The technical backup for the guidance and additional (EPA, 1977a). consideration of the size distribution of plutonium in soil are given in EPA, 1977b. The on-site and off-site areas of the Rocky Flats Plant contain elevated levels of plutonium from past operations (Krey and Hardy, 1970; Poet and Martell, 1974; and DOE, 1977). Several investigators and agencies have applied various soil sampling techniques in the environs of Rocky Flats. These include: 1. Krey and Hardy (1970): Collected samples for inventory determina- tion by auger, bore, or template techniques for the 0- to 5-cm or O- to 20-cm interval (generally a 620-cm* area). Poet and Martell (1972): Collected samples from the top 1 cm by a spoon technique (1,000 em*). Also collected depth profile samples. Rockwell International, contractor for the Department of Energy at Rocky Flats (1977): Collects 0- to 5-cm samples using a steel 10by 10-cm template and scoop for removing the sample. composed of one (100 cm?) to five aliquots. Samples are Colorado Department of Health (Colorado Department of Health, 1977): Collects surface samples from top one-eighth inch (0.32 cm) using a 5- by 6-cm template and scoop designed for controlling the sampling depth. The samples are composed of 25 subsamples (750 cm?). Jefferson County Health Department (Johnson et al., 1976): Collects samples by sweeping the loose material from a 2- by 2-m area. Neither the total material from the area nor the material to a fixed depth is collected. This material is then treated to disperse particle aggregates, and sized using sedimentation techniques. Because of differences in techniques and associated results and the forthcoming proposed EPA guidance, EPA was requested to participate in a joint study with a number of the previously named investigators. The objectives of the cooperative study were to: 1. Evaluate different soil sampling techniques to determine the best technique as related to health effects. Determine the relationships between soil and air sampling techniques. Determine applicability of techniques to different environmental conditions. Evaluate sampling techniques as related to EPA guidelines. 647