saturation is regarded as permanent, whereas subsequent resaturations are regarded as fully removable by steaming thereafter. Thus, once saturation is achieved, levels between 50 and 100 percent of saturation are maintained thereafter. As steaming removes material that contains contaminants rather than selectively removing contaminant activity, the intensity is not constrained to remain at least 50 percent of the maximum. This occurs when moreintense, fresh contaminants overlie those from an earlier shot, because the former are regarded as fully removable. 2.3 WATER INTENSITY MODEL. The fundamental data needed to apply the CROSSROADSship contamination model to CASTLEare water intensities, Iy, from each shot. Although values of Iy were infrequently reported, they may be approximated from theintensities on islands adjacent to the anchorages and operating areas (from Reference 2), coupled with a measured correlation between land and water readings. Data of 6 May 1954 indicated that, if local fallout from Shot YANKEE dominated the Nan anchorage water intensity and the EneuIsland intensity, a water intensity of 7 mR/hr at H+24 hours corresponded to a 100 R/hr land intensity at H+1 (Reference 8). The contribution of previous-shot fallout to the land and water readings was negligible. Neither the similar fallout deposition from Shot BRAVOonthe area, decaved over two months, nor the lesser Shot UNION deposition, from ten days previous, would have exceeded the order of | percent of these intensities on land or in the water. Therefore, the land/water intensity correlation is taken from these readings without modification. Reference 8 corroborates the derived levels of Bikini Lagoon contamination and indicates their persistence. The data, expressed as water activity concentrations, may be interpreted as water intensities through the conversion from Reference 4 of 1 mR/hr per 1yCi/1. The maximum stated water activities in the Nan anchorage convert to 8.4 mR/hr. In order not to conflict with YANKEEshot-day water intensities reported in the same reference, this valueis taken to apply only after general ship reentry into the lagoon. It likely refers to the YANKEE water intensity on D+1 (when ships reanchored), stated above as 7 mR/hr,orto the slightly higher value of 10.5 mR/hr derived for the Nan anchorage following Shot BRAVO (seesection 2.4). The YANKEE shot-day water intensity data reflect the rapid vertical mixing of contaminants that led to the low ratio of water-to-land intensity that prevailedat the later times of ships’ crew exposures. The decrease from 500 mR/hr at H+4.6 to 22 mR/hr at H+10.8 in the Nan anchorage was almost tenfold greater than that from decay alone, but decay accounts for the 14