52 RADIOLOGICAL CLEANUP OF ENEWETAK ATOLL = wwe was "A - Se BeBe , : _~_-enaeae = \ ‘ FIGURE 1-53, EVENT KICKAPOO SHOT TOWER, AOMON. OPERATION HARDTACKI: APRIL-AUGUST 1958 Thoughinternational discussions had been opened onthe cessation of atmospheric nuclear testing, the AEC and DOD announced on 15 September1957 that, in the absence of a disarmamentagreement, the US. would continue testing in the Pacific with the conduct of the Hardtack I series, beginning in April 1958. Hardtack I consisted of 34 events, 22 of which were at Enewetak, two in the Johnston Atoll area, and ten at Bikini. Thefirst event of the Hardtack I series was carried by balloon to a height of 86,000 feet and detonated over the ocean about 80 miles northeast of the atoll. This event, Yucca, is not classified as an Enewetak shot since it occurred between Enewetak and Bikini. Three surface events took, place on Runit, and these were to producesignificant effects. Cactus Event formed a crater on the Runit reef, while the Quince and Fig Events caused widespread surface and subsurface contamination of northern Runit. A fourth surface event, Koa, 137 MT, was carried out on Lidilbut, vaporizing it in the same manner that Mike had removed Elugelab. Two events, Wahoo and Umbrella, were conducted underwater, the first ata