TAK ATOLL Runit (Yvonne) Cleanup and Crater Containment CAP CONSTRUCTION :1"°=50 m SQUARE=1/16 Ha N 26 The dome cap was designed to protect the mound of contaminated material from natural erosion by wind and water. The POD design prescribed a nonload-bearing surface of 18 inches of concrete with the same strength characteristics as the keywall. Reinforcement was not prescribed because the concrete was to be produced using salt water, which accelerates corrosion of ferrous reinforcing materials. The final design of the cap sections was left to the USAE.In keeping with good engineering practices, it was decided that each cap section should be as close to square as possible to minimize shrinkage cracking. The USAE decided to place approximately 20-by-20-foot sections in the first ring, and continue with that size until the shape of the domedictated a reduction in size to keep the square shape ofthe individual sections. Each cap section was keyed to adjacent sections using forming techniques. The POD design required »le\ 100 expansion joint material only where the first ring joined the keywall (Figure 8-43). The rings were designated bytheletters ‘‘A”’ through “‘K,”’ beginning at the keywall and extending up to the top of the dome. The first sections of the ‘“‘A’’ ring were placed in May 1979, before the Donut Hole was filled and before final soil-cement operations were completed (Figure 8-44). The initial 20-by-20-foot forms were fabricated on site by the USAE using heavy lumber. The forms were positioned by survey and anchored with pins driven into the soil-cement surface. Full forms were used on alternating cap sections. Intermediate sections required an end form only. The formswere18 inches deep and contained a 4-by-4-inch tapered key (constructed using two 2-by-4-inch pieces of lumber) located from 7 to ll inches from the bottom of the side form (Figure 8-45). ET. Asthe capping operation progressed, the use of 18-inch steel forms was recommended. These were purchased by Field Command and used through the remainder of the project. The key on the steel forms was approximately the samesize as on the wooden forms, but was centered on the bottom third of the form. End forms of heavy lumberstill were used in conjunction with the steel forms. Once the forms wereinstalled, the area within the form was broughtto grade. The surface was then raked smooth and covered with polyethylene sheets to prevent absorption of water from the concrete. The forms were then lubricated to preclude their sticking to the concrete. Concrete wasplaced directly from the transit-mix trucks (Figure 8-46). For rings ‘“‘A”’ through “‘E,”’ the transit-mix truck was held in place using the winch cable from a dozer. This was necessary because of therelatively steep slope of the lower dome and the deteriorating braking systems on the trucks. Spreading and consolidation of the concrete was accomplished