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



forms, which were also used on tangents, resulting in a much larger 

 number of joints on the straight portions than good practice warrants. 

 The joints were spaced 6 feet apart, and an attempt has been made 

 to cover the seams with a coating of cement mortar. It is claimed, 

 however, that these will eventually become filled with sediment, 

 but the daily and seasonal contraction and expansion usually tend 

 to enlarge rather than to decrease then width. 



Plate V, figure 2, shows the forms used for back-filling with 

 puddled earth to prepare this canal for concrete lining. In Plate 

 VI, figures 1 and 2, these forms have" been removed and the channel 

 is ready to receive the forms used in placing the concrete, as shown 

 in Plate V, figure 2. Additional information on construction methods 

 used with other useful data are to be found elsewhere. 1 



NORTHERN PACIFIC IRRIGATION CO., KENNEWICK, WASH. 



During the winter of 1910-11 this company lined 22,500 feet of 

 ditches on the "Highlands" at Kennewick to eliminate heavy seepage 

 losses. The soil through which these ditches are built is principally 

 a fine sandy loam overlying gravel at a depth of 18 inches to 2 feet. 



One ditch 10,800 feet long, 3 feet wide on the bottom, with. side 

 slopes of \ to 1 and a vertical depth of 26 inches, is designed to 

 carry 18 second-feet. Another ditch having in part a bottom width 

 of 3^ feet, side slopes of \ to 1, and a vertical depth of 19^- inches is 

 designed to carry 14 second-feet. This ditch is reduced to a bottom 

 width of 2 \ feet, but with the same side slopes and depth as the upper 

 part. The concrete used was a 1:3:4 mixture of cement, sand, and 

 crushed rock. 



In preparation for lining, center grade stakes were set and the 

 bottom of the ditch brought to grade. Scantlings 2 by 4 inches 

 were then placed across the bottom of the ditch at 12-foot intervals 

 at right angles to the center line and flush with the subgrade. Three 

 forms 12 feet long (PI. VII, fig. 1) were then set in the ditch on the 

 cross strips and centered. Earth was shoveled and tamped behind 

 the forms to secure the desired section. There were 14 men in a 

 crew on this work. 



After the earth sections were prepared in this way, 2 by 2 inch 

 screeds (PI. VII, fig. 2) were placed at intervals of 5 feet 8 inches 

 and upon them forms 6 feet long were set on every other space. 

 The concrete was mixed with a one-third yard mixer, wheeled to 

 place and dumped on planks laid on top of the forms. It was then 

 shoveled behind the forms and lightly tamped. Strips of sheet 

 iron were inserted behind the forms to protect the slope while the 

 concrete was being put in and also to prevent a too rapid loss of 

 water from the mixture by its contact with the drier earth. These 



1 Brit. Columbia Dept. Agr. Bui. 44 (1912). 



