Atlantic Divison map

was confident. He authorized creation of scale models to test the effects of water pressure on various combinations of materials proposed for use in the dam. Through such means, Goethals and his assistants designed and verified the integrity of Gatun Dam.

To build the dam, train cars dumped solid rock removed from the Culebra Cut onto two parallel ridges across the 1.5-mile-long site. The ridges, known as toes, were 4,000 feet apart and 60 feet high. Once the toes were in place, dredges pumped impervious clay into the space between them from the surrounding river bottoms. Ultimately, the stone and earth dam was a half-mile wide at its base, 500 feet wide at the lake’s waterline, and 115 feet tall. The dam contained 22 million cubic yards of material and covered 288 acres. In the center of the dam, engineers built a concrete spillway that could discharge 182,000 cubic feet of water per second if a major flood threatened the canal. Thirty-two miles away, on the other side of Culebra Cut, a much smaller dam terminated the lake at Pedro Miguel. The locks there lowered ships into a 1.5-mile-long man-made lake that afforded navigation to the last set of locks at Miraflores. In total, all but 15 miles of the Panama Canal is traversed upon lakes impounded by dams that were designed and constructed by the Army’s finest engineers.

Dumping rock from rail cars to create Gatun Dam
Diverting the Chagres River

Miraflores spillway dam under construction
Excavating the Miraflores Spillway

Gatun Dam and Lake

Under the American canal plan, ships would transit the Panamanian interior not via a narrow river or channel but across an enormous man-made lake. Thirty-two of the canal’s fifty miles would take the form of a 164-square-mile lake with 1,016 miles of shoreline – it would be the largest man-made lake in the world when completed. The lake would accommodate navigation from Gatun on the Atlantic side all the way through the Culebra Cut (later renamed the Gaillard Cut) near the Pacific. In order to create the lake, a board of Army and civilian engineers proposed damming the Chagres River near Gatun, where its valley narrows to a mile and a half wide. To impound the 183 million cubic feet of water necessary to fill the lake, engineers designed the largest earthen dam ever conceived. Many Americans and international engineers doubted the feasibility of such a dam, but George Goethals