Soil gas measurements below foundation depth improve indoor radon prediction.
A soil gas measurement method developed earlier, [Nucl Tracks Radiat Meas, 22(1-4) (1993) 468] was applied to boreholes drilled to below foundation depth. Radon concentration and permeability were measured at 50-cm intervals. In radon prone areas, permeability showed an increase with depth over several orders of magnitude, indicating a low permeability top layer with a thickness of 0.5 m and more. A radon availability index (RAI) was empirically defined and the maximum RAI of each boring proved to be a reliable indicator for radon problems in nearby houses. The permeability of the top layer also proved to be an important factor for a better understanding of soil gas transport and the influence of rain. Implications for radon mitigation are derived.
Johner
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HU
Federal Office of Public Health, Environmental Radioactivity Survey, Fribourg, Switzerland. hans-ueli.johner@bag.admin.ch
Surbeck
H
H