—~ Runit (Yvonne) Cleanup and Crater Containment the design was selected to begin the keywall; i.e., a radius of approximat an arc v 185 feet from the center of the crater. Using the 185-foot radius, surveyed and staked out on the reef. The arc fell about 12 feet outsidet t crater lip. Excavation to place keywall forms began on the reef following week,’? and thefirst 10-foot section of keywall was placed t week of 6 November 1978.78 A field engineering decision was made | change the form length to 12 feet to accommodate use of standard s plywood. This resulted in fewer forms being required for the northern h (48 in lieu of 58) without detracting from the roundnessof the keywall.” Keywall construction was hampered by reef and tide conditio: Excavation and forming could be accomplished only during that half o day when the tide was out. The excavations were full of water even at |c tide, causing difficult and unpleasant working conditions and hamperi excavation (Figure 8-26). Tidal water in trenches also hampered ¢t proper placement of concrete (Figure 8-27). Dumping concreteinto t water-filled forms resulted in laitance in some sections, as was revealed subsequent core samples. 80 Concrete for the keywall was mixed using a type 16S concrete mixer ur tremie operations were completed. Thereafter, the batch plant, which v decontaminated on 27 February 1979, was used to produce clean concre which was then transported to the keywail construction site by transit-n trucks. ‘. ~ Cr, Ns e 3 . —_ FIGURE 8-26. BUILDING THE KEYWALL.