68 BULLETIN 126, U. S. DEPARTMENT OF AGRICULTURE. 



1 barrel of cement to 7 full barrels of the same size of aggregates when mixed together. 

 If broken stone is used, it must be hard, clean, and heavy, having at least a specific 

 gravity of 2 and screened into three different sizes. None of the gravel is to exceed 

 2 inches in diameter. The mixture of such sizes will be in the proportion determined 

 by the engineer. All of the rock must be of such size that it will pass through a screen 

 with a 2-inch square mesh. 



The seam shown in Plate IX, figure 1, is typical of many such seen 

 in canal lining in that it gradually diminishes in width from the top 

 to the bottom of the side lining. Plate IX, figure 2, shows a fracture 

 extending not only through the concrete but also through a diabase 

 rock some 14 inches long and 4 to 6 inches thick which was embedded 

 in the concrete. The natural cleavage of this rock, it may be observed, 

 was nearly at right angles to the rupture as made by the contraction 

 of the concrete. 



The placing of the concrete lining against the uneven rock surface 

 served to anchor the lining and prevent contraction, and this same 

 foundation condition doubtless added much to the strength of the 

 lining as a whole. Notwithstanding this fact, however, ruptures 

 have occurred at intervals of 28 feet or more throughout the lining. 

 The seams created by these ruptures varied in width from one- 

 twelfth to one-half inch or more at a time when the temperature of 

 the air was 50° and that of the water in the canal was 42° F. 



LOWER YAKIMA IRRIGATION CO., RICHLAND, WASH. 



The canal of this company parallels the Yakima River for several 

 miles, where the earth sections run mainly through coarse gravel, 

 bowlders, or shattered basaltic rock. The remainder of the system 

 is very largely built through sand . In the unlined channel the seepage 

 losses were excessive, and through the sand it was also difficult to 

 maintain the ditch owing to its tendency to fill up both by drifting 

 and on account of the flat side slopes which the sand naturally as- 

 sumed under the action of water. The lining was intended, there- 

 fore, not only to reduce the loss of water but to increase the carrying 

 capacity of the ditch and render it more stable and easy to maintain. 

 About 5 miles of the ditch was lined in 1910. The company furnished 

 all materials used and prepared the channel for lining, but the other 

 work was done by contract. 



In preparing the ditch, center stakes were set about 1J inches 

 above grade, to which the excavating was roughly done with teams 

 and scrapers. At intervals of about 25 feet along the bottom of the 

 side slopes stakes were set to grade, and from these the top slope 

 stakes were set by the use of a slope triangle. Nails were driven 

 into the grade stakes and chalk lines were stretched on them parallel 

 to the ditch. Trimming to these lines was done then with square- 

 pointed shovels and the slopes and bottom scraped to smooth sur- 



