Radon-hazard potential of the southern St. George basin, Washington County, and Ogden, Weber County, Utah (SS-87)

By: B. J. Solomon

Radon derived from the radioactive decay of uranium migrates in soil gas and, after penetrating foundation openings, can accumulate indoors in sufficient quantities to pose a health hazard. Geologic factors that influence radon emanation and migration, including uranium concentration, ground-water depth, and soil permeability, are readily quantifiable through rapid field surveys and data analysis. Hazard maps constructed from overlays of each specific factor define the relative potential for elevated indoor-radon levels in the southern St. George basin and Ogden Valley, Utah.

The radon-hazard potential of the southern St. George basin is highest south of St. George, where uranium levels are relatively high and either ground water is deep, soil is permeable, or both. Uranium levels are greatest in shale of the Petrified Forest member of the Triassic Chinle Formation and associated residual soils, and are also high in granular soils of the Virgin River floodplain and fine-grained soils of the Washington Fields area. The radon-hazard potential of Ogden Valley is highest northwest of Eden, and in smaller areas east of Eden and near the head of Ogden Canyon. As near St. George, a combination of high uranium levels, deep ground water, and permeable soil are characteristic of high-hazard areas. Uranium levels in Ogden Valley are greatest in Quaternary alluvial-fan, fluvial, and lacustrine deposits derived from the Tertiary Norwood Tuff, and are also high in similar deposits derived from low-grade metamorphic rocks, carbonaceous mudstone, and granitic diamictite of the Precambrian Formation of Perry Canyon.

Other Information:
Published: 1995
Pages: 24 pl.
Location: Washington and Weber Counties
Media Type: Paper Publication