AZ vs. CA:04 California Exhibits, Vol. IV; Nos. 151-192

page 36

36 THE ALL-AMERICAN CANAL. The maximum demand for irrigation water will determine the canal capacity. The maximum demand is expected in June and July. In these months the diversion from the river should be in such amount that if all the water were delivered without loss in transit it would cover the entire cultivated area in each of these mbnths to a depth of 0.60 foot or 7.2 inches. The duty of each second-foot of water diverted would, if expressed otherwise, be 100 acres. The canal to supply the desired amount of water to a cultivated area of 900,000 acres in Imperial Valley should have a capacity of 9,000 seconid-feet. For the Yuma project, with some allowance for expansion beyond the limits generally indicated, a maximum diversion of 1,600 second-feet has been assumed. This is the amount for which the Reclamation Service desires that capacity be provided and for which the original project canal was constructed. The required canal capacity, therefore, of 10,600 second-feet results, from, the Laguna Dam down to the point at the siphon drop where the Yuma water is to be delivered to a separate canal and 9,000 second-feet for the all-American canal below this point to the upper mesa canal heading where the main supply for the east mesa would be taken off. The board, upon request of the Directors of Imperial Irrigation District, submits as an alternative the estimated cost of constructing the canal at first at a capacity of only 6,000 second-feet to meet the immediate needs of the district. The structures for this alternative have, however, been planned at full capacity to meet early future requirements. The power plants would be the same as for a full-capacity canal. METHODS OF CONSTRUCTION AND UNIT COSTS. The work of excavating the canal should be done to the maximum extent possible by machinery. The climatic conditions are not favorable for securing good results with ordinary labor. For work of the magnitude of an all-American canal, particularly for the deep uniform excavation westerly from Pilot Knob, special methods or types of machinery and appliances may be designed to do the work expeditiously and economically. It is possible that such methods or machinery can be perfected and brought into successful operating condition, and that thereby the cost of the work can be somewhat reduced. Nevertheless, it would not be safe to assume other methods of construction as the basis for a cost estimate than such as have been standardized by experience. It would be useless to speculate as to what the operating and plant costs of special types of such machinery would be when, perhaps after considerable experimentation, they have been brought into a condi-