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THE BUREAU OF RECLAMATION has constructed 138 dams since its organization in 1902 and now is engaged in directing the largest construction program in its history, including 21 additional dams. Dams built by the Bureau range in size from simple, small diversion structures of a few feet in height to gigantic storage dams of unprecedented proportions.
Through the years since the Federal Government began construction of self-liquidating irrigation projects in the semiarid and arid section, the need for additional water has resulted in the construction of progressively larger and more complicated dams, until recently control of the largest rivers in the West has been undertaken. Outstanding structures of the Bureau are Boulder Dam on the Colorado River, completed in 1936, and Grand Coulee Dam on the Columbia River, now in construction.
Boulder Dam is extraordinary because it is the world's highest, rising 726.4 feet from the lowest point in its foundation to its crest. It has a total volume of concrete in the dam alone of 3,250,000 cubic yards and has created Lake Mead, a reservoir of 30,500,000 acre-feet capacity, by far the biggest so far. When completed, Grand Coulee Dam, while it will be only 553 feet in height, will be the most massive masonry structure in the world. It will contain about 10,250,000 cubic yards of concrete.
When the Bureau completed the 328-foot Shoshone Dam on the Shoshone River in Wyoming, in 1910, it was the highest dam in the world. Since then the Bureau three times has held this record. On its completion in 1915 the Arrowrock Dam on the Boise River in Idaho, then 349 feet but since raised 5 feet, was the world's highest. The Owyhee Dam on the Owyhee River, having a height of 417 feet, superseded Arrowrock on its completion in 1933, and Boulder Dam superseded all others in 1936'.
The work of the Bureau of Reclamation has many interesting features, but this book shall confine itself to a semitechnical discussion of dams and control works. Engineering practices have advanced greatly since the Bureau built its first dam, and it is felt that some part of the advance has resulted from the work here described. Review of the construction activities of the Bureau may prove valuable to the profession, to students, and others interested in the progress of design and construction.
The early practices of the Bureau have been outmoded and greatly altered. Such tremendous structures as Boulder and Grand Coulee Dams demonstrate in a remarkable manner the progress made. These dams, perhaps, are among the best examples of modern engineering. There is no thought, however, that additional improvements will not be made in future construction.
Older dams, like the Roosevelt Dam on the Salt River,
were constructed of rubble masonry, containing from 60 to 70 percent of stone laid by hand with mortar and spalls. The upstream faces of these dams were constructed of cut stone with comparatively thin, well-pointed joints. More recent construction involves concrete of well-graded aggregate through the entire body of the dam with the maximum size of cobbles definitely limited. Provisions are made for removing the heat generated by the setting of the cement; contraction joints are designed at regular intervals to restrict the cracking of the concrete, and the joints are grouted to form a monolithic structure.
Similarly, methods of analysis have been improved and knowledge of stresses for all types of dams has been greatly increased over the technical studies used in the design of early dams. An attempt has been made in the following descriptions to cover only the more important and exemplary types of dams constructed by the Bureau in its 35 years of activity, and to present only the more interesting and important technical studies. These latter subjects are covered in a group of special articles which describe experimental work being done by the Bureau. These studies, it is believed, have resulted in some of the advances mentioned earlier.
Articles descriptive of many of the dams have appeared from time to time in the Reclamation Era (formerly Reclamation Record) and their construction has been described in detail in the published annual reports of the Bureau, particularly in the ninth (1909-10) and fifteenth (1915-16) editions. Nearly all of the annual reports are now out of print and the stock of back numbers of the Reclamation Era in many instances has been exhausted. This, the second edition of "Dams and Control Works" therefore is in part a review and in part an initial presentation of its subjects. For more detailed and technical information on the structures described, reference is made to the file of published reports of the Bureau which may be consulted at any depository library and to the books and technical publications listed in the bibliographies.
The Bureau of Reclamation will be glad to consider requests from publishers who may desire to reprint or otherwise to make use of articles included in this book.
The administrative office of the Bureau of Reclamation, Department of the Interior, is in Washington, D. C, and is under the direction of John C. Page, Commissioner. The Bureau maintains its main engineering office at Denver, Colo., with Raymond F. Walter, Chief Engineer, in charge. This office has immediate supervision of all design and construction work. The construction is under the direction of Sinclair O. Harper, Assistant Chief Engineer. The preparation of plans and specifications and the design of all important structures are under the supervision of John L. Savage, Chief Designing Engineer.