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All-American Canal Desilting Works
Adjacent to the All-American Canal Headworks, three desilting basins are laid off at an angle of 60 degrees from the intake canal and each is divided into half by a long V-shaped influent channel. The dimensions of each half-basin are 269 ft wide by 769 ft long. Each basin is designed to handle a maximum of 2,000 cfs and each pair of basins is fed by an influent channel. Twelve rotating scraper mechanisms are installed in each half-basin to collect and remove the silt that settles out of the water. The water depth is 12.5 ft. The velocity of water is about 0.25 ft/s. Silt deposited in the basins during the passage of water from influent to effluent channels is removed by means of 72 rotary-type scrapers, each 125 ft in diameter, which force the deposited silt into collecting trenches from which it is flushed into a system of sludge disposal pipes, to the sluiceway channel, and then into the Laguna Settling Basin about 2 mi south of Imperial Dam.
The designed desilting capacity at a canal discharge rate of 12,000 cfs equals 70,000 tons per day; 600,000 to 700,000 yd? of sediment are removed annually.
Gila Canal Desilting Works, Gila Gravity Main Canal
The Gila Canal Headworks were constructed at the Arizona end of Imperial Dam. Downstream from this structure, the desilting works for the Gila Gravity Main Canal were installed. The Gila desilting works consists of one concrete-lined basin with space allowed for the construction of two additional basins. This basin was designed for desilting a maximum flow of 2,200 cfs. It is formed by two levees extending perpendicularly to the axis of Imperial Dam on either side of the third gate structure of the Gila Canal Headworks. The basin is roughly 1,175 ft long, including inlet and outlet transitions. The bottom width ranges from about 115 to 104 ft between the transitions. The average depth of water is about 20 ft, and the average velocity is 0.66 ft/s. Flow from The basin is controlled by two sets of eight 7- by 16-ft fixed wheel gates, one set located above the other. The upper eight are for diverting and the lower eight are used during sluicing operations. The sluicing water is returned to the river by a curved channel 1,800 ft long. The Gila Canal desilting works are capable of removing about 8,130 tons per day.
1 Constructed and operated by the Imperial Irrigation District
The Imperial Irrigation District has constructed powerplants at Pilot Knot Check and Wasteway, and at Drop Nos. 2, 3 and 4 of the All-American Canal. Installed capacities of these plants are:
The district also operates the 189.1 MW steam plant at El Centro. The 75 MW axis steam plant at Yucca is operated by the Arizona Public Service Company, but the Imperial Irrigation District has rights to 25 MW of the plant's production. Imperial's electrical distribution system interties with the Department of Energy's Parker-Davis system.