EXCAVATING MACHINERY USED IN LAND DRAINAGE. 35 



top of the levee by small towers mounted on 14 by 40-foot barges. 

 A strip about 30 feet wide along the center of the site of the levee was 

 grubbed and ploughed. No muck ditch was prepared. The levee 

 was about 14 feet high with an 8-foot crown and 3 to 1 slopes on both 

 sides. The number of men usually employed was about 14, and the 

 fuel used was about 5 tons of good coal in each shift. Two 11-hour 

 shifts built 100 linear feet of completed levee, or 2,700 cubic yards. 

 A dredge of this type costs approximately $15,000, not including 

 the discharge pipe, the barges, and other necessary appurtenances 

 which will add about $5,000, making the total first cost about $20,000 

 for a plant to build levees by this method. 



With hydraulic-fill levees a wide foreshore can be left. There are 

 no borrow pits to aid in probable seepage and consequent failure of 

 the levee. Any side slope wanted for a levee can be built. There 

 is no shrinkage after the embankment is first completed, for the 

 material is thoroughly compacted. The fine material is deposited 

 in the base of the levee where it is most needed to prevent seepage. 

 By using the hydraulic-fill method, a levee can be built across an old 

 bayou or lagoon with as little trouble as on dry ground, which can 

 be done by few machines. Wet, soggy ground gives no trouble in 

 construction. Hydraulic-fill levees, being composed mostly of sand, 

 are proof against damage by burrowing animals. 



On the other hand, a 20-foot head with about 600 to 800 feet of 

 discharge pipe are the maximum conditions under which a plant de- 

 veloping only 200 horsepower can operate; greater heights and dis- 

 tances must be overcome by a corresponding increase of power 

 equipment. The dredge must always be in about 8 feet of water to 

 prevent air from being drawn into the suction pipe. It would hardly 

 pay to put such an outfit on a project of less than 250,000 cubic yards. 



It has been observed in hydraulic fills made with clay that the 

 tendency to settle is not so marked as when sand alone or sand 

 mixed with some silt is pumped. The tendency of the sand to settle 

 in the bottom of the discharge pipe permits the building of levees 

 having any slope between the natural slope assumed by moist sand 

 and that of a semifluid. By using the slope boards, however, a greater 

 range of side slopes can be had. 



MACHINES FOR CLEANING OLD DITCHES. 



A floating dredge as a rule is unsuited to cleaning old ditches unless 

 the amount of material to be excavated is large. It is also imprac- 

 ticable to dam up the channel on account of possible damages to the 

 landowners. Moreover, all bridges must be removed if a machine 

 of this kind is used. 



A type of the stationary scraper excavator which straddles the 

 ditch has been used quite successfully on the smaller ditches. On 



