center for small boat entries and exits from contaminated areas, the Curtiss the base for entries and exits to device barges and scientific houseboats, and the Estes the information center and entry and exit point for the Commander and his staff. The Rad-Safe Building on Parry
was the control station for scientific activities at Eniwetok Atoll.
Each of the control stations was staffed by a control officer, a clerk, and a poo! of monitors. These monitors acted as reserve monitors in case recovery or construction parties
were unable to furnish a trained monitor.
Communications were maintained between Bikini stations by means of the administrative
radio net and a special Rad-Safe net. Contact with helicopter survey and recovery parties was
established through ship to plane radiocircuits.
4.3
SURVEY RESULTS
Initial aerial surveys were conducted at approximately H+4 hr. This procedure was followed since experience had indicated that initial fall-out would continue through this period.
Land and lagoon areas were examined from a helicopter flying at altitudes between 50 and
1000 ft.
1 L= ERAVO
A partial radiological-safety survey was conducted on G@RAvy day. Results of this initial *
survey were conclusive
enough to cancelall activities except those of an emergency nature for
UkAvd «Beno 1 DAY Intensities ranging as high as 600 r/hr were encountered approxi-
mately7 nat
nauticalmileseast-northeast of Ground Zero (GZ) at H+4 hr. Other readings of 125
r/hr at 20 nautical miles east-southeast of GZ were encountered at H+4 hr. An analysis of
this and succeeding results (Fig. 4.1) indicated that the bulk of active fall-out moved ina
spreading pattern from 60 to 100 deg east of north.
Lagoon contamination, of consequence, was confined to lagoon areas containing suspended
sediment. For the first few days this area was confined to the western quarter of the lagoon.
This radioactive sediment washed over the western reef, out through the southwest passage, or
settled to the bottom of the lagoon in a period of three days. At no time was the anchoredfleet
hazarded by the movement of contaminated water.
Succeeding surveys revealed a drifting of activity. The absence of rain prevented the
leaching of fine particulates; consequently activity tended to decrease on the windward side of
obstacles and to increase in the lee of buildings and bunkers, Surveys also indicated the pres-
ence of very low energy radiation. In many cases a thin liquid layer completely absorbed the
radiation. Tents provided measurable protection, whereas intact bunkers provided complete
protection, Individuals were able to work extended periods in bunkers in high-intensity areas
with little exposure.
The USS Bairoko,approximately 38 miles southeast of the shot site, reported a fall-out of
20 mr/hr at 0804MARVO
DAY, ,and a maximum reading of 1000 mr/hr was reportedon the
flight deck at 0815M.
Eniwetok Atoll reported a maximum fall-out of 3 to 4 mr/hr at 1015M,'GAAVO 2497
Survey parties from the USS Philip found radiation intensities to be 1.5 r/hr at Rongelap
Island, Rongelap Atoll (100 nautical miles east-southeast of GZ) at 03/1045M; 3.0 r/hr at Eniaetok, Rongelap Atoll (100 nautical miles east-southeast of GZ) at 03/1245M; 0.45 r/hr at Enibuk Island, Ailingnae Atoll (75 nautical miles southeast of GZ) at 03/1545M;and 0.41 r/hr at
Sifo Island, Ailingnae Atoll (70 nautical miles southeast of GZ) at 03/1715M,.
Survey parties from the USS Renshaw reported 0,1 r/hr at Utirik Island, Utirik Atoll (275
nautical miles east-southeast of GZ) at 04/1000M.
Intensities of 0.1 r/hr were reported from Rongerik Island, Rongerik Atoll (140 nautical
miles east-southeast of GZ) at 17/1200M by survey parties of TG-7.4.
Task force parties reported intensities of 0.003 r/hr at Likiep Island, Likiep Atoll (270
nautical miles southeast of GZ) at 06/0800M; 0.003 r/hr at Jemo Island (270 nautical miles
southeast of GZ) at 06/1100M; 0.005 r/hr at Ailuk Island, Ailuk Atoll (300 nautical miles east-
24