Page 126


Page 126
Colorado River problem
Is Part Of,8
Full text
KELLY ON THE COLORADO RIVER PROBLEM 431 is determined by compactness, rather than by hardness and that the rock in question leaves nothing to be desired in the way of compactness. The cementing material is not strong enough to resist heavy erosion; spillway and power tunnels would have to be lined, but in foundations, even with the most ordinary precautions to prevent failure by displacement, the rock will certainly bear more than the load which it is safe to place on concrete in a dam. It may be interesting to note that common practice considered the safe maximum stress in concrete dams as 20 tons per sq. ft., until some of the high dams of the Reclamation Service were built, when it was found that the cost of maintaining that standard was prohibitive, and the limit was raised to 30 tons per sq. ft. The same experience resulted from the design of the high Boulder Dam; Mr. Davis and his Board of Engineers have designed that dam with a maximum stress of 40 tons per sq. ft., equivalent to 555 lb. per sq. in. The concrete will have to be unusually good to insure an ultimate strength of 2,000 lb. per sq. in. In other words, the factor of safety will be about 3.6 in the concrete. The loading assumptions used by the designers are conservative, but with the tremendous loads available for unexpected concentration in such a high dam, there is a risk in so far exceeding precedent which nothing but positive necessity can justify. The economic height for power dams in the Canyon Section can be shown to lie between 200 and 400 ft. Dams higher than 400 ft. can be justified only for storage or, perhaps, for the purpose of backing the water up to the next feasible dam site, and should not be permitted unless it can be positively proved that the full development of the river cannot be obtained without them. The writer does not consider it necessary or desirable to build a very high dam at Glen Canyon—probably not over 400 ft., and certainly not over 500 ft. Referring to the heading, "Increase of Low-Water Flow" (page 391), legal views of eminent authorities are available to prove that Mexico can never profit from the storage of water in the United States, but any one who will study the history of the relations of the United States with other countries, especially with those of the American Continent, will realize that the United States always sets aside legal arguments and settles on a basis of unreasonable liberality. It is certainly a wise precaution to obtain a treaty with Mexico to cover the question. Fortunately, conditions seem favorable at present for negotiating such a treaty and it is understood that preliminary steps are already under way. Mr. Davis makes two statements in his discussion which cannot be overlooked. In the first he says, "This emphasizes the real point at issue, that is, whether the immense resources of the Lower Colorado are to be retained in the control of the Federal Government or turned over to private corporations." Any one familiar with the Federal Water Power Act knows that it sets forth a complete Federal control—the product of more than twelve years' consideration by Congress. Nobody, as far as the writer is informed, has ever proposed less Federal control except certain advocates of municipal development who do not wish to be burdened by the Federal Water Power Act, and who have called forth the private monopoly specter in their efforts to obtain special privileges for themselves.

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