Synopsis
This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1915 Excerpt: ...loss; (3) cost of operation and maintenance; (4) damages due to waterlogging and rise of alkali. When a new canal is to be constructed, as the extent and value of water loss by seepage can only be estimated, the choice between an unlined canal and a concrete-lined canal will depend largely on the first cost of construction. When the fall available is sufficient, a concrete-lined canal can be given a steeper grade than an unlined canal, which could not resist the resulting high velocity. The steep grade and the smoother concrete surfaces will give a high velocity with a corresponding smaller cross section; and as steeper side slopes can be used, the volume of excavation will be much smaller than for an unlined canal. This difference will be greatest on side-hill work and will reduce the cost of excavation sufficiently to balance at least part of the cost of lining and in hard material, excavated at a high unit cost, the concrete-lined canal may cost less than an unlined canal. Where there is not sufficient fall available to give the lined canal a steep grade, the comparison will not be as favorable; but even then the cross section of the lined canal will be smaller than that of an unlined canal on the same grade. In comparing the difference in cost, the smaller width of right-of-way and the smaller cost of structures on a concrete-lined canal should be considered. E. G. Hopson states that on the lateral system of the Orland project, in California, which includes 54 miles of ditches, covering 14,000 acres free from topographic irregularities, 28 per cent. of the total cost represents the cost of checks, drops and turnouts, which could be very much decreased if the system was entirely lined with concrete. Other benefits are the decreased cost of maintenance an...
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