METHODS AND COSTS OF RIVER DREDGING 209 



excavating 2,671,750 cu.yds., scow measurement, giving a daily 

 rate of 21,200 cu.yds. During the month of September, 1903, the 

 dredge excavated 757,100 in 25 days or 552 hours, making an average 

 rate of 1646 cu.yds. per hour, or 30,280 cu.yds. per day. During 

 the season of 1904 in 92 days the "Tarte" dredged 1,123,125 cu.yds. 

 at a total cost of $79,302.02, or 7.06 cts. per cu.yd. In 1905, 1,984,- 

 510 cu.yds. were moved, costing $117,668.03, or 5.92 cts. per cu.yd. 

 This work was done in 160 days. For the season of 1906, in 105 

 working days 1,358,560 cu.yds. were excavated, costing $86,533.82 

 or 6.36 cts. per cu.yd. 



Tte "J.- Israel Tarte" is 160 ft. in length, 42 ft. beam, with a 

 draft of 6 ft. (see Fig. 34). The suction frame is 80 ft. long, giving 

 a possible working depth of 45 ft. The discharge pipe is 36 in. in 

 diameter. The four boilers are of the marine type, carrying 160 

 Ibs. pressure. The rotary cutter is 9 ft. long and 9 ft. 6 in. in diameter. 

 There are four steel blades at the apex and 8 at the throat (see Fig. 

 27). The blades are designed so that the clay does not clog up the 

 throat. The cutter is operated by a pair of double tandem engines 

 of 300 H.P. (see Fig. 26). 



Near the close of the season of 1903 one of the boilers on this 

 dredge exploded, killing two men and injuring the dredge. It 

 took four months to make the repairs. Four new boilers were 

 placed in her. These, with a new system of steam piping, erecting 

 the smokestacks and work on her cabin cost $27,644.11. At the 

 end of 1905 a general overhauling was given the machinery and 

 boilers. Thus the dredge, as it now stands, cost for hull, machinery, 

 5-ft. pipe line, as altered and improved, about $400,000. The annual 

 repairs have varied from $8000 to 20,000, or a little more than 

 5 per cent of the cost of the machine. 



The annual repairs to one of the ladder or elevating dredges 

 used on the St. Lawrence, with its necessary outfit, averages about 

 $10,000. It cost about $40,000 per year to operate such a dredge, 

 and about twice that amount to operate a hydraulic dredge such 

 as the "Tarte." It is estimated that the entire dredging plant 

 used on the St. Lawrence River cost about $2,000,000. This is exclu- 

 sive of a well-equipped shop maintained by the Canadian Govern- 

 ment at Sorel for building and repairing dredges, tugs, scows and 

 other things needed both on the St. Lawrence and for other dredg- 

 ing work. 



In 1906 a hydraulic hopper dredge was purchased and put to 



