EXCAVATING MACHINERY USED IN LAND DRAINAGE. 9 
DETERMINATION AND ANALYSIS OF COST DATA. 
Cost data, if they are to have permanent value and be indepen- 
dent of fluctuating wages and prices, must be expressed in absolute 
terms, such as labor hours, fuel consumption per unit of output, 
average output per unit of time, etc. Moreover, the cost of operation 
alone does not give the cost of any project. The cost of securing 
the contract, assembling the machinery to do the work, together with 
the many items associated with assembly, must also be included, as 
well as repairs, depreciation, and interest. and the contractor’s 
profit. 
In estimating the unit cost of a project the cost. of installing and 
operating the machine or machines to be used, together with interest 
charges, depreciation, and lost time, is computed and the amount 
divided by the engineer’s estimate of yardage. The output will not 
be the same on all jobs; for this reason experience with different 
soils and conditions is valuable in estimating work. A record of 
quantities under different conditions is of greater value than a record 
of costs alone. 
Let it be assumed that a floating dipper dredge is to be used on a 
project. The weight of the machinery and the number of cars 
required for shipping must be known. The same information must be 
had with respect to the material for the hull. With these data the 
freight charges can be determined. The number of men and the time 
required to dismantle the dredge, the number of wagonloads, the 
length of haul to the siding, the condition of the roads, and the time 
required for hauling must be determined, together with data on 
hauling the equipment from the railroad to the project and the num- 
ber of men and the time required to assemble the dredge. These 
are all items which must be known and used in determining the cost 
of placing this machine on the job ready to work. In addition, the 
cost of dismantling and of building cabin boats, coal barges, and 
launches must be considered. 
In determining the cost of operation, the number of men required, 
the average output per shift, the fuel consumption per shift or unit 
of output, and the transportation of fuel and supplies to the ma- 
chine are items which must be considered. The time lost in moving 
due to weather conditions should also be taken into consideration. In 
the Northern States frost in the ground delays the work from three 
to four months each year. Likewise the cost of repairs, depreciation, 
interest, insurance on the dredge, and workmen’s liability insurance 
must be taken into account. The same cost items must be reckoned 
for any type of excavator. 
