it unsuitable for habitation, agriculture or food-gathering. Tables 7-1, 7-2 and 7-3 summarize the 3%Cs, 90sr and 239,240 py results, respectively, for the 0-15 em average; island average results for other profile ranges are shown below: 0-5 em oS pCi/g 137¢5, pCi/g 34.1 6.10 0-40 cm 38.2 5.8 0-60 cm Total Samples 36.6 5.4 90 317 When the FPDB samples were analyzed for 241 4m, eleven locations were discovered to have one or more samples with TRU activity, possibly exceeding 160 pCi/g. After additional chemical analysis to check the ratio of TRU to 2 lam, seven of the locations were confirmed to have TRU activity exceeding 160 pCi/g. The earlier subsurface investigations, sampling only 5 em of each 20 cm interval, had failed to find these locations, while the FPDB method included samples from the entire 0-60 em profile. The FPDB samples also yielded more specific information about the depth of subsurface activity than the auger core samples, and this information was incorporated in the followup sampling design. Tech Note 18 describes the sampling design that was used to investigate the seven locations with elevated subsurface activity. The new design produced better boundary definition with fewer samples, resulting in a substantial savings in time and effort. The locations investigated with this method, shown in Figures 7-55 to 7-61 respectively, were: 9-S-1, 12-N-1, 6-S-2, 7-S-3, 10-N-I and 14-N-1. After two iterations of soil sampling, it was clear that while 9-S-1 and 12-N-1 would not require cleanup, soil removal was necessary at all the other locations. Horizontal boundaries for the five soil excision areas were determined using the new method, but depths of each excision were based on standard sidewall sampling (Section 4.2.1). The investigation lasted from 3 to 16 June 1979, and soil lifts began 13 June, while two sites were still being sampled; the initial lifts were completed June 19. The excavations were soil sampled 27 June, and only 14-N-1 required more soil removal. Handheld instruments were used to direct the final lift at 14-N-l. The IMP remeasured all the locations, confirming that no 0.0625 hectare exceeded the 160 pCi/g criterion for TRU activity. Because it was too deep to leave open, the excavation at 14-N-1 was backfilled with clean beach sand. After the cleanup operations were completed, IMP measurements showed no 0.5 hectare had average TRU activity greater than 80 pCi/g. This phase of subsurface cleanup ended 14 July 1979, after an estimated 1,350 cubic meters (1,780 cubic yards) of soil, containing an estimated 0.41 Ci of TRU activity, were removed. The results of the FPDB sampling for 0-40 em profile means of 137s and 9%Sp for Irene are shown in Figures 7-62 and 7-63, respectively. Only the main island is included because the Helen spit was not sampled. Final Characterization Following the last cleanup operations on Irene, all the chemical analysis results for soil were compiled to arrive at a final set of ratio of TRU to 241am. Details of the computations and data used are in Tech Note 2.1-B. Four ratios were used for the final TRU estimates: 4.06 + 0.21 for the east end, 6.41 + 0.43 for the central area, 11.27 + 0.38 for the west end “(except the 14-N-1/13-N-1/12-N-2 excision areas), and 7.92 + 0.44for the 14-N-1/13-N-1/12-N-2 excision areas. The boundaries for each ratio population are shown in Figure 7-64, along with isopleths on the post-cleanup surface TRU eee (based on final data). Table 7-4 summarizes the post-cleanup status of Irene for TRU, 37Cs and ©9Co from IMP data. Based on final data, one 0.5 hectare had average TRU activity imag to be 87.7 pCi/g; all other 0.5 hectare averages were less than 80 pCi/g. The island average transuranics value reported in the Certification is 31 pCi/gm for surface soil, and the transuranics classification is Agricultural.