Initial Subsurface Characterization and Cleanup Several areas of Irene, shown in Figure 7-49, were suspected to contain subsurface contamination. The investigation of these areas for possible "pockets" of contamination began in mid-November 1977 with a series of auger core samples. All the suspect areas on the main island were sampled as shown in Figure 7-52, as were points P-1 and P-3 on the Helen spit. Cores were taken in 20 em increments, and R/h readings taken at 20-cm intervals in the core holes. The soil samples were scanned in the field for alpha activity to determine which ones would be brought to the lab for further analysis. (This procedure was later changed to eliminate the hole-logging, and all samples were submitted to the laboratory for gross alpha and/or gamma analyses.) The results showed definite subsurface contamination at location 13-N-1, and another set of auger samples was taken near 13-N-] in December 1977. The new data confirmed the earlier results and showed that more investigation was necessary. The sampling method was then changed from coring to profile sampling of a 5 em increment from each 20 em interval in the sidewall of a backhoe trench (see Section 6.9). This method was used for the next set of samples, taken in mid-February, which again covered all the suspect areas plus extra locations near 13-N-1 (see Figure 7-52). These samples again showed the subsurface contamination at 13-N-1 as well as some elevated subsurface activty at 10-BL-0, 10-N-1 and 11-S-4. No other areas showed significant subsurface activity, so an intensive profile sampling program was begun in March 1978 to define the extent of the activity in these four locations. No more contamination was found at 11-S-4, so the investigation at that location was dropped. The subsurface contamination near 10-BL-0/10-N-] covered too small an area to require cleanup, but boundaries of soil to be excised were determined for the 13-N-l area. Figure 7-53 shows these boundaries and also the locations sampled near 13-N~-1 and 10-BL-0/10-N-1. The sampling was completed in August 1978. Removal of the contaminated subsurface soil began in early December 1978. The delay from August to December resulted from an effort to avoid disturbing a large rookery of nesting sooty terns in the area near 13-N-l. Mid-Pacifie Marine Laboratory (now Mid-Pacifie Research Laboratory) made a study of the birds and concluded that the youngest chicks would be fledglings by December. Thesoil excision was therefore delayed until then, when the birds would be able to tolerate the noise and disturbance of cleanup activities. The excision was begun by pushing the contaminated soil into large mounds to await stockpiling. The soil in the excavated area was then sampled, and several places which required more excision were discovered. The soil in those places was removed in January 1979 as part of the stockpiling process. In mid-February 1979 the entire lift area was again soil-sampled and also measured with the IMP, and these data showed that more soil required removal. Another lift was made in late February of 1979, and soil samples taken 12 March again showed some TRU activity in excess of 160 pCi/g. In order to speed the cleanup process, soil samples were taken immediately after the next lift on 22 Mareh. Only the soil shown by these samples to have TRU activity greater than 160 pCi/g was removed in the next lift on 24 March, and samples were again taken immediately after that lift. For the final lift, on 30 March 1979, a method was devised to use handheld instruments to estimate TRU activity in the field while the excision was immediately to areas requiring more lifts, and below 160 pCi/g using this method. The entire reared with the IMP to confirm that no pUl/g. in progress. The operation could then be directed TRU activity in 13-N-1 subsurface area was reduced excision area and the beach stockpile area were then 0.5 hectares (ha) average TRU activity exceeded 80 This phase of subsurface cleanup on Irene was completed 26 April 1979. An estimated 2,450 cubic meters (3,200 cubic yards) of soil, containing an estimated 0.6 Ci of TRU activity, were removed from Irene during this phase. removed. Figure 7-54 shows the boundaries of the area from which soil was Fission Product Sampling and Final Subsurface Cleanup irene was sampled on the 50 m grid for the Fission Product Data Base Program (FPDB) in support of the dose assessment (see Section 6.11). Samples were taken at 53 locations, and soil from 15 of them was analyzed for 9%Sr. The Helen spit was not sampled because its unstable geography makes 266