New Inventions and Techniques
The first section of the Afsluitdijk was a 2.5 kilometre wide boulder clay dike, built in the Amsteldiep. This way, the island of Wieringen was connected to the mainland. A ringdike was built around the Wieringermeer, and the polder was pumped dry using the pumping-engines near Medemblik and Den Oever. By 1930, it was completely impoldered.
Meanwhile, in 1927, the construction of the Afsluitdijk began. Osier mats with dumpstones were used to fortify the two future closing breaches. After that, the dike was built up out of boulder clay, sand, and stones. In March 1931, construction workers suffered a large setback - divers discovered that the osier mats were riddled with woodworm: a worm or insect larva that bores into wood. Moreover, seawater had heavily corroded the galvanized steel wire that was holding the sink pieces together. To prevent the dam from washing away, the material had to be replaced as soon as possible. Barite, a mineral that had to be imported from Germany, was chosen as the new material. The barite was a success and the damn was saved.