Soil SamplingSoil samples are collected every two years from 12 offsite locations (four Distant and eight Boundary) (Figure 12). Five points were sampled at each location within a 10-m by 10-m grid. At each point two discrete depth intervals: 0 to 5 centimeters (cm) (0 to 2 inches [in.]) and 5 to 10 cm (2 to 4 in.) were sampled. Samples from each depth at all five points were combined to make two composite samples: one for the 0 to 5 cm (0 to 2 in.) depth interval and one for the 5 to 10 cm (2 to 4 in.) depth interval, for each location. Samples were analyzed for gamma-emitting radionuclides, 90Sr, and certain actinides.
Figure 12. Onsite soil sampling locations. Americium-241, 239/240Pu, and 137Cs were measured in all but two samples (Howe split and Mud Lake) above their respective 2s concentrations. Plutonium-238 was detected in all samples above the 2s value, while 90Sr was absent in three samples (Blackfoot, Carey, and FAA Tower). Cobalt-60 was also measured above the 2s value in two samples (Atomic City and Mud Lake #1). The sample and duplicate from Howe also had 238Pu above the 2s concentration. Review of the geometric mean areal activity for radionuclide results showed that 241Am and 239/240Pu were above the long-term average concentrations for this area (Figure 13). All results were within the range of historical concentrations. Results for gamma emitting radionuclides (137Cs and 60Co) are included in Appendix C, Table C-12, while the transuranics are presented in Table C-13.
Figure 13.
Geometric mean areal activity of surface soils (0-5 cm [0-2 in.]). |
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