438 RADIOLOGICAL CLEANUP OF ENEWETAK ATOLL Following an inspection by helicopter, it was discovered that inward distortion of the circle existed, not apparent from the ground. It also wag discovered that extending the keywall circle throughout the remaining are would run it directly into the high banks of ejecta on theisland side. The CJTG directed that 31 recently placed keywall sections be removed anq replaced with properly aligned sections.85 The banks had been a concern because it was believed that they contained high levels of subsurface soil contamination. After the misaligned keywall sections were removed, the CJTG directed that the banks be bulldozed, the soil be placed in the soil-cement mix in the crater, and the keywall correctly aligned. It was then in the crater, and the keywal} correctly aligned. It was then discovered that the banks contained a large quantity of contaminated debris, but that the soil contamination was less than 40 pCi/g.86 Subsequent helicopter surveys revealed that some of the replacement sections were Slightly out of line. This had no effect on the function or durability of the keywall but detracted from the aesthetic appearanceof the dome. As a result, 24 more sections were removed and replaced.87.88,89 Misalignment of these sections was caused by the incorrect use of a template to turn the angles between sections. This problem was solved by using survey proceduresto establish the proper location of each section. A total of $5 misaligned keywall sections were removed and used as armor stone in constructing the mole. The completed keywal! contained 99 sections, 95 of which were [2 feet long; three, 10 feet long; and one, 9.4 feet long. The circumference was 1,179.4 feet, and the nominal! diameter was 377 feet.9° An estimated 528 cubic yards of concrete were used in the keywall construction. SOIL-CEMENT OPERATIONS Once the crater wasfilled to 3 feet above the reef, the tremie barge was stabilized in the tremie, the crane was removed, and the remaining contaminated materials were stabilized and contained using a soil-cement process. Thereafter, contaminated soil was delivered to the containment site by truck and dumpedon the already processed material. A grader was used to spread the soil in approximately 6-inch layers (Figure 8-29). Bags of cement werethen placed in a pattern designed to provide two bags per cubic yard and cut open (Figure 8-30). The dry cement was mixed dry with the soil by a disc harrow towed by a dozer (Figure 8-31). Water then was distributed over the dry mixture (Figure 8-32). A vibratory rollercompactor was used next to compact the soil-cement mixture (Figure 833). Tests were made with a cone penetrometer to insure that the design strength of 300 psi was achieved.