowth. ENVIRONMENTAL CONSEQUENCES Under the No Action Alternative, the conditions and management of geologic and soil resources at Aspeo Highlands would not differ from the existing conditions or naturally occurring changes. No developmeots have been authorized where gravitational spreading appears to be occurring. The Cloud Nine Lift replacement could affect the area near the Golden Barrel slides, but impacts could be minimized through proper revegetation effons. Under Alternative B, gravitational spreading may affect the stability of the top terminals of the Steeplechase, Highland Bowl, and the Maroon Bowl lifts as well as some of the higher towers of the Highland Bowl Lift and the foundation of the new PHQ near Loge Peak. The bottom tenninal of Highland Bowl Lift may also be affected by slow talus creep. The Steeplechase, Highland Bowl, and Loge Bowl catwalks traverse slopes averaging 60 to 70 percent and all three could be affected by landslides if upslope cuts undermine dipslopes that they cross. Rockfalls may also occur along some sections of the Loge Bowl Catwalk. Due to the widespread distribution of slopes exceeding 40 percent, severe or high erosion hazards exist for at least part of all lift lines and catwalks proposed in Alternative B. Bulk movement hazard is less of a problem but is also high for 67 percent of the Maroon Bowl Uft alignment. Only 14 of the soil typeS that would be affected by snowmaking would have a high erosion hazard but the potential for slope failure occurs if snowmelt runoff is concentrated onto slopes with saturation-prone soils, especially the Leadville and possibly Scout type soils west of the ridgeline. In addition to the Steeplechase and Highland Bowl lifts, gravitational spreading could also affect the Highland Surface and Ridge Surface lifts and the Loge Peak restaurant, under Alternative C. The Highland Bowl and Loge Bowl catwalks would face the same potential dipslope failures as under Alternative B, but the Temerity Catwalk would not be affected by any geological hazards. The Lower Temerity maintenance road would cross very steep colluvial terrain, especially where it traverses the Castle Creek Valley wall, which would result in deep roadcuts that could undermine slope stability. High erosion hazards associated with slopes exceeding 40 percent would affect the Highland Bowl, Temerity, Lower Temerity, and Loge Bowl catwalks in a similar way as under Alternative B. Since additional snowmaking would be less under Alternative C, the added risk of soil saturatioo related slope failure would be much lower than under Alternative B. See/ion III Geology and Soils 15