48 BULLETIN 115, U. S. DEPARTMENT OF AGRICULTURE. 



for the standards to be raised above the crest of the wing walls in 

 order to secure elevation sufficient to raise the shutter. 



It will be noted from the plans that this is practically a sheet 

 structure with a small basin attached to the back to withstand the 

 erosion and pound of the falling water. The buttress construction 

 of this basin also braces the front walls. The plans show a double 

 3-foot opening check with small buttress walls at the sides of the 

 basin, used where there is drop in grade or the material of the banks 

 requires protection. For double openings the middle buttress wall is 

 not omitted, even though the conditions do not require the smaller 

 side buttresses. The constant dimensions for all this class of struc- 

 tures are given in figures, while the variable ones are lettered and 

 refer to the figures in the table under the letter given. 



Plate IX, figure 1, shows a combination of check and delivery struc- 

 tures as used by the Sacramento Valley Irrigation Co. Note the 

 inset panel cast in the concrete, upon which the number of the struc- 

 ture is carried. One gate has been numbered and the panel on an- 

 other gate is shown in blank. 



CHECK GATES, IMPERIAL WATER CO. NO. 1, CALIFORNIA. 



Plate IX, figure 2, shows a typical wooden check as used on the 

 main laterals, carrying 30 to 150 second-feet. This particular gate 

 has three bays, the two on the outside regulated by flashboards and 

 the middle one by a simple slide gate, with holes for a pin, which may 

 be locked. The upper and lower wings are identical, as are the cut- 

 off walls at both ends of the floor. Wings and cut-offs extend as far 

 below grade as the side walls extend above. Replacements on a well- 

 set ditch may be modified to the extent of making the depth of these 

 walls about one-half the height of the side walls above grade. The 

 floor usually is set 1 foot below the bottom grade line. The compa- 

 nies in the Imperial Valley use 1-inch redwood for the sheeting on 

 this class of structures, while the posts and sills are made either of 

 redwood or Oregon pine ''Douglas fir). These gates last 6 to 10 

 years. 



Note that the posts are all on the waterside. They pass through 

 the floor and are spiked direct to the sills. Diagonal braces extend 

 from the upper ends of the guideposts at both ends of the slide gate 

 down to the foot of the posts shown under the lower cap. No bat- 

 tens are used, as this silted water closes all cracks rapidly, and in 

 addition the gates are puddled in most thoroughly before water is 

 run commercially. In the foreground of the picture is seen a good 

 example of the use of brush riprap, described on page 11 for the 

 protection against eddying water. The structures of this company 

 are numbered with an ordinary, cheap grade of metal house num- 

 bers, which remain bright and are easily set on a wooden gate. 



