C. W. Shilling, M.D. “2= October 30, 1958 III. Rehoboth oceanographic survey. This program was designed to follow the distribution of radioactivity in water, plankton and fish following a Hardtack event. Hydrographic data to accompany the radiobiological data were provided by ONR and the Hydrographic Office. Sea water monitoring was carried on by the Naval Medical Research Institute and was supported by an AEC contract. All of the objectives were not attained because of contamination fromother tests both before and after the event being studied. The Rehoboth is a Hydrographic Office vessel. IV. Collete oceanographic survey. The Collete survey was of the restricted area established for the Hardtack series. As the Hardtack program in the Pacific came to an umexpected early close the plans for the post test survey were moved forward nearly a month. , Information on the radioactivity of plankton and of water by depth and by station was radioed from ship to Eniwetok and relayed to Gordon Dunning for the evaluation of hazard. In general, the activity increased from southeast to northwest, the levels of highest activity being found north of Bikini and Eniwetok and somewhat to the west. The Collete is a U.S. Navy Destroyer. V. Silverstein oceanographic survey. The Silverstein survey was an extension of the Collete survey from the restricted area westward to Guam, a distance of about 1100 miles from the Pacific Test Site. In addition to collecting samples of water, plankton and fish, work aboard ship included beta counting and gamma ray spectroscopy of a limited number of samples. The levels of radioactivity were similar to the levels observed in the 1956 Marsh survey that was made at relatively the same time in relation to the testing period. However, in 1958 radioactive samples were collected somewhat farther to the westward, A “hot spot™ that was observed during the Collete survey was believed to have been observed during the Silverstein survey 30 days later at a point 240 miles farther to the westward, a rate of advance of about 7.3 miles per day. The Silverstein is a U. S. Navy destroyer. VI. Off test-site atolls. In addition to samples from Eniwetok, Bikini and Rongelap samples of natural food items have been obtained at outlying atolls where weather stations had been established. These include Wotho, Kapingamarangi, Ujelang, Ponape, Utirik and Tarawa. From these samples information, either positive or negative, on the geographical distribution of fallout may be obtained. ec: Dr. Dunham Dr. Dunning Dr. Boss Dr. Seymour pos ARGHIVES