ArizoiNA Agricultural Experiment Station 309 



Recently a 50,000-gallon tank was designed in this office. The walls 

 are 6 inches thick of 1 :2 :4 gravel concrete, washed inside and out with 

 two coats of neat cement. When put in service, the tank was filled one- 

 third full of water and allowed to stand 24 hours; it was then filled 

 two-thirds full and allowed another day's rest ; then it was filled full. 

 Much of the lower half of the surface sweated considerably after the 

 second and third fillings, the upper half scarcely at all, and after fifteen 

 c'ays all sweating ceased. Hydrated lime was used in all but one ring of 

 the concrete. The eft'ect on the water tightness was sufficient to justify 

 recommending it. 



If the tank is to be used for tops fuel oil, it should first be made to 

 hold water for at least two weeks until it is thoroughly watertight. The 

 water appears to have an action causing colloids in the concrete. It is 

 not to be recommended that concrete tanks be built for storing gasoline 

 or engine distillate. 



additional field at university farm 



Early in 1916 this Department was asked to make plans for the 

 grading of a new field and for an extension of the cement pipe line at 

 the University Farm. A contour survey was first made and platted and 

 the grading was designed with a view to equalizing the cuts and fills 

 and to make the haul a minimum. While this method has not been con- 

 sidered necessary by farmers, it is advisable whenever a competent sur- 

 veyor is available. The lands were graded to several slopes so that a 

 study can be made of the relation between the slope and head of water 

 and the "efficiency of irrigation," that is, the uniformity of distribution. 

 Six hundred and thirty feet of 12-inch pipe and 570 feet of 16-inch 

 pipe were used in the extension of the pipe line. In the old pipe line 

 the water was discharged through notches in the sides of rectangular 

 concrete boxes. One of these boxes was placed at the middle of the 

 head end of each land making the boxes 36 feet apart. In part of the 

 new pipe line similar boxes were used, and in the remainder of the line 

 cement pipe risers* and California alfalfa valves were used. These 

 risers are made by cementing a joint of pipe into the top of the pipe 

 line, so as to make a tee, and the valve frames are cemented into the tops 

 of the risers. 



Because of the flat slope in which this pipe line was laid it was im- 

 portant to know in advance just what the loss of head would be. Tests 

 were made on the old pipe line and it was found that in straight sections 

 without outlets the loss of head was the same as is given in friction 



♦See BuL 236, Office of Exp. Sta., U. S. D. A. 



