Breaking Ground: The Foundation Challenge

The tower's foundation work began in winter's grip, with the Seine running high and the ground frozen solid. The challenge was immediately apparent: each of the tower's four legs needed a different foundation solution due to varying soil conditions.

The two piers closest to the Seine (the north and west pillars) sat on loose, water-bearing ground. Here, Eiffel employed compressed-air caissons—iron chambers where workers could excavate below the water table. The technology was dangerous; workers faced the risk of "caisson disease" (the bends) from pressure changes. Dr. François Triger, the company physician, instituted mandatory decompression periods and limited shift lengths, revolutionary safety measures for the time.

Pierre Michaud, a caisson worker, later described the experience: "It was like working in a iron coffin under the river. The air pressed on your ears until they ached. But Monsieur Eiffel paid us well and made sure we took breaks. In other jobs, men died every week. Here, we all went home to our families."

The south and east pillars, on firmer ground, required "only" massive excavations down to the hard clay layer. Even here, innovation was needed. Eiffel designed the foundations to distribute the tower's weight evenly—each of the four foundations would bear about 1.5 to 2 kilograms per square centimeter, less pressure than a person sitting in a chair.

By April 1887, all four foundations were complete. Each consisted of massive limestone blocks set in cement, with the ironwork anchor bolts precisely positioned. The slightest error in alignment would magnify as the tower rose. Koechlin's calculations allowed for a margin of error of just 1 millimeter per meter of height.