32 BULLETIN 181_, U. S. DEPARTMENT OF AGKICULTTJEE. 



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 le vehng 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 

 well 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 S25 per cubic yard in place. 

 The cost of all other gates were estimated by determinmg 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 bemg 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 remam 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. 



