32 BULLETIN 181, U. S. DEPARTMENT OF AGEIGULTURE. 
drainage work is carried out or not. As these sedimentation areas 
will in most cases be outside the district boundaries, no estimates of 
cost have been made for them. 
The sediment carried by these tributaries originates for the most 
part in the erosion of the surrounding hills. Too much stress can not 
be laid on the importance of controlling this action by proper terracing 
of slopes. It should be realized that it is the most fertile particles of 
soil that are thus carried away, not only to the detriment of the land, 
but to the great damage of the drainage channels in which the sedi- 
ment is deposited. 
COST OF IMPROVEMENTS. 
In the estimates for the construction of ditches and levees the cost 
of clearing right of way is provided for in the price per cubic yard for 
excavation. 
It is believed that the ditches can be excavated at an average cost 
of 9 cents per cubic yard. Levees with berms of from 10 to 15 feet 
are estimated at 13 cents per cubic yard, and those with berms of 50 
feet at 18 cents per cubic yard; in both cases the earth is assumed to 
be measured in excavation. The increased unit cost of the levee 
work over that for the ditches is due to the greater cost of depositing 
aU of the earth on one side of the ditch or borrow pit, and to the cost 
of leveling and smoothing the bank. Where a 50-foot berm is specified 
a longer boom will be required than is necessary on the remainder 
of the work. This requirement, together with the greater distance 
which the earth must be moved, increases the fuel consumption as 
weU as the time of construction. 
In estimating the cost of floodgates, rough designs are made for 
three gates with capacities of 175, 525, and 1,400 second-feet, respec- 
tively, and the cost of each was determined on the basis of 1 per cent 
reinforced concrete construction, costing $25 per cubic yard in place. 
The cost of all other gates were estimated by determining their re- 
quired capacities, and interpolating between the three computed costs. 
The cost of right of way for levees and ditches was estimated at $10 
per acre, no allowance being made for right of way for ditches which 
follow the present channels. The expense of clearing all brush, logs, 
and stumps from present channels was estimated at $750 per mile. 
It is not expected that it will be necessary for the organization to 
purchase the land to be cleared for the river floodway. Therefore 
this item is not included in the estimate. The cost of clearing the 
floodway is estimated at $20 per acre, with an additional $1 per acre 
for incidental expenses. The timber cut should remain the property 
of the landowner. 
An addition of 10 per cent on the estimated cost of the improve- 
ments is made to cover legal, engineering, and other incidental 
expenses. A detailed estimate of cost is given in the table on page 33. 
