A radiological survey of Enewetak was conducted from 1972 to 1973. In 1977, the United States military began decontamination of Enewetak and other islands. During the three-year, US$100 million cleanup process, the military mixed more than of contaminated soil and debris from the islands with Portland cement and buried it in an atomic blast crater on the northern end of the atoll's Runit Island. The material was placed in the deep, wide crater created by the May 5, 1958, "Cactus" nuclear weapons test. A dome composed of 358 concrete panels, each thick, was constructed over the material. The final cost of the cleanup project was US$239 million. The United States government declared the southern and western islands in the atoll safe for habitation in 1980, and residents of Enewetak returned that same year. The military members who participated in that cleanup mission are suffering from many health issues, but the U.S. Government is refusing to provide health coverage.