TABLE OF CONTENTS [top]

From the Preface to the Third Edition:

Some of the chapters and appendixes have been revised extensively, while others reflect only minor revisions.

Chapter 1, “Plan Formulation,” has been condensed to briefly cover only the basic concepts of plan formulation. The authors of this chapter concluded that a detailed discussion of plan formulation was not appropriate because the primary focus of this manual is on design, not project planning. Also, a discussion of plan formulation, particularly with an emphasis on Federal plan formulation requirements, would not be of interest to a majority of dam designers. The chapter thus provides a brief discussion of the steps of plan formulation and some of the fundamental tests for the viability of proposed plans.

Chapter 2, “Ecological and Environmental Considerations,” has been revised to include a discussion on the management of fish and wildlife resources at, completed projects, in addition to new design considerations. An expanded section on water quality implications to dam design and operation is also included.

Chapter 3, “Flood Hydrology Studies,” has been completely revised, including incorporating the previous appendix A, “Estimating Rainfall Runoff’ from Soil and Cover Data,” into the chapter. Reference to the Soil Conservation Services’ curve number approach for assigning infiltration losses, the triangular unit-hydrograph approach, and all discussions and plates providing guidance for estimating probable maximum precipitation have been eliminated. These topics have been replaced by a treatment of infiltration losses as actually applied by the Bureau of Reclamation, expanded consideration and guidance relative to the development of unit, hydrographs using the dimensionless unigraph and S-graph approaches, and specific reference to the National Weather Service’s Hydrometeorological Report series as the basis for developing probable maximum precipitation estimates for the contiguous United Statues.

Chapter 4, “Selection of Type of Dam,” includes classification of types; physical factors governing selection of type; and legal, economic, and esthetic considerations.

Chapter 5, “Foundation and Construction Materials,” has been updated to incorporate current standards in foundation and construction materials investigations. A reservoir studies section has been added to the section on scope of investigations. The sections on soil and rock classification have been updated to reflect current standards, and a new section on engineering geophysics has been added to summarize the capabilities of these methods. The sections on subsurface explorations and sampling have been revised extensively to represent, new technology. The logging of explorations has also been revised to reflect current standards, and the field and laboratory test section has been updated. Changes in soil mechanics terminology and soil testing procedures generated by revision of the Bureau’s Earth Manual are reflected in this chapter. The previous table 8, “Average Properties of Soils,” which is now table 5-1, was recompiled to include laboratory test results obtained since the last edition. Figure 5-14, “Permeability of Soils,” was added to this edition to illustrate ranges of permeability measured on compacted soil specimens tested at the Bureau’s laboratory in Denver. The bibliography has been updated to include selected sources of information for foundation and construction materials investigation.

Chapter 6, “Earthfill Dams,” has been revised to update terminology and reflect design philosophy, procedures, and standards that have evolved since 1974. The major change is greater emphasis on internal filtering and drainage to control seepage and internal erosion within embankment dams. New figures have been added that show current dam embankments that have been designed and constructed by the Bureau of Reclamation. Other illustrations have been replaced or revised to reflect current thinking and technology. Liberal reference is made to design standards that have been developed as guides for Bureau engineers.

Chapter 7, “Rockfill Dams,” required only minor revisions; however, the Bureau does not have extensive experience with the design and construction of rockfill dams. Design and construction procedures for rockfill dams have changed over the last two or three decades and continue to do so. The chapter gives a good general background for the design of rockfill dams; however, the designer should also refer to the literature on the subject.

Chapter 8, “Concrete Gravity Dams,” now includes additional topics, clarification, and more detail. This chapter has also been revised to address concerns for concrete dams of any height. Sections on material properties and foundation considerations have also been added. More complete discussions are now included for forces acting on the dam, requirements for stability, and stress and stability analyses. Discussions addressing the analysis of cracked dams have been clarified and expanded to include analysis during an earthquake. Also, a general iterative approach for cracked dam analysis, applicable for static and dynamic conditions, is now included.

Chapters, 9 and 10, The “Spillways” and “Outlet Works” respectively, now include two new hydraulic designs for energy dissipators. These designs are a modified low Froude number basin as an alternative to basin 4 design, and modifications in the design criteria for baffled apron spillways to permit their use for higher unit discharges. Other contemporary spillway concepts are introduced, although design criteria are not included because they are still under development. Included in this category are labyrinth weirs where large flows must be discharged in a limited space such as a narrow canyon, and the use of air slots (aerators) in spillways where there is high potential for cavitation damage. Plunge-pool design criteria have been somewhat improved by the addition of several references to recent research. The suggested method for calculating the discharge under radial gates has been revised to reflect up-to-date criteria developed by the U.S. Army Corps of Engineers, Waterways Experiment Station. The section on siphon spillways has been omitted from this edition because they are seldom used as flow control structures for dams. The bibliography has been revised by the removal of references that were hard to obtain and by the addition of many new references that reflect the current state-of-the-art.

Chapter 11, “Diversion During Construction,” topics include diversion requirements; methods of diversion; specifications requirements; and a bibliography.

Chapter 12, “Operation and Maintenance,” now includes additional topics, clarification, and more detail. The new topics added are “Changes in Operating Plan,” which addresses modification to a structure to add additional storage or to change the purpose of allocation of storage; “Emergency Preparedness Plan,” which addresses instructions to an operator during emergency situations; and “Dam Operators Training,” which outlines the requirements for the training of operators to assure that operation and maintenance of a facility are performed in an accurate and responsible manner.

Chapter 13 is a new chapter dealing with dam safety. Although dam safety is always an underlying consideration in the design, construction, operation, and monitoring of a dam, the passage of legislation on Safety of Dams has placed additional emphasis on dam safety; and the inclusion of a chapter on this subject was believed to be important. This chapter presents procedures and references to other procedures for the evaluation and analyses of dam safety issues for both new and existing dam structures.

The appendix designations have also been revised.