D. The Aspect of Lagoon Contamination. Prior to the Operation, a considerable amount of study was devoted to the problem of contamination of the shot-atoll lagoon and the possible disruption of surface operations as a result. Con- ’ sidering the shot schedule and the flushing mechanism of the two lagoons (Eniwetok and Bikini), the primary problem of ship operation seemed real only at Bikini. In general, it was assumed that the problem would be more an operational nuisance than a health hazard and that ship operation could begin by H plus 24 hours. The even- tual situation relative to lagoon operation was as predicted except that the bulk of the water transport of fallout was horizontal and downward. Very little, if any, upwelling of radioactive material occurred. On all shots, except | SHOTS (Rud S; , ships were able to re-enter the Enyu anchorages by approximately H plus 6 hours. Following S#or 4, ships were kept clear of the lagoon until shot day plus 1 and following (swor 53 re-sntry was delayed until H plus 10 hours. , For additional infcrmation concerning CASTLE radiological safety, refer to the JTF SEVEN Final Report, RadiologicalSafety, | Operation CASTLE, dated August 1954. 197