To develop a conservative estimate of the impact of adding an additional 10 Ci of plutonium to the Runit Island inventory, one could assume that the plutonium concentration in the lagoon water immediately off shore the northern end of Runit Istand results from terrestrial] groundwater contributions. It is estimated that the plutonium inventory on the northern end of the island (300 m x 250 m) near Cactus Crater is 1.7 curies. Recent data? shows, however, that the plutonium detected in the near shore water is derived from other sources such as the sediments and the reef as well] as groundwater. The estimated plutonium grouncwater contribution,” derived from this recent data,? appears to be less than 20% of the measured near shore concentration. Therefore, if an additional 10 Ci were placed on the northern end of Runit, plutonium concentrations in the off shore water would eventually increase. During Oct. 1975 the 238+240bu concentration in the off shore water of northern Runit was 97 fCi/1. For comparitive purposes, if 10 additional curies of 73%+?"°pPy were present in northern Runit during this period, it is estimated that the off shore water concentration would only be twice as high as the value observed. If it is then assumed that man's only marine diet consists entirely of fish equilibrated with this increased water concentration, the dose to man from this food pathway, calculated as in the 1972dose assessment , would be on the order of a few mrem, 2. Crater Disposal The low tide volume of Cactus Crater in 3.4 x 10* m?. Quantities of soil in excess of this volume will have to be mounded and extended onto the