Several areas were noted as possible sites of buried contamination based on the 1972 results and prior knowledge. At the Fig-Quince area, strips along both ocean and lagoon sides were suspect, as well as an inland area at the GZ itself. There was also elevated subsurface activity in the lip of the Cactus crater and in the area just south of the crater. Because of the earth-moving activities after the Erie event and the fact that the 1972 data showed some evidence of elevated subsurface activity near Erie GZ, this area also was suspect. Also, during the 1972 survey a jar containing sand with high plutonium activity was reported near the 1310 bunker and a box of contaminated material was reported near the old runway. Initial Characterization and Cleanup During the cleanup, much of Yvonne was covered with roads, buildings, storage yards, and other structures associated with the contaminated soil confinement operations. Therefore no complete initial surface characterization of Yvonne could be done. Instead, IMP measurements were made on the accessible areas of the island as time permitted. Part of northern Yvonne was measured in February 1978, and the undisturbed sections of southern Yvonne were measured in early February 1979. The rest of the accessible areas of northern Yvonne were also measured in February and early March 1979. The ratios of TRU to 24!am that were used to estimate TRU activity from IMP 241am data were based on both data from the 1972 survey and data taken during the cleanup. Soil samples were taken in February 1978 on northern Yvonne, at the locations shown in Figure 7-109. Southern Yvonne was soil sampled in February 1979, as shown in Figure 7-108. The 1978 samples were analyzed only for gross alpha activity and for 241 Am activity by gamma scan, not for plutonium, so only a rough estimate could be made. The ratio, which was estimated to be 9.5, was applicable only to the Cactus crater area. For the Fig-Quince area, 1972 data were used to estimate a ratio of 14.42 + 0.67. For southern Yvonne, data from the 1979 samples were used to estimate a ratio of 8.16 + 0.26. (See Tech Note 2.24 for details.) For the final characterization after cleanup, more soil samples were taken in August 1979 on northern Yvonne, and a ratio of 9.10 + 1.08, applicable to all the north half, was estimated. The Field Radiation Support Team (FRST) conducted several subsurface sampling efforts during the cleanup. In the first effort, an investigation of the Erie GZ area, samples were taken at several depths along several radials from the GZ in July 1977. No significant concentrations of elevated subsurface TRU activity were found. The Fig-Quince area was sampled by FRST between November 1977 and January 1978 using the auger coring method combined with logging of the holes for gamma activity. The purpose of this latter effort was to define, if possible, the boundaries of the area containing buried Quince material. Although a number of locations with very high subsurface TRU activity were found, no continuous boundary could be established. Auger core samples were also taken by the FRST on the Cactus eraterlip. As the Cactus crater wasfilled with contaminated soil, it became necessary to move the crater lip material. A set of samples was taken in May 1979 by ERSP personnel, to characterize this material. The sampling and results are described in Tech Note 15.0. A final set of subsurface samples was taken in August 1979 in the area southeast of Fig-Quinee. The soil from this area was later used as fill to reduce the surface TRU activity after the Fig-Quince area cleanup was terminated (see Section 6.10). These samples were also used to estimate the final TRU to 24lAm ratio for northern Yvonne. Most of the cleanup effort on Yvonne was concentrated on the Fig-Quince GZ area. The FRST made periodic efforts throughout the cleanup project to pick up the milligram-size and larger pieces of plutonium from the Quince event. The usual method involved using handheld instruments to narrowly define the location of a particle, then removing small amounts of soil until the remaining activity dropped abruptly. In some cases, the actual particle could be isolated and removed. All the soil that was picked up in these efforts was bagged and later placed in the Cactus dome, as reported in Tech ote 14. 340