Geologic hazards of Castle Valley, Grand County, Utah (OFR-238)

By: W. E. Mulvey

Castle Valley is in a rapidly developing region experiencing high growth rates. To address development in areas with the potential for geologic hazards, the Castle Valley Planning Commission requested the Utah Geological Survey (UGS) to conduct a geologic-hazards investigation of Castle Valley. This information will be used to help guide development and reduce losses from geologic hazards.

Geologic processes that created the rugged and scenic landscape of Castle Valley are still active today and can be hazardous to property and lives. Erosion by running water is the most active and potentially damaging process. Runoff from summer cloudburst storms along Porcupine Rim concentrates in drainages that flow into Castle Valley, causing debris flows and flooding on alluvial fans. The cliffs of Porcupine Rim are source areas for large rock falls which can travel far out onto the alluvial fans below the cliffs. Sandy soils along Castle and Placer Creeks are susceptible to piping and erosion. Large areas of the northeastern part of the valley contain expansive clay soils. Valley-floor alluvial deposits may be a source of radon gas. Collapsible and gypsiferous soils, and ground-water contamination may present problems for development in Castle Valley.

Maps of these hazards (1:24,000 scale) are designed to assist homeowners, planners, and developers in making informed decisions when building in Castle Valley. The maps show areas where hazards may exist and where site-specific studies are advisable prior to development. The maps are for planning purposes only, and do not preclude the necessity for site investigations. Site-specific studies should evaluate hazards and, if necessary, recommend hazard-reduction measures. The studies must be prepared by qualified professionals (engineering geologists, geotechnical engineers, hydrologists).

Other Information:
Published: 1992
Pages: 31 p.
Plates: 4 pl.
Scale: 1:24,000
Location: Grand County
Media Type: Paper Publication