WOOD PIPE FOR CONVEYING IRRIGATION WATER. 19 



The Snake River crossing of the Kings Hill project, near Bliss, 

 Idaho, and the new trestles of the Denver Union Water Co., afford 

 good examples of such cradles (fig. 7, C). 



The 84-inch pipe of the Pueblo, Rocky Ford Irrigation Co. is in 

 places supported on rock cradles set about 15 feet apart. 



ANCHORING PIPES. 



In order to secure surface pipes against water thrust at sharp 

 horizontal curves, and to guard against the tendency to creep on 

 steep inclines, anchorage in some manner is sometimes necessary. 

 One method of anchoring a 44-inch pipe, as well as the way of de- 

 signing an angle too sharp for the curvature of wood pipe, is illus- 

 trated by Plate IV, figure 2. Another method is to build around 

 the pipe a pier or mass of concrete or masonry to serve as anchorage. 



LOCATION OF CONTINUOUS STAVE PIPE LINES. 



The location of a pressure pipe line is very often a simple matter, 

 particularly where the distance traversed is short, but in the case 

 of long lines of wood pipe a proper and satisfactory location may 

 involve a number of important considerations. This is particularly 

 true if the line is to traverse a rough, mountainous region. Many 

 such pipe lines have been built without due knowledge or apprecia- 

 tion of the importance of certain factors, and failures or unsatisfac- 

 tory service may frequently result from faulty location. 



As a rule, a pipe line must follow more or less closely the varia- 

 tions of the ground surface, but in both plan and profile sharp curves 

 should be avoided as much as possible. The introduction of sharp 

 curves tends to increase the cost and difficulty of construction as well 

 as of maintenance and repairs and to decrease the carrying capacity. 

 Horizontal and vertical curves should not be placed in the same 

 section of pipe, and a tangent between curves is always desirable. 

 The degree of curvature permissible depends largely on the diameter 

 of the pipe and upon the thickness and kind of staves. A radius of 

 60 times the diameter of the pipe is usually taken as a measure of 

 allowable curvature, though sharper curves are not uncommon. 



A wooden pipe should be located so as to be under all conditions 

 entirely below the hydraulic gradient, and in making extensions, or 

 in taking off branches at any time from a line already established, 

 care should be taken not to lower the hydraulic gradient so as to 

 leave the original pipe above it. Carelessness with reference to these 

 considerations has in some instances been the cause of serious damage 

 and expense. 



On the point as to what the minimum distance below the hydraulic 

 gradient should be, engineers differ in opinion. Assuming that pres- 

 sure sufficient to keep the staves well saturated is necessary to pre- 



