266 A TREATISE ON DREDGES AND DREDGINC 



cu.yds. for the two dredges. Any excess over this, a contractor 

 would apply to expenses of administration and to dividends. 



" The twelve months ending June 30, 1906, show a monthly aver- 

 age, for the two dredges, of 316,200 yds.; the last three months' 

 average is 458,319 yds.; in the last month, June, 1906, 535,692 yds, 

 were excavated. The work of June, 1906, is the largest month's 

 work which this plant has yet done. Under favorable conditions 

 as to kind of material and with little lost time due to repairs, etc., 

 it may perhaps be exceeded, but it is doubtful whether the plant 

 can permanently maintain so high an average." 



COST OF HYDRAULIC DREDGING, HARBOR OF WILMINGTON, CAL. 



In the harbor improvements at San Pedro and Wilmington, Cal. 

 a suction dredge built by the Ellicott Machine Co., of Baltimore, 

 Md., is employed. Prior to the acceptance of the same by the 

 United States, and during an efficiency test, 16,450 cu.yds. of material 

 were removed from the proposed harbor and deposited behind a 

 bulkhead. The total cost for labor employed, including superintend- 

 ence, and for the fuel, water and other supplies expended on account 

 of this work, was $1682.46, or at an average cost of 10.2 cents per 

 cu.yd. of material handled. The dredge was placed in commission 

 April 1, 1905, and between this date and June 30, 1905, it removed 

 227,464 cu.yds. of material, which consisted principally of sand 

 intermingled with shell, and a small percentage of clay, cobbles, 

 disintegrated sandstone and very compact and hard mud. During 

 the period mentioned the dredge was laid up 16 days, May 15 to 

 30, 1905, so that the actual working time was 2J months, the 

 average rate of dredging per month being thus 91,000 cu.yds. 



The following statement shows the cost of the dredging during 

 the period from April 1 to June 30, 1905: 



Routine office work, labor $673 . 33 



Care of plant and property, labor 180. 00 



Surveys, labor and supplies 155 . 63 



Towing and dispatch work, labor, fuel and supplies 316 . 00 



Alterations and repairs to dredging plant, labor, and 



material 2,432 . 52 



Operating dredge, including superintendence and labor 

 charges, fuel, fresh water, lubricants, and all other 



supplies 10,084 . 54 



Deterioration of plant and property, estimated 2,263.94 



$16,105.96 

 Cost per cubic yard, $0.0708. 



