This publication, a 1:50,000-scale geologic hazard map with text, identifies locations susceptible to collapsible soils and subsidence that is related to the dissolution of evaporite minerals along the Lower Roaring Fork River Valley corridor. The corridor extends from the town of Basalt to Glenwood Springs at the confluence of the Lower Roaring Fork River and the Colorado River. Large parts of the corridor are underlain by the Eagle Valley Evaporite. This map provides detailed information on locations of surficial soil deposits that are susceptible to settlement, locations of known collapsible soil occurrences, shallow and exposed evaporite bedrock, and sinkholes and other karst phenomenon. The map also describes the geologic conditions, the potential hazards and risks, and engineering and mitigation techniques.
Historically, ranching was the dominant land use in the area and the hazards listed above caused only relatively minor problems. Recently, rapid development of the valley and its surroundings has fundamentally changed traditional land uses, resulting in higher public exposure to these hazards. To reduce the associated risks, it is necessary to understand these hazards and where they occur. Appropriate levels of investigation, engineering design, and maintenance practices are needed to mitigate these hazards for existing structures and new property and infrastructure development.
Meant as a guide for landowners, planners, municipal and county land-use regulators, and the geotechnical and civil engineering community, this map is a tool for formulating appropriate and proper types of investigation in the Roaring Fork River Corridor. 1 color plate (1:50,000). Digital PDF download. MS-34D