COMPARISON OF SOIL SAMPLING TECHNIQUES AT ROCKY FLATS D. E. Bernhardt, J. D. Bliss, and G. G. Eadie Office of Radiation Programs U.S. Environmental Protection Agency Las Vegas, Nevada ABSTRACT In May, 1977, a cooperative plutonium soil sampling project was conducted by Rockwell International (Department of Energy contractor), Colorado Department of Health, Jefferson County Department of Health, and the U.S. Environmental Protection Agency-Office of Radiation Programs-Las Vegas. Each of the agencies collected five duplicate samples from four distinctly different pedological and morphological settings around the Rocky Flats Colorado Plant. The sampling techniques included: the Rocky Flats O- to 5-cm depth technique (100-cm? area), the State of Colorado one-eighth-inch depth technique (750-cm* area), the Jefferson County technique (sizing of dust swept from a 4-m* area of the ground surface), and two EPA techniques for samples of 0- to l-em (450-cm2 area) and 0- to 5-cm (500-cm* area) depth. A limited number of depth profile samples, down to 10 cm, were also collected by EPA. The objectives of the project included assessing the variability and reproducibility of the techniques, comparison of the results from the various techniques, determining the applicability of the techniques to different environmental conditions, and assessing how well the techniques reflect the potential airborne hazard for resuspension of plutonium. Results of the various techniques are also to be compared to the proposed EPA guidance for transuranics in the environment (Federal Register, 42:60956, November 30, 1977), which is primarily based on activity in the surface 1 cm of soil. This paper presents a status report of results from the EPA samples collected for this project. The emphasis is on comparing the results from l-cm and 5-cm depth samples. The l-cm technique samples were based on a composite of fifteen 30-cm@ subsamples and the 5-cm technique includes a composite of five 100-cm? subsamples. The preliminary results indicate that about one-third of the plutonium-239/240 activity per unit area detected in the 5-cm depth samples was accounted for in the l-cm depth samples. A limited number of samples for the profile from 5 to 10 cm indicated about 20 percent of 645