| INP Ie ee 7 eomener , ETT DE ATTEN nee ED AeOeNE In view of the small amount of experience with water surface shots, cautious actions were imperative. Subsequent movements and events on shot day were delayed for approximately one to two hours, a factor of considerably less importance than taking an unnecessary risk with the embarked task force. At H+4, the radiological survey helicopters were launched from the Bairoko. Based on this survey, reentry to the lagoon was set at 1500. The survey covered the eastern and northern islands of the atoll and was conclusive enough to limit scientific recovery to Eneu, Bikini, and Aero- koj on the first day. The survey on D+l indicated that recontamination was limited to the Iroij-Aomen and the Bikini~Eneu sequence of islands. No significant secondary fallout was encountered at Bikini as a result of this detonation. Lagoon water was substantially contaminated with radioactive sediment. D-day readings of 4.2 R/hr were obtained at an altitude of 500 feet 150 meters) over ground zero. (about This contamination moved to the west and southwest, allowing small-boat operations in the area of ground zero. La- goon water movement toward the Southwest Passage increased radiation levels in the vicinity of Oroken, Bokaetoktok, and Bokdrolul. diation intensity on the various islands. Table 44 shows ra- Figure 84 gives the radiation contours at H+l. At 1400, Wilson 3 (and later Wilson 4, flying from H+1l2 to H+26) was directed to make a low-altitude (300 to 600 feet; 92 to 183 meters) at various atolls southeast of ground zero. survey Table 45 lists the results of this survey. During the shot day and throughout the night, secondary fallout was encountered by some of the ships as indicated in Table 46 (Reference 17, Tab N). Enewetak Atoll reported a maximum reading of 0.004 R/hr. Weather re- connaissance flights on D+l to the west, south, and northeast encountered 292