shielding from the crater's nuclear radiation to the surface operations. Scientific stations were built on Dridrilbwij for CASTLE, the island next to the Eluklab crater, and no mention of special difficulties due to radiation is made in the construction report, although personnel film badges were still required. Bikini was the location of the first postwar nuclear detonation. July 1946, the CROSSROADS tests were conducted in the lagoon. devices were detonated: In Two 23-KT one airburst over a target fleet, and the second burst underwater in the lagoon about 2 nmi (3.7 km) west of Bikini Island. There was no continuing radiological exposure of personnel on the surface at Bikini from these tests, although there was very-low-level contamina~ tion in the lagoon bottom. Special Problems in Oceanic Testing Testing in the Marshalls offered a large uninhabited area for test ac- tivities and for the favorable disposition of the test debris if the winds were in the right direction. However, the area was almost all water, of- fering little dry space to place shot towers, instrumentation shelters, test structures, or places to live. is only about 1,800 acres southeastern quadrant At Enewetak Atoll the total land area (730 hectares), and the prime acreage in the (about one-third of the total) the task force not based on ships. housed that part of The land area of Enewetak Island, the largest of the atoll, is only about 320 acres (130 hectares), and about half of this was occupied by an airstrip and associated activities. Fur- thermore, the land suitable for testing was not necessarily distributed in the appropriate directions and sizes for instrument placement. Lack of land area was one of the factors necessitating use of both Bikini and Enewetak atolls, starting in 1954 with CASTLE. The addition of Bikini also precluded damage to the Enewetak facilities by very~large-yield devices. The lack of land was compensated for in part by civil engineering projects. Causeways were constructed that linked strings of islands to support the long pipe runs of some experiments over thousands of feet. 51 These also