DIPPER DREDGES 159 



by passing boats or scows is certainly greater than in dredges com- 

 pelled to work in narrow spaces and under crowded conditions. 

 The five dredges employed in the section of the Chicago Drainage 

 Canal, mentioned above, while in the best week's work their output 

 was almost equal to one bucket per minute, yet in the average their 

 efficiency was of one bucket every two minutes, owing to the fact that 

 they were too crowded and consequently often they interfered with 

 one another, and they were served by scows and tugboats. When 

 the dredging work is depending upon other operations it would be 

 impossible to expect the greatest efficiency from the dredge. Thus 

 while the dredge "Alpha," on the Raritan River, could remove shale 

 rock and gravel at the rate of one bucket per minute, yet when the 

 rock was so hard that it was necessary to recourse to blasting, the 

 same dredge on the same locality worked at the rate of one bucket 

 every nine minutes. 



The dipper dredge of small capacity is handled by a crew of 

 6 men, while this number increases with the capacity of the machine, 

 and a dredge of 8 cu.yds. is served by 16 men. The daily running 

 expenses of working the machine are wages, coal, water and oil 

 and waste. Dividing by the number of cu.yds. dredged the 

 cost per one cu.yd. is given. Other costs to be considered are the 

 interest of the capital invested, the wear and tear, and sinking fund, 

 but these will be discussed in a special chapter. These are so impor- 

 tant that while in the Massena Canal a dredge worked at the average 

 cost of 4 cents per cu.yd. for labor and coal, the cost for interest and 

 depreciation was 7 cents per cu.yd., thus making a total cost of 11 

 cents per cu.yd. The other items were almost double the cost of 

 labor and coal. 



The dipper dredge is the typical American dredge, and has 

 rendered magnificent services on the Great Lakes. But even to-day, 

 notwithstanding there are so many powerful dredges at our disposal, 

 the old-time dipper dredge of small capacity can be still considered 

 without a rival on small contracts for the improvement of narrow 

 rivers and in digging canals for draining purposes when the debris 

 is deposited on both sides to form the levee. The dipper dredges of 

 small capacity are handled by a few men, are not easily broken, 

 and the repairs are almost insignificant, while in dredges of larger 

 capacity the expenses are heavy when the machine is compelled 

 to lay idle for repairs. Mr. Robinson says that a wooden dredge 

 ten years old, costing say $30,000, will excavate 1500 to 2000 cu.yds. 



