Costs 167 



steam-driven trenching machine is advisable, provided one can be 

 secured at favorable terms. But for shallow trenches in soil that 

 requires little or no pick work, excavation with a shovel is cheaper 

 than by machine. The cost of shovel trenching where the depth 

 does not exceed 4 feet is from 15 to 30 cents per cubic yard, equal to 

 from 4 to 8 cents per lineal foot for a trench 30 inches wide and 3 

 feet deep. Deep trenches should not be opened much in advance 

 of the pipe laying, because the caving of the side walls increases 

 rapidly after the earth is exposed to the weather. 



Hauling is a matter of some importance. Each length of pipe 

 should be laid on its side lengthwise of the wagon bed. It is cus- 

 tomary to haul about fifty feet of 12-inch pipe or twenty feet of 20- 

 inch pipe on a two-horse load. The pipe are packed in cars simi- 

 larly, on side and longitudinally with the car. 



The cost of pij^e distribution systems varies from $15 to $30 per 

 acre of land. Assuming 12-inch lateral lines 1000 feet apart, the 

 cost is about $13 per acre for these laterals and the main supply lines 

 may cost as much more. 



■ In the sewer contract referred to on page 153, the vitrified 

 clay tile cost 22' 1> cents per foot f. o.b. Tucson, while the pro- 

 posal was made to furnish 8-inch McCracken cement pipe at 15 cents 

 per foot. The clay drain pipe used at Thatcher in 1916 cost 20, 

 29>4, and 39 cents per foot, respectively, for the 8, 10, and 12-inch 

 sizes. The pipe was of the weight known as double-strength, the 

 12-inch pipe weighing 46.2 pounds per foot. 



Prices of pipe culverts, in place, in Pima County in 19 17 were 

 as shown in Table XXV. 



TABLE XXV. PRICES BID ON CULVERTS EOR PIMA COUNTY, 1917 



Quantity Size i Corrugated iron 



Feet Inches \ 



308 I 12 $ 432 



1232 ! 18 I 2340 



1280 24 3200 



McCracken pipe 



$ 200 

 1232 

 1935 



For large streams of water wdiich would require pipe greater 

 than 36 inches in diameter, cement-lined ditches are advisable*, 

 provided the line can be laid out with a suitable gradient. 



*See U. S. Department of Agriculture bulletin, No. 126, "Concrete Lining as 

 Applied to Irrigation Canals." 



