The Locks and the Lake: Experimental Engineering Pays off in Panama

A model of the locks made during the construction of the Panama Canal

The construction of the Panama Canal (1904-1914) has been called the largest design-build project of the 20th century. And if the scale of the project is not impressive enough, it would have been impossible to build just two decades earlier. Very recent technological advancements and innovations—in concrete, dredging, steel, electricity, equipment, engines, dynamite, railroads, and many others—meant the difference between success and failure.

Despite an overarching sense that all the problems they faced could be met by the engineers, manufacturers, and labor enlisted to finish the job, many aspects of the canal’s construction remained experimental, and there were no ready alternatives if they failed. Two examples of these “known unknowns” were arguably the most foundational and critical parts of the Canal’s final design: the locks and the lake.

Concrete

Photograph of the concrete lock chambers under construction (Gift of Brad Wilde).

Reinforced concrete was a relatively new construction method, only adopted by the U.S. Army Corps of Engineers in the 1890s and it was being used in Panama on a massive scale to build the three sets of locks – concrete chambers used to raise and lower ships transiting the Canal. No concrete structure of comparable size had ever been built, and the characteristics of the material when used in such high volume were unknown—so much so that the engineers were not sure that the concrete would actually harden or cure properly. Core samples were taken of the lock walls and floors during construction so the integrity could be tested. Imagine if it hadn’t dried!

The use of cement increased seven-fold in the years before the Panama Canal’s construction. The availability of the product and the advancements in the equipment used played a role in the construction’s success.

Cover feature of Scientific American: March 18, 1911 - Larger barrels illustrate increasing cement use.

Increasing cement use as displayed on the cover of Scientific American, March 18, 1911

Gatun Lake

In order for a lock canal to work in Panama, an artificial lake had to be created by damming the Chagres River, the major waterway that flowed across much of the isthmus. The necessary height of the lake’s surface had to be calculated by examining data on rainfall, water level, and flow that had been collected for over 50 years. It also required projecting into the future about the potential extremes of flood or drought. A topographical study was begun to determine the exact watershed and shoreline, and despite the many variables that remained unknown, construction of the Canal progressed. As late as 1912, only two years before the Canal’s completion, the engineers still had only an approximate understanding of what the ultimate shoreline of the lake would be and questions remained about if the lake would hold water or if it would slowly seep through the ground, but at that point there was no turning back. Can you imagine spending 10 years and 8 billion dollars (in today’s money) and then watching it all literally drain away?

Two men in a boat on Gatun lake, amid recently submerged trees and vines.

Gatun Lake appears in this early photograph from December, 1912. The caption notes that the water rose 52.5 feet above sea level (Gift of Mickey Fitzgerald).

In the photo below, you can see a group of men studying the two experimental scale models that were created to help the engineers decide which type of spillway to build within Gatun Dam. At the time of its construction, Gatun Dam was the largest earthen dam in the world – half a mile thick at the base, a mile and a half long at its crest, and 105 ft above sea level. The choice to build an earthen dam was another controversial and debated engineering decision. Some believed a masonry dam was needed, in part because of the famous 1889 collapse of the earthen dam near Johnstown, Pennsylvania. However, extensive boring samples and testing of the soil composition suggested that the location lacked the solid foundation that a masonry dam would require.

Engineers examine a scale model of the Gatun spillway used in testing.

Engineers test one of two scale models of the Gatun spillway.

Shortly after the United States had completed construction, the Canal’s success was portrayed in opposition to the French who had failed in their attempt to dig a canal across Panama in the 1880s. Ferdinand de Lesseps, who is referenced in the quote as “the great constructor,” had successfully created the Suez Canal in 1869 and was in charge of the French effort in Panama.

“…the great constructor in the joining of the two seas in the Eastern Hemisphere had driven his luckless sun-chariot into oblivion under the tropical suns of the Western World.” (Ira Bennett, History of the Panama Canal, 1915)

To learn more about the engineering of the Panama Canal visit our current exhibit, The Cutting Edge, on display until March 2024 in the Albert H. Nahmad Panama Canal Gallery on the first floor of Smathers Library. The digital exhibit can be viewed by clicking the button below.

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