The construction of the Deurganckdock lock is one of the largest building sites currently being worked on in Belgium. In order to draw up the design, a comprehensive testing program was conducted by the Geotechnics Division. Geotechnical design calculations were also made, with particular attention paid to the swell of the Boom clay. We are also closely involved with the execution of the project. Geotechnical follow up of activities on the site linked with an intensive monitoring program for the estimation of the swell of the Boom Clay, was a challenge.