ABSTRACT
The Boom Clay formation is a marine sediment of tertiary, Rupelian age (30 My). At the Belgian MolDessel nuclear site, the Boom Clay lies 190-290 m below ground level. The Boom Clay layer is almost horizontal (it dips 1-2% towards the NE) and water bearing sand layers are situated above and below it. The underground water level is situated more or less at the ground surface. The total vertical stress and pore water pressure at the level of the Belgian Underground Research Laboratory are about 4.5 and 2.2 MPa respectively.
