A large part of the area to the east of Carrum had flooded in the 1930s and 1950s, but to the engineers investigating the land, the important issues were why this occurred and how it could be prevented from occurring again. A common misconception was that the area was all swamp and mud. Extensive drilling found that only a surface layer of peat-like material was unsuitable. Underneath this layer was fine dense sand. The engineers realised that once the unsuitable material was removed (and used to strengthen levee banks and create landscaped areas and reserves) they would then be able to excavate to form lakes and canals, and use the excavated sand in forming residential sites. By using this fine, dense, carefully compacted sand, all the proposed residential sites would be brought to a level above that required by the authorities.