100 Years of Embankment Dam 

Design and Construction

in the 

U.S. Bureau of Reclamation

Bureau of Reclamation History Symposium

at

University of Nevada - Las Vegas

June 18-19, 2002

by

Richard Lyman Wiltshire, P.E.

Civil Engineer, Principal Designer

Geotechnical Services Division, Group 1

Technical Service Center

Bureau of Reclamation

U.S. Department of the Interior

Denver, Colorado

September 2002
100 Years of Embankment Dam Design and Construction 

in the U.S. Bureau of Reclamation

ABSTRACT

The design and construction of earthfill and rockfill embankment dams in the

Western United States have evolved dramatically during the past 100 years (1902-

2002). The U.S. Department of the Interior’s Bureau of Reclamation (Reclamation)

has played a significant role in that evolution of embankment dam engineering,

construction, and dam safety during the 20th Century. There are now over 240

water-storage embankment dams in the Western United States that were designed

and constructed by Reclamation. The list of civil engineers and other professionals

who have helped to design and build Reclamation’s embankment dams is lengthy

and highly regarded. 

This paper discusses Reclamation’s embankment dam design and construction

organizations and how they have evolved during the past century. Starting in 1902,

Reclamation's embankment dam design and construction approach involved one

engineer in charge of all phases of the work, from development of the project all the

way through design and construction of the dam and appurtenant structures. 

Embankment dam design and construction were then based largely on previous

experience with dams that had been successfully designed, built, and operated

without failure. Since that beginning, the design of embankment dams has evolved

to now include: site investigations and engineering geology; paleohydrology;

evaluation of foundation conditions and treatment; laboratory investigations of

foundation and borrow materials; geotechnical analysis of design criteria such as

seepage, filters, slope stability, deformation, and seismic behavior; instrumentation

and performance monitoring; and construction equipment, methods, and

management. Reclamation's embankment dam design and construction history can

be separated into five periods. Period I runs from 1902 to 1918; Period II extends

from 1919 to 1933; Period III covers 1934 to 1944; Period IV includes 1945

through 1975; and Period V runs from 1976 to the Present (2002). 

In summarizing Reclamation’s embankment dam design and construction history,

many of the notable embankment dams designed and constructed by Reclamation

during each of those periods are discussed. The last 100 years have seen the design

and construction of embankment dams develop from the relatively simple

homogeneous or two-zone earthfill embankments designed at the beginning of the

20th Century into the extremely complex, highly analyzed, well-instrumented zoned
earthfill and/or rockfill structures that are the embankment dams of the 21st Century. 

A central component of the evolution of engineering of embankment dams has been

the birth and maturation of geotechnical engineering as a civil engineering specialty. 

The evolution in construction equipment during the past 100 years is also discussed

in the paper. The development of Reclamation’s publications, such as the Earth

Manual, Design of Small Dams, and the Design Standards, is also discussed. The

near failure of Fontenelle Dam, the failure of Teton Dam, and the lessons learned

from those events are discussed in the paper. And, the post-Teton changes in

Reclamation’s embankment dam designs and in the organization are discussed. 
1

 Numbers in brackets refer to References located at the end of this paper.

1

INTRODUCTION

The design and construction of earthfill and rockfill embankment dams in the Western United

States and throughout the world have evolved dramatically during the past 100 years. The U.S.

Bureau of Reclamation (Reclamation) has played a significant role in that evolution of

embankment dam engineering, construction, and dam safety. There are now over 240 waterstorage embankment dams in the Western United States that were designed and constructed by

Reclamation during the 20th Century, which was the most intensive period of dam building the

world has ever seen. The list of embankment dams built by Reclamation includes many of the

most innovative, largest, and highest dams of their eras. The list of civil engineers and other

professionals who have helped to design and build Reclamation’s embankment dams is lengthy

and highly regarded. 

Reclamation is currently organized into five Regions across the 17 western states and the

Washington and Denver Offices. The five Regions, which have performed almost all of the dam

construction work, are: 1) Pacific Northwest, 2) Mid-Pacific, 3) Lower Colorado, 4) Upper

Colorado, and 5) Great Plains. The Denver Office includes the Technical Service Center, the

current name of the engineering organization that has performed most of the embankment dam

engineering and design work. 

This paper summarizes Reclamation’s embankment dam design and construction history. The last

100 years have seen the design and construction of embankment dams develop from the relatively

simple homogeneous or two-zone earthfill embankments designed in 1904 or 1905 into the

extremely complex, highly analyzed, well-instrumented zoned earthfill and/or rockfill structures

that are the embankment dams of the new millennium. This embankment dam engineering

evolution has also involved the growth of several related disciplines, including engineering

geology, seismology, hydrology, hydraulic engineering, instrumentation engineering, mechanical

engineering, and electrical engineering. A central component of the evolution of the engineering

of embankment dams has been the birth and maturation of geotechnical engineering as a civil

engineering specialty. The use of computers and computer programs for the analysis and design

of embankment dams became standard practice within a fairly short time after they were

developed by geotechnical engineers. Another component of this evolution has been the

development of larger, faster, more powerful, and more efficient earthwork construction

equipment. The paper also discusses the design and construction organizations within

Reclamation and how they’ve changed during the last 100 years. Reclamation’s publication of its

well-known engineering books, such as the Earth Manual [1]1 and the Design of Small Dams [2],

is noted. Lastly, the successes and failures that occurred during the last 100 years of

Reclamation’s embankment dam design and construction history are discussed, and the lessons

learned from those experiences are summarized.

In telling the story of the evolution of Reclamation’s embankment dam engineering, the paper
2

separates the 100-year history into five periods, which are partly based on noteworthy events such

as World Wars I and II and the failure of Teton Dam in 1976. Period I runs from 1902 to 1918;

Period II extends from 1919 to 1933; Period III covers 1934 to 1944; Period IV includes 1945

through 1975; and Period V runs from 1976 to the Present (2002). This paper examines the

embankment dam design and construction changes that occurred during each period. 

Representative and remarkable/notable embankment dams from each of the five periods are

discussed. A few problems, some significant, occurred during the construction and/or subsequent

operation of Reclamation’s embankment dams and they are also discussed. And the effects of

certain developments, such as the Proctor density test procedure and the failure of Teton Dam,

are discussed in the paper.

RECLAMATION’S DESIGN AND CONSTRUCTION ORGANIZATIONS

In 1902, the new U.S. Reclamation Service (Service) was organized within and was drawn from

the U.S. Geological Survey’s (USGS) Division of Hydrography, Hydrographic Branch, that had

studied western water resources for the previous 20+ years. Frederick H. Newell, Chief of

USGS’s Division of Hydrography, was selected to head the new Service under USGS Director

Charles D. Walcott and was titled Chief Engineer, and Arthur Powell Davis was Newell’s chief

assistant [3]. Based on the studies previously conducted by USGS, which had included studies of

streams, watersheds, irrigable lands, and potential dam and reservoir sites throughout the West,

six projects were approved for design and construction by the Secretary of the Interior in 1903. 

Out of 79 projects investigated, a total of 25 projects had been examined and authorized for

construction by the Secretary within the first five years, and 15 of those had been started by

private companies or by a group of cooperating farmers who requested the Service’s help. 

Period I (1902-1918)

At the beginning of Period I, each of the 16 western states (17 states after Texas was added in

1906) had at least one district under the direction of a “District Engineer”, who was responsible

for all Reclamation activities, including surveys, investigations, designs, and construction. For

each authorized project, a qualified (civil) engineer was selected as the “Resident Engineer” and

he was responsible for conducting site investigations and developing preliminary design plans on

the embankment dam judged appropriate for the site. On a larger project, the Resident Engineer

might have the help of an Assistant Engineer. Supervisory Service engineers, who functioned as

liaison representatives of the Chief Engineer on certain projects, and consulting engineers with

special skills, reviewed the preliminary plans and made project recommendations to the Secretary

of the Interior. Upon the Secretary’s approval, the Service was authorized to develop final plans

and specifications. The early embankment dams were constructed either by contract with private

contractors or by “force account” using Government forces. Both types of construction were

managed/supervised by Service engineers and inspectors. Most of the dam sites were fairly

remote, so construction included transportation of all necessary equipment and materials to the

dam site, as well as construction of the camps and facilities required to house the construction

workers. 
3

In 1903, a permanent western headquarters office was established in Denver, Colorado, to house

the engineers and assistants of the Hydrographic Branch who would facilitate the location and

construction of dams, in order to avoid overcrowding in the Washington, D. C. office. The

Reclamation Service became independent from the USGS in 1907, with Chief Engineer Newell

becoming the Service’s first Director and Davis becoming Chief Engineer. Newell reorganized

the 17 states into six divisions to enhance the Service’s administration of its large workload: the

Central, Idaho, Northern, Pacific, Southern, and Washington Divisions. The Division boundary

lines were determined by the ease of railroad travel and communication, with drainage boundaries

also being considered. Each of the six Divisions was headed by a Division Engineer. 

Reclamation’s early Project, District, and Division Engineers included such notables as: Ira W.

McConnell, Raymond F. Walter, Frank E. Weymouth, Joseph B. Lippincott, Hiram N. Savage,

David C. Henny, Ernest G. Hopson, Louis C. Hill, and Charles H. Swigart. Note that engineers

Weymouth, Lippincott, and Hill were all elevated to Honorary Member status in the American

Society of Civil Engineers (ASCE).

In 1913, the Service’s hierarchy was reorganized, creating a five-member Reclamation

Commission, which included: the Director of the Service, Chief Engineer, Chief Counsel,

Comptroller, and Supervisor of Irrigation. In December 1914, the Chief of Construction was

added as a member of the Reclamation Commission. Davis became Director of the Service in

December1914 after Secretary of the Interior Franklin K. Lane removed Newell as Director and

named him “Consulting Engineer.” Newell finally resigned from the Service in May 1915 and

became Chairman of the Civil Engineering Department at the University of Illinois. Also in May

1915, the Commission’s membership was reduced to three, consolidating the Director and Chief

Engineer positions with Davis as Director and Chief Engineer and retaining the Comptroller and

Chief Counsel positions (which also appears to have removed the Supervisor of Irrigation and the

Chief of Construction as members of the Commission). That same year, the direction of field

operations was centralized at the Denver Office under the Chief of Construction. With the

establishment of the Chief Engineer’s Office in Denver, Reclamation’s engineering design and

construction management functions were centralized in the Denver Office. In 1918, the Secretary

of the Interior followed Arthur P. Davis’ recommendations and the top level structure of the

Service was again reorganized, making the Comptroller and the Chief Counsel subordinate to the

Director and Chief Engineer.

Period II (1919-1933)

In May 1920, Director and Chief Engineer Davis changed his title to Director and appointed the

Chief of Construction in Denver, Frank E. Weymouth, to the Chief Engineer position. Arthur

Powell Davis served as President of ASCE in 1920. On June 18, 1923, the Service became the

Bureau of Reclamation headed by the Commissioner of Reclamation; Davis resigned from

Reclamation the following day. David W. Davis was named Reclamation’s Commissioner on July

1, 1923, quickly followed by Elwood Mead after Davis left office on April 2, 1924. Dr. Mead

served as Commissioner from 1924 until his death on January 26, 1936. Reclamation’s design

and construction organizations remained much the same for the next 20 years. During the 1920s
4

and 1930s, the status of the Chief Engineer grew as Reclamation’s authority was consolidated in

the office of the Chief Engineer headquartered in Denver. Reclamation’s various laboratories first

got started in 1930 with the hydraulic model testing performed in the laboratory of the Colorado

Agricultural Experiment Station in Fort Collins, Colorado. The Concrete Laboratory and the

Earth Materials Laboratory were also begun in the early 1930s in the U.S. Customs House in

Denver.

Period III (1934-1944)

In 1942 and 1943, Secretary of the Interior Harold Ickes reorganized Reclamation in accordance

with a plan designed to: 1) decentralize the authority for work execution along regional lines, 

2) limit the authority of the Chief Engineer and his staff to project design and construction, and 3)

establish a “functional type” of organization with the Commissioner’s authority going straight to

the Regional Directors. The reorganization provided for:

Four major branches in the Denver Office: Design and Construction under the Chief

Engineer, Project Investigations, Operation and Maintenance, and Fiscal and

Administrative Management. The Chief Engineer remained Reclamation’s ultimate

authority in the technical execution of construction projects, even though responsibility

over construction in the field was now divided between the Regional Directors and the

Chief Engineer.

Six Regional Offices, later expanded to seven, concentrated on planning and development

activities, and supervised the operation and maintenance of completed project facilities. 

The seven Regional Offices were located at Boise ID, Sacramento CA, Boulder City NV,

Salt Lake City UT, Amarillo TX, Denver CO, and Billings MT. The Regional Directors

reported directly to the Commissioner’s Office.

Period IV (1945-1975)

In 1945, the Commissioner won support for his position that “the responsibility for the technical

aspects of design and construction work should remain in the Chief Engineer, and therefore,

authority for this work should also be vested in the Chief Engineer.” This created problems for

the Construction Engineers because they had two bosses: the Regional Director and the Chief

Engineer. Reclamation’s Denver Office included some 2,000 employees by 1948 that were

scattered around the Denver metropolitan area. Reclamation’s new Denver headquarters was

established in 1950 as the Engineering and Research Center at the Denver Federal Center in

Lakewood, located 10 miles west of downtown Denver. In 1953, during the Eisenhower

Administration, the Chief Engineer’s authority was upgraded and the title was changed to

Assistant Commissioner and Chief Engineer. This title continued to be changed, becoming

Director, Office of Design and Construction in 1963, Director, Office of Design and

Construction/Chief Engineer in 1970, and Director, Office of Design and Construction in 1972.
5

Period V (1976-2002)

Reclamation’s Teton Dam failed on June 5, 1976, killing 11 people and causing about 

$400 million in property damage. This failure had a profound effect on the Bureau of

Reclamation. Two official panels of technical experts reviewed the probable causes of the dam’s

failure and released their reports in December 1976, April 1977, and January 1980. Significant 

recommendations by these two panels involved several areas of concern. These included: the

need to establish independent dam design and construction review boards, greater documentation

of design decisions, closer project supervision and oversight by design personnel, and more

intensive construction and post-construction monitoring of the structures. A team was named by

then Commissioner R. Keith Higginson in 1977 to review Reclamation’s dam design and

construction procedures, which resulted in a November 1977 reorganization that reaffirmed many

of the 1943 reorganization’s objectives to more clearly define the respective functions of the

Denver and Washington Offices and to streamline the lines of authority and accountability. 

Reclamation’s staff for technical review and support was established and added to the Denver

Office. Since the failure of Teton Dam, and with the decrease in the authorization of new

projects, the majority of the embankment dam design and construction work has involved dam

safety evaluations and modifications of existing dams and appurtenant structures.

The title Director, Office of Design and Construction was changed to Assistant Commissioner for

Engineering and Research in 1978. In 1979, the Bureau of Reclamation’s name was briefly

changed to the Water and Power Resources Service, which lasted until 1981 when the name was

changed back to the Bureau of Reclamation. The Lower Missouri Region was absorbed into the

Upper Missouri/Great Plains Region in 1985. The Southwest Region was abolished in 1988,

splitting its area between the Upper Colorado Region and the Great Plains Region. Reclamation

now has five regions: Pacific Northwest in Boise, Mid-Pacific in Sacramento, Lower Colorado in

Boulder City, Upper Colorado in Salt Lake City, and Great Plains in Billings. In 1994, the

Denver Office was reorganized, and the title Assistant Commissioner for Engineering and

Research was changed to Director, Technical Service Center (TSC) under the Director of the

Reclamation Service Center, with the latter position recently abolished. The 1994 reorganization

increased the relative authority and power of the Regions and their local project and area offices,

and reduced that of the TSC engineering organization. 

The majority of the embankment dam design work, now mostly dam safety modifications

determined necessary on existing dams, is still performed by the civil/geotechnical engineers in the

TSC. The majority of the embankment dam modification construction work is done by civil

engineers in the Regions and their Project and Area Offices. There are still Construction

Engineers in the TSC who perform the construction management work and/or function as liaisons

and provide oversight on the construction work managed by the Regions and the Project and Area

Offices.
6

Modern Embankment Dam Design and Construction

As different cradles of civilization evolved all over the world, irrigation works and dams were 

basic components of their development. The earliest known design and construction of an

embankment dam occurred around 2900 B.C. with the construction of Sadd el-Kafara Dam in

Egypt. The early history of dams in the world includes many other countries as well, such as

India, China, and Iraq. In North America, the Hohokam Indians built diversion works and canals

along the Salt and Gila Rivers in southern Arizona as early as about 300 B.C. And in the FourCorners area (Colorado, Utah, Arizona, and New Mexico), the Anasazi and Pueblo Indians

constructed mud-wattle dams across streams that diverted infrequent runoff into ditches and

storage reservoirs throughout the area in order to support their agricultural civilization, according

to a recent study by Wright Water Engineers, Inc. of Denver, Colorado. According to Dams and

Public Safety [4] by Robert B. Jansen (Reclamation’s Director, Office of Design and Construction

and Assistant Commissioner for Engineering and Research, 1977-1979), the first dam built in

North America by European-Americans was built in 1623 on the Piscataqua River to operate a

sawmill at South Windham, Maine. The first embankment dam was called Mill Pond Dam and

was built in 1677 at Newington, Connecticut. In the far West, in early California, Old Mission

Dam was built on the San Diego River in about 1770 by the Jesuits to provide water for the

mission. It was composed of mortared rubble masonry and was about 5 feet high. 

Starting about 1850, gold miners in California built rock-filled log-crib dams faced with wood

planking that ranged up to about 125 feet in height to store water for hydraulic mining, but there

were numerous failures. It should be noted that many of the early dams constructed in California

during the latter half of the 19th century supplied water for mining purposes. One of the earliest

notable non-mining dams in the West was San Andreas Dam, constructed on San Mateo Creek

near San Francisco, California in 1870 to supply water for the city. This dam is notable because it

was unknowingly built across the San Andreas fault zone. This earthfill dam was about 

105 feet in height and was built using the 19th-century puddled-core technique, where the

upstream and downstream shells consisted of rolled clay and the narrow core was made by

manually tamping wet clay. The dam’s upstream slope was 3.5:1 (horizontal:vertical, H:V) and

the downstream slope was 3:1. The embankment included a cutoff trench excavated down

through the alluvium and colluvium (30 to 40 feet thick) that was backfilled with a clay puddle

core about 20 feet wide that was extended upward to form the central portion of the dam. The

dam was subsequently raised about 12 feet in 1875 and another 6 feet in 1928. The great San

Francisco earthquake of 1906 caused a horizontal strike-slip offset of about 6 to 8 feet in the left

abutment, but the dam embankment was not damaged. 

Across San Francisco Bay, the highest embankment dam built in the United States during the 19th-

century was Chabot (Lower San Leandro) Dam, which was constructed in 1875 above San

Leandro (near Oakland) on San Leandro Creek with a height of 115 feet above the streambed. Its

reservoir stored residential water for the East Bay communities. It was constructed as a centralcore earthfill dam, with the earthfill dumped from wagons, sprinkled, and compacted by the

wagon wheels and by a herd of horses moved back and forth across the fill. The dam’s cross-
7

section included a central foundation (cutoff) trench excavated down through foundation soils to

30 feet below the streambed. In the bottom of the cutoff trench, three parallel concrete cutoff

walls were constructed 3 feet thick and 5 feet high, with about half the height (21⁄2 feet) anchored

into the foundation and half protruding up into the fill. The core zone was about 90 feet

wide/thick at its bottom in the foundation trench. The embankment’s upstream slope was 3:1 and

the downstream slope was 2.5:1. A buttressing zone of earth and rock material was sluiced onto

the downstream slope, giving the embankment a total volume of about 543,000 yd3. In 1890, the

dam was enlarged by sluicing earthfill onto the downstream slope. Subsequent raising and

buttressing of the dam embankment has increased the height to 154 feet. A good source of

information on the evolution of dam design and construction, including embankment dams, is

Development of Dam Engineering in the United States [5], which includes information on six of

Reclamation’s embankment dams. Such was the state-of-the-art in embankment dam design and

construction at Reclamation’s birth. 

The design of modern earthfill and rockfill embankment dams is far more complex today than was

the case just 100 years ago. There are now many college courses, books, collections of

professional papers, professional groups, computer programs, etc. related to the design of modern

embankment dams. Most of the major unknowns and uncertainties involved with the design of

embankment dams 100 years ago have been removed by the evolution of engineering experience,

research, knowledge, and education. Reclamation has played a central role in that engineering

evolution through its pioneering embankment designs, analyses, and soil behavior work on

developing new laboratory tests and procedures for soils, development and publication of

geotechnical and embankment dam engineering manuals and books, and contributions to the

articles, transactions, and proceedings of engineering periodicals and professional civil engineering

organizations. Some of Reclamation’s learning and knowledge has come at a high price, as was

the case with the 1976 failure of Teton Dam in Idaho.

In addition to the books and professional papers that now exist on modern embankment dam

design and construction, several professional organizations regularly deal with and publish stateof-the-art papers on the design and construction of embankment dams and related topics. These

organizations include: ASCE, the recently renamed Unites States Society on Dams (USSD,

formerly the United States Committee on Large Dams, USCOLD), its worldwide parent

organization, the International Commission on Large Dams (ICOLD), the International Society

on Soil Mechanics and Geotechnical Engineering, and The Institution of Civil Engineers (in Great

Britain). 

To the lay-person, embankment dams may look like huge “piles of dirt” thrown across a valley or

canyon, and it can be hard to imagine how truly complex and amazing they actually are. Most

people can perceive how complex a large concrete dam, like Hoover Dam, must be with a height

of 726 feet. The highest embankment dam in the world is currently Rogun Dam on the Vakhsh

River in Tajikistan at a height of about 1,066 feet, and California’s Oroville Dam the highest in the

United States at about 770 feet. The largest embankment dam volume in the world is Tarbella

Dam on the Indus River in Pakistan with a volume of about 159,000,000 yd3, and Montana’s Fort
8

Peck Dam is the largest in the United States with a volume of about 

126,000,000 yd3. Many of these huge embankment dams are almost as amazing in their own way

as Hoover Dam. 

There are many more embankment dams (currently about 72 percent) than there are concrete

dams (currently about 28 percent) in the United States, out of the total of about 77,000 dams,

meeting minimum dam height and reservoir volume criteria. Among several reasons, one key

aspect of why embankment dams are so popular is that in general, a properly designed

embankment dam can be constructed at almost any damsite, as opposed to the more stringent site

limitations associated with concrete dams. A limited “picture” of the various elements that are

included in the design (and construction) of a modern embankment dam is presented below. A

more complete understanding can be obtained by reading publications such as Reclamation’s

Design Standards No. 13 - Embankment Dams [6] and the previously mentioned Design of Small

Dams.

Once the need for a new dam and reservoir and a variety of other factors such as funding

availability and environmental impacts have been resolved, several potential damsites are studied

and investigated in sufficient detail that a conceptual design report can be developed, which

includes recommendations as to the preferred damsite and the appropriate type of embankment

dam and related features. Once the damsite, the type of embankment dam, and related features

have been selected, more detailed studies, investigations, and analyses are conducted in order to

have the information necessary to start the final design work, which concludes with the

preparation of written specifications and drawings that are used as the basis for constructing the

new embankment dam. The various studies, investigations, and analyses included in these design

phases, which often overlap, generally include: 

1) a hydrologic study of the upstream drainage basin; 

2) a geologic study of the damsite and the reservoir basin, including a seismotectonic

study of the area; 

3) a field investigation of the foundation at the damsite and of the locally available

earthfill and rockfill materials and concrete aggregates; 

4) a laboratory program including testing and analysis of the soil, rockfill, and

bedrock materials obtained from the damsite and the borrow area(s); 

5) a conceptual design study, intended to develop and present various alternatives and

their costs, and to recommend the preferred alternatives for the embankment dam,

spillway, and outlet works features;

6) a final design based on the selected-alternative features, including the necessary

construction specifications and drawings;

7) during construction, embankment design details often change to accommodate the

changed conditions encountered; and

8) during First Filling of the reservoir and for the first few years thereafter, the

performance/behavior of the foundation and/or the dam embankment may indicate

the need for changes or modifications to the original design.
9

It should be noted that even a brief a description of how to design an embankment dam is beyond

the scope of this paper. The hydrologic study of the drainage basin above the damsite develops

information on the probable flood hydrology that is used to design the dam embankment and the

appurtenant spillway and outlet works features. If the dam and its appurtenant features can’t

accommodate the flood flows resulting from the various potential storm events, the reservoir can

overtop the dam embankment and cause it to fail. The geologic study develops the necessary

information on the geology of the damsite and the surrounding area, which often affects the type

of dam selected for design and construction. Unless the damsite’s geology is properly

understood, the response of the foundation to the loads imposed by a dam and reservoir may

cause malfunction, leading to serious maintenance or in some cases failure of the dam. This is

especially true in the event of an unexpected earthquake shaking a dam that is not designed to

withstand the severity of the loading imposed on the structure. The dam, spillway, and/or outlet

works can all fail because of a moderate to severe earthquake event. The field investigation and

laboratory testing of the dam foundation and the embankment borrow materials accumulate and

develop engineering design data on the foundation soils, bedrock, and borrow soil and rockfill

materials. These field and laboratory design data are critical and must be properly collected and

evaluated if dam failure is to be avoided. These design data form the basic information used in the

various analyses conducted during the design of an embankment dam, including standard concerns

about seepage, internal erosion/piping, settlement, static stability, seismic stability, etc. Design

information on sources of sand and aggregate materials for concrete is also developed.

After the design data have been properly developed, and the various design analyses have been

completed, the dam embankment’s alignment, cross-section, freeboard, foundation treatment(s),

material zoning, filters, drainage, camber, upstream and downstream slope protection, and

instrumentation (for monitoring performance) are then determined. Computers have greatly

enhanced the designer’s ability to perform extremely complex analyses, as well as to create 

3-dimensional models portraying the dam’s configuration to ensure that all of the dam

embankment’s components join together properly. The written specifications and drawings that

describe the details for construction of the dam are then developed. The spillway and the outlet

works are similarly designed, and must be compatible with the embankment dam’s design. 

Because of the potential public danger created by any dam and reservoir, dam design work

(including that performed by Reclamation) undergoes a very high level of review, including

review by boards of outside consultant experts where appropriate to ensure that our designs

achieve the high quality required. 

A well-known saying related to embankment dam design is that the design work is not complete

until the dam’s construction has been finished. And, this “construction period” should also

include the first few years of a dam’s performance under full reservoir loading. If the “First

Filling” of a large reservoir takes 10 to 20 years to complete, then the “construction period”

during which design changes and modification of the dam may be necessary could last well over

15 to 25 years. The design uncertainty during the dam’s construction involves the fact that the

geologic studies, the field investigation data, and the laboratory testing data actually involve a
10

relatively limited exposure and assessment of the dam’s entire foundation and all of the earthfill

materials used to construct the embankment. When the final foundation surface is completely

exposed, there can easily be overburden soils and bedrock that were not encountered by any of

the subsurface investigations conducted, depending on the damsite geology. And, when the

borrow materials are brought to the damsite for construction of the dam embankment, some of

the material may not be quite what was sampled and tested in the laboratory. The dam

construction process may also be affected by the construction contractor’s plans for constructing

the embankment. The contractor might propose a different approach than was anticipated by the

designer, such as the use of different construction equipment and the use of soil amendments to

improve one of the earthfill material’s characteristics (such as decreasing its permeability). Design

changes during construction are most often subject to the same review process as the initial

design.

The dam engineering work required in the development of the design data, the performance of

analyses, the preparation of the final design, and the construction of a modern embankment dam

and its appurtenant features generally involves a large number of related disciplines, including

engineering geology, seismology, hydrology, civil engineering, geotechnical engineering,

instrumentation engineering, structural engineering, hydraulic engineering, mechanical

engineering, electrical engineering, and construction engineering. Several of the above disciplines

are included as sub-disciplines or specialties within the civil engineering profession: geotechnical,

structural, hydraulic, instrumentation, and construction engineering. As you can see from the

“brief” description provided above, the planning, design, and construction of a modern

embankment dam is a complicated process that requires the civil engineers and other professionals

performing the work to have high levels of expertise and years of experience. The entire dam

design and construction process can take years (sometimes tens of years) to complete.

Improvements in the size, speed, and efficiency of construction equipment during the last 

100 years have played a major role in the evolution of embankment dam construction. The

construction of a modern embankment dam and its appurtenant structures involves a large variety

of construction equipment. A brief list of the common types of larger construction equipment

typically used in constructing an embankment dam includes: backhoe, dragline, crane, articulated

concrete pumper, pneumatic drill, front-end-loader, belly-dump truck, tandem end-dump truck,

all-terrain haul truck, belt conveyors, water truck, bulldozer, motor grader, self-elevating scraper,

excavators of all types, tamping-foot compactor (static and vibratory), sheepsfoot roller, and

smooth-drum roller (static and vibratory). Construction on a large dam or at a difficult damsite

may effectively utilize more efficient or unusual equipment, such as a belt conveyor system or a

short railroad for hauling the borrow material to the damsite. 

Reclamation’s History of Embankment Dam Design and Construction

The history of Reclamation’s century of embankment dam design and construction is separated

into the five periods already used in describing Reclamation’s design and construction

organizations. Over 240 reservoir-storage embankment dam structures have been designed and
11

constructed by Reclamation during the past century. Some of the information presented in the

following period sections on Reclamation’s embankment dam design and construction history

through 1958 is taken from Development of Earth Dam Design in the Bureau of Reclamation [7]

by F. C. Walker, then Head of the Earth Dams Section, Dams Branch, Division of Design. The

location map and map index of Reclamation’s embankment dams are shown in Figures 1 and 2

below and on the next page.

Figure 1
12

Figure 2
13

Period I (1902-1918)

As already mentioned, at Reclamation’s emergence in 1902, the USGS’s Division of

Hydrography, Hydrographic Branch had been studying water resources in the West for about 

20 years, developing data on potential reservoir and dam sites. The USGS had published reports

such as Reservoirs for Irrigation [8], authored by James D. Schuyler in 1897. When the U.S.

Reclamation Service was established and given its mission of developing western water resources,

Frederick H. Newell and his nucleus of engineers were transferred from the USGS’s

Hydrographic Branch to the Service and they quickly started work on the design of the six

projects that had been approved for design and construction by the Secretary of the Interior in

1903. Work on the additional dams and projects approved for design and construction during the

next few years commenced as quickly as was possible. 

What was the state-of-the-art in embankment dam design and construction in 1903? Only a few

books had been published in the United States that covered the design and construction of dams,

including embankment dams. The first such book was The Design and Construction of Masonry

Dams [9] written by Edward Wegmann (Member, ASCE) in 1888, followed in 1899 by his The

Design and Construction of Dams, Including Masonry, Earth, Rockfill, Timber and Steel

Structures [10]. The third important book on dams, Reservoirs for Irrigation, Water-Power, and

Domestic Water Supply [11], was written by James Dix Schuyler (Member, ASCE) in 1901, with

a second edition in 1909 [12], which included information on the Service’s Minidoka, Belle

Fourche, and Cold Springs Dams. The 1909 book included chapters on: Rock-fill Dams,

Hydraulic-fill Dams, Masonry Dams, Earthen Dams, Steel Dams, Reinforced Concrete Dams,

Natural Reservoirs, and Miscellaneous, and included a total of 381 photos, figures, and

illustrations. 

The publications of several engineering, mining, and construction organizations were the primary

source of information on which embankment dam designs worked or failed, and why. These

publications included: Engineering News and Engineering Record (both subsequently merged to

form Engineering News-Record), Mining and Scientific Press, Engineering and Mining Journal,

Transactions of the American Institute of Mining Engineers, and ASCE. Service engineers such

as Hiram N. Savage had already written articles on dams [13], published before the Service was

created. Within a relatively short period, more books were written about dams, an increasingly

important subject in the arid West. Articles about the new Service and its dams first appeared in

Engineering News in 1903 and then in other publications like Engineering Record, Engineering

and Construction, Irrigation Age, and Pacific Builder and Engineer shortly thereafter. Papers on

the Service’s dams began to appear in the Proceedings of ASCE in 1907 and of the American

Society for Testing Materials in 1908 (dealing with cement and concrete work).

The Service’s Chief Engineer and his initial staff of 15 (civil) engineers and related disciplines

reportedly had lots of previous practical experience. Although the Denver Office was established

in 1903 for the engineers and assistants from USGS, a Resident Engineer at each irrigation project

was assigned to supervise the development of all phases of the project, which included
14

investigations, design, and construction. The project plans were reviewed by a “project board”

consisting of the Resident, District, and Supervising Engineers. If warranted, one of

Reclamation’s technical experts or a consultant would assist on a complex or difficult project. 

The actual records from this early period are fairly limited. Once the reservoir storage site was

examined and appeared acceptable, it was used only if the observable geological conditions were

“unquestionably adequate in light of past experience.” Where explorations were made, they were

directed at locating a competent foundation, with little consideration given to the material

overlying the good foundation. Streamflow records were either short or nonexistent. Except for

critical items such as gates, cement, and reinforcing steel for concrete, materials for constructing

the dam, including sand and gravel for concrete, had to be locally available due to transportation

difficulties. 

Reclamation’s first approved project was the Truckee-Carson Project, later called the Newlands

Project that was located in California and Nevada. Reclamation’s first constructed dam was part

of that project. Truckee River Diversion Dam located on the Truckee River in Nevada, now

called Derby (Diversion) Dam, was constructed as a combination gated concrete structure and

earthfill wing embankment dam. Construction of the diversion dam and canal works began under

Specifications No. 1 in 1903 and was completed in June 1905. The dam was 1,331 feet long, had

a structural height of 31 feet and a hydraulic height of 15 feet, contained about 

37,000 yd3 of earthfill, and had a 3:1 upstream slope and a 1.5:1 downstream slope. The Project

Engineer responsible for design and construction was Leon H. Taylor. Reclamation’s first

completed embankment dam, whose primary purpose was to impound a water-storage reservoir,

was Minidoka Dam located on the Snake River in Idaho (see Figure 3 on next page). Its

construction began in 1904 and was completed in 1906 (see figure 4 on page after next page). It

was a zoned earthfill and rockfill embankment 80 feet high that contained 257,000 yd3 of earth

and gravel fill and rockfill materials, had a crest length of 664 feet, and impounded 210,000 acrefeet of water. Minidoka Dam was designed by John H. Quinton (Member, ASCE) and was

constructed under the supervision of Construction Engineer F. C. Horn.

Rolled (compacted) earthfill was generally preferred by Reclamation for embankment dam

construction because of the difficulty in handling rockfill material, but hydraulic or semi-hydraulic

fill construction was used in several instances. Foundation treatment varied substantially. Some

of the dam foundations were excavated to bedrock, some had cutoff trenches excavated to

bedrock, and some had multiple trenches. Some cutoff trenches included a concrete cutoff wall

constructed into the foundation bedrock that extended up into the cutoff trench backfill. Some

trenches were for drainage and some provided additional cutoffs. Two dams had pile cutoffs: one

made of wood and one made of steel sheet piling; neither of them was considered very effective. 

Almost all of these embankment dams had one to three feet of riprap on the upstream slope.

Most of the embankment dams constructed by Reclamation during Period I were relatively small

structures (by today’s standards) that still took quite some time to build with the methods

available at the time (Belle Fourche Dam took over 5 years). The designs for these dams, which
15

Figure 3 - Minidoka Dam Plan and Section

depended on the nature of the locally available earthfill materials (and still do today), were based

on a relatively limited knowledge of geotechnical engineering and the other disciplines mentioned

earlier. The design standards of that time were limited: 1) an adequate foundation to support the

dam, 2) an impervious core or upstream facing, and 3) a spillway capable of passing flood flows

without damage to the embankment. Data on the hydrology of the drainage basins were very

limited. The geology of the damsites may have been studied and documented, but its affect on the

dams to be designed and constructed was probably poorly understood. The field investigation

performed at the damsite and on the earthfill borrow areas was generally limited to test pits and

borings of shallow depth. 

Any laboratory testing of the anticipated earthfill materials was extremely limited by today’s

standards since most of the tests now performed on earthfill and rockfill materials were developed

during and after the 1920s. Grain size analysis was probably performed on the soils, but only of

the sand, gravel, and cobble size materials, and information on the amount of clay and silt

materials was not possible until later. Darcy’s Law about the rate of water-flow through a soil (its

permeability) was promulgated in 1856, and it dictates how and where different types earth

materials (clay, silt, sand, gravel, cobbles, and rockfill) can be used in an embankment dam, which

is still very relevant today. Early scientists, physicists, and engineers like Charles A.
16

Figure 4 - Minidoka Dam Construction

Coulomb (1773), Alexandre Collin (1846), and W. J. M Rankine (1857) developed theories about

earth pressure on retaining walls and tests of the shear strength of soil materials, but there were

no standardized shear-strength tests performed on soil materials or analysis of slope stability as

are an integral part of embankment dam design today. The Atterberg limits tests still used today

to help characterize clayey materials were developed by A. Atterberg of Germany in 1911. In

1916, K. E. Pettersson and S. Hultin developed a slope stability analysis method to analyze the

failure of a quay wall in Goteborg, Sweden, but it does not appear to have been introduced to

engineers in the United States until several years later. And settlement/ consolidation behavior of

soil materials was not tested, although settlement benchmarks were first installed along the edges

of the embankment crest at Belle Fourche Dam in 1911. Thus, the ability to develop the

necessary data and to analyze an earthfill structure like an embankment dam during Period I was

very limited by today’s standards. 

The various types of construction equipment that existed during Period I played a large role in
17

defining the size and height limitations placed on these early embankment dams. Excavation of

foundation overburden soils (alluvium and colluvium) or borrow materials was performed by pick

and shovel, horse-drawn (Fresno) scraper, dragline, and/or steam shovel. The borrow soil

materials were excavated by hydraulic monitor or dredge for use in hydraulic-fill embankment

dams, and by dragline and/or steam shovel for the other types of embankment dams . For

relatively short distances, transportation of borrow materials to the damsite was accomplished by

hydraulic pipelines or flumes in the case of hydraulic-fill dams and by horse-drawn wagons and/or

scrapers for the other types of embankment dams. For longer distances, borrow materials were

transported by railroads using trains of side-dump cars pulled by small “Dinkey” steam

locomotives. After the earthfill material was brought to the embankment and dumped, it was

spread out in relatively thin (i.e., 6-inch-thick) layers using horse-drawn drags and/or graders. 

Water may or may not have been added to the layers of uncompacted earthfill before compaction. 

Each layer of earthfill was then compacted by team and wagon travel, steel-drum rollers, 

concrete (cylinder) rollers, and/or steam-powered engines (“traction engines” were used at Belle

Fourche Dam). The use of the sheepsfoot roller for earthfill compaction was reportedly

developed around 1905, but they were not used on Reclamation’s dams for a while yet. Rockfill

material was either placed without compaction or was sluiced with hydraulic monitors. Period I

construction by Reclamation was accomplished either by government forces or by contract with a

construction company. 

During this early period of embankment dam design and construction, the height of dam and the

foundation geology had little affect on the design of the embankment dam section. However, the

type of earthfill materials available for embankment construction had a noticeable influence. 

Hence, depending on the nature of the earthfill materials available in the borrow area(s), the dam

embankment section was either: 1) an upstream impervious zone supported by a downstream

rockfill zone, 2) an upstream impervious zone supported by a downstream gravel zone, or 3) a

modified homogeneous section, which included design features that modified the homogeneous

performance.

Upstream Impervious Zone Supported by Downstream Rockfill Zone

Period I embankment dams utilizing this type of cross-section included: Avalon, Clear Lake,

Minidoka, and McMillan Dams and Elephant Butte Dike. Avalon and McMillan Dams, both on

the Pecos River near Carlsbad, New Mexico, were actually the second or third reconstructions of

earlier dams that had failed by overtopping during floods that breached both dams. Neither dam

included a transition/filter zone between the earthfill and rockfill zones, which was added to later

dams of this type. Avalon Dam also had a part sheet-pile, part concrete core/cutoff wall the full

height of the dam. The upstream slope of these dams was typically 3:1 that was often steepened

to 2:1 above the full reservoir level, and the downstream slope was typically 1.5:1. The relatively

high cost of using rockfill material with the equipment then available was the reason that few of

this type of embankment dam were constructed by Reclamation. The failure of several nonReclamation dams of this type during this period probably contributed to the decision to stop

building this type of dam.
18

Upstream Impervious Zone Supported by Downstream Gravel Zone

Period I embankment dams utilizing this type of cross-section included: Cold Springs, Lahontan,

Keechelus, and Minitare Dams and Pathfinder Dike. The upstream slope of these dams was

typically 3:1 and the downstream slope was typically 2:1, except for Minitare Dam. Minitare

Dam had a 2.5:1 upstream slope to the full reservoir level, a 2:1 slope above that level, and a

2.5:1 downstream slope. Pathfinder Dike also had a concrete cutoff wall that extended above the

reservoir level. The earthfill zone became thicker during the period, probably because gravel

material was more difficult to use with the construction equipment then available, and because of

the greater relative abundance of earthfill material. Although the mechanics of internal erosion

(piping) of earthfill materials was not yet understood, dam designers did understand the nature of

the problems potentially caused by seepage from the reservoir, as indicated by their efforts to

control that seepage with defensive measures like cutoff trenches and walls. The designers also

made the embankment’s upstream impervious earthfill zones thicker than twice the hydraulic

water-pressure head from the reservoir. Cold Springs Dam, constructed between 1907 and 1908,

had a total of four zones in which the gravel content increased from 50 percent in the upstream

zone to 67 percent, then 80 percent, and finally 100 percent in the downstream zone.

Modified Homogeneous Section

The remaining Period I embankment dams were of the “modified” homogeneous cross-section

type, and they included: Belle Fourche, Deer Flat, Strawberry, and Sherburne Lake Dams. 

Except for Belle Fourche Dam, the other dams had 3:1 upstream slopes and 2:1 downstream

slopes. Sherburne Lake Dam includes a vertical screened-gravel drain near the center of the

embankment section, with this type of design detail being many years ahead of its time. Belle

Fourche Dam had a “bold” (less conservative) embankment cross-section, probably due to its

large size. The lower upstream slope is 5:1 to a berm, 2:1 above the berm to the full reservoir

pool level, and 1.5:1 above that; and the upper downstream slope is 1.655:1 to a berm and drain

gutter, and 2:1 below that level. At the time it was built, Belle Fourche Dam was reportedly the

largest rolled earthfill dam constructed in the world; it is discussed in greater detail below. 

Strawberry Dam also had a reinforced concrete core wall that extended above the reservoir level.

Belle Fourche Dam

Belle Fourche Dam (locally called Orman Dam) is located on Owl Creek about 10 miles northeast

of Belle Fourche, South Dakota, and was the most notable embankment dam constructed by

Reclamation during Period I. The dam was constructed 115 feet high above its streambed with a

crest length of 6,262 feet, an earthfill volume of 1,783,000 yd3, impounded a 192,000 acre-foot

off-stream reservoir and a water-surface area of about 8,000 acres, and was fed by a 6-mile-long

canal that conveyed a maximum of 1,600 ft3/s of water diverted by a diversion dam on the Belle

Fourche River. Information on the embankment’s as-built slopes is given above. The original

upper slopes shown on the 1905 Belle Fourche Dam design drawings were 1:1 instead of 1.5:1

upstream and 1.75:1 instead of 1.655:1 downstream. The decision was made during construction
19

to flatten the upper upstream slope and flatten the upper downstream slope, moving the crest

downstream (see Figure 5 below). 

Figure 5 - Belle Fourche Dam Section

The greater steepness of the upstream slope, compared to the other embankments designed and

built by the Service during Period I was an important difference. Construction under contract No.

73 awarded to Orman & Crook of Pueblo, Colorado, began in November 1905, but work was

suspended in early 1908 when Orman & Crook went into bankruptcy. Construction resumed in

April 1908 under a new contract with the National Surety Company of New York, who was the

“bondsman” for Orman & Crook. The National Surety Company subcontracted with several

private companies to perform the construction and the dam was completed on June 30, 1911. 

The total cost, including engineering, construction, cement, and general expenses, was about

$1,299,000. An article on Belle Fourche Dam by Project Engineer Raymond F. Walter was

published in Engineering Record in March 1906 [14]. A second article on the dam by Resident

Engineer O. T. (Oliver) Reedy (Associate Member, ASCE) was published in Engineering Record

in April 1910 [15], describing the early plans for the project and the construction to date (early

1910) on the dam and appurtenant structures. Some of the more unique or informative details

related to Belle Fourche Dam’s design and construction are discussed below. 

In April 1904, a board consisting of Arthur P. Davis, John H. Quinton (consulting engineer from

Los Angeles), and Charles H. Fitch (Supervising Engineer) examined the Belle Fourche Project

and ordered detailed surveys of the irrigable areas, potential damsites, and canal alignments. 

Three dam sites were located and the final damsite was selected in May 1905. The dam

foundation had been “thoroughly prospected” by both open test wells and by earth auger borings

located every 200 feet along the dam’s alignment. The embankment was founded on a “heavy

compact clay,” locally known as “gumbo”, which overlies a soft slatey shale located 20 to 40 feet

below the surface. There were occasional pockets of gravel encountered in the overburden layer. 

The dam embankment was constructed using the locally available clay obtained from borrow pits

located upstream and at both ends of the dam. An expert “Engineer of Soils”, Thomas H. Means

came and tested the proposed earthfill material. Small scale experiments determined that this

material needed an additional 7 percent water, by weight, for compaction to achieve the maximum

density of the earthfill. Belle Fourche Dam was designed under the direction of Project Engineer
20

Raymond F. Walter, with the resulting plans approved by a board of engineers consisting of John

H. Quinton, C. E. Wells, Charles H. Fitch, and Raymond F. Walter, resulting in a July 5, 1905,

letter in which they approved the plans and specifications, recommending “that the drawings be

reduced to standard size and the specifications printed in Washington and that the work be

advertised as soon as possible.” The 1905-era Specifications No. 56 contained a total of 37 pages

and 12 drawings used to show the dam embankment, appurtenant structures, and canals. The

specifications sections included topics such as: Engineer, Changes, Sanitation, Use of liquor,

Embankment construction, and Measurements. During construction, several design details related

to the dam’s upper slopes and the appurtenant structures had to be revised. Resident Engineers

Patch and Reedy were in daily to weekly contact with Project Engineer Walter during the entire

period of dam construction. Visitors (mostly engineers) from as far away as South Africa and

Sweden visited the dam during construction [16]. 

Figure 6 - Belle Fourche Dam - Cutoff Trench Construction

In August 1910, engineers from the U.S. Army Corps of Engineers (Corps) visited the dam for a

few hours and subsequently informed Reclamation that they considered the dam’s slopes,

particularly the downstream slope to be excessively steep. Reclamation’s engineers, including

Project Engineer Walter and Chief Engineer A.P. Davis, developed the response to the Corps and

provided a list of some 20 recently constructed embankment dams built with slopes steeper than

at Belle Fourche Dam. They knew that the location (height) of the phreatic surface in the dam

embankment would affect the slope stability of the embankment, so they decided to install some

2-inch-diameter vertical pipes to function as observation wells for monitoring the “plane of

saturation.” More details on these pipe observation wells are provided below. 

The cutoff trench was excavated by horse-drawn “wheel scrapers” and a locomotive crane, using
21

a 1⁄2-yd3 clamshell bucket, after which the trench was backfilled with compacted “select material”

(see Figure 6 on previous page). The earthfill material in the borrow area(s) was excavated by 

70-ton and 75-ton steam shovels with a 21⁄2-yd3 bucket/dipper and was dumped into the 4-yd3

Western side-dump cars (see Figure 7 below). The trains of 10 to 13 side-dump cars (a total of

about 60 side-dump cars were used) were pulled by 18-ton Dinkey locomotives that hauled the

trains about 3⁄4-mile to the embankment, up a maximum grade of about 4 percent onto the

embankment surface. The 36-inch gage train tracks and wooden ties were moved every third

layer as the embankment rose in height. Three-horse-team 11⁄4-yd3 dump wagons, filled by

Western graders pulled by traction engines, were also used to haul earthfill from some of the

upstream borrow pits.

Figure 7 - Belle Fourche Dam

Steam Shovel, Dinkey Locomotive, and Train of Side-Dump Cars in Borrow Pit

Four-horse-team Fresno scrapers were used to move the dumped earthfill a maximum distance of

50 feet away from the tracks, and ordinary four-horse-team road graders ran over the material

deposited by the scrapers to spread and level the layer (see Figure 8 on next page). The layer of

earthfill was thoroughly wetted, if necessary, using a 2-inch hose to apply water pumped up from

wells or small reservoirs. If the earthfill was compacted immediately 
22

Figure 8 - Belle Fourche Dam - Embankment Fill Construction

after being placed on the fill, little if any water needed to be applied. The specifications required

that the earthfill material be placed and rolled in 6-inch layers using steam rollers weighing not

less than “200 pounds per linear inch of roller rim.” According to O.T. Reedy’s article, one of the

rollers used was a 12-ton roller with a 4-foot rolling base. According to the Belle Fourche

Project History [17], an “8-ton asphalt dirt roller with smooth wheels” was also used, but it often

became stuck on the slick surface of the embankment. However, most of the compaction was

accomplished by four 32-horsepower 18-ton and 21-ton traction (steam) engines, with the rear

wheels having been widened to create a 6-foot-wide “rolling base.” The traction engines

accomplished the compaction more quickly due to their greater power (see Figure 9 on next

page). 

A somewhat unique feature of the construction of Belle Fourche Dam was a gap through the

embankment in the vicinity of station 42+00 (note that the distance between stations 0+00 and

1+00 equals 100 feet) that was left open to pass Owl Creek flows through the damsite from the

start of construction until it was quickly closed in 1909. The “Owl Creek Gap” (Gap) had side

slopes a little steeper than 1.5:1. Flooding on Owl Creek occurred several times during

construction, with a maximum flow of about 5,500 ft3/s moving through the Gap. Earthfill

cofferdams were constructed at the upstream and downstream ends of the Gap. Three cutoff

trenches were excavated across the Gap that were backfilled with select earthfill material. A

drainage system consisting of 4-inch tile pipes enclosed in screened gravel was constructed in the

Gap’s bottom downstream of the lower cutoff trench to collect and convey any foundation

seepage to discharge into Owl Creek downstream of the dam. The Gap was closed using earthfill

hauled to the dam by wagon and by train, which involved dumping the earthfill off a Howe truss

bridge, and spreading and compacting the earthfill layers as rapidly as possible. The Howe truss 
23

Figure 9 - Belle Fourche Dam - Traction Engine Hauling Dinkey Locomotive to Damsite

bridge consisted of one 100-foot center span and two 60-foot side spans built across the Gap. 

The Gap fill was joined to the two existing embankments by excavating the slopes of the Gap until

firm material was reached. Due to the confined area, the bottom layers of earthfill were

compacted by hand tampers that could exert a pressure of 1 lb/in2, by a wooden tamper weighing

about 200 pounds operated by the locomotive crane, by the small 12-ton roller, and then by the

wheels of a traction engine.

Another unique feature of the dam’s design was the upstream slope protection. The nearest rock

quarry was located 32 miles away and the sandstone’s quality was considered poor, together

causing its use to be rejected. The selected upstream slope protection consisted of 8-inch-thick

concrete blocks/slabs that measured 5 feet by 61⁄2 feet, and weighed about 3,000 pounds each. A

concrete footing wall was constructed at the bottom of the 2:1 slope and the bottom course of

blocks rested against this wall. Along the center portion of the embankment, the concrete footing

wall was buttressed by 10-inch-diameter 16-foot-long timber piles driven into the earthfill on 3-

foot centers. The concrete blocks were placed on a 24-inch-thick bed of gravel using stiff-leg 3-

ton-capacity traveling derricks with 25-foot masts and 50-foot booms operated by 20-horsepower

hoisting engines. The blocks were moved into place with the derrick and were then levered and
24

hammered into place. Figure 10 below shows the nearly-completed dam embankment from the

right abutment.

Figure 10 - Belle Fourche Dam - Embankment from Right Abutment

The upstream slope protection at Belle Fourche Dam suffered some degree of damage by wave

action almost every year due to the common, sustained high winds in the area and the 8-mile fetch

(length) along the Owl Creek arm of the reservoir. A 4-foot-thick layer of grouted riprap was

suggested in 1943 by Chief Design Engineer John L. (Jack) Savage (Honorary Member, ASCE),

but World War II caused the work to be deferred. A 4-foot-thick layer of dumped rock riprap

was constructed in 1976-1977, but the wave-erosion/beaching problem still persists in some areas

on the upstream slope.

The downstream slope was finished by placing a 12-inch-thick layer of rich loam-soil dressing

which was then “seeded with a mixture of grasses recommended by the Department of

Agriculture.” Concrete gutters were also placed on berms located 30 feet apart vertically, with

down-slope gutters every 1,000 feet, to collect and remove runoff during heavy rainstorms.

The dam included two canal outlet works, each one well above the old Owl Creek channel, and a

waste weir (spillway) at the left (north) end of the embankment. Downstream of the weir

structure, the spillway channel was earth lined below which it was concrete lined. Ensign-type

balanced valves were installed on the canal outlet works in 1910 and 1911. Two 58-inch valves

were installed at the upstream end of the North Canal outlet works conduit and one 58-inch valve

was installed at the upstream end of the South Canal outlet works conduit.
25

During the summer of 1910, after the reservoir had reached a maximum elevation of about 

2930 feet, seepage began to surface downstream of the dam where the ground is at about

elevation 2910. Borings were driven to investigate the cause and source of the seepage, which

indicated a strata of disintegrated shale and gravel about 10 feet below the surface. The engineers

had known about this layer of gravel, but thought is was 30 to 40 feet below the ground surface. 

Supervising Engineer David C. Henny of Portland, Oregon, had been brought in as a “consulting

engineer” during much of the work on the dam, and he was again consulted on the seepage

problem. A drainage system was advised, designed, and constructed along the downstream toe of

the embankment in November and December 1910. This drainage system consisted of a trench

excavated about 3 feet wide and up to 17 feet deep between stations 26+00 and 41+00 (1,500

feet), with 14-inch-diameter “telephone pole auger” wells drilled in the bottom of the trench that

were backfilled with coarse screened gravel, covered by fine screened gravel and then pit-run

gravel. A 12-inch-diameter vitrified clay tile pipe was placed with open joints and surrounded by

coarse screened gravel (1-inch to 2-inch) and by fine screened gravel (1⁄4-inch to 1-inch)

surrounding the coarse gravel in the bottom of the trench, which was then covered with

unscreened gravel and regular backfill. Manholes were constructed at several locations along the

toe drain- using 2-foot-diameter vitrified clay pipe. The outflow from the drainage system

reached a maximum of 45 to 50+ gal/min, which varied with the reservoir water surface elevation. 

The flow from this drainage system has been monitored ever since, and constitutes the longest

continuous monitoring performed on one of Reclamation’s embankment dams. 

In late 1911, a series of 2-inch-diameter open-end pipe (observation) “wells” were installed in the

embankment in the vicinity of stations 37+00 and 38+00 to determine the “plane of saturation”

(phreatic surface) and to obtain data on its movements with reservoir fluctuations. A wash-boring

apparatus was used to drill the holes into which the pipes were installed; 34 wells were

constructed, ranging in depth from 10 to 90 feet. These were the first “instruments” installed in a

Reclamation embankment dam for the purpose of monitoring the porewater pressures in the dam

and/or foundation. A few of these observation wells are still monitored, making them the longest

continuously monitored instruments of that type. Their rate of response to reservoir fluctuation is

very slow (about a 2-year lag time) due to the relatively large diameter of the 2-inch pipes and the

very low flow rate (permeability) of the seepage percolating through the gumbo-clay

embankment. Also in 1911, a set of iron benchmarks was installed every 300 feet along the

embankment crest to monitor its settlement, also the first of that type of instrumentation installed

on a Reclamation dam. Belle Fourche Dam was quickly turned into the most instrumented

embankment dam built by Reclamation between 1902 and 1911.

The 90-year-long performance of Belle Fourche Dam has been quite an interesting story. The

concrete paving blocks protecting the upstream slope have suffered storm damage fairly

frequently, which is why that type of slope protection was not used after the construction of

Minitare Dam in 1915. In 1928, after 17 years of acceptable embankment performance, parallel

cracks several hundred feet long occurred on the embankment crest between stations 27+00 and

31+00, and they occurred close to the upstream slope. This lead to an investigation and

exploration shafts; the cracks were up to 3 inches wide and up to 12 feet deep. The resulting
26

judgement was that drying out of the embankment was the cause. Other cracks had also been

reported in the vicinity of station 39+00 to 46+00. Then on August 2, 1931, after a fairly rapid

drought-caused reservoir drawdown of 27 feet in 60 days, part of the upstream slope failed,

resulting in a slump about 610 feet long between stations 40+50 and 46+60. The slide mass

averaged a thickness of 9 to 10 feet and extended from about elevation 2962 down to the base of

the 2:1 slope at elevation 2920. Several factors contributed to this slide, but the steepness of the

upstream slope, the (low) shear strength of the as-constructed “gumbo” clay embankment

material, the low permeability of the “gumbo” clay material, and the rapid reservoir drawdown

were the primary factors that caused the failure. 

The slope failure was quickly examined by Reclamation’s engineers, including Chief Design

Engineer Savage on August 12th. Plans for reconstruction of the upstream slope were agreed

upon. On August 24th, a 3⁄4-yd3 dragline began building an access ramp into the slide and began to

remove the concrete blocks. A total of 20,320 yd3 of the slumped embankment material and

gravel bedding was excavated by a larger dragline with a 50-foot boom and a 13⁄4-yd3

 bucket,

making sure to dig at least 1 to 2 feet below the “lowest slip plane,” and placing the material in

stockpiles to one side for reuse. The embankment was then rebuilt by several pieces of

equipment. The larger dragline picked up a half-bucket of gravel, then filled the bucket with

stockpiled embankment material, and dumped the material into the excavation where it was

hauled and spread in 6-inch layers by Caterpillar tractors pulling Fresno scrapers. These layers

were then compacted by rollers pulled the Caterpillar tractors. The initial attempts to use

concrete rollers for compaction encountered difficulty when the roughness of the roller prevented

it from being properly cleaned. An “iron mule” loaded with one yard of gravel was tried, but it

was too slow. They then tried an old printing press roller, for which they had to make a pulling

device, and filled the roller with concrete. This smooth roller allowed the use of cleaning scrapers

and it worked well pulled by a “Fifteen” (horsepower) Caterpillar tractor. A total of eight

Caterpillar tractors were used, ranging in size from fifteen to forty horsepower. The most

effective “dirt mover” was a “Thirty” Caterpillar tractor pulling a 11⁄2-yd3 Fresno scraper. Up to

three working shifts were used due to the approach of winter. Once the embankment was rebuilt,

the gravel bedding was rebuilt and the concrete paving blocks were placed back on the upstream

slope. 

After the completion of this reconstruction, Reclamation proceeded during the remainder of the

1930s to drill, sample, install piezometers (for monitoring water pressure) in the dam embankment

and foundation, and then conduct a laboratory investigation of the Belle Fourche Dam

embankment material in one of the most comprehensive laboratory investigations conducted up to

that time. That work was followed by a (then) state-of-the-art analysis of the upstream slope

stability. Finally, in 1939, a 25-foot-wide earthfill berm was constructed to improve the stability

by buttressing the upstream slope. The berm sloped at 3:1 and included a 

3-foot-thick layer of well-graded 1⁄4-inch to 3-inch gravel that was placed against the existing dam

embankment to provide drainage. The berm included earthfill material similar to the original

embankment material, but it was enclosed in gravel for drainage. The earthfill material was placed

in 6-inch lifts and was compacted by 12 passes of a tamping roller. The tamping rollers were to
27

be configured such that they had one ball foot or knob for each square foot, a knob end area

between 5 and 7 in2, produced a knob pressure of not less than 300 lb/in2, and were equipped with

roller cleaners. The berm was surfaced with 24 inches of riprap placed on 12-inches of gravel

bedding. Weep holes were also drilled on 5-foot centers through the concrete paving slabs for

drainage purposes. The embankment section shown in Figure 5 includes this upstream berm. 

The concrete paving slabs on the upstream slope continued to be damaged by wave action, and in

1976-1977, the upper portion of the upstream slope was rebuilt to provide 4 feet of riprap slope

protection on a 2.33:1 slope from the top of the 1939 berm (elevation 2950) to the embankment

crest (elevation 2990). Longitudinal cracks have continued to appear on the dam crest into the

1990s, and the rate of reservoir drawdown continues to be carefully controlled in order to prevent

further drawdown-induced slope instability. 

Belle Fourche Dam is a truly amazing and unique early embankment dam in Reclamation’s 

history. ASCE designated Belle Fourche Dam a National Historic Civil Engineering Landmark in

1988, and (somewhat surprisingly) it is Reclamation’s only embankment dam so honored. Many

of the design details and construction procedures developed and utilized at Belle Fourche Dam

starting 97 years ago are still used by Reclamation engineers today, especially some of the

innovative design and construction concepts. 

Period II (1919-1933)

Reclamation engineers had helped advance the state-of-the-art in embankment dam design and

construction during Period I. Reclamation’s reputation grew as the numbers of its successful

projects increased throughout the West. Reclamation received more and more publicity in the

articles and papers published in western newspapers, magazines, and professional journals to

which Reclamation’s engineers contributed their experience, innovations, and new design ideas. 

Reclamation’s engineering design groups had been centralized and were better organized in the

Denver Office, and they produced designs for new projects and dams at a high rate. Respected

civil engineers like J. L. Savage, who had started his career with Reclamation on the Minidoka

Project in 1903, had joined the new Denver Office staff as a Design Engineer in 1916 and was

subsequently promoted to Chief Design Engineer in February 1928. The Chief Engineers during

Period II were Arthur P. Davis (also serving as Director of the Service until 1923), Frank E.

Weymouth, and Raymond F. Walter.

The embankment dams designed and constructed during Period II were larger and the designs

were more varied. Consultants were used extensively during Period II, although the list of dams

constructed during this period is fairly small. Most of them were built with homogeneous

sections, had little foundation treatment of note, and generally had 3:1 upstream and 2:1

downstream slopes. Early in this period, the 40-foot-high Salmon Lake Dam was constructed

between 1919 and 1923 on Salmon Creek as part of the Okanogan Project in Washington state. 

It was Reclamation’s first embankment dam that utilized a central impervious (sandy loam) core

and a flattened downstream toe or “tail” with 5:1 and 10:1 slopes. It was also the first dam to be

constructed on a “questionable” foundation (sand and clay of unknown depth). The base of the
28

impervious core was widened, and in the bottom of the 8-foot-wide cutoff trench located 

25 feet upstream of the dam crest, Wakefield sheet piling 38 feet long was driven into the

foundation with part of the sheet piles extending up into the core. Note that these embankment

design changes were included on a relatively small dam.

Several other notable embankment dams were designed and constructed during Period II. These

included: Sherburne Lake, Tieton, McKay, Guernsey, American Falls, Echo, and Cle Elum Dams. 

Most of the embankment dams constructed during Period II were compacted earthfill structures,

with some semi-hydraulic fill dams built too, such as Tieton Dam. Most of them were built on

rock foundations that required the excavation of the overburden soils. Some of these dams

included reinforced concrete core walls the full height of the reservoir, such as at Tieton and

American Falls Dams. Sherburne Lake Dam, completed in 1921, included a vertical zone of

screened gravel located beneath the downstream edge of the crest intended to prevent saturation

of the downstream embankment material. This was one of the earliest uses of a “chimney drain”

inside an embankment dam to control the phreatic surface and porewater pressures. 

Tieton Dam, completed in 1925 with a maximum height of 185 feet above the streambed, was the

highest embankment dam built by Reclamation during Period II. It was the first Reclamation dam

designed on the basis of a stability analysis, and the soil’s shear strength characteristics were

assumed on the basis of the material’s angle of repose. A concrete core wall 10 feet thick was

excavated down a maximum of 134 feet through river-channel deposits and 10 feet into bedrock. 

This foundation wall was constructed by mining out vertical shafts driven to bedrock and

horizontal side drifts, forming a wall within the foundation. The core wall foundation was also

pressure grouted using five holes each 22 feet deep in one of the first such applications (the

maximum grout take was only one sack per foot). Grout is generally a mixture of cement and

water, and possibly sand, bentonite, and other materials. According to Design of Small Dams

(p. 195), “Foundation grouting is a process of injecting under pressure a fluid sealing material into

the underlying formations through specially drilled holes to seal off or fill joints, fractures,

fissures, bedding planes, cavities, or other openings.” The Tieton Dam embankment included a

puddled-clay core one-third the thickness of the hydraulic head constructed against the upstream

side of the concrete core wall. The remainder of the dam was constructed using the semihydraulic fill method in which the earthfill is dumped at the upstream or downstream embankment

shoulder and is sluiced with jets of water, washing the fines into the center pool.

McKay Dam, completed in 1926 with a maximum height of 160 feet above the streambed, rested

almost entirely on bedrock and was constructed of compacted sand and gravel. The upstream

slope at 1.75:1 is the steepest ever constructed on one of Reclamation’s embankment dams and

was covered with a monolithic concrete slab tied to bedrock with a concrete cutoff. Three cutoff

walls were constructed across McKay Dam’s foundation contact, and the foundation beneath each

of the walls was grouted. Steps were cast into the upper part of the upstream concrete facing to

break up the wave runup (unlike the smooth concrete-panel facing at Belle Fourche Dam). The

concrete facing was very hard to construct and the construction engineer advised against using

that design again.
29

Guernsey Dam, completed in 1927 with a maximum height of 105 feet above the streambed,

rested on a pervious foundation of unknown depth. Because of the foundation, the embankment

section included an upstream “blanket” and a large downstream rockfill. The central portion of

the embankment included an inclined impervious core zone confined by zones of sluiced sand and

gravel located upstream and downstream of the core. This was the last hydraulic fill embankment

constructed by Reclamation. A new concept used at Guernsey Dam was the incorporation of the

upstream cofferdam into the embankment section. A partial cutoff trench was excavated and

backfilled with the impervious earthfill.

American Falls Dam, also completed in 1927 with a maximum height of 75 feet above the

streambed, was a combination concrete gravity and earthfill structure. The bedrock foundation

beneath its reinforced concrete core wall was grouted.

Echo Dam, completed in 1931 with a maximum height of 130 feet above streambed, was another

zoned embankment. The central core consisted of compacted clay, silt, sand, and gravel; the

zones upstream and downstream of the core consisted of sand and gravel; and the downstream

toe zone consisted of conglomerate rockfill rolled in 12-inch layers. The excavated cutoff trench

was about 25 feet deep to bedrock and included a concrete cutoff wall. The cutoff trench was

located well upstream of the central core and was connected to it by a thick blanket of the

compacted core material. The earthfill materials were hauled to the damsite using gasolinepowered trucks, the first such use on one of Reclamation’s embankment dams. Compaction of

the embankment materials was accomplished using a sheepsfoot-type tamping roller for the first

time on a Reclamation dam. The sheepsfoot tamping roller was an important development in the

evolution of earthfill compaction because of the kneading action produced by the steel knobs or

“feet” fabricated around the roller drum. Water and/or sand were usually placed inside the steel

drum to increase its weight and thereby the amount of stress applied by the ends of the feet during

compaction.

Cle Elum Dam, completed in 1933 with a maximum height of 135 feet above the streambed, was

the first instance in which a sheepsfoot tamping roller was specified to be used for embankment

compaction (it was used, but was not specified on Echo Dam). Cle Elum Dam was the last dam

designed using just empirical rules and the last one constructed without earthfill testing to verify

the quality of the as-built earthfill materials, to evaluate construction practices, and to confirm

design assumptions. 

Dams generally put more people at risk than other type of civil works structure. Dam failures

tend to be catastrophic, which causes them to be studied very thoroughly to try to explain why the

failure occurred and to avoid repeating any mistakes. The dramatic failures of dams like St.

Francis Dam at about midnight on March 12, 1928, near Los Angeles, California tended to

produce important changes in the practice of dam engineering. By the end of 1929, several states

had enacted laws placing the construction and maintenance of non-Federal dams that imperil the

lives and property of others under the supervision and control of the State engineer or other

authorized official. With embankment dams, the need to explain why a dam failed when the same
30

basic design had worked elsewhere was a major concern to all civil engineers, as well as the

general public. As civil engineering evolved, the increasing knowledge of the engineering design

of certain materials (such as wood, steel, and concrete) that are used in constructing civil

structures (such as buildings, bridges, and dams) generally improved the overall record with

respect to reducing the incidence of structural failure. However, the failure rate with respect to

embankment dams did not seem to keep pace with the evolution of those other civil engineering

structures, and remained of great concern into the 1920s and 1930s. In general, Reclamation had

a very good record with respect to its embankment dams. However, Reclamation’s record was

not perfect, as evidenced by the rapid drawdown failure of the upstream slope of Belle Fourche

Dam in August 1931. While this slumping of the upstream slope material did not breach the dam

or release the reservoir, the steep slope did become unstable and it did fail.

In the years just after World War I, several European engineers began to specialize in the

mechanics of soil and rock materials, and thereby began the field that has become geotechnical

engineering. Dr. Karl Terzaghi (Honorary Member, ASCE) is generally considered the father of

soil mechanics (geotechnical engineering). According to Karl Terzaghi - The Engineer as Artist

by Prof. Richard E. Goodman [18], Karl Terzaghi graduated from the Technical University of

Graz in 1900 with a degree in mechanical engineering, having resisted his grandfather’s civil

engineering profession. However, after a short stint working as a mechanical engineer, Karl

Terzaghi switched and began his life-long career in civil engineering. After receiving his Doctor

of Technical Sciences degree from the Technical University of Graz in 1912, Dr. Terzaghi visited

the United States for the next two years. He quickly found his way to a meeting with Service

Director F.H. Newell and immediately began an extensive tour of Reclamation projects and dams

then under construction. Back in Europe, Dr. Terzaghi began to study the mechanics of soils

toward the end of World War I in 1917, working on the problem of earth pressure against

retaining walls that had been worked on earlier by Coulomb and Rankine. Dr. Terzaghi’s work

(in German) was first summarized (in English) in Engineering News Record in 1920, which wrote

an editorial preface declaring that characterizing earth as an engineering material is “the

outstanding research problem in civil engineering” and that Terzaghi’s article “heralds the opening

of an avenue of progress.” He completed the manuscript for Erdbaumechanik (Principles of Soil

Mechanics) in April 1924 and, after it was translated from German to English, it was circulated

widely in the United States by John R. Freeman (Honorary Member, ASCE). The Massachusetts

Institute of Technology quickly offered Dr. Terzaghi the opportunity to develop a graduate

course in foundations and soil mechanics. Because of Prof. Terzaghi’s background and expertise

in geology, the “marriage” of geotechnical engineering and geology has been one of his more

important achievements. Prof. Terzaghi continued to lead in the development of the new field of

soil mechanics and foundation engineering in the United States, with a continued special interest

in dams until his death in 1963. (In his memory, Mission Dam in British Columbia, Canada was

renamed Terzaghi Dam in 1965.) Briefly described, thus began what is now geotechnical

engineering. The birth of geotechnical engineering as it relates to embankment dams “arrived” at

ICOLD’s First Congress on Large Dams meeting in 1933 at Stockholm, Sweden, which was

quickly followed by ICOLD’s Second Congress on Large Dams meeting in 1936 at Washington,

D.C. Reclamation engineers participated in both of these meetings, including Commissioner
31

Mead and Chief Design Engineer Savage.

Reclamation’s first engineering publication, entitled High-Pressure Reservoir Outlets - A Report

on Bureau of Reclamation Installations by J. M. Gaylord, Electrical Engineer, and J. L. Savage,

Designing Engineer, was published in 1923 [19]. This book of 179 pages included information

and reproductions of drawings on the outlet works designed for and constructed at many

Reclamation dams, including Minidoka, Belle Fourche, Strawberry, Lahontan, Minitare, Jackson

Lake, Sherburne Lake, and McDonald Dams (McDonald Dam was designed and constructed by

the Service under an agreement with Interior’s Indian Affairs Office). A second engineering

publication, entitled Dams and Control Works, was published by Reclamation in 1929 [20]. This

book of 164 pages included information written by Reclamation engineers on various diversion

and storage dams, including Tieton, McKay, Guernsey, American Falls, and Echo Dams. A

section of miscellaneous articles presented information on topics such as: Corewalls for Earth and

Rockfill Dams, and Design and Construction of Small Earth Dams. And the Appendix included a

reprint of the recent specifications on Echo Dam. Included in the article on Design and

Construction of Small Earth Dams was a material placement recommendation for two-zone

embankment dams. This recommendation called for placement of the selected water-tight

material in the upstream portion of the dam, and of the heavy, stable, free draining material such

as sand, gravel, and stone in the downstream portion, distributed such that the coarser material

was placed on the downstream slope, changing gradually to the finer and more claylike material as

the impervious material in the upstream portion of the dam was reached. The importance of the

proper placement of soils with fine-grained vs. coarse-grained gradations within a dam

embankment became much better understood subsequently in the 1940s and 1950s.

Field and laboratory testing of soil and rock materials also began to emerge during the 1920s and

early 1930s. In addition to the pioneering soil mechanics work by Dr. Terzaghi on topics such as

soil permeability, others contributed greatly to the evolution of soil and rock testing in the attempt

to characterize these materials. Reclamation’s Earth Materials Laboratory was established in

Denver at the U.S. Customs House in the fall of 1933. The primary duties of the new Earth

Materials Laboratory “were to determine the characteristics of proposed embankment and

foundation soils, to work with the design section in planning field control tests on the foundation

and compacted embankment, and to train construction inspectors in the test procedure” [21]. 

While the subject of soil compaction and optimum moisture content had been written about as

early as 1907, Ralph R. Proctor developed a soil test procedure in 1933 that established the

principles of soil compaction and moisture content and their application. A four-article series was

published by Engineering News Record beginning on August 31, 1933. Proctor’s compaction

control test standard was quickly adopted by every engineer and organization involved with

embankment dams, which was a major milestone in the history of embankment dam design and

construction. In addition to performing Proctor’s density test, Reclamation’s Earth Materials

Laboratory used or developed a variety of soil testing equipment and procedures, which included

mechanical (grain size) analysis, penetration resistance (on compaction specimens), percolation

and settlement, consolidation, shear strength, specific gravity, and soluble solids. The laboratory

also began to conduct studies and experimentation on different methods of compaction, on the
32

percolation rates in different soils, on porewater pressure movement through different soils, and

on consolidation rates of different soils. The rapid drawdown failure of the upstream slope at

Belle Fourche Dam in 1931 indicated that there was still a lot for Reclamation’s engineers to learn

about soil mechanics and earthfill embankments. 

As Period II began, the World War I advances in mechanized equipment such as tanks and trucks

lead to the post-war development of new construction equipment. Gasoline engines were now

used to power 5-ton trucks for hauling earthfill materials more quickly and with greater economy. 

The new 15-horsepower Caterpillar tractor was introduced and could be used to pull a roller for

earthfill compaction, a Fresno scraper for moving earthfill, or a bulldozer for excavating and

moving earth materials. Further development of larger-sized engines lead to more powerful

Caterpillar tractors and other construction equipment during Period II. As discussed on Echo and

Cle Elum Dams, the use of sheepsfoot tamping rollers for compacting earthfill materials on

Reclamation’s embankment dams began in the late 1920s and early 1930s.

Period III (1934-1944)

Reclamation’s state-of-the-practice in embankment dam design and construction at the beginning

of Period III had developed to a fairly high degree of sophistication. Reclamation’s projects and

dams were often written about in publications like Engineering News-Record and its engineers’

papers were often published in ASCE’s Transactions. Reclamation’s reputation and those of its

engineers were well established in the West and the United States. Reclamation’s evolution in

concrete dams peaked during Period III with the design and construction of Hoover Dam. While

the concrete dams received more notice nationally and worldwide, Reclamation designed and

constructed several milestone embankment dams during Period III.

Reclamation’s centralized engineering design and construction organization and the Chief

Engineer in the Denver Office were well established and empowered. Reclamation’s Chief

Engineers during Period III were Raymond F. Walter (mentioned earlier under Period II) and

Sinclair O. Harper, and J. L. Savage remained the Chief Design Engineer during the entire period.

The embankment dams designed and constructed during Period III involved some revolutionary

changes and they were larger and more numerous than ever before. At about the same time,

testing of earth materials, construction testing for compaction and moisture control, and

engineering design specialization all became part of Reclamation’s embankment dam design and

construction process. The installation of performance monitoring instruments in Reclamation’s

embankment dams became standard procedure during this period.

Data from laboratory testing, construction control testing, and performance measurements

obtained on Reclamation’s embankment dams were collected and analyzed by the specialized

embankment dam design group, which determined that soil as a construction material was

extremely variable and very sensitive. The data also indicated that the performance characteristics

of many types of ordinary soil could not be adequately defined by the existing tests and
33

procedures. Hence, the earthfill construction practices then in use would not necessarily produce

the desired consistent performance. While attempting to solve these concerns and problems, the

successful empirical design and construction practices historically used with success by

Reclamation continued to be followed. Government regulations covering concerns such as

working hours, transportation of equipment, safety, and wage rates became part of the process.

Many notable embankment dams were designed and constructed by Reclamation during Period

III. These included: Hyrum, Pineview, Agency Valley, Rye Patch, Taylor Park, Moon Lake,

Alcova, Caballo, Bull Lake, Midview, Fresno, Green Mountain, Deer Creek, Vallecito, and

Anderson Ranch Dams (the latter dam wasn’t actually completed until 1947). All of these

embankment dams were constructed as compacted earthfill structures. The dams had upstream

slopes ranging from 3:1 to 3.5:1 with flatter slopes at the (upstream) toe where material needed to

be wasted, and had downstream slopes ranging from 2:1 to 2.5:1, similarly with flatter slopes at

the (downstream) toe. These dams were built on a variety of foundations; almost all of them

included a cutoff trench excavated down through the overburden soils to bedrock and quite a few

of them included concrete cutoff walls in the bottom of the cutoff trench. The cutoff trenches

moved toward the center of the dam. The rock(fill) material produced from required excavations,

that was unsuitable for use as upstream riprap, was often placed on the downstream slope of the

embankment.

Pineview Dam, completed in 1936 with an initial maximum height of about 55 feet above

streambed, included a steel sheet pile cutoff in the foundation, which was later determined to be

ineffective, causing little if any porewater pressure drop in the seepage percolating downstream. 

The dam’s crest was raised about 29 feet in 1955. 

Taylor Park Dam, completed in 1937 with a maximum height of 167 feet above the streambed,

was constructed as an embankment dam at a good concrete damsite because of its remoteness. 

Comparative cost estimates were developed for both types of dam, and they indicated little

difference in cost. Contractors were allowed to submit alternative bids, and an embankment dam

was the low bid. This reportedly indicated that earthfill construction had developed to the point

where it could be cost competitive with concrete dam construction at a damsite suited either type

of dam. A large rockfill zone mantles the downstream slope.

Alcova Dam, completed in 1938 with a maximum height of 185 feet above the streambed, was a

fairly complex embankment dam. The foundation consisted of sedimentary rock dipping

downstream that had quite different permeabilities, artesian pressure in one bedrock layer, and hot

sulfurous groundwater. An extensive “U”-shaped grout curtain was constructed in the foundation

and up the abutments to control seepage and uplift. A concrete gallery was constructed on top of

the excavated bedrock to provide access for drilling drain holes and to perform additional

foundation grouting if the need arose. Alcova dam was thoroughly instrumented with the new

hydrostatic pressure indicators at three sections of the embankment to monitor porewater

pressures. A large rockfill zone mantled the downstream slope.
34

Fresno Dam, completed in 1939 with a maximum height of 75 feet above the streambed, was built

on a very soft foundation of questionable strength. Consolidation of the foundation and

settlement of the embankment became major problems as construction progressed. A theoretical

approach and the results of plate bearing tests of the foundation were used to estimate the total

settlement, which was estimated to be relatively minor. However, the actual settlement has been

in excess of 8 feet, about half of which occurred during construction. The base of the dam

embankment was widened, primarily to avoid abrupt changes in the stress in the foundation and to

distribute the load from the embankment. Piezometers were installed in the embankment for the

first time to monitor the development of construction porewater pressures in the earthfill. The

control of embankment compaction and earthfill moisture content proved to be effective in

controlling the earthfill porewater pressures. 

Green Mountain Dam, completed in 1943 with a maximum height of 274 feet above the

streambed, was the highest embankment dam yet built by Reclamation. Collectively, Green

Mountain, Deer Creek and Vallecito Dams marked Reclamation’s initial use of geological data in

formulating the embankment dam’s design. The alignment of Green Mountain Dam was shifted

downstream to avoid an old landslide in the left abutment. The upstream foundation was

excavated to bedrock to remove potentially unstable foundation material. Shale bedrock

unexpectedly deteriorated rapidly on exposure to the air, which was addressed by spraying an

asphalt coating on the shale immediately after it was cleaned off. This procedure became standard

practice on Reclamation dams whenever shale is encountered. The borrow material was

processed to remove the cobble-size (plus 3-inch) particles from the earthfill used to construct the

embankment. The compacted earthfill at Green Mountain Dam achieved the highest dry density

yet at 132 lb/ft3. Even at this high density, construction-induced porewater pressures in the

embankment caused by the weight of the fill were excessive. Studies were begun to discover

what could be done to avoid this effect, with the finding that slight reductions in moisture content

in the earthfill caused a marked reduction in the earthfill porewater pressures. Construction

practices on Reclamation’s embankment dams were changed accordingly.

Anderson Ranch Dam, started in 1941 and completed in 1947 with a maximum height of 

344 feet above the streambed and with a cutoff trench excavated a maximum of 112 feet to

bedrock, set a new record as the World’s highest embankment dam. The scheme developed on

Green Mountain Dam to carefully control the earthfill moisture content to avoid excessively high

porewater pressures was followed on Anderson Ranch Dam, but it wasn’t until near the end of

construction that the moisture content control effort effectively controlled the porewater

pressures. The designed upstream and downstream slopes gradually flatten from crest to toe,

going from 3:1 to 3.5:1 on the upstream slope and from 2:1 to 2.5:1 to 8:1 on the downstream

slope. This was done in an attempt to balance the cost savings from minimizing the embankment

volume (steeper slopes) vs. the need to maintain adequate slope stability (flatter slopes). In 1941,

the design of the embankment slopes on Anderson Ranch Dam was based with some confidence

on the results of the slope stability analyses and the earthfill strength data developed by

Reclamation’s Earth Materials Laboratory. The contractor on Anderson Ranch Dam introduced a

number of innovations during construction, including the use of a belt conveyor system for the
35

transporting the borrow material to the embankment, with facilities for adding moisture to the

material moving along the belt conveyor.

After Dr. Terzaghi and others began to develop geotechnical engineering during Period II, and

after the First and Second Congress on Large Dams meetings in 1933 and 1936, Reclamation’s

engineers joined the national and worldwide efforts in advancing the new field as it related to

embankment dams. Reclamation continued to develop and make available information on its

engineering work. A second edition of Dams and Control Works was published in February 1938

[22]. This soft-cover 261-page book, again written by Reclamation engineers, contained three

parts: One - Storage Dams; Two - Diversion Dams; and Three - Special Articles. Part 3 still

included an article by Engineer F. F. Smith on “Design and Construction of Small Earth Dams.” 

Paragraph 5 of that article contains the statement: “Among Engineers charged with the

responsibility for the safety of large earth dams, it is appreciated that the outworn empirical

methods have given way to thorough preconstruction investigations, careful theoretical design,

and construction on known and definite principles of soil mechanics.” [23] A figure in the article

on page 254 portrays “Methods of Zoning Earth Dams,” and notes that zones 2 and 3 (zone 2

flanks the zone 1 impervious core and zone 3 is located between zone 2 and the rockfill zone on

the downstream slope) “are roughly graded from fine material at the inner slopes to coarse at the

outer slopes”. This grading from finer grained material at the zone 1 core to coarser grained

material toward the outer slopes was generally used on Reclamation’s embankment dams, and

provides the filtering action necessary to prevent soil “internal erosion” (piping). Dr. Terzaghi

seems to have started the work to develop rational filter criteria. The results of his work and the

research work by George E. Bertram with the assistance of Dr. Terzaghi and Prof. Arthur

Casagrande (Honorary Member, ASCE) resulted in a paper by Bertram [24] that is generally

given the credit as the first document on filter criteria. The Corps conducted its own research into

filters in the early 1940s. 

Field and laboratory testing of soil and rock materials continued to be refined in response to the

need of designers to better characterize those materials for potential use in embankment dams. As

noted above in the discussion of Anderson Ranch Dam, the Earth Materials Laboratory was able

to provide the engineering data necessary to optimize the design of the embankment slopes to be

constructed.

Reclamation’s instrumentation for and monitoring of embankment dams continued to be

improved, with the development and installation in 1935 of 13 water level indicators (WLI) at

Hyrum Dam and 12 more WLIs at Agency Valley Dam. The water level indicators were a

combination manometer and piezometer, but it was not sufficiently accurate. This lead to the

development of the hydrostatic pressure indicator (HPI), a modification of the Goldbeck cell,

which were installed at Caballo Dam, Alcova Dam, and several other dams in 1938 and 1939. 

The hydrostatic pressure indicator used a thin gold-plated monel-metal diaphragm, which used air

pressure on one side to balance and measure the porewater pressure on the other side of the

diaphragm. The HPIs were installed in the embankment as it was constructed, and copper tubing

was run in trenches from the instrument to the embankment surface where a recording apparatus
36

could be attached and operated to measure the porewater pressure. Reclamation developed the

more-rugged hydraulic piezometer that could be installed in either the foundation or the

embankment; the first 72 hydraulic piezometers were installed at Fresno Dam in 1939. 

Reclamation also developed the internal vertical movement device, which was first installed at

Caballo Dam in 1936. The device was installed as the embankment was constructed and allowed

the vertical consolidation behavior of the embankment to be measured at 5- or 10-foot intervals

and also measured the settlement of the foundation at the bottom. 

During Period III, the equipment available for the construction of embankment dams continued to

improve in size, power, speed, and efficiency. The rockfill zones included in these dam

embankments could now be constructed because the construction equipment now permitted the

handling of larger and larger sizes of rock particles, which were usually obtained from the

required excavations for the outlet works and/or spillway. The improved construction equipment

and improved techniques for dewatering below the groundwater table allowed the excavation of

cutoff trenches through overburden soils to become larger and deeper where necessary.

Period IV (1945-1975)

Reclamation’s state-of-the-practice in embankment dam design and construction at the beginning

of Period IV had developed to quite a high degree of sophistication. Reclamation’s projects and

dams were generally written about in engineering and construction publications as indicative of

the state of the practice. Reclamation’s reputation and those of its engineers continued to grow

as more milestone embankment dams were designed and constructed during Period IV. 

Reclamation’s Chief Engineers during Period IV were Walker R. Young, Leslie N. McClellan,

Grant Bloodgood, (both McClelland and Bloodgood were also Assistant Commissioners),

Bernard P. Bellport, and Harold G. Arthur (both Bellport and Arthur were also titled Director,

Office of Design and Construction).

The embankment dams designed and constructed during Period IV generally involved more

difficult and complex damsites than had been built on before, and the resulting designs were more

complex. After World War II, a new rush of dam construction occurred because of the delays

caused by the war. The multi-purpose dam and project came into being at Reclamation,

expanding its previous focus on irrigation projects and storage dams. Significant improvements

were made to the construction equipment available at the start of Period IV.

Laboratory testing of earthfill materials saw new improvements in the quality and size of the

apparatuses and instrumentation available for conducting soil and rock testing, aided especially by

the introduction of computers for automated data acquisition during testing. Starting around

1957, Reclamation started to use computers in laboratory testing and in the analysis of slope

stability. Larger sizes of testing equipment allowed research and development of data on the

effects of larger-size particles on the shear strength of the true matrix of earthfill materials being

used in embankment dams. The improved instrumentation used in monitoring the testing allowed

them to be run more slowly and allowed for the measurement of porewater pressures generated
37

during shearing of the saturated specimens. Reclamation’s research into filters was conducted by

K. P. Karpoff, which lead to The Use of Laboratory Tests to Develop Design Criteria for

Protective Filters published in 1955 [25]. 

In October 1961, Waco Dam in Texas, a Corps dam, suffered a slope failure during construction

that dropped the crest 18 feet vertically and caused horizontal movements of up to 26 feet

downstream. The slope failure was caused by a combination of high porewater pressures in the

foundation clay shale generated by the weight of the overlying embankment that were transmitted

through a sand layer and the failure of the low shear strength clay-shale foundation. Research on

testing the Waco Dam foundation clay-shale material and improvements in slope stability analyses

resulted from that event (this became important to Reclamation at the end of Period IV and the

beginning of Period V). 

Sheffield Dam near Santa Barbara, California had failed in 1925 due to earthquake-induced soil

liquefaction in the dam’s foundation. Reclamation became more concerned about the seismic

stability of its embankment dams in the late 1940s and early 1950s, and a technical memorandum

entitled Seismic Stability of Earth Dams [26] by Civil Engineer Elbert E. Esmiol (Life Member,

ASCE and USCOLD/USSD) was published in April 1951. Several large earthquakes occurred

during Period IV, which lead to the development of new soil tests and methods of analysis, trying

to model the loading of and the response by the various soils that occurred during those

earthquakes. The powerful earthquakes that occurred at Nigata, Japan, and in Alaska in 1964

caused geotechnical engineers to begin research on how to model the soil behavior called

“liquefaction” that was exhibited by sandy soils during those events. The near-breaching of

Lower Van Norman (San Fernando) Dam during the 1971 earthquake that hit the Los Angeles

area caused a renewed burst of research into soil liquefaction, field and laboratory testing, and

modeling of the deformations that occurred in the upstream portion of the Lower Van Norman

Dam, a hydraulic-fill embankment. Reclamation’s Soils Engineering Branch participated in the

evolution of field testing and laboratory testing of liquefaction-susceptible sandy soils after the

near earthquake-induced upstream slope failure of Lower Van Norman Dam. Starting around

1962, computers had begun to be used to analyze soil stresses with the newly-developed finiteelement method of analysis. This analysis method was subsequently upgraded to allow the Lower

Van Norman Dam embankment and foundation to be modeled, and to estimate the deformations

produced by the earthquake shaking for comparison with the actual deformations. 

Many embankment dams were designed and constructed by Reclamation during Period IV. These

included: Davis, Granby, Martinez, Box Butte, Scofield, Shadow Mountain, Cascade, Dixon

Canyon, Spring Canyon, Soldier Canyon, Long Lake, Dry Falls, O’Sullivan, Jackson Gulch,

Enders, Medicine Creek, Heart Butte, Bonny, Cedar Bluff, Shadehill, Dickinson, Trenton, Kirwin,

Webster, Cachuma, Carter Lake, Glen Anne, Lauro, Rattlesnake, Tiber, Jamestown, Palisades,

Sly Park, Wanship, Lovewell, Casitas, Vega, Trinity, Navajo, Fontenelle, Merritt, San Luis,

Soldier Creek, Pueblo, and Teton Dams. These Period IV embankment dams generally had

upstream slopes that ranged from 2.5:1 to 3.5:1, with flatter slopes ranging from 4:1 to 20:1 at

the toe where excess material could be wasted. The steep 2.5:1 upstream slopes were used only
38

where an upstream rockfill zone created the necessary strength and stability. The downstream

slopes ranged from 2:1 to 2.5:1, similarly with flatter slopes ranging from 3.5:1 to 20:1 at the toe. 

These dams were built on a variety of foundations; all of them were either founded on bedrock or

they included a cutoff trench excavated down through the overburden soils to bedrock, and quite

a few of them included concrete cutoff walls in the bottom of the cutoff trench. The cutoff

trenches remained near the upstream center of the dam. The rockfill material from required

excavations was generally placed and compacted in the outer slopes of the embankment.

Granby Dam, completed in 1948 with a maximum height of 235 feet above the streambed,

encountered several construction problems that were successfully dealt with. A significant change

in the borrow source for the embankment was accomplished with little adverse effect on the

schedule. An attempt was made to use the surface mapping of the damsite’s geology instead of

the usual amount of investigative drilling; however, the use of this approach (used elsewhere)

proved to be inappropriate due to the complex geology of the damsite. The construction

experience on Granby Dam was discussed in F. C. Walker’s publication: “It was necessary to

perform additional grouting after the structure was placed in operation. However, this grouting

was accomplished so economically that portions of other dams have since been left ungrouted

until actual performance indicates a need for such treatment.” [27] This insight into

Reclamation’s foundation grouting design philosophy by the then Head of the Earth Dams Section

becomes more meaningful when Fontenelle and Teton Dams are discussed.

Davis Dam, which spans the Colorado River, was completed in 1950 with a maximum height of

138 feet above streambed. This dam represented an important advancement because of the

diversion scheme for bypassing the large flow of the river around the damsite. That diversion was

accomplished by excavating an open channel through the left abutment that was later closed by

the construction of a concrete dam, which contained the spillway and the hydroelectric

powerplant penstocks.

Construction of Enders, Medicine Creek, and Heart Butte Dams and several other embankment

dams were all begun around 1946 and 1947 in the Great Plains area where the foundations

generally consisted of relatively weak Cretaceous and Tertiary formations of sand, silt, and/or

clay. These formations tend to be fairly permeable if sandy or structurally weak if clayey. The

valley floors are generally broad and are covered with moderately deep alluvium. The available

borrow materials usually ranged from sandy silts to silty clays, with both gravel and rock (suitable

for use as riprap) scarce to nonexistent. This damsite also had stream flows that were highly

variable, with large floods possible. It proved to be cheaper to increase the size of the reservoir to

increase flood-storage capacity rather than build a larger spillway.

Cachuma (Bradbury) Dam, completed in 1953 with a maximum height of 206 feet above the

streambed, was constructed in a highly seismic area close to where Sheffield Dam had failed

during an earthquake in 1925. The design of the embankment dam was therefore more

conservative than would have otherwise been necessary. A large amount of siltstone and shale

rockfill was produced by the spillway excavation, and this otherwise unsuitable material was used
39

by enclosing it entirely within the downstream sand and gravel zone. In one of the first

applications, a concrete “grout cap” was constructed at the bedrock surface in the center-bottom

of the cutoff trench at Cachuma Dam to provide firm support for the curtain grouting of the

foundation beneath the dam.

Tiber Dam, completed in 1956 with a maximum height of 196 feet above the streambed, was built

on a shale foundation that contained numerous seams of low shear strength bentonite clay. 

Hence, the foundation shear strength was uncertain. The earthfill materials available for use as

the embankment’s central core varied widely in characteristics and shear strength, which was

expected to be low. The embankment cross section therefore reflected these concerns with a

waste material disposal zone between the upstream cofferdam and the upstream slope, and with

downstream slopes ranging from 2.25:1 near the crest to 5.5:1 toward the toe. The embankment

also included zones flanking both sides of the core that transition between the finer-grained clay,

silt, sand, and gravel core founded on bedrock and the coarser outer shells that consisted of sand,

gravel, and cobbles.

Palisades Dam, completed in 1957 with a maximum height of 260 feet above the streambed, was

one of the largest embankment dams yet built by Reclamation. The embankment volume of over

13,500,000 yd3 caused the design to use nearby borrow materials that might otherwise have been

rejected. The borrow soils available were pervious sand and gravel alluvium on the valley floor

and impervious soils along the abutments, which had moisture contents either too high or too low

with respect to optimum moisture for compaction. There was also some concern about

potentially high construction porewater pressures created by the weight of the fill. The design

was adjusted to place the better but wetter borrow soils in the lower and central parts of the

embankment and the drier but poorer borrow soils in the upper and outer parts of the

embankment, while still maintaining adequate slope stability.

Sly Park Dam, completed in 1954 with a maximum height of 175 feet above the streambed, was

one of the first and few rockfill embankment dam designs built by Reclamation. The upstream

rockfill slope was 2.5:1 and the downstream rockfill slope was 2:1. Because of the size of the

rockfill particles, the rockfill material could not be tested in the laboratory. The design therefore

had to assume that the shear strength should reflect the natural slopes of the loose rock in the

vicinity (the angle of repose). Again, the central core of compacted silt, sand, and gravel was

flanked by transition zones, consisting of quarry fines in this case. Because of the difference

between the properties of the compacted central core and the rockfill shells, differential

consolidation between these zones later caused longitudinal cracks along the crest. 

Although vibratory rollers had been developed for compacting cohesionless soils for roads in

Europe in the 1930s, they were first used to compact rockfill dam materials at Quoich Dam in

Scotland around 1958. In the United States, the use of vibratory rollers for compaction of rockfill

materials was first attempted by the Corps at the 445-foot-high Cougar Dam in Oregon, built

between 1959 and 1964. Reclamation first used smooth steel-drum vibratory rollers to compact a

sand and gravel zone at Navajo Dam in 1959. [28]
40

Trinity Dam, completed in 1962 with a maximum height of 465 feet above the streambed, is the

highest embankment dam ever designed and constructed by Reclamation, and its volume of

29,400,000 yd3 made it the largest yet built. Almost all of the overburden material was excavated 

such that the embankment rested almost entirely on bedrock. The embankment contained four

zones, grading from the central core to outer toe zones of rockfill. The upstream slope ranged

from 2.5:1 in the upper slope to 4:1 in the lower rockfill toe zone. The downstream slope ranged

from 2:1 near the crest to 3:1 in the lower rockfill toe zone. The upstream and downstream

rockfill toe zones were added to improve stability; the rockfill was placed in 3-foot-thick layers

(without compaction). A belt conveyor system over 10,000 feet long, that dropped 1,000 feet in

elevation and handled 1,850 yd3/hr, moved a total of about 10,000,000 yd3 of earthfill material

from the borrow area to the damsite. 

Navajo Dam, completed in 1963 with a maximum height of 388 feet above streambed, had a

miscellaneous earthfill zone downstream of the central core that was completely enclosed within a

zone of “selected sand, gravel, cobbles, and boulders.” That selected sand, gravel, cobbles, and

boulders zone formed an inclined transition/drain zone between the core and the miscellaneous

earthfill and formed a blanket/drain zone against the downstream bedrock foundation.

Fontenelle Dam, completed in 1964 with a maximum height of 128 feet above streambed, 

included: irrigation canal outlet works in both abutments, a river outlet works near the middle of

the dam capable of passing 18,700 ft3/s, a hydroelectric powerplant, and a right abutment

overflow spillway of 20,000 ft3/s capacity at full pool. The river outlet works was large because it

was less costly than increasing the size of the spillway. The embankment cross-section is shown

in Figure 11 below. The embankment zoning included: the zone 1 core, the zone 2 

Figure 11 - Fontenelle Dam Section

chimney and blanket drain of selected (pit run alluvium) sand, gravel, and cobbles, and a zone 3

miscellaneous fill that was completely enclosed within the Zone 2. The surface of the bedrock

foundation was far more broken than had been anticipated, so the cutoff trench was deepened by

6 feet. The foundation and abutments were grouted by a single-row grout curtain installed

through a grout cap. Grout takes in the upper 65 feet of the foundation were very large and a
41

second line of grout holes was placed in the vicinity of the river outlet works and in the right

abutment to perform additional grouting. The grouting program included a total of 45,900 linear

feet of drill hole and 143,000 ft3 of cement grout pumped into the foundation, for an average

grout take of 3.1 ft3 per foot of hole. Reservoir filling was to be very slow so that if any seepage

leaks occurred, they could be plugged before permanent operations commenced (remember the

previous reservoir filling and additional grouting experience on Granby Dam.) There was no

surface treatment of the foundation rock beneath the zone 1 core, such as slush (lean cement)

grouting of surface cracks, and smoothing of the foundation with dental concrete.

First filling of the 345,000 acre-foot reservoir commenced in April 1964. During the summer of

1964, after the reservoir had risen to a depth of about 49 feet, seepage appeared in the floor of an

exhausted borrow area 2,000 feet downstream of the dam and stabilized at a flow of 6 ft3/s. The

reservoir continued to fill through the spring runoff from the heavy snowpack winter of 1964-

1965 (which produced a peak reservoir inflow of 17,560 ft3/s) until it reached a depth of about 

85 feet in early June 1965. Seepage then began to discharge from a rock cut in the spillway

discharge channel and from a cliff face about 0.6-mile downstream on the left abutment. The

seepage flowing from the downstream borrow area also appeared to have increased. The

reservoir began to spill on June 15th and the rate of total seepage increased to about 70 ft3/s. A

small slough occurred at the edge of the embankment on the left side of the spillway chute at

about the mid-height of the dam on June 29th, with about 1 ft3/s issuing from a crack in the rock

beneath the chute. On the morning of September 3rd, a wet spot was observed on the downstream

slope of the dam at about mid-height near the right abutment about 100 feet to the right of the

slough that occurred in June. By mid-afternoon, seepage water started flowing from the wet spot

area, causing erosion and sloughing of the dam embankment material. The flow that evening was

estimated at about 5 ft3/s. Local officials were then alerted to stand by, ready to evacuate

downstream residents. The next morning (September 4th ), the seepage flows had increased to

about 21 ft3/s and an estimated 10,500 yd3 of material had been eroded from the downstream

slope (see Figure 12 on next page). Rockfill was dumped into the hole on the downstream slope,

trying to stop the erosion, and the seepage flows appeared to stabilize. On the morning of

September 5th, it was decided to fully open the outlet works, and by the morning of the 6th the

reservoir level had dropped 8 feet from the initial level. That afternoon, an area on the dam crest

about 20 feet in diameter near the upstream edge collapsed (see Figure 13 on page after next

page) and dropped about 30 feet, exposing bedrock on the abutment side of the cavity. The

reservoir continued to drop about 4 feet per day until the pool was low enough to halt the

seepage. 

There were several causes for the near-breaching (and near-failure) of Fontenelle Dam, which was

barely avoided because of the large outlet works capacity. According to Chief Engineer

Bellport’s “appraisal of the accident” included in his paper Bureau of Reclamation Experience in

Stabilizing Embankment of Fontenelle Earth Dam [29] presented at the 1967 ICOLD Conference 
42

Figure 12 - Fontenelle Dam - Large Sinkhole on Downstream Slope

in Istanbul, Turkey, “It is apparent that the weak spot was in the abutment and not the

embankment. Many dams have been placed on similar foundations. ... With steep abutments, it is

difficult to obtain adequate shallow grouting because of the low pressures that must be used to

prevent movement in the foundation.” [30] The single row grout curtain was judged to have been

inadequate, given the nature of the sedimentary shale and sandstone bedrock jointing in the

abutments. The problem was (supposedly) fixed by a grouting program consisting of eight lines

of grout holes in the steep right abutment; a total of 80,000 feet of hole was drilled and an

additional 200,000 ft3 of grout were pumped into the abutments during August-December 1966. 

Bellport commented in the paper that “In the 20-year span from 1940 to 1960, increasing

boldness in reducing the number of lines and amount of grout seemed to be proving a philosophy

that grouting was mostly superfluous. At the Bureau of Reclamation too, in situations where

deficiencies could be readily remedied, the process of “try and see” was being used with

increasing success until the situation at Fontenelle Dam was encountered.” [31] Further, “This

difficulty occurred on first filling of the reservoir which was unusually rapid due to extremely

large inflows and the fact that the outlet works was not being used so that some repair work 
43

Figure 13 - Fontenelle Dam - Crest Sinkhole

could be performed. This experience illustrates the need for slow, controlled filling of reservoirs

where unfavorable foundation conditions are known to exist.” [32] Within Reclamation, it

appears that information on the near failure of Fontenelle Dam may not have been widely

distributed, but other organizations, such as the Corps, reportedly changed some of their

embankment dam design and construction practices after reviewing this incident. Fontenelle Dam

will be discussed further under Period V.

Merritt Dam, completed in 1964 with a maximum height of 120 feet above the original ground

surface, was the first embankment dam that used “soil cement” instead of rock riprap to protect

the upstream slope. Merritt Dam is located on the Snake River in north-central Nebraska where

the usual rock riprap material was not economically available. Reclamation had developed and

successfully used soil cement on a test section constructed in 1951 at Bonny Reservoir in eastern

Colorado. Since its first success at Merritt Dam, soil cement slope protection has been used on

twelve more embankment dams by Reclamation and on countless other structures. 

San Luis Dam, completed in 1967 with a maximum height of 244 feet above the original ground
44

surface and a volume of over 77,000,000 yd3, is the largest embankment dam by volume ever

designed and constructed by Reclamation. The embankment included a central impervious core

with a volume of about 42,000,000 yd3. The borrow material was excavated using a BucyrusErie wheel excavator with a 30-foot-diameter digging wheel equipped with ten 21⁄2 yd3

 buckets. 

This machine had a capacity of about 4,000 yd3/hr and loaded a 100-ton Euclid bottom-dump

truck every 45 seconds. In September 1981, a rapid-drawdown of the reservoir lead to a slide in

the upstream slope that was caused by a weak clay layer in the foundation. The slide was about

1,300 feet long and involved the reconstruction of the upstream slope and construction of a berm

along the toe, with a total volume of about 1.4 million yd3.

Soldier Creek Dam, completed in 1973 with a maximum height of 251 feet above streambed, was

built to enlarge the reservoir originally impounded by the 1913-era Strawberry Dam, which was

then breached when the water on both sides equalized. The design and construction of Soldier

Creek Dam were similar to Fontenelle Dam. Soldier Creek Dam was one of seven dams (both

embankment and concrete dams) selected by the Department of the Interior for a post-Teton 1977

study by W. A. Wahler & Associates to review recently completed Reclamation dams. Soldier

Creek Dam will be discussed further in the Period V section.

Pueblo Dam, completed in 1975 with a height of 165 feet above original ground, was a composite

dam consisting of a concrete massive-head buttress structure containing the 550-foot- long

spillway, flanked by two earthfill embankments. The concrete structure was 1,750 feet long and

consisted of 23 buttresses with a maximum height of 176 feet. The two wing embankments

wrapped around the ends of the concrete structure and consist of the 3,570-foot-long left

embankment and the 4,910-foot-long right embankment. Bedrock at the damsite consisted of

flat-lying Cretaceous sediments in alternating units of sandstone, limestone, and shale. The

concrete dam section was founded on Dakota sandstone and the embankments rest partly on

alluvium in the valley bottom and on Graneros shale on the gently rising abutments. The Dakota

sandstone contained a few discontinuous lenses and seams of shale. The Graneros shale

contained a number of seams of bentonite clay up to 6 inches thick. When the left embankment

had risen to within about 20 feet of the final crest elevation in November 1973, the inclinometer

casing located at the downstream toe at station 90+00 indicated a downstream shear deformation

through the casing that prevented the lowering of the inclinometer instrument. Additional

inclinometer casings were installed along the downstream toe of the left embankment, which

finally indicated the deformation had stopped, after reaching a total of about 6 inches of

downstream deformation. There were no piezometers installed in the shale or the bentonite clay

seams prior to embankment construction that might have indicated the amount of constructioninduced porewater pressure in the foundation. Sampling and laboratory testing of the Graneros

shale were performed, and finite element analyses were conducted to help judge whether a longterm stability problem was indicated by this foundation deformation. This left embankment

deformation in the foundation, which occurred during construction, appears to have been similar

to what occurred during construction at Waco Dam in 1961, although not to the same degree. 

The left and right embankments were both completed and the dam and reservoir were put into

service. Pueblo Dam will be discussed further in the Period V section.
45

Teton Dam was constructed between February 1972 and November 1975, with a maximum height

of 305 feet above the streambed. The embankment cross-section was remarkably similar to that

of Fontenelle Dam (see Figure 14 below). The wide zone 1 core consisted of silt, flanked 

Figure 14 - Teton Dam Sections

upstream and downstream by zone 2, which consisted of (pit-run alluvium) selected sand, gravel,

and cobbles. There was also a zone 3 miscellaneous earthfill zone downstream, with zone 2

constructed as a chimney filter/drain and as a 20-foot-thick drainage blanket beneath the zone 3

and up the abutments. The outlet works at Teton Dam consisted of the river outlet works with a

capacity of 3,400 ft3/s and an auxiliary outlet works with a capacity of 850 ft3/s. The construction

schedule required that the river outlet works be operational by May 1, 1976, but the contractor

was behind schedule and only the auxiliary outlet works were operational to control reservoir

filling.

Foundation grouting at Teton Dam consisted of 3 lines of grout holes up to 310 feet deep. A

test-grouting program was conducted in 1969 and was to inject about 260,000 ft3 of grout into

the foundation. The actual test grouting program pumped twice that amount of grout during the

pilot grouting program, and just two of the test holes took 16,000 sacks of cement and 18,000

sacks of sand, for an equivalent total of about 34,000 ft3 of grout. During actual construction, the

grout was injected into 118,179 lineal feet of drilled holes and totaled: 496,515 ft3 of cement,

82,364 ft3 of sand, 132,000 pounds of bentonite, and 418,000 pounds of calcium chloride. 

Looking at just the cement and sand grout materials, the above figures equate to about 4.9 ft3 per

foot of drill hole, or an increase of over 50 percent compared to the initial grouting done at
46

Fontenelle Dam. Beneath the zone 1 core, the rock foundation surface was cleaned using air and

water jets and some open joints and cracks in the bottom of the key trenches and the cutoff trench

were treated by installing pipes and grouting with a grout slurry, or by filling with specially

compacted zone 1 material. Surface grouting stopped at elevation 5205. [33] The

instrumentation installed at Teton Dam consisted of surface settlement points and strong motion

accelerographs; there were no piezometers installed in the dam embankment or foundation. 

Reclamation’s embankment dam design engineers made only two visits to the damsite during

construction; the construction liaison engineer made six visits during construction.

Data on the dam obtained during subsequent investigations were summarized in the paper Teton

Dam: Summary of Technical Investigations by D. J. Duck, R. W. Kramer, and L. W. Davidson

that was presented at the 13th ICOLD Congress in New Delhi, India in 1979 [34]. The zone 2

chimney filter and drainage blanket located downstream from the core was intended to: filter the

zone 1, prevent water from attacking the zone 3, reduce seepage pressures, and transmit seepage

flows to the downstream toe. The permeability of the zone 2 material was not tested prior to

construction. The zone 2 contained 2 to 12 percent silt fines, average 4.5 percent; had been

placed at a relative density ranging from 80 to 120 percent, average 94 percent; and had a

permeability that ranged from 0.7 to 39.3 x 10-6 cm/s, average 9.4 x 10-6 cm/s. The zone 1 silt

had a mean horizontal permeability of 5 x 10-6 cm/s, which was just a bit lower than the average

for the zone 2 material [35]. These permeability numbers indicate that the zone 2 filter/drain

material was nearly as impervious as the zone 1 core material. According to Peter Aberle, Field

Engineer on Teton Dam construction, when it rained during construction, the water would pond

on the zone 2 surface [36]. It appears that the as-constructed zone 2 did not have sufficient

permeability to function as the intended blanket drain. 

First filling of the 288,000 acre-foot reservoir commenced in October 1975 with the reservoir at

elevation 5060. The design considerations required that the reservoir not be filled faster than 

1-foot per day above elevation 5200. In early March 1976, with the reservoir 135 feet deep at

elevation 5170, the filling rate limit in the design considerations was “relaxed” and filling rate of 

2 feet per day was “allowed” to accommodate the high reservoir inflows from a large snowmelt

runoff. However, they had no other option but to relax the reservoir filling rate limit and accept

the 2-foot-per-day rate of rise - the river outlet works weren’t yet operational! By early May

1976, the reservoir was 185 feet deep. The decision was “made” (note once again the inoperable

river outlet works) around May 13th to fill the reservoir to the spillway crest, which lead to an

average filling rate of about 3 feet per day, and a maximum rate of 4.3 feet per day. Teton Dam

failed catastrophically on June 5, 1976, when the reservoir had reached the spillway approach

channel at elevation 5301.7. The failure of this embankment dam killed 11 people, left 

25,000 people homeless, inundated partially or completely an area of about 300 mi2 that extended

80 miles downstream, and did property damage estimated at about $400 million. This dam failure

changed the Bureau of Reclamation in many, very significant ways. The construction of Teton

Dam therefore completes Period IV. The failure of Teton Dam will be discussed further in the

Period V section. 
47

During Period IV, Reclamation’s engineers continued to enjoy national and worldwide acclaim as

they helped to advance the new field of geotechnical engineering and its sub-specialty of

embankment dams by conducting research and publishing reports and professional society papers. 

Reclamation continued to develop and make available information on its engineering work. A

total of 6,000 copies of the “tentative edition” of Reclamation’s Earth Manual were printed and

distributed in 1951, followed quickly by another 28,000 copies of the “first formal edition”. The

Earth Manual was a huge success worldwide and was in great demand. A First Edition -

Revised, Second Printing was printed and distributed in 1968 with 783 pages. The Earth Manual

combined and revised three earlier manuals: the Earth Materials Laboratory Test Procedures; the

Field Manual for Rolled Earth Dams; and the Earth Materials Investigation Manual. The Earth

Manual was prepared by Reclamation’s engineers in the Earth Dams Section, Dams Branch,

Division of Design, and in the Soils Engineering Branch, Division of Research, with editing and

coordination performed by John (Jack) W. Hilf of the Earth Dams Section. Reclamation’s Design

of Small Dams was published and distributed in 1960, with a Second Edition released in 1973. 

Reclamation’s instrumentation for and monitoring of embankment dams continued to be improved

during Period IV. During the 1950s, several modifications were made to the piezometers used on

Reclamation’s embankment dams. The tubing used between the hydraulic piezometer tip and the

embankment surface was updated to polyethylene tubing. In the 1960s, the tubing was updated

again to polypropylene. Reclamation researched and developed the use of carborundum disks in

the hydraulic piezometer tips in the 1950s for improved measurement of porewater pressures. In

1959, the use of ceramic filter disks in the piezometer tips was first attempted by Reclamation at

Steinaker, Sherman, and Merritt Dams. The first strong-motion earthquake instrument was

installed at Hoover Dam in 1937, and Cachuma (Bradbury) Dam was the first embankment dam

to have one installed in 1954. There are now over 20 embankment dams instrumented with such

devices. As noted earlier, Reclamation seems to have cut back on the amount of instrumentation

installed in its dams during Period IV. 

During Period IV, the variety of equipment available for the construction of embankment dams

continued to improve in size, power, speed, and efficiency. As already mentioned, the wheel

excavator used at San Luis Dam produced 4,000 yd3 per hour, and the earthfill haul trucks used

there were 100-ton capacity bottom-dump wagons. The versatile front-end wheel loader with a

bucket of up to 12 yd3

 capacity was added to the construction equipment available. Earthfill

compaction rollers and scrapers became self-propelled instead of having to be towed behind a

Caterpillar bulldozer or tractor. After its initial use at Cougar Dam, the vibratory roller, both the

smooth drum and later the tamping pad-foot varieties, became available for improved compaction

of earthfill and rockfill materials. 

Period V (1976-2002)

At the start of Period V, the failure of Teton Dam on June 5, 1976, began a chain of events during

which Reclamation’s design and construction organizations changed dramatically. As already

mentioned, the first filling of the reservoir was very rapid, due to the earlier-than-usual high
48

inflows from a heavy snowpack in the mountains upstream. The reservoir inflow peaked at

around 4,000 ft3/s in mid-May. It should be noted again that Teton Dam’s main river outlet

works in the left abutment, with a full-pool capacity of 3,400 ft3/s, was not yet operational

because the regulating gate had not yet been received from the manufacturer. Only the auxiliary

outlet works in the right abutment, with a capacity of only 850 ft3/s, could be used to control the

rate of reservoir filling, or to lower the reservoir water surface in the event of a Fontenelle Dam

type of emergency drawdown situation. Hence, even if the main river outlet works had been

operational, the releases from the combined outlet works would have been about equal to the

inflows and would not have been able to drop the reservoir pool as had been the case at

Fontenelle Dam.

On June 3rd, with the reservoir at about elevation 5300, two small seeps flowing about 60 and 

40 gal/min were found 1,300 and 1,500 feet, respectively, downstream of the dam at the base of

the right abutment. On June 4th, a small seep was found flowing about 20 gal/min at the base of

the right abutment about 150 to 200 feet downstream from the toe of the embankment. At about

7:00 a.m. on June 5th, a survey party observed a leak coming from the right abutment at the top of

a berm at elevation 5045. It was immediately reported to one of the field engineers who drove to

the dam and at 8:15am, he estimated the leak to be flowing 20 to 30 ft3/s. At about 9:10 am, a

slightly muddy leak was observed exiting from the right abutment at elevation 5200, flowing

Figure 15 - Teton Dam - Downstream Sinkhole at About 11:20 a.m.
49

about 2 ft3/s. The lower leak at elevation 5045 was estimated to be flowing 40 to 50 ft3/s at about

9:30 a.m. Between 10:00 and 10:30 a.m., a wet spot was observed on the downstream slope of

the dam at elevation 5200 and about 15 to 20 feet from the right abutment. The wet spot quickly

increased to a flow of 10 to 15 ft3/s and was eroding the material on the downstream slope. At

about 10:30 a.m., a loud sound (roar) was heard, followed by the sound of rapidly running water. 

At about 11:00 am, a whirlpool formed in the reservoir about 150 feet from the right abutment

and its diameter rapidly began to expand. By about 11:20 a.m., attempts to bulldoze rockfill into

the opening (as had been done at Fontenelle Dam) proved futile (see Figure 15 on previous

page). 

Figure 16 - Teton Dam - Crest Collapsed at 11:55 a.m.

A sinkhole developed on the downstream slope shortly before the embankment crest collapsed at

11:55 a.m. (see Figure 16 above), and the dam was breached two minutes later at 11:57 a.m. (see

Figure 17 on next page). This sequence of observed new seepage, wet spots, erosion, sinkhole,

whirlpool, crest collapse, and embankment breaching took only five hours from start to finish and

the complete release of the reservoir followed. By 5:00 to 6:00 p.m. that same day, the reservoir

had completely emptied.

On June 8, 1976, just three days after the failure of Teton Dam, the Under Secretary of the

Interior, D. Kent Frizzell, established the Department of the Interior Teton Dam Failure Review

Group (IRG) that was formed to examine the causes of the dam’s failure and to make 
50

Figure 17 - Teton Dam - Dam Completely Breached

recommendations as appropriate to prevent the recurrence of such failures. The IRG was directed

to “review the following aspects of the failure: geologic, engineering, design, construction,

hydrologic factors, and all other pertinent background information and testimony.” The IRG was

composed of representatives from several Federal Government agencies, such as the Soil

Conservation Service, the Tennessee Valley Authority, and the U.S. Army Corps of Engineers. 

The Secretary of the Interior, Thomas S. Kleppe, and the Governor of Idaho, Cecil D. Andrus,

empowered another review group of experts not associated with the Federal 

Government, who were referred to as the “Independent Panel to Review Cause of Teton Dam

Failure” (Independent Panel). The IRG and the Independent Panel operated simultaneously from

June to December 1976, with field investigations coordinated and the results shared by the two

groups. The Independent Panel’s report Failure of Teton Dam was published in December 1976
51

[37]. The IRG’s Failure of Teton Dam - A Report of Findings was published in April 1977 [33],

and its Failure of Teton Dam, Final Report was published in January 1980 [38]. The reports/

conclusions of the IRG and the Independent Panel were in general agreement, concluding that the

failure of Teton Dam had been caused by:

1. Internal erosion (piping) of the core of the dam deep in the right foundation key trench,

with the eroded soil particles finding exits through channels in and along the interface of

the dam with the highly pervious abutment rock and talus, to points at the right groin of

the dam;

2. Seepage moving through openings that existed in inadequately sealed rock joints, and

that may have developed through cracks in the core zone in the key trench;

3. Once started, piping progressed rapidly through the main body of the dam and quickly

lead to complete failure; and

4. The design of the dam did not adequately take into account the foundation conditions

and the characteristics of the soil used for filling the key trench.

Regarding Cause No. 1 above, it should be noted that the apparently impervious zone 2 blanket

drain material probably confined the seepage flows and eroded zone 1 core material within the

abutment channels, joints, fractures, and cracks all the way to the right groin downstream, and

prevented the safe, proper interception and collection of the seepage flows. The nature of the

damsite geology, the design of the dam embankment, the treatment(s) of the foundation bedrock

surface and open joints (or lack thereof), the characteristics of the embankment materials, the

defensive measures taken to control seepage and piping erosion, and the construction practices at

Teton Dam were all too similar to those involved on Fontenelle Dam. The IRG and the

Independent Panel both recommended that Reclamation should take certain specific measures to

prevent the recurrence of another dam failure:

1. An independent board of review should be convened for each major dam project to

review both design and construction at frequent intervals;

2. Design decisions should be formally documented;

3. Design personnel should remain involved with a project during construction, including

frequent scheduled site visits; and

4. Major dams and their foundations should include an instrumentation program to

monitor construction and post-construction behavior. Instrumentation data should be

promptly interpreted and evaluated.

In a July 20, 1976, letter, the Comptroller General of the United States was asked by U.S. House
52

of Representatives’ Environment, Energy, and Natural Resources Subcommittee to examine the

dambuilding procedures and practices used by the Bureau of Reclamation and the Corps of

Engineers. The resulting report Actions Needed to Increase the Safety of Dams Build by the

Bureau of Reclamation and the Corps of Engineers was published on June 3, 1977 [39]. The

Comptroller’s report discussed several concerns involving the dam designers, recommending that

“We recommend that the Secretary of Interior direct the Bureau of Reclamation to establish

written procedures to better ensure that design intent is achieved. In so doing the Bureau should:

(1) evaluate and implement ways to improve the clarity of instructions, specifications, and

drawings; (2) evaluate and implement ways to better ensure that onsite personnel fully understand

the intent of the designers, and (3) develop and implement policies and procedures calling for

more frequent onsite inspections by designers during construction.” [40] The Comptroller’s

report also noted the comments made in the paper by Chief Engineer Bellport about the lessons

learned after the near failure of Fontenelle Dam, and recommended that “Thus, by averting a

disaster at Fontenelle, the Bureau had seemingly learned a valuable lesson regarding reservoir

filling. Yet, at Teton Dam, over 10 years later, the lesson was not applied.” and “We believe that

the failure of Teton Dam and the near failure at Fontenelle Dam should clearly illustrate to

dambuilders the importance of (1) a slow, controlled filling rate during first filling to closely

monitor the behavior of the dam and (2) an operable outlet of sufficient size to release enough

water to lower the reservoir level when emergencies arise affecting dam safety.” [41] 

Reclamation’s organization and its state-of-the-practice in embankment dam design and

construction at the beginning of Period V, which were thought to have been developed to as high

a degree of capability and sophistication as any dam-building organization in the World, were

immediately put under the proverbial microscope. In April 1977, President Jimmy Carter ordered

all Federal agencies that build, maintain, or operate dams to review their dam safety practices. 

Reclamation Commissioner R. Keith Higginson named a team to review Reclamation’s dam

design and construction procedures, and charged the team “to review expeditiously all factors

relevant to safety of dams in the Bureau’s plan-design-construct-operate process and to develop

recommendations which would assure that Bureau procedures follow acceptable standards ...” 

On March 31, 1977, the Department of the Interior contracted with W. A. Wahler & Associates

to conduct a program entitled “An Emergency Study of Seven Completed Bureau of Reclamation

Dams.” All seven dams were recently completed structures, both earthfill and concrete dams. 

The seven dams studied by W. A. Wahler & Associates were: Crystal, Mountain Park, Mt. Elbert

Forebay, Nambe Falls, Pueblo, Ririe, and Soldier Creek Dams [42]. On November 29, 1977,

Commissioner Higginson announced a reorganization plan in which the decentralized field

structure was retained, and the Denver Office became Reclamation’s center for technical review

and support. On November 6, 1979, under Commissioner Higginson, Reclamation changed its

name to the “Water and Power Resources Service”, but changed it back to the Bureau of

Reclamation on May 20, 1981, under Commissioner Robert N. Broadbent. 

Reclamation’s Chief Engineers (now with different titles, which began as Director, Office of

Design and Construction) during Period V were Harold G. Arthur, Robert B. Jansen (title was

changed to Assistant Commissioner for Engineering and Research on February 1, 1978), Rodney
53

J. Vissia, James Cook (acting for 3 or 4 months in 1982), Darrel W. Webber, Felix W. Cook, Sr.

(the title was changed once again in October 1994 to Director, Technical Service Center), and

Michael J. Roluti.

While Reclamation still had many dams and projects in its “pipeline” awaiting funding and

construction at the start of Period V, environmental “clouds” had been gathering on the horizon in

both numbers and power and they wanted to put a halt to the continued construction of new

dams. The embankment dams that Reclamation designed and constructed during Period V

generally involved even more difficult and complex damsites than had been built on before, and

the resulting designs were more complex. Part of this increased design complexity was a direct

result of the findings and recommendations by the IRG, the Independent Panel, and the

Comptroller on the failure of Teton Dam. 

The Wahler Reports on seven of Reclamation’s recently constructed dams presented some fairly

alarming conclusions and recommendations. For example, on Soldier Creek Dam, the Wahler

Report concluded that “there may be significant risk of serious distress and/or failure associated

with filling the reservoir behind Soldier Creek Dam.” And on Pueblo Dam, the Wahler Report

concluded that “the reservoir behind Pueblo Dam should not be permitted to rise significantly

above its present level until certain supplementary investigations and/or actions have been

completed.” After the findings of the Wahler Reports were presented to the Department of the

Interior (and Reclamation), Reclamation responded by beginning its own reevaluation of these

seven dams, which included field and laboratory investigations, new evaluations of the design and

construction, etc. With the conclusions and recommendations resulting from the two Teton Dam

failure reviews needing to be implemented, Reclamation made dramatic changes in its design and

construction organizations. 

In 1978, Reclamation instituted its new Safety Evaluation of Existing Dams (SEED) Program

under the Division of Dam Safety and reporting directly to the Assistant Commissioner -

Engineering and Research (ACER). The SEED Program began a comprehensive review of dam

design, construction, and operation records; analysis of material data; field inspections; and study

of any apparent deficiencies. The Denver Office’s engineering staff was increased to handle the

enlarged program. A Technical Review Staff, also reporting directly to ACER, was added to the

Denver Office and was tasked with independently reviewing all new dam and major structure

designs, modifications to existing dams and major structures, and the SEED Program. 

Reclamation also hired independent consulting engineers and other professionals to review and

approve Reclamation’s dam design and construction work. 

The work by the Denver Office to respond to the embankment dam concerns raised in the Wahler

Reports included field investigations that produced embankment and foundation samples, which

needed laboratory testing to develop information on their engineering properties. This additional

engineering workload and the laboratory testing workload for projects already planned lead to an

increase in the size and capability of the Denver Office Laboratory. Improved electronics and

computers were involved with the upgrading of the Laboratory’s capability. New testing
54

equipment was needed in a few cases because of the nature of some of the dam foundation

problems encountered and for testing new materials such as synthetic geomembranes and

geotextiles. For example, the weak clay seams in the foundation shale at Pueblo Dam required

testing for residual shear strength, which Reclamation had never done before. 

During Period V, Reclamation continued to design and build some notable embankment dams in

the West. These Period V embankment dams included: Mt. Elbert Forebay, Twin Lakes,

Palmetto Bend, Funks, Wintering, Red Fleet (Tyzak), Stateline, Choke Canyon, Sugar Pine,

Ridgway, Calamus, McPhee, McGee Creek, San Justo, Brantley, Davis Creek, Jordanelle, New

Waddell, and Buckhorn Dams. The Period V embankment dams generally had upstream slopes

that ranged from 2:1 to 3.5:1 and downstream slopes that ranged from 2:1 to 1.5:1, with the

steepest slopes at Jordanelle Dam. 

These dams were built on a variety of foundations, but after the foundation problems that in part

caused the failure of Teton Dam, the foundation treatments constructed during Period V were

more aggressive and more “complete” than those previously constructed. This included design

details and features such as: more aggressive cleanup and mapping of foundations, foundation

shaping to flatten steep slopes and remove bedrock overhangs, more dental concrete backfill to

shape abutments, lean cement (slush) grouting of surface joints, thorough blanket grouting in the

upper 20 to 30 feet of the foundation-core contact zone, more lines of curtain grouting, and

removal of more poor-quality bedrock in the foundation. The concrete grout cap used at

Fontenelle and Teton Dams was also eliminated, grouting from the rock surface, removing any

damaged surface rock, or using a reinforced concrete slab so that grout pressure can be applied to

near-surface rock. Blanket grouting is then done after the curtain grouting has been completed.

The embankment dam designs changed in several important ways during Period V. The chimney

filter/drains placed between the core and the downstream shell material were revised to use

processed materials instead to ensure the prevention of internal erosion/piping. A processed

transition/filter zone was used between the core backfilling the cutoff trench and the downstream

alluvium. Blanket drains were used against the downstream foundation. Processing of borrow

soils or the use of imported soil materials to supply the filter gradation(s) necessary was used

more aggressively in the chimney filter/drains and the blanket drains. These filters included 1, 2,

or even 3 zones of different soil sizes and gradations where necessary to prevent potential internal

erosion/piping. These filter/drain systems were interconnected and drained by a perforated toe

drain pipe with emphasis on monitoring seepage flows. There was also more emphasis on

inspection manholes and monitoring devices in the toe drain system, and more emphasis on the

use of relief wells for deeper seepage collection. The design of the embankment constructed

adjacent and around concrete structures such as outlet works and spillways changed, eliminating

the seepage collars around conduits to facilitate compaction by the tires of heavy equipment

rolling next to the conduit instead of regular compaction equipment such as tamping rollers. 

Processed filters and drains were also placed around the downstream section of the conduits. 

New synthetic materials such as geomembranes and geotextiles were used in modifications

constructed at several embankment dams. Several of the embankment dams noted above,
55

including San Justo and Jordanelle Dams, were constructed close to major “active” earthquake

faults in California and Utah, respectively. Starting with the early work by Esmiol [26],

Reclamation has continued to investigate and develop appropriate design requirements for its

embankment dams in the earthquake-prone western U.S. that have been used by many others

worldwide.

Like other dam-safety programs nationwide, the results of Reclamation’s SEED Program and the

reevaluation of the existing dams determined that quite a few existing embankment dams needed

to be modified to improve their condition and to ensure their continued safe operation. A partial

list of Reclamation’s modified embankment dams includes: Jackson Lake, Helena Valley, Soldiers

Meadow (not built by Reclamation), Fontenelle, Navajo, Casitas, Soldier Creek, Pueblo, Lost

Creek, Twin Buttes, Twin Lakes, San Justo, Horsetooth (modification under construction), and

Pineview (modification being designed) Dams. Reclamation has also been involved with the

analysis, design, and construction of modifications to several Bureau of Indian Affairs (BIA)

embankment dams, including Black Lake, Pablo, and McDonald Dams on the Flathead Indian

Reservation in Montana, and dams belonging to the National Park Service.

Red Fleet (Tyzak) Dam, completed in 1978 with a maximum height of 145 feet above streambed,

was one of the first embankment dam designs started by Reclamation after the failure of Teton

Dam. Its design cross-section included the new defensive features: a two-stage transition zone

and chimney filter/drain, a transition/filter zone between the core backfilling the cutoff trench and

the downstream alluvium, and a processed sand and gravel drainage blanket beneath the

downstream shell. 

Mt. Elbert Forebay Dam, completed in 1980 with a maximum height of 92 feet above the stripped

foundation, was built above Twin Lakes as part of a pumped-storage hydroelectric project. The

original forebay reservoir was lined with compacted earthfill, but excessive leakage was detected

and it could have triggered an ancient landslide, endangering the powerplant at the edge of Twin

Lakes Reservoir below. The design was changed to add about 290 acres of 45-mil-thick

reinforced chlorinated polyethylene geomembrane liner covered by 18 inches of earthfill.

Pueblo Dam was identified in the Wahler Report as needing certain supplementary investigations

and/or actions while restricting its reservoir level. Field investigations were performed and

samples of the Graneros shale and bentonite clay seams were obtained for laboratory testing,

along with work to resolve several other concerns. Soil testing was performed to determine the

residual shear strength of the bentonite clay and the test data were used to re-analyze the stability

of the left embankment. The analysis results indicated the downstream slope stability was

inadequate and the left embankment had to be modified to increase its stability. An earthfill berm

2,500 feet long and 35 feet high was constructed along the downstream toe of the left

embankment in 1980-1981. Subsequent analysis of the concrete buttress dam section and a

concern about the low strength shale seams in part of its sandstone foundation resulted in some

recent (1999-2000) modifications to improve its resistance to sliding along the shale seams.
56

Soldier Creek Dam was identified in the Wahler Report as having certain deficiencies that

individually or in combination could jeopardize the safety of the dam. Field and laboratory

investigations were conducted and Soldier Creek Dam was re-analyzed by Reclamation. The

results confirmed that several concerns raised by the Wahler Report were sufficiently serious that

modification of the dam embankment was justified. A lack of instrumentation made it difficult to

evaluate the performance of the dam embankment, which lead to the installation of over 

25 piezometers in the embankment and foundation. The foundation bedrock surface preparation

and the lack of proper treatment with lean cement (slush) grout placed in surface cracks, shaping,

and dental concrete were of concern. The single-row grout curtain also caused concern. The

nature of the zone 1 core material and the fact that it was placed directly against the untreated

foundation bedrock caused concern. The permeability of the unprocessed zone 3 chimney

filter/drain and blanket drain material caused concern, as did the fact that the chimney filter/drain

and the toe drains did not extend all the way up to the full-reservoir water surface. Embankment

and foundation drainage modifications were constructed in 1983-1984 to address these problems

[43].

Fontenelle Dam continued to have seepage and internal erosion/piping problems after is was

supposedly fixed by the additional abutment grouting performed in 1966. Instrumentation

monitoring data in 1983 indicated that a potential dam safety problem was developing, and the

decision was made to modify the dam by installing a continuous concrete diaphragm wall through

the dam and into the foundation. There were several aspects of the existing Fontenelle Dam

embankment’s design that were judged to have been partly responsible for the failure of Teton

Dam, such as vertical to overhanging abutment cliffs, extensive joints and cracks in the abutments,

no processed material placed as a chimney to filter the erodible silty zone 1 core as protection

against internal erosion/piping, and silty core material placed directly against open, unsealed

bedrock joints, cracks, and crevices. Only one solution was judged to be capable of alleviating all

of these potential problems, and construction of a concrete diaphragm wall from the crest of the

dam down through the embankment and the upper highly-fractured bedrock was selected as the

appropriate modification (see Figure 18 on next page). The concrete diaphragm wall had to

avoid damaging the river outlet works near the middle of the embankment and the spillway on the

right abutment. The concrete diaphragm wall modification was constructed between 1987 and

1989. Figures 19 and 20 (on two pages after next page) show the rockmilling equipment used to

excavate embankment and rock for the diaphragm wall at Fontenelle Dam.

Black Lake, Pablo, and McDonald Dams are BIA dams on the Flathead Indian Reservation in

Montana; Reclamation had designed and constructed Pablo and McDonald Dams between 1905

and 1920. At BIA’s request, Reclamation investigated and prepared SEED reports on these three

dams, along with the other 14 dams on the Reservation. Under a contract with the BIA, the

Confederated Salish and Kootenai Tribes entered into an agreement with the TSC for

Reclamation to perform field investigations, laboratory testing, and engineering evaluations to

determine the adequacy and safety of the dams on the Reservation. Starting with the dam of 
57

Figure 18 - Fontenelle Dam - Section of Embankment with Diaphragm Wall

greatest initial concern, the investigation and analysis of Black Lake Dam indicated it needed to be

modified to prevent a piping/erosion failure. The original Black Lake Dam had failed by internal

erosion/piping in 1967, and the replacement embankment dam was judged to have several serious

deficiencies that could result in another piping/erosion failure. Black Lake Dam was modified in

1992 by the construction of a geomembrane liner installed along the upstream right abutment,

across the upstream slope of the embankment, and as a liner beneath part of the reservoir

upstream of the dam. A downstream drainage berm is scheduled to be constructed in the near

future and will hopefully remediate the current situation. 

Pablo Dam was investigated and analyzed next, and it was determined that the upper portion of

the embankment was susceptible to seepage, internal erosion/piping, and potential failure. The

upper portion of the dam was more pervious because two embankment raises had been

constructed and had used more pervious earthfill material than the original embankment. A

geomembrane liner was constructed in 1993-1994, covering the upper embankment to

control/prevent the seepage that had been percolating through it. 

McDonald Dam was the third embankment dam investigated and analyzed. It was located about

1⁄2-mile upstream of the Mission fault, which had experienced a major earthquake about 

7,700 years ago, and which was judged capable of producing a magnitude 71⁄2 earthquake at any 
58

Figure 19 - Fontenelle Dam - Diaphragm Wall Construction

time. The dam embankment had been constructed by Project Manager/Engineer Frank Crowe

(Honorary Member, ASCE) using dumped and sluiced earthfill, with a puddled core created by

sluicing the dumped earthfill (see Figure 21 on page after next page). The embankment and an

outwash foundation beneath part of the dam were judged susceptible to liquefaction and excessive

deformation. Various alternatives were developed and evaluated, with the final decision reached

to completely replace the existing dam embankment, spillway, and outlet works. These

modifications were designed by Reclamation who also provided the construction management

services. It should be noted that the Construction Engineer for McDonald Dam Modification was

on the Design Team. The new McDonald Dam embankment was a completely different

embankment design. The new embankment cross-section included: a textured geomembrane

covered by earthfill and riprap on the upstream slope, an impervious earthfill zone behind the

geomembrane, followed by an inclined processed chimney filter/drain, all of which rest against a

large miscellaneous earthfill zone that sits on top of a blanket drain consisting of processed

drainage material sandwiched between two layers of the processed filter material. The

instrumentation consisted of piezometers in the embankment and foundation, embankment

measurement points, and weirs to monitor seepage flows. These McDonald Dam modifications

were constructed in 1994-1995 and 1999-2000 (see Figure 22 also on page after next), after

which its behavior during resumed filling of the reservoir in 2000 and beyond went very well [44]. 
59

Figure 20 - Fontenelle Dam - Diaphragm Wall - Hydromill Rock Excavator
60

Figure 21 - McDonald Dam - Original Dam in 1920

Figure 22 - McDonald Dam - New Dam in 2000
61

At the beginning of Period V, the failure of Teton Dam and the results of the IRG, Independent

Panel, and Comptroller reviews resulted in many organizational changes as already discussed. 

Several of Reclamation’s embankment dam design engineers retired, leaving a small cadre of

experienced engineers to work with the new staff of engineers then being hired to work on

Reclamation’s new dam safety program and on the embankment dam design work already in the

“pipeline.” That work has been going on for over 20 years now and is expected to continue for

some time. Reclamation’s current dam safety program includes conducting in-depth reviews,

referred to as Comprehensive Facility Reviews (CFR), which are performed mostly by in-house

senior engineers every six years. The CFRs include an examination of the dam and evaluations of:

the dam’s design, analysis, and construction; its structural behavior; its seismic and hydrologic

hazards; its potential failure modes; its failure consequences; a risk analysis; and its performance

parameters. Reclamation has continued to develop, revise, and make available information on its

engineering work. The Earth Manual is now in its third edition, with Part 2 published in 1990

and Part 1 published in 1998 [1]. Part 1 of the Earth Manual (now containing 1,270 pages)

includes updated information on properties of soils, field and laboratory investigations and test

procedures, construction quality control testing of earthfill materials used as foundations and for

dams, canals, and other types of structures built by Reclamation. Part 2

(now containing 329 pages) includes updated information on properties of soils, field

investigations, and control of earth construction. Reclamation’s Design of Small Dams was

revised and published as a “revised reprint” in 1977 and was revised again and published as the 

Third Edition in 1987 [2]. In the 1980s, Reclamation developed its Design Standards, with

Design Standards No. 13 - Embankment Dams [6] covering all of the embankment dam design

issues and concerns; they are all continually updated. Reclamation has continued to make its

technical publications available to the public. Reclamation has recently embarked on a new

program, generally referred to as risk-based analysis of existing structures, to help with its

decision-making process.

Reclamation’s instrumentation for and monitoring of embankment dams continued to be improved

during Period V. Since their first installation at Fresno Dam in 1939, almost 

2,800 hydraulic twin-tube piezometers have been installed at Reclamation’s embankment dams. 

Pneumatic piezometers have more recently been used to measure porewater pressures and

vibrating-wire piezometers are now the piezometer of choice installed at Reclamation’s

embankment dams. In addition to piezometers, other instrumentation often installed at

Reclamation’s new and modified embankment dams includes: observation wells, seepage weirs,

embankment measurement points, strong-motion accelerographs (in earthquake-prone areas), and

inclinometer casings with inclinometers to monitor known slide areas. One important aspect of

current instrumentation is the use of automated monitoring systems at Reclamation’s dams,

allowing timely monitoring of embankment dams in remote locations where winter access can be a

problem. Such automated monitoring systems also allow the data to be used by early warning

systems. The monitoring data are collected by the TSC’s Structural Behavior and

Instrumentation Group who automatically interprets and evaluates the data in a timely manner,

and alerts the appropriate design groups if any of the instrumentation data cause concern. 

Reclamation’s Embankment Dam Instrumentation Manual was published in 1987 [45].
62

During Period V, the variety of equipment available for the construction of embankment dams

continued to improve in size, power, speed, and efficiency as usual. For example, Figures 23 and

24 (see below and next page) show the construction of New Waddell Dam (1986-1992) and 

Figure 23 - New Waddell Dam Construction

the size of the equipment currently used to construct embankment dams. Compare the end-dump

truck in Figure 24 and its 35 yd3

 capacity to the train of 4 yd3 side-dump cars used to construct

Belle Fourche Dam in 1909 shown in Figure 7. Also compare the large excavator in Figure 24

and its 12 yd3 bucket with steam shovel at Belle Fourche Dam with its 21⁄2-yd3 bucket shown in

Figure 7. During Period V, synthetic materials such as high-density polyethylene (HDPE) and

polypropylene were developed into new products, such as corrugated pipe, geomembranes, and

geotextiles, that were promptly put to use on embankment dams where judged appropriate. New

types of equipment related to these new materials and products were developed, and quality

control tests, testing equipment, and detailed test procedures were developed, with Reclamation’s

significant participation in these developments.
63

Figure 24 - New Waddell Dam - Construction Equipment

Conclusion

The information presented in this paper has summarized the U.S. Bureau of Reclamation’s

embankment dam design and construction history. During the past century, Reclamation has

designed and built some of the most significant embankment dams in the West. Reclamation and 

its dam engineers produced many successes and a few failures during that period. Reclamation

and its civil engineers, through the study of both success and failure and the sharing of the

knowledge gained with all professionals worldwide, have indeed played a significant role in the

evolution of embankment dam design and construction during the past century. Starting before

World War II, Reclamation has provided technical assistance to more than 80 countries and has

trained more than 10,000 international colleagues. It is hoped that the lay-person reader of this

paper has gained some appreciation of Reclamation’s history and just how remarkable the

evolution of embankment dam design and construction has been. It is also hoped that the design
64

and construction engineers reading this paper have gained some understanding of Reclamation’s

embankment dam design and construction history, and of the reasons for doing all embankment

dam work with the utmost knowledge, care, and caution. One of the most important lessons

learned from the failure of Teton Dam involved the need for embankment dam designers and

construction engineers to work as a team, with their primary concern being the need to design and

build the very best and safest dam possible.

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66

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67

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