AZ vs. CA:24 California Exhibits, Vol. XXIV; Miscellaneous

page 68

68 PROBLEMS OF IMPERIAL VALLEY AND VICINITY. with a similar set which will be placed near Araz, will not alone serve their prime purpose as sluice gates but will also facilitate the discharge of storm water when there is large inflow from the hill region. ¦ This provision for handling the storm water is suggested by the large reservoir capacity represented by the 17 miles of canal from the Laguna Dairi to the proposed power station at Pilot Knob. All along this portion of the canal the left or river bank thereof will be a high embankment, as already described. Against this embankment water could rise 3 or possibly even 4 feet above the ordinary high-water line without serious menace. If a storm should occur near the head of the canal with a large delivery of water into the canal, such a rise might turn some water upstream, back into the desilting channel, and thence into Colorado River. While this is occurring, preparation would be made at all the sluice gates to open the same when necessary. The opening of those at the Luguna Dam would stop the inflow of river water into the canal; those near the l|-mile point and those near Araz would be opened to. relieve the canal of storm water. To prevent damage to the canal by the deposit in it of the coarse material which a cloudburst may sweep along in the beds of the sand washes which this part of the canal crosses, the canal will be closed where feasible against these by means of substantial embankments or barriers above which the flood occasioned bj such a cloudburst will be pocketed. Interconnection will be provided so far as practicable from one sand wash to the next, and at selected points the barriers will be provided with concrete crests and protected slopes or drops to the canal, so that when the basin behind them is lull they will discharge over the barriers into the canal. In this way a number of pockets will be provided for the interception of sand, travel, and cobbles, and these can hereafter be increased in extent y adding to the height of the overfall barriers. THE CANAL FROM SIPHON DROP TO PILOT KNOB. At the Siphon Drop the water from the Yuma project will be dropped, as explained, to a lower level, while the water for Imperial Valley will be held at grade. The All-American Canal, strictly speaking, will begin at this point. It will follow rather difficult ground, generally near and finally well in among the outlying hills and knolls which are features of the higher ground between a number of sand washes. An agreement will be necessary with the Southern Pacific Co. in order to secure permission to encroach on its right of way. In addition a bridge will have to e provided for the main line on the Southern Pacific Railroad, and one for the Inter-California Railroad. In this section, too, the canal is to have a freeboard of at least 6 feet. At the lower end of this section there will be a rode cut or tunnel through a spur of Pilot Knob. Adjacent to and either above or below this spur the Pilot Knob power station will be located. At a convenient point below the power house offtake there will be a controling gate in the canal. By means of this the flow in the canal to the westward will be regulated. Any surplus water will be discharged either through the waste gates at Araz or through the power house offtake canal and a by-pass, which is here to be provided.