384 



KEPORT OF OFFICE OF EXPERIMENT STATIONS. 



TRACTION DREDGE. 



Where the ground is firm enough for a man to walk, a more satisfac- 

 tory way is to use a traction dredge with a swinging boom and a clam- 

 shell bucket (fig. 6). In this case the machinerj^ is mounted on a 

 platform that moves on rollers or is self-propelling on a temporary 

 track. It digs in front and backs away from the work (fig. 6). With 

 a machine of this kind very large embankments may be built, leaving 

 a wide berm and a shallow pit. Traction dredges of this type with a 

 boom 100 feet long and carrying a 25-yard bucket, are successfully 

 used for levee building along the Mississippi River. Where there are 

 no stumps or logs an embankment can be built with any type of dredge 

 as above stated, at a cost ranging from 3^ to 6 cents per cubic 3'ard. 

 Although this method of constructing embankments is very cheap it 

 is only practicable where there is a large quantity of material to be 

 handled, as it is very expensive installing a dredge suitable to do the 



-□ — D — a — u id'" 'lift la- — m — m — a — □ — (3- 



FiG. G.— Typo of traction dredge suitable for building dikes. 



work. This is one great reason why cooperation is necessary to suc- 

 cessfully reclaim the greater part of the salt marsh under consideration. 

 In building levees with a dredge the different layers of material are 

 more thoroughly mixed than when put up with hand labor and make 

 a much more compact and impervious embankment. 



ELEVATOR AND SUCTION DREDGES. 



Elevator and suction dredges discharge so much water with the 

 material they excavate that they are not well adapted to building 

 levees. They have, however, been used quite successfully in some 

 places by building parallel walls of turf and sod to hold the material 

 until the water drains out. The great difficulty in building a levee 

 with a dredge is to get one with a boom or carrier long enough to place 

 the material in the embankment without digging a deep pit too near 



