SPILLWAYS FOR RESERVOIRS AND CANALS. 



35 



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. 



k- /£*-**- -g'«2& 



.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. 



