The position must be such that there will be zero grade or better 

 for short runs, with proportionately higher grades for long runs. At 

 this project, with a slope of 4 feet in 3,000 feet (1 on 750), the con- 

 tractor has been able to deliver a satisfactory amount of material to the 

 surge pit. Any further increase in slope causes difficulty in delivery 

 of material, as the lines sand up, causing breakdowns in the system. 

 Where the depositing area is higher than the area from which the sand is 

 to be removed, the sand eductor system is not satisfactory as the effi- 

 ciency of an eductor is poor. Also, in locations with deposits of clay, 

 shale, or other solid materials which remain consolidated underwater, a 

 jet would not be suitable for this type of operation. 



To maintain efficient operation in the pumping system, the center 

 line of primary water and sand pumps must be located so there is a 

 minimum amount of suction lift. Also, the location must be such that the 

 discharge from the surge pit is slightly above the pump centerline to 

 provide a velocity that will keep the sluice material in suspension. 

 This limits the advisability of the use of the system in many locations. 

 At the El Segundo plant, it was necessary to locate pumps No. 1 and 3 

 below grade line, to reduce the suction lift from the ocean and to obtain 

 the necessary drop from the surge pit, to improve total plant efficiency. 

 If this had not been done, the delivery rate of pump No. 1 would have been 

 lowered, and the amount of material in suspension received by pump No. 3 

 would also have been lowered, thus reducing the total plant efficiency. 



A system designed for utilizing the sand eductor as a prime mover for 

 transferring sand or soil from point to point would have extreme applica- 

 tion limitations, for the following reasons: 



1. The eductor has no mechanical means of agitation for mixing the 

 sand with water; therefore, the material must be delivered -to the eductor 

 with the sand or soil suspended in the water at a correct mixture to be 

 siphoned in by the eductor and forced through the discharge line economi- 

 cally. If the mixture is too heaAO^, settlement and clogging of the 

 discharge lines will occur; if the mixture is too light, too much energy 

 is dissipated in pumping water. 



2. The maximum length of discharge line through which material was 

 forced by an eductor satisfactorily on the Hyperion project was 3,000 feet 

 and this was with, a 4-foot drop in elevation and with a mximum pressure 



of 90 pounds per square inch, which was the pressure available for use 

 with the equipment on hand. This limits the installation to locations 

 where a drop of 1.33 feet or more per 1,000 feet could be obtained in the 

 discharge lines, and the deposit area must be located within a 3,000-foot 

 radius from the borrow pit. If the length of discharge line is greater 

 than stated above, the material in suspension will settle to the bottom 

 of the line, thus sanding up the line and stopping the flow of water, 

 unless a system with higher water pressures with resultant greater nozzle 

 velocities is used. To force the suspended material a greater distance, 

 the pressure of water delivered by the pump to the eductor nozzle must be 

 increased to obtain hijgher velocity and prevent settling of the material 



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