wae It should also be stated that the advantages of the Taongi weather conditions as compared to Bikini, of less rainfall and decreased shower activity are important in diagnostic experimental work as a greater assurance that optical lines of sight will remin open at shot time, especially over long distances. The possibility of transmission interlocks stopping a shot is less likely at Taongi by whatever mrgin of advantage exists in this regard. Fallout As discussed under Item 3 above, and as seen from the JIF 7 interpolated hodographs, the ever present northerly component in the upper westerly winds precludes the possibility of keeping the sand islands clear of contamination at Taongi after the first shot. Past operations have been very successful in being able to continue firing at Fox/George at Bikini and to re-enter selentific stations and to prepare the next shot. Many yards of concrete are required to provide adequate shielding for film data in such stations, in addition to assuring structural strength in close proximity to the blast. The contamination picture at Tacngi wovld be even more discoureging if one had to guarantee re-entry into land stations. The diagnostic ship method rids a considerable portion of the operation of recovery and construction corplications. Another consideration at Taongi concerns contamination in the lagoon and the effects on barge mooring operations in case of no reef break-through on the first shot. Taongi lagoon hes en average depth of only 50 feet and possesses an extremely small tidal prism volume. At the present time, it is estimted the half life of the lagoon water in exchange is 180 days, This figure, elthough large, is not so surprising when it is remembered that Taong} iz totally land locked. The 8 knot current in the channel at low tide arises from the fact that the reef is continuous except for Pokaakku passage and this outflow is not enough to allow the legoon level to equalize with that of the ocean. It is estimted thet the minimum difference between the two is in the range of 810 inches. In the case of reef break-through on the first shot, the srall lagoon volunc becomes a beneficial factor since the exchange rate, once the tidal flow through the crater comes into action, would increase tremendously. It is feit that the crater proper from a 1 - 2 megaton first shot on the reef would clear itself for re-entry faster than either Enivetok or Bikini. The storage of radioactive contaminant in any flowless stagnant pot holes below an intermediate current return layer is being looked at very carefully. Measurements of the wertical mixing, and establishment of the surfece and sub-surface current patterns will reveal any possibility of such storage. These are all factors bearing on the choice of zero points. The feasibility of building a model to aid in thcse determinations is being investigated. Copy Lin, f°/D0¢ Re