with a range from 0.20 to 0.48 percent. The concrete mix used five sacks 

 of cement per cubic yard, and 3-inch maximum size of aggregate. Calcium 

 lignin sulphonate water-reducing additive was used at the contractor's 

 option. A dual drum paving mixer operated on a bulkhead ramp adjacent to 

 the casting pit so that its bucket could discharge directly into the 

 tetrapod forms . 



The forms were of two-piece steel construction: the bottom section 

 formed the bottom half of the three lower legs, and the top section formed 

 the top half of the lower legs and the upstanding leg. End gates for the 

 bottom legs were hinged to the top section. The contractor used 36 bottom 

 sections and 12 top sections, which allowed pouring 12 tetrapods per day. 

 The top forms were stripped after 20 hours, and the tetrapods removed from 

 the bottom forms after 3 days. For this first lift, a special compression 

 sling developed by the contractor gripped the tetrapod by pressing a bearing 

 plate against the flat end of each bottom leg, thus allowing the tetrapod 

 to be handled while the concrete was still green without damage or over- 

 stressing. A large crawler crane lifted the tetrapods from the casting pit 

 and placed them in an adjacent storage yard for the 28-day curing period. 



The first material for the island was placed in February 1957, after 

 several months of quarry development and the construction of temporary 

 facilities. Most of the marine work was done on a two-shift, 6-day work 

 week since marine equipment charges represented a sizable proportion of 

 the contractor's costs. The general procedure was to build the exterior 

 rings of each lift out of Class G and F material, then place the armor 

 rock and the core material. Class G, F, and core materials below eleva- 

 tion -15 feet were placed by bulldozing the material over the sides of 

 carefully located barges. Except for the top lifts of tetrapods and armor 

 rock, which were placed by a crawler crane from the island, all armor 

 materials were placed by barge-mounted cranes. 



The contractor placed wood-pile dolphins on the north and east sides 

 of the island work area, and used targets strung between the dolphins to 

 provide position lines for placing materials below water. The island 

 first broke water in October 1957. The seaward face was constructed first, 

 to elevation +17 feet, to provide some protection from the approaching 

 winter weather. Before complete closure of the island above water, suffi- 

 cient core material was placed on the south side to allow the barge-mounted 

 crawler crane to be unloaded. This was accomplished by beaching the barge 

 against the core and walking the crane off on a temporary ramp of core 

 fill. The final closure of the north face was made in January 1958. 



Core fill for the island was a medium to fine sand obtained from the 

 cliff behind Punta Gorda about 1,320 yards from the island site. It was 

 first hauled by truck to the contractor's loading-out pier, then by barge 

 to the island site. It was not surprising that the contractor elected not 

 to dredge the core fill, since the final design required a relatively small 

 amount of sand for an economical dredging operation. The lift-type con- 

 struction required core sand to be placed on an intermittent schedule, and 

 the open sea is an insecure place to operate a dredge even on larger projects. 



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