Pipe Line Structures 



149 



sometimes, where the slopes are steeper, by using valves in the 

 upward-flow branches of the standpipes. 



Many citrus groves in California are on land which has a natural 

 slope of 10 to 40 feet per 100 feet. It is impracticable to run the 

 furrows down the slope; they are made to follow the contours ot 

 the land with just a little fall. The cement-pipe head ditches for 

 these orchards are run down the hillsides, often following a ridge, 

 with overflows at such intervals that the fall from one to another 

 is not over six or eight feet. A\'ater is taken from riser valves, 

 through hoods, and is run along the contours to both right and left 

 of the head ditches. This practice is well exemplified in the La 

 Habra Hills, where the soil is of a clayey composition and resists 

 erosion. 



Terracing and heavy grading have the disadvantage that the 

 good soil is removed from certain parts of the ground and on 

 such places the trees or other vegetation may be stunted and 

 unproductive. 



The overflow system may be called the open system, while the 

 svstems at Continental are closed, that is, each riser requires a 

 valve. The closed system is better adapted to uneven land, and it 

 permits of the use of slightly smaller pipe sizes. The open system 

 requires more carefully executed surveys. 



Riser valves are of brass. In some makes sheet rubber gaskets 

 are used, in others braided hemp boiled in tallow. The valves are 

 set, sometimes on the groove ledge at the top of the riser, some- 

 times in the riser so that the top of the valve handle is at the level 

 of the top of the riser. Two to one mortar is used for setting the 

 risers and valves. 



10-foot contours and layout of main supply line and laterals. 



