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



LATERAL HEADGATE, CALIFORNIA DEVELOPMENT CO., CALIFORNIA. 



The engineers of the California Development Co. have designed 

 standard plans for a reinforced concrete branch canal or lateral 

 headgate. These plans are based on their experience of 10 years 

 with wooden structures which these are designed to replace. The 

 plans (fig. 8) show a gate with a minimum amount of concrete, 

 heavily reinforced with steel to give the required strength. Un- 

 usual local conditions render great economy in concrete necessary in 

 this region, as it costs as high as $48 per cubic yard. For this reason 

 much time was spent in making a theoretically economic design. 

 The form work would be relatively expensive for this structure, and 

 in adapting the plans for a region where unit cost of concrete would 

 not be so great the cost of forms may be reduced by altering the 

 plans slightly. For instance, the division walls, now made of re- 

 inforced posts braced by similar members, could be made solid pier 

 walls; the arched supports for the operating platform might be 

 made slightly heavier of a reinforced rectangular-section slab; the 

 counterfort walls under the front wings might slope directly from 

 the upper edge to the floor, omitting the reentrant angle at the back. 



The cut-off walls of this gate are of wooden sheet piling extending 

 12 feet into the bed of the canals. In adapting the plans, light con- 

 crete cut-off walls may be used. The depth would be determined by 

 local conditions. For a canal well lined with cobblestones, there- 

 fore not in danger from erosion below the gate, a very shallow cut- 

 off will suffice. A good anchorage already is secured by the weight 

 of earth filling on the floor outside the walls and wings. 



The girdered floor and the counterfort supports to the side and 

 wing walls are features which may be adopted to advantage in the 

 design of other gates. The girders and counterforts are reinforced 

 to take the tension, thus enabling the intervening slabs to be made 

 much lighter than if the girders and counterforts were omitted. 



The shutters are of wood, constructed so that the main regulation 

 is effected with flashboards, but a similar board is attached to the 

 lower end of a stem so that the whole panel may be lifted as a single 

 unit by a rack-and-pinion or other lifting device. This allows the 

 water to be delivered either under or over the shutter or both. The 

 plans shown are for a 3-bay gate, while the bill of material includes 

 quantities for 3, 4, 5, and 7 bay structures. 



The development company delivers 30 to 150! second-feet of water 

 through these gates to the branch canals or laterals of the mutual 

 water companies of the Imperial Valley, who purchase water by 

 wholesale from the development company. All structures below the 

 headgate in the lateral are owned and operated by the mutual com- 

 panies. 



