Page 125


Page 125
Colorado River problem
Is Part Of,8
Full text
430 KELLY ON THE COLORADO RIVER PROBLEM storage needed in the lower river in the final development is in the lowest reservoir that will give sufficient storage, so that no power will be lost owing to the difference in the power and irrigation demands. Mr. Davis' discussion makes it necessary for the writer to point out again that he is not committed to his plan, and that it was used simply as an illustration. A better plan can doubtless be developed when the necessary data are available. In discussing "Poor Rock in Glen Canyon" (page 390), Mr. Davis emphasizes the writer's presumption in differing with his eminent Board. The writer questions whether there is much difference between his own views and those of the Board regarding the quality of rock at Glen Canyon. The report of the Board which examined this site was signed by Messrs. F. E. Weymouth, F. L. Ransome, L. C. Hill, and A. J. "Wiley (three engineers and a geologist), on December 20, 1922. The following is quoted from the report: "11. The Jurassic sandstone has been fully described by Gregory, Bryan, and others. It is a fine-grained, very uniform quartzose sandstone which appears to owe its reddish tint to the superficial redness of certain individual grains. The grains are imperfectly cemented and the whole resembles in hardness the type of soft brick known to the trade as salmon brick. It crumbles under shock, such as that of ordinary blasting, and small fragments can be crushed to sand between the fingers. Notwithstanding its softness the rock stands remarkably well in the canyon walls, forming large, smooth cliffs that rise for 1 000 ft. or more above the river, and which in places are within 5° of being vertical. * * * * * * * * * * * "13. As pointed out by Dr. Bryan the Jurassic sandstone is too soft and too easily broken on corners and edges to make good building stone, and is entirely unsuitable for use as concrete constituent. In large masses, however, it successfully resists the weight of the towering canyon walls and shows no signs of failure at the base of the cliffs where these come down to the water's edge. Under the atmospheric conditions prevailing at the canyon, moreover, the sandstone in spite of its softness withstands the action of the weather remarkably well. Some of the smooth walls must have stood without appreciable change for centuries. * * * * * * * * * * * "30. The abutments for a gravity type concrete dam are fully exposed, and the foundation is indicated by a diamond drill boring. Both are of a quite uniform soft sandstone which is not hard enough for a building stone, but probably will be found to have sufficient strength to support a concrete dam." As far as the writer can ascertain, no other Board report on the subject has been made, but apparently one member of the Board expressed somewhat modified views about a year later, for Mr. Weymouth, in his report of February, 1924, quotes from a letter of November 27, 1923, by Mr. Wiley as follows: "It does not seem feasible to build any type of masonry dam of the necessary height for effective storage on the soft sandstone at Glen Canyon, at least no type or height requiring maximum pressures of more than 20 tons per square foot should be used." A few years ago the writer spent four days examining this dam site. Evidence of bearing power is furnished by the cliffs which rise nearly vertical to a height of 1,000 to 1,500 ft. It may be well to point out that bearing power

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