FINAL CONSTRUCTION 



In April 19^9, a contract was awarded for sealing an additional 880 

 feet of the middle jetty and 1,000 feet of the north jetty (see fig. 2). 

 Specifications were prepared on the basis of what was learned and proved 

 during the experimental construction. Procedures on the final construction 

 differed little from those on the experimental construction, although the 

 equipment used was superior. 



A batching and mixing plant especially for the job was built By the 

 contractor. The mixer consisted of twin l/2-yard plaster mixers discharg- 

 ing into a shallow hopper, mounted directly underneath, which funneled the 

 grout into a valveless rotor-stator positive action pump. The assembly 

 was mounted on a car which ran on a railway constructed on the jetty top. 

 Likewise, an endless belt elevator mounted on railway trucks, elevated the 

 dry ingredients of the grout into the mixer as they were placed at the 

 lower end of the belt by hand. A sand hopper, also mounted on a car, ran 

 back and forth from the beach to the elevator. Rotary gates released 

 sand into a measuring vessel, swung on trunions, which fed the sand onto 

 the belt directly from the bags. The discharge end of the elevator could 

 be continuously charged and discharged. 



A mine air hoist was rigged at the land end of the rails and, with 

 a closed loop rove through a snatch block placed at the sea end of the 

 rails, moved the mixer and wagon drill as needed, and also shuttled the 

 sand hopper from the stockpile to the mixer. 



The wagon drill was mounted on a car which ran on the rails, and 

 2-1/2-inch detachable silicon carbide bits were used. Spalls and loose 

 rock, encountered in the drilling, sometimes hampered the work and some 

 holes had to be abandoned and relocated. 



Materials . - Materials used in the final construction were the same 

 as in the experimental construction. The clay used was similar to the 

 P-95 rotary drilling clay used in the experimental construction. This 

 clay was mined at Muroc Dry Lake, California, ms was the Macco P-95. 



Mixing and placing . - The grout was mixed at the point of deposition 

 and was not pumped farther than 25 feet to the nozzle. This method allowed 

 the grout to be severely stiffened by reduction of water whenever large 

 openings to the outside of the jetty were encountered. The nozzle consisted 

 of 1-1/2-inch rigid pipe. The holes were drilled much truer on this job 

 than was done on the experimental work, so it was never necessary to use a 

 flexible nozzle. Batching measurements were made volume trically. Sand 

 was measured by a calibrated steel vessel under the hopper, and water by 

 a meter installed at the mixer. Cement and clay were delivered in sacks. 



