TABLE 7-6. VOLUME AND TRU ACTIVITY OF SOIL EXCISED DURING THE RADIOLOGICAL CLEANUP OF ENEWETAK ATOLL Soil Volume Island (Cubic Meters) Sally 8,100 Irene 3,775 Aomon Crypt Janet Pearl Yvonne Totals 7.5.1 TRU Activity (Curies) 1.3 Total Area with Soil Excision Area (ha) % of Island 1.8 4.5 0.6 3.3 7,475 0.9 0.2 40,525 11,415 8,210 2.6 1.7 7.2 15.5 9.7 5.0 79,500 14.7 32.8 1.0 1.0 13.1 44,1 13.5 Irene Background Island Irene (Marshallese: Boken), the northernmost island in the Atoll, is moderately to heavily vegetated. It is now about 18 hectares (ha) in area, but was somewhat larger, perhaps 20 ha, prior to nuclear testing activities. The change in area is the result of the Seminole event, which left a water-filled crater about 150 m in diameter in the west-central coastline of Irene. A sandspit extends outward from the main island along the southern edge of the crater, curling to the northwest and stretching several hundred meters west of the main island. The spit, formed from a combination of nuclear event throwout, a small remnant of island Helen (Marshallese: Bokaidrik) and wave-deposited sand, tends to change shape with every major storm. The only constant sections are a small vegetated area near the main body of the island and another small vegetated area about 200 m west of the mainisland. The latter area is all that remains of Helen, so the sandspit is known as the "Helen spit." Figures 7-49 and 7-50 are maps of Irene and the Helen spit, respectively. The only event ground zero (GZ) on Irene was Seminole; the GZ itself was just east of the center of the crater left by that event. However, the Mike and Koa events which vaporized the nearby islands of Flora and Gene (see Section 7.5 for more details) also extensively affected Irene. Other events on barges in the Mike crater also affected Irene, eventually destroying most of Helen and forming the Helen.spit from what remained. As a result of the 24 events which affected Irene and Helen, they ranked fourth and fifth in the Atoll in total H + 1 hour exposure rate with 6,184 R/h and 2,277 R/h, respectively. Among the effects of the events on and near Irene are direct blast effects, at least one impact erater from flying debris, and repeated wave inundation. Both the shape and physical characteristics of Irene were altered by these processes. Many test structures were built on Irene, with substantial soil rearrangement in the process, leading to numerous areas of suspected buried contamination. For example, in order to provide line-of-sight from Ivy Station 200 in northeastern Irene to the Mike crater, contaminated throwout from the Seminole crater was bulldozed aside. Similar actions may have taken place during construction of a line-of-sight pipeline to the Koa GZ, and there may have been deliberate burials of contaminated soil and debris. The areas suspected of containing subsurface contamination are shown in Figure 7-49. A great deal of debris, scrap metal, and old scientific stations remained scattered all over the island after testing ceased. Much of this debris was contaminated, and it was difficult to distinguish between contaminated and uncontaminated material because of Irene's high background activity. Some of the debris was subsurface; for example, at least one station was constructed below~grade and never removed, and many buried cables and pipes were left. cables were found during the cleanup, still in place. 261 A number of the