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Civil Engineering Almanac

March marks the anniversary of the formal completion of the Hoover Dam. Constructed between 1931 and 1936 during the Great Depression Hoover Dam is a concrete arch-gravity dam in the Black Canyon of the Colorado River, on the border between Arizona and Nevada. The 726-foot-high structure was the highest dam in the world at the time of construction and it is still the highest concrete dam in the Western Hemisphere. 

 Hoover Dam
Hoover Dam

In 1918, the U.S. Reclamation Service's director and chief engineer Arthur P. Davis proposed a dam of unprecedented height to control the floods on the Colorado River, generate hydroelectric power, and store the river's waters for irrigation and other uses. A dam project of this scale had never been built in America. In March 1931, the Bureau of Reclamation awarded the contract to a consortium of six large construction firms, called Six Companies, Inc., that bid together on the project because it was larger than anyone could handle. Francis T. Crowe was construction superintendent for Six Companies, Inc.

The first concrete was poured into the dam on June 6, 1933, 18 months ahead of schedule. Construction of the dam, powerhouse, and related structures required a total of 4,400,000 cubic yards of concrete, 45,000,000 pounds of reinforcing steel. Bureau of Reclamation engineers calculated that if the dam was built in a single continuous pour, the concrete would take 125 years to cool and the resulting stresses would cause the dam to crack and crumble. Instead, the ground was marked with rectangles, and concrete blocks in columns were poured, some as large as 50 feet square and 5 feet high.

To dissipate the heat generated as the concrete cured, over 650 miles of one-inch pipe were embedded in the concrete to convey refrigerated water. The cooling coils were cut off and filled with grout after each block had cured and cooled. Grout was also used to fill the hairline spaces between columns, which were grooved to increase the strength of the joints. Although there are myths that men were caught in the pour and are entombed in the dam, each bucket only deepened the concrete in a form by an inch. Also, construction engineers would not have permitted a flaw caused by the presence of a human body.

Working around the clock, Six Companies completed the dam two years ahead of schedule. On September 30, 1935, Franklin D. Roosevelt officially dedicated the dam and on March 1, 1936, Secretary of the Interior Harold Ickes formally accepted the dam on behalf of the government.

Once known as Boulder Dam, Hoover Dam is an arch gravity structure rising 726 feet above bedrock. It is 660 feet thick at its base, 45 feet thick at its crest, and stretches 1,244 feet across Black Canyon, impounding Lake Mead. It is located near Boulder City, Nevada, a municipality originally constructed for workers on the construction project. Today, it continues to regulate the flow of the Colorado River and provides a range of benefits, including electricity for more than 1.3 million people and irrigation for 1.5 million acres of land in the United States and Mexico.

Hoover Dam is a major tourist attraction; nearly a million people tour the dam each year. The Hoover Dam was named one of America's Seven Modern Civil Engineering Wonders in 1955 and was designated an American Society of Civil Engineers (ASCE) Historic Civil Engineering Landmark in 1984. The National Park Service designated the Hoover Dam as a National Historic Landmark in 1984. In 1999, the system was named by ASCE as a Civil Engineering Monument of the Millennium.

April marks the birth of American civil engineer John Frank Stevens. Born near West Gardiner, Maine on April 25, 1853, Stevens studied to be a teacher and at the age of 21, with no technical training, decided to move west and take a job in the Minneapolis city engineer's office. Later he went into the growing field of railroad location and construction in several western states. He undertook his first major engineering assignment in 1883, as an assistant to the chief engineer responsible for scouting locations for the Canadian Pacific Railroad's crossing of the Rocky Mountains. By the age of 33, in 1886, Stevens was principal assistant engineer for the Duluth, South Shore and Atlantic Railway, and in charge of building the line from Duluth, Minnesota to Sault Ste. Marie, Michigan, across the Upper Peninsula of Michigan.

John Frank Stevens
John Frank Stevens

In 1889, Stevens was hired by James J. Hill, who had ambitious plans to link the Midwest with the Pacific Northwest via a route south of the Canadian border. Hill hired Stevens as a locating engineer for the Great Northern Railway. During this time, Stevens became the first European American to discover the Marias Pass over the Continental Divide. Stevens Pass in the Cascade Range was named for him. In 1895, Hill promoted him to chief engineer, and later to general manager. During his tenure at the Great Northern, Stevens built over a thousand miles of railroad, including the original Cascade Tunnel. Stevens oversaw the construction of Hill's Great Northern Railway until 1903, when he left for the Chicago, Rock Island and Pacific Railroad, where he was promoted to vice-president.

In 1905 he was selected to be the chief engineer for the Panama Canal project. Stevens' primary achievement in Panama was to build the infrastructure needed for the completion of the canal. Arriving in Panama, he found what he called "about as discouraging a proposition as was ever presented to a construction engineer." The workers were suffering from malaria, yellow fever, poor housing, and malnutrition. The project had too little excavating equipment on hand, and the transportation system was in disrepair.

Stevens understood that his first task was to restore morale. "The digging," he said, "is the least thing of all." He proceeded immediately to build warehouses, machine shops, and piers. Communities for the personnel were planned and built to include housing, schools, hospitals, churches, and hotels. He authorized extensive sanitation and mosquito-control programs that eliminated yellow fever and other diseases from the Isthmus. Stevens saw the early stage of the canal project itself as primarily a problem in railroad engineering, which included rebuilding the Panama Railway and devising a rail-based system for disposing of the soil from the excavations.

Stevens was instrumental in persuading President Theodore Roosevelt to build the canal with locks in the face of opposition from skeptics who preferred a sea-level canal which would have required much more extensive excavation. During his tenure, he also encountered continuing political difficulties. In 1907 Stevens formally resigned from the canal job and returned to the US to resume his railroad work.

In 1917, he was appointed to the American Advisory Commission of Railway Experts to Russia, created by President Woodrow Wilson to improve the Chinese Eastern and Trans-Siberian railroads needed to supply troops to the front during World War I. After the fall of the Russian government that took the new Soviet Union out of the fighting, Stevens formed the Inter-Allied Technical Board under the auspices of the State Department. Headquartered in Harbin, Manchuria, the board worked to protect Allied interests along the railway. In 1923 he returned to the U.S. and continued to work as a consulting engineer, ending his career in Baltimore in the early 1930s. Stevens retired to Southern Pines, North Carolina, where he died at the age of 90 on June 2, 1943. Stevens is buried in the Mount Hope Cemetery in Mattapan, Massachusetts.