On the design of a sampling plan to verify compliance with EPA standards for radium-226 in soil at uranium mill tailings remedial action sites

This paper discusses design aspects of a two-stage compliance sampling program being developed to verify that removal of soil at windblown uranium mill-tailings sites are results in 226Ra concentrations that meet Environmental Protection Agency (EPA) standards. In the first stage, gamma scans of surface soil would be conducted over the entire remediated region using a tractor-mounted gamma-ray counting system (RTRAK) to measure 214Bi (Bismuth), which is an indicator of 226Ra in soil. In the second stage, composite soil samples would be collected from a systematic sample of 10-m by 10-m plots, where the number of plots is determined using a compliance acceptance sampling plan. These soil samples are analyzed for 226Ra and compared with the EPA standard of 5 pCi/g above background using a selected statistical rule