The Netherlands' nearly two-mile long Eastern Scheldt storm surge barrier required the building of 66 reinforced concrete piers ranging from 100 to 130 feet high and measuring 82 by 165 feet at the base, with a design life of 200 years in a seawater environment. Each pier, weighing an average 17,000 tons, was built in a construction dry dock, then towed to its final position at sea, with precast sill beams and metal gates then installed in recesses built into the piers. To preserve the ecology, the barrier permits free flow of water during fair weather; but when storms occur, sliding steel gates between the piers will close and hold out the North Sea to prevent flooding.
The decision to construct complete pier units, including caissons, at a remote site protected from the weather was made to reduce construction risk and time delays due to weather and to eliminate substantial safety risks for workers. Piers were built in a construction dock which would be flooded once they were completed. The flooding provided buoyancy, reducing pier weight by about half for the lifting vessel. The dock was subdivided into four compartments so that flooding of one wouldn't interfere with work being done in others.
Special measures that limited cracking during the construction phase included artificial cooling of concrete, thermal insulation of the base slab, and early "shrinkage" prestressing. A part of the total prestressing was applied as soon as possible in each poured part of the structure. By tensioning some of the cables at an early stage, even before removal of formwork, the compressive stresses limited tensile stress build-up and lowered the risk of cracking. Various practices were also used to help control corrosion in the prestressing components. Tendon ducts were formed from smooth-walled 0.08-inch-thick sheet to provide more protection than does the normally used corrugated sheet metal. Anchorages of the prestressing tendons were finished with 3 layers of tar epoxy and the ends of strands had a plastic protection cap. Anchorage recesses were sandblasted, then filled with shotcrete.