h soil Cleanup Operations 341 um time possible for a 30-day period. Thefilters operat ed for the maxim hanged at |-week intervals. The main limiting factor to the air were © ling program was the weather. Since rain often damaged thefilters ae was desired to sample the air during the season when maximum an ension of beryllium occurred, the beryllium air-sampling program eogun during the dry season. Approximately 24,000 cubic meters of sent to the were sampled. One-month samples were composited and Texas, AFB, Brooks tory, Labora ‘ecupational and Environmental Health per ium for gnalysis.? All results were less than 0.001 microgramsof beryll cubic meter of air, the minimum detectable concentration, well within . !° established limits ENJEBI SOIL CLEANUP Enjebi is the largest island in the northern portion of Enewetak Atoll, the political subdivision controlled by the iroij (chief) of the dri-Enjebi. With an area of 290 acres, it is the second largest island in the atoll. Cleanup of debris on Enjebi is described in Chapter 5. Soil cleanup work was complicated by a numberof factors. Enjebi was the site of the first test at Enewetak Proving Ground, the X-Ray event, on 14 April 1948. The Easy and Item tests of Operation Greenhouse also were conducted on this island. During the Hardtack | Operation in 1958, seven tests were conducted from barges in the lagoon near Enjebi. The plutonium-239 concentrations found in the 1972 radiological survey ranged from 0.08 to 170, with a mean of 8.5 pCi/g. The geographic distribution of plutonium-239 did not show any systematic pattern, and the depth distribution showed considerable variability from location to location. Most distributions displayed a rapid decrease in activity within the top few centimeters, with leveling off occurring as depth increased. Some deviations from this were noted in NVO-140. The geographical distribution of strontium-90 and cesium-137 did not show a systematic pattern either. Elevated amounts of radiation from cobalt-60 were evident in one area; however, the level was not alarming. Records of nuclear test-related activities which affected soil cleanup were incomplete; however, soil profile samples indicated the same marble cake effect (swirls of clean and contaminated soil) which appeared on Aomon and Runit. Some standard assumptions were made; e.g., that burial of contaminated material occurred at all surface GZs. This was evidenced by the presence of mixed sand, paving material, and concrete, as well as by elevated levels of plutonium. Records indicated that some contaminated areas had simply been paved over with asphalt. 7