CHAPTER XXVI 



DREDGING FOR INDUSTRIAL PURPOSES SAND DREDGING 

 DREDGING FOR FILLING UP LOW LAND 



Sand Dredging for Commercial Purposes. Another industry 

 based exclusively upon the work of dredges is the excavation of 

 sand and gravel from the great rivers for commercial purposes. 

 This industry was described by Mr. Richard G. Donovan in an 

 interesting article contributed to the Engineering Record, Jan. 5, 

 1906, which is slightly condensed here. 



One of the important industries on the Mississippi River and 

 its tributaries is dredging sand and gravel for commercial purposes. 

 These rivers carry an immense volume of sand, gravel and other 

 matter which form large bars at locations where the current is 

 checked. The annual floods also play an important part in the 

 formation of these bars, for the high velocity of the river during 

 these periods tends to erode the bed and side banks; when the 

 floods decline the load is too heavy for the decreasing velocity, 

 and the gravel and sand are rapidly deposited. 



In the Ohio River at some localities gravel is found in large 

 quantities with but a small percentage of sand, while in other 

 places the bars may be entirely of sand. In the Pittsburg district 

 the Allegheny River is noted for its fine clean sand, and most of 

 the sand used in the district comes from this river. The sand from 

 the Monongahela River, on the other hand, is dirty and contains 

 injurious deposits from the numerous manufacturing plants along 

 its banks. In the Mississippi River, as a rule, the bars contain 

 fine, fairly clean sand of quite recent deposits. An immense amount 

 of sand and gravel is taken from the rivers annually and the develop- 

 ment of this business has resulted in the adoption of certain types 

 of dredges to meet the peculiar conditions existing in the various 

 localities. Those more commonly employed are the hydraulic, 

 the ladder and the grab-bucket dredges. 



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