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<br />002786 <br /> <br />1.0 INTRODUCTION <br /> <br />Basis for! Colorado Landslide Mitigation Plan <br /> <br />In Colorado, losses from landslides, subsidence and other ground failures have <br />been extremely high, particularly in recent years. Losses from 1ands1iding in <br />terms of lives, property, and damage to the state's infrastructure (roads, <br />utilities, bridges, buildings) are high enough to significantly impact the <br />state's economy over the near term. If present loss trends continue over a <br />longer term, expected losses will soon be high enough to disrupt the state's <br />economic well-being and the quality of life of its citizens. The potential <br />for higher losses is growing rapidly as urbanization and development continue <br />in Colorado's mountains. The 1976 USGS map shown below indicates the extent <br />of 1ands1iding in Colorado, relative to adjacent states. Most significant <br />1ands1iding events in Colorado occur in the western half of the state. <br /> <br />The landslide hazard in Colorado: There are thousands of landslides in <br />Colorado of various ages and degrees of activity. A preliminary screening by <br />the Colorado Geological Survey ICGS) has identified twelve large landslides <br />with serious potential for very large future losses. About forty additional <br />areas have been identified that have high potential for future debris-flow or <br />landslide events that could have serious local community impacts. Although <br />few lives have been lost as a result of 1ands1iding, the State Department of <br />Highways' budget, as well as many western slope county and city budgets, have <br />been significantly impacted by costs related to lands1iding. Only very <br />expensive earthmoving operations have prevented the East Muddy Creek slide <br />near Paonia Reservoir from permanently closing State Highway 133 (Paonia to <br />Glenwood Springs). When others of the state's major landslides move enough to <br />affect nearby highways, costs will increase significantly. If a major slide <br />blocks a stream, an extremely dangerous "form and fail" dam may develop. This <br />type of natural dam often results in the formation of a lake which is likely <br />to overflow, breach the dam and seriously threaten the lives of downstream <br />residents. <br /> <br />Case study no. I describes the serious potential impacts of the several very <br />large landslides near Dowd's Junction, adjacent to Interstate Highway I-70, <br />just west of Vail. Activation of major sliding across this important life line <br /> <br />- 1 - <br />