SPILLWAYS FOR RESERVOIRS AND CANALS. 
35 
Section Plan A-A 
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the others were led to a point 2 inches under water where air pressure 
could be relieved but back suction after priming was retarded by the 
high lift. The calculated capacity of battery is 5,200 second-feet and 
since the project has been but recently completed no tests of efficiency 
have been conducted. It is evident that the assumed discharge co- 
efficient was conservative. The siphons replace a system of flash- 
boards 6 feet high which were used before the dams were raised. 
Figure 13 repre- 
sents a smaller type 
placed at a number of 
points along the canal 
system of the Mount 
Whitney Power and 
Light Company in 
California. The op- 
erating head is 3.5 
feet, the cross section 
0.5 by 2 feet, and the 
approximate dis- 
charge 10 second-feet. 
Larger structures in- 
stalled in batteries of 
three units are also 
placed along their 
canal system (fig. 14) , 
designed along the 
same general lines, 
but capable of dis- 
charging up to 100 
second- feet. The 
only trouble found 
with any of these was 
due to ice and float- 
ing trash which clogs 
the intakes, but which 
is seldom a great men- 
ace, since the structures are rarely in operation during the period of 
freezing weather. Figure 7 shows the outline of a typical European 
design such as was installed by Gregotti and as designed to overcome 
the objection where trouble may be expected from ice and floating 
trash. The air regulation is so arranged that it can be manipulated 
to break siphonic action when the ordinary air duct intake is menaced 
by ice. Provision is also made for the drainage of the water-seal 
basin to prevent freezing and consequent stopping of the outlet. 
Floor of 
— *— J 3// »} 
f- 
Section B»B. 
Fig. 13. — Cross section of siphon spillway to waste small 
amouats of water. Located at isolated points on the 
canal system of the Mount Whitney Power & Electric 
Co. near Visalia, Calif. 
