CONCRETE LINING FOE IEEIGATION CANALS. 63 



The concrete was composed of a 1:3:6 cement, sand, and crushed 

 stone mixture, but whenever a well-graded crushed stone could be 

 secured sand was omitted and the concrete was made of 1 part 

 cement to 6 parts crushed stone from which all particles over 1| 

 inches in diameter had been excluded. 



In earth sections the lining of the sides and bottom was 4 inches 

 thick and had side slopes of If to 1. Expansion joints of corru- 

 gated iron were inserted every 16 to 20 feet along the sides and bot- 

 tom except in the bottom of the rock sections. These joints consisted 

 of pieces of corrugated iron cut into strips 4 inches wide containing 

 \\ corrugations, these being designed to lock the. edges of adjacent 

 sections and to prevent slipping. (See fig. 3, c.) 



The side walls in the rock sections were supposed to have a slope 

 of 1 to 4; but in many places where this would have necessitated the 

 blasting of large amounts of rock, walls were made almost vertical. 

 Heavy, collapsible forms of 2-inch lumber were used in placing con- 

 crete for the walls which approached the vertical. The concrete 

 was wheeled directly from the mixers and spread in uniform layers 4 

 inches thick over the bottom and on the sides of the easier slopes in 

 earth sections. Concrete placed within forms made of 4 by 4 inch 

 lumber was compacted by tamping and finished by working 24-foot 

 floats made of 2 by 6 inch timbers back and forth over the upper sur- 

 face of the forms. Sixty cubic yards of concrete per day were some- 

 times laid in this way by one gang working under favorable conditions. 

 The sides and slopes were finished with a coat of cement mortar 

 whenever the surface was rough enough to warrant it. 



The unusually high cost of this work was largely due to the diffi- 

 culty of preparing the rock cut for the lining and to the absence of 

 sand and gravel, which made it necessary to crush rock for the con- 

 crete. However, a greater factor than either of these was the added 

 expense due to the necessity of prosecuting the work during severe 

 winter weather. To do this the canal was roofed over for a distance 

 of 2,000 feet and the inclosed space warmed by specially constructed 

 heaters, using sagebrush for fuel. The nature of the temporary 

 roof and the method of heating are shown in Plate IV, figures 

 1 and 2. The cost of labor and material was as follows: 



Cost of labor and materials for lining Twin Falls North Side Canal. 



Laborers, per day of 10 hours $2. 50 



Drillers, per day of 10 hours 2. 75-3. 00 



Engineers (steam), per day 3. 00-4. 00 



Man and team, per day 5. 00 



Coal per ton, f. o. b. Milner 6. 50 



Cement per barrel, f. o. b. Milner 2. 59-2. 89 



Cost of crushing rock, per cubic yard 1. 10 



Cost of labor for placing concrete, per cubic yard , 2. 75 



