EXCAVATING MACHINERY USED IN LAND DRAINAGE. 9 



$8,000 was shipped about 400 miles and hauled by wagon 18 miles. 

 The dismantling cost about $490; the freight charges were about 

 $700; hauling, $360; and rebuilding about $670. These costs are 

 fairly representative for this size of machine. 



METHOD OF OPERATING. 



With a floating dredge the construction should, where practicable, 

 begin at the upper end of the ditch and proceed downstream. Some- 

 times it is not feasible to transport the machinery and material to 

 the upper end of the ditch and the dredge must then work upstream. 

 This is undesirable, unless the fall be slight, since in working upstream 

 dams must be built behind the boat to maintain the necessary water 

 level. In working downstream the ditch remains full and the dredge, 

 floating high, can dig a much narrower bottom than if working 

 upstream in shallow water. Moreover, when floating low, the 

 dipper may not properly clear the spoil bank. Again, in working 

 downstream, any material dropping from the dipper into the ditch 

 will be taken out in the next shovelful; whereas if working upstream 

 any material dropped or any silt washed behind the dredge is left to 

 settle in the bottom of the ditch. If work is begun on the natural 

 ground surface a pit must be dug to launch the boat; or if in a stream, 

 it may be necessary to build a temporary dam in the channel to 

 raise the water high enough to float the boat. The depth of water 

 required varies from 2 feet upward depending on the size of machine. 



The floating dipper dredge moves itself ahead by means of the 

 dipper. The spuds are first loosened from their bearings and the 

 dipper is run ahead of the machine and rested on the natural ground 

 surface in front of the ditch. The spuds are then raised and the 

 engines operating the backing drum are started; the dredge, being 

 free, is thus pulled ahead. The spuds are then lowered and excava- 

 tion continued. 



In timbered country the right of way must be cleared. In many 

 cases the timber cut will supply sufficient fuel for the dredge. It is 

 poor policy to fall the trees and leave them on the ground to be 

 removed by the dredge. The stumps should always be shattered 

 with dynamite, as the strain on the machinery is thus rendered much 

 less and the life of the dredge increased. 



An engineer, a craneman, a fireman, and a deckhand are required 

 to operate a dipper dredge. The output, loss of time due to break- 

 downs, and the cost of repairs, depend almost wholly upon their 

 skill and efficiency. The engineer should be an all-around mechanic 

 as well as experienced in dredging. 



The amount of fuel consumed depends upon the size and type of 

 boiler used, and upon the burning and heating qualities of the fuel. 

 4908°— Bull. 300—15 2 



