EXTREMELY HIGH INDOOR RADON ON THE PETERS CREEK SCHIST IN VIRGINIA

Soil permeability and soil radon serve to define the indoor radon potential over the Peters Creek Schist, a quartz-rich polymetamorphic unit in northern Virginia. Based on a year of seasonal (3 month) indoor radon measurements in almost 250 homes, the USEPA's Maximum Contamination Level of 4 pCi/L (for home buyers) was exceeded in more than half of the homes (winter average=5.6 pCi/L, spring and fall @ 5.3 pCi/L, and summer average=4.0 pCi/L. New home construction is active in this area, and some builders have installed passive radon mitigation systems (causes modest radon mitigation) or active sub-slab remediation (lowers indoor radon to less than 2 pCi/L in most homes). Good correlations between indoor radon and aeroradioactivity (total gamma) maps make it possible to avoid some areas during home construction.