48 BULLETIN 71, U. S. DEPARTMENT OF AGRICULTURE. 



material to flow into the canal. The surface is raised between 1 and 2 feet 

 for a distance of 100 or 200 feet back from the canal banks by the deposit 

 made by the hydraulic dredge. The cost of cutting the canals by this method 

 is not as great as with the other type of dredge and the results are much more 

 satisfactory. It is expected that in the future this type of dredge will be used 

 almost exclusively where the ground is free from trees and stumps. 



Ditches. 



The spacing of the ditches on this tract is 165 feet. With the canals at 

 one-half the usual distance, and with a deep, porous muck soil, this spacing 

 should give a sufficient amount of drainage for a number of years until the 

 soil becomes more impervious, due to the decay of the vegetation it contains. 

 Owing to the soft nature of the soil in this district a long time would have 

 been required for it to become solid enough to use the ordinary type of apron 

 traction ditcher. A capstan ditcher, or ditching plow, was therefore used to cut the 

 ditches. The plow was pulled with cables running between two adjacent collecting 

 canals. In each of the canals an engine with winding drum was mounted on a 

 barge. After cutting a ditch the barges were floated along the canals to the 

 location of the next one. In some of the softer portions this plow was found 

 to be too heavy and plowed too deeply, so a lighter structure of wood was sub- 

 stituted which cut a very satisfactory surface ditch. This tract is free from 

 logs and stumps, thus allowing the use of such machinery. When the surface 

 has become fairly solid, due to the drainage afforded by these superficial ditches, 

 the larger and heavier ditching plow can be used, and all of these ditches will 

 be put down to a depth of 3 feet. By this method of ditching the time con- 

 sumed in placing the tract under complete drainage will be considerably 

 lessened, for a wait of several months would have been necessary before a 

 traction ditcher could have been used. 



Pumping Plant. 



In location this plant is rather far to one corner of the tract, but due to the 

 large size of the main reservoir canal no great loss of head should result in 

 the canals when the pumps are in operation. The greatest distance that the 

 water will travel in the canals to reach the pump is about 3 miles. The pumps 

 discharge into the navigation canal that surrounds the district and connects 

 with the bays and bayous to the rear. 



The machinery consists of one 36-inch and one 24-inch cast-iron centrifugal 

 pump direct connected to slide-valve engines. The boilers are of the return- 

 tube type and oil is used as fuel. The discharge and intake pipes on both 

 pumps are enlarged to save the usual loss of velocity head. The two units are 

 mounted on separate concrete foundations, supported on piling, the foundation 

 forming part of the dam across the outfall canal. The greater part of the dam 

 is of mud held in place by the rows of sheet piling that form the cofferdam. 

 This saves considerable expense for concrete and still insures a water-tight 

 dam. It is planned to use the small unit in times of ordinary rainfall and to 

 use both when necessary. The combined capacity of the pumps when operating 

 at full load will be about 1.1 inches in depth in 24 hours. On account of the 

 high tide to be expected in this vicinity, the pumps are capable of working 

 against a 10-foot head. The capacity will of course be greatly reduced at this 

 head. 



The building over this machinery is of fireproof construction, being a frame- 

 work of structural steel covered with heavy corrugated galvanized iron. 



