Ch. 21] COST OF CLEANING CANALS 375 



Canal was cleaned by more conventional methods in 1946 at a cost 

 of approximately $37 per mile. 



The Turlock Irrigation District, in California, has a total of 125 

 miles of lined canals in which occurs a moderate amount of silting. 

 The presence of the silt, however, as in all lined canals, encourages 

 the growth of algae and certain types of mosses and leads to decreases 

 in the canals' carrying capacities that are greater than the reductions 

 in cross-sectional areas would indicate. For this reason, the district 

 removes the silt deposits and other debris at the close of the irriga- 

 tion season each year. Equipment developed in the district, consist- 

 ing of a truck equipped with a boom and scraper arrangement that 

 minimizes the hand work required is used, and the average cost of 

 cleaning all sizes of canals is $50. 



On the Shoshone project in northwestern Wyoming, 3.8 miles of the 

 Deaver Canal (194 second-feet) were cleaned with a dragline in 1945 

 at a cost of about $1,020 per mile. This figure includes allowance for 

 depreciation on the equipment. Small laterals were cleaned on the 

 Shoshone project in 1947 with a one-way Chatten ditcher pulled with 

 a tractor, at a cost of about $50 per mile. Excavation in cleaning the 

 laterals with this machine averaged about 1 cubic yard of material 

 for every 15 linear feet. 



The Bucyrus-Ruth excavator, or Ruth dredger, is used on many ir- 

 rigation projects for cleaning laterals and small unlined canals. On 

 the Belle Fourche project in South Dakota, 29 miles of laterals were 

 cleaned in 1946 with a Ruth dredger, at a cost of $85 per mile. Also 

 in 1946, approximately 8 miles of laterals on the Milk River project 

 in northern Montana were cleaned at a cost of about $147 per mile. 

 Between 50 and 75 miles of laterals on the Lower Yellowstone project 

 in eastern Montana were cleaned each year during the years 1932 to 

 1946, inclusive, at an average cost of $75 per mile. Depending on 

 the size of the lateral and the variation of silt deposit, weeds, willows, 

 tules, and other vegetative growth, the cost of cleaning laterals with 

 this type of excavator varies from $50 to $150 per mile of lateral. 



Before the desilting works were installed for the Imperial Irrigation 

 District at Imperial Dam, the cost to remove silt from its canal system 

 averaged over $700,000 annually. This was approximately $250 per 

 mile for the lengths of canals and laterals cleaned each year in the 

 entire system. The cost of silt removal from the distribution systems 

 since construction of Imperial Dam and desilting works has been much 

 less than the previous cost, and the deposit in the All-American Canal 

 itself has been negligible. Suspended material carried in the Yuma 

 Canal before Hoover and Imperial dams were built was 30 times the 



