In the 1970s, Belgium embarked on an ambitious expansion of the Port of Zeebrugge to accommodate a new generation of larger vessels and growing international trade volumes. As part of this development, the companies that would later form DEME played a key role in the construction of the new outer harbour, carrying out large-scale dredging, land reclamation and marine construction works.

The project arrived at a crucial time. As international dredging demand slowed following the oil crisis, Zeebrugge provided long-term continuity while presenting challenges that extended far beyond traditional dredging. Teams carried out ground improvement works, offshore geotechnical investigations and innovative coastal protection measures.

When the outer harbour officially opened in 1985, Zeebrugge had established itself as a major deep-water port. The project broadened expertise beyond dredging alone, combining marine civil engineering, ground improvement and offshore techniques that would help shape the company's future diverse activities.