

METHODS AND COSTS OF RIVER DREDGING 205 



for a distance of 108 miles, from Montreal to Cap a la Roche, a 

 depth of 27J ft. at low water had been obtained, while for the other 

 52 miles the river had been dredged to the same depth at half tide. 

 Prior to 1888, namely from 1851-1888, 19,865,693 cu.yds. of material 

 were dredged at a cost for labor and supplies of 17.1 cents., while 

 the charge for plant, shops, repairs, surveys and other general 

 expenses was 2.7 cents, making a total of 19.8 cts. The work from 

 the start has been done with dredges and machines owned by the 

 channel authorities and with day-labor forces. 



For the period from 1889 to 1899 there was excavated 3,558,733 

 cu.yds., in widening and cleaning up the 27}-ft. channel, at a cost 

 of 23.3 cts. for labor and supplies, to which must be added 14 cts. 

 for plant, shops, repairs, surveys and other charges, making a total 

 cost per cu.yd. of 37.3 cts. 



Since 1899 work has been done on a new project, namely, a 

 30-ft. channel, from Montreal to the Traverse, the distance to be 

 actually dredged being about 70 miles. Up to March 31, 1908, 

 about 58J miles were finished, leaving at that time 11J miles to 

 be dredged. The minimum width of this channel is 400 ft. in the 

 straight portions, and from 500 to 750 ft. on the curves or turns. 

 The entire channel has been widened, with the exception of a stretch 

 in Lake St. Peter. Of a total of 68,500,000 cu.yds. of excavation 

 to be made to complete this project 55,517,055 cu.yds. had been 

 dredged up to March 31, 1908. The detail cost of this work will 

 be given. 



The materials excavated vary exceedingly. In Lake St. Peter 

 soft blue clay mud is encountered; at other places, as where the fresh 

 and salt water meets, sand-bars are found, of coarse sand; then 

 stiff clay, hardpan, shale rock, large boulders and other materials 

 are found at different localities. 



A word about the St. Lawrence River. In many ways it differs 

 from most rivers of the world, and this affects the work of dredging 

 somewhat. An ordinary river generally has deep slopes and grades 

 near its source, that mean great erosion of the bed and banks 

 by the swift current. Thus near the source the water becomes 

 saturated with soil, which is deposited in the level stretches of 

 the river and at its mouth, always interfering with navigation. 

 When such rivers are dredged, those portions fill up again with 

 the fine sediment, thus making the work of dredging almost con- 

 tinuous, as in the Mississippi and Missouri Rivers. The only other 



