10 BULLETIN 300, U. S. DEPARTMENT OF AGRICULTURE. 
A very great saving can be effected by covering the boiler with an 
asbestos coat. Ordinarily, about 25 pounds of coal per horsepower- 
hour are consumed on dredges. The cost of repairs depends largely 
upon the operator; a careless operator will cause many unnecessary 
breakdowns. It is not only the high cost of repairs for machinery 
but also the time lost which aids in increasing the actual cost of the 
output. It is a well-established fact that it is not the initial cost of a 
dredge or of any machine, but the operating and overhead expenses, 
that reduce the profits. 
COST OF OPERATION. 
The cost of dredge work depends upon a number of factors. The 
locality of the work, the kind of soil, repairs, delays, labor, etc., 
greatly influence the actual cost of any work. If the water level can 
naturally be maintained within a foot or so of the surface of the 
ground, the cost of excavation can be reduced very low with this type 
of machine. The data given in the following pages were obtained 
from the actual cost records of the various projects. Unfortunately, 
the figures are not always strictly comparable, one project with 
another, owing to variations in the items of cost included. Unless 
otherwise stated, interest is taken at 6 per cent and depreciation at 
35 per cent per annum on the cost of the dredging outfit. Interest 
and depreciation are, however, charged only for the interval of time 
upon which the unit cost is based. This is not strictly correct, as a 
certain amount of time consumed in getting the machine on and off 
the work should be charged to each project. In most cases it was 
impossible to ascertain the time that should be charged to moving, 
building, etc., and therefore the item has been ignored in all cases, for 
the sake of uniformity. On some projects figures for operation over an 
extended period were not obtainable. In such cases the unit cost is 
based upon the daily cost of operation and the average amount of ditch 
dug' per day, no allowance being made for interest and depreciation. 
In the construction of a ditch in North Carolina a new IJ-yard 
dipper dredge was employed. This dredge had a 5 by 20 by 70 foot 
hull and was equipped with 8f by 10 inch double-cylinder hoisting 
engines; 7 by 7 inch double cylinder, reversible swinging engines; 
a 50-horsepower Scotch marine return-flue boiler; a 1^-yard dipper, 
31-foot dipper handle, and 45-foot boom. The spuds were converti- 
ble to bank or vertical and were operated by the hoisting engines. 
The cost of this dredge, erected, was $10,342.19. The dredge was 
operated continuously, each shift working 11 hours per day. The 
men were paid at the following rates per month: Superintendent in 
charge, $110; engineers, $100; cranemen, $60; firemen, $48; deck- 
hands, $36. The men furnished their own subsistence. The ditch 
