The Head-Works of the Imperial Canal

The diversion of water from the Colorado River for the irrigation of lands in the Imperial Valley, California, has been fully d escribed in papers previously submitted to the Society.‡ In 1916, mainly on account of difficulty with the silt carried by the Imperial Canal, it became necessary to make considerable improvements which included an up-stream extension of the canal for about 1 mile and the building of an intake structure which is known as the Rockwood Gate . This gate was designed for erection on a sand foundation. It is a structure with seventy-five openings between piers and extends for more than 600 ft. along the bank of the river. For about 400 ft. of this distance, the foundation is fine sand which has been prevented from being piped out from under the gate by placing upon it, without pile support, the floor of the structure, heavily weighted by a box of sand carried by the piers which sub-divide the gate into sluice-like openings. There has been no trouble with settling since its completion.