asthe D+1su_— , does not indicate comparable dose rat The aircraft encountered active fallout and became contaminated. A replacementaircraft was flown to the survey area. This also became contaminated. At no time was the level in the aircraft allowed to exceed 20 mr/hr. Both aircraft on the D + 1 flights (Figure 3.11) were also lightly contaminated. Active fallout was encountered 100 miles northwest of Bikini at H+ 30 hours. The northwest sector was closed, as far as aerial surveys on D+ 1 were concerned. As indicated on the chart, it was not possible to close the isodose plot at that time. The project had four aircraft to choose from for the D + 2 flight, all reading a background of approximately 0.1 mr/hr inside the detector shielding. The survey for this day could not detect any surface contamination reading above a minimum detectable limit of 0.25 mr/hr at 3 feet from the surface, Table 3.4 summarizes the fallout distribution. TABLE 3.4 SUMMARY OF FALLOUT DISTRIBUTION, FLATHEAD Isodose Area mr/hr mi? 383 908 3,350 11,000" Difference Area Average Contamination mi? mr/hr me 383 525 2,442 7,650* 0.368 0.148 0.074 0.037 D+1 0.2 0.1 0.05 0.025 56 31 73 115 275 mc at H+ 24 hours * Based on estimated position of isodose line. The EOB is roughly estimated and may not be representative of the actual extent of thesefntamination. 3.3.4 Shot Mohawk. A survey of the islands of Eniwetok Atoll was flown on D+1. The island readings are shown in Figure 3.12. The readings are referred to 3 feet above the surface of the islands by a factor of 5.8 for the 300-foot flight altitude (Figure 1.2). Sites Fred and Elmer were excluded from the survey pattern, because a 300-foot flight altitude would have interfered with the air traffic in the vicinity. The open-sea aerial survey could find no detectable contamination in the area searched (Figure 3.13). ings in mr/hr. 3.3.5 Shot Navajo. A background survey was made on D—1 day to determineif the hot intensities, reported by Project 2.62, adjacent to the reef after Shot Flathead, could have come from contaminated water crossing the reef. This flight (Figure 3.14) subsequently became a D-3 survey because of postponement of the shot. The next flight (Figure 3.15) became the D-2 survey, again because of a postponement. The aircraft flight, on the day which would have resulted in a D-1 survey, was not completed because of malfunction. The background surveys were coordinated with a Project 2.62 ship survey. Because the shape and position of the contaminated area varied from day to day, it is possible that the variation may have been a function of the surface winds. An outline of the area, based on the ship data has been included as Figure 3.16. The agreement between these plots appears good, in view of the 12-hour displacement between the ship and aerial survey. The D-day survey (Figure 3.17) located the estimated upwind boundary. On D+1, the flights covered an area of 10,000 mi’ but did not close the 0.025 mr/hr isodose line in the northwest sector (Figure 3.18). The D+2 chart (Figure 3.19) shows that this isodose extended farther than estimated on the previous days. The narrow 1.25 mr/hr line extending to the wesugigfe ARCHIVE atoll had disappeared. Reef readings have been included in this chart. The summary of the fallout distribution (Table 3.5) indicates considerable instability in the contaminated area during the aerial-survey operations. As experienced after the previous water 35 S| ar